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DropPriv: Really call seteuid and not setuid, and add more checks

The only thing we are missing is non-portable saved ids support.
debian/1.8.y
Julian Andres Klode 8 years ago
parent
commit
5f2047ece8
  1. 46
      apt-pkg/contrib/fileutl.cc

46
apt-pkg/contrib/fileutl.cc

@ -2175,9 +2175,12 @@ bool Popen(const char* Args[], FileFd &Fd, pid_t &Child, FileFd::OpenMode Mode)
bool DropPrivs()
{
if (getuid() != 0)
return true;
/* uid will be 0 in the end, but gid might be different anyway */
uid_t old_uid = getuid();
gid_t old_gid = getgid();
if (old_uid != 0)
return true;
if(_config->FindB("Debug::NoDropPrivs", false) == true)
return true;
@ -2197,22 +2200,43 @@ bool DropPrivs()
return _error->Errno("setgroups", "Failed to setgroups");
if (setegid(pw->pw_gid) != 0)
return _error->Errno("setgid", "Failed to setgid");
return _error->Errno("setegid", "Failed to setegid");
if (setgid(pw->pw_gid) != 0)
return _error->Errno("setgid", "Failed to setgid");
if (setuid(pw->pw_uid) != 0)
return _error->Errno("setuid", "Failed to setuid");
// the seteuid() is probably uneeded (at least thats what the linux
// man-page says about setuid(2)) but we cargo culted it anyway
if (setuid(pw->pw_uid) != 0)
return _error->Errno("setuid", "Failed to setuid");
// be defensive
if(setgid(0) != -1 || setegid(0) != -1)
return _error->Error("Could restore gid to root, privilege dropping does not work");
if(setuid(0) != -1 || seteuid(0) != -1)
return _error->Error("Could restore uid to root, privilege dropping does not work");
if (seteuid(pw->pw_uid) != 0)
return _error->Errno("seteuid", "Failed to seteuid");
/* Try changing GID/EGID */
if (pw->pw_gid != old_gid && (setgid(old_gid) != -1 || setegid(old_gid) != -1))
return _error->Error("Could restore a gid to root, privilege dropping did not work");
if (pw->pw_uid != old_uid && (setuid(old_uid) != -1 || seteuid(old_uid) != -1))
return _error->Error("Could restore a uid to root, privilege dropping did not work");
/* Verify the list of supplementary groups is what we expected */
gid_t groups[1];
if (getgroups(1, groups) != 1)
return _error->Errno("getgroups", "Could not get new groups");
if (groups[0] != pw->pw_gid)
return _error->Error("Could not switch group");
/* Verify gid, egid, uid, and euid */
if (getgid() != pw->pw_gid)
return _error->Error("Could not switch group");
if (getegid() != pw->pw_gid)
return _error->Error("Could not switch effective group");
if (getuid() != pw->pw_uid)
return _error->Error("Could not switch user");
if (geteuid() != pw->pw_uid)
return _error->Error("Could not switch effective user");
/* TODO: Check saved uid/saved gid as well */
return true;
}

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