Reland of 'Improve canonicalization of mailto url path components'

url/url_canon_mailtourl.cc

 // Copyright 2013 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.
 
 // Functions for canonicalizing "mailto:" URLs.
 
 #include "url/url_canon.h"
 #include "url/url_canon_internal.h"
 #include "url/url_file.h"
 #include "url/url_parse_internal.h"
 
 namespace url {
 
 namespace {
 
+// Certain characters should be percent-encoded when they appear in the path
+// component of a mailto URL, to improve compatibility and mitigate against
+// command-injection attacks on mailto handlers. See https://crbug.com/711020.
+template <typename UCHAR>
+bool ShouldEncodeMailboxCharacter(UCHAR uch) {
+  if (uch < 0x21 ||                              // space & control characters.
+      uch > 0x7e ||                              // high-ascii characters.
+      uch == 0x22 ||                             // quote.
+      uch == 0x3c || uch == 0x3e ||              // angle brackets.
+      uch == 0x60 ||                             // backtick.
+      uch == 0x7b || uch == 0x7c || uch == 0x7d  // braces and pipe.
+      ) {
+    return true;
+  }
+  return false;
+}
+
 template <typename CHAR, typename UCHAR>
 bool DoCanonicalizeMailtoURL(const URLComponentSource<CHAR>& source,
                              const Parsed& parsed,
                              CanonOutput* output,
                              Parsed* new_parsed) {
   // mailto: only uses {scheme, path, query} -- clear the rest.
   new_parsed->username = Component();
   new_parsed->password = Component();
   new_parsed->host = Component();
   new_parsed->port = Component();
   new_parsed->ref = Component();
 
   // Scheme (known, so we don't bother running it through the more
   // complicated scheme canonicalizer).
   new_parsed->scheme.begin = output->length();
   output->Append("mailto:", 7);
   new_parsed->scheme.len = 6;
 
   bool success = true;
 
   // Path
   if (parsed.path.is_valid()) {
     new_parsed->path.begin = output->length();
 
     // Copy the path using path URL's more lax escaping rules.
-    // We convert to UTF-8 and escape non-ASCII, but leave all
+    // We convert to UTF-8 and escape non-ASCII, but leave most
     // ASCII characters alone.
     int end = parsed.path.end();
     for (int i = parsed.path.begin; i < end; ++i) {
       UCHAR uch = static_cast<UCHAR>(source.path[i]);
-      if (uch < 0x20 || uch >= 0x80)
+      if (ShouldEncodeMailboxCharacter<UCHAR>(uch))
         success &= AppendUTF8EscapedChar(source.path, &i, end, output);
       else
         output->push_back(static_cast<char>(uch));
     }
 
     new_parsed->path.len = output->length() - new_parsed->path.begin;
   } else {
     // No path at all
     new_parsed->path.reset();
   }
@@ skipping 44 matching lines @@
                       Parsed* new_parsed) {
   RawCanonOutput<1024> utf8;
   URLComponentSource<char> source(base);
   Parsed parsed(base_parsed);
   SetupUTF16OverrideComponents(base, replacements, &utf8, &source, &parsed);
   return DoCanonicalizeMailtoURL<char, unsigned char>(
       source, parsed, output, new_parsed);
 }
 
 }  // namespace url