80 lines
2.1 KiB
C
80 lines
2.1 KiB
C
#include <stdlib.h>
|
|
#include <stdio.h>
|
|
#include <string.h>
|
|
#include <unistd.h>
|
|
#include <sys/types.h>
|
|
#include <sys/stat.h>
|
|
#include <fcntl.h>
|
|
#include <dirent.h>
|
|
|
|
extern char **environ;
|
|
|
|
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();
|
|
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();
|
|
|
|
|
|
/* 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'. */
|
|
//printf("%d %d\n", geteuid(), getegid());
|
|
|
|
struct stat st;
|
|
if (lstat(self, &st) == -1) abort();
|
|
|
|
//printf("%d %d\n", st.st_uid, st.st_gid);
|
|
|
|
if ((st.st_mode & S_ISUID) != 0 &&
|
|
st.st_uid != geteuid())
|
|
abort();
|
|
|
|
if ((st.st_mode & S_ISGID) != 0 &&
|
|
st.st_gid != getegid())
|
|
abort();
|
|
|
|
/* And, of course, we shouldn't be writable. */
|
|
if (st.st_mode & (S_IWGRP | S_IWOTH))
|
|
abort();
|
|
|
|
|
|
/* 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 fdSelf = open(realFN, O_RDONLY);
|
|
if (fdSelf == -1) abort();
|
|
|
|
char real[PATH_MAX];
|
|
len = read(fdSelf, real, PATH_MAX);
|
|
if (len == -1) abort();
|
|
if (len == sizeof(real)) abort();
|
|
real[len] = 0;
|
|
|
|
close(fdSelf);
|
|
|
|
//printf("real = %s, len = %d\n", real, len);
|
|
|
|
execve(real, argv, environ);
|
|
|
|
exit(1);
|
|
}
|