system_cmds/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
  56 #include <libiosexec.h>
  57
  58 static void      addgroup(const char *grpname);
  59 static void      doshell(void);
  60 static int       inarray(gid_t, const gid_t[], int);
  61 static void      loginshell(void);
  62 static void      restoregrps(void);
  63 static void      usage(void);
  64
  65 static struct passwd *pwd;
  66 static uid_t euid;
  67
  68 extern char **environ;
  69
  70 /* Manipulate effective user ID. */
  71 #define PRIV_START do {                         \
  72                 if (seteuid(euid) < 0)          \
  73                         err(1, "seteuid");      \
  74         } while (0)
  75 #define PRIV_END do {                           \
  76                 if (seteuid(getuid()) < 0)      \
  77                         err(1, "seteuid");      \
  78         } while (0)
  79
  80 int
  81 main(int argc, char *argv[])
  82 {
  83         int ch, login;
  84
  85         euid = geteuid();
  86         if (seteuid(getuid()) < 0)
  87                 err(1, "seteuid");
  88
  89         if ((pwd = getpwuid(getuid())) == NULL)
  90                 errx(1, "unknown user");
  91
  92         login = 0;
  93         while ((ch = getopt(argc, argv, "-l")) != -1) {
  94                 switch (ch) {
  95                 case '-':               /* Obsolescent */
  96                 case 'l':
  97                         login = 1;
  98                         break;
  99                 default:
 100                         usage();
 101                 }
 102         }
 103         argc -= optind;
 104         argv += optind;
 105
 106         switch (argc) {
 107         case 0:
 108                 restoregrps();
 109                 break;
 110         case 1:
 111                 addgroup(*argv);
 112                 break;
 113         default:
 114                 usage();
 115         }
 116
 117         if (seteuid(euid) < 0)
 118                 err(1, "seteuid");
 119         if (setuid(getuid()) < 0)
 120                 err(1, "setuid");
 121
 122         if (login)
 123                 loginshell();
 124         else
 125                 doshell();
 126
 127         /*NOTREACHED*/
 128         exit(1);
 129 }
 130
 131 static void
 132 usage(void)
 133 {
 134
 135         fprintf(stderr, "usage: newgrp [-l] [group]\n");
 136         exit(1);
 137 }
 138
 139 static void
 140 restoregrps(void)
 141 {
 142         int initres, setres;
 143
 144         PRIV_START;
 145         initres = initgroups(pwd->pw_name, pwd->pw_gid);
 146         setres = setgid(pwd->pw_gid);
 147         PRIV_END;
 148
 149         if (initres < 0)
 150                 warn("initgroups");
 151         if (setres < 0)
 152                 warn("setgid");
 153 }
 154
 155 static void
 156 addgroup(const char *grpname)
 157 {
 158         gid_t *grps;
 159         long lgid, ngrps_max;
 160         int dbmember, i, ngrps;
 161         gid_t egid;
 162         struct group *grp;
 163         char *ep, *pass;
 164 #ifndef __APPLE__
 165         char **p;
 166 #endif
 167         char *grp_passwd;
 168 #ifdef __APPLE__
 169         uuid_t user_uuid;
 170         uuid_t group_uuid;
 171         int status;
 172 #endif
 173
 174         egid = getegid();
 175
 176         /* Try it as a group name, then a group id. */
 177         if ((grp = getgrnam(grpname)) == NULL)
 178                 if ((lgid = strtol(grpname, &ep, 10)) <= 0 || *ep != '\0' ||
 179                     (grp = getgrgid((gid_t)lgid)) == NULL ) {
 180                         warnx("%s: bad group name", grpname);
 181                         return;
 182                 }
 183
 184 #ifdef __APPLE__
 185         status = mbr_uid_to_uuid(pwd->pw_uid, user_uuid);
 186         if (status)
 187                 errc(1, status, "mbr_uid_to_uuid");
 188
 189         status = mbr_gid_to_uuid(grp->gr_gid, group_uuid);
 190         if (status)
 191                 errc(1, status, "mbr_gid_to_uuid");
 192
 193         status = mbr_check_membership(user_uuid, group_uuid, &dbmember);
 194         if (status)
 195                 errc(1, status, "mbr_check_membership");
 196 #else
 197         /*
 198          * If the user is not a member of the requested group and the group
 199          * has a password, prompt and check it.
 200          */
 201         dbmember = 0;
 202         if (pwd->pw_gid == grp->gr_gid)
 203                 dbmember = 1;
 204         for (p = grp->gr_mem; *p != NULL; p++)
 205                 if (strcmp(*p, pwd->pw_name) == 0) {
 206                         dbmember = 1;
 207                         break;
 208                 }
 209 #endif
 210
 211         grp_passwd = grp->gr_passwd;
 212         if ((grp_passwd == NULL) || (grp_passwd[0] == '\0'))
 213                 grp_passwd = "*";
 214         if (!dbmember && getuid() != 0) {
 215                 pass = getpass("Password:");
 216                 if (pass == NULL ||
 217                     strcmp(grp_passwd, crypt(pass, grp_passwd)) != 0) {
 218                         fprintf(stderr, "Sorry\n");
 219                         return;
 220                 }
 221         }
 222
 223         ngrps_max = sysconf(_SC_NGROUPS_MAX) + 1;
 224         if ((grps = malloc(sizeof(gid_t) * ngrps_max)) == NULL)
 225                 err(1, "malloc");
 226         if ((ngrps = getgroups((int)ngrps_max, (gid_t *)grps)) < 0) {
 227                 warn("getgroups");
 228                 goto end;
 229         }
 230
 231         /* Remove requested gid from supp. list if it exists. */
 232         if (grp->gr_gid != egid && inarray(grp->gr_gid, grps, ngrps)) {
 233                 for (i = 0; i < ngrps; i++)
 234                         if (grps[i] == grp->gr_gid)
 235                                 break;
 236                 ngrps--;
 237                 memmove(&grps[i], &grps[i + 1], (ngrps - i) * sizeof(gid_t));
 238                 PRIV_START;
 239                 if (setgroups(ngrps, (const gid_t *)grps) < 0) {
 240                         PRIV_END;
 241                         warn("setgroups");
 242                         goto end;
 243                 }
 244                 PRIV_END;
 245         }
 246
 247         PRIV_START;
 248         if (setgid(grp->gr_gid)) {
 249                 PRIV_END;
 250                 warn("setgid");
 251                 goto end;
 252         }
 253         PRIV_END;
 254         grps[0] = grp->gr_gid;
 255
 256         /* Add old effective gid to supp. list if it does not exist. */
 257         if (egid != grp->gr_gid && !inarray(egid, grps, ngrps)) {
 258                 if (ngrps + 1 >= ngrps_max)
 259                         warnx("too many groups");
 260                 else {
 261                         grps[ngrps++] = egid;
 262                         PRIV_START;
 263                         if (setgroups(ngrps, (const gid_t *)grps)) {
 264                                 PRIV_END;
 265                                 warn("setgroups");
 266                                 goto end;
 267                         }
 268                         PRIV_END;
 269                 }
 270         }
 271
 272 end:
 273         free(grps);
 274 }
 275
 276 static int
 277 inarray(gid_t gid, const gid_t grps[], int ngrps)
 278 {
 279         int i;
 280
 281         for (i = 0; i < ngrps; i++)
 282                 if (grps[i] == gid)
 283                         return (1);
 284         return (0);
 285 }
 286
 287 /*
 288  * Set the environment to what would be expected if the user logged in
 289  * again; this performs the same steps as su(1)'s -l option.
 290  */
 291 static void
 292 loginshell(void)
 293 {
 294         char *args[2], **cleanenv, *term, *ticket;
 295         const char *shell;
 296         char *prog, progbuf[PATH_MAX];
 297 #ifndef __APPLE__
 298         login_cap_t *lc;
 299 #endif /* !__APPLE__ */
 300         shell = pwd->pw_shell;
 301         if (*shell == '\0')
 302                 shell = _PATH_BSHELL;
 303         if (chdir(pwd->pw_dir) < 0) {
 304                 warn("%s", pwd->pw_dir);
 305                 chdir("/");
 306         }
 307
 308         term = getenv("TERM");
 309         ticket = getenv("KRBTKFILE");
 310
 311         if ((cleanenv = calloc(20, sizeof(char *))) == NULL)
 312                 err(1, "calloc");
 313         *cleanenv = NULL;
 314         environ = cleanenv;
 315 #ifndef __APPLE__
 316         lc = login_getpwclass(pwd);
 317         setusercontext(lc, pwd, pwd->pw_uid,
 318             LOGIN_SETPATH|LOGIN_SETUMASK|LOGIN_SETENV);
 319         login_close(lc);
 320 #endif /* !__APPLE__ */
 321         setenv("USER", pwd->pw_name, 1);
 322         setenv("SHELL", shell, 1);
 323         setenv("HOME", pwd->pw_dir, 1);
 324         if (term != NULL)
 325                 setenv("TERM", term, 1);
 326         if (ticket != NULL)
 327                 setenv("KRBTKFILE", ticket, 1);
 328
 329         strlcpy(progbuf, shell, sizeof(progbuf));
 330         prog = basename(progbuf);
 331
 332         if (asprintf(args, "-%s", prog) < 0)
 333                 err(1, "asprintf");
 334         args[1] = NULL;
 335
 336         execv(shell, args);
 337         err(1, "%s", shell);
 338 }
 339
 340 static void
 341 doshell(void)
 342 {
 343         const char *shell;
 344         char *prog, progbuf[PATH_MAX];
 345
 346         shell = pwd->pw_shell;
 347         if (*shell == '\0')
 348                 shell = _PATH_BSHELL;
 349
 350         strlcpy(progbuf, shell, sizeof(progbuf));
 351         prog = basename(progbuf);
 352
 353         execl(shell, prog, (char *)NULL);
 354         err(1, "%s", shell);
 355 }