curl/lib/hostcheck.c

/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 1998 - 2021, Daniel Stenberg, <daniel@haxx.se>, et al.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution. The terms
 * are also available at https://curl.se/docs/copyright.html.
 *
 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
 * copies of the Software, and permit persons to whom the Software is
 * furnished to do so, under the terms of the COPYING file.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 ***************************************************************************/

#include "curl_setup.h"

#if defined(USE_OPENSSL)                                \
  || defined(USE_GSKIT)                                 \
  || defined(USE_SCHANNEL)
/* these backends use functions from this file */

#ifdef HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif
#ifdef HAVE_NETINET_IN6_H
#include <netinet/in6.h>
#endif

#include "hostcheck.h"
#include "strcase.h"
#include "inet_pton.h"

#include "curl_memory.h"
/* The last #include file should be: */
#include "memdebug.h"

/*
 * Match a hostname against a wildcard pattern.
 * E.g.
 *  "foo.host.com" matches "*.host.com".
 *
 * We use the matching rule described in RFC6125, section 6.4.3.
 * https://tools.ietf.org/html/rfc6125#section-6.4.3
 *
 * In addition: ignore trailing dots in the host names and wildcards, so that
 * the names are used normalized. This is what the browsers do.
 *
 * Do not allow wildcard matching on IP numbers. There are apparently
 * certificates being used with an IP address in the CN field, thus making no
 * apparent distinction between a name and an IP. We need to detect the use of
 * an IP address and not wildcard match on such names.
 *
 * NOTE: hostmatch() gets called with copied buffers so that it can modify the
 * contents at will.
 */

static int hostmatch(char *hostname, char *pattern)
{
  const char *pattern_label_end, *pattern_wildcard, *hostname_label_end;
  int wildcard_enabled;
  size_t prefixlen, suffixlen;
  struct in_addr ignored;
#ifdef ENABLE_IPV6
  struct sockaddr_in6 si6;
#endif

  /* normalize pattern and hostname by stripping off trailing dots */
  size_t len = strlen(hostname);
  if(hostname[len-1]=='.')
    hostname[len-1] = 0;
  len = strlen(pattern);
  if(pattern[len-1]=='.')
    pattern[len-1] = 0;

  pattern_wildcard = strchr(pattern, '*');
  if(!pattern_wildcard)
    return strcasecompare(pattern, hostname) ?
      CURL_HOST_MATCH : CURL_HOST_NOMATCH;

  /* detect IP address as hostname and fail the match if so */
  if(Curl_inet_pton(AF_INET, hostname, &ignored) > 0)
    return CURL_HOST_NOMATCH;
#ifdef ENABLE_IPV6
  if(Curl_inet_pton(AF_INET6, hostname, &si6.sin6_addr) > 0)
    return CURL_HOST_NOMATCH;
#endif

  /* We require at least 2 dots in pattern to avoid too wide wildcard
     match. */
  wildcard_enabled = 1;
  pattern_label_end = strchr(pattern, '.');
  if(!pattern_label_end || strchr(pattern_label_end + 1, '.') == NULL ||
     pattern_wildcard > pattern_label_end ||
     strncasecompare(pattern, "xn--", 4)) {
    wildcard_enabled = 0;
  }
  if(!wildcard_enabled)
    return strcasecompare(pattern, hostname) ?
      CURL_HOST_MATCH : CURL_HOST_NOMATCH;

  hostname_label_end = strchr(hostname, '.');
  if(!hostname_label_end ||
     !strcasecompare(pattern_label_end, hostname_label_end))
    return CURL_HOST_NOMATCH;

  /* The wildcard must match at least one character, so the left-most
     label of the hostname is at least as large as the left-most label
     of the pattern. */
  if(hostname_label_end - hostname < pattern_label_end - pattern)
    return CURL_HOST_NOMATCH;

  prefixlen = pattern_wildcard - pattern;
  suffixlen = pattern_label_end - (pattern_wildcard + 1);
  return strncasecompare(pattern, hostname, prefixlen) &&
    strncasecompare(pattern_wildcard + 1, hostname_label_end - suffixlen,
                    suffixlen) ?
    CURL_HOST_MATCH : CURL_HOST_NOMATCH;
}

int Curl_cert_hostcheck(const char *match_pattern, const char *hostname)
{
  int res = 0;
  if(!match_pattern || !*match_pattern ||
      !hostname || !*hostname) /* sanity check */
    ;
  else {
    char *matchp = strdup(match_pattern);
    if(matchp) {
      char *hostp = strdup(hostname);
      if(hostp) {
        if(hostmatch(hostp, matchp) == CURL_HOST_MATCH)
          res = 1;
        free(hostp);
      }
      free(matchp);
    }
  }

  return res;
}

#endif /* OPENSSL, GSKIT or schannel+wince */