1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2002 Tim J. Robbins.
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29 /*
30 * newgrp -- change to a new group
31 */
32
33 #include <sys/cdefs.h>
34 __FBSDID("$FreeBSD$");
35
36 #include <sys/types.h>
37
38 #include <err.h>
39 #include <errno.h>
40 #include <grp.h>
41 #include <limits.h>
42 #include <login_cap.h>
43 #include <paths.h>
44 #include <pwd.h>
45 #include <stdio.h>
46 #include <stdlib.h>
47 #include <string.h>
48 #include <unistd.h>
49
50 static void addgroup(const char *grpname);
51 static void doshell(void);
52 static int inarray(gid_t, const gid_t[], int);
53 static void loginshell(void);
54 static void restoregrps(void);
55 static void usage(void);
56
57 static struct passwd *pwd;
58 static uid_t euid;
59
60 extern char **environ;
61
62 /* Manipulate effective user ID. */
63 #define PRIV_START do { \
64 if (seteuid(euid) < 0) \
65 err(1, "seteuid"); \
66 } while (0)
67 #define PRIV_END do { \
68 if (seteuid(getuid()) < 0) \
69 err(1, "seteuid"); \
70 } while (0)
71
72 int
main(int argc,char * argv[])73 main(int argc, char *argv[])
74 {
75 int ch, login;
76
77 if ((euid = geteuid()) != 0)
78 warnx("need root permissions to function properly, check setuid bit");
79 if (seteuid(getuid()) < 0)
80 err(1, "seteuid");
81
82 if ((pwd = getpwuid(getuid())) == NULL)
83 errx(1, "unknown user");
84
85 login = 0;
86 while ((ch = getopt(argc, argv, "-l")) != -1) {
87 switch (ch) {
88 case '-': /* Obsolescent */
89 case 'l':
90 login = 1;
91 break;
92 default:
93 usage();
94 }
95 }
96 argc -= optind;
97 argv += optind;
98
99 switch (argc) {
100 case 0:
101 restoregrps();
102 break;
103 case 1:
104 addgroup(*argv);
105 break;
106 default:
107 usage();
108 }
109
110 if (seteuid(euid) < 0)
111 err(1, "seteuid");
112 if (setuid(getuid()) < 0)
113 err(1, "setuid");
114
115 if (login)
116 loginshell();
117 else
118 doshell();
119
120 /*NOTREACHED*/
121 exit(1);
122 }
123
124 static void
usage(void)125 usage(void)
126 {
127
128 fprintf(stderr, "usage: newgrp [-l] [group]\n");
129 exit(1);
130 }
131
132 static void
restoregrps(void)133 restoregrps(void)
134 {
135 int initres, setres;
136
137 PRIV_START;
138 initres = initgroups(pwd->pw_name, pwd->pw_gid);
139 setres = setgid(pwd->pw_gid);
140 PRIV_END;
141
142 if (initres < 0)
143 warn("initgroups");
144 if (setres < 0)
145 warn("setgid");
146 }
147
148 static void
addgroup(const char * grpname)149 addgroup(const char *grpname)
150 {
151 gid_t *grps;
152 long lgid, ngrps_max;
153 int dbmember, i, ngrps;
154 gid_t egid;
155 struct group *grp;
156 char *ep, *pass, *cryptpw;
157 char **p;
158
159 egid = getegid();
160
161 /* Try it as a group name, then a group id. */
162 if ((grp = getgrnam(grpname)) == NULL)
163 if ((lgid = strtol(grpname, &ep, 10)) <= 0 || *ep != '\0' ||
164 (grp = getgrgid((gid_t)lgid)) == NULL ) {
165 warnx("%s: bad group name", grpname);
166 return;
167 }
168
169 /*
170 * If the user is not a member of the requested group and the group
171 * has a password, prompt and check it.
172 */
173 dbmember = 0;
174 if (pwd->pw_gid == grp->gr_gid)
175 dbmember = 1;
176 for (p = grp->gr_mem; *p != NULL; p++)
177 if (strcmp(*p, pwd->pw_name) == 0) {
178 dbmember = 1;
179 break;
180 }
181 if (!dbmember && *grp->gr_passwd != '\0' && getuid() != 0) {
182 pass = getpass("Password:");
183 if (pass == NULL)
184 return;
185 cryptpw = crypt(pass, grp->gr_passwd);
186 if (cryptpw == NULL || strcmp(grp->gr_passwd, cryptpw) != 0) {
187 fprintf(stderr, "Sorry\n");
188 return;
189 }
190 }
191
192 ngrps_max = sysconf(_SC_NGROUPS_MAX) + 1;
193 if ((grps = malloc(sizeof(gid_t) * ngrps_max)) == NULL)
194 err(1, "malloc");
195 if ((ngrps = getgroups(ngrps_max, (gid_t *)grps)) < 0) {
196 warn("getgroups");
197 goto end;
198 }
199
200 /* Remove requested gid from supp. list if it exists. */
201 if (grp->gr_gid != egid && inarray(grp->gr_gid, grps, ngrps)) {
202 for (i = 0; i < ngrps; i++)
203 if (grps[i] == grp->gr_gid)
204 break;
205 ngrps--;
206 memmove(&grps[i], &grps[i + 1], (ngrps - i) * sizeof(gid_t));
207 PRIV_START;
208 if (setgroups(ngrps, (const gid_t *)grps) < 0) {
209 PRIV_END;
210 warn("setgroups");
211 goto end;
212 }
213 PRIV_END;
214 }
215
216 PRIV_START;
217 if (setgid(grp->gr_gid)) {
218 PRIV_END;
219 warn("setgid");
220 goto end;
221 }
222 PRIV_END;
223 grps[0] = grp->gr_gid;
224
225 /* Add old effective gid to supp. list if it does not exist. */
226 if (egid != grp->gr_gid && !inarray(egid, grps, ngrps)) {
227 if (ngrps == ngrps_max)
228 warnx("too many groups");
229 else {
230 grps[ngrps++] = egid;
231 PRIV_START;
232 if (setgroups(ngrps, (const gid_t *)grps)) {
233 PRIV_END;
234 warn("setgroups");
235 goto end;
236 }
237 PRIV_END;
238 }
239 }
240 end:
241 free(grps);
242 }
243
244 static int
inarray(gid_t gid,const gid_t grps[],int ngrps)245 inarray(gid_t gid, const gid_t grps[], int ngrps)
246 {
247 int i;
248
249 for (i = 0; i < ngrps; i++)
250 if (grps[i] == gid)
251 return (1);
252 return (0);
253 }
254
255 /*
256 * Set the environment to what would be expected if the user logged in
257 * again; this performs the same steps as su(1)'s -l option.
258 */
259 static void
loginshell(void)260 loginshell(void)
261 {
262 char *args[2], **cleanenv, *term, *ticket;
263 const char *shell;
264 login_cap_t *lc;
265
266 shell = pwd->pw_shell;
267 if (*shell == '\0')
268 shell = _PATH_BSHELL;
269 if (chdir(pwd->pw_dir) < 0) {
270 warn("%s", pwd->pw_dir);
271 chdir("/");
272 }
273
274 term = getenv("TERM");
275 ticket = getenv("KRBTKFILE");
276
277 if ((cleanenv = calloc(20, sizeof(char *))) == NULL)
278 err(1, "calloc");
279 *cleanenv = NULL;
280 environ = cleanenv;
281
282 lc = login_getpwclass(pwd);
283 setusercontext(lc, pwd, pwd->pw_uid,
284 LOGIN_SETPATH|LOGIN_SETUMASK|LOGIN_SETENV);
285 login_close(lc);
286 setenv("USER", pwd->pw_name, 1);
287 setenv("SHELL", shell, 1);
288 setenv("HOME", pwd->pw_dir, 1);
289 if (term != NULL)
290 setenv("TERM", term, 1);
291 if (ticket != NULL)
292 setenv("KRBTKFILE", ticket, 1);
293
294 if (asprintf(args, "-%s", shell) < 0)
295 err(1, "asprintf");
296 args[1] = NULL;
297
298 execv(shell, args);
299 err(1, "%s", shell);
300 }
301
302 static void
doshell(void)303 doshell(void)
304 {
305 const char *shell;
306
307 shell = pwd->pw_shell;
308 if (*shell == '\0')
309 shell = _PATH_BSHELL;
310 execl(shell, shell, (char *)NULL);
311 err(1, "%s", shell);
312 }
313