Refuse to resolve some types of invalid DNS addresses.

net/dns/dns_util.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/dns/dns_util.h"
 
 #include <errno.h>
 #include <limits.h>
 
 #include <cstring>
@@ skipping 15 matching lines @@
 #endif  // defined(OS_POSIX)
 
 #if defined(OS_ANDROID)
 #include "net/android/network_library.h"
 #endif
 
 namespace net {
 
 // Based on DJB's public domain code.
 bool DNSDomainFromDot(const base::StringPiece& dotted, std::string* out) {
+  // Refuse to convert invalid host names.

[Julia Tuttle, 2016/09/09 20:24:38]

This is commented out; remove it?

[mmenke, 2016/09/09 20:38:44]

Oops, thanks!  I hadn't realized this was actually the method used to check
hostname validity, initially.

+  // if (!IsHostnameValid(dotted))
+  //  return false;
+
   const char* buf = dotted.data();
   unsigned n = dotted.size();
   char label[63];
   size_t labellen = 0; /* <= sizeof label */
   char name[255];
   size_t namelen = 0; /* <= sizeof name */
   char ch;
 
   for (;;) {
     if (!n)
@@ skipping 30 matching lines @@
   if (namelen + 1 > sizeof name)
     return false;
   if (namelen == 0) // Empty names e.g. "", "." are not valid.
     return false;
   name[namelen++] = 0;  // This is the root label (of length 0).
 
   *out = std::string(name, namelen);
   return true;
 }
 
+bool IsValidDNSDomain(const base::StringPiece& dotted) {
+  std::string dns_formatted;
+  return DNSDomainFromDot(dotted, &dns_formatted);
+}
+
 std::string DNSDomainToString(const base::StringPiece& domain) {
   std::string ret;
 
   for (unsigned i = 0; i < domain.size() && domain[i]; i += domain[i] + 1) {
 #if CHAR_MIN < 0
     if (domain[i] < 0)
       return std::string();
 #endif
     if (domain[i] > 63)
       return std::string();
@@ skipping 122 matching lines @@
     return DELTA_IDENTICAL;
   else if (same_size && !any_missing)
     return DELTA_REORDERED;
   else if (any_match)
     return DELTA_OVERLAP;
   else
     return DELTA_DISJOINT;
 }
 
 }  // namespace net