1 /* $OpenBSD: doas.c,v 1.4 2019/10/21 03:14:53 tedu Exp $ */
2 /*
3 * Copyright (c) 2015 Ted Unangst <tedu@openbsd.org>
4 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17
18 #include <sys/types.h>
19 #include <sys/stat.h>
20
21 #include <limits.h>
22 #include <string.h>
23 #include <stdio.h>
24 #include <stdlib.h>
25 #include <err.h>
26 #include <unistd.h>
27 #include <pwd.h>
28 #include <grp.h>
29 #include <syslog.h>
30 #include <errno.h>
31
32 static void __dead
usage(void)33 usage(void)
34 {
35 fprintf(stderr, "usage: doas [-u user] command [args]\n");
36 exit(1);
37 }
38
39 static int
parseuid(const char * s,uid_t * uid)40 parseuid(const char *s, uid_t *uid)
41 {
42 struct passwd *pw;
43 const char *errstr;
44
45 if ((pw = getpwnam(s)) != NULL) {
46 *uid = pw->pw_uid;
47 if (*uid == UID_MAX)
48 return -1;
49 return 0;
50 }
51 *uid = strtonum(s, 0, UID_MAX - 1, &errstr);
52 if (errstr)
53 return -1;
54 return 0;
55 }
56
57 int
main(int argc,char ** argv)58 main(int argc, char **argv)
59 {
60 const char *cmd;
61 struct passwd *pw;
62 uid_t uid;
63 uid_t target = 0;
64 gid_t groups[1];
65 int ch;
66
67 setprogname("doas");
68
69 closefrom(STDERR_FILENO + 1);
70
71 uid = getuid();
72 if (uid != 0)
73 errc(1, EPERM, "root only");
74
75 while ((ch = getopt(argc, argv, "u:")) != -1) {
76 switch (ch) {
77 case 'u':
78 if (parseuid(optarg, &target) != 0)
79 errx(1, "unknown user");
80 break;
81 default:
82 usage();
83 break;
84 }
85 }
86 argv += optind;
87 argc -= optind;
88
89 if (!argc)
90 usage();
91
92 cmd = argv[0];
93
94 pw = getpwuid(target);
95 if (!pw)
96 errx(1, "no passwd entry for target");
97 groups[0] = pw->pw_gid;
98
99 if (setgroups(1, groups) ||
100 setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) ||
101 setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid))
102 err(1, "failed to change user");
103
104 execvp(cmd, argv);
105 if (errno == ENOENT)
106 errx(1, "%s: command not found", cmd);
107 err(1, "%s", cmd);
108 }
109