{"id":389,"date":"2016-01-04T08:39:44","date_gmt":"2016-01-04T08:39:44","guid":{"rendered":"http:\/\/www.inforsec.org\/wp\/?p=389"},"modified":"2016-01-04T09:09:42","modified_gmt":"2016-01-04T09:09:42","slug":"389","status":"publish","type":"post","link":"http:\/\/202.112.238.40\/wp\/?p=389","title":{"rendered":"ELF\u5982\u4f55\u6467\u6bc1\u5723\u8bde \u2014\u2014\u901a\u8fc7ELF\u52a8\u6001\u88c5\u8f7d\u673a\u5236\u8fdb\u884c\u6f0f\u6d1e\u5229\u7528"},"content":{"rendered":"

\u4f5c\u8005\uff1aAlessandro Di Federico, Amat Cama, Yan Shoshitaishvili, Christopher Kruegel and Giovanni Vigna(UCSB,CA, USA; Politecnico di Milano, Milan, Italy)
\n<\/span>\u539f\u6587\u51fa\u81ea\uff1aUSENIX Security 2015<\/a>
\n\u7ffb\u8bd1\uff1a\u88f4\u4e2d\u715c\uff0c\u6e05\u534e\u5927\u5b66\u7f51\u7edc\u7814\u7a76\u9662\uff08\u672c\u6587\u662f\u6e05\u534e\u5927\u5b66\u672c\u79d1\u6bd5\u8bbe\u8981\u6c42\u7ffb\u8bd1\u7684\u5916\u6587\u6587\u732e\uff09\u5168\u90e8\u8bd1\u6587<\/a><\/span><\/span>
\n========================================================================
\n<\/span>\u6458\u8981<\/strong><\/p>\n

\u8fd1\u51e0\u5341\u5e74\u6765\uff0c\u8ba1\u7b97\u673a\u8f6f\u4ef6\u7ecf\u5386\u7740\u4e00\u573a\u5229\u7528\u6280\u672f\u3001\u53d1\u73b0\u4e0e\u4fdd\u62a4\u6280\u672f\u4e4b\u95f4\u7684\u519b\u5907\u7ade\u8d5b\u3002\u4e00\u4e9b\u6709\u6548\u7684\u4fdd\u62a4\u63aa\u65bd\uff08\u4f8b\u5982\uff0cASLR\u5730\u5740\u7a7a\u95f4\u5e03\u5c40\u968f\u673a\u5316\uff09\uff0c\u663e\u8457\u5730\u589e\u52a0\u4e86\u6210\u529f\u5229\u7528\u4e00\u4e2a\u6f0f\u6d1e\u7684\u96be\u5ea6\u3002\u4e00\u4e2a\u73b0\u4ee3\u7684\u6f0f\u6d1e\u5229\u7528\u4e00\u822c\u5206\u4e3a\u4e24\u4e2a\u9636\u6bb5\uff1a\u7b2c\u4e00\u6b65\u9700\u8981\u8fdb\u884c\u4fe1\u606f\u6cc4\u6f0f\u4ee5\u53d6\u5f97\u7a0b\u5e8f\u7684\u5185\u5b58\u5206\u5e03\uff0c\u63a5\u7740\u7b2c\u4e8c\u6b65\u5219\u8fdb\u884c\u5b9e\u9645\u7684\u5229\u7528\u3002\u7136\u800c\uff0c\u7531\u4e8e\u5185\u5b58\u7834\u574f\u540e\u7684\u5177\u4f53\u60c5\u51b5\u5404\u4e0d\u76f8\u540c\uff0c\u4ece\u7a0b\u5e8f\u4e2d\u5f97\u5230\u5185\u5b58\u5e03\u5c40\u7684\u65b9\u6cd5\u5e76\u4e0d\u603b\u662f\u53ef\u884c\u3002<\/span><\/p>\n

\u5728\u8fd9\u7bc7\u6587\u7ae0\u4e2d\uff0c\u6211\u4eec\u5c55\u793a\u4e86\u4e00\u79cd\u4e0d\u9700\u8981\u8fdb\u884c\u4fe1\u606f\u6cc4\u6f0f\uff0c\u800c\u662f\u4f7f\u7528\u52a8\u6001\u88c5\u8f7d\u5668\u6765\u76f4\u63a5\u6807\u8bc6\u5173\u952e(critical)\u51fd\u6570\u7684\u4f4d\u7f6e\u5e76\u8c03\u7528\u5b83\u4eec\u7684\u6280\u672f\u3002\u6211\u4eec\u5728ELF\u6587\u4ef6\u6807\u51c6\u548c\u52a8\u6001\u88c5\u8f7d\u5668\u7684\u5b9e\u73b0\u4e2d\u627e\u5230\u4e86\u51e0\u4e2a\u5f31\u70b9\uff0c\u8fd9\u4e9b\u5f31\u70b9\u80fd\u591f\u7528\u6765\u89e3\u6790\u3001\u6267\u884c\u4efb\u610f\u5e93\u51fd\u6570\u3002\u56e0\u6b64\uff0c\u6211\u4eec\u80fd\u591f\u7ed5\u8fc7\u7279\u5b9a\u7684\u5b89\u5168\u7f13\u89e3\u63aa\u65bd\uff0c\u5305\u62ec\u4e13\u95e8\u4e3a\u4fdd\u62a4ELF\u6570\u636e\u7ed3\u6784\u4e0d\u88ab\u653b\u51fb\u8005\u7834\u574f\u800c\u8bbe\u8ba1\u7684partial RELRO\u4e0efull RELRO\u3002\u6211\u4eec\u5b9e\u73b0\u4e86\u4e00\u4e2a\u540d\u4e3aLeakless\u7684\u539f\u578b\u5de5\u5177\uff0c\u5e76\u9488\u5bf9\u52a8\u6001\u88c5\u8f7d\u5668\u7684\u5b9e\u73b0\u3001\u4e4b\u524d\u7684\u653b\u51fb\u6280\u672f\u548c\u771f\u5b9e\u6848\u4f8b\u8fdb\u884c\u8bc4\u4f30\u4ee5\u786e\u5b9a\u6211\u4eec\u7684\u53d1\u73b0\u7684\u5f71\u54cd\u3002\u53e6\u5916\uff0cLeakless\u4e5f\u53ef\u4ee5\u8fdb\u884c\u66f4\u53ef\u9760\u3001\u66f4\u4e0d\u5177\u4fb5\u7565\u6027\u7684\u653b\u51fb\uff0c\u4ee5\u51cf\u5c11\u88ab\u5165\u4fb5\u68c0\u6d4b\u7cfb\u7edf\u53d1\u73b0\u7684\u51e0\u7387\u3002<\/span><\/p>\n

========================================================================<\/span><\/p>\n

    \n
  1. \u7b80\u4ecb<\/strong><\/li>\n<\/ol>\n

    \u4ece1998\u5e74Morris worm\u53d1\u8868\u7684\u7b2c\u4e00\u4e2a\u88ab\u5e7f\u6cdb\u5e94\u7528\u7684\u6808\u6ea2\u51fa\u6587\u7ae0[27]\u4ee5\u6765\uff0c\u5185\u5b58\u7834\u574f\u6f0f\u6d1e\u7684\u4fdd\u62a4\u3001\u5229\u7528\u548c\u51cf\u7f13\u6280\u672f\u7814\u7a76\u5360\u636e\u7740\u5b89\u5168\u7814\u7a76\u4eba\u5458\u548c\u7f51\u7edc\u7f6a\u72af\u76f8\u540c\u7684\u65f6\u95f4\u3002\u5c3d\u7ba1\u8fd1\u5e74\u6765\u5185\u5b58\u7834\u574f\u6f0f\u6d1e\u7684\u76db\u884c\u8d8b\u52bf\u6709\u6240\u51cf\u7f13\uff0c\u7ecf\u5178\u7684\u6808\u6ea2\u51fa\u4ecd\u7136\u96c4\u8e1e\u6700\u5e38\u89c1\u8f6f\u4ef6\u6f0f\u6d1e\u7684\u7b2c3\u4f4d\uff0c\u800c\u53e6\u59164\u79cd\u5185\u5b58\u7834\u574f\u6f0f\u6d1e\u5df2\u7ecf\u8dcc\u51fa\u4e86\u524d25\u540d\u3002<\/span><\/p>\n

    \u800c\u80fd\u591f\u5239\u4f4f\u5185\u5b58\u7834\u574f\u4e4b\u98ce\u7684\u539f\u56e0\uff0c\u662f\u5728\u5185\u5b58\u4fdd\u62a4\u4e0e\u7f13\u89e3\u63aa\u65bd\u65b9\u9762\u7684\u5de8\u5927\u6295\u5165\u3002\u8fd9\u4e9b\u7f13\u89e3\u63aa\u65bd\u4e3b\u8981\u5e94\u7528\u4e8e2\u4e2a\u65b9\u9762\uff1a\u7cfb\u7edf\u7ea7\u52a0\u56fa(\u4f8b\u5982CGroups [23], Apparmor [4], Capsicum [41], \u548c GRSecurity [18]) \u548c\u5e94\u7528\u7ea7\u52a0\u56fa(\u5982 stack canaries [3], Address Space Layout Randomization (ASLR), \u548c No-eXecute (NX) bit [8]).<\/span><\/p>\n

    \u5c24\u5176\u662f\u5730\u5740\u7a7a\u95f4\u5e03\u5c40\u968f\u673a\u5316(ASLR)\uff0c\u901a\u8fc7\u5c06\u52a8\u6001\u5e93\u52a0\u8f7d\u5230\u5185\u5b58\u4e2d\u968f\u673a\u7684\u4e00\u5757\u533a\u57df\uff08\u5bf9\u4e8e\u653b\u51fb\u8005\u6765\u8bf4\u672a\u77e5\uff09\uff0c\u4f7f\u5f97\u653b\u51fb\u8005\u9700\u8981\u5c06\u5229\u7528\u8fc7\u7a0b\u62c6\u5206\u4e3a2\u4e2a\u9636\u6bb5\u3002\u5728\u7b2c\u4e00\u4e2a\u9636\u6bb5\uff0c\u653b\u51fb\u8005\u5fc5\u987b\u4f7f\u7528\u4e00\u4e2a\u4fe1\u606f\u6cc4\u6f0f\u6f0f\u6d1e\u5c06\u7a0b\u5e8f\u4ee5\u53ca\u52a8\u6001\u5e93\u7684\u5185\u5b58\u5e03\u5c40\u6cc4\u6f0f\u51fa\u6765\uff0c\u8fd9\u6837\u5c31\u53ef\u4ee5\u6807\u8bc6\u51fa\u5b89\u5168\u5173\u952e(security-critical)\u51fd\u6570\uff08\u4f8b\u5982system()\u5e93\u51fd\u6570\uff09\u4ee3\u7801\u7684\u5730\u5740\u3002\u5728\u7b2c\u4e8c\u4e2a\u9636\u6bb5\uff0c\u653b\u51fb\u8005\u4f7f\u7528\u4e00\u4e2a\u63a7\u5236\u6d41\u91cd\u5b9a\u5411\u6f0f\u6d1e\uff0c\u5c06\u7a0b\u5e8f\u7684\u63a7\u5236\u6d41\u91cd\u5b9a\u5411\u5230\u8fd9\u4e2a\u51fd\u6570\u3002<\/p>\n

    \u7136\u800c\uff0c\u7531\u4e8e\u5185\u5b58\u7834\u574f\u540e\u7684\u5177\u4f53\u60c5\u51b5\u5404\u4e0d\u76f8\u540c\uff0c\u4ece\u7a0b\u5e8f\u4e2d\u5f97\u5230\u5185\u5b58\u5e03\u5c40\u4fe1\u606f\u7684\u65b9\u6cd5\u5e76\u4e0d\u603b\u662f\u53ef\u884c\u3002\u4f8b\u5982\uff0c\u5927\u591a\u6570\u89e3\u6790\u4ee3\u7801\uff08\u4f8b\u5982\u89e3\u7801\u56fe\u50cf\u6216\u8005\u89c6\u9891\uff09\u7ecf\u5e38\u4e0d\u4f1a\u4e0e\u653b\u51fb\u8005\u6709\u76f4\u63a5\u7684\u4ea4\u4e92\uff0c\u8fd9\u5c31\u6392\u9664\u4e86\u4fe1\u606f\u6cc4\u6f0f\u7684\u53ef\u80fd\u6027\u3002\u6ca1\u6709\u8fd9\u4e9b\u4fe1\u606f\uff0c\u518d\u5bf9ASLR\u4fdd\u62a4\u4e0b\u7684\u4e8c\u8fdb\u5236\u6587\u4ef6\u4f7f\u7528\u73b0\u5728\u7684\u6280\u672f\u8fdb\u884c\u5229\u7528\u901a\u5e38\u662f\u4e0d\u53ef\u884c\u6216\u4e0d\u53ef\u9760\u7684\u3002<\/span><\/p>\n

    \u5c31\u50cf [36] \u4e2d\u5199\u7684\u90a3\u6837\uff0c\u9664\u4e86\u52a0\u56fa\u5e94\u7528\u548c\u7cfb\u7edf\u7684\u7ade\u8d5b\uff0c\u5bf9\u4e8e\u4e8c\u8fdb\u5236\u7684\u683c\u5f0f\u4ee5\u53ca\u7cfb\u7edf\u7ec4\u4ef6\u7684\u4e00\u4e9b\u9c9c\u4e3a\u4eba\u77e5\u7684\u89d2\u843d\uff0c\u5219\u7f3a\u5c11\u4ed4\u7ec6\u7684\u68c0\u67e5\u3002\u7279\u522b\u5730\uff0c\u6211\u4eec\u7740\u773c\u4e8e\u64cd\u4f5c\u7cfb\u7edf\u4e2d\u7684\u4e00\u4e2a\u7528\u6237\u6001\u7ec4\u4ef6\u2014\u2014\u52a8\u6001\u88c5\u8f7d\u5668\uff0c\u8d1f\u8d23\u88c5\u8f7d\u4e8c\u8fdb\u5236\u6587\u4ef6\u4ee5\u53ca\u5b83\u4eec\u4f9d\u8d56\u7684\u5e93\u6587\u4ef6\u5230\u5185\u5b58\u4e2d\u3002\u4e8c\u8fdb\u5236\u6587\u4ef6\u4f7f\u7528\u52a8\u6001\u88c5\u8f7d\u5668\u6765\u652f\u6301\u5bfc\u5165\u7b26\u53f7\u7684\u89e3\u6790\u529f\u80fd\u3002\u6709\u8da3\u7684\u662f\uff0c\u8fd9\u6070\u597d\u5c31\u662f\u4e00\u4e2a\u9762\u5bf9\u52a0\u56fa\u5e94\u7528\u7684\u653b\u51fb\u8005\u901a\u8fc7\u6cc4\u6f0f\u5e93\u5730\u5740\u4e0e\u5185\u5bb9\u5c1d\u8bd5\u201c\u91cd\u5851\u201d\u4e00\u4e2a\u7b26\u53f7\u7684\u8868\u73b0\u3002<\/span><\/p>\n

    \u6211\u4eec\u7684\u6280\u672f\u7684\u4eae\u70b9\uff0c\u5728\u4e8e\u53ef\u4ee5\u901a\u8fc7\u6d3b\u7528\u4e00\u4e2a\u52a8\u6001\u88c5\u8f7d\u5668\u7684\u529f\u80fd\uff0c\u5b8c\u5168\u7701\u53bb\u5bf9\u4fe1\u606f\u6cc4\u6f0f\u6f0f\u6d1e\u7684\u9700\u8981\u3002\u6211\u4eec\u7684\u6280\u672f\u5229\u7528\u52a8\u6001\u88c5\u8f7d\u5668\u4e0eELF\u683c\u5f0f\u7684\u5f31\u70b9\uff0c\u89e3\u6790\u5e76\u6267\u884c\u4efb\u610f\u5e93\u51fd\u6570\uff0c\u5141\u8bb8\u6211\u4eec\u5728\u6ca1\u6709\u4fe1\u606f\u6cc4\u6f0f\u7684\u60c5\u51b5\u4e0b\u6210\u529f\u5730\u653b\u51fb\u52a0\u56fa\u540e\u7684\u5e94\u7528\u3002\u4efb\u4f55\u5e93\u51fd\u6570\u90fd\u53ef\u4ee5\u88ab\u6267\u884c\uff0c\u53ea\u8981\u5b83\u6240\u5728\u5e93\u88ab\u52a0\u8f7d\u8fdb\u7a0b\u5e8f\u3002\u65e2\u7136\u6240\u6709\u7684\u4e8c\u8fdb\u5236\u7a0b\u5e8f\u90fd\u4f9d\u8d56\u4e8eC\u8bed\u8a00\u5e93\uff0c\u8fd9\u5c31\u8868\u793a\u6211\u4eec\u7684\u6280\u672f\u80fd\u6267\u884csystem()\u548cexecve()\u8fd9\u7c7b\u5b89\u5168\u5173\u952e(security-critical)\u51fd\u6570\uff0c\u4ece\u800c\u5141\u8bb8\u6267\u884c\u4efb\u610f\u547d\u4ee4\u3002\u6211\u4eec\u8fd8\u4f1a\u5c55\u793a\u4e00\u4e9b\u901a\u8fc7\u91cd\u7528\u7279\u5b9a\u5e94\u7528\u7a0b\u5e8f\u5e93\u4e2d\u7684\u51fd\u6570\u6765\u8fdb\u884c\u590d\u6742\u53c8\u9690\u79d8\u7684\u653b\u51fb\u3002\u8fd9\u9879\u6280\u672f\u975e\u5e38\u53ef\u9760\u4e14\u67b6\u6784\u65e0\u5173\uff0c\u653b\u51fb\u8005\u4e0d\u9700\u8981\u77e5\u9053\u7248\u672c\u3001\u5e03\u5c40\u3001\u5185\u5bb9\u6216\u8005\u5176\u4ed6\u5173\u4e8e\u5e93\u51fd\u6570\u4e0d\u53ef\u77e5\u7684\u4fe1\u606f\u3002<\/span><\/p>\n

    \u6211\u4eec\u5b9e\u73b0\u4e86\u81ea\u5df1\u7684\u60f3\u6cd5\uff0c\u5199\u6210\u4e86\u4e00\u4e2a\u79f0\u4e3aLeakless\u7684\u539f\u578b\u5de5\u5177\u3002\u8981\u4f7f\u7528Leakless\uff0c\u653b\u51fb\u8005\u5fc5\u987b\u62e5\u6709\u76ee\u6807\u5e94\u7528\u7684\u526f\u672c\uff0c\u4e14\u80fd\u591f\u5229\u7528\u6f0f\u6d1e\uff08\u5373\u52ab\u6301\u63a7\u5236\u6d41\uff09\u3002\u4e4b\u540e\uff0cLeakless\u53ef\u4ee5\u5728\u6ca1\u6709\u4fe1\u606f\u6cc4\u6f0f\u7684\u60c5\u51b5\u4e0b\u81ea\u52a8\u5730\u521b\u5efa\u5229\u7528\u8fc7\u7a0b\uff0c\u5e76\u4e14\u8c03\u7528\u653b\u51fb\u8005\u611f\u5174\u8da3\u7684\u5173\u952e\u5e93\u51fd\u6570\u3002<\/span><\/p>\n

    \u4e3a\u4e86\u8bc4\u4f30\u6211\u4eec\u6280\u672f\u7684\u5f71\u54cd\uff0c\u6211\u4eec\u5bf9\u51e0\u4e2a\u4e0d\u540c\u7684Linux(\u4ee5\u53caFreeBSD)\u53d1\u884c\u7248\u8fdb\u884c\u4e86\u8c03\u7814\uff0c\u53d1\u73b0\u5176\u4e2d\u5927\u90e8\u5206\u7684\u4e8c\u8fdb\u5236\u7a0b\u5e8f\u5bb9\u6613\u88abLeakless\u7684\u653b\u51fb\u6240\u5f71\u54cd\uff08\u5982\u679c\u76ee\u6807\u7a0b\u5e8f\u6709\u5185\u5b58\u7834\u574f\u6f0f\u6d1e\u7684\u8bdd\uff09\u3002\u6211\u4eec\u8fd8\u5ba1\u67e5\u4e86\u591a\u79cdC\u8bed\u8a00\u5e93\u7684\u52a8\u6001\u88c5\u8f7d\u5668\u5b9e\u73b0\uff0c\u53d1\u73b0\u5176\u4e2d\u5927\u591a\u6570\u4e5f\u662f\u5bb9\u6613\u88abLeakless\u7684\u6280\u672f\u5f71\u54cd\u7684\u3002\u9664\u6b64\u4e4b\u5916\uff0c\u6211\u4eec\u5c55\u793a\u4e86\u4e00\u79cd\u6d41\u884c\u7684\u7f13\u89e3\u6280\u672f\uff0cRELocation Read-Only (RELRO) \u91cd\u5b9a\u4f4d\u53ea\u8bfb\uff0c\u5b83\u80fd\u591f\u4fdd\u62a4\u5e93\u51fd\u6570\u7684\u8c03\u7528\u4e0d\u53d7\u653b\u51fb\u8005\u91cd\u5b9a\u5411\u7684\u5f71\u54cd\u3002\u7136\u800c\u5b83\u4e5f\u88abLeakless\u5b8c\u5168\u5730\u7ed5\u8fc7\u4e86\u3002\u6700\u540e\uff0c\u6211\u4eec\u6bd4\u8f83\u4e86Leakless\u4e0e\u7c7b\u4f3c\u7684ROP\u7f16\u8bd1\u5668\u4ea7\u751f\u7684ROP\u94fe\u7684\u957f\u5ea6\u3002Leakless\u4ea7\u751f\u7684ROP\u94fe\u7684\u957f\u5ea6\u663e\u8457\u5730\u77ed\u4e8e\u73b0\u6709\u6280\u672f\u4ea7\u751f\u7684ROP\u94fe\u3002\u5c31\u50cf\u6211\u4eec\u5c55\u793a\u7684\u90a3\u6837\uff0c\u4e0e\u4f20\u7edfROP\u7f16\u8bd1\u5668\u76f8\u6bd4Leakless\u80fd\u591f\u5b9e\u73b0\u66f4\u52a0\u5e7f\u6cdb\u7684\u5229\u7528\u3002<\/span><\/p>\n

    \u603b\u7684\u6765\u8bf4\uff0c\u6211\u4eec\u4f5c\u51fa\u4e86\u5982\u4e0b\u8d21\u732e\uff1a<\/p>\n

    – \u6211\u4eec\u5f00\u53d1\u4e86\u4e00\u4e2a\u65b0\u7684\u3001\u67b6\u6784\u4e0e\u5e73\u53f0\u65e0\u5173\u7684\u653b\u51fb\uff0c\u4f7f\u7528\u57fa\u4e8eELF\u3001\u652f\u6301\u52a8\u6001\u88c5\u8f7d\u7684\u7cfb\u7edf\u7684\u56fa\u6709\u529f\u80fd\uff0c\u4f7f\u5f97\u653b\u51fb\u8005\u80fd\u591f\u5728\u4e0d\u505a\u4fe1\u606f\u6cc4\u6f0f\u7684\u60c5\u51b5\u4e0b\uff0c\u6267\u884c\u4efb\u610f\u5e93\u51fd\u6570\u3002<\/span><\/p>\n

    – \u6211\u4eec\u8be6\u8ff0\u4e86\u5b9e\u73b0\u81ea\u5df1\u7684\u7cfb\u7edf\u7684\u8fc7\u7a0b\u4e2d\uff0c\u9762\u5bf9\u4e0d\u540c\u52a8\u6001\u88c5\u8f7d\u5668\u5b9e\u73b0\u548c\u591a\u79cd\u7f13\u89e3\u63aa\u65bd(\u5305\u62ecRELRO)\u7684\u6311\u6218\uff0c\u5e76\u6700\u7ec8\u514b\u670d\u4e86\u5b83\u4eec\u3002<\/span><\/p>\n

    – \u6700\u540e\uff0c\u6211\u4eec\u8fdb\u884c\u4e86\u4e00\u6b21\u6df1\u5165\u7684\u8bc4\u4f30\uff0c\u5305\u62ec\u4ee5\u524d\u590d\u6742\u7684\u5229\u7528\u56e0\u4f7f\u7528\u4e86\u6211\u4eec\u7684\u6280\u672f\u53d8\u5f97\u5bb9\u6613\u7684\u6848\u4f8b\u5206\u6790\uff0c\u5bf9\u51e0\u79cd\u4e0d\u540c\u52a8\u6001\u88c5\u8f7d\u5668\u5b9e\u73b0\u5b89\u5168\u6027\u7684\u8bc4\u5b9a\uff0c\u6211\u4eec\u7684\u6280\u672f\u5728\u4e0d\u540c\u64cd\u4f5c\u7cfb\u7edf\u914d\u7f6e\u4e0b\u9002\u7528\u6027\u7684\u8c03\u7814\uff0c\u4ee5\u53caLeakless\u5728ROP\u94fe\u957f\u5ea6\u6539\u5584\u65b9\u9762\u7684\u6d4b\u91cf\u3002<\/span><\/p>\n

    ========================================================================<\/span><\/p>\n

      \n
    1. \u76f8\u5173\u5de5\u4f5c\uff1a\u5185\u5b58\u7834\u574f\u7684\u519b\u5907\u7ade\u8d5b<\/strong><\/li>\n<\/ol>\n

      \u5185\u5b58\u7834\u574f\u7684\u519b\u5907\u7ade\u8d5b(\u5373\u9632\u5fa1\u8005\u9488\u5bf9\u73b0\u6709\u7684\u5229\u7528\u6280\u672f\u5f00\u53d1\u5bf9\u6297\u63aa\u65bd\uff0c\u63a5\u7740\u653b\u51fb\u8005\u60f3\u51fa\u65b0\u7684\u5229\u7528\u6280\u672f\u6765\u7ed5\u8fc7\u8fd9\u4e9b\u63aa\u65bd\u7684\u8fc7\u7a0b)\u5df2\u7ecf\u6301\u7eed\u4e86\u51e0\u5341\u5e74\u3002\u8fd9\u573a\u7ade\u8d5b\u7684\u5386\u53f2\u5df2\u7ecf\u88ab\u8bb0\u5f55\u5728\u522b\u5904 [37]\uff0c\u8fd9\u4e00\u8282\u7740\u773c\u4e8e\u90a3\u4e9b\u4f7f\u5f97\u73b0\u4ee3\u5229\u7528\u6280\u672f\u88ab\u62c6\u5206\u62102\u4e2a\u9636\u6bb5\u7684\u4e8b\u4ef6\uff0c\u5c31\u662f\u8bf4\uff0c\u9700\u8981\u653b\u51fb\u8005\u5728\u6267\u884c\u4efb\u610f\u4ee3\u7801\u524d\u8fdb\u884c\u4fe1\u606f\u6cc4\u6f0f\u8fd9\u4e00\u6b65\u3002<\/p>\n

      \u65e9\u671f\u7684\u6808\u6ea2\u51fa\u5229\u7528\u4f9d\u8d56\u4e8e\u5411\u7f13\u51b2\u533a\u4e2d\u6ce8\u5165\u4e8c\u8fdb\u5236\u4ee3\u7801(\u79f0\u4e3ashellcode)\u7684\u80fd\u529b\uff0c\u5e76\u9700\u8981\u8986\u76d6\u5728\u6808\u4e0a\u7684\u4e00\u4e2a\u8fd4\u56de\u5730\u5740\u4f7f\u5176\u6307\u5411\u8fd9\u4e2a\u7f13\u51b2\u533a\u3002\u968f\u540e\uff0c\u5f53\u7a0b\u5e8f\u4ece\u5f53\u524d\u51fd\u6570\u8fd4\u56de\u65f6\uff0c\u6267\u884c\u6d41\u5c31\u4f1a\u88ab\u91cd\u5b9a\u5411\u5230\u653b\u51fb\u8005\u7684shellcode\uff0c\u63a5\u7740\u653b\u51fb\u8005\u5c31\u80fd\u53d6\u5f97\u7a0b\u5e8f\u7684\u63a7\u5236\u6743\u3002<\/span><\/p>\n

      \u7ed3\u679c\uff0c\u5b89\u5168\u7814\u7a76\u8005\u63d0\u51fa\u4e86\u53e6\u4e00\u9879\u51cf\u7f13\u6280\u672f\uff1a\u4e0d\u53ef\u6267\u884c\u4f4d(the NX bit)\u3002\u4e0d\u53ef\u6267\u884c\u4f4d\u5177\u6709\u9632\u6b62\u90a3\u4e9b\u4e0d\u8be5\u6709\u4ee3\u7801\u7684\u533a\u57df(\u6808\u5c31\u662f\u5178\u578b\u7684\u8fd9\u7c7b\u533a\u57df)\u88ab\u6267\u884c\u7684\u6548\u679c\u3002<\/span><\/p>\n

      \u4e0d\u53ef\u6267\u884c\u4f4d\u903c\u8feb\u653b\u51fb\u8005\u4eec\u5f00\u59cb\u91c7\u7528\u201c\u4ee3\u7801\u91cd\u7528\u201d\u7684\u7406\u5ff5\uff1a\u4f7f\u7528\u7a0b\u5e8f\u4e2d\u5df2\u7ecf\u5b58\u5728\u7684\u4ee3\u7801(\u4f8b\u5982\u7cfb\u7edf\u8c03\u7528\u6216\u5b89\u5168\u5173\u952e(security-critical)\u5e93\u51fd\u6570)\u6765\u8fbe\u5230\u4ed6\u4eec\u7684\u76ee\u7684\u3002\u5728return-to-libc\u7684\u5229\u7528\u4e2d [30,39] \uff0c\u4e00\u4e2a\u653b\u51fb\u8005\u5c06\u63a7\u5236\u6d41\u91cd\u5b9a\u5411\u5230\u4e00\u4e2a\u654f\u611f\u7684libc\u51fd\u6570(\u4f8b\u5982system())\uff0c\u5e76\u7ed9\u4e88\u5176\u6070\u5f53\u7684\u53c2\u6570\u6765\u5b9e\u884c\u6076\u610f\u7684\u884c\u4e3a\uff0c\u800c\u4e0d\u662f\u6ce8\u5165shellcode\u3002<\/span><\/p>\n

      \u4e3a\u4e86\u5bf9\u6297\u8fd9\u9879\u6280\u672f\uff0c\u4e00\u9879\u7cfb\u7edf\u7ea7\u7684\u52a0\u56fa\u63aa\u65bd\uff0c\u79f0\u4e3a\u5730\u5740\u7a7a\u95f4\u5e03\u5c40\u968f\u673a\u5316ASLR\u88ab\u5f00\u53d1\u51fa\u6765\u3002\u4e00\u65e6ASLR\u8d77\u4f5c\u7528\uff0c\u653b\u51fb\u8005\u5c06\u65e0\u6cd5\u77e5\u9053\u5e93\u7684\u4f4d\u7f6e\u3002\u5b9e\u9645\u4e0a\uff0c\u7a0b\u5e8f\u7684\u5185\u5b58\u5e03\u5c40(\u5e93\u88ab\u52a0\u8f7d\u7684\u4f4d\u7f6e\uff0c\u6808\u7684\u4f4d\u7f6e\u4ee5\u53ca\u5806\u7684\u4f4d\u7f6e)\u6bcf\u6b21\u6267\u884c\u90fd\u662f\u968f\u673a\u7684\u3002\u56e0\u6b64\uff0c\u653b\u51fb\u8005\u4e0d\u77e5\u9053\u5c06\u63a7\u5236\u6d41\u91cd\u5b9a\u5411\u5230\u54ea\u91cc\u624d\u80fd\u6267\u884c\u7279\u5b9a\u51fd\u6570\u3002\u66f4\u7cdf\u7cd5\u7684\u662f\uff0c\u5373\u4f7f\u662f\u653b\u51fb\u8005\u80fd\u591f\u786e\u5b9a\u8fd9\u4e9b\u4fe1\u606f\uff0c\u4ed6\u4ecd\u7136\u4e0d\u77e5\u9053\u7279\u5b9a\u51fd\u6570\u5728\u5e93\u4e2d\u7684\u4f4d\u7f6e\uff0c\u9664\u975e\u4ed6\u53d6\u5f97\u5e93\u6587\u4ef6\u7684\u4e00\u4efd\u526f\u672c\u3002\u7ed3\u679c\uff0c\u653b\u51fb\u8005\u5e38\u5e38\u9700\u8981\u6cc4\u6f0f\u5e93\u672c\u8eab\u7684\u5185\u5bb9\u5e76\u89e3\u6790\u4ee3\u7801\u6765\u786e\u5b9a\u5173\u952e\u51fd\u6570\u7684\u4f4d\u7f6e\u3002\u4e3a\u4e86\u6cc4\u6f0f\u5e93\uff0c\u653b\u51fb\u8005\u9700\u8981\u91cd\u7528\u4e00\u4e9b\u7a0b\u5e8f\u4ee3\u7801\u6bb5\u91cc\u7684\u5c0f\u5757\u4ee3\u7801(\u79f0\u4e3agadgets)\u6765\u6cc4\u6f0f\u5185\u5b58\u4f4d\u7f6e\u3002\u8fd9\u4e9bgadgets\u53ef\u4ee5\u901a\u8fc7\u5c06\u5176\u5730\u5740\u5199\u5728\u6808\u4e0a\u5e76\u8fde\u7eed\u5730\u6267\u884c\u8fd4\u56de(ret)\u6307\u4ee4\u88ab\u7ec4\u5408\u4f7f\u7528\u3002\u6240\u4ee5\uff0c\u8fd9\u9879\u6280\u672f\u88ab\u79f0\u4f5c\u201c\u9762\u5411\u8fd4\u56de\u7f16\u7a0b\u201d(Return Oriented Programming (ROP)).<\/p>\n

      ROP\u662f\u653b\u51fb\u8005\u7684\u4e00\u4e2a\u5f3a\u6709\u529b\u7684\u5de5\u5177\u3002\u5b9e\u9645\u4e0a\uff0c\u5728\u8bb8\u591a\u4e8c\u8fdb\u5236\u7a0b\u5e8f\u4e2d\u53d1\u73b0\u7684ROP Gadgets\u662f\u201c\u56fe\u7075\u5b8c\u5168\u201d\u96c6\u5408\uff0c\u501f\u52a9ROP\u7f16\u8bd1\u5668\u80fd\u591f\u5b8c\u6210\u5229\u7528\u7684\u4efb\u52a1\u3002\u7136\u800c\uff0c\u7531\u4e8e\u5176\u666e\u9002\u6027\u7684\u9700\u8981\uff0cROP\u7f16\u8bd1\u5668\u503e\u5411\u4e8e\u751f\u6210\u4f9d\u8d56\u4e8e\u5177\u4f53\u6f0f\u6d1e\u7ec6\u8282\u7684\u957fROP\u94fe\uff0c\u5b83\u4eec\u201c\u592a\u957f\u800c\u65e0\u7528\u201d [22].\u5728\u8fd9\u4e4b\u540e\uff0c\u6211\u4eec\u5c06\u5c55\u793aLeakless\u751f\u6210\u7684\u76f8\u5bf9\u77ed\u7684ROP\u94fe\uff0c\u5e76\u4e14\u4f9d\u8d56\u4e8e\u5b58\u5728\u7684\u7f13\u89e3\u63aa\u65bd\uff0c\u53ea\u9700\u8981\u5f88\u5c11\u7684gadgets\u3002\u6b64\u5916\uff0cLeakless\u5728\u6ca1\u6709\u56fe\u7075\u5b8c\u5168\u7684Gadgets\u7684\u96c6\u5408\u7684\u60c5\u51b5\u4e0b\u4e5f\u80fd\u53d1\u6325\u4f5c\u7528\u3002<\/span><\/p>\n

      \u5728\u771f\u5b9e\u4e16\u754c\u7684\u5229\u7528\u4e2d\uff0c\u653b\u51fb\u8005\u5f80\u5f80\u4f7f\u7528\u4e00\u4e2a\u4fe1\u606f\u6cc4\u6f0f\u653b\u51fb\u6765\u6cc4\u9732\u5e93\u7684\u5730\u5740\u6216\u5185\u5bb9\uff0c\u7136\u540e\u4f7f\u7528\u8fd9\u4e9b\u4fe1\u606f\u6765\u8ba1\u7b97\u5b89\u5168\u5173\u952e(security-critical)\u51fd\u6570(\u4f8b\u5982system())\u7684\u5730\u5740\uff0c\u6700\u540e\u53d1\u9001\u7b2c\u4e8c\u6bb5\u653b\u51fb\u8f7d\u8377(payload)\u5230\u6f0f\u6d1e\u5e94\u7528\u6765\u91cd\u5b9a\u5411\u63a7\u5236\u6d41\u5230\u60f3\u8981\u7684\u51fd\u6570\u3002<\/span><\/p>\n

      \u5b9e\u9645\u4e0a\uff0c\u6211\u4eec\u89c2\u5bdf\u5230\u5bfb\u627e\u7279\u5b9a\u5e93\u51fd\u6570\u7684\u76ee\u6807\u5df2\u7ecf\u88ab\u52a8\u6001\u88c5\u8f7d\u5668\u5b9e\u73b0\u4e86\uff0c\u8fd9\u662f\u4e00\u4e2a\u80fd\u591f\u8fdb\u884c\u7b26\u53f7\u89e3\u6790(\u5373\u786e\u5b9a\u5e93\u51fd\u6570\u5730\u5740)\u7684\u64cd\u4f5c\u7cfb\u7edf\u7ec4\u4ef6\u3002\u6240\u4ee5\uff0c\u6211\u4eec\u610f\u8bc6\u5230\u53ef\u4ee5\u4f7f\u7528\u52a8\u6001\u88c5\u8f7d\u5668\u6765\u7565\u8fc7\u4fe1\u606f\u6cc4\u6f0f\u8fd9\u4e00\u6b65\u5e76\u5de7\u5999\u5730\u8fdb\u884c\u5229\u7528\u3002\u56e0\u4e3a\u6211\u4eec\u7684\u653b\u51fb\u4e0d\u9700\u8981\u4fe1\u606f\u6cc4\u6f0f\u7684\u6b65\u9aa4\uff0c\u6240\u4ee5\u6211\u4eec\u79f0\u5b83\u4e3aLeakless.<\/span><\/p>\n

      \u4f7f\u7528\u52a8\u6001\u8fde\u63a5\u5668\u7684\u89c2\u5ff5\u5df2\u7ecf\u5728\u4e00\u4e9breturn-to-libc\u7684\u653b\u51fb\u4e2d\u4f5c\u4e3a\u5229\u7528\u8fc7\u7a0b\u7684\u4e00\u90e8\u5206\u88ab\u7b80\u8981\u5730\u63a2\u7a76\u8fc7 [15,21,30] \u3002\u7136\u800c\uff0c\u73b0\u6709\u7684\u6280\u672f\u975e\u5e38\u4f9d\u8d56\u73b0\u6709\u72b6\u51b5\uff0c\u4f9d\u8d56\u5e73\u53f0\uff0c\u9700\u89812\u4e2a\u9636\u6bb5\uff0c\u6216\u8005\u6613\u53d7\u5230\u73b0\u6709\u7684\u7f13\u89e3\u6280\u672f(\u4f8b\u5982RELRO)\u7684\u5f71\u54cd\uff0c\u8fd9\u4e00\u5f71\u54cd\u6211\u4eec\u5c06\u5728\u540e\u9762\u8ba8\u8bba\u3002\u800cLeakless\uff0c\u4f5c\u4e3a\u53ea\u67091\u4e2a\u9636\u6bb5\uff0c\u5e73\u53f0\u65e0\u5173\uff0c\u5177\u6709\u666e\u9002\u6027\u7684\u6280\u672f\uff0c\u5728\u8fd9\u6837\u7684\u7f13\u89e3\u6280\u672f\u9762\u524d\u4ecd\u7136\u80fd\u591f\u53d1\u6325\u4f5c\u7528\u3002<\/span><\/p>\n

      \u5728\u4e0b\u4e00\u8282\u4e2d\uff0c\u6211\u4eec\u5c06\u9610\u8ff0\u52a8\u6001\u88c5\u8f7d\u5668\u662f\u5982\u4f55\u5de5\u4f5c\u7684\uff0c\u7136\u540e\u5c06\u4f1a\u5c55\u793a\u5982\u4f55\u6d3b\u7528\u5b83\u7684\u529f\u80fd\u6765\u8fdb\u884c\u6211\u4eec\u7684\u653b\u51fb\u3002<\/span><\/p>\n

      ========================================================================<\/span><\/p>\n

        \n
      1. \u52a8\u6001\u88c5\u8f7d\u5668<\/strong><\/li>\n<\/ol>\n

        \u52a8\u6001\u88c5\u8f7d\u5668\u662f\u4e00\u4e2a\u7528\u6237\u6267\u884c\u73af\u5883\u7684\u7ec4\u4ef6\uff0c\u5b83\u80fd\u591f\u5e2e\u52a9\u5728\u5f00\u59cb\u65f6\u52a0\u8f7d\u5e94\u7528\u9700\u8981\u7684\u5e93\u5e76\u89e3\u6790\u5e93\u5bfc\u51fa\u7684\u52a8\u6001\u7b26\u53f7(\u51fd\u6570\u548c\u5168\u5c40\u53d8\u91cf)\u4f9b\u5e94\u7528\u7a0b\u5e8f\u4f7f\u7528\u3002\u5728\u8fd9\u4e00\u8282\u4e2d\uff0c\u6211\u4eec\u5c06\u4f1a\u9610\u8ff0\u52a8\u6001\u7b26\u53f7\u89e3\u6790\u7684\u8fc7\u7a0b\u5728\u57fa\u4e8eELF\u7684\u7cfb\u7edf\u4e0a\u662f\u5982\u4f55\u5de5\u4f5c\u7684 [33].<\/span><\/p>\n

        ELF\u662fUnix\u7c7b\u5e73\u53f0(\u5305\u62ecGNU\/Linux\u4e0eFreeBSD)\u4e0a\u6bd4\u8f83\u666e\u904d\u7684\u4e00\u79cd\u6807\u51c6\u683c\u5f0f\uff0c\u5176\u5b9a\u4e49\u72ec\u7acb\u4e8e\u4efb\u4f55\u4e00\u79cd\u7279\u5b9a\u52a8\u6001\u88c5\u8f7d\u5668\u5b9e\u73b0\u3002\u56e0\u4e3aLeakless\u4e3b\u8981\u4f9d\u8d56\u4e0eELF\u6807\u51c6\u7684\u7279\u6027\uff0c\u5b83\u4e5f\u5f88\u5bb9\u6613\u5e94\u7528\u4e8e\u5f88\u591a\u7cfb\u7edf\u3002<\/span><\/p>\n

        3.1 ELF\u5bf9\u8c61<\/strong><\/p>\n

        \u4e00\u4e2a\u5e94\u7528\u7531\u4e00\u4e2a\u4e3b\u8981ELF\u4e8c\u8fdb\u5236\u6587\u4ef6(\u53ef\u6267\u884c\u6587\u4ef6)\u548c\u6570\u4e2a\u52a8\u6001\u5e93\u6784\u6210\uff0c\u5b83\u4eec\u90fd\u662fELF\u683c\u5f0f\u3002\u6bcf\u4e2aELF\u5bf9\u8c61\u7531\u591a\u4e2asegments\u7ec4\u6210\uff0c\u6bcf\u4e2asegment\u5219\u542b\u6709\u4e00\u4e2a\u6216\u591a\u4e2asections(\u8bd1\u6ce8: \u4ee5\u4e0b\u79f0sections\u4e3a\u6bb5).<\/span><\/p>\n

        \u6bcf\u4e2a\u6bb5\u90fd\u6709\u7ea6\u5b9a\u7684\u542b\u4e49\u3002\u4e3e\u4e2a\u4f8b\u5b50\uff0c.text\u6bb5\u5305\u542b\u7740\u7a0b\u5e8f\u7684\u4ee3\u7801\uff0c.data\u6bb5\u5305\u542b\u7740\u5b83\u53ef\u5199\u7684\u6570\u636e(\u4f8b\u5982\u5168\u5c40\u53d8\u91cf)\uff0c\u800c.rodata\u6bb5\u5219\u5305\u542b\u7740\u53ea\u8bfb\u7684\u6570\u636e(\u4f8b\u5982\u5e38\u91cf\u548c\u5b57\u7b26\u4e32)\u3002\u6bb5\u7684\u5217\u8868\u4ee5\u6570\u7ec4\u7684\u5f62\u5f0f\u5b58\u4e8eELF\u6587\u4ef6\u7684Elf_Shdr\u7ed3\u6784\u4f53\u4e2d\u3002<\/span><\/p>\n

        \u6ce8\u610f\u8fd9\u91cc\u6709\u4e24\u79cdELF\u7ed3\u6784\u4f53\u7684\u7248\u672c: \u4e00\u79cd\u662f32\u4f4d\u7684(\u4f8b\u5982Elf32_Rel)\uff0c\u4e00\u79cd\u662f64\u4f4d\u7684(\u4f8b\u5982Elf64_Rel).\u4e3a\u4e86\u7b80\u5316\u8d77\u89c1\uff0c\u9664\u4e86\u5728\u76f8\u5173\u8ba8\u8bba\u7684\u7279\u5b9a\u6848\u4f8b\u4e2d\uff0c\u4e00\u822c\u60c5\u51b5\u6211\u4eec\u5c06\u5ffd\u7565\u8fd9\u4e9b\u7ec6\u8282\u3002<\/span><\/p>\n

        3.2 \u52a8\u6001\u7b26\u53f7\u4e0e\u91cd\u5b9a\u4f4d<\/strong><\/p>\n

        \u5728\u8fd9\u4e00\u8282\u4e2d\uff0c\u6211\u4eec\u5c06\u5bf9ELF\u7b26\u53f7\u89e3\u6790\u8fc7\u7a0b\u76f8\u5173\u7684\u6570\u636e\u7ed3\u6784\u8fdb\u884c\u4e00\u4e2a\u603b\u7ed3\u3002\u56fe1\u603b\u4f53\u5c55\u793a\u4e86\u8fd9\u4e9b\u6570\u636e\u7ed3\u6784\u4ee5\u53ca\u5b83\u4eec\u4e4b\u95f4\u7684\u5173\u7cfb\u3002<\/span><\/p>\n

        \"Figure1\"<\/a><\/p>\n

        figure 1: \u5728\u7b26\u53f7\u89e3\u6790\u8fc7\u7a0b\u4e2d\u76f8\u5173\u6570\u636e\u7ed3\u6784\u7684\u5173\u7cfb(\u9664\u53bb\u7b26\u53f7\u7248\u672c)\u3002\u9634\u5f71\u80cc\u666f\u90e8\u5206\u8868\u793a\u53ea\u8bfb\u5185\u5b58\u3002<\/span><\/p>\n

        \u4e00\u4e2aELF\u5bf9\u8c61\u53ef\u4ee5\u5411\u5176\u5b83ELF\u5bf9\u8c61\u5bfc\u51fa\u7b26\u53f7\u6216\u5bfc\u5165\u7b26\u53f7\u3002\u4e00\u4e2a\u7b26\u53f7\u8868\u793a\u4e00\u4e2a\u5177\u6709\u540d\u79f0\u6807\u8bc6\u7684\u51fd\u6570\u6216\u8005\u5168\u5c40\u53d8\u91cf\u3002<\/span><\/p>\n

        \u6bcf\u4e2a\u7b26\u53f7\u90fd\u4f7f\u7528Elf_Sym\u7ed3\u6784\u4f53\u6765\u63cf\u8ff0\u3002\u8fd9\u4e2a\u7ed3\u6784\u4f53\u7684\u5b9e\u4f8b\u662fELF\u4e2d.dynsym\u6bb5\u7684\u7ec4\u6210\u90e8\u5206\uff0c\u5b83\u5305\u542b\u4ee5\u4e0b\u76f8\u5173\u7684\u57df:<\/span><\/p>\n

        [st_name] \u76f8\u5bf9.dynstr\u6bb5\u5f00\u59cb\u7684\u504f\u79fb\u503c\uff0c\u90a3\u91cc\u6709\u8fd9\u4e2a\u7b26\u53f7\u540d\u5b57\u7684\u5b57\u7b26\u4e32\u3002<\/span><\/p>\n

        [st_value] \u5982\u679c\u8fd9\u4e2a\u7b26\u53f7\u88ab\u5bfc\u51fa\uff0c\u5219\u5b58\u6709\u8fd9\u4e2a\u5bfc\u51fa\u51fd\u6570\u7684\u865a\u62df\u5730\u5740\uff0c\u5426\u5219\u4e3aNULL.<\/span><\/p>\n

        \u8fd9\u4e9b\u7ed3\u6784\u88ab\u7528\u6765\u89e3\u6790\u5bfc\u5165\u7684\u7b26\u53f7\u3002\u5bfc\u5165\u7b26\u53f7\u7684\u89e3\u6790\u9700\u8981\u91cd\u5b9a\u4f4d\u7684\u652f\u6301\uff0c\u91cd\u5b9a\u4f4d\u9879\u4ee5Elf_Rel\u7ed3\u6784\u4f53\u6765\u63cf\u8ff0\u3002\u8fd9\u4e2a\u7ed3\u6784\u7684\u5b9e\u4f8b\u5b58\u5728\u4e8e.rel.plt\u6bb5(\u7528\u4e8e\u5bfc\u5165\u51fd\u6570)\u548c.rel.dyn\u6bb5\u4e2d(\u7528\u4e8e\u5bfc\u5165\u5168\u5c40\u53d8\u91cf)\u3002\u5728\u8fd9\u91cc\u6211\u4eec\u611f\u5174\u8da3\u7684\u662f\u524d\u8005\u3002Elf_Rel\u7ed3\u6784\u4f53\u6709\u4ee5\u4e0b\u57df:<\/span><\/p>\n

        [r_info] \u6b64\u57df\u7684\u9ad8\u4f4d3\u4e2a\u5b57\u8282\u4f5c\u4e3a\u4e00\u4e2a\u65e0\u7b26\u53f7\u7684\u4e0b\u6807\uff0c\u8868\u793a\u8fd9\u4e2a\u7b26\u53f7\u5728.dynsym\u6bb5\u4e2d\u7684\u4f4d\u7f6e\u3002<\/span><\/p>\n

        [r_offset] \u89e3\u6790\u540e\u7684\u7b26\u53f7\u5730\u5740\u88ab\u5199\u5165\u5185\u5b58\u4e2d\u7684\u4f4d\u7f6e(\u7edd\u5bf9\u5730\u5740)\u3002<\/span><\/p>\n

        \u5f53\u7a0b\u5e8f\u5bfc\u5165\u4e00\u4e2a\u6b63\u5e38\u51fd\u6570\u65f6\uff0c\u94fe\u63a5\u5668\u4f1a\u5728.dynstr\u6bb5\u4e2d\u5305\u542b\u4e00\u4e2a\u51fd\u6570\u540d\u79f0\u7684\u5b57\u7b26\u4e32\uff0c\u5728.dynsym\u6bb5\u4e2d\u5305\u542b\u4e00\u4e2a\u6307\u5411\u5b83\u7684\u7b26\u53f7(Elf_Sym)\uff0c\u5728.rel.plt\u6bb5\u4e2d\u5305\u542b\u4e00\u4e2a\u6307\u5411\u8fd9\u4e2a\u7b26\u53f7\u7684\u91cd\u5b9a\u4f4d\u9879(Elf_Rel).<\/span><\/p>\n

        \u91cd\u5b9a\u4f4d\u7684\u76ee\u6807(\u5373Elf_Rel\u7ed3\u6784\u4e2d\u7684r_offset\u57df)\u5c06\u4f1a\u662f\u5168\u5c40\u504f\u79fb\u91cf\u8868(Global Offset Table, GOT)\u4e2d\u7684\u4e00\u4e2a\u6761\u76ee\u3002GOT\u8868\u4fdd\u5b58\u4e8e.got.plt\u6bb5\uff0c\u7531\u80fd\u591f\u89e3\u6790.rel.plt\u6bb5\u4e2d\u7684\u91cd\u5b9a\u4f4d\u7684\u52a8\u6001\u94fe\u63a5\u5668\u6765\u586b\u5199\u3002<\/span><\/p>\n

        3.3 \u60f0\u6027\u7b26\u53f7\u89e3\u6790<\/strong><\/p>\n

        \u56e0\u4e3a\u5728\u7a0b\u5e8f\u5f00\u59cb\u65f6\u5c31\u89e3\u6790\u6240\u6709\u5bfc\u5165\u7b26\u53f7\u5e76\u5e94\u7528\u91cd\u5b9a\u4f4d\u662f\u4e00\u9879\u5f00\u9500\u8f83\u5927\u7684\u64cd\u4f5c\uff0c\u7b26\u53f7\u7684\u89e3\u6790\u5c06\u662f\u60f0\u6027\u7684\u3002\u5728\u60f0\u6027\u7b26\u53f7\u89e3\u6790\u4e2d\uff0c\u6bcf\u4e2a\u51fd\u6570\u5730\u5740(\u76f8\u5f53\u4e8eGOT\u4e2d\u7684\u6761\u76ee)\u53ea\u5728\u9700\u8981\u7684\u65f6\u5019\u624d\u8fdb\u884c\u89e3\u6790(\u5373\u8fd9\u4e2a\u51fd\u6570\u7b2c\u4e00\u6b21\u88ab\u8c03\u7528\u7684\u65f6\u5019)\u3002<\/span><\/p>\n

        \u5f53\u4e00\u4e2a\u7a0b\u5e8f\u9700\u8981\u8c03\u7528\u5bfc\u5165\u51fd\u6570\u65f6\uff0c\u4ed6\u5c06\u4f1a\u8c03\u7528\u8fc7\u7a0b\u94fe\u63a5\u8868(Procedure Linkage Table, .plt\u6bb5)\u4e2d\u7684\u4e00\u6bb5\u7279\u5b9a\u4ee3\u7801\u3002\u5c31\u50cf\u5217\u88681\u5c55\u793a\u7684\u90a3\u6837\uff0c\u6bcf\u4e2a\u5bfc\u5165\u51fd\u6570\u5728PLT\u4e2d\u6709\u4e00\u6bb5\u7279\u5b9a\u4ee3\u7801\uff0c\u5176\u6267\u884c\u65e0\u6761\u4ef6\u8df3\u8f6c\u5230\u76f8\u5173\u7684GOT\u6761\u76ee\u3002<\/span><\/p>\n

        \u5728\u7b26\u53f7\u89e3\u6790\u7ed3\u675f\u540e\uff0cGOT\u6761\u76ee\u5df2\u7ecf\u5305\u542b\u4e86\u5b9e\u9645\u51fd\u6570\u7684\u5730\u5740\uff0c\u6240\u4ee5\u6267\u884c\u80fd\u591f\u65e0\u7f1d\u5730\u8fdb\u5165\u5bfc\u5165\u7684\u5e93\u4e2d\u3002\u5f53\u51fd\u6570\u8fd4\u56de\u65f6\uff0c\u63a7\u5236\u6d41\u8fd4\u56de\u5230PLT\u4e2d\u7279\u5b9a\u4ee3\u7801\u7684\u8c03\u7528\u8005\u4f4d\u7f6e\uff0c\u6545\u5269\u4e0b\u7684PLT\u4ee3\u7801\u4e0d\u4f1a\u88ab\u6267\u884c\u3002\u4e0d\u8fc7\uff0c\u5f53\u7a0b\u5e8f\u521a\u542f\u52a8\u65f6\uff0cGOT\u6761\u76ee\u88ab\u521d\u59cb\u5316\u4e3a\u4e00\u4e2a\u6307\u5411\u76f8\u5173PLT\u4ee3\u7801\u7b2c2\u6761\u6307\u4ee4\u7684\u5730\u5740\u3002\u8fd9\u90e8\u5206\u4ee3\u7801\u5c06\u4f1a\u5c06\u5bfc\u5165\u51fd\u6570\u7684\u6807\u8bc6(\u4ee5\u4e00\u4e2aElf_Rel\u5b9e\u4f8b\u5728.rel.plt\u6bb5\u4e2d\u504f\u79fb\u7684\u5f62\u5f0f)\u538b\u6808\uff0c\u7136\u540e\u8df3\u5230.plt\u6bb5\u5f00\u5934PLT0\u7684\u4ee3\u7801\u5904\u3002\u8fd9\u56de\uff0cPLT0\u7684\u4ee3\u7801\uff0c\u5c06GOT[1]\u7684\u503c\u538b\u6808\u5e76\u95f4\u63a5\u8df3\u8f6c\u81f3GOT[2].\u8fd9\u4e24\u4e2aGOT\u8868\u7684\u6761\u76ee\u6709\u7740\u7279\u6b8a\u7684\u542b\u4e49\uff0c\u52a8\u6001\u88c5\u8f7d\u5668\u5728\u5f00\u59cb\u65f6\u7ed9\u4ed6\u4eec\u586b\u5145\u4e86\u7279\u6b8a\u7684\u5185\u5bb9:<\/span><\/p>\n

        – GOT[1]. \u4e00\u4e2a\u6307\u5411\u5185\u90e8\u6570\u636e\u7ed3\u6784\u7684\u6307\u9488\uff0c\u7c7b\u578b\u662flink_map\uff0c\u5728\u52a8\u6001\u88c5\u8f7d\u5668\u5185\u90e8\u4f7f\u7528\uff0c\u5305\u542b\u4e86\u8fdb\u884c\u7b26\u53f7\u89e3\u6790\u9700\u8981\u7684\u5f53\u524dELF\u5bf9\u8c61\u7684\u4fe1\u606f\u3002<\/span><\/p>\n

        – GOT[2]. \u4e00\u4e2a\u6307\u5411\u52a8\u6001\u88c5\u8f7d\u5668\u4e2d_dl_runtime_resolve\u51fd\u6570\u7684\u6307\u9488\u3002<\/span><\/p>\n

        \u603b\u7684\u6765\u8bf4\uff0cPLT\u6761\u76ee\u53ea\u662f\u8fdb\u884c\u4e86\u4ee5\u4e0b\u51fd\u6570\u8c03\u7528:<\/span><\/p>\n

        _dl_runtime_resolve(link_map_obj, reloc_index)<\/span><\/p>\n

        \u8fd9\u4e2a\u51fd\u6570\u4f7f\u7528link_map_obj\u53c2\u6570\u6765\u53d6\u5f97\u89e3\u6790\u5bfc\u5165\u51fd\u6570(\u4f7f\u7528reloc_index\u53c2\u6570\u6807\u8bc6)\u9700\u8981\u7684\u4fe1\u606f\uff0c\u5e76\u5c06\u7ed3\u679c\u5199\u5230\u6b63\u786e\u7684GOT\u6761\u76ee\u4e2d\u3002\u5728_dl_runtime_resolve\u89e3\u6790\u5b8c\u6210\u5bfc\u5165\u7b26\u53f7\u4e2d\uff0c\u63a7\u5236\u6d41\u5c31\u4ea4\u5230\u4e86\u90a3\u4e2a\u51fd\u6570\u624b\u4e2d\uff0c\u4f7f\u5f97\u89e3\u6790\u7684\u8fc7\u7a0b\u5bf9\u8c03\u7528\u8005\u6765\u8bf4\u5b8c\u5168\u900f\u660e\u3002\u4e0b\u6b21PLT\u4ee3\u7801\u8c03\u7528\u65f6\u5219\u4f1a\u76f4\u63a5\u8fdb\u5165\u76ee\u6807\u51fd\u6570\u6267\u884c\u3002<\/span><\/p>\n

        \"Listing1\"<\/a><\/p>\n

        Listing 1: PLT\u4e0eGOT\u7684\u4f8b\u5b50<\/span><\/p>\n

        link_map\u7ed3\u6784\u4f53\u5305\u542b\u4e86\u52a8\u6001\u88c5\u8f7d\u5668\u52a0\u8f7dELF\u5bf9\u8c61\u9700\u8981\u7684\u5168\u90e8\u4fe1\u606f\u3002\u6bcf\u4e2alink_map\u5b9e\u4f8b\u90fd\u662f\u4e00\u6761\u53cc\u5411\u94fe\u8868\u7684\u4e00\u4e2a\u8282\u70b9\uff0c\u800c\u8fd9\u4e2a\u94fe\u8868\u4fdd\u5b58\u4e86\u6240\u6709\u52a0\u8f7d\u7684ELF\u5bf9\u8c61\u7684\u4fe1\u606f\u3002<\/span><\/p>\n

        3.4 \u7b26\u53f7\u7248\u672c<\/strong><\/p>\n

        ELF\u6807\u51c6\u63d0\u4f9b\u4e86\u4e00\u4e2a\u53ef\u4ee5\u5bfc\u5165\u4e00\u4e2a\u7279\u5b9a\u7248\u672c\u7b26\u53f7\u7684\u673a\u80fd\u3002\u8fd9\u4e2a\u7279\u6027\u88ab\u7528\u4e8e\u4ece\u4e00\u4e2a\u7279\u5b9a\u7684\u5e93\u4e2d\u5bfc\u5165\u51fd\u6570\u3002\u4f8b\u5982\uff0c\u4f7f\u7528\u7248\u672c\u6807\u8bc6GLIBC_2.2.5\uff0c\u5c31\u53ef\u4ee5\u4ece2.2.5\u7248\u672c\u7684GNU C\u6807\u51c6\u5e93\u4e2d\u5bfc\u5165fopen\u8fd9\u4e2aC\u6807\u51c6\u5e93\u51fd\u6570\u3002.gnu.version_r\u6bb5\u4fdd\u5b58\u4e86\u7248\u672c\u7684\u5b9a\u4e49\uff0c\u5f62\u5f0f\u662fElf_Verdef\u7ed3\u6784\u4f53\u3002<\/span><\/p>\n

        \u4e00\u4e2a\u52a8\u6001\u7b26\u53f7\u4e0e\u6307\u5411\u5b83\u7684Elf_Verdef\u7684\u5173\u8054\u4fdd\u5b58\u5728.gnu.version\u6bb5\u4e2d\uff0c\u5176\u4e2d\u6709\u4e00\u4e2aElf_Verneed\u7ed3\u6784\u4f53\u7ec4\u6210\u7684\u6570\u7ec4\uff0c\u6bcf\u4e2a\u5143\u7d20\u5bf9\u5e94\u52a8\u6001\u7b26\u53f7\u8868\u4e2d\u7684\u4e00\u9879\u3002\u8fd9\u4e2a\u7ed3\u6784\u4f53\u53ea\u6709\u4e00\u4e2a\u57df: \u4e00\u4e2a16\u4f4d\u7684\u6574\u6570\uff0c\u8868\u793a.gnu.version_r\u6bb5\u4e2d\u7684\u4e0b\u6807\u3002<\/span><\/p>\n

        \u5f97\u76ca\u4e8e\u8fd9\u6837\u7684\u5e03\u5c40\uff0c\u52a8\u6001\u8fde\u63a5\u5668\u4f7f\u7528Elf_Rel\u7ed3\u6784\u4f53\u6210\u5458r_info\u4e2d\u7684\u4e0b\u6807\u540c\u65f6\u4f5c\u4e3a.dynsym\u6bb5\u548c.gnu.version\u6bb5\u7684\u4e0b\u6807\u3002\u7406\u89e3\u8fd9\u4e00\u8fc7\u7a0b\u975e\u5e38\u91cd\u8981\uff0c\u56e0\u4e3aLeakless\u4e4b\u540e\u5c06\u88ab\u5b83\u6240\u6270\u3002<\/p>\n

        3.5 .dynamic\u6bb5\u548cRELRO<\/strong><\/p>\n

        \u52a8\u6001\u88c5\u8f7d\u5668\u4ece.dynamic\u6bb5\u6536\u96c6\u6240\u6709\u5b83\u9700\u8981\u7684\u5173\u4e8eELF\u5bf9\u8c61\u7684\u4fe1\u606f\u3002.dynamic\u6bb5\u7531Elf_Dyn\u7ed3\u6784\u7ec4\u6210\uff0c\u4e00\u4e2aElf_Dyn\u662f\u4e00\u4e2a\u952e\u503c\u5bf9\uff0c\u5176\u4e2d\u5b58\u50a8\u4e86\u4e0d\u540c\u7c7b\u578b\u7684\u4fe1\u606f\u3002\u76f8\u5173\u7684\u6761\u76ee\u5df2\u7ecf\u5728\u88681\u4e2d\u5c55\u793a\uff0c\u5b83\u4eec\u4fdd\u5b58\u7740\u7279\u5b9a\u6bb5\u7684\u7edd\u5bf9\u5730\u5740\u3002\u6709\u4e00\u4e2a\u4f8b\u5916\u662fDT_DEBUG\u6761\u76ee\uff0c\u5b83\u4fdd\u5b58\u7684\u52a8\u6001\u88c5\u8f7d\u5668\u5185\u90e8\u6570\u636e\u7ed3\u6784\u7684\u6307\u9488\u3002\u8fd9\u4e2a\u6761\u76ee\u662f\u4e3a\u4e86\u8c03\u8bd5\u7684\u9700\u8981\u7531\u52a8\u6001\u88c5\u8f7d\u5668\u521d\u59cb\u5316\u7684\u3002<\/span><\/p>\n

        \"Table1\"<\/a><\/p>\n

        Table 1: .dynamic\u6bb5\u7684\u6761\u76ee\uff0cd_tag\u662f\u952e\uff0cd_value\u662f\u503c\u3002<\/span><\/p>\n

        \u4e00\u4e2a\u653b\u51fb\u8005\u5982\u679c\u80fd\u5e72\u6270\u8fd9\u4e9b\u503c\uff0c\u90a3\u5c06\u4f1a\u9020\u6210\u5b89\u5168\u5a01\u80c1\u3002\u4e3a\u6b64\uff0c\u4e00\u79cd\u79f0\u4f5cRELRO(\u91cd\u5b9a\u4f4d\u53ea\u8bfb RELocation Read Only)\u4fdd\u62a4\u673a\u5236\u88ab\u5f15\u5165\u4e86\u52a8\u6001\u88c5\u8f7d\u5668\u3002RELRO\u67092\u79cd\u5f62\u5f0f\uff1a\u90e8\u5206\u548c\u5b8c\u5168\u3002<\/span><\/p>\n

        [\u90e8\u5206RELRO] \u5728\u8fd9\u79cd\u6a21\u5f0f\u4e0b\uff0c\u4e00\u4e9b\u6bb5(\u5305\u62ec.dynamic)\u5728\u521d\u59cb\u5316\u540e\u5c06\u4f1a\u88ab\u6807\u8bc6\u4e3a\u53ea\u8bfb\u3002<\/span><\/p>\n

        [\u5b8c\u5168RELRO] \u9664\u4e86\u90e8\u5206RELRO\uff0c\u60f0\u6027\u89e3\u6790\u4f1a\u88ab\u7981\u7528: \u6240\u6709\u7684\u5bfc\u5165\u7b26\u53f7\u5c06\u5728\u5f00\u59cb\u65f6\u88ab\u89e3\u6790\uff0c.got.plt\u6bb5\u4f1a\u88ab\u5b8c\u5168\u521d\u59cb\u5316\u4e3a\u76ee\u6807\u51fd\u6570\u7684\u6700\u7ec8\u5730\u5740\uff0c\u5e76\u88ab\u6807\u8bb0\u4e3a\u53ea\u8bfb\u3002\u6b64\u5916\uff0c\u65e2\u7136\u60f0\u6027\u89e3\u6790\u88ab\u7981\u7528\uff0cGOT[1]\u4e0eGOT[2]\u6761\u76ee\u5c06\u4e0d\u4f1a\u88ab\u521d\u59cb\u5316\u4e3a\u4e4b\u524d\u57283.3\u8282\u4e2d\u63d0\u5230\u7684\u503c\u3002<\/span><\/p>\n

        \u53ef\u4ee5\u770b\u5230\uff0cRELRO\u663e\u8457\u5730\u589e\u52a0\u4e86\u590d\u6742\u6027\uff0cLeakless\u4e3a\u4e86\u80fd\u5728\u8fd9\u4e9b\u5bf9\u6297\u63aa\u65bd\u4e0b\u5de5\u4f5c\uff0c\u5fc5\u987b\u89e3\u51b3\u8fd9\u4e2a\u95ee\u9898(\u5b83\u4e5f\u505a\u5230\u4e86)\u3002<\/span><\/p>\n

        \u503c\u5f97\u6ce8\u610f\u7684\u662f\u4e4b\u524d\u63d0\u5230\u7684link_map\u7ed3\u6784\u51fa\u4e8e\u5185\u90e8\u7528\u9014\u8003\u8651\uff0c\u5728l_info\u57df\u4e2d\u4fdd\u5b58\u4e86.dynamic\u6bb5\u4e2d\u5927\u591a\u6570\u6761\u76ee\u7684\u6307\u9488\u6784\u6210\u7684\u4e00\u4e2a\u6570\u7ec4\u3002\u65e2\u7136\u52a8\u6001\u88c5\u8f7d\u5668\u5b8c\u5168\u5730\u4fe1\u4efb\u8fd9\u4e2a\u57df\u7684\u5185\u5bb9\uff0c\u90a3\u4e48Leakless\u5c06\u6709\u80fd\u529b\u5de7\u7528\u8fd9\u4e2a\u7ed3\u6784\u8fbe\u6210\u81ea\u5df1\u7684\u76ee\u7684\u3002<\/span><\/p>\n

        ========================================================================<\/span><\/p>\n

          \n
        1. \u653b\u51fb<\/strong><\/li>\n<\/ol>\n

          Leakless\u4f7f\u653b\u51fb\u8005\u53ea\u7528\u540d\u5b57\u5c31\u80fd\u591f\u8c03\u7528\u4efb\u610f\u5e93\u51fd\u6570\uff0c\u4e0d\u9700\u8981\u5173\u4e8e\u5185\u5b58\u5e03\u5c40\u4ee5\u53ca\u6f0f\u6d1e\u7a0b\u5e8f\u5e93\u7684\u4fe1\u606f\u3002\u4e3a\u4e86\u8fbe\u5230\u8fd9\u4e2a\u76ee\u6807\uff0cLeakless\u6d3b\u7528\u4e86\u52a8\u6001\u88c5\u8f7d\u5668\uff0c\u5f3a\u8feb\u5176\u89e3\u6790\u8bf7\u6c42\u7684\u51fd\u6570\u3002\u7531\u4e8e\u5b83\u548c\u5185\u5b58\u7834\u574f\u6f0f\u6d1e\u7684\u7834\u574f\u6027\u6709\u7740\u540c\u6837\u7684\u6839\u6e90: \u53ef\u63a7\u6570\u636e\u548c\u4e0d\u53ef\u63a7\u6570\u636e\u7684\u6df7\u6742\uff0c\u6240\u4ee5\u8fd9\u6837\u7684\u653b\u51fb\u540c\u6837\u53ef\u80fd\u3002\u5728\u6808\u6ea2\u51fa\u7684\u653b\u51fb\u6848\u4f8b\u4e2d\uff0c\u53ef\u63a7\u6570\u636e\u7684\u95ee\u9898\u5c31\u51fa\u5728\u4fdd\u5b58\u7684\u8fd4\u56de\u5730\u5740\u4e0a\u3002\u5bf9\u4e8e\u52a8\u6001\u88c5\u8f7d\u5668\u6765\u8bf4\uff0c\u53ef\u63a7\u6570\u636e\u5c31\u662f\u4f17\u591a\u7528\u4e8e\u7b26\u53f7\u89e3\u6790\u7684\u6570\u636e\u7ed3\u6784\u3002\u7279\u522b\u5730\uff0c\u51fd\u6570\u7684\u540d\u5b57\uff0c\u4fdd\u5b58\u5728.dynstr\u6bb5\u4e2d\uff0c\u4e0e\u8fd4\u56de\u5730\u5740\u76f8\u4f3c: \u5f53\u51fd\u6570\u88ab\u8c03\u7528\uff0c\u5b83\u4e5f\u6307\u5b9a\u4e86\u4e00\u4e2a\u7279\u5b9a\u7684\u6267\u884c\u76ee\u6807\u3002<\/span><\/p>\n

          \u52a8\u6001\u88c5\u8f7d\u5668\u8ba4\u4e3a\u5b83\u63a5\u6536\u5230\u7684\u53c2\u6570\u90fd\u662f\u503c\u5f97\u4fe1\u4efb\u7684\uff0c\u56e0\u4e3a\u5b83\u5047\u8bbe\u8fd9\u4e9b\u90fd\u662f\u76f4\u63a5\u7531ELF\u6587\u4ef6\u63d0\u4f9b\u7684\u6216\u8005\u662f\u5b83\u81ea\u5df1\u5728\u5f00\u59cb\u65f6\u521d\u59cb\u5316\u7684\u3002\u7136\u800c\uff0c\u5f53\u4e00\u4e2a\u653b\u51fb\u8005\u80fd\u591f\u4fee\u6539\u8fd9\u4e9b\u6570\u636e\u65f6\uff0c\u8fd9\u4e2a\u5047\u8bbe\u5c31\u4e0d\u6210\u7acb\u4e86\u3002\u4e00\u4e9b\u52a8\u6001\u88c5\u8f7d\u5668(FreeBSD)\u4f1a\u9a8c\u8bc1\u81ea\u5df1\u63a5\u6536\u5230\u7684\u8f93\u5165\u3002\u7136\u800c\uff0c\u4ed6\u4eec\u8fd8\u662f\u5b8c\u5168\u5730\u4fe1\u4efb\u63a7\u5236\u7ed3\u6784\uff0c\u4f46\u8fd9\u4e9b\u4e5f\u4f1a\u88abLeakless\u8f7b\u6613\u5730\u7834\u574f\u3002<\/span><\/p>\n

          Leakless\u88ab\u8bbe\u8ba1\u7528\u4e8e\u5229\u7528\u4e00\u4e2a\u5b58\u5728\u7684\u6f0f\u6d1e(\u6307\u7f13\u51b2\u533a\u6ea2\u51fa\u7b49)\u3002Leakless\u7684\u8f93\u5165\u5305\u62ec\u53ef\u6267\u884cELF\u6587\u4ef6\uff0c\u4e00\u7ec4ROP Gadgets\u7684\u96c6\u5408\uff0c\u548c\u653b\u51fb\u8005\u5e0c\u671b\u8c03\u7528\u7684\u5e93\u51fd\u6570\u540d\u79f0(\u5178\u578b\u7684\u4f8b\u5b50\u5c31\u662fexecve())\u3002\u6709\u4e86\u8fd9\u4e9b\u4fe1\u606f\uff0cLeakless\u8f93\u51fa\u4e00\u6bb5ROP\u7684\u653b\u51fb\u8f7d\u8377(payload)\u80fd\u591f\u6267\u884c\u9700\u8981\u7684\u5e93\u51fd\u6570\uff0c\u4e14\u80fd\u591f\u7ed5\u8fc7\u591a\u79cd\u5e94\u7528\u5728\u4e8c\u8fdb\u5236\u6587\u4ef6\u4e0a\u7684\u52a0\u56fa\u6280\u672f\u3002\u8fd9\u6bb5ROP\u94fe\u901a\u5e38\u6765\u8bf4\u975e\u5e38\u77ed: \u4f9d\u8d56\u4e8e\u4e8c\u8fdb\u5236\u6587\u4ef6\u4e2d\u7684\u51cf\u7f13\u6280\u672f\uff0c\u9700\u89813\u523012\u6b21\u4e0d\u7b49\u7684\u5199\u64cd\u4f5c\u3002\u4e00\u4e9bLeakless\u4ea7\u751f\u7684\u8f93\u51fa\u7684\u4f8b\u5b50\u80fd\u591f\u5728Leakless\u4ee3\u7801\u5e93\u7684\u6587\u6863\u91cc\u627e\u5230 [17].<\/span><\/p>\n

          Leakless\u4e0d\u9700\u8981\u4efb\u4f55\u5173\u4e8e\u5e93\u5730\u5740\u548c\u5185\u5bb9\u7684\u4fe1\u606f; \u6211\u4eec\u5047\u8bbeASLR\u5728\u6240\u6709\u7684\u52a8\u6001\u5e93\u4e0a\u542f\u7528\u4e14\u4e0d\u80fd\u83b7\u5f97\u5173\u4e8e\u5b83\u4eec\u7684\u4efb\u4f55\u77e5\u8bc6\u3002\u7136\u800c\uff0c\u6211\u4eec\u9700\u8981\u5047\u8bbe\u53ef\u6267\u884c\u6587\u4ef6\u4e0d\u662f\u201c\u4f4d\u7f6e\u65e0\u5173\u7684\u201d\uff0c\u6240\u4ee5\u5b83\u4eec\u4f1a\u88ab\u52a0\u8f7d\u5230\u5185\u5b58\u4e2d\u7684\u7279\u5b9a\u4f4d\u7f6e\u3002\u6211\u4eec\u57287.2\u8282\u4e2d\u8ba8\u8bba\u4e86\u8fd9\u4e2a\u9650\u5236\uff0c\u5e76\u4e14\u57286.2\u8282\u4e2d\u5c55\u793a\u4e86\u4f4d\u7f6e\u65e0\u5173\u53ef\u6267\u884c(Position Independent Executables, PIE)\u6587\u4ef6\u5728\u73b0\u4ee3\u64cd\u4f5c\u7cfb\u7edf\u4e2d\u7684\u5206\u5e03\u60c5\u51b5\u3002<\/span><\/p>\n

          \"Figure2\"<\/a><\/p>\n

          Figure 2: \u653b\u51fb\u56fe\u793a\u3002\u9634\u5f71\u80cc\u666f\u8868\u793a\u53ea\u8bfb\u7684\u5185\u5b58\uff0c\u767d\u8272\u80cc\u666f\u8868\u793a\u53ef\u5199\u7684\u5185\u5b58\uff0c\u7ea2\u8272\u6216\u52a0\u7c97\u7684\u90e8\u5206\u8868\u793a\u653b\u51fb\u8005\u4f2a\u9020\u7684\u6570\u636e<\/span><\/p>\n

          a) 4.1\u8282\u4e2d\u653b\u51fb\u7684\u4f8b\u5b50\u3002\u653b\u51fb\u8005\u80fd\u591f\u6539\u5199DT_STRTAB\u6761\u76ee\u7684\u5185\u5bb9\uff0c\u6b3a\u9a97\u52a8\u6001\u88c5\u8f7d\u5668\u4f7f\u5176\u8ba4\u4e3a.dynstr\u6bb5\u5728.bss\u6bb5\u4e2d\uff0c\u5e76\u5728\u90a3\u91cc\u4f2a\u9020\u4e00\u4e2a\u5047\u7684\u5b57\u7b26\u4e32\u8868\u3002\u5f53\u52a8\u6001\u88c5\u8f7d\u5668\u5c1d\u8bd5\u89e3\u6790printf\u65f6\u5c06\u4f1a\u4f7f\u7528\u4e0d\u540c\u7684\u57fa\u5730\u5740\u6765\u5bfb\u627e\u51fd\u6570\u7684\u540d\u79f0\uff0c\u6700\u7ec8\u5b9e\u9645\u4f1a\u89e3\u6790\u5e76\u6267\u884cexecve.<\/span><\/p>\n

          b) 4.2\u8282\u4e2d\u653b\u51fb\u7684\u4f8b\u5b50\u3002\u4f20\u9012\u7ed9_dl_runtime_resolve\u7684\u53c2\u6570reloc_index\u8d85\u51fa\u4e86.rel.plt\u6bb5\u5e76\u6700\u7ec8\u843d\u5728.bss\u6bb5\uff0c\u5728\u90a3\u91cc\u653b\u51fb\u8005\u4f2a\u9020\u4e86Elf_Rel\u7ed3\u6784\u3002\u8fd9\u4e2a\u91cd\u5b9a\u4f4d\u9879\u6307\u5411\u4e00\u4e2a\u5c31\u4f4d\u4e8e\u5176\u540e\u7684Elf_Sym\u7ed3\u6784\uff0c\u800cElf_Sym\u7ed3\u6784\u4e2d\u7684index\u540c\u6837\u8d85\u51fa\u4e86.dynsym\u6bb5\u3002\u8fd9\u6837\u8fd9\u4e2a\u7b26\u53f7\u5c31\u4f1a\u5305\u542b\u4e00\u4e2a\u76f8\u5bf9.dynstr\u5730\u5740\u8db3\u591f\u5927\u7684\u504f\u79fb\u4f7f\u5176\u80fd\u591f\u8fbe\u5230\u8fd9\u4e2a\u7b26\u53f7\u4e4b\u540e\u7684\u4e00\u6bb5\u5185\u5b58\uff0c\u90a3\u91cc\u4fdd\u5b58\u7740\u8fd9\u4e2a\u5c06\u8981\u8c03\u7528\u7684\u51fd\u6570\u7684\u540d\u79f0\u3002<\/span><\/p>\n

          \u5728\u591a\u6570\u60c5\u51b5\u4e0b\uff0cLeakless\u5e76\u4e0d\u4f9d\u8d56\u76ee\u6807\u7cfb\u7edf\u4e0a\u8fd0\u884c\u7684\u52a8\u6001\u88c5\u8f7d\u5668\u7684\u5b9e\u73b0\u548c\u7248\u672c\uff0c\u4e0d\u8fc7\u6709\u4e9b\u653b\u51fb\u9700\u8981\u4e00\u4e9b\u5c0f\u7684\u6539\u52a8\u4ee5\u9002\u5e94\u4e0d\u540c\u7684\u52a8\u6001\u88c5\u8f7d\u5668\u5b9e\u73b0\u3002<\/span><\/p>\n

          \u503c\u5f97\u6ce8\u610f\u7684\u662fLeakless\u7684\u76ee\u6807\uff0c\u5373\u83b7\u5f97\u4e00\u4e2a\u5e93\u51fd\u6570\u7684\u5730\u5740\u5e76\u6267\u884c\u5b83\uff0c\u4e0elibdl\u5e93\u4e2d\u7684dlsym\u51fd\u6570\u5341\u5206\u76f8\u4f3c\u3002\u4f46\u5728\u5b9e\u9645\u5f53\u4e2d\u8fd9\u4e2a\u51fd\u6570\u5f88\u5c11\u88ab\u5e94\u7528\u7a0b\u5e8f\u4f7f\u7528\uff0c\u6240\u4ee5\uff0c\u5b83\u7684\u5730\u5740\u4e00\u822c\u653b\u51fb\u8005\u4e5f\u4e0d\u77e5\u9053\u3002<\/span><\/p>\n

          4.1 \u57fa\u7840\u60c5\u5f62<\/strong><\/p>\n

          \u5c31\u50cf\u7b2c3\u8282\u4e0e\u56fe1\u4e2d\u5c55\u793a\u7684\u90a3\u6837\uff0c\u52a8\u6001\u88c5\u8f7d\u5668\u4ece.rel.plt\u4e2d\u7684Elf_Rel\u7ed3\u6784\u5f00\u59cb\u5de5\u4f5c\uff0c\u987a\u7740\u5176\u4e2d\u7684\u4e0b\u6807\u627e\u5230.dynsym\u6bb5\u4e2d\u5bf9\u5e94Elf_Sym\u7ed3\u6784\u7684\u4f4d\u7f6e\uff0c\u5e76\u6700\u7ec8\u4f7f\u7528\u5b83\u786e\u5b9a\u5f85\u89e3\u6790\u7b26\u53f7\u7684\u540d\u79f0(\u5728.dynstr\u6bb5\u4e2d\u7684\u4e00\u6bb5\u5b57\u7b26\u4e32)\u3002\u6700\u7b80\u5355\u7684\u8c03\u7528\u4efb\u610f\u51fd\u6570\u7684\u529e\u6cd5\u5c31\u662f\u4f7f\u7528\u5e0c\u671b\u7684\u51fd\u6570\u7684\u540d\u79f0\u8986\u76d6\u5b57\u7b26\u4e32\u8868\u4e2d\u7684\u6761\u76ee\uff0c\u7136\u540e\u518d\u8c03\u7528\u52a8\u6001\u88c5\u8f7d\u5668\uff0c\u4f46\u8fd9\u662f\u4e0d\u53ef\u80fd\u7684\uff0c\u56e0\u4e3a\u4fdd\u5b58\u7740\u52a8\u6001\u7b26\u53f7\u5b57\u7b26\u4e32\u8868\u7684\u6bb5\uff0c\u5373.dynstr\uff0c\u662f\u4e0d\u53ef\u5199\u7684\u3002<\/span><\/p>\n

          \u7136\u800c\uff0c\u52a8\u6001\u88c5\u8f7d\u5668\u662f\u4ece.dynamic\u6bb5\u7684DT_STRTAB\u6761\u76ee\u4e2d\u83b7\u5f97.dynstr\u6bb5\u7684\u5730\u5740\u7684\uff0c\u800c\u4e14DT_STRTAB\u6761\u76ee\u7684\u4f4d\u7f6e\u662f\u5df2\u77e5\u7684\uff0c\u9ed8\u8ba4\u60c5\u51b5\u4e0b\u4e5f\u53ef\u5199\u3002\u8fd9\u6837\uff0c\u5c31\u50cf\u56fe2a\u4e2d\u5c55\u793a\u7684\u90a3\u6837\uff0c\u6211\u4eec\u53ef\u4ee5\u5c06\u8fd9\u4e2a\u6761\u76ee\u7684d_val\u57df\u8986\u76d6\u4e3a\u4e00\u4e2a\u6307\u5411\u653b\u51fb\u8005\u63a7\u5236\u5185\u5b58\u533a\u57df\u7684\u6307\u9488(\u5178\u578b\u7684\u5c31\u662f.bss\u6216.data\u6bb5)\u3002\u8fd9\u5757\u5185\u5b58\u533a\u57df\u4e0a\u5c06\u4f1a\u5305\u542b\u4e00\u6bb5\u5b57\u7b26\u4e32\uff0c\u6bd4\u5982execve\u3002\u5230\u4e86\u8fd9\u4e00\u6b65\uff0c\u653b\u51fb\u8005\u9700\u8981\u9009\u62e9\u4e00\u4e2a\u5df2\u7ecf\u5b58\u5728\u7684\u7b26\u53f7\uff0c\u5b83\u7684\u504f\u79fb\u5728\u4f2a\u9020\u7684\u5b57\u7b26\u4e32\u8868\u4e2d\u6b63\u597d\u6307\u5411execve\u7684\u4f4d\u7f6e\uff0c\u63a5\u7740\u8c03\u7528\u5176\u5bf9\u5e94\u7684\u7b26\u53f7\u89e3\u6790\u91cd\u5b9a\u4f4d\u8fc7\u7a0b\u3002\u53ef\u4ee5\u901a\u8fc7\u5c06\u5176\u91cd\u5b9a\u4f4d\u9879\u7684\u504f\u79fb\u538b\u6808\u5e76\u8df3\u8f6c\u5230PLT0\u5b9e\u73b0\u3002<\/span><\/p>\n

          \u8fd9\u79cd\u65b9\u5f0f\u975e\u5e38\u7b80\u5355\uff0c\u4f46\u4ec5\u5f53\u4e8c\u8fdb\u5236\u7a0b\u5e8f\u7684.dynamic\u6bb5\u53ef\u5199\u65f6\u6709\u6548\u3002\u5bf9\u4e8e\u4f7f\u7528\u90e8\u5206\u6216\u5b8c\u5168RELRO\u7f16\u8bd1\u7684\u4e8c\u8fdb\u5236\u7a0b\u5e8f\uff0c\u9700\u8981\u4f7f\u7528\u66f4\u590d\u6742\u7684\u653b\u51fb\u3002<\/span><\/p>\n

          4.2 \u7ed5\u8fc7\u90e8\u5206RELRO<\/strong><\/p>\n

          \u5c31\u50cf\u6211\u4eec\u57283.3\u8282\u4e2d\u89e3\u91ca\u7684\u90a3\u6837\uff0c_dl_runtime_resolve\u51fd\u6570\u7684\u7b2c\u4e8c\u4e2a\u53c2\u6570\u662fElf_Rel\u6761\u76ee\u5728\u91cd\u5b9a\u4f4d\u8868(.rel.plt\u6bb5)\u4e2d\u5bf9\u5e94\u5f53\u524d\u8bf7\u6c42\u51fd\u6570\u7684\u7684\u504f\u79fb\u3002\u52a8\u6001\u88c5\u8f7d\u5668\u5c06\u8fd9\u4e2a\u503c\u52a0\u4e0a.rel.plt\u7684\u57fa\u5730\u5740\u6765\u5f97\u5230\u76ee\u6807Elf_Rel\u7ed3\u6784\u7684\u7edd\u5bf9\u5730\u5740\u3002\u7136\u800c\u591a\u6570\u52a8\u6001\u88c5\u8f7d\u5668\u5b9e\u73b0\u4e0d\u53bb\u68c0\u67e5\u91cd\u5b9a\u4f4d\u8868\u7684\u8fb9\u754c\u3002\u8fd9\u5c31\u8868\u660e\u5982\u679c\u4e00\u4e2a\u5927\u4e8e.rel.plt\u7684\u503c\u4f20\u5230_dl_runtime_resolve\u4e2d\uff0c\u88c5\u8f7d\u5668\u5c06\u4f1a\u8ba4\u4e3a\u7279\u5b9a\u7684\u5730\u5740\u4e0a\u7684\u6570\u636e\u662f\u4e00\u4e2aElf_Rel\u7ed3\u6784\u5e76\u4f7f\u7528\u5b83\uff0c\u5373\u4f7f\u90a3\u91cc\u5df2\u7ecf\u8d85\u51fa\u4e86.rel<\/span>.plt\u6bb5\u7684\u8303\u56f4\u3002<\/span><\/p>\n

          \u5c31\u50cf\u56fe2b\u663e\u793a\u7684\u90a3\u6837\uff0cLeakless\u8ba1\u7b97\u4e00\u4e2a\u80fd\u591f\u5c06_dl_runtime_resolve\u5bfc\u5411\u5230\u653b\u51fb\u8005\u63a7\u5236\u7684\u5185\u5b58\u7a7a\u95f4\u7684\u4e0b\u6807\u503c\u3002\u7136\u540e\u5b83\u5236\u9020\u4e00\u4e2aElf_Rel\u7ed3\u6784\uff0c\u5e76\u586b\u5199r_offset\u7684\u503c\u4e3a\u4e00\u4e2a\u53ef\u5199\u7684\u5185\u5b58\u5730\u5740\u6765\u5c06\u89e3\u6790\u540e\u7684\u51fd\u6570\u5730\u5740\u5199\u5728\u90a3\u91cc\u3002\u540c\u7406\uff0cr_info\u7684\u503c\u5c06\u4f1a\u662f\u4e00\u4e2a\u5c06\u52a8\u6001\u88c5\u8f7d\u5668\u5bfc\u5411\u5230\u653b\u51fb\u8005\u63a7\u5236\u5185\u5b58\u7684\u4e0b\u6807\u3002Leakless\u4f1a\u5c06\u4e00\u4e2a\u4f2a\u9020\u7684Elf_Sym\u5bf9\u8c61\u653e\u5728\u90a3\u4e2a\u4e0b\u6807\u5bf9\u5e94\u7684\u4f4d\u7f6e\uff0c\u5176\u4e2d\u7684st_name\u57df\uff0c\u8fd9\u4e2a\u503c\u4e5f\u5927\u5230\u8db3\u4ee5\u8fbe\u5230\u653b\u51fb\u8005\u63a7\u5236\u7684\u5185\u5b58\u3002\u5728\u8fd9\u6bb5\u5185\u5b58\u6700\u540e\uff0cLeakless\u4f1a\u653e\u7f6e\u5c06\u8981\u6267\u884c\u7684\u51fd\u6570\u7684\u540d\u79f0\u3002<\/span><\/p>\n

          \u603b\u4e4b\uff0cLeakless\u5c06\u8fd9\u4e00\u6761\u7b26\u53f7\u89e3\u6790\u8fc7\u7a0b\u4e2d\u9700\u8981\u4f7f\u7528\u7684\u7ed3\u6784\u94fe\u5168\u90e8\u90fd\u4f2a\u9020\u4e86\u51fa\u6765\uff0c\u5b8c\u5168\u63a7\u5236\u4e86\u5bf9\u4e8e\u653b\u51fb\u8005\u63a7\u5236\u5185\u5b58\u4e2d\u5185\u5bb9\u7684\u201c\u51fd\u6570\u8c03\u7528\u201d\u8fc7\u7a0b\u3002\u5728\u8fd9\u4e4b\u540e\uff0cLeakless\u5c06\u8ba1\u7b97\u597d\u7684\u5047Elf_Rel\u7ed3\u6784\u7684\u504f\u79fb\u538b\u6808\uff0c\u5e76\u8c03\u7528PLT0\u4ee3\u7801\u3002<\/span><\/p>\n

          \u7136\u800c\uff0c\u8fd9\u4e2a\u65b9\u6cd5\u4f1a\u53d7\u5230\u51e0\u4e2a\u9650\u5236\u3002\u9996\u5148\uff0cElf_Rel\u7684\u4e0b\u6807\u9700\u8981\u662f\u6b63\u6570\uff0c\u56e0\u4e3ar_info\u57df\u5728ELF\u6807\u51c6\u4e2d\u89c4\u5b9a\u662f\u4e00\u4e2a\u65e0\u7b26\u53f7\u6574\u6570\u3002\u8fd9\u5c31\u610f\u5473\u7740\u5728\u5b9e\u9645\u4e2d\u8fd9\u5757\u53ef\u5199\u7684\u5185\u5b58\u7a7a\u95f4(\u4f8b\u5982.bss\u6bb5)\u5fc5\u987b\u662f\u4f4d\u4e8e.dynsym\u6bb5\u4e4b\u540e\u3002\u5728\u6211\u4eec\u7684\u8bc4\u4f30\u4e2d\uff0c\u60c5\u51b5\u603b\u662f\u6ee1\u8db3\u7684\u3002<\/span><\/p>\n

          \u53e6\u4e00\u4e2a\u9650\u5236\u662fELF\u4f1a\u4f7f\u7528\u57283.4\u8282\u4e2d\u63d0\u5230\u7684\u7b26\u53f7\u7248\u672c\u7cfb\u7edf\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0cElf_Rel.r_info\u57df\u4e0d\u4ec5\u7528\u4f5c\u52a8\u6001\u7b26\u53f7\u8868\u4e2d\u7684\u4e0b\u6807\uff0c\u4e5f\u7528\u4f5c\u7b26\u53f7\u7248\u672c\u8868(.gnu.version\u6bb5)\u4e2d\u7684\u4e0b\u6807\u3002\u901a\u5e38\u6765\u8bf4\uff0cLeakless\u80fd\u591f\u81ea\u52a8\u7684\u6ee1\u8db3\u8fd9\u4e9b\u9650\u5236\uff0c\u9664\u4e86x86-64\u4e2d\u4f7f\u7528huge pages\u7684\u5c0f\u578b\u4e8c\u8fdb\u5236\u7a0b\u5e8f [32]. \u6211\u4eec\u5728\u9644\u5f55A\u4e2d\u8be6\u8ff0\u4e86\u5173\u4e8e\u7b26\u53f7\u7248\u672c\u7684\u989d\u5916\u9650\u5236\u3002\u5f53\u8fd9\u4e9b\u9650\u5236\u4e0d\u80fd\u88ab\u6ee1\u8db3\u65f6\uff0c\u5fc5\u987b\u4f7f\u7528\u4e00\u4e2a\u66ff\u4ee3\u7684\u65b9\u6cd5\u3002\u8fd9\u5c31\u9700\u8981\u6d3b\u7528\u52a8\u6001\u88c5\u8f7d\u5668\uff0c\u901a\u8fc7\u7834\u574f\u5176\u5185\u90e8\u6570\u636e\u7ed3\u6784\u6765\u6539\u53d8\u52a8\u6001\u89e3\u6790\u7684\u8fc7\u7a0b\u3002<\/span><\/p>\n

          4.3 \u7834\u574f\u52a8\u6001\u88c5\u8f7d\u6570\u636e<\/strong><\/p>\n

          \u6211\u4eec\u56de\u60f3\u8d77_dl_runtime_resolve\u7684\u7b2c\u4e00\u4e2a\u53c2\u6570\u662f\u4e00\u4e2a\u6307\u5411link_map\u6570\u636e\u7c7b\u578b\u7684\u6307\u9488\u3002\u8fd9\u4e2a\u7ed3\u6784\u4f53\uff0c\u5305\u542b\u4e86ELF\u53ef\u6267\u884c\u6587\u4ef6\u7684\u4fe1\u606f\uff0c\u800c\u4e14\u8fd9\u4e9b\u5185\u5bb9\u4f1a\u88ab\u52a8\u6001\u88c5\u8f7d\u5668\u5b8c\u5168\u5730\u4fe1\u4efb\u3002\u6b64\u5916\uff0cLeakless\u53ef\u4ee5\u83b7\u5f97\u6709\u6f0f\u6d1e\u7a0b\u5e8f\u7684GOT\u8868\u7684\u7b2c\u4e8c\u4e2a\u6761\u76ee\uff0c\u5b83\u7684\u4f4d\u7f6e\u662f\u786e\u5b9a\u5df2\u77e5\u7684\u3002<\/span><\/p>\n

          \u56de\u60f33.5\u8282\u4e2dlink_map\u7684\u7ed3\u6784\uff0c\u5728l_info\u57df\u4e2d\uff0c\u5305\u542b\u7740.dynamic\u6bb5\u6240\u6709\u6761\u76ee\u6307\u9488\u6784\u6210\u7684\u4e00\u4e2a\u6570\u7ec4\u3002\u8fd9\u4e9b\u6307\u9488\u5c31\u662f\u52a8\u6001\u94fe\u63a5\u5668\u62ff\u6765\u5b9a\u4f4d\u7b26\u53f7\u89e3\u6790\u8fc7\u7a0b\u4e2d\u4f7f\u7528\u7684\u5bf9\u8c61\u7684\u3002\u5c31\u50cf\u56fe3\u4e2d\u663e\u793a\u7684\u90a3\u6837\uff0c\u901a\u8fc7\u8986\u76d6\u8fd9\u4e2a\u6570\u636e\u7ed3\u6784\u7684\u4e00\u90e8\u5206\uff0cLeakless\u80fd\u591f\u5c06l_info\u57df\u4e2d\u7684DT_STRTAB\u6761\u76ee\u6307\u5411\u4e00\u4e2a\u7279\u610f\u5236\u9020\u7684\u52a8\u6001\u6761\u76ee\uff0c\u90a3\u91cc\u6307\u5411\u4e00\u4e2a\u5047\u7684\u52a8\u6001\u5b57\u7b26\u4e32\u8868\u3002\u7ed3\u679c\uff0c\u653b\u51fb\u8005\u5c31\u53ef\u4ee5\u5c06\u653b\u51fb\u7b80\u5316\u4e3a4.1\u8282\u4e2d\u7684\u57fa\u7840\u60c5\u5f62\u4e86\u3002<\/span><\/p>\n

          \u8fd9\u4e2a\u6280\u672f\u8f83\u4e0a\u4e00\u8282\u4e2d\u7684\u6280\u672f\u800c\u8a00\u6709\u7740\u66f4\u52a0\u5e7f\u6cdb\u7684\u9002\u7528\u6027\uff0c\u56e0\u4e3a\u5b83\u6ca1\u6709\u7279\u5b9a\u7684\u9650\u5236\u3002\u7279\u522b\u7684\uff0c\u5b83\u5bf9\u4e8e\u4f7f\u7528huge pages\u7684\u5c0f\u578b64\u4f4dELF\u540c\u6837\u9002\u7528\u3002\u7136\u800c\uff0c\u76f8\u6bd4\u4e8e\u4e4b\u524d\u53ea\u4f9d\u8d56\u4e8e\u6807\u51c6ELF\u7684\u7279\u6027\u7684\u653b\u51fb\uff0c\u5728\u8fd9\u79cd\u60c5\u51b5(\u548c\u4e0b\u4e00\u8282\u8981\u53d9\u8ff0\u7684\u60c5\u51b5)\u4e0b\uff0c\u6211\u4eec\u9700\u8981\u5047\u8bbe\u7279\u5b9aglibc\u7684\u7ed3\u6784(link_map)\u5e03\u5c40\u662f\u5df2\u77e5\u7684\u3002\u6bcf\u4e2a\u52a8\u6001\u88c5\u8f7d\u5668\u6709\u5b83\u81ea\u5df1\u7684\u7ed3\u6784\u5b9e\u73b0\uff0c\u6545\u5f53\u9762\u5bf9\u4e0d\u540c\u7684\u52a8\u6001\u88c5\u8f7d\u5668\u65f6\u5c31\u9700\u8981\u505a\u4e00\u4e9b\u5c0f\u7684\u6539\u52a8\u3002\u9700\u8981\u6ce8\u610f\u7684\u662flink_map\u7684\u5e03\u5c40\u5728\u540c\u4e00\u79cd\u52a8\u6001\u88c5\u8f7d\u5668\u7684\u4e0d\u540c\u7248\u672c\u4e4b\u95f4\u4e5f\u53ef\u80fd\u4e0d\u540c\u3002\u7136\u800c\uff0c\u4ed6\u4eec\u663e\u5f97\u975e\u5e38\u7a33\u5b9a\uff0c\u5c24\u5176\u662fglibc\u4e2d\u7684\u76f8\u5173\u7ed3\u6784\u4ece2004\u5e74\u8d77\u5c31\u6ca1\u53d8\u8fc7\u3002<\/span><\/p>\n

          \"Figure3\"<\/a><\/p>\n

          Figure 3: 4.3\u8282\u4e2d\u653b\u51fb\u7684\u4f8b\u5b50\u3002\u653b\u51fb\u8005\u901a\u8fc7\u89e3\u5f15\u7528GOT\u7684\u7b2c\u4e8c\u9879\u6765\u53d6\u5f97link_map\u7ed3\u6784\u3002\u5728\u8fd9\u4e2a\u7ed3\u6784\u4e2d\u7834\u574f\u4fdd\u5b58DT_STRTAB\u6307\u9488\u7684l_info\u57df\u3002\u5b83\u7684\u503c\u88ab\u8bbe\u6210\u4e00\u4e2a\u4f2a\u9020\u7684\u52a8\u6001\u6761\u76ee\u7684\u5730\u5740\uff0c\u90a3\u91cc\u6307\u5411\u4e86\u4e00\u4e2a\u4f4d\u4e8e.bss\u6bb5\u4e2d\u7684\u5047\u7684\u52a8\u6001\u5b57\u7b26\u4e32\u8868\u3002<\/span><\/p>\n

          4.4 \u5b8c\u5168RELRO\u7684\u60c5\u5f62<\/strong><\/p>\n

          Leakless\u53ef\u4ee5\u7ed5\u8fc7\u5b8c\u5168RELRO\u7684\u4fdd\u62a4\u3002<\/span><\/p>\n

          \u5f53\u5b8c\u5168RELRO\u5e94\u7528\u65f6\uff0c\u6240\u6709\u7684\u91cd\u5b9a\u4f4d\u5c06\u5728\u52a0\u8f7d\u65f6\u5b8c\u6210\uff0c\u4e0d\u4f1a\u6709\u60f0\u6027\u89e3\u6790\u7684\u8fc7\u7a0b\uff0c\u5e76\u4e14link_map\u7ed3\u6784\u7684\u5730\u5740\u548c\u5728GOT\u4e2d\u7684_dl_runtime_resolve\u4e5f\u4e0d\u4f1a\u88ab\u521d\u59cb\u5316\u3002\u6240\u4ee5\uff0c\u50cf\u666e\u901a\u6280\u672f\u7ed5\u8fc7\u90e8\u5206RELRO\u90a3\u6837\u76f4\u63a5\u83b7\u5f97\u5b83\u4eec\u7684\u5730\u5740\u662f\u4e0d\u53ef\u80fd\u7684\u3002<\/span>\u7136\u800c\uff0c\u4ece\u52a8\u6001\u8868\u7684DT_DEBUG\u6761\u76ee\u4e2d\u95f4\u63a5\u6062\u590d\u8fd9\u4e24\u4e2a\u503c\u4ecd\u7136\u662f\u53ef\u80fd\u7684\u3002DT_DEBUG\u6761\u76ee\u7684\u503c\u662f\u52a8\u6001\u88c5\u8f7d\u5668\u5728\u52a0\u8f7d\u65f6\u8bbe\u7f6e\u597d\u7684\uff0c\u5b83\u6307\u5411\u4e00\u4e2ar_debug\u7c7b\u578b\u7684\u6570\u636e\u7ed3\u6784\u3002\u8fd9\u4e2a\u6570\u636e\u7ed3\u6784\u4fdd\u5b58\u7740\u8c03\u8bd5\u5668\u7528\u6765\u6807\u8bc6\u52a8\u6001\u88c5\u8f7d\u5668\u7684\u57fa\u5730\u5740\u5e76\u62e6\u622a\u76f8\u5e94\u4e8b\u4ef6\u9700\u8981\u7684\u4fe1\u606f\u3002\u6b64\u5916\uff0c\u8fd9\u4e2a\u7ed3\u6784\u7684r_map\u57df\u4fdd\u5b58\u7740\u4e00\u4e2a\u6307\u5411link_map\u94fe\u8868\u5934\u90e8\u7684\u6307\u9488\u3002<\/span><\/p>\n

          Leakless\u7834\u574f\u4e86\u8fd9\u4e2a\u94fe\u8868\u4e2d\u63cf\u8ff0ELF\u53ef\u6267\u884c\u6587\u4ef6\u7684\u7b2c\u4e00\u4e2a\u8282\u70b9\uff0c\u4f7f\u5f97\u7528\u4e8e\u4fdd\u5b58DT_STRTAB\u7684l_info\u6761\u76ee\u6307\u5411\u4e00\u4e2a\u5047\u7684\u52a8\u6001\u5b57\u7b26\u4e32\u8868\u7684\u6307\u9488\u3002\u5177\u4f53\u60c5\u5f62\u5982\u56fe4\u6240\u793a\u3002<\/span><\/p>\n

          \"Figure4\"<\/a><\/p>\n

          Figure 4: 4.4\u8282\u4e2d\u7684\u653b\u51fb\u56fe\u793a\u3002\u9634\u5f71\u80cc\u666f\u8868\u793a\u53ea\u8bfb\u7684\u5185\u5b58\uff0c\u767d\u8272\u7684\u80cc\u666f\u8868\u793a\u53ef\u5199\u7684\u5185\u5b58\uff0c\u7ea2\u8272\u4e0e\u52a0\u7c97\u7684\u90e8\u5206\u8868\u793a\u653b\u51fb\u8005\u4f2a\u9020\u7684\u6570\u636e\u3002\u653b\u51fb\u8005\u4f7f\u7528DT_DEBUG\u8fd9\u4e2a\u52a8\u6001\u6761\u76ee\u6765\u83b7\u53d6r_debug\u7ed3\u6784\uff0c\u63a5\u7740\uff0c\u89e3\u5f15\u7528r_map\u57df\u4ece\u800c\u5f97\u5230\u4e3b\u7a0b\u5e8f\u7684link_map\u7ed3\u6784\uff0c\u7136\u540e\u50cf\u7b2c3\u8282\u4e2d\u5c55\u793a\u7684\u90a3\u6837\u7834\u574fl_info[DT_STRTAB]\u3002<\/span><\/p>\n

          \u56e0\u4e3a\u5b8c\u5168RELRO\u7684\u7f18\u6545.got.plt\u662f\u53ea\u8bfb\u7684\uff0c\u653b\u51fb\u8005\u9700\u8981\u4f2a\u9020\u4e00\u4e2a\u91cd\u5b9a\u4f4d\u9879\u3002\u4e3a\u6b64\uff0c\u4ed6\u7834\u574fl_info[DT_JMPREL]\u4f7f\u5176\u6307\u5411\u4e00\u4e2a\u5047\u7684\u52a8\u6001\u6761\u76ee\uff0c\u800c\u8fd9\u4e2a\u52a8\u6001\u6761\u76ee\u5219\u6307\u5411\u4e00\u4e2a\u91cd\u5b9a\u4f4d\u9879\u3002\u8fd9\u4e2a\u91cd\u5b9a\u4f4d\u9879\u5f15\u7528\u4e86\u5df2\u7ecf\u5b58\u5728\u7684printf\u7b26\u53f7\uff0c\u4f46r_offset\u5219\u6307\u5411\u4e00\u5757\u53ef\u5199\u7684\u5185\u5b58\u533a\u57df\u3002<\/span><\/p>\n

          \u63a5\u7740\u653b\u51fb\u8005\u540c\u6837\u9700\u8981\u6062\u590d_dl_runtime_resolve\u51fd\u6570\u7684\u6307\u9488\uff0c\u56e0\u4e3a\u5b8c\u5168RELRO\u73b0\u5728\u5b83\u5728\u4e3b\u7a0b\u5e8f\u7684GOT\u4e2d\u5df2\u7ecf\u4e0d\u5b58\u5728\u4e86\uff0c\u6240\u4ee5\u4ed6\u89e3\u5f15\u7528l_info\u57df\u4e2d\u7684\u7b2c\u4e00\u4e2alink_map\u7ed3\u6784\u53d6\u5f97\u63cf\u8ff0\u7b2c\u4e00\u4e2a\u5171\u4eab\u5e93\u7684link_map\uff0c\u800c\u8fd9\u4e2a\u5171\u4eab\u5e93\u662f\u4e0d\u88ab\u5b8c\u5168RELRO\u4fdd\u62a4\u7684\u3002\u653b\u51fb\u8005\u901a\u8fc7l_info[DT_PLTGOT]\u57df\u6765\u5f97\u5230\u5bf9\u5e94\u7684\u52a8\u6001\u6761\u76ee(\u53f3\u4fa7\u7684.dynamic)\uff0c\u63a5\u7740\u662f.plt.got\u6bb5(\u603b\u662f\u5728\u53f3\u4fa7)\uff0c\u5176\u4e2d\u7684\u7b2c\u4e8c\u4e2a\u6761\u76ee\u91cc\u5c31\u6709_dl_runtime_resolve\u7684\u5730\u5740\u3002<\/span><\/p>\n

          \u5728\u8fd9\u4e4b\u540e\uff0cLeakless\u5fc5\u987b\u8c03\u7528_dl_runtime_resolve\uff0c\u5c06\u521a\u521a\u7834\u574f\u7684link_map\u7ed3\u6784\u4f5c\u4e3a\u7b2c\u4e00\u4e2a\u53c2\u6570\u4f20\u8fc7\u53bb\uff0c\u5e76\u5c06\u4e00\u4e2a\u65b0\u7684.dynsym\u504f\u79fb\u4f5c\u4e3a\u7b2c\u4e8c\u4e2a\u53c2\u6570\u4f20\u8fc7\u53bb\u3002\u7136\u800c\uff0c\u5c31\u50cf\u4e4b\u524d\u63d0\u5230\u7684\u90a3\u6837\uff0c_dl_runtime_resolve\u56e0\u4e3a\u5b8c\u5168RELRO\u7684\u7f18\u6545\u5728GOT\u4e2d\u5df2\u7ecf\u4e0d\u5b58\u5728\u4e86\u3002\u6240\u4ee5\uff0cLeakless\u5fc5\u987b\u5728\u53e6\u4e00\u4e2aELF\u5bf9\u8c61\u7684GOT\u8868\u4e2d\u627e\u5230\u5b83\u7684\u5730\u5740\uff0c\u6362\u53e5\u8bdd\u8bf4\uff0c\u5c31\u662f\u4e00\u4e2a\u88ab\u7a0b\u5e8f\u4f7f\u7528\u800c\u6ca1\u6709\u5b8c\u5168RELRO\u4fdd\u62a4\u7684\u5e93\u3002\u5728\u5927\u591a\u6570\u60c5\u51b5\u4e0b\uff0c\u53ea\u6709ELF\u53ef\u6267\u884c\u6587\u4ef6\u672c\u8eab\u662f\u88ab\u5b8c\u5168RELRO\u4fdd\u62a4\u7684\uff0c\u4f46\u5e93\u5e76\u4e0d\u4f1a\u3002\u8fd9\u662f\u56e0\u4e3aRELRO\u662f\u5728\u727a\u7272\u6027\u80fd\u7684\u524d\u63d0\u4e0b\uff0c\u7528\u6765\u52a0\u56fa\u4e00\u4e9b\u88ab\u8ba4\u4e3a\u6bd4\u8f83\u201c\u6709\u98ce\u9669\u201d\u7684\u7279\u5b9a\u5e94\u7528\u7a0b\u5e8f\u7684\u3002\u5728\u5171\u4eab\u5e93\u4e0a\u5e94\u7528\u5b8c\u5168RELRO\u5c06\u4f1a\u5f71\u54cd\u6240\u6709\u4f7f\u7528\u8fd9\u4e2a\u5e93\u5e94\u7528\u7a0b\u5e8f\u7684\u6027\u80fd\uff0c\u6240\u4ee5\u5e93\u6587\u4ef6\u4e00\u822c\u662f\u4e0d\u53d7\u4fdd\u62a4\u7684\u3002\u56e0\u4e3a\u5404\u4e2a\u5e93\u5728\u94fe\u8868\u4e0a\u7684\u987a\u5e8f\u662f\u786e\u5b9a\u7684\uff0cLeakless\u53ef\u4ee5\u89e3\u5f15\u7528link_map\u4e2d\u7684l_next\u9879\u6765\u5f97\u5230\u4e0d\u88ab\u5b8c\u5168RELRO\u4fdd\u62a4\u7684\u5e93\u6587\u4ef6\u7684link_map\uff0c\u89e3\u5f15\u7528\u5b83\u7684l_info\u9879\u5f97\u5230\u5bf9\u5e94\u7684DT_PLTGOT\u52a8\u6001\u6761\u76ee\u7684\u503c\uff0c\u518d\u89e3\u5f15\u7528\u5b83\u7684\u503c(\u5373\u8fd9\u4e2a\u5e93GOT\u7684\u57fa\u5730\u5740)\uff0c\u5c31\u53ef\u4ee5\u4eceGOT\u4e2d\u83b7\u5f97_dl_runtime_resolve\u7684\u5730\u5740\u4e86\u3002<\/span><\/p>\n

          Leakless\u63a5\u4e0b\u6765\u5fc5\u987b\u8981\u514b\u670d\u4ee5\u4e0b\u95ee\u9898: _dl_runtime_resolve\u4e0d\u4ec5\u4ec5\u4f1a\u8c03\u7528\u76ee\u6807\u51fd\u6570\uff0c\u8fd8\u4f1a\u5c1d\u8bd5\u5c06\u5b83\u7684\u5730\u5740\u5199\u5230\u6b63\u786e\u7684GOT\u9879\u4e2d\u3002\u5982\u679c\u8fd9\u4ef6\u4e8b\u53d1\u751f\uff0c\u7a0b\u5e8f\u5c31\u4f1a\u5d29\u6e83\uff0c\u56e0\u4e3a\u5b8c\u5168RELRO\u4fdd\u62a4\u4e0bGOT\u662f\u4e0d\u53ef\u5199\u7684\u3002\u6211\u4eec\u53ef\u4ee5\u901a\u8fc7\u4f2a\u9020link_map\u4e2d\u7684DT_JMPREL\u52a8\u6001\u6761\u76ee\u6765\u7ed5\u8fc7\u8fd9\u4e2a\u95ee\u9898\u3002\u539f\u672cDT_JMPREL\u6307\u5411.rel.dyn\u6bb5\uff0cLeakless\u5c06\u5176\u6307\u5411\u653b\u51fb\u8005\u63a7\u5236\u7684\u4e00\u5757\u5185\u5b58\u533a\u57df\uff0c\u90a3\u91cc\u5199\u6709\u4e00\u4e2aElf_Rel\u7ed3\u6784\uff0c\u4e14\u5176r_offset\u57df\u6307\u5411\u4e00\u5757\u53ef\u5199\u7684\u5185\u5b58\u533a\u57df\uff0c\u5176r_info\u6307\u5411\u6211\u4eec\u7684\u76ee\u6807\u7b26\u53f7\u3002\u6240\u4ee5\uff0c\u5f53\u4e00\u4e2a\u5e93\u88ab\u89e3\u6790\u7684\u65f6\u5019\uff0c\u5b83\u7684\u5730\u5740\u5c06\u4f1a\u88ab\u5199\u5230\u4e00\u4e2a\u53ef\u5199\u7684\u4f4d\u7f6e\uff0c\u7a0b\u5e8f\u5c31\u4e0d\u4f1a\u5d29\u6e83\u4e86\uff0c\u800c\u4e14\u8bf7\u6c42\u7684\u51fd\u6570\u4e5f\u5c06\u4f1a\u88ab\u6267\u884c\u3002<\/span><\/p>\n

          ========================================================================<\/span><\/p>\n

            \n
          1. \u5b9e\u73b0<\/strong><\/li>\n<\/ol>\n

            Leakless\u5c06\u4f1a\u5206\u6790\u4e8c\u8fdb\u5236\u6587\u4ef6\u4ee5\u786e\u5b9a\u5b83\u7684\u6280\u672f\u662f\u5426\u9002\u7528\uff0c\u63a5\u7740\u5236\u9020\u5fc5\u8981\u7684\u6570\u636e\uff0c\u7136\u540e\u751f\u6210\u4e00\u6bb5ROP\u94fe\u6765\u5b9e\u73b0\u6240\u9009\u6280\u672f\u3002\u81f3\u4e8e\u53d1\u73b0\u6700\u521d\u59cb\u7684\u6f0f\u6d1e\u4ee5\u53ca\u81ea\u52a8\u63d0\u53d6\u6709\u7528\u7684gadgets\u90a3\u5e76\u975e\u6211\u4eec\u7684\u5de5\u4f5c\uff0c\u5b83\u4eec\u5df2\u7ecf\u5728\u5f88\u591a\u8457\u4f5c\u4e2d\u88ab\u5f88\u597d\u5730\u7814\u7a76\u548c\u5b9e\u73b0\u8fc7\u4e86 [6,16,19,20,34,38].\u6211\u4eec\u5c06Leakless\u8bbe\u8ba1\u6210\u4e0e\u591a\u79cdgadget\u53d1\u73b0\u6280\u672f\u517c\u5bb9\uff0c\u5e76\u5b9e\u73b0\u4e86\u4e00\u4e2a\u624b\u52a8\u7684\u540e\u7aef(\u7528\u6237\u53ef\u4ee5\u7ed9\u7a0b\u5e8f\u63d0\u4f9bgadgets)\uff0c\u53e6\u5916\u8fd8\u6709\u4e00\u4e2a\u4f7f\u7528ROPC [22] \u7684\u540e\u7aef\u3002ROPC\u662f\u4e00\u4e2a\u4ee5Q [34] \u63d0\u51fa\u7684\u65b9\u6cd5\u4e3a\u57fa\u7840\u5b9e\u73b0\u7684\u4e00\u4e2a\u81ea\u52a8\u5316ROP\u7f16\u8bd1\u5668\u7684\u539f\u578b\u3002<\/span><\/p>\n

            \u6211\u4eec\u8fd8\u5f00\u53d1\u4e86\u4e00\u4e2a\u5c0f\u578b\u7684\u6d4b\u8bd5\u5957\u4ef6\uff0c\u7531\u4e00\u4e2a\u5177\u6709\u57fa\u4e8e\u6808\u7684\u7f13\u51b2\u533a\u6ea2\u51fa\u7684C\u7a0b\u5e8f\u7ec4\u6210\uff0c\u540c\u65f6\u63d0\u4f9b\u65e0\u4fdd\u62a4\uff0c\u90e8\u5206RELRO\u548c\u5b8c\u5168RELRO\u7684\u7248\u672c\u3002\u8fd9\u4e2a\u6d4b\u8bd5\u5957\u4ef6\u53ef\u4ee5\u5728x86, x86-64, arm\u67b6\u6784\u7684GNU\/Linux\u7cfb\u7edf\u548cx86-64\u67b6\u6784\u7684FreeBSD\u7cfb\u7edf\u4e0a\u8fd0\u884c\u3002<\/span><\/p>\n

            5.1 \u9700\u8981\u7684Gadgets<\/span><\/p>\n

            Leakless\u5305\u542b\u4e864\u79cd\u7528\u4e8e\u4e0d\u540c\u52a0\u56fa\u63aa\u65bd\u7684\u5229\u7528\u6280\u672f\u3002\u5e94\u7528\u8fd9\u4e9b\u4e0d\u540c\u7684\u6280\u672f\u9700\u8981\u63d0\u4f9b\u4e0d\u540c\u7684gadgets\u3002\u88682\u662f\u5bf9\u8fd9\u4e9bgadgets\u7c7b\u578b\u7684\u4e00\u4e2a\u603b\u7ed3\u3002write_memory gadget\u4e3b\u8981\u7528\u4e8e\u5728\u5df2\u77e5\u5730\u5740\u4f2a\u9020\u6570\u636e\u7ed3\u6784\uff0cderef_write gadget\u7528\u4e8e\u904d\u5386\u548c\u7834\u574f\u6570\u636e\u7ed3\u6784(\u5c24\u5176\u662flink_map).deref_save\u548ccopy_to_stack gadgets\u662f\u7528\u5728\u5b8c\u5168RELRO\u7684\u60c5\u51b5\u4e2d\u7684\u3002\u524d\u8005\u7684\u76ee\u7684\u662f\u5c06link_map\u548c_dl_runtime_resolve\u7684\u5730\u5740\u4fdd\u5b58\u5728\u4e00\u4e2a\u5df2\u77e5\u4f4d\u7f6e\uff0c\u800c\u540e\u8005\u7684\u5219\u662f\u7528\u6765\u5c06link_map\u548c\u91cd\u5b9a\u4f4d\u9879\u7684\u4e0b\u6807\u653e\u5230\u6808\u4e0a\u7136\u540e\u8c03\u7528_dl_runtime_resolve\uff0c\u56e0\u4e3a\u4f7f\u7528PLT0\u5df2\u7ecf\u4e0d\u53ef\u884c\u3002<\/span><\/p>\n

            \"Table2\"<\/a><\/p>\n

            Table 2: \u591a\u79cd\u65b9\u6cd5\u9700\u8981\u7684Gadgets\u3002”Signature”\u5217\u4ee3\u8868gadget\u7684\u540d\u5b57\u548c\u5b83\u63a5\u53d7\u7684\u53c2\u6570\uff0c”Implementation”\u4ee3\u8868gadget\u884c\u4e3a\u7684\u7c7bC\u4f2a\u4ee3\u7801\u3002\u6700\u540e\u56db\u5217\u6307\u793a\u4e86\u67d0\u4e2agadget\u662f\u5426\u5728\u7b2c4\u8282\u91cc\u5bf9\u5e94\u7684\u65b9\u6cd5\u4e2d\u9700\u8981\u3002”N”\u8868\u793a\u6ca1\u6709RELRO\uff0c”P”\u8868\u793a\u90e8\u5206RELRO\uff0c”H”\u8868\u793a\u90e8\u5206RELRO\u4e14\u4e3a\u4f7f\u7528huge pages\u7684\u5c0f\u578b64\u4f4d\u7a0b\u5e8f\uff0c”F”\u5219\u8868\u793a\u5b8c\u5168RELRO\u3002<\/span><\/p>\n

            \u5bf9\u4e8e\u611f\u5174\u8da3\u7684\u8bfb\u8005\uff0c\u6211\u4eec\u63d0\u4f9b\u4e86Leakless\u5728\u4e24\u7ec4\u4e0d\u540c\u7684\u7f13\u89e3\u6280\u672f\u4fdd\u62a4\u4e0b\u8fdb\u884c\u5229\u7528\u7684\u6df1\u5ea6\u6837\u4f8b\uff0c\u653e\u5728Leakless\u4ee3\u7801\u5e93\u7684\u6587\u6863\u4e2d [17].<\/span><\/p>\n

            ========================================================================<\/span><\/p>\n

            6 \u8bc4\u4f30<\/strong><\/p>\n

            \u6211\u4eec\u4f7f\u75284\u79cd\u65b9\u6cd5\u5bf9Leakless\u8fdb\u884c\u4e86\u8bc4\u4f30\u3002\u9996\u5148\u6211\u4eec\u786e\u5b9a\u4e86\u6211\u4eec\u7684\u6280\u672f\u5bf9\u4e8e\u4e0d\u540c\u52a8\u6001\u88c5\u8f7d\u5668\u5b9e\u73b0\u7684\u9002\u7528\u6027\u3002\u63a5\u7740\u5206\u6790\u4e86\u591a\u4e2a\u6d41\u884c\u7684GNU\/Linux\u4ee5\u53caBSD\u7684\u53d1\u884c\u7248(Ubuntu, Debian, Fedora\u548cFreeBSD)\u4e2d\u7684\u4e8c\u8fdb\u5236\u6587\u4ef6\uff0c\u4ece\u800c\u786e\u5b9a\u6613\u53d7\u6211\u4eec\u653b\u51fb\u5f71\u54cd\u7684\u4e8c\u8fdb\u5236\u6587\u4ef6\u6240\u5360\u7684\u6bd4\u7387\u3002\u7136\u540e\u6211\u4eec\u5c06Leakless\u5e94\u7528\u5728\u5bf9\u771f\u5b9e\u4e16\u754c\u4e2dWireshark\u7684\u4e00\u4e2a\u6709\u6f0f\u6d1e\u7248\u672c\u7684\u5229\u7528\u4e2d\uff0c\u4ee5\u53ca\u4e00\u4e2a\u9488\u5bf9Pidgin\u7684\u66f4\u52a0\u590d\u6742\u7684\u653b\u51fb\u4e2d\u3002\u6700\u540e\u6211\u4eec\u4f7f\u7528\u4e00\u4e2a\u56fe\u7075\u5b8c\u5168\u7684ROP\u7f16\u8bd1\u5668\u6765\u5b9e\u73b0Leakless\u7684\u65b9\u6cd5\u548c\u4e24\u4e2a\u4ee5\u524d\u4f7f\u7528\u7684\u6280\u672f\uff0c\u5e76\u6bd4\u8f83\u4ed6\u4eec\u751f\u6210\u51fa\u7684\u94fe\u7684\u5927\u5c0f\u3002<\/span><\/p>\n

            6.1 \u52a8\u6001\u88c5\u8f7d\u5668<\/strong><\/p>\n

            \u4e3a\u4e86\u5c55\u793aLeakless\u7684\u666e\u9002\u6027\uff0c\u5c24\u5176\u662f\u9488\u5bf9\u4e0d\u540c\u7684\u57fa\u4e8eELF\u7684\u5e73\u53f0\uff0c\u6211\u4eec\u8c03\u67e5\u4e86\u51e0\u79cd\u52a8\u6001\u88c5\u8f7d\u5668\u7684\u5b9e\u73b0\u3002\u7279\u522b\u5730\uff0c\u6211\u4eec\u53d1\u73b0GNU C\u6807\u51c6\u5e93(\u4e5f\u5c31\u662f\u5728GUN\/Linux\u53d1\u884c\u7248\u4e2d\u5e7f\u6cdb\u4f7f\u7528\u7684glibc)\u7684\u52a8\u6001\u88c5\u8f7d\u90e8\u5206\uff0c\u5176\u4ed6\u4e00\u4e9bLinux\u5b9e\u73b0\u4f8b\u5982dietlibc, uClibc\u548cnewlib(\u5728\u5d4c\u5165\u5f0f\u7cfb\u7edf\u4e2d\u5e7f\u6cdb\u4f7f\u7528)\uff0c\u4ee5\u53caOpenBSD\u548cNetBSD\u7684\u5b9e\u73b0\u90fd\u542b\u6709\u53ef\u4ee5\u88abLeakless\u5229\u7528\u7684\u6f0f\u6d1e\u3002\u53e6\u4e00\u79cd\u5d4c\u5165\u5f0f\u5e93\uff0cmusl\uff0c\u5219\u4e0d\u4f1a\u53d7\u5230\u6211\u4eec\u65b9\u6cd5\u7684\u5f71\u54cd\u56e0\u4e3a\u5b83\u4e0d\u652f\u6301\u60f0\u6027\u88c5\u8f7d\u3002Bionic\uff0cAndroid\u4e2d\u4f7f\u7528\u7684C\u6807\u51c6\u5e93\uff0c\u540c\u6837\u4e0d\u53ef\u5229\u7528\u56e0\u4e3a\u5b83\u53ea\u652f\u6301PIE\u7684\u4e8c\u8fdb\u5236\u6587\u4ef6\u3002\u6700\u6709\u8da3\u7684\u4f8b\u5b50\uff0c\u4e0d\u540c\u4e8e\u6240\u6709\u6211\u4eec\u5206\u6790\u7684\u88c5\u8f7d\u5668\uff0c\u662fFreeBSD\u7684\u5b9e\u73b0\u3002\u5b9e\u9645\u4e0a\uff0c\u5b83\u662f\u552f\u4e00\u4e00\u4e2a\u4f1a\u5bf9\u4f20\u8fdb_dl_runtime_resolve\u7684\u53c2\u6570\u8fdb\u884c\u8fb9\u754c\u68c0\u67e5\u7684\u3002\u6240\u6709\u5176\u4ed6\u7684\u88c5\u8f7d\u5668\u5b8c\u5168\u4fe1\u4efb\u4f20\u5165\u7684\u53c2\u6570\u3002\u4e0d\u4ec5\u5982\u6b64\uff0c\u6240\u6709\u88ab\u5206\u6790\u7684\u88c5\u8f7d\u5668\u90fd\u5b8c\u5168\u5730\u4fe1\u4efb\u63a7\u5236\u7ed3\u6784\uff0c\u800cLeakless\u4f1a\u5728\u591a\u6570\u653b\u51fb\u4e2d\u7834\u574f\u8fd9\u4e2a\u7ed3\u6784\u3002<\/span><\/p>\n

            \u603b\u7ed3\u6765\u8bf4\uff0c\u5728\u6211\u4eec\u5206\u6790\u7684\u88c5\u8f7d\u5668\u4e2d\uff0c\u53ea\u67092\u4e2a\u5728\u8bbe\u8ba1\u4e0a\u5bf9Leakless\u662f\u514d\u75ab\u7684: musl, \u5b83\u4e0d\u652f\u6301\u60f0\u6027\u7b26\u53f7\u89e3\u6790; \u4ee5\u53cabionic, \u5b83\u53ea\u652f\u6301PIE\u53ef\u6267\u884c\u6587\u4ef6\u3002\u6b64\u5916\uff0c\u56e0\u4e3aFreeBSD\u7684\u52a8\u6001\u88c5\u8f7d\u5668\u4f1a\u8fdb\u884c\u8fb9\u754c\u68c0\u67e5\uff0c4.2\u8282\u4e2d\u7684\u6280\u672f\u5df2\u7ecf\u4e0d\u9002\u7528\u4e86\u3002\u4e0d\u8fc7\u5176\u4ed6\u7684\u6280\u672f\u8fd8\u662f\u53ef\u4ee5\u8d77\u6548\u3002<\/p>\n

            6.2 \u64cd\u4f5c\u7cfb\u7edf\u8c03\u7814<\/strong><\/p>\n

            \u4e3a\u4e86\u80fd\u660e\u767dLeakless\u5bf9\u771f\u5b9e\u4e16\u754c\u7684\u64cd\u4f5c\u7cfb\u7edf\u7684\u5f71\u54cd\uff0c\u6211\u4eec\u5bf9\u51e0\u4e2aLinux\u548cBSD\u53d1\u884c\u7248\u4e2d\u9ed8\u8ba4\u5b89\u88c5\u7684\u4e8c\u8fdb\u5236\u7a0b\u5e8f\u8fdb\u884c\u4e86\u4e00\u6b21\u8c03\u7814\u3002\u7279\u522b\u5730\uff0c\u6211\u4eec\u68c0\u67e5\u4e86\u6240\u6709\u5728\/sbin,\/bin,\/usr\/bin\u548c\/usr\/bin\u76ee\u5f55\u4e0b\u7684\u7a0b\u5e8f\uff0c\u5e76\u5c06\u5b83\u4eec\u6309\u7167Leakless\u6280\u672f\u7684\u9002\u7528\u6027\u8fdb\u884c\u5206\u7c7b\u3002\u6211\u4eec\u8003\u8651\u7684\u53d1\u884c\u7248\u6709Ubuntu 14.10, Debian Wheezy, Fedora 20, \u548cFreeBSD 10\u3002\u6211\u4eec\u540c\u65f6\u4f7f\u7528\u4e86\u8fd9\u4e9b\u7cfb\u7edf\u7684x86\u548cx86-64\u7684\u7248\u672c\u3002\u5728Ubuntu\u548cDebian\u4e0a\uff0c\u6211\u4eec\u53e6\u5916\u5b89\u88c5\u4e86LAMP(Linux, Apache, MySQL, PHP)\u6808\u4f5c\u4e3a\u6a21\u62df\u4e00\u4e2a\u5178\u578b\u670d\u52a1\u5668\u90e8\u7f72\u3001\u914d\u7f6e\u7684\u5c1d\u8bd5\u3002<\/span><\/p>\n

            \u6211\u4eec\u5c06\u7a0b\u5e8f\u5206\u4e3a\u4e86\u4ee5\u4e0b5\u7c7b\uff1a<\/span><\/p>\n

            [\u672a\u4fdd\u62a4] \u6b64\u7c7b\u5305\u62ec\u6ca1\u6709\u542f\u7528RELRO\u6216PIE\u7684\u7a0b\u5e8f\u3002\u5bf9\u4e8e\u8fd9\u4e9b\u7a0b\u5e8f\uff0cLeakless\u53ef\u4ee5\u5e94\u7528\u57284.1\u8282\u4e2d\u4ecb\u7ecd\u7684\u57fa\u7840\u6280\u672f\u3002<\/span><\/p>\n

            [\u90e8\u5206RELRO] \u5f00\u542f\u4e86\u90e8\u5206RELRO\u7684\u7a0b\u5e8f\uff0c\u4f46\u662f\u6ca1\u6709\u5f00\u542fPIE\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0cLeakless\u53ef\u4ee5\u5e94\u75284.2\u8282\u4e2d\u4ecb\u7ecd\u7684\u6280\u672f\u3002<\/span><\/p>\n

            [\u90e8\u5206RELRO(huge pages)] \u5f00\u542f\u4e86\u90e8\u5206RELRO\uff0c\u4e14\u4f7f\u7528huge pages\u7684\u5c0f\u578b\u7a0b\u5e8f\uff0c\u5b83\u4eec\u9700\u8981Leakless\u4f7f\u75284.3\u8282\u4ecb\u7ecd\u7684\u6280\u672f\u3002<\/span><\/p>\n

            [\u5b8c\u5168RELRO] \u5f00\u542f\u4e86\u5b8c\u5168RELRO\u7684\u7a0b\u5e8f\uff0cLeakless\u9700\u8981\u4f7f\u75284.4\u8282\u5c55\u793a\u7684\u6280\u672f\u3002<\/span><\/p>\n

            [\u4e0d\u53d7\u5f71\u54cd] \u6700\u540e\u662f\u4f7f\u7528PIE\u7684\u7a0b\u5e8f\uff0c\u5b83\u4eec\u4e0d\u53d7Leakless\u7684\u5f71\u54cd(\u66f4\u591a\u7684\u8ba8\u8bba\u5c06\u57287.2\u4e2d\u8fdb\u884c)<\/span><\/p>\n

            \u8fd9\u9879\u8c03\u7814\u7684\u7ed3\u679c\u5728\u8fdb\u884c\u5f52\u4e00\u5316\u540e\uff0c\u5982\u56fe5\u6240\u793a\u3002\u6211\u4eec\u80fd\u591f\u786e\u5b9a\uff0c\u5728Ubuntu\u4e2d\uff0c84%\u7684\u7a0b\u5e8f\u53d7\u5230\u81f3\u5c11\u4e00\u9879\u6280\u672f\u7684\u5f71\u54cd\uff0c\u53e6\u670916%\u88abPIE\u6280\u672f\u4fdd\u62a4\u3002\u5728Debian\u4e2d\uff0cLeakless\u53ef\u4ee5\u5e94\u7528\u572886%\u7684\u7a0b\u5e8f\u4e2d\u3002Fedora\u5219\u542b\u670976%\u7684\u6613\u53d7\u5f71\u54cd\u7a0b\u5e8f\u3002\u6709\u8da3\u7684\u662f\uff0cFreeBSD\u6ca1\u6709\u7a0b\u5e8f\u5f00\u542fRELRO\u548cPIE\uff0c\u6240\u4ee5100%\u7684\u7a0b\u5e8f\u90fd\u4f1a\u53d7\u5230Leakless\u5f71\u54cd\u3002<\/span><\/p>\n

            \u53e6\u5916\uff0c\u6211\u4eec\u8fd8\u9488\u5bf9\u8fd9\u4e9b\u7cfb\u7edf\u4e2d\u7684\u5171\u4eab\u5e93\u8fdb\u884c\u4e86\u4e00\u6b21\u8c03\u7814\u3002\u6211\u4eec\u53d1\u73b0\uff0c\u5e73\u5747\u6765\u8bf4\uff0c\u53ea\u670911%\u7684\u5e93\u542f\u7528\u4e86\u5b8c\u5168RELRO\u7684\u4fdd\u62a4\u3002\u8fd9\u5bf9Leakless\u6765\u8bf4\u662f\u4e2a\u597d\u6d88\u606f: \u5bf9\u4e8e\u4e00\u4e2a\u7ed9\u5b9a\u7684\u7a0b\u5e8f\uff0c\u80fd\u591f\u627e\u5230\u52a0\u8f7d\u7684\u6ca1\u6709\u5b8c\u5168RELRO\u4fdd\u62a4\u7684\u5e93\u7684\u6982\u7387\u6781\u5176\u5730\u9ad8\uff0c\u5e76\u4e14\u5373\u4f7f\u4e00\u4e2a\u6f0f\u6d1e\u7a0b\u5e8f\u4f7f\u7528\u4e86RELRO\uff0cLeakless\u53ef\u4ee5\u5e94\u7528\u5b83\u7684\u5b8c\u5168RELRO\u653b\u51fb\u6765\u7ed5\u8fc7\u3002\u8fd9\u6837\u4e00\u6765\uff0cRELRO\u4f5c\u4e3a\u4e00\u9879\u7f13\u89e3\u63aa\u65bd\u7684\u4f5c\u7528\u57fa\u672c\u5df2\u7ecf\u5fae\u4e4e\u5176\u5fae\uff0c\u9664\u975e\u5b83\u5728\u7cfb\u7edf\u4e2d\u5927\u8303\u56f4\u4f7f\u7528\u3002<\/span><\/p>\n

            \"Figure5\"<\/a><\/p>\n

            Figure 5: \u76ee\u6807\u53d1\u884c\u7248\u4e2d\u9ed8\u8ba4\u5b89\u88c5\u7a0b\u5e8f\u7684\u5206\u7c7b\u3002\u88ab\u6807\u8bc6\u4e3a\u672a\u4fdd\u62a4\uff0c\u90e8\u5206RELRO\uff0c\u90e8\u5206RELRO HP\u548c\u5b8c\u5168RELRO\u5206\u522b\u9700\u8981\u5e94\u75284.1, 4.2, 4.3, 4.4\u8282\u4e2d\u7684\u653b\u51fb\u6280\u672f\u3002\u800c\u5bf9\u4e8e\u4e0d\u53d7\u5f71\u54cd\u7684\u7a0b\u5e8f\uff0cLeakless\u7684\u65b9\u6cd5\u4e0d\u9002\u7528\u3002<\/span><\/p>\n

            6.3 \u6848\u4f8b\u7814\u7a76: Wireshark<\/strong><\/p>\n

            \u6211\u4eec\u8fdb\u884c\u4e86\u4e00\u9879\u5c06Leakless\u5e94\u7528\u5728\u4e00\u4e2a\u4e0d\u4f1a\u4e0e\u653b\u51fb\u8005\u6709\u76f4\u63a5\u8054\u7cfb\u7684\u7a0b\u5e8f\u4e0a\u7684\u6848\u4f8b\u7814\u7a76\u3002\u6362\u53e5\u8bdd\u8bf4\uff0c\u5229\u7528\u5fc5\u987b\u4e00\u51fb\u5b8c\u6210\uff0c\u5e76\u4e14\u6ca1\u6709\u5730\u5740\u5e03\u5c40\u4fe1\u606f\u4ee5\u53ca\u5e93\u7684\u5185\u5bb9\u4fe1\u606f\u3002<\/p>\n

            \u6211\u4eec\u9009\u62e9\u4e86\u4e00\u4e2a\u8fd1\u671f(2014\u5e744\u6708)\u7684\u6f0f\u6d1e [7]\uff0c\u4e00\u4e2a\u5728Wireshark 1.8.0\u52301.8.13\u4ee5\u53ca1.10.0\u52301.10.6\u4e2dMPEG\u534f\u8bae\u89e3\u6790\u5668\u7684\u6808\u7f13\u51b2\u533a\u6ea2\u51fa\u6f0f\u6d1e\u3002\u6211\u4eec\u5728\u7528\u90e8\u5206RELRO\u4e0e\u5b8c\u5168RELRO\u7f16\u8bd1\u7684Wireshark 1.8.2\u4e0a\u8fdb\u884c\u8fd9\u9879\u5b9e\u9a8c\u3002\u4e8c\u8005\u90fd\u662f\u5728x86-64\u7684Debian Wheezy\u7cfb\u7edf\u4e0a\u7f16\u8bd1\uff0c\u4f7f\u7528GNU C\u8bed\u8a00\u5e93\uff0c\u5e76\u4e14\u6ca1\u6709\u5176\u5b83\u7c7b\u4f3cPIE\u548cstack canaries\u7684\u9632\u62a4\u3002<\/span><\/p>\n

            \u6211\u4eec\u4f7f\u7528Leakless\u7684\u624b\u52a8\u540e\u7aef\u6765\u786e\u5b9a\u9700\u8981\u7684gadgets\u4ee5\u6784\u5efa4\u79cd\u5fc5\u8981\u7684\u539f\u59cb\u529f\u80fd(\u57285.1\u8282\u4e2d\u63cf\u8ff0): write_memory, deref_write, deref_save \u548c copy_to_stack. \u5728Wireshark\u7684\u4f8b\u5b50\u4e2d\uff0c\u627e\u5230\u80fd\u591f\u6ee1\u8db3\u8fd9\u4e9b\u539f\u59cb\u529f\u80fd\u7684gadgets\u662f\u975e\u5e38\u5bb9\u6613\u7684\u3002<\/span><\/p>\n

            Leakless\u80fd\u591f\u4f7f\u75284.2\u8282\u548c4.4\u8282\u7684\u6280\u672f\u6784\u5efa\u4e00\u4e2a\u4e00\u51fb\u5b8c\u6210(one-shot)\u7684\u5229\u7528\u3002\u5728\u4e24\u79cd\u60c5\u51b5\u4e0b\uff0c\u5b83\u90fd\u80fd\u591f\u4f7f\u52a8\u6001\u88c5\u8f7d\u5668\u8c03\u7528glibc\u4e2d\u7684execve\u51fd\u6570\u6765\u542f\u52a8\u4e00\u4e2a\u6211\u4eec\u9009\u62e9\u7684\u7a0b\u5e8f\u3002<\/span><\/p>\n

            6.4 \u6848\u4f8b\u7814\u7a76: Pidgin<\/strong><\/p>\n

            \u6211\u4eec\u540c\u6837\u5c06Leakless\u5e94\u7528\u5728Pidgin\u4e0a\u6765\u5b9e\u884c\u66f4\u52a0\u590d\u6742\u7684\u5229\u7528\uff0c\u8fd9\u662f\u4e00\u4e2a\u6d41\u884c\u7684\u591a\u534f\u8bae\u5373\u65f6\u6d88\u606f\u5ba2\u6237\u7aef\u3002\u800c\u4e14\uff0c\u6211\u4eec\u60f3\u5728\u4e0d\u8fdb\u884c\u4efb\u4f55\u5f02\u5e38\u7cfb\u7edf\u8c03\u7528(\u4f8b\u5982 execve(“\/bin\/sh”)\uff0c\u8fd9\u53ef\u80fd\u89e6\u53d1\u5165\u4fb5\u68c0\u6d4b\u7cfb\u7edf\u62a5\u8b66)\u7684\u60c5\u51b5\u4e0b\u8fdb\u884c\u4e00\u6b21\u6076\u610f\u64cd\u4f5c\u3002\u6211\u4eec\u4f7f\u7528\u4e86x86\u67b6\u6784\u4e0b\u5f00\u542fRELRO\u7f16\u8bd1\u7684Pidgin 2.10.7\u7248\u672c\u3002<\/span><\/p>\n

            \u4e3a\u4e86\u8fbe\u5230\u8fd9\u4e2a\u76ee\u7684\uff0c\u6211\u4eec\u8fdb\u884c\u4e86\u4e00\u4e2a\u7279\u6b8a\u8bbe\u8ba1\u7684\u5229\u7528\uff0c\u4f7f\u5176\u5047\u88c5\u81ea\u5df1\u8fdb\u5165\u5e94\u7528\u903b\u8f91\u91cc\u5408\u6cd5\u7684\u51fd\u6570\u4e2d: \u901a\u8fc7\u4e00\u4e2a\u4ee3\u7406\u6253\u5f00\u96a7\u9053\u8fde\u63a5\u3002\u8fd9\u79cd\u653b\u51fb\u7684\u601d\u60f3\u662f\u4e00\u4e2a\u5373\u65f6\u901a\u8baf\u670d\u52a1\u7684\u63d0\u4f9b\u8005\u5229\u7528\u50cfCVE-2013-6487 [14] \u8fd9\u6837\u7684\u6f0f\u6d1e\u6765\u83b7\u5f97\u4ee3\u7801\u6267\u884c\uff0c\u5e76\u4e14\u4f7f\u7528Pidgin\u7684\u5168\u5c40\u4ee3\u7406\u8bbe\u7f6e\uff0c\u5c06\u6240\u6709\u7684\u5373\u65f6\u901a\u8baf\u6d41\u91cf\u91cd\u5b9a\u5411\u5230\u4e00\u4e2a\u7b2c\u4e09\u65b9\u7684\u670d\u52a1\u5668\u4e0a\uff0c\u4ece\u800c\u9020\u6210\u804a\u5929\u7a83\u542c\u3002<\/span><\/p>\n

            \u4e00\u65e6\u6211\u4eec\u786e\u5b9a\u4e86\u5fc5\u8981\u7684gadgets\u6765\u4f7f\u7528Leakless\u5bf9\u6297\u5b8c\u5168RELRO\u4fdd\u62a4\uff0c\u8c03\u7528libpurple.so(\u5e94\u7528\u7a0b\u5e8f\u6838\u5fc3\u903b\u8f91\u6240\u5728)\u4e2d\u7684\u51fd\u6570\u5c31\u975e\u5e38\u5bb9\u6613\u4e86\uff0c\u63a5\u7740\u8fdb\u884c\u4e0b\u9762\u5217\u88682\u4e2d\u7684C\u4ee3\u7801\u7684\u7b49\u4ef7\u64cd\u4f5c<\/span><\/p>\n

            \"Listing2\"<\/a><\/p>\n

            Listing 2: Pidgin\u653b\u51fb<\/span><\/p>\n

            \u6709\u8da3\u7684\u662f\uff0c\u6709\u4e9b\u5e93\u63d0\u4f9b\u7684\u51fd\u6570\u6ca1\u6709\u88ab\u5bfc\u5165\u5230Pidgin\u7a0b\u5e8f\u4e2d\uff0c\u8fd9\u6837\u5728\u6ca1\u6709Leakless\u7684\u60c5\u51b5\u4e0b\u4ec5\u4f7f\u7528\u4e00\u4e2a\u9636\u6bb5\u7684\u8f7d\u8377\u5b8c\u6210\u653b\u51fb\u5c06\u975e\u5e38\u5177\u6709\u6311\u6218\u6027\u3002<\/span><\/p>\n

            6.5 ROP\u94fe\u7684\u957f\u5ea6\u6bd4\u8f83<\/strong><\/p>\n

            \u4e3a\u4e86\u8bc1\u660eLeakless\u65b9\u6cd5\u7684\u6548\u7387\uff0c\u6211\u4eec\u5c06\u5176\u4e0e\u73b0\u6709\u7684\u5141\u8bb8\u653b\u51fb\u8005\u8c03\u7528\u4efb\u610f\u5e93\u51fd\u6570\u7684\u4e24\u9879\u6280\u672f\u8fdb\u884c\u4e86\u6bd4\u8f83\u3002\u7b2c\u4e00\u9879\u6280\u672f\u9996\u5148\u4ece.plt.got\u6bb5\u5411\u540e\u626b\u63cf\u5e93\uff0c\u76f4\u5230\u53d1\u73b0ELF\u7684\u5934\u90e8\uff0c\u968f\u540e\u5411\u524d\u626b\u63cf\u53d1\u73b0\u653b\u51fb\u8005\u60f3\u8981\u8c03\u7528\u7684\u51fd\u6570\u7684\u7279\u5f81\u3002\u8fd9\u79cd\u65b9\u6cd5\u662f\u53ef\u884c\u7684\uff0c\u4f46\u5e76\u4e0d\u5341\u5206\u53ef\u9760\uff0c\u56e0\u4e3a\u4e00\u4e2a\u5e93\u7684\u4e0d\u540c\u7248\u672c(\u6216\u5b9e\u73b0)\u53ef\u80fd\u65e0\u6cd5\u901a\u8fc7\u5355\u4e00\u7684\u7279\u5f81\u5c31\u786e\u5b9a\u3002\u7b2c\u4e8c\u9879\u6280\u672f\u8981\u53ef\u9760\u4e00\u4e9b\uff0c\u56e0\u4e3a\u5b83\u5b9e\u73b0\u4e86\u4e00\u4e2a\u5b8c\u6574\u7684\u7b26\u53f7\u89e3\u6790\u7684\u8fc7\u7a0b\uff0c\u5c31\u50cf\u52a8\u6001\u88c5\u8f7d\u5668\u4e00\u6837\u3002<\/span><\/p>\n

            \u6211\u4eec\u5b9e\u73b0\u4e86\u8fd9\u4e24\u79cd\u65b9\u6cd5\uff0c\u4f7f\u7528\u4e00\u79cdx86\u67b6\u6784\u4e0a\u57fa\u4e8eQ [34]\u7684\u56fe\u7075\u5b8c\u5168ROP\u7f16\u8bd1\u5668\uff0c\u79f0\u4e3aROPC [22]\u3002\u6211\u4eec\u5728\u90e8\u5206RELRO\u4e0e\u5b8c\u5168RELRO\u4e24\u79cd\u60c5\u51b5\u4e0b\u4e0eLeakless\u7684ROPC\u540e\u7aef\u8fdb\u884c\u4e86\u6bd4\u8f83\u3002\u4e3a\u4e86\u5b8c\u6574\u8d77\u89c1\uff0c\u6211\u4eec\u540c\u6837\u5305\u62ec\u4e86Leakless\u7684\u624b\u52a8\u540e\u7aef\uff0c\u4f7f\u7528\u7528\u6237\u6307\u5b9a\u7684gadgets.<\/span><\/p>\n

            \u4e8b\u5b9e\u4e0a\uff0cROP\u94fe\u957f\u5ea6\u662f\u5341\u5206\u91cd\u8981\u7684\uff0c\u4e00\u4e2a\u6f0f\u6d1e\u5f80\u5f80\u4f34\u968f\u7740\u56fa\u5b9a\u957f\u5ea6\u7684\u8f7d\u8377\u9650\u5236\u3002\u4e3a\u4e86\u6d4b\u91cfLeakless\u7684ROP\u94fe\u957f\u5ea6\u7684\u5f71\u54cd\uff0c\u6211\u4eec\u6536\u96c6\u4e86Metasploit Framework [31] (\u4e00\u4e2a\u53ef\u4ee5\u81ea\u52a8\u8fdb\u884c\u591a\u79cd\u8f6f\u4ef6\u5df2\u77e5\u6f0f\u6d1e\u5229\u7528\u7684\u5de5\u5177)\u4e2d\u6240\u6709\u6f0f\u6d1e\u7684\u8f7d\u8377\u957f\u5ea6\u9650\u5236\u3002\u6211\u4eec\u53d1\u73b01303\u4e2a\u6f0f\u6d1e\u4e2d\u7684946\u4e2a\u6709\u6700\u5927\u8f7d\u8377\u957f\u5ea6\u9650\u5236\uff0c\u5b83\u4eec\u7684\u5e73\u5747\u6700\u5927\u8f7d\u8377\u957f\u5ea6\u4e3a1332\u5b57\u8282\u3002\u4e3a\u4e86\u5c55\u793a\u81ea\u52a8\u751f\u6210\u590d\u6742\u5229\u7528\u7684\u53ef\u884c\u6027\u7684\u589e\u957f\uff0c\u6211\u4eec\u5728\u56fe\u4e2d\u589e\u52a0\u4e86\u6bcf\u79cd\u6280\u672f\u80fd\u591f\u81ea\u52a8\u751f\u6210\u8db3\u591f\u77ed\u7684ROP\u94fe\u6765\u5229\u7528\u7684Metasploit\u6f0f\u6d1e\u5360\u5176\u603b\u6f0f\u6d1e\u7684\u767e\u5206\u6bd4\u3002<\/span><\/p>\n

            \u7ed3\u679c\uff0c\u5728\u4e3aROPC\u7684\u6d4b\u8bd5\u7a0b\u5e8f\u751f\u6210\u7684ROP\u94fe\u957f\u5ea6\u65b9\u9762\u548c\u5bf9Metasploit\u7684\u6f0f\u6d1e\u5229\u7528\u7684\u53ef\u884c\u6027\u65b9\u9762\uff0c\u8fd9\u4e9b\u6280\u672f\u7684\u8868\u73b0\u5982\u88683\u6240\u793a\u3002Leakless\u5168\u9762\u8d85\u8fc7\u4e86\u73b0\u6709\u7684\u6280\u672f\uff0c\u4e0d\u4ec5\u662f\u5728\u8fdb\u884c\u521d\u59cb\u8c03\u7528\u7684ROP\u94fe\u7edd\u5bf9\u957f\u5ea6\u4e0a\uff0c\u5728\u6bcf\u6b21\u989d\u5916\u8c03\u7528\u4e0a\u7684\u5f00\u9500\u4e5f\u66f4\u5c0f\u3002\u8fd9\u4f7f\u5b83\u5728\u8fdb\u884c\u50cf6.4\u8282\u4e2d\u7684\u590d\u6742\u653b\u51fb\u4e2d\u66f4\u52a0\u6709\u6548\u3002<\/span><\/p>\n

            \"Table3\"<\/a><\/p>\n

            Table 3: ROPC\u4e3a6.5\u8282\u4e2d\u7684\u6bcf\u79cd\u6280\u672f\u751f\u6210\u7684ROP\u94fe\u7684\u957f\u5ea6\uff0c\u4ee5\u53caLeakless\u624b\u52a8\u540e\u7aef\u751f\u6210\u7684\u7ed3\u679c(*)\u3002\u7b2c2\u5217\u4ee3\u8868\u4ece\u653b\u51fb\u51c6\u5907\u5230\u7b2c\u4e00\u6b21\u8c03\u7528\u9700\u8981\u7684\u5b57\u8282\u6570\uff0c\u7b2c3\u5217\u5219\u8868\u793a\u540e\u6765\u7684\u8c03\u7528\u6bcf\u6b21\u9700\u8981\u7684\u5b57\u8282\u6570\u3002\u6700\u540e\uff0c\u7b2c4\u5217\u663e\u793a\u4e86\u6309\u7167\u5176\u7b2c\u4e00\u6b21\u8c03\u7528\u7684\u5927\u5c0f\u751f\u6210\u7684ROP\u94fe\u80fd\u591f\u5229\u7528\u7684Metasploit\u4e2d\u7684\u6f0f\u6d1e\u6bd4\u7387\u3002<\/span><\/p>\n

            ========================================================================<\/span><\/p>\n

            7 \u8ba8\u8bba<\/strong><\/p>\n

            \u5728\u8fd9\u8282\u4e2d\uff0c\u6211\u4eec\u5c06\u8ba8\u8bba\u4e0eLeakless\u6709\u5173\u7684\u51e0\u4e2a\u65b9\u9762: \u4e3a\u4ec0\u4e48\u5b83\u63d0\u4f9b\u7ed9\u653b\u51fb\u8005\u7684\u80fd\u529b\u5f88\u6709\u4ef7\u503c\uff0c\u5728\u4ec0\u4e48\u60c5\u51b5\u4e0b\u5b83\u6700\u9002\u5408\uff0c\u5b83\u7684\u5c40\u9650\u6027\u5728\u54ea\u91cc\uff0c\u4ee5\u53ca\u5982\u4f55\u7f13\u89e3\u5176\u5e26\u6765\u7684\u5f71\u54cd\u3002<\/span><\/p>\n

            7.1 Leakless\u7684\u5e94\u7528<\/strong><\/p>\n

            Leakless\u4f5c\u4e3a\u6f0f\u6d1e\u5229\u7528\u5f00\u53d1\u8005\u519b\u68b0\u5e93\u4e2d\u7684\u4e00\u4ef6\u5f3a\u529b\u5de5\u5177\uff0c\u4e3b\u8981\u80fd\u591f\u5728\u4e09\u4e2a\u9886\u57df\u5e2e\u52a9\u4ed6\u4eec: \u529f\u80fd\u91cd\u7528\uff0c\u4e00\u51fb\u5229\u7528\uff0c\u4ee5\u53caROP\u94fe\u7684\u7f29\u77ed\u3002<\/span><\/p>\n

            [\u4e00\u51fb\u5229\u7528] \u6240\u6709\u5229\u7528\u90fd\u53ef\u4ee5\u4f7f\u7528Leakless\u6765\u7b80\u5316\uff0c\u6211\u4eec\u8bbe\u8ba1\u5b83\u7684\u76ee\u6807\u662f\u4f7f\u5f97\u90a3\u4e9b\u9700\u8981\u4fe1\u606f\u6cc4\u6f0f\u6f0f\u6d1e\u7684\u5229\u7528\u5728\u65e0\u6cd5\u8fdb\u884c\u4fe1\u606f\u6cc4\u6f0f\u65f6\u4ecd\u7136\u53ef\u884c\u3002\u8fd9\u7c7b\u7a0b\u5e8f\u4e2d\u6709\u4e00\u5927\u90e8\u5206\u90fd\u662f\u6587\u4ef6\u683c\u5f0f\u89e3\u6790\u5668\u3002<\/span><\/p>\n

            \u89e3\u6790\u6587\u4ef6\u683c\u5f0f\u7684\u4ee3\u7801\u6781\u5176\u590d\u6742\uff0c\u6b63\u56e0\u5982\u6b64\uff0c\u5f53\u9047\u5230\u4e0d\u53ef\u4fe1\u7684\u8f93\u5165\u65f6\uff0c\u5c31\u6709\u5185\u5b58\u7834\u574f\u7684\u503e\u5411\u3002\u6709\u5f88\u591a\u8fd9\u6837\u7684\u4f8b\u5b50: \u8fc7\u53bb10\u5e74\u89e3\u6790\u56fe\u7247\u7684libpng\u5e93\u670927\u6761CVE\u8bb0\u5f55 [10], libtiff\u5219\u670953\u6761 [11]\u3002\u590d\u6742\u683c\u5f0f\u7684\u89e3\u6790\u5668\u751a\u81f3\u66f4\u52a0\u7cdf\u7cd5: \u8fc7\u53bb5\u5e74\u591a\u5a92\u4f53\u5e93ffmpeg\u5df2\u7ecf\u7d2f\u8ba1\u4e86170\u6761CVE\u8bb0\u5f55 [9].\u4e0d\u4ec5\u4ec5\u5c40\u9650\u4e8e\u591a\u5a92\u4f53\u7c7b\u7684\u5e93\u3002Wireshark\uff0c \u4e00\u4e2a\u7f51\u7edc\u5305\u5206\u6790\u5668\uff0c\u6709285\u6761CVE\u8bb0\u5f55\uff0c\u591a\u6570\u662f\u56e0\u4e3a\u7f51\u7edc\u534f\u8bae\u5206\u6790\u63d2\u4ef6\u7684\u6f0f\u6d1e [12].<\/span><\/p>\n

            \u8fd9\u4e9b\u5e93\uff0c\u4ee5\u53ca\u548c\u5b83\u4eec\u7c7b\u4f3c\u7684\u5176\u5b83\u5e93\uff0c\u5f80\u5f80\u662f\u79bb\u7ebf\u5de5\u4f5c\u7684\u3002\u7528\u6237\u53ef\u4ee5\u5148\u4e0b\u8f7d\u4e00\u4e2a\u5a92\u4f53\u6216\u8005PCAP\u6587\u4ef6\uff0c\u7136\u540e\u4f7f\u7528\u8fd9\u4e9b\u5e93\u6765\u89e3\u6790\u3002\u5f53\u6f0f\u6d1e\u89e6\u53d1\u7684\u65f6\u5019\uff0c\u653b\u51fb\u8005\u65e0\u6cd5\u4e0e\u53d7\u5bb3\u8005\u5efa\u7acb\u4e00\u4e2a\u76f4\u63a5\u8fde\u63a5\u6765\u63a5\u53d7\u6cc4\u6f0f\u7684\u4fe1\u606f\u6216\u8005\u53d1\u9001\u989d\u5916\u7684\u653b\u51fb\u8f7d\u8377\u3002\u4e0d\u4ec5\u5982\u6b64\uff0c\u5927\u90e8\u5206\u8fd9\u79cd\u683c\u5f0f\u90fd\u662f\u88ab\u52a8\u7684\uff0c\u4e5f\u5c31\u662f\u8bf4(\u4e0d\u50cfPDF)\uff0c\u5b83\u4eec\u4e0d\u542b\u6709\u653b\u51fb\u8005\u6a21\u62df2\u4e2a\u9636\u6bb5\u5229\u7528\u9700\u8981\u7684\u811a\u672c\u3002\u7ed3\u679c\uff0c\u5373\u4f7f\u8fd9\u4e9b\u5e93\u662f\u6709\u6f0f\u6d1e\u7684\uff0c\u5bf9\u5b83\u4eec\u7684\u5229\u7528\u4e5f\u662f\u975e\u5e38\u56f0\u96be\uff0c\u4e0d\u53ef\u9760\uff0c\u6216\u8005\u5b8c\u5168\u4e0d\u53ef\u5b9e\u884c\u3002\u901a\u8fc7\u907f\u514d\u4fe1\u606f\u6cc4\u6f0f\u7684\u6b65\u9aa4\uff0cLeakless\u80fd\u591f\u4f7f\u5f97\u8fd9\u4e9b\u5229\u7528\u80fd\u66f4\u7b80\u5355\uff0c\u53ef\u9760\uff0c\u53ef\u884c\u3002<\/span><\/p>\n

            [\u529f\u80fd\u91cd\u7528] Leakless\u8ba9\u653b\u51fb\u8005\u80fd\u591f\u8c03\u7528\u7a0b\u5e8f\u52a0\u8f7d\u7684\u5e93\u4e2d\u7684\u4efb\u610f\u51fd\u6570\u3002\u4e8b\u5b9e\u4e0a\uff0c\u6f0f\u6d1e\u7a0b\u5e8f\u4e0d\u9700\u8981\u771f\u6b63”\u5bfc\u5165”\u8fd9\u4e9b\u51fd\u6570\uff0c\u5b83\u53ea\u9700\u8981\u5bf9\u8fd9\u4e9b\u5e93\u8fdb\u884c\u94fe\u63a5\u5373\u53ef(\u5373\u53ef\u4ee5\u8c03\u7528\u5e93\u4e2d\u7684\u5176\u5b83\u51fd\u6570)\u3002\u8fd9\u5c31\u5e26\u6765\u4e86\u4e00\u4e9b\u4fbf\u5229\u3002<\/span><\/p>\n

            \u9996\u5148\uff0c\u88ab\u5927\u90e8\u5206\u7a0b\u5e8f\u94fe\u63a5\u7684C\u6807\u51c6\u5e93\uff0c\u5305\u542b\u4e86\u51e0\u4e4e\u6240\u6709\u7cfb\u7edf\u8c03\u7528\u7684\u5c01\u88c5\u51fd\u6570(\u4f8b\u5982read()\u3001execve()\u7b49\u7b49)\u3002\u8fd9\u5c31\u610f\u5473\u7740Leakless\u80fd\u591f\u8fdb\u884c\u4efb\u4f55\u7cfb\u7edf\u8c03\u7528\uff0c\u5e76\u4e14\u53ef\u4ee5\u5728\u6ca1\u6709\u7cfb\u7edf\u8c03\u7528gadget\u7684\u60c5\u51b5\u4e0b\u4f7f\u7528\u4e00\u6761\u77ed\u5c0f\u7684ROP\u94fe\u5b8c\u6210\u3002<\/span><\/p>\n

            \u4e0d\u4ec5\u5982\u6b64\uff0c\u5c31\u50cf6.4\u8282\u4e2d\u8bf4\u7684\uff0cLeakless\u80fd\u591f\u8f7b\u6613\u5730\u91cd\u7528\u7a0b\u5e8f\u903b\u8f91\u4e2d\u73b0\u6709\u7684\u529f\u80fd\u3002\u8fd9\u5f88\u91cd\u8981\uff0c\u539f\u56e0\u6709\u4e8c\u3002<\/span><\/p>\n

            \u7b2c\u4e00\u4e2a\u539f\u56e0\uff0c\u901a\u8fc7\u5c06\u5229\u7528\u4f2a\u88c5\u6210\u7a0b\u5e8f\u6b63\u5e38\u7684\u884c\u4e3a\u80fd\u591f\u5e2e\u52a9\u653b\u51fb\u8005\u8fdb\u884c\u66f4\u52a0\u9690\u79d8\u7684\u653b\u51fb\u3002\u5f53\u6807\u51c6\u5229\u7528\u7684\u5957\u8def\u88ab\u8bf8\u5982seccomp [2], AppArmor [1] \u6216SELinux [25]\u8fd9\u79cd\u4fdd\u62a4\u673a\u5236\u5c01\u9501\u65f6\uff0c\u8fd9\u5c31\u662f\u51b3\u5b9a\u6027\u7684\u3002<\/span><\/p>\n

            \u7b2c\u4e8c\u4e2a\u539f\u56e0\uff0c\u6839\u636e\u653b\u51fb\u8005\u7684\u5177\u4f53\u76ee\u6807\uff0c\u91cd\u7528\u51fd\u6570\u529f\u80fd\u5f80\u5f80\u6bd4\u6267\u884c\u4efb\u610f\u547d\u4ee4\u66f4\u597d\u3002\u9664\u4e86\u5728Pidgin\u7684\u6848\u4f8b\u7814\u7a76\u4e2d\u7684\u653b\u51fb\u4e4b\u5916\uff0c\u653b\u51fb\u8005\u53ef\u4ee5\u6084\u6084\u5730\u5728Firefox\u6d4f\u89c8\u5668\u4e2d\u542f\u7528\u4e0d\u5b89\u5168\u7684\u5bc6\u7801\u5957\u4ef6\u6216\u8005SSL\u7684\u4e0d\u5b89\u5168\u7248\u672c\uff0c\u4ec5\u4ec5\u9700\u8981\u4e00\u4e2aSSL_CipherPrefSetDefault\u8c03\u7528 [24].<\/span><\/p>\n

            [\u7f29\u77edROP\u94fe] \u5c31\u50cf6.5\u8282\u8bf4\u7684\uff0cLeakless\u80fd\u591f\u4ea7\u751f\u6bd4\u73b0\u6709\u6280\u672f\u66f4\u77ed\u7684ROP\u94fe\u3002\u5b9e\u9645\u4e0a\uff0c\u5728\u5f88\u591a\u573a\u5408\uff0cLeakless\u901a\u8fc7\u4ea7\u751f\u5c0f\u4e8e1KB\u7684ROP\u94fe\u5c31\u80fd\u5b8c\u6210\u4efb\u610f\u51fd\u6570\u7684\u8c03\u7528\u3002\u5728\u5f88\u591a\u6f0f\u6d1e\u90fd\u6709\u8f93\u5165\u957f\u5ea6\u7684\u9650\u5236\u7684\u60c5\u51b5\u4e0b\uff0c\u8fd9\u662f\u5f88\u91cd\u8981\u7684\u7ed3\u679c\u3002\u4f8b\u5982\uff0c\u6211\u4eec\u5728Pidgin\u7684\u6848\u4f8b\u7814\u7a76\u4e2d\u5229\u7528\u7684\u6f0f\u6d1e\u5141\u8bb8\u7684\u6700\u5927ROP\u94fe\u957f\u5ea6\u4e3a1KB\u3002\u666e\u901a\u7684ROP\u7f16\u8bd1\u6280\u672f\u65e0\u6cd5\u81ea\u52a8\u751f\u6210\u8fd9\u4e2a\u6f0f\u6d1e\u7684\u8f7d\u8377\uff0c\u800cLeakless\u5374\u53ef\u4ee5\u901a\u8fc7\u81ea\u52a8\u751f\u6210\u4e0d\u8d85\u8fc7\u957f\u5ea6\u9650\u5236\u7684ROP\u94fe\u6765\u8c03\u7528\u4efb\u610f\u51fd\u6570\u3002<\/span><\/p>\n

            7.2 \u9650\u5236<\/strong><\/p>\n

            Leakless\u6700\u5927\u7684\u9650\u5236\u5c31\u662f\u5728\u6ca1\u6709\u4fe1\u606f\u6cc4\u6f0f\u7684\u60c5\u51b5\u4e0b\u65e0\u6cd5\u5904\u7406\u4f4d\u7f6e\u65e0\u5173\u53ef\u6267\u884c\u6587\u4ef6(Position Independent Executables, PIEs)\u3002\u8fd9\u662f\u4f7f\u7528ROP\u7684\u6280\u672f\u7684\u901a\u75c5\uff0c\u56e0\u4e3aROP\u94fe\u4e2d\u7684gadgets\u7684\u7edd\u5bf9\u5730\u5740\u5fc5\u987b\u786e\u5b9a\u3002\u9664\u6b64\u4e4b\u5916\uff0c\u5728\u6ca1\u6709\u7a0b\u5e8f\u57fa\u5730\u5740\u7684\u60c5\u51b5\u4e0b\uff0cLeakless\u4e5f\u65e0\u6cd5\u5b9a\u4f4d\u5b83\u8981\u7834\u574f\u7684\u52a8\u6001\u88c5\u8f7d\u5668\u7ed3\u6784\u3002<\/span><\/p>\n

            \u5f53\u9047\u5230PIE\u7684\u7a0b\u5e8f\u65f6\uff0cLeakless\u9700\u8981\u653b\u51fb\u8005\u80fd\u591f\u63d0\u4f9b\u5e94\u7528\u7a0b\u5e8f\u7684\u57fa\u5730\u5740\uff0c\u8fd9\u5e94\u8be5\u80fd\u591f\u901a\u8fc7\u4e00\u4e2a\u4fe1\u606f\u6cc4\u6f0f\u6f0f\u6d1e\u5f97\u5230(\u6216\u8005\u4f7f\u7528BROP\u6280\u672f [5])\u3002\u8fd9\u5c31\u6253\u7834\u4e86Leakless\u4e0d\u9700\u8981\u4fe1\u606f\u6cc4\u6f0f\u5c31\u53ef\u4ee5\u8fdb\u884c\u64cd\u4f5c\u7684\u80fd\u529b\u3002\u4e0d\u8fc7Leakless\u4ecd\u7136\u662f\u8fdb\u884c\u5229\u7528\u6700\u65b9\u4fbf\u7684\u65b9\u5f0f\uff0c\u56e0\u4e3a\u4e0d\u9700\u8981\u6cc4\u6f0f\u5e93\u7684\u5730\u5740\u548c\u5185\u5bb9\u3002\u9664\u6b64\u4e4b\u5916\uff0c\u4f9d\u636e\u5177\u4f53\u60c5\u51b5\uff0c\u4ec5\u4ec5\u6cc4\u6f0f\u7a0b\u5e8f\u7684\u5730\u5740\u6216\u8bb8\u6bd4\u6cc4\u6f0f\u6574\u4e2a\u5e93\u7684\u5185\u5bb9\u66f4\u52a0\u53ef\u884c\u3002\u4e0e\u5176\u5b83\u9700\u8981\u540e\u8005\u7684\u6280\u672f\u4e0d\u540c\uff0cLeakless\u53ea\u9700\u8981\u524d\u8005\u3002<\/span><\/p>\n

            \u5b9e\u9645\u5f53\u4e2d\uff0cPIE\u56e0\u4e3a\u5173\u7cfb\u5230\u6027\u80fd\u5f00\u9500\u5e76\u4e0d\u592a\u5e38\u89c1\u3002\u6709\u6d4b\u8bd5\u7ed3\u679c\u663e\u793aPIE\u5728x86\u5904\u7406\u5668\u4e0a\u7684\u989d\u5916\u5f00\u9500\u5e73\u5747\u4e3a10%\uff0c\u800c\u5728x86-64\u5904\u7406\u5668\u4e0a\uff0c\u5f97\u76ca\u4e8e\u76f8\u5bf9\u6307\u4ee4\u6307\u9488(instruction-pointer-relative)\u7684\u5bfb\u5740\u65b9\u5f0f\uff0c\u5e73\u5747\u67093.6%\u7684\u989d\u5916\u5f00\u9500 [28] \u3002<\/span><\/p>\n

            \u56e0\u4e3aPIE\u76f8\u5173\u7684\u989d\u5916\u5f00\u9500\u5f00\u9500\u592a\u5927\uff0c\u5927\u90e8\u5206\u53d1\u884c\u7248\u53ea\u5c06\u90a3\u4e9b\u201c\u6709\u98ce\u9669\u201d\u7684\u7a0b\u5e8f\u4e0a\u5f00\u542fPIE\u3002\u4f8b\u5982\uff0c\u8d44\u6599\u663e\u793a\uff0cUbuntu\u7684\u5b98\u65b9\u652f\u6301\u7a0b\u5e8f\u5305(\u5373\u5728\u4e3b\u8981\u4ed3\u5e93\u4e2d\u7684\u5305)\u4e2d\u53ea\u670927\u4e2a\u5f00\u542f\u4e86PIE\uff0c\u6ca1\u6709\u5f00\u542f\u7684\u5219\u6709\u8d85\u8fc727000\u4e2a\u5305 [40]\u3002\u6b63\u59826.1\u8282\u4e2d\u8bf4\u7684\uff0cPIE\u53ef\u6267\u884c\u7a0b\u5e8f\u53ea\u5360\u6211\u4eec\u8c03\u7814\u8fc7\u7684\u6240\u6709\u7cfb\u7edf\u4e2d\u5f88\u5c0f\u4e00\u90e8\u5206\u3002<\/span><\/p>\n

            7.3 \u5bf9\u6297\u63aa\u65bd<\/strong><\/p>\n

            \u6709\u591a\u79cd\u80fd\u591f\u5bf9\u6297Leakless\u7684\u65b9\u6cd5\uff0c\u4e0d\u8fc7\u5b83\u4eec\u90fd\u6709\u7f3a\u70b9\u3002\u5728\u672c\u8282\u4e2d\u6211\u4eec\u5c06\u4f1a\u5206\u6790\u6700\u9002\u7528\u7684\u51e0\u79cd\u65b9\u6cd5\u3002<\/span><\/p>\n

            [\u4f4d\u7f6e\u65e0\u5173\u53ef\u6267\u884c] \u4e00\u4e2a\u5feb\u901f\u7684\u5bf9\u6297\u63aa\u65bd\u5c31\u662f\u8ba9\u6240\u6709\u7cfb\u7edf\u4e2d\u7684\u53ef\u6267\u884c\u6587\u4ef6\u90fd\u662f\u4f4d\u7f6e\u65e0\u5173\u7684\u3002\u8fd9\u867d\u7136\u4f1a\u5c01\u9501Leakless\u7684\u81ea\u52a8\u64cd\u4f5c(\u5c31\u50cf7.2\u8282\u4e2d\u8ba8\u8bba\u7684\u90a3\u6837)\uff0c\u4f46\u5f53\u5b58\u5728\u4efb\u4f55\u4fe1\u606f\u6cc4\u6f0f\u65f6Leakless\u7684\u6280\u672f\u8fd8\u662f\u53ef\u4ee5\u5e94\u7528\u7684\u3002\u4e3a\u6b64\uff0c\u518d\u52a0\u4e0aPIE\u76f8\u5173\u7684\u6027\u80fd\u5f00\u9500\uff0c\u6211\u4eec\u8ba4\u4e3a\u8fd9\u8282\u4e2d\u8ba8\u8bba\u7684\u5176\u4ed6\u5bf9\u6297\u63aa\u65bd\u6bd4\u5b83\u66f4\u4e3a\u9002\u7528\u3002<\/span><\/p>\n

            [\u7981\u7528\u60f0\u6027\u88c5\u8f7d] \u5f53LD_BIND_NOW\u73af\u5883\u53d8\u91cf\u88ab\u8bbe\u7f6e\u65f6\uff0c\u52a8\u6001\u88c5\u8f7d\u5668\u5c06\u4f1a\u5b8c\u5168\u5730\u7981\u7528\u60f0\u6027\u88c5\u8f7d\u3002\u8fd9\u5c31\u610f\u5473\u7740\uff0c\u6240\u6709\u4e3a\u4e86\u7a0b\u5e8f\u548c\u5176\u4f9d\u8d56\u5e93\u7684\u5bfc\u5165\u5c06\u5728\u7a0b\u5e8f\u5f00\u59cb\u65f6\u88ab\u89e3\u6790\u3002\u7531\u6b64\u5e26\u6765\u7684\u526f\u4f5c\u7528\u5c31\u662f_dl_runtime_resolve\u51fd\u6570\u7684\u5730\u5740\u4e0d\u4f1a\u88ab\u88c5\u8f7d\u5230\u4efb\u4f55\u5e93\u7684GOT\u4e2d\uff0cLeakless\u5c31\u65e0\u6cd5\u5de5\u4f5c\u4e86\u3002\u8fd9\u5c31\u76f8\u5f53\u4e8e\u5728\u6574\u4e2a\u7cfb\u7edf\u4e0a\u5e94\u7528\u4e86\u5b8c\u5168RELRO\u3002\u6240\u4ee5\uff0c\u4ed6\u4e5f\u540c\u6837\u4f1a\u5e26\u6765\u4e0d\u53ef\u5ffd\u7565\u7684\u6027\u80fd\u4e0a\u7684\u989d\u5916\u5f00\u9500\u3002<\/span><\/p>\n

            [\u7981\u7528DT_DEBUG] \u6700\u540e\uff0cLeakless\u5c06\u4f1a\u4f7f\u7528DT_DEBUG\u8fd9\u4e2a\u52a8\u6001\u6761\u76ee\u6765\u7ed5\u8fc7\u5b8c\u5168RELRO\u3002\u800c\u8fd9\u4e2a\u6761\u76ee\u662f\u8c03\u8bd5\u5668\u7528\u6765\u62e6\u622a\u4e0e\u88c5\u8f7d\u6709\u5173\u4e8b\u4ef6\u4f7f\u7528\u7684\u3002\u73b0\u5728\uff0c\u8fd9\u4e2a\u57df\u603b\u662f\u4f1a\u88ab\u52a0\u8f7d\uff0c\u4e3aLeakless\u7684\u5b8c\u5168RELRO\u7ed5\u8fc7\u655e\u5f00\u5927\u95e8\u3002\u4e3a\u4e86\u5173\u95ed\u8fd9\u4e2a\u5751\uff0c\u53ef\u4ee5\u5bf9\u52a8\u6001\u88c5\u8f7d\u5668\u8fdb\u884c\u4fee\u6539\u8ba9\u5b83\u53ea\u5728\u6709\u8c03\u8bd5\u5668\u5b58\u5728\u6216\u6709\u660e\u786e\u5b9a\u4e49\u7684\u73af\u5883\u53d8\u91cf\u5b58\u5728\u65f6\u624d\u53bb\u521d\u59cb\u5316\u8fd9\u4e2a\u503c\u3002<\/span><\/p>\n

            [\u5bf9\u88c5\u8f7d\u5668\u63a7\u5236\u7ed3\u6784\u66f4\u597d\u7684\u4fdd\u62a4] Leakless\u975e\u5e38\u4f9d\u8d56\u4e8e\u201c\u52a8\u6001\u88c5\u8f7d\u5668\u7684\u63a7\u5236\u7ed3\u6784\u5f88\u597d\u83b7\u5f97\u201d\u8fd9\u4e00\u4e8b\u5b9e\uff0c\u5e76\u4e14\u5b83\u4eec\u7684\u4f4d\u7f6e\u4e5f\u662f\u4f17\u6240\u5468\u77e5\u7684\u3002\u4e0e\u5c06\u5b83\u4eec\u88c5\u8f7d\u5230\u4e00\u4e2a\u5df2\u77e5\u4f4d\u7f6e\u76f8\u6bd4\uff0c\u628a\u8fd9\u4e9b\u7ed3\u6784\u66f4\u597d\u5730\u4fdd\u62a4\u6216\u8005\u9690\u85cf\u5728\u5185\u5b58\u4e2d\u4f1a\u662f\u4e2a\u597d\u4e3b\u610f\u3002\u4f8b\u5982\uff0c\u5728 [29] \u4e2d\u8bf4\u7684\u90a3\u6837\uff0c\u5bf9\u4e8e\u8fd9\u4e9b\u7ed3\u6784\u4ee5\u53ca\u4efb\u4f55\u4f1a\u63d0\u4f9b\u7b26\u53f7\u89e3\u6790\u63a7\u5236\u6570\u636e\u7684\u6bb5\uff0c\u5e94\u5f53\u5728\u521d\u59cb\u5316\u540e\u5c06\u5b83\u4eec\u6807\u4e3a\u53ea\u8bfb\u3002\u8fd9\u6837\u7684\u6539\u8fdb\u80fd\u591f\u5f7b\u5e95\u62b9\u6d88Leakless\u7834\u574f\u8fd9\u4e9b\u7ed3\u6784\u7684\u80fd\u529b\uff0c\u5e76\u80fd\u9632\u6b62\u5c06\u63a7\u5236\u6d41\u91cd\u5b9a\u5411\u5230\u654f\u611f\u51fd\u6570\u7684\u8fd9\u7c7b\u653b\u51fb\u3002<\/span><\/p>\n

            \u6b64\u5916\uff0c\u4fee\u6539\u88c5\u8f7d\u7684\u8fc7\u7a0b\u8ba9\u5b83\u4f7f\u7528\u4e00\u5f20\u8868\u6765\u8bb0\u5f55link_map\u7ed3\u6784\uff0c\u5e76\u7ed9_dl_runtime_resolve\u5728\u8868\u4e2d\u8d4b\u4e88\u4e00\u4e2a\u4e0b\u6807\uff0c\u800c\u4e0d\u662f\u4f7f\u7528\u4e00\u4e2a\u76f4\u63a5\u7684\u6307\u9488\uff0c\u8fd9\u6837\u80fd\u591f\u6253\u7834Leakless\u5bf9\u5b8c\u5168RELRO\u7684\u7ed5\u8fc7\u3002\u7136\u800c\uff0c\u8fd9\u79cd\u6539\u53d8\u5c06\u4f1a\u7834\u574f\u4e4b\u524d\u7f16\u8bd1\u7684\u4efb\u4f55\u4e8c\u8fdb\u5236\u7a0b\u5e8f\u7684\u517c\u5bb9\u6027\u3002<\/span><\/p>\n

            [\u9694\u79bb\u52a8\u6001\u88c5\u8f7d\u5668] \u5c06\u52a8\u6001\u88c5\u8f7d\u5668\u4ece\u76ee\u6807\u7a0b\u5e8f\u7684\u5730\u5740\u7a7a\u95f4\u4e2d\u9694\u79bb\u662f\u4e00\u4e2a\u6709\u6548\u7684\u5bf9\u6297\u63aa\u65bd\u3002\u4e3e\u4f8b\u6765\u8bf4\uff0c\u8bfa\u57fa\u4e9a\u7684\u585e\u73ed\u64cd\u4f5c\u7cfb\u7edf\uff0c\u5176\u4f7f\u7528\u4e86\u5fae\u5185\u6838\u7ed3\u6784\uff0c\u52a8\u6001\u88c5\u8f7d\u5668\u662f\u5728\u4e00\u4e2a\u5355\u72ec\u7684\u8fdb\u7a0b\u4e2d\u5b9e\u73b0\u7684\uff0c\u8fd9\u4e2a\u8fdb\u7a0b\u4f5c\u4e3a\u4e00\u4e2a\u7cfb\u7edf\u670d\u52a1\u5668(system server)\u4e0e\u5185\u6838\u4ea4\u4e92\u3002\u8fd9\u5c31\u4fdd\u8bc1\u4e86\u52a8\u6001\u88c5\u8f7d\u5668\u7684\u63a7\u5236\u7ed3\u6784\u4e0d\u4f1a\u88ab\u7a0b\u5e8f\u7834\u574f\u3002\u6240\u4ee5\uff0c\u8fd9\u5b9e\u9645\u4e0a\u5df2\u7ecf\u4f7f\u5f97Leakless\u5931\u6548\u4e86\u3002\u7136\u800c\uff0c\u8fd9\u79cd\u5bf9\u6297\u63aa\u65bd\u5c06\u4f1a\u7ed9\u7a0b\u5e8f\u7684\u6574\u4f53\u6027\u80fd\u5e26\u6765\u76f8\u5f53\u5927\u7684\u5f71\u54cd\uff0c\u56e0\u4e3a\u8fdb\u7a0b\u95f4\u901a\u4fe1(Inter-Process Communication, IPC)\u4e5f\u9700\u8981\u989d\u5916\u5f00\u9500\u3002<\/span><\/p>\n

            \u603b\u4f53\u6765\u8bf4\uff0c\u8fd9\u4e9b\u7f13\u89e3\u63aa\u65bd\u8981\u4e48\u5e26\u6765\u8fd0\u884c\u65f6\u7684\u6027\u80fd\u5f00\u9500(PIE\u6216\u88c5\u8f7d\u5668\u9694\u79bb)\uff0c\u8981\u4e48\u5e26\u6765\u88c5\u8f7d\u65f6\u7684\u6027\u80fd\u5f00\u9500(\u975e\u60f0\u6027\u88c5\u8f7d\u548c\u7cfb\u7edf\u8303\u56f4\u7684RELRO)\uff0c\u8981\u4e48\u9700\u8981\u4fee\u6539\u88c5\u8f7d\u7684\u8fc7\u7a0b(DT_DEBUG\u7684\u7981\u7528\u4ee5\u53ca\u88c5\u8f7d\u5668\u63a7\u5236\u7ed3\u6784\u9690\u85cf).\u4ece\u957f\u8fdc\u6765\u770b\uff0c\u6211\u4eec\u76f8\u4fe1\u4e00\u4e2a\u8003\u8651\u5b89\u5168\u7684\u5bf9\u52a8\u6001\u88c5\u8f7d\u5668\u7684\u91cd\u65b0\u8bbe\u8ba1\u5c06\u4f1a\u8ba9\u6211\u4eec\u90fd\u53d7\u76ca\u532a\u6d45\u3002\u5728\u77ed\u671f\u5185\uff0c\u4e5f\u6709\u51e0\u79cd\u9488\u5bf9Leakless\u53ef\u9009\u7684\u4fdd\u62a4\u65b9\u6848\uff0c\u4e0d\u8fc7\u90fd\u4f1a\u6709\u6027\u80fd\u635f\u5931\u3002<\/span><\/p>\n

            ========================================================================<\/span><\/p>\n

            8 \u7ed3\u8bba<\/strong><\/p>\n

            \u5728\u8fd9\u7bc7\u6587\u7ae0\u4e2d\uff0c\u6211\u4eec\u5c55\u793a\u4e86Leakless\u8fd9\u79cd\u65b0\u6280\u672f\uff0c\u80fd\u591f\u4f7f\u7528\u52a8\u6001\u88c5\u8f7d\u5668\u7684\u529f\u80fd\u6765\u4f7f\u5f97\u653b\u51fb\u8005\u5728\u5229\u7528\u4e2d\u4f7f\u7528\u4efb\u610f\u7684\u3001\u5b89\u5168\u5173\u952e(security-critical)\u7684\u5e93\u51fd\u6570\uff0c\u800c\u4e0d\u9700\u8981\u77e5\u9053\u8fd9\u4e9b\u51fd\u6570\u5728\u7a0b\u5e8f\u5185\u5b58\u4e2d\u7684\u4f4d\u7f6e\u3002\u800c\u5728\u4ee5\u524d\uff0c\u5b9e\u73b0\u8fd9\u79cd\u5229\u7528\u5219\u9700\u8981\u5148\u8fdb\u884c\u4fe1\u606f\u6cc4\u6f0f\u8fd9\u4e00\u6b65\u9aa4\u3002<\/span><\/p>\n

            \u56e0\u4e3aLeakless\u4f7f\u7528\u7684\u662fELF\u4e8c\u8fdb\u5236\u683c\u5f0f\u89c4\u5b9a\u7684\u7279\u6027\uff0c\u6240\u4ee5\u653b\u51fb\u80fd\u591f\u8de8\u67b6\u6784\uff0c\u8de8\u64cd\u4f5c\u7cfb\u7edf\uff0c\u8de8\u52a8\u6001\u88c5\u8f7d\u5668\u6765\u8fdb\u884c\u3002\u6b64\u5916\uff0c\u6211\u4eec\u5c55\u793a\u4e86\u6211\u4eec\u7684\u6280\u672f\u80fd\u591f\u7ed5\u8fc7\u50cfRELRO\u8fd9\u79cd\u4fdd\u62a4\u52a8\u6001\u89e3\u6790\u8fc7\u7a0b\u4e2d\u91cd\u8981\u63a7\u5236\u7ed3\u6784\u7684\u52a0\u56fa\u65b9\u6848\u3002\u6700\u540e\uff0c\u6211\u4eec\u63d0\u51fa\u4e86\u51e0\u79cd\u5bf9\u6297Leakless\u7684\u63aa\u65bd\uff0c\u5e76\u8ba8\u8bba\u4e86\u5b83\u4eec\u7684\u4f18\u7f3a\u70b9\u3002<\/span><\/p>\n

            ========================================================================<\/span><\/p>\n

            \u53c2\u8003\u6587\u732e<\/strong><\/p>\n

            [1] AppArmor. http:\/\/wiki.apparmor.net\/.<\/span><\/p>\n

            [2] A. Arcangeli. seccomp. https:\/\/www.kernel.org\/doc\/Documentation\/prctl\/seccomp_filter.txt.<\/span><\/p>\n

            [3] A. Baratloo, N. Singh, and T. K. Tsai. Transparent Run-Time Defense Against Stack-Smashing Attacks. In USENIX Annual Technical Conference, General Track, pages 251\u2013262, 2000.<\/span><\/p>\n

            [4] M. Bauer. Paranoid penguin: an introduction to Novell AppArmor. Linux Journal, 2006(148):13, 2006.<\/span><\/p>\n

            [5] A. Bittau, A. Belay, A. Mashtizadeh, D. Mazieres, and D. Boneh. Hacking blind. In Proceedings of the 35th IEEE Symposium on Security and Privacy, 2014.<\/span><\/p>\n

            [6] S. K. Cha, T. Avgerinos, A. Rebert, and D. Brumley. Unleashing mayhem on binary code. In Security and Privacy (SP), 2012 IEEE Symposium on, pages 380\u2013394. IEEE, 2012.<\/span><\/p>\n

            [7] Common Vulnerabilities and Exposures. CVE-2014-2299. http:\/\/cve.mitre.org\/cgi-bin\/cvename.cgi?name=CVE-2014-2299.<\/span><\/p>\n

            [8] C. Cowan, P. Wagle, C. Pu, S. Beattie, and J. Walpole. Buffer overflows: Attacks and defenses for the vulnerability of the decade. In DARPA Information Survivability Conference and Exposition, 2000. DISCEX\u201900. Proceedings, volume 2, pages 119\u2013129. IEEE, 2000.<\/span><\/p>\n

            [9] CVEDetails.com. ffmpeg: CVE security vulnerabilities. http:\/\/www.cvedetails.com\/product\/6315\/Ffmpeg-Ffmpeg.html.<\/span><\/p>\n

            [10] CVEDetails.com. Libpng: Security Vulnerabilities. http:\/\/www.cvedetails.com\/vendor\/7294\/Libpng.html.<\/span><\/p>\n

            [11] CVEDetails.com. Libtiff: CVE security vulnerabilities. http:\/\/www.cvedetails.com\/product\/3881\/Libtiff-Libtiff.html. <\/span><\/p>\n

            [12] CVEDetails.com. Wireshark: CVE security vulnerabilities. http:\/\/www.cvedetails.com\/product\/8292\/Wireshark-Wireshark.html.<\/span><\/p>\n

            [13] CWE. CWE\/SANS Top 25 Most Dangerous Software Errors. http:\/\/cwe.mitre.org\/top25\/.<\/span><\/p>\n

            [14] N. V. Database. NVD – Detail – CVE-2013-6487. http:\/\/web.nvd.nist.gov\/view\/vuln\/detail?vulnId=CVE-2013-6487.<\/span><\/p>\n

            [15] A. Di Federico, A. Cama, Y. Shoshitaishvili, C. Kruegel, and G. Vigna. Leakless source code repository. https:\/\/github.com\/ucsb-seclab\/leakless.<\/span><\/p>\n

            [16] S. Dudek. The Art Of ELF: Analysis and Exploitations. http:\/\/bit.ly\/1a8MeEw.<\/span><\/p>\n

            [17] T. Dullien, T. Kornau, and R.-P. Weinmann. A Framework for Automated Architecture-Independent Gadget Search. In WOOT, 2010.<\/span><\/p>\n

            [18] M. Fox, J. Giordano, L. Stotler, and A. Thomas. Selinux and grsecurity: A case study comparing linux security kernel enhancements. 2009.<\/p>\n

            [19] I. Haller, A. Slowinska, M. Neugschwandtner, and H. Bos. Dowsing for Overflows: A Guided Fuzzer to Find Buffer Boundary Violations. In USENIX Security, pages 49\u201364, 2013.<\/span><\/p>\n

            [20] C. Heitman and I. Arce. BARFgadgets. https:\/\/github.com\/programa-stic\/barf-project\/tree\/master\/barf\/tools\/gadgets.<\/p>\n

            [21] inaz2. ROP Illmatic: Exploring Universal ROP on glibc x86-64. http:\/\/ja.avtokyo.org\/avtokyo2014\/speakers#inaz2.<\/span><\/p>\n

            [22] P. Kot. A Turing complete ROP compiler. https:\/\/github.com\/pakt\/ropc.<\/span><\/p>\n

            [23] P. Menage. Cgroups. Available on-line at: http:\/\/www.mjmwired.net\/kernel\/Documentation\/cgroups.txt, 2008.<\/p>\n

            [24] Mozilla. SSL_CipherPrefSetDefault. https:\/\/developer.mozilla.org\/en-US\/docs\/Mozilla\/Projects\/NSS\/SSL_functions\/sslfnc.html#_SSL_CipherPrefSetDefault_.<\/span><\/p>\n

            [25] National Security Agency. Security-Enhanced Linux. http:\/\/selinuxproject.org\/.<\/span><\/p>\n

            [26] Nokia. Symbian OS Internals – The Loader. http:\/\/developer.nokia.com\/community\/wiki\/Symbian_OS_Internals\/10._The_ Loader#The_loader_server.<\/span><\/p>\n

            [27] H. Orman. The Morris worm: a fifteen-year perspective. IEEE Security & Privacy, 1(5):35\u201343, 2003.<\/span><\/p>\n

            [28] M. Payer. Too much PIE is bad for performance. 2012. https:\/\/nebelwelt.net\/publications\/12TRpie\/gccPIE-TR120614.pdf.<\/span><\/p>\n

            [29] M. Payer, T. Hartmann, and T. R. Gross. Safe Loading – A Foundation for Secure Execution of Untrusted Programs. In Proceedings of the 2012 IEEE Symposium on Security and Privacy, SP \u201912, pages 18\u201332, Washington, DC, USA, 2012. IEEE Computer Society.<\/span><\/p>\n

            [30] Phrack. Phrack – Volume 0xB, Issue 0x3a. http:\/\/phrack.org\/issues\/58\/4.html.<\/span><\/p>\n

            [31] Rapid7, Inc. The Metasploit Framework. http:\/\/www.metasploit.com\/.<\/span><\/p>\n

            [32] RedHat, Inc. Huge Pages and Transparent Huge Pages. https:\/\/access.redhat.com\/documentation\/en-US\/Red_Hat_ Enterprise_Linux\/6\/html\/Performance_Tuning_Guide\/s-memory-transhuge.html.<\/span><\/p>\n

            [33] Santa Cruz Operation. System V Application Binary Interface, 2013. http:\/\/www.sco.com\/developers\/gabi\/latest\/contents.html.<\/span><\/p>\n

            [34] E. J. Schwartz, T. Avgerinos, and D. Brumley. Q: Exploit Hardening Made Easy. In USENIX Security Symposium, 2011.<\/span><\/p>\n

            [35] H. Shacham. The geometry of innocent flesh on the bone: Return-into-libc without function calls (on the\u00a0<\/span>x86). In Proceedings of the 14th ACM conference on Computer and communications security, pages 552\u2013561. ACM, 2007.<\/span><\/p>\n

            [36] R. Shapiro, S. Bratus, and S. W. Smith. \u201dWeird Machines\u201d in ELF: A Spotlight on the Underappreciated Metadata. In Proceedings of the 7th USENIX Conference on Offensive Technologies, WOOT\u201913, pages 11\u201311, Berkeley, CA, USA, 2013. USENIX Association.<\/span><\/p>\n

            [37] L. Szekeres, M. Payer, T. Wei, and D. Song. SoK: Eternal war in memory. In Security and Privacy (SP), 2013 IEEE Symposium on, pages 48\u201362. IEEE, 2013.<\/span><\/p>\n

            [38] The Avalanche Project. Avalange – a dynamic defect detection tool. https:\/\/code.google.com\/p\/avalanche\/.<\/span><\/p>\n

            [39] M. Tran, M. Etheridge, T. Bletsch, X. Jiang, V. Freeh, and P. Ning. On the Expressiveness of Return-into-libc Attacks. In Proceedings of the 14th International Conference on Recent Advances in Intrusion Detection, RAID\u201911, pages 121\u2013141, Berlin, Heidelberg, 2011. Springer-Verlag.<\/span><\/p>\n

            [40] Ubuntu. Ubuntu Wiki – Security\/Features. https:\/\/wiki.ubuntu.com\/Security\/Features#Built_as_PIE.<\/span><\/p>\n

            [41] R. N. Watson, J. Anderson, B. Laurie, and K. Kenn-away. Capsicum: Practical Capabilities for UNIX. In USENIX Security Symposium, pages 29\u201346, 2010.<\/span><\/p>\n

            ========================================================================<\/span><\/p>\n

            \u9644\u5f55A \u7b26\u53f7\u7248\u672c\u5e26\u6765\u7684\u6311\u6218<\/span><\/p>\n

            \u57283.4\u8282\u4e2d\u6211\u4eec\u4ecb\u7ecd\u4e86\u7b26\u53f7\u7248\u672c\u7684\u6982\u5ff5\uff0c\u57284.2\u8282\u4e2d\u6211\u4eec\u63d0\u5230\u4e86\u5b83\u7684\u4f7f\u7528\u8ba9Elf_Rel.r_info\u7684\u542b\u4e49\u6709\u4e86\u65b0\u7684\u9650\u5236\u3002\u5728\u672c\u9644\u5f55\u4e2d\u6211\u4eec\u4f1a\u5217\u51fa\u8fd9\u51e0\u4e2a\u9650\u5236\uff0c\u5e76\u89e3\u91caLeakless\u5982\u4f55\u81ea\u52a8\u5730\u68c0\u9a8c\u5e76\u6ee1\u8db3\u5b83\u4eec\u3002<\/span><\/p>\n

            A.1 \u7b26\u53f7\u7248\u672c\u7684\u9650\u5236<\/span><\/p>\n

            \u5f53\u7b26\u53f7\u7248\u672c\u4f7f\u7528\u65f6\uff0cElf_Rel.info\u57df\u5c06\u540c\u65f6\u4f5c\u4e3a\u52a8\u6001\u7b26\u53f7\u8868\u7684\u4e0b\u6807\u4ee5\u53ca\u7b26\u53f7\u7248\u672c\u8868(.gnu.version\u6bb5)\u7684\u4e0b\u6807\u3002\u7b26\u53f7\u7248\u672c\u8868\u7531Elf_Verneed\u503c\u6784\u6210\uff0c\u4e00\u4e2a0\u503c\u62161\u503c\u6709\u7740\u7279\u6b8a\u7684\u542b\u4e49\uff0c\u5b83\u80fd\u591f\u505c\u6b62\u7b26\u53f7\u7248\u672c\u7684\u8fc7\u7a0b\uff0c\u8fd9\u5bf9\u653b\u51fb\u8005\u6765\u8bf4\u518d\u597d\u4e0d\u8fc7\u4e86\u3002<\/span><\/p>\n

            \u4e3a\u4e86\u7406\u89e3\u8fd9\u4e9b\u9650\u5236\u5230\u5e95\u662f\u600e\u6837\u7684\uff0c\u6211\u4eec\u5c06\u5f15\u5165\u4e00\u4e9b\u5b9a\u4e49\u548c\u547d\u540d\u89c4\u5219\u3002idx\u4e3aLeakless\u8ba1\u7b97\u51fa\u7684Elf_Rel.r_info\u503c\u6240\u6307\u793a\u7684\u4e0b\u6807\uff0cbaseof(x)\u51fd\u6570\u80fd\u591f\u8fd4\u56de\u6bb5x\u7684\u57fa\u5730\u5740\uff0csizeof(y)\u8fd4\u56de\u7ed3\u6784\u4f53y\u7684\u5927\u5c0f\uff0c*\u662f\u6307\u9488\u89e3\u5f15\u7528\u64cd\u4f5c(\u5373\u53d6\u503c)\u3002\u6211\u4eec\u5b9a\u4e49\u4e86\u5982\u4e0b\u53d8\u91cf\uff1a<\/span><\/p>\n

            sym = baseof(.dynsym) + idx \u00b7 sizeof(Elf Sym)<\/span><\/p>\n

            ver = baseof(.gnu.version) + idx \u00b7 sizeof(Elf Verneed)<\/span><\/p>\n

            verdef = baseof(.gnu.version_r) + *(ver) \u00b7 sizeof(Elf Verdef)<\/span><\/p>\n

            \u4e3a\u4e86\u80fd\u591f\u8fdb\u884c\u653b\u51fb\uff0c\u9700\u8981\u6ee1\u8db3\u4e0b\u9762\u7684\u6761\u4ef6:<\/span><\/p>\n

              \n
            1. sym\u6307\u5411\u653b\u51fb\u8005\u63a7\u5236\u7684\u4e00\u5757\u5185\u5b58\u533a\u57df\uff0c\u5e76\u4e14<\/span><\/li>\n
            2. \u4e0b\u9762\u7684\u67d0\u4e00\u6761\u80fd\u591f\u6ee1\u8db3:<\/span><\/li>\n<\/ol>\n

              \u00a0(a) ver\u6307\u5411\u5305\u542b\u4e00\u4e2a0\u6216\u8005\u4e00\u4e2a1\u7684\u5185\u5b58\u533a\u57df\uff0c\u6216<\/span><\/p>\n

              \u00a0(b) ver\u6307\u5411\u653b\u51fb\u8005\u63a7\u5236\u7684\u5185\u5b58\u533a\u57df\uff0c\u90a3\u91cc\u4f1a\u88ab\u5199\u4e0a0\u503c\uff0c\u6216<\/span><\/p>\n

              \u00a0(c) verdef\u6307\u5411\u653b\u51fb\u8005\u63a7\u5236\u7684\u5185\u5b58\u533a\u57df\uff0c\u5728\u90a3\u91cc\u5c06\u4f1a\u653e\u4e0a\u4e00\u4e2a\u6b63\u786e\u6784\u9020\u7684Elf_Verdef\u7ed3\u6784\u3002<\/span><\/p>\n

              \u5982\u679c\u4e0d\u80fd\u6ee1\u8db3\u4e0a\u8ff0\u6761\u4ef6\u5c06\u4f1a\u51fa\u73b0\u8bbf\u95ee\u4e00\u6bb5\u672a\u88ab\u6620\u5c04\u7684\u5185\u5b58\u533a\u57df\u6216\u8005\u7b26\u53f7\u89e3\u6790\u8fc7\u7a0b\u5931\u8d25\u7684\u73b0\u8c61\uff0c\u5e76\u6700\u7ec8\u8ba9\u7a0b\u5e8f\u7ec8\u6b62\u3002<\/span><\/p>\n

              Leakless\u53ef\u4ee5\u5728\u5927\u591a\u6570\u60c5\u51b5\u4e0b\u81ea\u52a8\u6ee1\u8db3\u8fd9\u4e9b\u9650\u5236\u3002\u4e00\u4e2a\u5178\u578b\u7684\u6210\u529f\u60c5\u5f62\u5c31\u662f\u8ba9idx\u503c\u6307\u5411\u4e00\u4e2a\u503c\u4e3a0\u7684\u7248\u672c\u4e0b\u6807\u6216\u8005\u5728.text\u6bb5\u4e2d(\u5b83\u5927\u591a\u8ddf\u5728.gnu.version\u6bb5\u540e\u9762)\uff0c\u5e76\u6307\u5411\u4e00\u4e2a.data\u548c.bss\u6bb5\u4e2d\u7b26\u53f7\u3002\u4e00\u4e2a\u503c\u5f97\u6ce8\u610f\u7684\u4f8b\u5916\u662fx86-64\u67b6\u6784\u4e0b\u652f\u6301huge pages\u7684ELF\u4e8c\u8fdb\u5236\u6587\u4ef6 [32]\u3002\u4f7f\u7528huge pages\u610f\u5473\u7740\u5185\u5b58\u9875\u662f\u4ee52MB\u7684\u8fb9\u754c\u5bf9\u9f50\u7684\uff0c\u6240\u4ee5\u5305\u542b\u53ea\u8bfb\u6bb5(\u7279\u522b\u662f.gun.version\u548c.text)\u7684segment\u4e0e\u53ef\u5199\u7684segment(\u542b\u6709.bss\u548c.data)\u79bb\u5f97\u5f88\u8fdc\u3002\u8fd9\u5c31\u8ba9\u627e\u5230\u4e00\u4e2a\u5408\u9002\u7684idx\u503c\u53d8\u5f97\u5f88\u96be\u3002<\/span><\/p>\n

              A.2 huge page\u7684\u95ee\u9898<\/span><\/p>\n

              huge page\u7684\u6548\u679c\u5982\u4e0b\u9762\u4f8b\u5b50\u6240\u793a:<\/span><\/p>\n

              “`<\/span><\/p>\n

              $ readelf –wide -l elf-without-huge-pages<\/span><\/p>\n

              Program Headers :<\/span><\/p>\n

              Type \u00a0\u00a0\u00a0VirtAddr \u00a0\u00a0\u00a0MemSiz \u00a0\u00a0\u00a0\u00a0\u00a0Flg Align<\/span><\/p>\n

              …<\/span><\/p>\n

              LOAD \u00a0\u00a0\u00a00x00400000 \u00a00x006468 \u00a0\u00a0\u00a0R E 0x1000<\/span><\/p>\n

              LOAD \u00a0\u00a0\u00a00x00407480 \u00a00x0005d0 \u00a0\u00a0\u00a0RW \u00a00x1000<\/span><\/p>\n

              …<\/span><\/p>\n

              $ readelf –wide -l elf-with-huge-pages<\/span><\/p>\n

              Program Headers :<\/span><\/p>\n

              Type \u00a0\u00a0\u00a0VirtAddr \u00a0\u00a0\u00a0MemSiz \u00a0\u00a0\u00a0\u00a0\u00a0Flg Align<\/span><\/p>\n

              …<\/span><\/p>\n

              LOAD \u00a0\u00a0\u00a00x00400000 \u00a00x00610c \u00a0\u00a0\u00a0R E 0x200000<\/span><\/p>\n

              LOAD \u00a0\u00a0\u00a00x00606e10 \u00a00x0005d0 \u00a0\u00a0\u00a0RW \u00a00x200000<\/span><\/p>\n

              …<\/span><\/p>\n

              “`<\/span><\/p>\n

              \u5728\u7b2c\u4e00\u4e2a\u4f8b\u5b50\u91cc\u53ef\u5199\u7684segments\u4e0e\u7a0b\u5e8f\u5f00\u5934\u7684\u8ddd\u79bb\u662f\u4ee5KB\u8ba1\u7684\uff0c\u4f46\u5982\u679c\u7528\u4e86huge pages\u8ddd\u79bb\u5c31\u8d85\u8fc7\u4e862MB\uff0c\u8fd9\u6837\u5c31\u65e0\u6cd5\u627e\u5230\u4e00\u4e2a\u6709\u6548\u7684idx\u503c\u4e86\u3002<\/span><\/p>\n

              \u5bf9\u4e8e\u8fd9\u4e2a\u95ee\u9898\uff0c\u53ef\u4ee5\u4f7f\u7528\u4e24\u79cd\u65b9\u6cd5\u89e3\u51b3\u3002<\/span><\/p>\n

              \u7b2c\u4e00\u79cd\u9009\u62e9\u662f\u5728\u53ea\u8bfb\u7684segment(\u4e00\u822c\u662f.text\u6bb5)\u4e2d\u4e3aElf_Verneed\u627e\u5230\u4e00\u4e2a0\u503c\u3002\u4ee4ro_start, ro_end, ro_size\u5206\u522b\u4e3a\u53ea\u8bfbsegment\u7684\u5f00\u59cb\u5730\u5740\uff0c\u7ed3\u675f\u5730\u5740\u4ee5\u53ca\u5927\u5c0f\uff0crw_start, rw_end, rw_size\u4e3a\u53ef\u5199segment\u7684\u5bf9\u5e94\u503c\u3002\u90a3\u4e48\u5b83\u4eec\u9700\u8981\u6ee1\u8db3\u4ee5\u4e0b\u6761\u4ef6:<\/span><\/p>\n

              ro_start \u2264 ver < ro_end<\/span><\/p>\n

              rw_start \u2264 sym < rw_end<\/span><\/p>\n

              \u8fd9\u91cc\uff0c\u6700\u96be\u6ee1\u8db3\u7684\u662f.dynsym\u6216.gnu.version\u4f4d\u4e8ero_start\u7684\u5f00\u5934\u7684\u60c5\u51b5\u3002\u5047\u8bbe\u4e0a\u8ff0\u4e24\u6761\u90fd\u80fd\u6ee1\u8db3\uff0c\u6211\u4eec\u5c31\u6709:<\/span><\/p>\n

              idx \u00b7 sizeof(Elf_Verneed) < ro end \u2212 ro start<\/span><\/p>\n

              idx \u00b7 sizeof(Elf_Sym) \u2265 rw start \u2212 ro start<\/span><\/p>\n

              \u4e5f\u5c31\u662f:<\/span><\/p>\n

              idx \u00b7 sizeof(Elf_Verneed) < ro size<\/span><\/p>\n

              idx \u00b7 sizeof (Elf_Sym) \u2265 2 MiB<\/span><\/p>\n

              \u6211\u4eec\u77e5\u9053Elf_Verneed\u548cElf_Sym\u572864\u4f4dELF\u4e2d\u5404\u53602\u4e2a\u5b57\u8282\u4e0e24\u4e2a\u5b57\u8282\uff0c\u6211\u4eec\u53ef\u4ee5\u8ba1\u7b97\u6ee1\u8db3\u8fd9\u4e2a\u4e0d\u7b49\u5f0f\u7ec4\u6761\u4ef6\u4e0bro_size\u7684\u6700\u5c0f\u503c\u3002\u7ed3\u679c\u662f170.7KB\u3002\u5982\u679c.rodata\u6bb5\u5c0f\u4e8e\u8fd9\u4e2a\u5927\u5c0f\uff0c\u90a3\u5c31\u5fc5\u987b\u4f7f\u7528\u5176\u4ed6\u65b9\u6cd5\u3002<\/span><\/p>\n

              \u7b2c\u4e8c\u79cd\u9009\u62e9\u662f\u5c06Elf_Verneed\u653e\u7f6e\u4e8e\u53ef\u5199\u7684segment\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0c\u653b\u51fb\u7684\u8981\u6c42\u4ee5\u4e0b\u9762\u7684\u4e0d\u7b49\u5f0f\u7ec4\u6765\u5b9a\u4e49:<\/span><\/p>\n

              rw_start \u2264 ver < rw_end<\/span><\/p>\n

              rw_start \u2264 sym < rw_end<\/span><\/p>\n

              \u5982\u679c\u6211\u4eec\u540c\u6837\u6765\u8003\u8651\u6700\u574f\u60c5\u51b5\u5e76\u4f5c\u51fa\u4e4b\u524d\u90a3\u6837\u7684\u5047\u8bbe\uff0c\u6211\u4eec\u5f97\u5230:<\/span><\/p>\n

              idx \u00b7 sizeof(Elf_Verneed) \u2265 rw_start \u2212 ro_start<\/span><\/p>\n

              idx \u00b7 sizeof(Elf_Sym) < rw_start \u2212 ro_start + rw_size<\/span><\/p>\n

              \u4e5f\u5c31\u662f:<\/span><\/p>\n

              idx \u00b7 sizeof(Elf_Verneed) \u2265 2 MiB<\/p>\n

              idx \u00b7 sizeof(Elf_Sym) < 2 MiB + rw_size<\/span><\/p>\n

              \u6211\u4eec\u73b0\u5728\u53ef\u4ee5\u8ba1\u7b97\u51fa\u80fd\u591f\u4f7f\u5176\u6210\u7acb\u7684\u53ef\u5199segment(rw_size)\u5927\u5c0f\u7684\u4e0b\u754c: 22MB\u3002\u7136\u800c\uff0c\u8fd9\u4e2a\u503c\u6ca1\u6709\u9053\u7406\u5730\u5927\uff0c\u5e76\u8ba9\u6211\u4eec\u5f97\u51fa\u7ed3\u8bba: \u8fd9\u79cd\u65b9\u6cd5\u5728\u4f7f\u7528huge pages\u7684\u5c0f\u578bELF\u6587\u4ef6\u4e2d\u662f\u4e0d\u9002\u7528\u7684<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

              \u4f5c\u8005\uff1aAlessandro Di Federico, Amat Cama, Yan Shoshita… Continue reading → <\/span><\/a><\/p>\n","protected":false},"author":4,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5],"tags":[],"class_list":["post-389","post","type-post","status-publish","format-standard","hentry","category-research"],"_links":{"self":[{"href":"http:\/\/202.112.238.40\/wp\/index.php?rest_route=\/wp\/v2\/posts\/389","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/202.112.238.40\/wp\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/202.112.238.40\/wp\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/202.112.238.40\/wp\/index.php?rest_route=\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"http:\/\/202.112.238.40\/wp\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=389"}],"version-history":[{"count":15,"href":"http:\/\/202.112.238.40\/wp\/index.php?rest_route=\/wp\/v2\/posts\/389\/revisions"}],"predecessor-version":[{"id":415,"href":"http:\/\/202.112.238.40\/wp\/index.php?rest_route=\/wp\/v2\/posts\/389\/revisions\/415"}],"wp:attachment":[{"href":"http:\/\/202.112.238.40\/wp\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=389"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/202.112.238.40\/wp\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=389"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/202.112.238.40\/wp\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=389"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}