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      1 // Copyright (c) 2010 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef NET_BASE_SSL_FALSE_START_BLACKLIST_H_
      6 #define NET_BASE_SSL_FALSE_START_BLACKLIST_H_
      7 
      8 #include "base/basictypes.h"
      9 
     10 namespace net {
     11 
     12 // SSLFalseStartBlacklist is a set of domains which we believe to be intolerant
     13 // to TLS False Start. Because this set is several hundred long, it's
     14 // precompiled by the code in ssl_false_start_blacklist_process.cc into a hash
     15 // table for fast lookups.
     16 class SSLFalseStartBlacklist {
     17  public:
     18   // IsMember returns true if the given host is in the blacklist.
     19   //   host: a DNS name in dotted form (i.e. "www.example.com")
     20   static bool IsMember(const char* host);
     21 
     22   // Hash returns the modified djb2 hash of the given string.
     23   static unsigned Hash(const char* str) {
     24     // This is inline because the code which generates the hash table needs to
     25     // use it. However, the generating code cannot link against
     26     // ssl_false_start_blacklist.cc because that needs the tables which it
     27     // generates.
     28     const unsigned char* in = reinterpret_cast<const unsigned char*>(str);
     29     unsigned hash = 5381;
     30     unsigned char c;
     31 
     32     while ((c = *in++))
     33       hash = ((hash << 5) + hash) ^ c;
     34     return hash;
     35   }
     36 
     37   // LastTwoLabels returns a pointer within |host| to the last two labels of
     38   // |host|. For example, if |host| is "a.b.c.d" then LastTwoLabels will return
     39   // "c.d".
     40   //   host: a DNS name in dotted form.
     41   //   returns: NULL on error, otherwise a pointer inside |host|.
     42   static const char* LastTwoLabels(const char* host) {
     43     // See comment in |Hash| for why this function is inline.
     44     const size_t len = strlen(host);
     45     if (len == 0)
     46       return NULL;
     47 
     48     unsigned dots_found = 0;
     49     size_t i;
     50     for (i = len - 1; i < len; i--) {
     51       if (host[i] == '.') {
     52         dots_found++;
     53         if (dots_found == 2) {
     54           i++;
     55           break;
     56         }
     57       }
     58     }
     59 
     60     if (i > len)
     61       i = 0;
     62 
     63     if (dots_found == 0)
     64       return NULL;  // no names with less than two labels are in the blacklist.
     65     if (dots_found == 1) {
     66       if (host[0] == '.')
     67         return NULL;  // ditto
     68     }
     69 
     70     return &host[i];
     71   }
     72 
     73   // This is the number of buckets in the blacklist hash table. (Must be a
     74   // power of two).
     75   static const unsigned kBuckets = 128;
     76 
     77  private:
     78   // The following two members are defined in
     79   // ssl_false_start_blacklist_data.cc, which is generated by
     80   // ssl_false_start_blacklist_process.cc
     81 
     82   // kHashTable contains an offset into |kHashData| for each bucket. The
     83   // additional element at the end contains the length of |kHashData|.
     84   static const uint32 kHashTable[kBuckets + 1];
     85   // kHashData contains the contents of the hash table. |kHashTable| indexes
     86   // into this array. Each bucket consists of zero or more, 8-bit length
     87   // prefixed strings. Each string is a DNS name in dotted form. For a given
     88   // string x, x and *.x are considered to be in the blacklist. In order to
     89   // assign a string to a hash bucket, the last two labels (not including the
     90   // root label) are hashed. Thus, the bucket for "www.example.com" is
     91   // Hash("example.com"). No names that are less than two labels long are
     92   // included in the blacklist.
     93   static const char kHashData[];
     94 };
     95 
     96 }  // namespace net
     97 
     98 #endif  // NET_BASE_SSL_FALSE_START_BLACKLIST_H_
     99