DNSDomainFromDot: Reject empty labels.

net/base/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/base/dns_util.h"
 
 #include <cstring>
 
 namespace net {
 
 // Based on DJB's public domain code.
 bool DNSDomainFromDot(const base::StringPiece& dotted, std::string* out) {
   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)
       break;
     ch = *buf++;
     --n;
     if (ch == '.') {
-      if (labellen) {
-        if (namelen + labellen + 1 > sizeof name)
-          return false;
-        name[namelen++] = static_cast<char>(labellen);
-        memcpy(name + namelen, label, labellen);
-        namelen += labellen;
-        labellen = 0;
-      }
+      // Don't allow empty labels per http://crbug.com/456391.
+      if (!labellen)
+        return false;
+      if (namelen + labellen + 1 > sizeof name)
+        return false;
+      name[namelen++] = static_cast<char>(labellen);
+      memcpy(name + namelen, label, labellen);
+      namelen += labellen;
+      labellen = 0;
       continue;
     }
     if (labellen >= sizeof label)
       return false;
     label[labellen++] = ch;
   }
 
+  // Allow empty label at end of name to disable suffix search.
   if (labellen) {
     if (namelen + labellen + 1 > sizeof name)
       return false;
     name[namelen++] = static_cast<char>(labellen);
     memcpy(name + namelen, label, labellen);
     namelen += labellen;
     labellen = 0;
   }
 
   if (namelen + 1 > sizeof name)
@@ skipping 31 matching lines @@
 std::string TrimEndingDot(const base::StringPiece& host) {
   base::StringPiece host_trimmed = host;
   size_t len = host_trimmed.length();
   if (len > 1 && host_trimmed[len - 1] == '.') {
     host_trimmed.remove_suffix(1);
   }
   return host_trimmed.as_string();
 }
 
 }  // namespace net