glibc/nis/nss_nis/nis-initgroups.c

/* Copyright (C) 1998-2017 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Thorsten Kukuk <kukuk@suse.de>, 1998.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <http://www.gnu.org/licenses/>.  */

#include <alloca.h>
#include <ctype.h>
#include <errno.h>
#include <grp.h>
#include <nss.h>
#include <pwd.h>
#include <string.h>
#include <unistd.h>
#include <rpcsvc/yp.h>
#include <rpcsvc/ypclnt.h>
#include <sys/param.h>

#include "nss-nis.h"
#include <libnsl.h>

/* Get the declaration of the parser function.  */
#define ENTNAME grent
#define STRUCTURE group
#define EXTERN_PARSER
#include <nss/nss_files/files-parse.c>


static enum nss_status
internal_setgrent (char *domainname, intern_t *intern)
{
  struct ypall_callback ypcb;
  enum nss_status status;

  ypcb.foreach = _nis_saveit;
  ypcb.data = (char *) intern;
  status = yperr2nss (yp_all (domainname, "group.byname", &ypcb));

  /* Mark the last buffer as full.  */
  if (intern->next != NULL)
    intern->next->size = intern->offset;

  intern->next = intern->start;
  intern->offset = 0;

  return status;
}


static enum nss_status
internal_getgrent_r (struct group *grp, char *buffer, size_t buflen,
		     int *errnop, intern_t *intern)
{
  if (intern->start == NULL)
    return NSS_STATUS_NOTFOUND;

  /* Get the next entry until we found a correct one. */
  int parse_res;
  do
    {
      struct response_t *bucket = intern->next;

      if (__glibc_unlikely (intern->offset >= bucket->size))
	{
	  if (bucket->next == NULL)
	    return NSS_STATUS_NOTFOUND;

	  /* We look at all the content in the current bucket.  Go on
	     to the next.  */
	  bucket = intern->next = bucket->next;
	  intern->offset = 0;
	}

      char *p;
      for (p = &bucket->mem[intern->offset]; isspace (*p); ++p)
        ++intern->offset;

      size_t len = strlen (p) + 1;
      if (__glibc_unlikely (len > buflen))
	{
	  *errnop = ERANGE;
	  return NSS_STATUS_TRYAGAIN;
	}

      /* We unfortunately have to copy the data in the user-provided
	 buffer because that buffer might be around for a very long
	 time and the servent structure must remain valid.  If we would
	 rely on the BUCKET memory the next 'setservent' or 'endservent'
	 call would destroy it.

	 The important thing is that it is a single NUL-terminated
	 string.  This is what the parsing routine expects.  */
      p = memcpy (buffer, &bucket->mem[intern->offset], len);

      parse_res = _nss_files_parse_grent (p, grp, (void *) buffer, buflen,
					  errnop);
      if (__glibc_unlikely (parse_res == -1))
        return NSS_STATUS_TRYAGAIN;

      intern->offset += len;
    }
  while (!parse_res);

  return NSS_STATUS_SUCCESS;
}


static int
get_uid (const char *user, uid_t *uidp)
{
  size_t buflen = sysconf (_SC_GETPW_R_SIZE_MAX);
  char *buf = (char *) alloca (buflen);

  while (1)
    {
      struct passwd result;
      struct passwd *resp;

      int r = getpwnam_r (user, &result, buf, buflen, &resp);
      if (r == 0 && resp != NULL)
	{
	  *uidp = resp->pw_uid;
	  return 0;
	}

      if (r != ERANGE)
	break;

      buf = extend_alloca (buf, buflen, 2 * buflen);
    }

  return 1;
}


static enum nss_status
initgroups_netid (uid_t uid, gid_t group, long int *start, long int *size,
		  gid_t **groupsp, long int limit, int *errnop,
		  const char *domainname)
{
  /* Limit domainname length to the maximum size of an RPC packet.  */
  if (strlen (domainname) > UDPMSGSIZE)
    {
      *errnop = ERANGE;
      return NSS_STATUS_UNAVAIL;
    }

  /* Prepare the key.  The form is "unix.UID@DOMAIN" with the UID and
     DOMAIN field filled in appropriately.  */
  char key[sizeof ("unix.@") + sizeof (uid_t) * 3 + strlen (domainname)];
  ssize_t keylen = snprintf (key, sizeof (key), "unix.%lu@%s",
			     (unsigned long int) uid, domainname);

  char *result;
  int reslen;
  int yperr = yp_match (domainname, "netid.byname", key, keylen, &result,
			&reslen);
  if (__glibc_unlikely (yperr != YPERR_SUCCESS))
    return yperr2nss (yperr);

  /* Parse the result: following the colon is a comma separated list of
     group IDs.  */
  char *cp = strchr (result, ':');
  if (cp == NULL)
    {
    errout:
      free (result);
      return NSS_STATUS_NOTFOUND;
    }
  /* Skip the colon.  */
  ++cp;

  gid_t *groups = *groupsp;
  while (*cp != '\0')
    {
      char *endp;
      unsigned long int gid = strtoul (cp, &endp, 0);
      if (cp == endp)
	goto errout;
      if (*endp == ',')
	++endp;
      else if (*endp != '\0')
	goto errout;
      cp = endp;

      if (gid == group)
	/* We do not need this group again.  */
	continue;

      /* Insert this group.  */
      if (*start == *size)
	{
	  /* Need a bigger buffer.  */
	  long int newsize;

	  if (limit > 0 && *size == limit)
	    /* We reached the maximum.  */
	    break;

	  if (limit <= 0)
	    newsize = 2 * *size;
	  else
	    newsize = MIN (limit, 2 * *size);

	  gid_t *newgroups = realloc (groups, newsize * sizeof (*groups));
	  if (newgroups == NULL)
	    goto errout;
	  *groupsp = groups = newgroups;
	  *size = newsize;
	}

      groups[*start] = gid;
      *start += 1;
    }

  free (result);

  return NSS_STATUS_SUCCESS;
}


enum nss_status
_nss_nis_initgroups_dyn (const char *user, gid_t group, long int *start,
			 long int *size, gid_t **groupsp, long int limit,
			 int *errnop)
{
  /* We always need the domain name.  */
  char *domainname;
  if (yp_get_default_domain (&domainname))
    return NSS_STATUS_UNAVAIL;

  /* Check whether we are supposed to use the netid.byname map.  */
  if (_nsl_default_nss () & NSS_FLAG_NETID_AUTHORITATIVE)
    {
      /* We need the user ID.  */
      uid_t uid;

      if (get_uid (user, &uid) == 0
	  && initgroups_netid (uid, group, start, size, groupsp, limit,
			       errnop, domainname) == NSS_STATUS_SUCCESS)
	return NSS_STATUS_SUCCESS;
    }

  struct group grpbuf, *g;
  size_t buflen = sysconf (_SC_GETPW_R_SIZE_MAX);
  char *tmpbuf;
  enum nss_status status;
  intern_t intern = { NULL, NULL, 0 };
  gid_t *groups = *groupsp;

  status = internal_setgrent (domainname, &intern);
  if (status != NSS_STATUS_SUCCESS)
    return status;

  tmpbuf = __alloca (buflen);

  while (1)
    {
      while ((status =
	      internal_getgrent_r (&grpbuf, tmpbuf, buflen, errnop,
				   &intern)) == NSS_STATUS_TRYAGAIN
             && *errnop == ERANGE)
	tmpbuf = extend_alloca (tmpbuf, buflen, 2 * buflen);

      if (status != NSS_STATUS_SUCCESS)
	{
	  if (status == NSS_STATUS_NOTFOUND)
	    status = NSS_STATUS_SUCCESS;
	  goto done;
	}

      g = &grpbuf;
      if (g->gr_gid != group)
        {
          char **m;

          for (m = g->gr_mem; *m != NULL; ++m)
            if (strcmp (*m, user) == 0)
              {
                /* Matches user.  Insert this group.  */
                if (*start == *size)
                  {
                    /* Need a bigger buffer.  */
		    gid_t *newgroups;
		    long int newsize;

		    if (limit > 0 && *size == limit)
		      /* We reached the maximum.  */
		      goto done;

		    if (limit <= 0)
		      newsize = 2 * *size;
		    else
		      newsize = MIN (limit, 2 * *size);

		    newgroups = realloc (groups, newsize * sizeof (*groups));
		    if (newgroups == NULL)
		      {
			status = NSS_STATUS_TRYAGAIN;
			*errnop = errno;
			goto done;
		      }
		    *groupsp = groups = newgroups;
                    *size = newsize;
                  }

                groups[*start] = g->gr_gid;
		*start += 1;

                break;
              }
        }
    }

done:
  while (intern.start != NULL)
    {
      intern.next = intern.start;
      intern.start = intern.start->next;
      free (intern.next);
    }

  return status;
}