1 /*-
2 * Copyright (c) 2002 Tim J. Robbins.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 *
26 * $FreeBSD: /src/usr.bin/newgrp/newgrp.c,v 1.2 2003/10/30 15:14:34 harti Exp $
27 * $DragonFly: src/usr.bin/newgrp/newgrp.c,v 1.3 2004/12/08 22:26:42 liamfoy Exp $
28 */
29
30 /*
31 * newgrp -- change to a new group
32 */
33
34 #include <sys/types.h>
35
36 #include <err.h>
37 #include <errno.h>
38 #include <grp.h>
39 #include <libgen.h>
40 #include <limits.h>
41 #include <login_cap.h>
42 #include <paths.h>
43 #include <pwd.h>
44 #include <stdio.h>
45 #include <stdlib.h>
46 #include <string.h>
47 #include <unistd.h>
48
49 static void addgroup(const char *grpname);
50 static void doshell(void);
51 static int inarray(gid_t, const gid_t[], int);
52 static void loginshell(void);
53 static void restoregrps(void);
54 static void usage(void);
55
56 static struct passwd *pwd;
57 static uid_t euid;
58
59 extern char **environ;
60
61 /* Manipulate effective user ID. */
62 #define PRIV_START do { \
63 if (seteuid(euid) < 0) \
64 err(1, "seteuid"); \
65 } while (0)
66 #define PRIV_END do { \
67 if (seteuid(getuid()) < 0) \
68 err(1, "seteuid"); \
69 } while (0)
70
71 int
main(int argc,char * argv[])72 main(int argc, char *argv[])
73 {
74 int ch, login;
75
76 if ((euid = geteuid()) != 0)
77 warnx("need root permissions to function properly, check setuid bit");
78 if (seteuid(getuid()) < 0)
79 err(1, "seteuid");
80
81 if ((pwd = getpwuid(getuid())) == NULL)
82 errx(1, "unknown user");
83
84 login = 0;
85 while ((ch = getopt(argc, argv, "-l")) != -1) {
86 switch (ch) {
87 case '-': /* Obsolescent */
88 case 'l':
89 login = 1;
90 break;
91 default:
92 usage();
93 }
94 }
95 argc -= optind;
96 argv += optind;
97
98 switch (argc) {
99 case 0:
100 restoregrps();
101 break;
102 case 1:
103 addgroup(*argv);
104 break;
105 default:
106 usage();
107 }
108
109 if (seteuid(euid) < 0)
110 err(1, "seteuid");
111 if (setuid(getuid()) < 0)
112 err(1, "setuid");
113
114 if (login)
115 loginshell();
116 else
117 doshell();
118
119 /*NOTREACHED*/
120 exit(1);
121 }
122
123 static void
usage(void)124 usage(void)
125 {
126
127 fprintf(stderr, "usage: newgrp [-l] [group]\n");
128 exit(1);
129 }
130
131 static void
restoregrps(void)132 restoregrps(void)
133 {
134 int initres, setres;
135
136 PRIV_START;
137 initres = initgroups(pwd->pw_name, pwd->pw_gid);
138 setres = setgid(pwd->pw_gid);
139 PRIV_END;
140
141 if (initres < 0)
142 warn("initgroups");
143 if (setres < 0)
144 warn("setgroups");
145 }
146
147 static void
addgroup(const char * grpname)148 addgroup(const char *grpname)
149 {
150 gid_t grps[NGROUPS_MAX];
151 long lgid;
152 int dbmember, i, ngrps;
153 gid_t egid;
154 struct group *grp;
155 char *ep, *pass, *cryptpw;
156 char **p;
157
158 egid = getegid();
159
160 /* Try it as a group name, then a group id. */
161 if ((grp = getgrnam(grpname)) == NULL)
162 if ((lgid = strtol(grpname, &ep, 10)) <= 0 || *ep != '\0' ||
163 (grp = getgrgid((gid_t)lgid)) == NULL ) {
164 warnx("%s: bad group name", grpname);
165 return;
166 }
167
168 /*
169 * If the user is not a member of the requested group and the group
170 * has a password, prompt and check it.
171 */
172 dbmember = 0;
173 if (pwd->pw_gid == grp->gr_gid)
174 dbmember = 1;
175 for (p = grp->gr_mem; *p != NULL; p++)
176 if (strcmp(*p, pwd->pw_name) == 0) {
177 dbmember = 1;
178 break;
179 }
180 if (!dbmember && *grp->gr_passwd != '\0' && getuid() != 0) {
181 pass = getpass("Password:");
182 if (pass == NULL)
183 return;
184 cryptpw = crypt(pass, grp->gr_passwd);
185 if (cryptpw == NULL || strcmp(grp->gr_passwd, cryptpw) != 0) {
186 fprintf(stderr, "Sorry\n");
187 return;
188 }
189 }
190
191 if ((ngrps = getgroups(NGROUPS_MAX, (gid_t *)grps)) < 0) {
192 warn("getgroups");
193 return;
194 }
195
196 /* Remove requested gid from supp. list if it exists. */
197 if (grp->gr_gid != egid && inarray(grp->gr_gid, grps, ngrps)) {
198 for (i = 0; i < ngrps; i++)
199 if (grps[i] == grp->gr_gid)
200 break;
201 ngrps--;
202 memmove(&grps[i], &grps[i + 1], (ngrps - i) * sizeof(gid_t));
203 PRIV_START;
204 if (setgroups(ngrps, (const gid_t *)grps) < 0) {
205 PRIV_END;
206 warn("setgroups");
207 return;
208 }
209 PRIV_END;
210 }
211
212 PRIV_START;
213 if (setgid(grp->gr_gid)) {
214 PRIV_END;
215 warn("setgid");
216 return;
217 }
218 PRIV_END;
219 grps[0] = grp->gr_gid;
220
221 /* Add old effective gid to supp. list if it does not exist. */
222 if (egid != grp->gr_gid && !inarray(egid, grps, ngrps)) {
223 if (ngrps == NGROUPS_MAX)
224 warnx("too many groups");
225 else {
226 grps[ngrps++] = egid;
227 PRIV_START;
228 if (setgroups(ngrps, (const gid_t *)grps)) {
229 PRIV_END;
230 warn("setgroups");
231 return;
232 }
233 PRIV_END;
234 }
235 }
236
237 }
238
239 static int
inarray(gid_t gid,const gid_t grps[],int ngrps)240 inarray(gid_t gid, const gid_t grps[], int ngrps)
241 {
242 int i;
243
244 for (i = 0; i < ngrps; i++)
245 if (grps[i] == gid)
246 return (1);
247 return (0);
248 }
249
250 /*
251 * Set the environment to what would be expected if the user logged in
252 * again; this performs the same steps as su(1)'s -l option.
253 */
254 static void
loginshell(void)255 loginshell(void)
256 {
257 char *args[2], **cleanenv, *term, *ticket;
258 const char *shell;
259 login_cap_t *lc;
260
261 shell = pwd->pw_shell;
262 if (*shell == '\0')
263 shell = _PATH_BSHELL;
264 if (chdir(pwd->pw_dir) < 0) {
265 warn("%s", pwd->pw_dir);
266 chdir("/");
267 }
268
269 term = getenv("TERM");
270 ticket = getenv("KRBTKFILE");
271
272 if ((cleanenv = calloc(20, sizeof(char *))) == NULL)
273 err(1, "calloc");
274 *cleanenv = NULL;
275 environ = cleanenv;
276
277 lc = login_getpwclass(pwd);
278 setusercontext(lc, pwd, pwd->pw_uid,
279 LOGIN_SETPATH|LOGIN_SETUMASK|LOGIN_SETENV);
280 login_close(lc);
281 if (setenv("USER", pwd->pw_name, 1) == -1)
282 err(EXIT_FAILURE, "setenv failed");
283
284 if (setenv("SHELL", shell, 1) == -1)
285 err(EXIT_FAILURE, "setenv failed");
286
287 if (setenv("HOME", pwd->pw_dir, 1) == -1)
288 err(EXIT_FAILURE, "setenv failed");
289
290 if (term != NULL)
291 if (setenv("TERM", term, 1) == -1)
292 err(EXIT_FAILURE, "setenv failed");
293 if (ticket != NULL)
294 if (setenv("KRBTKFILE", ticket, 1) == -1)
295 err(EXIT_FAILURE, "setenv failed");
296
297 if (asprintf(args, "-%s", basename(strdup(shell))) < 0)
298 err(1, "asprintf");
299 args[1] = NULL;
300
301 execv(shell, args);
302 err(1, "%s", shell);
303 }
304
305 static void
doshell(void)306 doshell(void)
307 {
308 const char *shell;
309
310 shell = pwd->pw_shell;
311 if (*shell == '\0')
312 shell = _PATH_BSHELL;
313 execl(shell, basename(strdup(shell)), NULL);
314 err(1, "%s", shell);
315 }
316