{"id":11,"date":"2022-03-21T22:29:00","date_gmt":"2022-03-21T14:29:00","guid":{"rendered":"https:\/\/fushuling.com\/?p=11"},"modified":"2023-01-24T05:06:17","modified_gmt":"2023-01-23T21:06:17","slug":"%e4%bb%8e%e8%99%8e%e7%ac%a6ctf-ezphp%e6%b5%85%e8%b0%88%e7%8e%af%e5%a2%83%e5%8f%98%e9%87%8f%e6%b3%a8%e5%85%a5%e4%b8%8elinux%e4%b8%b4%e6%97%b6%e6%96%87%e4%bb%b6%e5%88%a9%e7%94%a8","status":"publish","type":"post","link":"https:\/\/fushuling.com\/index.php\/2022\/03\/21\/%e4%bb%8e%e8%99%8e%e7%ac%a6ctf-ezphp%e6%b5%85%e8%b0%88%e7%8e%af%e5%a2%83%e5%8f%98%e9%87%8f%e6%b3%a8%e5%85%a5%e4%b8%8elinux%e4%b8%b4%e6%97%b6%e6%96%87%e4%bb%b6%e5%88%a9%e7%94%a8\/","title":{"rendered":"\u4ece\u864e\u7b26CTF-ezphp\u6d45\u8c08\u73af\u5883\u53d8\u91cf\u6ce8\u5165\u4e0eLinux\u4e34\u65f6\u6587\u4ef6\u5229\u7528"},"content":{"rendered":"\n

\u6bd4\u8d5b\u65f6\u7684\u9519\u8bef\u601d\u8def<\/h2>\n\n\n\n

\u8fdb\u5165\u8d5b\u9898\uff0c\u9898\u76ee\u5f88\u7b80\u5355\uff0c\u5c31\u662f\u4e00\u4e32php\u4ee3\u7801\uff0c\u4fd7\u8bdd\u8bf4\u7684\u5f88\u597d\uff0c\u8d8a\u7b80\u5355\u7684\u8d8a\u590d\u6742\uff0c\u6b64\u8bdd\u8bda\u4e0d\u6b3a\u6211\u4e5f\u3002<\/p>\n\n\n\n

<?php \nforeach($_REQUEST['envs'] as $key => $val) {putenv(\"{$key}={$val}\"); \n<?php (empty($_GET[\"env\"])) ? highlight_file(__FILE__) : putenv($_GET[\"env\"]) && system('echo hfctf2022');  \n?><\/code><\/pre>\n\n\n\n
\u5f53\u65f6\u6211\u7b2c\u4e00\u773c\u5c31\u770b\u5230\u4e86\u8fd9\u4e2asystem\u51fd\u6570\uff0c\u56e0\u4e3a\u5b83\u7528system\u8c03\u7528echo\u7684\u884c\u4e3a\u5b9e\u5728\u5947\u602a\uff0c\u6bd5\u7adf\u5728\u7cfb\u7edf\u4e2d\uff0csystem\u8fd9\u4e2a\u51fd\u6570\u662f\u975e\u5e38\u5371\u9669\u7684\uff0c\u5b83\u53ef\u4ee5\u4ee5root\u6743\u9650\u6267\u884c\u51e0\u4e4e\u4efb\u4f55\u4ee3\u7801\u3002\u800c\u642d\u8fc7\u535a\u5ba2\u7684\u4eba\u53ef\u80fd\u4f1a\u9047\u5230\u7531\u4e8e\u5b89\u5168\u539f\u56e0\u5bfc\u81f4putenv\u51fd\u6570\u88ab\u7981\u7528\uff0c\u670d\u52a1\u505c\u6446\u7684\u60c5\u51b5\u3002\u56e0\u4e3aputenv\u662f\u4e00\u79cd\u5371\u9669\u51fd\u6570\uff0c\u56e0\u4e3a\u5b83\u53ef\u4ee5\u8bbe\u7f6e\u73af\u5883\u53d8\u91cf\uff0c\u8fd9\u53ef\u80fd\u4f1a\u5bf9\u7cfb\u7edf\u670d\u52a1\u9020\u6210\u6bc1\u706d\u6027\u6253\u51fb\u3002\u56e0\u6b64\uff0c\u8fd9\u77ed\u77ed\u51e0\u884c\u4ee3\u7801\u7b80\u76f4\u662f\u5367\u9f99\u51e4\u96cf\u4e00\u76f8\u9022\u2014\u2014\u2014\u2014\u4fbf\u80dc\u4eba\u95f4\u65e0\u6570\u3002\u5927\u5bb6\u90fd\u611f\u89c9\u8fd9\u4e2a\u73a9\u610f\u513f\u663e\u7136\u6709\u5927\u95ee\u9898\uff0c\u4f46\u4e0d\u77e5\u9053\u600e\u4e48\u5229\u7528\u8fd9\u4e2a\u95ee\u9898\u4ee3\u7801\u3002<\/p>\n\n\n\n
\u6211\u5f53\u65f6\u7684\u9519\u8bef\u7684\u60f3\u6cd5\u662f\uff1a\u80fd\u4e0d\u80fd\u53c2\u8003CISCN-LoveMath\uff0c\u7528define\u4e4b\u7c7b\u7684\u65b9\u6cd5\u628ahfctf2022\u53d8\u6210get flag\uff0c\u8fd9\u6837system\u547d\u4ee4\u4e00\u8c03\u7528\uff0c\u5c31\u80fd\u76f4\u63a5echo flag\uff0c\u7686\u5927\u6b22\u559c\u3002\u4e0d\u8fc7\u8fd9\u4e2a\u9898\u5982\u679c\u771f\u90a3\u4e48\u7b80\u5355\u5c31\u4e0d\u4f1a\u5c06\u8fd1\u665a\u4e0a\u624d\u6709\u4e00\u8840\u4e86\u3002\u9996\u5148CISCN\u7684\u5173\u952e\u4ee3\u7801\u662f\uff1a<\/p>\n\n\n\n
eval('echo '.$content.';');<\/code><\/pre>\n\n\n\n
\u540c\u6837\u662f\u5371\u9669\u51fd\u6570\uff0c\u4f46\u8fd9\u91cc\u6211\u4eec\u7684\u6539\u53d8\u91cf\u662f$content\uff0c\u8fd9\u662f\u4e00\u4e2a\u53d8\u91cf\uff0c\u800c\u6211\u4eec\u90a3\u9053\u9898\u662f\u201decho hfctf2022\u201c,\u8fd9\u5c31\u662f\u4e00\u53e5\u7b80\u5355\u7684\u8bdd\uff0c\u5373\u4f7f\u6211\u4eec\u8fd0\u6c14\u597d\uff0c\u771f\u7684\u628ahfctf2022\u53d8\u6210\u4e86get flag\uff0c\u7ecf\u8fc7\u6211\u7684\u9a8c\u8bc1\uff0c\u6700\u540e\u7684\u7ed3\u679c\u4e5f\u53ea\u4f1a\u662f\u5728\u9875\u9762\u4e0a\u6253\u5370get flag\u7f62\u4e86\uff0c\u4e0d\u4f1a\u771f\u7684\u628a\u5b83\u5f53\u4f5c\u4e00\u4e2a\u547d\u4ee4\u6267\u884c\u3002<\/p>\n\n\n\n
\u4e0d\u8fc7\u6211\u4eec\u5b66\u6821\u7684\u5927\u4f6cyyz\u62ff\u4e86\u8fd9\u9053\u9898\u7684\u4e8c\u8840\uff0c\u4ece\u4ed6\u7684\u53e3\u4e2d\uff0c\u6211\u5f97\u5230\u4e86\u8fd9\u9053\u9898\u7684\u9884\u671f\u89e3\uff0c\u8fd9\u5176\u5b9e\u662f\u4e00\u9053\u73af\u5883\u53d8\u91cf\u6ce8\u5165\u9898\uff0c\u53c2\u8003\u5927\u4f6c\u7684\u535a\u5ba2<\/a><\/p>\n\n\n\n
\"\"<\/div><\/figure>\n\n\n\n
\u4ee3\u7801\u662f\u4e0d\u662f\u548c\u8fd9\u9053\u9898\u5f88\u76f8\u4f3c\uff1f\u786e\u5b9e\uff0c\u8fd9\u662f\u4e00\u9053\u73af\u5883\u53d8\u91cf\u6ce8\u5165\uff0c\u4ec0\u4e48easy php\uff0c\u7b11\u6b7b\ud83d\ude25\ud83d\ude25\ud83d\ude25\u501f\u7528\u8fd9\u4f4d\u5927\u4f6c\u7684\u8bdd\uff1a<\/p>\n\n\n\n
\n
\u5728\u6709\u4e0a\u4f20\u70b9\uff08\u65e0\u9700\u63a7\u5236\u6587\u4ef6\u540d\uff09\u7684\u60c5\u51b5\u4e0b\uff0c\u8fd9\u6bb5\u4ee3\u7801\u5176\u5b9e\u6bd4\u8f83\u7b80\u5355\u4e86\uff0c\u53ef\u4ee5\u76f4\u63a5\u7528LD_PRELOAD\u641e\u5b9a\u3002\u4e0a\u4f20\u4e00\u4e2a\u6587\u4ef6\u540d\u4e0d\u9650\u7684so\u6587\u4ef6\uff0c\u5982hj.jpg\uff0c\u53ef\u4ee5\u901a\u8fc7LD_PRELOAD=\/var\/www\/html\/uploads\/hj.jpg\u8fd9\u6837\u7684\u65b9\u6cd5\u52ab\u6301\u5e76\u6267\u884c\u4efb\u610f\u4ee3\u7801\u3002<\/p>\n<\/blockquote>\n\n\n\n
\u4ec0\u4e48\u662fLD_PRELOAD<\/h2>\n\n\n\n
LD_PRELOAD\u662fLinux\u7cfb\u7edf\u7684\u4e00\u4e2a\u73af\u5883\u53d8\u91cf\uff0c\u5b83\u53ef\u4ee5\u5f71\u54cd\u7a0b\u5e8f\u7684\u8fd0\u884c\u65f6\u7684\u94fe\u63a5\uff08Runtime linker\uff09\uff0c\u5b83\u5141\u8bb8\u4f60\u5b9a\u4e49\u5728\u7a0b\u5e8f\u8fd0\u884c\u524d\u4f18\u5148\u52a0\u8f7d\u7684\u52a8\u6001\u94fe\u63a5\u5e93\u3002\u8fd9\u4e2a\u529f\u80fd\u4e3b\u8981\u5c31\u662f\u7528\u6765\u6709\u9009\u62e9\u6027\u7684\u8f7d\u5165\u4e0d\u540c\u52a8\u6001\u94fe\u63a5\u5e93\u4e2d\u7684\u76f8\u540c\u51fd\u6570\u3002\u901a\u8fc7\u8fd9\u4e2a\u73af\u5883\u53d8\u91cf\uff0c\u6211\u4eec\u53ef\u4ee5\u5728\u4e3b\u7a0b\u5e8f\u548c\u5176\u52a8\u6001\u94fe\u63a5\u5e93\u7684\u4e2d\u95f4\u52a0\u8f7d\u522b\u7684\u52a8\u6001\u94fe\u63a5\u5e93\uff0c\u751a\u81f3\u8986\u76d6\u6b63\u5e38\u7684\u51fd\u6570\u5e93\u3002\u4e00\u65b9\u9762\uff0c\u6211\u4eec\u53ef\u4ee5\u4ee5\u6b64\u529f\u80fd\u6765\u4f7f\u7528\u81ea\u5df1\u7684\u6216\u662f\u66f4\u597d\u7684\u51fd\u6570\uff08\u65e0\u9700\u522b\u4eba\u7684\u6e90\u7801\uff09\uff0c\u800c\u53e6\u4e00\u65b9\u9762\uff0c\u6211\u4eec\u4e5f\u53ef\u4ee5\u4ee5\u5411\u522b\u4eba\u7684\u7a0b\u5e8f\u6ce8\u5165\u7a0b\u5e8f\uff0c\u4ece\u800c\u8fbe\u5230\u7279\u5b9a\u7684\u76ee\u7684\u3002<\/p>\n\n\n\n
\u7528\u4eba\u8bdd\u8bb2\uff0cLD_PRELOAD\uff0c\u662f\u4e2a\u73af\u5883\u53d8\u91cf\uff0c\u7528\u4e8e\u52a8\u6001\u5e93\u7684\u52a0\u8f7d\uff0c\u800c\u52a8\u6001\u5e93\u52a0\u8f7d\u7684\u4f18\u5148\u7ea7\u6700\u9ad8\uff0c\u56e0\u6b64\u6211\u4eec\u53ef\u4ee5\u62a2\u5148\u5728\u6b63\u5e38\u51fd\u6570\u6267\u884c\u4e4b\u524d\u7387\u5148\u6267\u884c\u6211\u4eec\u7684\u7528\u4ee3\u7801\u5199\u7684\u51fd\u6570\u3002\u501f\u7528\u5927\u4f6c\u7684\u535a\u5ba2<\/a>\u7684\u6f14\u793a\uff1a<\/p>\n\n\n\n
\u5047\u5982\u8fd9\u91cc\u6709\u4e2arandom.c\uff0c\u4ee3\u7801\u5982\u4e0b\uff1a<\/p>\n\n\n\n
#include <stdio.h>\n#include <stdlib.h>\n#include <time.h>\n\nint main(){\n  srand(time(NULL));\n  int i = 10;\n  while(i--) printf(\"%d\\n\",rand()%100);\n  return 0;\n}<\/code><\/pre>\n\n\n\n
\u6267\u884c\u7ed3\u679c\uff1a<\/p>\n\n\n\n
[root preload]#gcc -o random  random.c\n[root preload]#.\/random\n69\n36\n52\n0\n15\n24\n72\n34\n71\n84<\/code><\/pre>\n\n\n\n
\u5047\u5982\u8fd9\u91cc\u6709\u4e2aunrandom.c\uff0c\u4ee3\u7801\u4e3a\uff1a<\/p>\n\n\n\n
int rand(){
return 42; \/\/the most random number in the universe
}<\/code><\/pre>\n\n\n\n
\u7f16\u8bd1\u6210\u52a8\u6001\u5e93\uff1a<\/p>\n\n\n\n
gcc -shared -fPIC unrandom.c -o unrandom.so<\/code><\/pre>\n\n\n\n
\u7136\u540e\u8fd0\u884c<\/p>\n\n\n\n
LD_PRELOAD=$PWD\/unrandom.so .\/random_nums
\u6216\u8005
[root preload]#export LD_PRELOAD=$PWD\/unrandom.so
[root preload]#.\/random
\u8fd0\u884c\u7ed3\u679c\u5747\u4e3a:
42
42
42
42
42
42
42
42
42
42<\/code><\/pre>\n\n\n\n
\u795e\u5947\u7684\u4e00\u5e55\u53d1\u751f\u8fa3\uff01\u8fd0\u884c\u7ed3\u679c\u5168\u6210\u4e8642!<\/p>\n\n\n\n
\u4e0a\u9762\u7684\u4f8b\u5b50\u8bf4\u660e\uff0c\u6211\u4eec\u5df2\u7ecf\u6210\u529f\u5c06rand\u51fd\u6570\u66ff\u6362\u4e3a\u6211\u4eec\u81ea\u5df1\u6240\u7f16\u5199\u7684\u7248\u672c\u3002\u56e0\u4e3a\u6211\u4eec\u7684\u52a8\u6001\u5e93\u4f18\u5148\u7ea7\u662f\u6700\u9ad8\u7684\uff0c\u65e2\u7136\u5148return 42\uff0c\u90a3\u4e48\u4f18\u5148\u7ea7\u4f4e\u7684\u4ee3\u7801\u5c31\u5df2\u7ecf\u90fd\u88ab\u6211\u4eec\u8986\u76d6\u4e86\u3002\u56e0\u6b64\u5982\u5927\u4f6c\u6240\u8bf4\u7684\u90a3\u6837\uff0c\u6211\u4eec\u80fd\u5229\u7528LD_PRELOAD\u52ab\u6301\u5e76\u6267\u884c\u4efb\u610f\u4ee3\u7801\u3002\u4f46\u9057\u61be\u7684\u662f\uff0c\u8fd9\u91cc\u6ca1\u6709\u4e0a\u4f20\u70b9\uff0c\u6211\u4eec\u538b\u6839\u5c31\u4e0d\u53ef\u80fd\u6574\u4e2aLD_PRELOAD=\/var\/www\/html\/uploads\/hj.jpg\u4e0a\u53bb\u3002\u8fd9\u5c31\u662f\u5982\u4eca\u7684\u95ee\u9898\u6240\u5728\uff0c\u600e\u4e48\u5728\u6ca1\u6709\u7ed9\u4e0a\u4f20\u63a5\u53e3\u7684\u60c5\u51b5\u4e0bget shell\u3002<\/p>\n\n\n\n
Centos\u4e0b\u7684\u65e0\u53c2\u6570\u6ce8\u5165<\/h2>\n\n\n\n
\u5927\u4f6c\u5728\u63a5\u4e0b\u6765\u7684\u535a\u5ba2\u4e2d\u76f4\u63a5\u5206\u6790\u4e86PHP\u7684\u5e95\u5c42\u4ee3\u7801\uff0c\u5206\u6790PHP\u7684system\u51fd\u6570\u7684\u4ee3\u7801\uff08\u8fd9\u5c31\u662fLinux\u5185\u6838\u73a9\u5bb6\u5417\/(\u3112o\u3112)\/~~\uff09\uff0c\u7136\u540e\u53d1\u73b0PHP\u7684system\u8c03\u7528\u7684\u662f\u7cfb\u7edf\u7684popen()\uff0c\u7d27\u63a5\u7740\uff0c\u7ee7\u7eed\u5206\u6790popen\u7a76\u7adf\u5728\u505a\u4ec0\u4e48\u3002\u6700\u540e\uff0c\u5927\u4f6c\u53d1\u73b0\uff0cpopen()\u4ecd\u7136\u6ca1\u5b8c\uff0c\u8fd8\u5f97\u7ee7\u7eed\u5957\u5a03\u4e0b\u53bb\uff0c\u5b9e\u9645\u4e0apopen\u6700\u7ec8\u6267\u884c\u7684\u662fspawn_process\u51fd\u6570\uff1a<\/p>\n\n\n\n
static bool\nspawn_process (posix_spawn_file_actions_t *fa, FILE *fp, const char *command,\n           int do_cloexec, int pipe_fds[2], int parent_end, int child_end,\n           int child_pipe_fd)\n{\n\n  \/\/...\n\n  if (__posix_spawn (&((_IO_proc_file *) fp)->pid, _PATH_BSHELL, fa, 0,\n             (char *const[]){ (char*) \"sh\", (char*) \"-c\",\n             (char *) command, NULL }, __environ) != 0)\n    return false;\n\n  \/\/...\n\n  return true;\n}<\/code><\/pre>\n\n\n\n
\u4ece\u7b2c\u4e5d\u884c\u4ee3\u7801\u4e2d\uff0c\u6211\u4eec\u53d1\u73b0\uff0c\u6700\u7ec8\u6267\u884c\u7684\u662f“sh”, (char*) “-c”<\/strong>\uff0c\u5373\u547d\u4ee4sh -c “echo hello”<\/strong><\/p>\n\n\n\n
\u73b0\u5728\u6211\u4eec\u6765\u601d\u8003\uff0c\u6211\u53ef\u4ee5\u63a7\u5236\u6267\u884csh -c “echo hello”\u65f6\u7684\u73af\u5883\u53d8\u91cf\uff0c\u662f\u5426\u53ef\u4ee5getshell\uff1f<\/strong><\/p>\n\n\n\n
sh -c “echo hello”<\/strong>\u5b9e\u8d28\u4e0a\u6267\u884c\u4e86\u4e24\u4e2a\u4e8c\u8fdb\u5236\u6587\u4ef6\uff0c\u5373<\/p>\n\n\n\n