/* Mail alias file parser in nss_files module.

   Copyright (C) 1996-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.

   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 <aliases.h>

#include <ctype.h>

#include <errno.h>

#include <fcntl.h>

#include <libc-lock.h>

#include <stdlib.h>

#include <stdio.h>

#include <string.h>

#include <kernel-features.h>

#include "nsswitch.h"

#include <nss_files.h>

/* Locks the static variables in this file.  */

__libc_lock_define_initialized (static, lock)

/* Maintenance of the stream open on the database file.  For getXXent

   operations the stream needs to be held open across calls, the other

   getXXbyYY operations all use their own stream.  */

static FILE *stream;

static enum nss_status

internal_setent (FILE **stream)

{

  enum nss_status status = NSS_STATUS_SUCCESS;

  if (*stream == NULL)

    {

      *stream = __nss_files_fopen ("/etc/aliases");

      if (*stream == NULL)

	status = errno == EAGAIN ? NSS_STATUS_TRYAGAIN : NSS_STATUS_UNAVAIL;

    }

  else

    rewind (*stream);

  return status;

}

/* Thread-safe, exported version of that.  */

enum nss_status

_nss_files_setaliasent (void)

{

  enum nss_status status;

  __libc_lock_lock (lock);

  status = internal_setent (&stream);

  __libc_lock_unlock (lock);

  return status;

}

/* Close the database file.  */

static void

internal_endent (FILE **stream)

{

  if (*stream != NULL)

    {

      fclose (*stream);

      *stream = NULL;

    }

}

/* Thread-safe, exported version of that.  */

enum nss_status

_nss_files_endaliasent (void)

{

  __libc_lock_lock (lock);

  internal_endent (&stream);

  __libc_lock_unlock (lock);

  return NSS_STATUS_SUCCESS;

}

/* Parsing the database file into `struct aliasent' data structures.  */

static enum nss_status

get_next_alias (FILE *stream, const char *match, struct aliasent *result,

		char *buffer, size_t buflen, int *errnop)

{

  enum nss_status status = NSS_STATUS_NOTFOUND;

  int ignore = 0;

  result->alias_members_len = 0;

  while (1)

    {

      /* Now we are ready to process the input.  We have to read a

	 line and all its continuations and construct the array of

	 string pointers.  This pointers and the names itself have to

	 be placed in BUFFER.  */

      char *first_unused = buffer;

      size_t room_left = buflen - (buflen % __alignof__ (char *));

      char *line;

      /* Check whether the buffer is large enough for even trying to

	 read something.  */

      if (room_left < 2)

	goto no_more_room;

      /* Read the first line.  It must contain the alias name and

	 possibly some alias names.  */

      first_unused[room_left - 1] = '\xff';

      line = fgets_unlocked (first_unused, room_left, stream);

      if (line == NULL)

	/* Nothing to read.  */

	break;

      else if (first_unused[room_left - 1] != '\xff')

	{

	  /* The line is too long for our buffer.  */

	no_more_room:

	  *errnop = ERANGE;

	  status = NSS_STATUS_TRYAGAIN;

	  break;

	}

      else

	{

	  char *cp;

	  /* If we are in IGNORE mode and the first character in the

	     line is a white space we ignore the line and start

	     reading the next.  */

	  if (ignore && isspace (*first_unused))

	    continue;

	  /* Terminate the line for any case.  */

	  cp = strpbrk (first_unused, "#\n");

	  if (cp != NULL)

	    *cp = '\0';

	  /* Skip leading blanks.  */

	  while (isspace (*line))

	    ++line;

	  result->alias_name = first_unused;

	  while (*line != '\0' && *line != ':')

	    *first_unused++ = *line++;

	  if (*line == '\0' || result->alias_name == first_unused)

	    /* No valid name.  Ignore the line.  */

	    continue;

	  *first_unused++ = '\0';

	  if (room_left < (size_t) (first_unused - result->alias_name))

	    goto no_more_room;

	  room_left -= first_unused - result->alias_name;

	  ++line;

	  /* When we search for a specific alias we can avoid all the

	     difficult parts and compare now with the name we are

	     looking for.  If it does not match we simply ignore all

	     lines until the next line containing the start of a new

	     alias is found.  */

	  ignore = (match != NULL

		    && __strcasecmp (result->alias_name, match) != 0);

	  while (! ignore)

	    {

	      while (isspace (*line))

		++line;

	      cp = first_unused;

	      while (*line != '\0' && *line != ',')

		*first_unused++ = *line++;

	      if (first_unused != cp)

		{

		  /* OK, we can have a regular entry or an include

		     request.  */

		  if (*line != '\0')

		    ++line;

		  *first_unused++ = '\0';

		  if (strncmp (cp, ":include:", 9) != 0)

		    {

		      if (room_left < (first_unused - cp) + sizeof (char *))

			goto no_more_room;

		      room_left -= (first_unused - cp) + sizeof (char *);

		      ++result->alias_members_len;

		    }

		  else

		    {

		      /* Oh well, we have to read the addressed file.  */

		      FILE *listfile;

		      char *old_line = NULL;

		      first_unused = cp;

		      listfile = __nss_files_fopen (&cp[9]);

		      /* If the file does not exist we simply ignore

			 the statement.  */

		      if (listfile != NULL

			  && (old_line = strdup (line)) != NULL)

			{

			  while (! feof_unlocked (listfile))

			    {

			      if (room_left < 2)

				{

				  free (old_line);

				  fclose (listfile);

				  goto no_more_room;

				}

			      first_unused[room_left - 1] = '\xff';

			      line = fgets_unlocked (first_unused, room_left,

						     listfile);

			      if (line == NULL)

				break;

			      if (first_unused[room_left - 1] != '\xff')

				{

				  free (old_line);

				  fclose (listfile);

				  goto no_more_room;

				}

			      /* Parse the line.  */

			      cp = strpbrk (line, "#\n");

			      if (cp != NULL)

				*cp = '\0';

			      do

				{

				  while (isspace (*line))

				    ++line;

				  cp = first_unused;

				  while (*line != '\0' && *line != ',')

				    *first_unused++ = *line++;

				  if (*line != '\0')

				    ++line;

				  if (first_unused != cp)

				    {

				      *first_unused++ = '\0';

				      if (room_left < ((first_unused - cp)

						       + __alignof__ (char *)))

					{

					  free (old_line);

					  fclose (listfile);

					  goto no_more_room;

					}

				      room_left -= ((first_unused - cp)

						    + __alignof__ (char *));

				      ++result->alias_members_len;

				    }

				}

			      while (*line != '\0');

			    }

			  fclose (listfile);

			  first_unused[room_left - 1] = '\0';

			  strncpy (first_unused, old_line, room_left);

			  free (old_line);

			  line = first_unused;

			  if (first_unused[room_left - 1] != '\0')

			    goto no_more_room;

			}

		    }

		}

	      if (*line == '\0')

		{

		  /* Get the next line.  But we must be careful.  We

		     must not read the whole line at once since it

		     might belong to the current alias.  Simply read

		     the first character.  If it is a white space we

		     have a continuation line.  Otherwise it is the

		     beginning of a new alias and we can push back the

		     just read character.  */

		  int ch;

		  ch = fgetc_unlocked (stream);

		  if (ch == EOF || ch == '\n' || !isspace (ch))

		    {

		      size_t cnt;

		      /* Now prepare the return.  Provide string

			 pointers for the currently selected aliases.  */

		      if (ch != EOF)

			ungetc (ch, stream);

		      /* Adjust the pointer so it is aligned for

			 storing pointers.  */

		      first_unused += __alignof__ (char *) - 1;

		      first_unused -= ((first_unused - (char *) 0)

				       % __alignof__ (char *));

		      result->alias_members = (char **) first_unused;

		      /* Compute addresses of alias entry strings.  */

		      cp = result->alias_name;

		      for (cnt = 0; cnt < result->alias_members_len; ++cnt)

			{

			  cp = strchr (cp, '\0') + 1;

			  result->alias_members[cnt] = cp;

			}

		      status = (result->alias_members_len == 0

				? NSS_STATUS_RETURN : NSS_STATUS_SUCCESS);

		      break;

		    }

		  /* The just read character is a white space and so

		     can be ignored.  */

		  first_unused[room_left - 1] = '\xff';

		  line = fgets_unlocked (first_unused, room_left, stream);

		  if (first_unused[room_left - 1] != '\xff')

		    goto no_more_room;

		  cp = strpbrk (line, "#\n");

		  if (cp != NULL)

		    *cp = '\0';

		}

	    }

	}

      if (status != NSS_STATUS_NOTFOUND)

	/* We read something.  In any case break here.  */

	break;

    }

  return status;

}

enum nss_status

_nss_files_getaliasent_r (struct aliasent *result, char *buffer, size_t buflen,

			  int *errnop)

{

  /* Return next entry in host file.  */

  enum nss_status status = NSS_STATUS_SUCCESS;

  __libc_lock_lock (lock);

  /* Be prepared that the set*ent function was not called before.  */

  if (stream == NULL)

    status = internal_setent (&stream);

  if (status == NSS_STATUS_SUCCESS)

    {

      result->alias_local = 1;

      /* Read lines until we get a definite result.  */

      do

	status = get_next_alias (stream, NULL, result, buffer, buflen, errnop);

      while (status == NSS_STATUS_RETURN);

    }

  __libc_lock_unlock (lock);

  return status;

}

enum nss_status

_nss_files_getaliasbyname_r (const char *name, struct aliasent *result,

			     char *buffer, size_t buflen, int *errnop)

{

  /* Return next entry in host file.  */

  enum nss_status status = NSS_STATUS_SUCCESS;

  FILE *stream = NULL;

  if (name == NULL)

    {

      __set_errno (EINVAL);

      return NSS_STATUS_UNAVAIL;

    }

  /* Open the stream.  */

  status = internal_setent (&stream);

  if (status == NSS_STATUS_SUCCESS)

    {

      result->alias_local = 1;

      /* Read lines until we get a definite result.  */

      do

	status = get_next_alias (stream, name, result, buffer, buflen, errnop);

      while (status == NSS_STATUS_RETURN);

    }

  internal_endent (&stream);

  return status;

}