src/network/ssl/match-hostname.c

   1 /* Matching a host name to wildcards in SSL certificates */
   2
   3 #ifdef HAVE_CONFIG_H
   4 #include "config.h"
   5 #endif
   6
   7 #include "elinks.h"
   8
   9 #include "intl/charsets.h"
  10 #include "network/ssl/match-hostname.h"
  11 #include "util/conv.h"
  12 #include "util/error.h"
  13 #include "util/string.h"
  14
  15 /** Checks whether a host name matches a pattern that may contain
  16  * wildcards.
  17  *
  18  * @param[in] hostname
  19  *   The host name to which the user wanted to connect.
  20  *   Should be in UTF-8 and need not be null-terminated.
  21  * @param[in] hostname_length
  22  *   The length of @a hostname, in bytes.
  23  * @param[in] pattern
  24  *   A pattern that the host name might match.
  25  *   Should be in UTF-8 and need not be null-terminated.
  26  *   The pattern may contain wildcards, as specified in
  27  *   RFC 2818 section 3.1.
  28  * @param[in] pattern_length
  29  *   The length of @a pattern, in bytes.
  30  *
  31  * @return
  32  *   Nonzero if the host name matches.  Zero if it doesn't.
  33  *
  34  * According to RFC 2818 section 3.1, '*' matches any number of
  35  * characters except '.'.  For example, "*r*.example.org" matches
  36  * "random.example.org" or "history.example.org" but not
  37  * "frozen.fruit.example.org".
  38  *
  39  * This function does not allocate memory, and consumes at most
  40  * O(@a hostname_length * @a pattern_length) time.  */
  41 int
  42 match_hostname_pattern(const unsigned char *hostname,
  43                        size_t hostname_length,
  44                        const unsigned char *pattern,
  45                        size_t pattern_length)
  46 {
  47         const unsigned char *const hostname_end = hostname + hostname_length;
  48         const unsigned char *const pattern_end = pattern + pattern_length;
  49
  50         assert(hostname <= hostname_end);
  51         assert(pattern <= pattern_end);
  52         if_assert_failed return 0;
  53
  54         while (pattern < pattern_end) {
  55                 if (*pattern == '*') {
  56                         const unsigned char *next_wildcard;
  57                         size_t literal_length;
  58
  59                         ++pattern;
  60                         next_wildcard = memchr(pattern, '*',
  61                                                pattern_end - pattern);
  62                         if (next_wildcard == NULL)
  63                                 literal_length = pattern_end - pattern;
  64                         else
  65                                 literal_length = next_wildcard - pattern;
  66
  67                         for (;;) {
  68                                 size_t hostname_left = hostname_end - hostname;
  69                                 unicode_val_T uni;
  70
  71                                 if (hostname_left < literal_length)
  72                                         return 0;
  73
  74                                 /* If next_wildcard == NULL, then the
  75                                  * literal string is at the end of the
  76                                  * pattern, so anchor the match to the
  77                                  * end of the hostname.  The end of
  78                                  * this function can then easily
  79                                  * verify that the whole hostname was
  80                                  * matched.
  81                                  *
  82                                  * But do not jump directly there;
  83                                  * first verify that there are no '.'
  84                                  * characters in between.  */
  85                                 if ((next_wildcard != NULL
  86                                      || hostname_left == literal_length)
  87                                     && !c_strlcasecmp(pattern, literal_length,
  88                                                       hostname, literal_length))
  89                                         break;
  90
  91                                 /* The literal string doesn't match here.
  92                                  * Skip one character of the hostname and
  93                                  * retry.  If the skipped character is '.'
  94                                  * or one of the equivalent characters
  95                                  * listed in RFC 3490 section 3.1
  96                                  * requirement 1, then return 0, because
  97                                  * '*' must not match such characters.
  98                                  * Do the same if invalid UTF-8 is found.
  99                                  * Cast away const.  */
 100                                 uni = utf8_to_unicode((unsigned char **) &hostname,
 101                                                       hostname_end);
 102                                 if (uni == 0x002E
 103                                     || uni == 0x3002
 104                                     || uni == 0xFF0E
 105                                     || uni == 0xFF61
 106                                     || uni == UCS_NO_CHAR)
 107                                         return 0;
 108                         }
 109
 110                         pattern += literal_length;
 111                         hostname += literal_length;
 112                 } else {
 113                         if (hostname == hostname_end)
 114                                 return 0;
 115
 116                         if (c_toupper(*pattern) != c_toupper(*hostname))
 117                                 return 0;
 118
 119                         ++pattern;
 120                         ++hostname;
 121                 }
 122         }
 123
 124         return hostname == hostname_end;
 125 }