nis/nss_compat/compat-initgroups.c

   1 /* Copyright (C) 1998-2015 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Thorsten Kukuk <kukuk@suse.de>, 1998.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <alloca.h>
  20 #include <ctype.h>
  21 #include <errno.h>
  22 #include <fcntl.h>
  23 #include <grp.h>
  24 #include <nss.h>
  25 #include <stdio_ext.h>
  26 #include <string.h>
  27 #include <unistd.h>
  28 #include <rpc/types.h>
  29 #include <sys/param.h>
  30 #include <nsswitch.h>
  31 #include <bits/libc-lock.h>
  32 #include <kernel-features.h>
  33
  34 static service_user *ni;
  35 /* Type of the lookup function.  */
  36 static enum nss_status (*nss_initgroups_dyn) (const char *, gid_t,
  37                                               long int *, long int *,
  38                                               gid_t **, long int, int *);
  39 static enum nss_status (*nss_getgrnam_r) (const char *name,
  40                                           struct group * grp, char *buffer,
  41                                           size_t buflen, int *errnop);
  42 static enum nss_status (*nss_getgrgid_r) (gid_t gid, struct group * grp,
  43                                           char *buffer, size_t buflen,
  44                                           int *errnop);
  45 static enum nss_status (*nss_setgrent) (int stayopen);
  46 static enum nss_status (*nss_getgrent_r) (struct group * grp, char *buffer,
  47                                           size_t buflen, int *errnop);
  48 static enum nss_status (*nss_endgrent) (void);
  49
  50 /* Protect global state against multiple changers.  */
  51 __libc_lock_define_initialized (static, lock)
  52
  53
  54 /* Get the declaration of the parser function.  */
  55 #define ENTNAME grent
  56 #define STRUCTURE group
  57 #define EXTERN_PARSER
  58 #include <nss/nss_files/files-parse.c>
  59
  60 /* Structure for remembering -group members ... */
  61 #define BLACKLIST_INITIAL_SIZE 512
  62 #define BLACKLIST_INCREMENT 256
  63 struct blacklist_t
  64 {
  65   char *data;
  66   int current;
  67   int size;
  68 };
  69
  70 struct ent_t
  71 {
  72   bool files;
  73   bool need_endgrent;
  74   bool skip_initgroups_dyn;
  75   FILE *stream;
  76   struct blacklist_t blacklist;
  77 };
  78 typedef struct ent_t ent_t;
  79
  80
  81 /* Positive if O_CLOEXEC is supported, negative if it is not supported,
  82    zero if it is still undecided.  This variable is shared with the
  83    other compat functions.  */
  84 #ifdef __ASSUME_O_CLOEXEC
  85 # define __compat_have_cloexec 1
  86 #else
  87 # ifdef O_CLOEXEC
  88 extern int __compat_have_cloexec;
  89 # else
  90 #  define __compat_have_cloexec -1
  91 # endif
  92 #endif
  93
  94 /* Prototypes for local functions.  */
  95 static void blacklist_store_name (const char *, ent_t *);
  96 static int in_blacklist (const char *, int, ent_t *);
  97
  98 /* Initialize the NSS interface/functions. The calling function must
  99    hold the lock.  */
 100 static void
 101 init_nss_interface (void)
 102 {
 103   __libc_lock_lock (lock);
 104
 105   /* Retest.  */
 106   if (ni == NULL
 107       && __nss_database_lookup ("group_compat", NULL, "nis", &ni) >= 0)
 108     {
 109       nss_initgroups_dyn = __nss_lookup_function (ni, "initgroups_dyn");
 110       nss_getgrnam_r = __nss_lookup_function (ni, "getgrnam_r");
 111       nss_getgrgid_r = __nss_lookup_function (ni, "getgrgid_r");
 112       nss_setgrent = __nss_lookup_function (ni, "setgrent");
 113       nss_getgrent_r = __nss_lookup_function (ni, "getgrent_r");
 114       nss_endgrent = __nss_lookup_function (ni, "endgrent");
 115     }
 116
 117   __libc_lock_unlock (lock);
 118 }
 119
 120 static enum nss_status
 121 internal_setgrent (ent_t *ent)
 122 {
 123   enum nss_status status = NSS_STATUS_SUCCESS;
 124
 125   ent->files = true;
 126
 127   if (ni == NULL)
 128     init_nss_interface ();
 129
 130   if (ent->blacklist.data != NULL)
 131     {
 132       ent->blacklist.current = 1;
 133       ent->blacklist.data[0] = '|';
 134       ent->blacklist.data[1] = '\0';
 135     }
 136   else
 137     ent->blacklist.current = 0;
 138
 139   ent->stream = fopen ("/etc/group", "rme");
 140
 141   if (ent->stream == NULL)
 142     status = errno == EAGAIN ? NSS_STATUS_TRYAGAIN : NSS_STATUS_UNAVAIL;
 143   else
 144     {
 145       /* We have to make sure the file is  `closed on exec'.  */
 146       int result = 0;
 147
 148       if (__compat_have_cloexec <= 0)
 149         {
 150           int flags;
 151           result = flags = fcntl (fileno_unlocked (ent->stream), F_GETFD, 0);
 152           if (result >= 0)
 153             {
 154 #if defined O_CLOEXEC && !defined __ASSUME_O_CLOEXEC
 155               if (__compat_have_cloexec == 0)
 156                 __compat_have_cloexec = (flags & FD_CLOEXEC) ? 1 : -1;
 157
 158               if (__compat_have_cloexec < 0)
 159 #endif
 160                 {
 161                   flags |= FD_CLOEXEC;
 162                   result = fcntl (fileno_unlocked (ent->stream), F_SETFD,
 163                                   flags);
 164                 }
 165             }
 166         }
 167
 168       if (result < 0)
 169         {
 170           /* Something went wrong.  Close the stream and return a
 171              failure.  */
 172           fclose (ent->stream);
 173           ent->stream = NULL;
 174           status = NSS_STATUS_UNAVAIL;
 175         }
 176       else
 177         /* We take care of locking ourself.  */
 178         __fsetlocking (ent->stream, FSETLOCKING_BYCALLER);
 179     }
 180
 181   return status;
 182 }
 183
 184
 185 static enum nss_status
 186 internal_endgrent (ent_t *ent)
 187 {
 188   if (ent->stream != NULL)
 189     {
 190       fclose (ent->stream);
 191       ent->stream = NULL;
 192     }
 193
 194   if (ent->blacklist.data != NULL)
 195     {
 196       ent->blacklist.current = 1;
 197       ent->blacklist.data[0] = '|';
 198       ent->blacklist.data[1] = '\0';
 199     }
 200   else
 201     ent->blacklist.current = 0;
 202
 203   if (ent->need_endgrent && nss_endgrent != NULL)
 204     nss_endgrent ();
 205
 206   return NSS_STATUS_SUCCESS;
 207 }
 208
 209 /* Add new group record.  */
 210 static void
 211 add_group (long int *start, long int *size, gid_t **groupsp, long int limit,
 212            gid_t gid)
 213 {
 214   gid_t *groups = *groupsp;
 215
 216   /* Matches user.  Insert this group.  */
 217   if (__glibc_unlikely (*start == *size))
 218     {
 219       /* Need a bigger buffer.  */
 220       gid_t *newgroups;
 221       long int newsize;
 222
 223       if (limit > 0 && *size == limit)
 224         /* We reached the maximum.  */
 225         return;
 226
 227       if (limit <= 0)
 228         newsize = 2 * *size;
 229       else
 230         newsize = MIN (limit, 2 * *size);
 231
 232       newgroups = realloc (groups, newsize * sizeof (*groups));
 233       if (newgroups == NULL)
 234         return;
 235       *groupsp = groups = newgroups;
 236       *size = newsize;
 237     }
 238
 239   groups[*start] = gid;
 240   *start += 1;
 241 }
 242
 243 /* This function checks, if the user is a member of this group and if
 244    yes, add the group id to the list.  Return nonzero is we couldn't
 245    handle the group because the user is not in the member list.  */
 246 static int
 247 check_and_add_group (const char *user, gid_t group, long int *start,
 248                      long int *size, gid_t **groupsp, long int limit,
 249                      struct group *grp)
 250 {
 251   char **member;
 252
 253   /* Don't add main group to list of groups.  */
 254   if (grp->gr_gid == group)
 255     return 0;
 256
 257   for (member = grp->gr_mem; *member != NULL; ++member)
 258     if (strcmp (*member, user) == 0)
 259       {
 260         add_group (start, size, groupsp, limit, grp->gr_gid);
 261         return 0;
 262       }
 263
 264   return 1;
 265 }
 266
 267 /* Get the next group from NSS  (+ entry). If the NSS module supports
 268    initgroups_dyn, get all entries at once.  */
 269 static enum nss_status
 270 getgrent_next_nss (ent_t *ent, char *buffer, size_t buflen, const char *user,
 271                    gid_t group, long int *start, long int *size,
 272                    gid_t **groupsp, long int limit, int *errnop)
 273 {
 274   enum nss_status status;
 275   struct group grpbuf;
 276
 277   /* Try nss_initgroups_dyn if supported. We also need getgrgid_r.
 278      If this function is not supported, step through the whole group
 279      database with getgrent_r.  */
 280   if (! ent->skip_initgroups_dyn)
 281     {
 282       long int mystart = 0;
 283       long int mysize = limit <= 0 ? *size : limit;
 284       gid_t *mygroups = malloc (mysize * sizeof (gid_t));
 285
 286       if (mygroups == NULL)
 287         return NSS_STATUS_TRYAGAIN;
 288
 289       /* For every gid in the list we get from the NSS module,
 290          get the whole group entry. We need to do this, since we
 291          need the group name to check if it is in the blacklist.
 292          In worst case, this is as twice as slow as stepping with
 293          getgrent_r through the whole group database. But for large
 294          group databases this is faster, since the user can only be
 295          in a limited number of groups.  */
 296       if (nss_initgroups_dyn (user, group, &mystart, &mysize, &mygroups,
 297                               limit, errnop) == NSS_STATUS_SUCCESS)
 298         {
 299           status = NSS_STATUS_NOTFOUND;
 300
 301           /* If there is no blacklist we can trust the underlying
 302              initgroups implementation.  */
 303           if (ent->blacklist.current <= 1)
 304             for (int i = 0; i < mystart; i++)
 305               add_group (start, size, groupsp, limit, mygroups[i]);
 306           else
 307             {
 308               /* A temporary buffer. We use the normal buffer, until we find
 309                  an entry, for which this buffer is to small.  In this case, we
 310                  overwrite the pointer with one to a bigger buffer.  */
 311               char *tmpbuf = buffer;
 312               size_t tmplen = buflen;
 313               bool use_malloc = false;
 314
 315               for (int i = 0; i < mystart; i++)
 316                 {
 317                   while ((status = nss_getgrgid_r (mygroups[i], &grpbuf,
 318                                                    tmpbuf, tmplen, errnop))
 319                          == NSS_STATUS_TRYAGAIN
 320                          && *errnop == ERANGE)
 321                     {
 322                       if (__libc_use_alloca (tmplen * 2))
 323                         {
 324                           if (tmpbuf == buffer)
 325                             {
 326                               tmplen *= 2;
 327                               tmpbuf = __alloca (tmplen);
 328                             }
 329                           else
 330                             tmpbuf = extend_alloca (tmpbuf, tmplen, tmplen * 2);
 331                         }
 332                       else
 333                         {
 334                           tmplen *= 2;
 335                           char *newbuf = realloc (use_malloc ? tmpbuf : NULL, tmplen);
 336
 337                           if (newbuf == NULL)
 338                             {
 339                               status = NSS_STATUS_TRYAGAIN;
 340                               goto done;
 341                             }
 342                           use_malloc = true;
 343                           tmpbuf = newbuf;
 344                         }
 345                     }
 346
 347                   if (__builtin_expect  (status != NSS_STATUS_NOTFOUND, 1))
 348                     {
 349                       if (__builtin_expect  (status != NSS_STATUS_SUCCESS, 0))
 350                         goto done;
 351
 352                       if (!in_blacklist (grpbuf.gr_name,
 353                                          strlen (grpbuf.gr_name), ent)
 354                           && check_and_add_group (user, group, start, size,
 355                                                   groupsp, limit, &grpbuf))
 356                         {
 357                           if (nss_setgrent != NULL)
 358                             {
 359                               nss_setgrent (1);
 360                               ent->need_endgrent = true;
 361                             }
 362                           ent->skip_initgroups_dyn = true;
 363
 364                           goto iter;
 365                         }
 366                     }
 367                 }
 368
 369               status = NSS_STATUS_NOTFOUND;
 370
 371  done:
 372               if (use_malloc)
 373                 free (tmpbuf);
 374             }
 375
 376           free (mygroups);
 377
 378           return status;
 379         }
 380
 381       free (mygroups);
 382     }
 383
 384   /* If we come here, the NSS module does not support initgroups_dyn
 385      or we were confronted with a split group.  In these cases we have
 386      to step through the whole list ourself.  */
 387  iter:
 388   do
 389     {
 390       if ((status = nss_getgrent_r (&grpbuf, buffer, buflen, errnop)) !=
 391           NSS_STATUS_SUCCESS)
 392         break;
 393     }
 394   while (in_blacklist (grpbuf.gr_name, strlen (grpbuf.gr_name), ent));
 395
 396   if (status == NSS_STATUS_SUCCESS)
 397     check_and_add_group (user, group, start, size, groupsp, limit, &grpbuf);
 398
 399   return status;
 400 }
 401
 402 static enum nss_status
 403 internal_getgrent_r (ent_t *ent, char *buffer, size_t buflen, const char *user,
 404                      gid_t group, long int *start, long int *size,
 405                      gid_t **groupsp, long int limit, int *errnop)
 406 {
 407   struct parser_data *data = (void *) buffer;
 408   struct group grpbuf;
 409
 410   if (!ent->files)
 411     return getgrent_next_nss (ent, buffer, buflen, user, group,
 412                               start, size, groupsp, limit, errnop);
 413
 414   while (1)
 415     {
 416       fpos_t pos;
 417       int parse_res = 0;
 418       char *p;
 419
 420       do
 421         {
 422           /* We need at least 3 characters for one line.  */
 423           if (__glibc_unlikely (buflen < 3))
 424             {
 425             erange:
 426               *errnop = ERANGE;
 427               return NSS_STATUS_TRYAGAIN;
 428             }
 429
 430           fgetpos (ent->stream, &pos);
 431           buffer[buflen - 1] = '\xff';
 432           p = fgets_unlocked (buffer, buflen, ent->stream);
 433           if (p == NULL && feof_unlocked (ent->stream))
 434             return NSS_STATUS_NOTFOUND;
 435
 436           if (p == NULL || __builtin_expect (buffer[buflen - 1] != '\xff', 0))
 437             {
 438             erange_reset:
 439               fsetpos (ent->stream, &pos);
 440               goto erange;
 441             }
 442
 443           /* Terminate the line for any case.  */
 444           buffer[buflen - 1] = '\0';
 445
 446           /* Skip leading blanks.  */
 447           while (isspace (*p))
 448             ++p;
 449         }
 450       while (*p == '\0' || *p == '#' || /* Ignore empty and comment lines. */
 451              /* Parse the line.  If it is invalid, loop to
 452                 get the next line of the file to parse.  */
 453              !(parse_res = _nss_files_parse_grent (p, &grpbuf, data, buflen,
 454                                                    errnop)));
 455
 456       if (__glibc_unlikely (parse_res == -1))
 457         /* The parser ran out of space.  */
 458         goto erange_reset;
 459
 460       if (grpbuf.gr_name[0] != '+' && grpbuf.gr_name[0] != '-')
 461         /* This is a real entry.  */
 462         break;
 463
 464       /* -group */
 465       if (grpbuf.gr_name[0] == '-' && grpbuf.gr_name[1] != '\0'
 466           && grpbuf.gr_name[1] != '@')
 467         {
 468           blacklist_store_name (&grpbuf.gr_name[1], ent);
 469           continue;
 470         }
 471
 472       /* +group */
 473       if (grpbuf.gr_name[0] == '+' && grpbuf.gr_name[1] != '\0'
 474           && grpbuf.gr_name[1] != '@')
 475         {
 476           if (in_blacklist (&grpbuf.gr_name[1],
 477                             strlen (&grpbuf.gr_name[1]), ent))
 478             continue;
 479           /* Store the group in the blacklist for the "+" at the end of
 480              /etc/group */
 481           blacklist_store_name (&grpbuf.gr_name[1], ent);
 482           if (nss_getgrnam_r == NULL)
 483             return NSS_STATUS_UNAVAIL;
 484           else if (nss_getgrnam_r (&grpbuf.gr_name[1], &grpbuf, buffer,
 485                                    buflen, errnop) != NSS_STATUS_SUCCESS)
 486             continue;
 487
 488           check_and_add_group (user, group, start, size, groupsp,
 489                                limit, &grpbuf);
 490
 491           return NSS_STATUS_SUCCESS;
 492         }
 493
 494       /* +:... */
 495       if (grpbuf.gr_name[0] == '+' && grpbuf.gr_name[1] == '\0')
 496         {
 497           /* If the selected module does not support getgrent_r or
 498              initgroups_dyn, abort. We cannot find the needed group
 499              entries.  */
 500           if (nss_initgroups_dyn == NULL || nss_getgrgid_r == NULL)
 501             {
 502               if (nss_setgrent != NULL)
 503                 {
 504                   nss_setgrent (1);
 505                   ent->need_endgrent = true;
 506                 }
 507               ent->skip_initgroups_dyn = true;
 508
 509               if (nss_getgrent_r == NULL)
 510                 return NSS_STATUS_UNAVAIL;
 511             }
 512
 513           ent->files = false;
 514
 515           return getgrent_next_nss (ent, buffer, buflen, user, group,
 516                                     start, size, groupsp, limit, errnop);
 517         }
 518     }
 519
 520   check_and_add_group (user, group, start, size, groupsp, limit, &grpbuf);
 521
 522   return NSS_STATUS_SUCCESS;
 523 }
 524
 525
 526 enum nss_status
 527 _nss_compat_initgroups_dyn (const char *user, gid_t group, long int *start,
 528                             long int *size, gid_t **groupsp, long int limit,
 529                             int *errnop)
 530 {
 531   size_t buflen = sysconf (_SC_GETPW_R_SIZE_MAX);
 532   char *tmpbuf;
 533   enum nss_status status;
 534   ent_t intern = { true, false, false, NULL, {NULL, 0, 0} };
 535   bool use_malloc = false;
 536
 537   status = internal_setgrent (&intern);
 538   if (status != NSS_STATUS_SUCCESS)
 539     return status;
 540
 541   tmpbuf = __alloca (buflen);
 542
 543   do
 544     {
 545       while ((status = internal_getgrent_r (&intern, tmpbuf, buflen,
 546                                             user, group, start, size,
 547                                             groupsp, limit, errnop))
 548              == NSS_STATUS_TRYAGAIN && *errnop == ERANGE)
 549         if (__libc_use_alloca (buflen * 2))
 550           tmpbuf = extend_alloca (tmpbuf, buflen, 2 * buflen);
 551         else
 552           {
 553             buflen *= 2;
 554             char *newbuf = realloc (use_malloc ? tmpbuf : NULL, buflen);
 555             if (newbuf == NULL)
 556               {
 557                 status = NSS_STATUS_TRYAGAIN;
 558                 goto done;
 559               }
 560             use_malloc = true;
 561             tmpbuf = newbuf;
 562           }
 563     }
 564   while (status == NSS_STATUS_SUCCESS);
 565
 566   status = NSS_STATUS_SUCCESS;
 567
 568  done:
 569   if (use_malloc)
 570     free (tmpbuf);
 571
 572   internal_endgrent (&intern);
 573
 574   return status;
 575 }
 576
 577
 578 /* Support routines for remembering -@netgroup and -user entries.
 579    The names are stored in a single string with `|' as separator. */
 580 static void
 581 blacklist_store_name (const char *name, ent_t *ent)
 582 {
 583   int namelen = strlen (name);
 584   char *tmp;
 585
 586   /* First call, setup cache.  */
 587   if (ent->blacklist.size == 0)
 588     {
 589       ent->blacklist.size = MAX (BLACKLIST_INITIAL_SIZE, 2 * namelen);
 590       ent->blacklist.data = malloc (ent->blacklist.size);
 591       if (ent->blacklist.data == NULL)
 592         return;
 593       ent->blacklist.data[0] = '|';
 594       ent->blacklist.data[1] = '\0';
 595       ent->blacklist.current = 1;
 596     }
 597   else
 598     {
 599       if (in_blacklist (name, namelen, ent))
 600         return;                 /* no duplicates */
 601
 602       if (ent->blacklist.current + namelen + 1 >= ent->blacklist.size)
 603         {
 604           ent->blacklist.size += MAX (BLACKLIST_INCREMENT, 2 * namelen);
 605           tmp = realloc (ent->blacklist.data, ent->blacklist.size);
 606           if (tmp == NULL)
 607             {
 608               free (ent->blacklist.data);
 609               ent->blacklist.size = 0;
 610               return;
 611             }
 612           ent->blacklist.data = tmp;
 613         }
 614     }
 615
 616   tmp = stpcpy (ent->blacklist.data + ent->blacklist.current, name);
 617   *tmp++ = '|';
 618   *tmp = '\0';
 619   ent->blacklist.current += namelen + 1;
 620
 621   return;
 622 }
 623
 624 /* returns TRUE if ent->blacklist contains name, else FALSE */
 625 static bool_t
 626 in_blacklist (const char *name, int namelen, ent_t *ent)
 627 {
 628   char buf[namelen + 3];
 629   char *cp;
 630
 631   if (ent->blacklist.data == NULL)
 632     return FALSE;
 633
 634   buf[0] = '|';
 635   cp = stpcpy (&buf[1], name);
 636   *cp++ = '|';
 637   *cp = '\0';
 638   return strstr (ent->blacklist.data, buf) != NULL;
 639 }