newgrp.c revision 97364
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 27/* 28 * newgrp -- change to a new group 29 */ 30 31#include <sys/cdefs.h> 32__FBSDID("$FreeBSD: head/usr.bin/newgrp/newgrp.c 97364 2002-05-28 05:05:28Z tjr $"); 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 49static void addgroup(const char *grpname); 50static void doshell(void); 51static int inarray(gid_t, const gid_t[], int); 52static void loginshell(void); 53static void restoregrps(void); 54static void usage(void); 55 56static struct passwd *pwd; 57static uid_t euid; 58 59extern 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 71int 72main(int argc, char *argv[]) 73{ 74 int ch, login; 75 76 euid = geteuid(); 77 if (seteuid(getuid()) < 0) 78 err(1, "seteuid"); 79 80 if ((pwd = getpwuid(getuid())) == NULL) 81 errx(1, "unknown user"); 82 83 login = 0; 84 while ((ch = getopt(argc, argv, "-l")) != -1) { 85 switch (ch) { 86 case '-': /* Obsolescent */ 87 case 'l': 88 login = 1; 89 break; 90 default: 91 usage(); 92 } 93 } 94 argc -= optind; 95 argv += optind; 96 97 switch (argc) { 98 case 0: 99 restoregrps(); 100 break; 101 case 1: 102 addgroup(*argv); 103 break; 104 default: 105 usage(); 106 } 107 108 if (seteuid(euid) < 0) 109 err(1, "seteuid"); 110 if (setuid(getuid()) < 0) 111 err(1, "setuid"); 112 113 if (login) 114 loginshell(); 115 else 116 doshell(); 117 118 /*NOTREACHED*/ 119 exit(1); 120} 121 122static void 123usage(void) 124{ 125 126 fprintf(stderr, "usage: newgrp [-l] [group]\n"); 127 exit(1); 128} 129 130static void 131restoregrps(void) 132{ 133 int initres, setres; 134 135 PRIV_START; 136 initres = initgroups(pwd->pw_name, pwd->pw_gid); 137 setres = setgid(pwd->pw_gid); 138 PRIV_END; 139 140 if (initres < 0) 141 warn("initgroups"); 142 if (setres < 0) 143 warn("setgroups"); 144} 145 146static void 147addgroup(const char *grpname) 148{ 149 gid_t grps[NGROUPS_MAX]; 150 long lgid; 151 int dbmember, i, ngrps; 152 gid_t egid; 153 struct group *grp; 154 char *ep, *pass; 155 char **p; 156 157 egid = getegid(); 158 159 /* Try it as a group name, then a group id. */ 160 if ((grp = getgrnam(grpname)) == NULL) 161 if ((lgid = strtol(grpname, &ep, 10)) <= 0 || *ep != '\0' || 162 (grp = getgrgid((gid_t)lgid)) == NULL ) { 163 warnx("%s: bad group name", grpname); 164 return; 165 } 166 167 /* 168 * If the user is not a member of the requested group and the group 169 * has a password, prompt and check it. 170 */ 171 dbmember = 0; 172 if (pwd->pw_gid == grp->gr_gid) 173 dbmember = 1; 174 for (p = grp->gr_mem; *p != NULL; p++) 175 if (strcmp(*p, pwd->pw_name) == 0) { 176 dbmember = 1; 177 break; 178 } 179 if (!dbmember && *grp->gr_passwd != '\0' && getuid() != 0) { 180 pass = getpass("Password:"); 181 if (pass == NULL || 182 strcmp(grp->gr_passwd, crypt(pass, grp->gr_passwd)) != 0) { 183 fprintf(stderr, "Sorry\n"); 184 return; 185 } 186 } 187 188 if ((ngrps = getgroups(NGROUPS_MAX, (gid_t *)grps)) < 0) { 189 warn("getgroups"); 190 return; 191 } 192 193 /* Remove requested gid from supp. list if it exists. */ 194 if (grp->gr_gid != egid && inarray(grp->gr_gid, grps, ngrps)) { 195 for (i = 0; i < ngrps; i++) 196 if (grps[i] == grp->gr_gid) 197 break; 198 ngrps--; 199 memmove(&grps[i], &grps[i + 1], (ngrps - i) * sizeof(gid_t)); 200 PRIV_START; 201 if (setgroups(ngrps, (const gid_t *)grps) < 0) { 202 PRIV_END; 203 warn("setgroups"); 204 return; 205 } 206 PRIV_END; 207 } 208 209 PRIV_START; 210 if (setgid(grp->gr_gid)) { 211 PRIV_END; 212 warn("setgid"); 213 return; 214 } 215 PRIV_END; 216 grps[0] = grp->gr_gid; 217 218 /* Add old effective gid to supp. list if it does not exist. */ 219 if (egid != grp->gr_gid && !inarray(egid, grps, ngrps)) { 220 if (ngrps == NGROUPS_MAX) 221 warnx("too many groups"); 222 else { 223 grps[ngrps++] = egid; 224 PRIV_START; 225 if (setgroups(ngrps, (const gid_t *)grps)) { 226 PRIV_END; 227 warn("setgroups"); 228 return; 229 } 230 PRIV_END; 231 } 232 } 233 234} 235 236static int 237inarray(gid_t gid, const gid_t grps[], int ngrps) 238{ 239 int i; 240 241 for (i = 0; i < ngrps; i++) 242 if (grps[i] == gid) 243 return (1); 244 return (0); 245} 246 247/* 248 * Set the environment to what would be expected if the user logged in 249 * again; this performs the same steps as su(1)'s -l option. 250 */ 251static void 252loginshell(void) 253{ 254 char *args[2], **cleanenv, *term, *ticket; 255 const char *shell; 256 login_cap_t *lc; 257 258 shell = pwd->pw_shell; 259 if (*shell == '\0') 260 shell = _PATH_BSHELL; 261 if (chdir(pwd->pw_dir) < 0) { 262 warn("%s", pwd->pw_dir); 263 chdir("/"); 264 } 265 266 term = getenv("TERM"); 267 ticket = getenv("KRBTKFILE"); 268 269 if ((cleanenv = calloc(20, sizeof(char *))) == NULL) 270 err(1, "calloc"); 271 *cleanenv = NULL; 272 environ = cleanenv; 273 274 lc = login_getpwclass(pwd); 275 setusercontext(lc, pwd, pwd->pw_uid, 276 LOGIN_SETPATH|LOGIN_SETUMASK|LOGIN_SETENV); 277 login_close(lc); 278 setenv("USER", pwd->pw_name, 1); 279 setenv("SHELL", shell, 1); 280 setenv("HOME", pwd->pw_dir, 1); 281 if (term != NULL) 282 setenv("TERM", term, 1); 283 if (ticket != NULL) 284 setenv("KRBTKFILE", ticket, 1); 285 286 if (asprintf(args, "-%s", basename(shell)) < 0) 287 err(1, "asprintf"); 288 args[1] = NULL; 289 290 execv(shell, args); 291 err(1, "%s", shell); 292} 293 294static void 295doshell(void) 296{ 297 const char *shell; 298 299 shell = pwd->pw_shell; 300 if (*shell == '\0') 301 shell = _PATH_BSHELL; 302 execl(shell, basename(shell), NULL); 303 err(1, "%s", shell); 304} 305