usr.bin/newgrp/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  * $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 }