usr.bin/newgrp/grutil.c

   1 /*      $NetBSD: grutil.c,v 1.1 2007/10/27 15:36:21 christos Exp $      */
   2
   3 /*-
   4  * Copyright (c) 2007 The NetBSD Foundation, Inc.
   5  * All rights reserved.
   6  *
   7  * This code is derived from software contributed to The NetBSD Foundation
   8  * by Brian Ginsbach.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
  20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
  21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
  23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  29  * POSSIBILITY OF SUCH DAMAGE.
  30  */
  31 #include <sys/cdefs.h>
  32 __RCSID("$NetBSD: grutil.c,v 1.1 2007/10/27 15:36:21 christos Exp $");
  33
  34 #include <sys/param.h>
  35 #include <err.h>
  36 #include <errno.h>
  37 #include <grp.h>
  38 #include <pwd.h>
  39 #include <stdio.h>
  40 #include <stdlib.h>
  41 #include <string.h>
  42 #include <unistd.h>
  43 #include <util.h>
  44
  45 #ifdef LOGIN_CAP
  46 #include <login_cap.h>
  47 #endif
  48
  49 #include "grutil.h"
  50
  51 typedef enum {
  52         ADDGRP_NOERROR          = 0,    /* must be zero */
  53         ADDGRP_EMALLOC          = 1,
  54         ADDGRP_EGETGROUPS       = 2,
  55         ADDGRP_ESETGROUPS       = 3
  56 } addgrp_ret_t;
  57
  58 static void
  59 free_groups(void *groups)
  60 {
  61         int oerrno;
  62
  63         oerrno = errno;
  64         free(groups);
  65         errno = oerrno;
  66 }
  67
  68 static addgrp_ret_t
  69 alloc_groups(int *ngroups, gid_t **groups, int *ngroupsmax)
  70 {
  71         *ngroupsmax = (int)sysconf(_SC_NGROUPS_MAX);
  72         if (*ngroupsmax < 0)
  73                 *ngroupsmax = NGROUPS_MAX;
  74
  75         *groups = malloc(*ngroupsmax * sizeof(**groups));
  76         if (*groups == NULL)
  77                 return ADDGRP_EMALLOC;
  78
  79         *ngroups = getgroups(*ngroupsmax, *groups);
  80         if (*ngroups == -1) {
  81                 free_groups(*groups);
  82                 return ADDGRP_ESETGROUPS;
  83         }
  84         return ADDGRP_NOERROR;
  85 }
  86
  87 static addgrp_ret_t
  88 addgid(gid_t *groups, int ngroups, int ngroupsmax, gid_t gid, int makespace)
  89 {
  90         int i;
  91
  92         /* search for gid in supplemental group list */
  93         for (i = 0; i < ngroups && groups[i] != gid; i++)
  94                 continue;
  95
  96         /* add the gid to the supplemental group list */
  97         if (i == ngroups) {
  98                 if (ngroups < ngroupsmax)
  99                         groups[ngroups++] = gid;
 100                 else {  /*
 101                          * setgroups(2) will fail with errno = EINVAL
 102                          * if ngroups > nmaxgroups.  If makespace is
 103                          * set, replace the last group with the new
 104                          * one.  Otherwise, fail the way setgroups(2)
 105                          * would if we passed the larger groups array.
 106                          */
 107                         if (makespace) {
 108                                 /*
 109                                  * Find a slot that doesn't contain
 110                                  * the primary group.
 111                                  */
 112                                 struct passwd *pwd;
 113                                 gid_t pgid;
 114                                 pwd = getpwuid(getuid());
 115                                 if (pwd == NULL)
 116                                         goto error;
 117                                 pgid = pwd->pw_gid;
 118                                 for (i = ngroupsmax - 1; i >= 0; i--)
 119                                         if (groups[i] != pgid)
 120                                                 break;
 121                                 if (i < 0)
 122                                         goto error;
 123                                 groups[i] = gid;
 124                         }
 125                         else {
 126                 error:
 127                                 errno = EINVAL;
 128                                 return ADDGRP_ESETGROUPS;
 129                         }
 130                 }
 131                 if (setgroups(ngroups, groups) < 0)
 132                         return ADDGRP_ESETGROUPS;
 133         }
 134         return ADDGRP_NOERROR;
 135 }
 136
 137 static addgrp_ret_t
 138 addgrp(gid_t newgid, int makespace)
 139 {
 140         int ngroups, ngroupsmax, rval;
 141         gid_t *groups;
 142         gid_t oldgid;
 143
 144         oldgid = getgid();
 145         if (oldgid == newgid) /* nothing to do */
 146                 return ADDGRP_NOERROR;
 147
 148         rval = alloc_groups(&ngroups, &groups, &ngroupsmax);
 149         if (rval != 0)
 150                 return rval;
 151
 152         /*
 153          * BSD based systems normally have the egid in the supplemental
 154          * group list.
 155          */
 156 #if (defined(BSD) && BSD >= 199306)
 157         /*
 158          * According to POSIX/XPG6:
 159          * On system where the egid is normally in the supplemental group list
 160          * (or whenever the old egid actually is in the supplemental group
 161          * list):
 162          *      o If the new egid is in the supplemental group list,
 163          *        just change the egid.
 164          *      o If the new egid is not in the supplemental group list,
 165          *        add the new egid to the list if there is room.
 166          */
 167
 168         rval = addgid(groups, ngroups, ngroupsmax, newgid, makespace);
 169 #else
 170         /*
 171          * According to POSIX/XPG6:
 172          * On systems where the egid is not normally in the supplemental group
 173          * list (or whenever the old egid is not in the supplemental group
 174          * list):
 175          *      o If the new egid is in the supplemental group list, delete
 176          *        it from the list.
 177          *      o If the old egid is not in the supplemental group list,
 178          *        add the old egid to the list if there is room.
 179          */
 180         {
 181                 int i;
 182
 183                 /* search for new egid in supplemental group list */
 184                 for (i = 0; i < ngroups && groups[i] != newgid; i++)
 185                         continue;
 186
 187                 /* remove new egid from supplemental group list */
 188                 if (i != ngroups)
 189                         for (--ngroups; i < ngroups; i++)
 190                                 groups[i] = groups[i + 1];
 191
 192                 rval = addgid(groups, ngroups, ngroupsmax, oldgid, makespace);
 193         }
 194 #endif
 195         free_groups(groups);
 196         return rval;
 197 }
 198
 199 /*
 200  * If newgrp fails, it returns (gid_t)-1 and the errno variable is
 201  * set to:
 202  *      [EINVAL]        Unknown group.
 203  *      [EPERM]         Bad password.
 204  */
 205 static gid_t
 206 newgrp(const char *gname, struct passwd *pwd, uid_t ruid, const char *prompt)
 207 {
 208         struct group *grp;
 209         char **ap;
 210         char *p;
 211         gid_t *groups;
 212         int ngroups, ngroupsmax;
 213
 214         if (gname == NULL)
 215                 return pwd->pw_gid;
 216
 217         grp = getgrnam(gname);
 218
 219 #ifdef GRUTIL_ACCEPT_GROUP_NUMBERS
 220         if (grp == NULL) {
 221                 gid_t gid;
 222                 if (*gname != '-') {
 223                     gid = (gid_t)strtol(gname, &p, 10);
 224                     if (*p == '\0')
 225                             grp = getgrgid(gid);
 226                 }
 227         }
 228 #endif
 229         if (grp == NULL) {
 230                 errno = EINVAL;
 231                 return (gid_t)-1;
 232         }
 233
 234         if (ruid == 0 || pwd->pw_gid == grp->gr_gid)
 235                 return grp->gr_gid;
 236
 237         if (alloc_groups(&ngroups, &groups, &ngroupsmax) == 0) {
 238                 int i;
 239                 for (i = 0; i < ngroups; i++)
 240                         if (groups[i] == grp->gr_gid) {
 241                                 free_groups(groups);
 242                                 return grp->gr_gid;
 243                         }
 244                 free_groups(groups);
 245         }
 246
 247         /*
 248          * Check the group membership list in case the groups[] array
 249          * was maxed out or the user has been added to it since login.
 250          */
 251         for (ap = grp->gr_mem; *ap != NULL; ap++)
 252                 if (strcmp(*ap, pwd->pw_name) == 0)
 253                         return grp->gr_gid;
 254
 255         if (*grp->gr_passwd != '\0') {
 256                 p = getpass(prompt);
 257                 if (strcmp(grp->gr_passwd, crypt(p, grp->gr_passwd)) == 0) {
 258                         (void)memset(p, '\0', _PASSWORD_LEN);
 259                         return grp->gr_gid;
 260                 }
 261                 (void)memset(p, '\0', _PASSWORD_LEN);
 262         }
 263
 264         errno = EPERM;
 265         return (gid_t)-1;
 266 }
 267
 268 #ifdef GRUTIL_SETGROUPS_MAKESPACE
 269 # define ADDGRP_MAKESPACE       1
 270 #else
 271 # define ADDGRP_MAKESPACE       0
 272 #endif
 273
 274 #ifdef GRUTIL_ALLOW_GROUP_ERRORS
 275 # define maybe_exit(e)
 276 #else
 277 # define maybe_exit(e)  exit(e);
 278 #endif
 279
 280 void
 281 addgroup(
 282 #ifdef LOGIN_CAP
 283     login_cap_t *lc,
 284 #endif
 285     const char *gname, struct passwd *pwd, uid_t ruid, const char *prompt)
 286 {
 287         pwd->pw_gid = newgrp(gname, pwd, ruid, prompt);
 288         if (pwd->pw_gid == (gid_t)-1) {
 289                 switch (errno) {
 290                 case EINVAL:
 291                         warnx("Unknown group `%s'", gname);
 292                         maybe_exit(EXIT_FAILURE);
 293                         break;
 294                 case EPERM:     /* password failure */
 295                         warnx("Sorry");
 296                         maybe_exit(EXIT_FAILURE);
 297                         break;
 298                 default: /* XXX - should never happen */
 299                         err(EXIT_FAILURE, "unknown error");
 300                         break;
 301                 }
 302                 pwd->pw_gid = getgid();
 303         }
 304
 305         switch (addgrp(pwd->pw_gid, ADDGRP_MAKESPACE)) {
 306         case ADDGRP_NOERROR:
 307                 break;
 308         case ADDGRP_EMALLOC:
 309                 err(EXIT_FAILURE, "malloc");
 310                 break;
 311         case ADDGRP_EGETGROUPS:
 312                 err(EXIT_FAILURE, "getgroups");
 313                 break;
 314         case ADDGRP_ESETGROUPS:
 315                 switch(errno) {
 316                 case EINVAL:
 317                         warnx("setgroups: ngroups > ngroupsmax");
 318                         maybe_exit(EXIT_FAILURE);
 319                         break;
 320                 case EPERM:
 321                 case EFAULT:
 322                 default:
 323                         warn("setgroups");
 324                         maybe_exit(EXIT_FAILURE);
 325                         break;
 326                 }
 327                 break;
 328         }
 329
 330 #ifdef LOGIN_CAP
 331         if (setusercontext(lc, pwd, pwd->pw_uid, LOGIN_SETGID) == -1)
 332                 err(EXIT_FAILURE, "setting user context");
 333 #else
 334         if (setgid(pwd->pw_gid) == -1)
 335                 err(EXIT_FAILURE, "setgid");
 336 #endif
 337 }