tools/examples/svnserve-sgid.c

   1 /*
   2  * Wrapper to run the svnserve process setgid.
   3  * The idea is to avoid the problem that some interpreters like bash
   4  * invoked by svnserve in hook scripts will reset the effective gid to
   5  * the real gid, nuking the effect of an ordinary setgid svnserve binary.
   6  * Sadly, to set the real gid portably, you need to be root, if only
   7  * for a moment.
   8  * Also smashes the environment to something known, so that games
   9  * can't be played to try to break the security of the hook scripts,
  10  * by setting IFS, PATH, and similar means.
  11  */
  12 /*
  13  * Written by Perry Metzger, and placed into the public domain.
  14  */
  15
  16 #include <stdio.h>
  17 #include <unistd.h>
  18
  19 #define REAL_PATH "/usr/bin/svnserve.real"
  20
  21 char *newenv[] = { "PATH=/bin:/usr/bin", "SHELL=/bin/sh", NULL };
  22
  23 int
  24 main(int argc, char **argv)
  25 {
  26         if (setgid(getegid()) == -1) {
  27                 perror("setgid(getegid())");
  28                 return 1;
  29         }
  30
  31         if (seteuid(getuid()) == -1) {
  32                 perror("seteuid(getuid())");
  33                 return 1;
  34         }
  35
  36         execve(REAL_PATH, argv, newenv);
  37         perror("attempting to exec " REAL_PATH " failed");
  38         return 1;
  39 }