1/*	$OpenBSD: setresgid.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
21int
22main(int argc, const char *argv[])
23{
24	struct kinfo_proc	 kproc;
25	struct passwd		*pw;
26	gid_t			 gid;
27
28	if ((pw = getpwnam(_SETUID_REGRESS_USER)) == NULL)
29		err(1, "unknown user \"%s\"", _SETUID_REGRESS_USER);
30
31	gid = getgid();
32
33	if (setresgid(pw->pw_gid, -1, -1) == -1)
34		err(1, "setgid 0");
35	checkgids(pw->pw_gid, gid, gid, "0");
36
37	/* should only respond to setgid 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 gids for now */
50	if (setresgid(gid, -1, -1) == -1)
51		err(1, "setgid 1");
52	checkgids(gid, gid, gid, "1");
53
54	if (setresgid(-1, pw->pw_gid, -1) == -1)
55		err(1, "setgid 2");
56	checkgids(gid, pw->pw_gid, gid, "2");
57
58	/* we should be able to roll back our gids for now */
59	if (setresgid(-1, gid, -1) == -1)
60		err(1, "setgid 3");
61	checkgids(gid, gid, gid, "3");
62
63	/*
64	 * after changing our saved gid and dropping superuser privs,
65	 * we should be able to change our real and effective gids to
66	 * that of our saved gid, but not to anything else
67	 */
68
69	if (setresgid(-1, -1, pw->pw_gid) == -1)
70		err(1, "setgid 4");
71	checkgids(gid, gid, pw->pw_gid, "4");
72
73	if (setresuid(pw->pw_gid, pw->pw_gid, pw->pw_gid) == -1)
74		err(1, "setresuid 4");
75
76	if (setresgid(pw->pw_gid, -1, -1) == -1)
77		err(1, "setgid 5");
78	checkgids(pw->pw_gid, gid, pw->pw_gid, "5");
79
80	if (setresgid(-1, pw->pw_gid, -1) == -1)
81		err(1, "setgid 6");
82	checkgids(pw->pw_gid, pw->pw_gid, pw->pw_gid, "6");
83
84	if (setresgid(gid, -1, -1) != -1)
85		errx(1, "incorrectly capable of setting real gid");
86	checkgids(pw->pw_gid, pw->pw_gid, pw->pw_gid, "7");
87
88	if (setresgid(-1, gid, -1) != -1)
89		errx(1, "incorrectly capable of setting effective gid");
90	checkgids(pw->pw_gid, pw->pw_gid, pw->pw_gid, "9");
91
92	if (setresgid(-1, -1, gid) != -1)
93		errx(1, "incorrectly capable of setting saved gid");
94	checkgids(pw->pw_gid, pw->pw_gid, pw->pw_gid, "9");
95
96	/* sanity-check use of -1 as noop */
97	if (setresgid(-1, -1, -1) == -1)
98		errx(1, "-1 not properly recognized as noop");
99	checkgids(pw->pw_gid, pw->pw_gid, pw->pw_gid, "9");
100
101	exit(0);
102}
103