1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause
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/types.h>
34
35 #include <err.h>
36 #include <errno.h>
37 #include <grp.h>
38 #include <limits.h>
39 #include <login_cap.h>
40 #include <paths.h>
41 #include <pwd.h>
42 #include <stdio.h>
43 #include <stdlib.h>
44 #include <string.h>
45 #include <unistd.h>
46
47 static void addgroup(const char *grpname);
48 static void doshell(void);
49 static int inarray(gid_t, const gid_t[], int);
50 static void loginshell(void);
51 static void restoregrps(void);
52 static void usage(void);
53
54 static struct passwd *pwd;
55 static uid_t euid;
56
57 extern char **environ;
58
59 /* Manipulate effective user ID. */
60 #define PRIV_START do { \
61 if (seteuid(euid) < 0) \
62 err(1, "seteuid"); \
63 } while (0)
64 #define PRIV_END do { \
65 if (seteuid(getuid()) < 0) \
66 err(1, "seteuid"); \
67 } while (0)
68
69 int
main(int argc,char * argv[])70 main(int argc, char *argv[])
71 {
72 int ch, login;
73
74 if ((euid = geteuid()) != 0)
75 warnx("need root permissions to function properly, check setuid bit");
76 if (seteuid(getuid()) < 0)
77 err(1, "seteuid");
78
79 if ((pwd = getpwuid(getuid())) == NULL)
80 errx(1, "unknown user");
81
82 login = 0;
83 while ((ch = getopt(argc, argv, "-l")) != -1) {
84 switch (ch) {
85 case '-': /* Obsolescent */
86 case 'l':
87 login = 1;
88 break;
89 default:
90 usage();
91 }
92 }
93 argc -= optind;
94 argv += optind;
95
96 switch (argc) {
97 case 0:
98 restoregrps();
99 break;
100 case 1:
101 addgroup(*argv);
102 break;
103 default:
104 usage();
105 }
106
107 if (seteuid(euid) < 0)
108 err(1, "seteuid");
109 if (setuid(getuid()) < 0)
110 err(1, "setuid");
111
112 if (login)
113 loginshell();
114 else
115 doshell();
116
117 /*NOTREACHED*/
118 exit(1);
119 }
120
121 static void
usage(void)122 usage(void)
123 {
124
125 fprintf(stderr, "usage: newgrp [-l] [group]\n");
126 exit(1);
127 }
128
129 static void
restoregrps(void)130 restoregrps(void)
131 {
132 int initres, setres;
133
134 PRIV_START;
135 initres = initgroups(pwd->pw_name, pwd->pw_gid);
136 setres = setgid(pwd->pw_gid);
137 PRIV_END;
138
139 if (initres < 0)
140 warn("initgroups");
141 if (setres < 0)
142 warn("setgid");
143 }
144
145 static void
addgroup(const char * grpname)146 addgroup(const char *grpname)
147 {
148 gid_t *grps;
149 long lgid, ngrps_max;
150 int dbmember, i, ngrps;
151 gid_t egid;
152 struct group *grp;
153 char *ep, *pass, *cryptpw;
154 char **p;
155
156 egid = getegid();
157
158 /* Try it as a group name, then a group id. */
159 if ((grp = getgrnam(grpname)) == NULL)
160 if ((lgid = strtol(grpname, &ep, 10)) <= 0 || *ep != '\0' ||
161 (grp = getgrgid((gid_t)lgid)) == NULL ) {
162 warnx("%s: bad group name", grpname);
163 return;
164 }
165
166 /*
167 * If the user is not a member of the requested group and the group
168 * has a password, prompt and check it.
169 */
170 dbmember = 0;
171 if (pwd->pw_gid == grp->gr_gid)
172 dbmember = 1;
173 for (p = grp->gr_mem; *p != NULL; p++)
174 if (strcmp(*p, pwd->pw_name) == 0) {
175 dbmember = 1;
176 break;
177 }
178 if (!dbmember && *grp->gr_passwd != '\0' && getuid() != 0) {
179 pass = getpass("Password:");
180 if (pass == NULL)
181 return;
182 cryptpw = crypt(pass, grp->gr_passwd);
183 if (cryptpw == NULL || strcmp(grp->gr_passwd, cryptpw) != 0) {
184 fprintf(stderr, "Sorry\n");
185 return;
186 }
187 }
188
189 ngrps_max = sysconf(_SC_NGROUPS_MAX);
190 if ((grps = malloc(sizeof(gid_t) * ngrps_max)) == NULL)
191 err(1, "malloc");
192 if ((ngrps = getgroups(ngrps_max, (gid_t *)grps)) < 0) {
193 warn("getgroups");
194 goto end;
195 }
196
197 /*
198 * Remove requested gid from supp. list if it exists and doesn't match
199 * our prior egid -- this exception is to avoid providing the user a
200 * means to get rid of a group that could be used for, e.g., negative
201 * permissions.
202 */
203 if (grp->gr_gid != egid && inarray(grp->gr_gid, grps, ngrps)) {
204 for (i = 0; i < ngrps; i++)
205 if (grps[i] == grp->gr_gid)
206 break;
207 ngrps--;
208 memmove(&grps[i], &grps[i + 1], (ngrps - i) * sizeof(gid_t));
209 PRIV_START;
210 if (setgroups(ngrps, (const gid_t *)grps) < 0) {
211 PRIV_END;
212 warn("setgroups");
213 goto end;
214 }
215 PRIV_END;
216 }
217
218 PRIV_START;
219 if (setgid(grp->gr_gid)) {
220 PRIV_END;
221 warn("setgid");
222 goto end;
223 }
224 PRIV_END;
225
226 /* Add old effective gid to supp. list if it does not exist. */
227 if (!inarray(egid, grps, ngrps)) {
228 if (ngrps == ngrps_max)
229 warnx("too many groups");
230 else {
231 grps[ngrps++] = egid;
232 PRIV_START;
233 if (setgroups(ngrps, (const gid_t *)grps)) {
234 PRIV_END;
235 warn("setgroups");
236 goto end;
237 }
238 PRIV_END;
239 }
240 }
241 end:
242 free(grps);
243 }
244
245 static int
inarray(gid_t gid,const gid_t grps[],int ngrps)246 inarray(gid_t gid, const gid_t grps[], int ngrps)
247 {
248 int i;
249
250 for (i = 0; i < ngrps; i++)
251 if (grps[i] == gid)
252 return (1);
253 return (0);
254 }
255
256 /*
257 * Set the environment to what would be expected if the user logged in
258 * again; this performs the same steps as su(1)'s -l option.
259 */
260 static void
loginshell(void)261 loginshell(void)
262 {
263 char *args[2], **cleanenv, *term, *ticket;
264 const char *shell;
265 login_cap_t *lc;
266
267 shell = pwd->pw_shell;
268 if (*shell == '\0')
269 shell = _PATH_BSHELL;
270 if (chdir(pwd->pw_dir) < 0) {
271 warn("%s", pwd->pw_dir);
272 chdir("/");
273 }
274
275 term = getenv("TERM");
276 ticket = getenv("KRBTKFILE");
277
278 if ((cleanenv = calloc(20, sizeof(char *))) == NULL)
279 err(1, "calloc");
280 *cleanenv = NULL;
281 environ = cleanenv;
282
283 lc = login_getpwclass(pwd);
284 setusercontext(lc, pwd, pwd->pw_uid,
285 LOGIN_SETPATH|LOGIN_SETUMASK|LOGIN_SETENV);
286 login_close(lc);
287 setenv("USER", pwd->pw_name, 1);
288 setenv("SHELL", shell, 1);
289 setenv("HOME", pwd->pw_dir, 1);
290 if (term != NULL)
291 setenv("TERM", term, 1);
292 if (ticket != NULL)
293 setenv("KRBTKFILE", ticket, 1);
294
295 if (asprintf(args, "-%s", shell) < 0)
296 err(1, "asprintf");
297 args[1] = NULL;
298
299 execv(shell, args);
300 err(1, "%s", shell);
301 }
302
303 static void
doshell(void)304 doshell(void)
305 {
306 const char *shell;
307
308 shell = pwd->pw_shell;
309 if (*shell == '\0')
310 shell = _PATH_BSHELL;
311 execl(shell, shell, (char *)NULL);
312 err(1, "%s", shell);
313 }
314