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         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
 122 static void
 123 usage(void)
 124 {
 125
 126         fprintf(stderr, "usage: newgrp [-l] [group]\n");
 127         exit(1);
 128 }
 129
 130 static void
 131 restoregrps(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
 146 static void
 147 addgroup(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
 236 static int
 237 inarray(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  */
 251 static void
 252 loginshell(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         if (setenv("USER", pwd->pw_name, 1) == -1)
 279                 err(EXIT_FAILURE, "setenv failed");
 280
 281         if (setenv("SHELL", shell, 1) == -1)
 282                 err(EXIT_FAILURE, "setenv failed");
 283
 284         if (setenv("HOME", pwd->pw_dir, 1) == -1)
 285                 err(EXIT_FAILURE, "setenv failed");
 286
 287         if (term != NULL)
 288                 if (setenv("TERM", term, 1) == -1)
 289                         err(EXIT_FAILURE, "setenv failed");
 290         if (ticket != NULL)
 291                 if (setenv("KRBTKFILE", ticket, 1) == -1)
 292                         err(EXIT_FAILURE, "setenv failed");
 293
 294         if (asprintf(args, "-%s", basename(shell)) < 0)
 295                 err(1, "asprintf");
 296         args[1] = NULL;
 297
 298         execv(shell, args);
 299         err(1, "%s", shell);
 300 }
 301
 302 static void
 303 doshell(void)
 304 {
 305         const char *shell;
 306
 307         shell = pwd->pw_shell;
 308         if (*shell == '\0')
 309                 shell = _PATH_BSHELL;
 310         execl(shell, basename(shell), NULL);
 311         err(1, "%s", shell);
 312 }