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Use assert (!C)' instead of if (C) abort ();' in setuid wrappers.

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svn path=/nixos/trunk/; revision=10679
This commit is contained in:
Ludovic Courtès 2008-02-14 11:08:06 +00:00
parent a05d842575
commit bdc729ea6c
1 changed files with 19 additions and 23 deletions
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42
helpers/setuid/setuid-wrapper.c
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@ -6,6 +6,10 @@
#include <sys/stat.h>
#include <fcntl.h>
#include <dirent.h>
#include <assert.h>
/* Make sure assertions are not compiled out. */
#undef NDEBUG
extern char **environ;
@ -14,24 +18,19 @@ static char * wrapperDir = WRAPPER_DIR;
int main(int argc, char * * argv)
{
char self[PATH_MAX];
int len = readlink("/proc/self/exe", self, sizeof(self) - 1);
if (len == -1) abort();
assert (len > 0);
self[len] = 0;
//printf("self = %s, ch = %c\n", self, self[strlen(wrapperDir)]);
/* Make sure that we are being executed from the right location,
i.e., `wrapperDir'. This is to prevent someone from
creating hard link `X' from some other location, along with a
false `X.real' file, to allow arbitrary programs from being
executed setuid. */
if ((strncmp(self, wrapperDir, sizeof(wrapperDir)) != 0) ||
(self[strlen(wrapperDir)] != '/'))
abort();
executed setuid. */
assert ((strncmp(self, wrapperDir, sizeof(wrapperDir)) == 0) &&
(self[strlen(wrapperDir)] == '/'));
/* Make *really* *really* sure that we were executed as `self',
and not, say, as some other setuid program. That is, our
effective uid/gid should match the uid/gid of `self'. */
@ -42,31 +41,28 @@ int main(int argc, char * * argv)
//printf("%d %d\n", st.st_uid, st.st_gid);
if ((st.st_mode & S_ISUID) != 0 &&
st.st_uid != geteuid())
abort();
assert ((st.st_mode & S_ISUID) == 0 ||
(st.st_uid == geteuid()));
if ((st.st_mode & S_ISGID) != 0 &&
st.st_gid != getegid())
abort();
assert ((st.st_mode & S_ISGID) == 0 ||
st.st_gid == getegid());
/* And, of course, we shouldn't be writable. */
if (st.st_mode & (S_IWGRP | S_IWOTH))
abort();
assert (!(st.st_mode & (S_IWGRP | S_IWOTH)));
/* Read the path of the real (wrapped) program from <self>.real. */
char realFN[PATH_MAX + 10];
if (snprintf(realFN, sizeof(realFN), "%s.real", self) >= sizeof(realFN))
abort();
int realFNSize = snprintf (realFN, sizeof(realFN), "%s.real", self);
assert (realFNSize < sizeof(realFN));
int fdSelf = open(realFN, O_RDONLY);
if (fdSelf == -1) abort();
assert (fdSelf != -1);
char real[PATH_MAX];
len = read(fdSelf, real, PATH_MAX);
if (len == -1) abort();
if (len == sizeof(real)) abort();
assert (len != -1);
assert (len < sizeof (real));
real[len] = 0;
close(fdSelf);