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 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 124 usage(void) 125 { 126 127 fprintf(stderr, "usage: newgrp [-l] [group]\n"); 128 exit(1); 129 } 130 131 static 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 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 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 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(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 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(shell), NULL); 314 err(1, "%s", shell); 315 } 316