newgrp.tproj/newgrp.c

   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: src/usr.bin/newgrp/newgrp.c,v 1.5 2009/12/13 03:14:06 delphij Exp $");
  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 #ifndef __APPLE__
  42 #include <login_cap.h>
  43 #endif /* !__APPLE__ */
  44 #ifdef __APPLE__
  45 #include <membership.h>
  46 #endif /* __APPLE__ */
  47 #include <pwd.h>
  48 #include <stdio.h>
  49 #include <stdlib.h>
  50 #include <string.h>
  51 #include <unistd.h>
  52 #ifdef __APPLE__
  53 #include <paths.h>
  54 #endif /* __APPLE__ */
  55 static void      addgroup(const char *grpname);
  56 static void      doshell(void);
  57 static int       inarray(gid_t, const gid_t[], int);
  58 static void      loginshell(void);
  59 static void      restoregrps(void);
  60 static void      usage(void);
  61
  62 static struct passwd *pwd;
  63 static uid_t euid;
  64
  65 extern char **environ;
  66
  67 /* Manipulate effective user ID. */
  68 #define PRIV_START do {                         \
  69                 if (seteuid(euid) < 0)          \
  70                         err(1, "seteuid");      \
  71         } while (0)
  72 #define PRIV_END do {                           \
  73                 if (seteuid(getuid()) < 0)      \
  74                         err(1, "seteuid");      \
  75         } while (0)
  76
  77 int
  78 main(int argc, char *argv[])
  79 {
  80         int ch, login;
  81
  82         euid = geteuid();
  83         if (seteuid(getuid()) < 0)
  84                 err(1, "seteuid");
  85
  86         if ((pwd = getpwuid(getuid())) == NULL)
  87                 errx(1, "unknown user");
  88
  89         login = 0;
  90         while ((ch = getopt(argc, argv, "-l")) != -1) {
  91                 switch (ch) {
  92                 case '-':               /* Obsolescent */
  93                 case 'l':
  94                         login = 1;
  95                         break;
  96                 default:
  97                         usage();
  98                 }
  99         }
 100         argc -= optind;
 101         argv += optind;
 102
 103         switch (argc) {
 104         case 0:
 105                 restoregrps();
 106                 break;
 107         case 1:
 108                 addgroup(*argv);
 109                 break;
 110         default:
 111                 usage();
 112         }
 113
 114         if (seteuid(euid) < 0)
 115                 err(1, "seteuid");
 116         if (setuid(getuid()) < 0)
 117                 err(1, "setuid");
 118
 119         if (login)
 120                 loginshell();
 121         else
 122                 doshell();
 123
 124         /*NOTREACHED*/
 125         exit(1);
 126 }
 127
 128 static void
 129 usage(void)
 130 {
 131
 132         fprintf(stderr, "usage: newgrp [-l] [group]\n");
 133         exit(1);
 134 }
 135
 136 static void
 137 restoregrps(void)
 138 {
 139         int initres, setres;
 140
 141         PRIV_START;
 142         initres = initgroups(pwd->pw_name, pwd->pw_gid);
 143         setres = setgid(pwd->pw_gid);
 144         PRIV_END;
 145
 146         if (initres < 0)
 147                 warn("initgroups");
 148         if (setres < 0)
 149                 warn("setgid");
 150 }
 151
 152 static void
 153 addgroup(const char *grpname)
 154 {
 155         gid_t *grps;
 156         long lgid, ngrps_max;
 157         int dbmember, i, ngrps;
 158         gid_t egid;
 159         struct group *grp;
 160         char *ep, *pass;
 161 #ifndef __APPLE__
 162         char **p;
 163 #endif
 164         char *grp_passwd;
 165 #ifdef __APPLE__
 166         uuid_t user_uuid;
 167         uuid_t group_uuid;
 168         int status;
 169 #endif
 170
 171         egid = getegid();
 172
 173         /* Try it as a group name, then a group id. */
 174         if ((grp = getgrnam(grpname)) == NULL)
 175                 if ((lgid = strtol(grpname, &ep, 10)) <= 0 || *ep != '\0' ||
 176                     (grp = getgrgid((gid_t)lgid)) == NULL ) {
 177                         warnx("%s: bad group name", grpname);
 178                         return;
 179                 }
 180
 181 #ifdef __APPLE__
 182         status = mbr_uid_to_uuid(pwd->pw_uid, user_uuid);
 183         if (status)
 184                 errc(1, status, "mbr_uid_to_uuid");
 185
 186         status = mbr_gid_to_uuid(grp->gr_gid, group_uuid);
 187         if (status)
 188                 errc(1, status, "mbr_gid_to_uuid");
 189
 190         status = mbr_check_membership(user_uuid, group_uuid, &dbmember);
 191         if (status)
 192                 errc(1, status, "mbr_check_membership");
 193 #else
 194         /*
 195          * If the user is not a member of the requested group and the group
 196          * has a password, prompt and check it.
 197          */
 198         dbmember = 0;
 199         if (pwd->pw_gid == grp->gr_gid)
 200                 dbmember = 1;
 201         for (p = grp->gr_mem; *p != NULL; p++)
 202                 if (strcmp(*p, pwd->pw_name) == 0) {
 203                         dbmember = 1;
 204                         break;
 205                 }
 206 #endif
 207
 208         grp_passwd = grp->gr_passwd;
 209         if ((grp_passwd == NULL) || (grp_passwd[0] == '\0'))
 210                 grp_passwd = "*";
 211         if (!dbmember && getuid() != 0) {
 212                 pass = getpass("Password:");
 213                 if (pass == NULL ||
 214                     strcmp(grp_passwd, crypt(pass, grp_passwd)) != 0) {
 215                         fprintf(stderr, "Sorry\n");
 216                         return;
 217                 }
 218         }
 219
 220         ngrps_max = sysconf(_SC_NGROUPS_MAX) + 1;
 221         if ((grps = malloc(sizeof(gid_t) * ngrps_max)) == NULL)
 222                 err(1, "malloc");
 223         if ((ngrps = getgroups((int)ngrps_max, (gid_t *)grps)) < 0) {
 224                 warn("getgroups");
 225                 goto end;
 226         }
 227
 228         /* Remove requested gid from supp. list if it exists. */
 229         if (grp->gr_gid != egid && inarray(grp->gr_gid, grps, ngrps)) {
 230                 for (i = 0; i < ngrps; i++)
 231                         if (grps[i] == grp->gr_gid)
 232                                 break;
 233                 ngrps--;
 234                 memmove(&grps[i], &grps[i + 1], (ngrps - i) * sizeof(gid_t));
 235                 PRIV_START;
 236                 if (setgroups(ngrps, (const gid_t *)grps) < 0) {
 237                         PRIV_END;
 238                         warn("setgroups");
 239                         goto end;
 240                 }
 241                 PRIV_END;
 242         }
 243
 244         PRIV_START;
 245         if (setgid(grp->gr_gid)) {
 246                 PRIV_END;
 247                 warn("setgid");
 248                 goto end;
 249         }
 250         PRIV_END;
 251         grps[0] = grp->gr_gid;
 252
 253         /* Add old effective gid to supp. list if it does not exist. */
 254         if (egid != grp->gr_gid && !inarray(egid, grps, ngrps)) {
 255                 if (ngrps + 1 >= ngrps_max)
 256                         warnx("too many groups");
 257                 else {
 258                         grps[ngrps++] = egid;
 259                         PRIV_START;
 260                         if (setgroups(ngrps, (const gid_t *)grps)) {
 261                                 PRIV_END;
 262                                 warn("setgroups");
 263                                 goto end;
 264                         }
 265                         PRIV_END;
 266                 }
 267         }
 268
 269 end:
 270         free(grps);
 271 }
 272
 273 static int
 274 inarray(gid_t gid, const gid_t grps[], int ngrps)
 275 {
 276         int i;
 277
 278         for (i = 0; i < ngrps; i++)
 279                 if (grps[i] == gid)
 280                         return (1);
 281         return (0);
 282 }
 283
 284 /*
 285  * Set the environment to what would be expected if the user logged in
 286  * again; this performs the same steps as su(1)'s -l option.
 287  */
 288 static void
 289 loginshell(void)
 290 {
 291         char *args[2], **cleanenv, *term, *ticket;
 292         const char *shell;
 293         char *prog, progbuf[PATH_MAX];
 294 #ifndef __APPLE__
 295         login_cap_t *lc;
 296 #endif /* !__APPLE__ */
 297         shell = pwd->pw_shell;
 298         if (*shell == '\0')
 299                 shell = _PATH_BSHELL;
 300         if (chdir(pwd->pw_dir) < 0) {
 301                 warn("%s", pwd->pw_dir);
 302                 chdir("/");
 303         }
 304
 305         term = getenv("TERM");
 306         ticket = getenv("KRBTKFILE");
 307
 308         if ((cleanenv = calloc(20, sizeof(char *))) == NULL)
 309                 err(1, "calloc");
 310         *cleanenv = NULL;
 311         environ = cleanenv;
 312 #ifndef __APPLE__
 313         lc = login_getpwclass(pwd);
 314         setusercontext(lc, pwd, pwd->pw_uid,
 315             LOGIN_SETPATH|LOGIN_SETUMASK|LOGIN_SETENV);
 316         login_close(lc);
 317 #endif /* !__APPLE__ */
 318         setenv("USER", pwd->pw_name, 1);
 319         setenv("SHELL", shell, 1);
 320         setenv("HOME", pwd->pw_dir, 1);
 321         if (term != NULL)
 322                 setenv("TERM", term, 1);
 323         if (ticket != NULL)
 324                 setenv("KRBTKFILE", ticket, 1);
 325
 326         strlcpy(progbuf, shell, sizeof(progbuf));
 327         prog = basename(progbuf);
 328
 329         if (asprintf(args, "-%s", prog) < 0)
 330                 err(1, "asprintf");
 331         args[1] = NULL;
 332
 333         execv(shell, args);
 334         err(1, "%s", shell);
 335 }
 336
 337 static void
 338 doshell(void)
 339 {
 340         const char *shell;
 341         char *prog, progbuf[PATH_MAX];
 342
 343         shell = pwd->pw_shell;
 344         if (*shell == '\0')
 345                 shell = _PATH_BSHELL;
 346
 347         strlcpy(progbuf, shell, sizeof(progbuf));
 348         prog = basename(progbuf);
 349
 350         execl(shell, prog, (char *)NULL);
 351         err(1, "%s", shell);
 352 }