1 /*
2 * Copyright (c) 2004, 2005 Darren Tucker (dtucker at zip com au).
3 *
4 * Permission to use, copy, modify, and distribute this software for any
5 * purpose with or without fee is hereby granted, provided that the above
6 * copyright notice and this permission notice appear in all copies.
7 *
8 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15 */
16
17 #include <sys/types.h>
18
19 #include <errno.h>
20 #include <unistd.h>
21
22 int
setresuid(uid_t ruid,uid_t euid,uid_t suid)23 setresuid(uid_t ruid, uid_t euid, uid_t suid)
24 {
25 uid_t ouid;
26 int ret = -1;
27
28 /* Allow only the tested configuration. */
29 if (ruid != euid || euid != suid) {
30 errno = ENOSYS;
31 return -1;
32 }
33 ouid = getuid();
34
35 # if defined(HAVE_SETREUID) && !defined(BROKEN_SETREUID)
36 if ((ret = setreuid(euid, euid)) == -1)
37 return -1;
38 # else
39 # ifndef SETEUID_BREAKS_SETUID
40 if (seteuid(euid) == -1)
41 return -1;
42 # endif
43 if ((ret = setuid(ruid)) == -1)
44 return -1;
45 # endif
46
47 /*
48 * When real, effective and saved uids are the same and we have
49 * changed uids, sanity check that we cannot restore the old uid.
50 */
51 if (ruid == euid && euid == suid && ouid != ruid &&
52 setuid(ouid) != -1 && seteuid(ouid) != -1) {
53 errno = EINVAL;
54 return -1;
55 }
56
57 /*
58 * Finally, check that the real and effective uids are what we
59 * expect.
60 */
61 if (getuid() != ruid || geteuid() != euid) {
62 errno = EACCES;
63 return -1;
64 }
65
66 return ret;
67 }
68