1 /* $OpenBSD: setresuid.c,v 1.3 2021/12/15 18:42:38 anton Exp $ */
2 /*
3 * Written by Bret Stephen Lambert <blambert@openbsd.org> 2014
4 * Public Domain.
5 */
6
7 #include <sys/types.h>
8 #include <sys/signal.h>
9 #include <sys/proc.h>
10 #include <sys/sysctl.h>
11 #include <sys/wait.h>
12
13 #include <err.h>
14 #include <stdio.h>
15 #include <stdlib.h>
16 #include <pwd.h>
17 #include <unistd.h>
18
19 #include "setuid_regress.h"
20
21 int
main(int argc,const char * argv[])22 main(int argc, const char *argv[])
23 {
24 struct kinfo_proc kproc;
25 struct passwd *pw;
26 uid_t uid;
27
28 if ((pw = getpwnam(_SETUID_REGRESS_USER)) == NULL)
29 err(1, "unknown user \"%s\"", _SETUID_REGRESS_USER);
30
31 uid = getuid();
32
33 if (setresuid(pw->pw_uid, -1, -1) == -1)
34 err(1, "setuid 0");
35 checkuids(pw->pw_uid, uid, uid, "0");
36
37 /* should only respond to setuid upon exec */
38 if (issetugid())
39 errx(1, "process incorrectly marked as issetugid()");
40
41 if (read_kproc_pid(&kproc, getpid()) == -1)
42 err(1, "kproc read failed");
43
44 if (!(kproc.p_psflags & PS_SUGID))
45 errx(1, "PS_SUGID not set");
46 if (kproc.p_psflags & PS_SUGIDEXEC)
47 errx(1, "PS_SUGIDEXEC incorrectly set");
48
49 /* we should be able to roll back our uids for now */
50 if (setresuid(uid, -1, -1) == -1)
51 err(1, "setuid 1");
52 checkuids(uid, uid, uid, "1");
53
54 if (setresuid(-1, pw->pw_uid, -1) == -1)
55 err(1, "setuid 2");
56 checkuids(uid, pw->pw_uid, uid, "2");
57
58 /* we should be able to roll back our uids for now */
59 if (setresuid(-1, uid, -1) == -1)
60 err(1, "setuid 3");
61 checkuids(uid, uid, uid, "3");
62
63 /*
64 * after changing our saved uid, we should be able to change
65 * our real and effective uids to that of our saved uid,
66 * but not to anything else
67 */
68
69 if (setresuid(-1, -1, pw->pw_uid) == -1)
70 err(1, "setuid 4");
71 checkuids(uid, uid, pw->pw_uid, "4");
72
73 if (setresuid(pw->pw_uid, -1, -1) == -1)
74 err(1, "setuid 5");
75 checkuids(pw->pw_uid, uid, pw->pw_uid, "5");
76
77 if (setresuid(-1, pw->pw_uid, -1) == -1)
78 err(1, "setuid 6");
79 checkuids(pw->pw_uid, pw->pw_uid, pw->pw_uid, "6");
80
81 if (setresuid(uid, -1, -1) != -1)
82 errx(1, "incorrectly capable of setting real uid");
83 checkuids(pw->pw_uid, pw->pw_uid, pw->pw_uid, "7");
84
85 if (setresuid(-1, uid, -1) != -1)
86 errx(1, "incorrectly capable of setting effective uid");
87 checkuids(pw->pw_uid, pw->pw_uid, pw->pw_uid, "9");
88
89 if (setresuid(-1, -1, uid) != -1)
90 errx(1, "incorrectly capable of setting saved uid");
91 checkuids(pw->pw_uid, pw->pw_uid, pw->pw_uid, "9");
92
93 /* sanity-check use of -1 as noop */
94 if (setresuid(-1, -1, -1) == -1)
95 errx(1, "-1 not properly recognized as noop");
96 checkuids(pw->pw_uid, pw->pw_uid, pw->pw_uid, "9");
97
98 exit(0);
99 }
100