net/base/dns_util.cc

   1 // Copyright (c) 2011 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 #include "net/base/dns_util.h"
   6
   7 #include <cstring>
   8
   9 namespace net {
  10
  11 // Based on DJB's public domain code.
  12 bool DNSDomainFromDot(const base::StringPiece& dotted, std::string* out) {
  13   const char* buf = dotted.data();
  14   unsigned n = dotted.size();
  15   char label[63];
  16   size_t labellen = 0; /* <= sizeof label */
  17   char name[255];
  18   size_t namelen = 0; /* <= sizeof name */
  19   char ch;
  20
  21   for (;;) {
  22     if (!n)
  23       break;
  24     ch = *buf++;
  25     --n;
  26     if (ch == '.') {
  27       // Don't allow empty labels per http://crbug.com/456391.
  28       if (!labellen)
  29         return false;
  30       if (namelen + labellen + 1 > sizeof name)
  31         return false;
  32       name[namelen++] = static_cast<char>(labellen);
  33       memcpy(name + namelen, label, labellen);
  34       namelen += labellen;
  35       labellen = 0;
  36       continue;
  37     }
  38     if (labellen >= sizeof label)
  39       return false;
  40     label[labellen++] = ch;
  41   }
  42
  43   // Allow empty label at end of name to disable suffix search.
  44   if (labellen) {
  45     if (namelen + labellen + 1 > sizeof name)
  46       return false;
  47     name[namelen++] = static_cast<char>(labellen);
  48     memcpy(name + namelen, label, labellen);
  49     namelen += labellen;
  50     labellen = 0;
  51   }
  52
  53   if (namelen + 1 > sizeof name)
  54     return false;
  55   if (namelen == 0) // Empty names e.g. "", "." are not valid.
  56     return false;
  57   name[namelen++] = 0;  // This is the root label (of length 0).
  58
  59   *out = std::string(name, namelen);
  60   return true;
  61 }
  62
  63 std::string DNSDomainToString(const base::StringPiece& domain) {
  64   std::string ret;
  65
  66   for (unsigned i = 0; i < domain.size() && domain[i]; i += domain[i] + 1) {
  67 #if CHAR_MIN < 0
  68     if (domain[i] < 0)
  69       return std::string();
  70 #endif
  71     if (domain[i] > 63)
  72       return std::string();
  73
  74     if (i)
  75       ret += ".";
  76
  77     if (static_cast<unsigned>(domain[i]) + i + 1 > domain.size())
  78       return std::string();
  79
  80     domain.substr(i + 1, domain[i]).AppendToString(&ret);
  81   }
  82   return ret;
  83 }
  84
  85 std::string TrimEndingDot(const base::StringPiece& host) {
  86   base::StringPiece host_trimmed = host;
  87   size_t len = host_trimmed.length();
  88   if (len > 1 && host_trimmed[len - 1] == '.') {
  89     host_trimmed.remove_suffix(1);
  90   }
  91   return host_trimmed.as_string();
  92 }
  93
  94 }  // namespace net