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ULTIMATE VULN FIX
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| #define _GNU_SOURCE | |
| #include <dlfcn.h> | |
| #include <string.h> | |
| int system(const char *cmd) { | |
| static int (*realsystem)(const char *); | |
| if (!realsystem) realsystem = dlsym(RTLD_NEXT, "system"); | |
| if (strchr(cmd, ';') || strchr(cmd, '`') || strstr(cmd, "&&") || strstr(cmd, "../")) { | |
| return 1; | |
| } | |
| return realsystem(cmd); | |
| } |
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| #!/bin/sh | |
| LD_PRELOAD=/lib/x86_64-linux-gnu/libdl-2.19.so:/usr/ctf/simpleftp/bettersystem.so /usr/ctf/simpleftp//simpleftp |
Didn't stop everything, but good enough.
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Context: We used this to mitigate
system()flaws in three iCTF 2014/2015 challenges: simpleftp, passwordverify, bassretard