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       if (labellen) {
  28         if (namelen + labellen + 1 > sizeof name)
  29           return false;
  30         name[namelen++] = static_cast<char>(labellen);
  31         memcpy(name + namelen, label, labellen);
  32         namelen += labellen;
  33         labellen = 0;
  34       }
  35       continue;
  36     }
  37     if (labellen >= sizeof label)
  38       return false;
  39     label[labellen++] = ch;
  40   }
  41
  42   if (labellen) {
  43     if (namelen + labellen + 1 > sizeof name)
  44       return false;
  45     name[namelen++] = static_cast<char>(labellen);
  46     memcpy(name + namelen, label, labellen);
  47     namelen += labellen;
  48     labellen = 0;
  49   }
  50
  51   if (namelen + 1 > sizeof name)
  52     return false;
  53   if (namelen == 0) // Empty names e.g. "", "." are not valid.
  54     return false;
  55   name[namelen++] = 0;  // This is the root label (of length 0).
  56
  57   *out = std::string(name, namelen);
  58   return true;
  59 }
  60
  61 std::string DNSDomainToString(const base::StringPiece& domain) {
  62   std::string ret;
  63
  64   for (unsigned i = 0; i < domain.size() && domain[i]; i += domain[i] + 1) {
  65 #if CHAR_MIN < 0
  66     if (domain[i] < 0)
  67       return std::string();
  68 #endif
  69     if (domain[i] > 63)
  70       return std::string();
  71
  72     if (i)
  73       ret += ".";
  74
  75     if (static_cast<unsigned>(domain[i]) + i + 1 > domain.size())
  76       return std::string();
  77
  78     domain.substr(i + 1, domain[i]).AppendToString(&ret);
  79   }
  80   return ret;
  81 }
  82
  83 std::string TrimEndingDot(const base::StringPiece& host) {
  84   base::StringPiece host_trimmed = host;
  85   size_t len = host_trimmed.length();
  86   if (len > 1 && host_trimmed[len - 1] == '.') {
  87     host_trimmed.remove_suffix(1);
  88   }
  89   return host_trimmed.as_string();
  90 }
  91
  92 }  // namespace net