resolv/res_context_hostalias.c

   1 /* HOSTALIASES-based name resolution.  Internal function.
   2    Copyright (C) 2015-2022 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   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    <https://www.gnu.org/licenses/>.  */
  18
  19 /*
  20  * Copyright (c) 1988, 1993
  21  *    The Regents of the University of California.  All rights reserved.
  22  *
  23  * Redistribution and use in source and binary forms, with or without
  24  * modification, are permitted provided that the following conditions
  25  * are met:
  26  * 1. Redistributions of source code must retain the above copyright
  27  *    notice, this list of conditions and the following disclaimer.
  28  * 2. Redistributions in binary form must reproduce the above copyright
  29  *    notice, this list of conditions and the following disclaimer in the
  30  *    documentation and/or other materials provided with the distribution.
  31  * 4. Neither the name of the University nor the names of its contributors
  32  *    may be used to endorse or promote products derived from this software
  33  *    without specific prior written permission.
  34  *
  35  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  36  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  37  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  38  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  39  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  40  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  41  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  42  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  43  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  44  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  45  * SUCH DAMAGE.
  46  */
  47
  48 /*
  49  * Portions Copyright (c) 1993 by Digital Equipment Corporation.
  50  *
  51  * Permission to use, copy, modify, and distribute this software for any
  52  * purpose with or without fee is hereby granted, provided that the above
  53  * copyright notice and this permission notice appear in all copies, and that
  54  * the name of Digital Equipment Corporation not be used in advertising or
  55  * publicity pertaining to distribution of the document or software without
  56  * specific, written prior permission.
  57  *
  58  * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
  59  * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
  60  * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
  61  * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  62  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  63  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  64  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  65  * SOFTWARE.
  66  */
  67
  68 /*
  69  * Portions Copyright (c) 1996-1999 by Internet Software Consortium.
  70  *
  71  * Permission to use, copy, modify, and distribute this software for any
  72  * purpose with or without fee is hereby granted, provided that the above
  73  * copyright notice and this permission notice appear in all copies.
  74  *
  75  * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
  76  * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
  77  * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
  78  * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  79  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  80  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  81  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  82  * SOFTWARE.
  83  */
  84
  85 #include <arpa/nameser.h>
  86 #include <ctype.h>
  87 #include <resolv-internal.h>
  88 #include <resolv_context.h>
  89 #include <stdio.h>
  90 #include <stdlib.h>
  91 #include <string.h>
  92
  93 const char *
  94 __res_context_hostalias (struct resolv_context *ctx,
  95                          const char *name, char *dst, size_t siz)
  96 {
  97   char *file, *cp1, *cp2;
  98   char buf[BUFSIZ];
  99   FILE *fp;
 100
 101   if (ctx->resp->options & RES_NOALIASES)
 102     return NULL;
 103   file = getenv ("HOSTALIASES");
 104   if (file == NULL || (fp = fopen (file, "rce")) == NULL)
 105     return NULL;
 106   buf[sizeof (buf) - 1] = '\0';
 107   while (__fgets_unlocked (buf, sizeof (buf), fp))
 108     {
 109       for (cp1 = buf; *cp1 && !isspace (*cp1); ++cp1)
 110         ;
 111       if (!*cp1)
 112         break;
 113       *cp1 = '\0';
 114       if (__libc_ns_samename (buf, name) == 1)
 115         {
 116           while (isspace (*++cp1))
 117             ;
 118           if (!*cp1)
 119             break;
 120           for (cp2 = cp1 + 1; *cp2 && !isspace (*cp2); ++cp2)
 121             ;
 122           *cp2 = '\0';
 123           strncpy (dst, cp1, siz - 1);
 124           dst[siz - 1] = '\0';
 125           fclose (fp);
 126           return dst;
 127         }
 128     }
 129   fclose (fp);
 130   return NULL;
 131 }
 132 libc_hidden_def (__res_context_hostalias)