Replace whitespace at beginning and end of file with hyphens, rather than silently discarding.

net/base/net_util.cc

Index: net/base/net_util.cc
===================================================================
--- net/base/net_util.cc	(revision 97172)
+++ net/base/net_util.cc	(working copy)
@@ -158,6 +158,20 @@
   22,   // ssh
 };
 
+template<typename STR>
+typename STR::size_type CountTrailingChars(
+    const STR& input,
+    const typename STR::value_type
+    trailing_chars[]) {
+  const typename STR::size_type last_good_char =
+    input.find_last_not_of(trailing_chars);
+
+  if (last_good_char == std::string::npos)
+    return input.length();
+  else
+    return input.length() - last_good_char - 1;
+}
+
 // Similar to Base64Decode. Decodes a Q-encoded string to a sequence
 // of bytes. If input is invalid, return false.
 bool QPDecode(const std::string& input, std::string* output) {
@@ -1388,6 +1402,7 @@
   static const char* kFinalFallbackName = "download";
 
   std::string filename;
+  std::string::size_type trimmed_trailing_character_count = 0;
 
   // Try to extract from content-disposition first.
   if (!content_disposition.empty())
@@ -1405,10 +1420,12 @@
 
     // Next, remove "." from the beginning and end of the file name to avoid
     // tricks with hidden files, "..", and "."
+    trimmed_trailing_character_count += CountTrailingChars(filename, ".");
     TrimString(filename, ".", &filename);
   }
 
   if (filename.empty()) {
+    trimmed_trailing_character_count = 0;
     // about: and data: URLs don't have file names, but esp. data: URLs may
     // contain parts that look like ones (i.e., contain a slash).
     // Therefore we don't attempt to divine a file name out of them.
@@ -1439,11 +1456,8 @@
 #if defined(OS_WIN)
   { // Handle CreateFile() stripping trailing dots and spaces on filenames
     // http://support.microsoft.com/kb/115827
-    std::string::size_type pos = filename.find_last_not_of(" .");
-    if (pos == std::string::npos)
-      filename.resize(0);
-    else
-      filename.resize(++pos);
+    trimmed_trailing_character_count += CountTrailingChars(filename, " .");
+    filename.resize(filename.length() - trimmed_trailing_character_count);
   }
 #endif
   // Trim '.' once more.
@@ -1452,6 +1466,7 @@
   // If there's no filename or it gets trimed to be empty, use
   // the URL hostname or default_name
   if (filename.empty()) {
+    trimmed_trailing_character_count = 0;
     if (!default_name.empty()) {
       return default_name;
     } else if (url.is_valid()) {
@@ -1466,7 +1481,15 @@
 
 #if defined(OS_WIN)
   string16 path = UTF8ToUTF16(filename);
+  // On Windows we want to preserve or replace all characters including
+  // whitespace to prevent file extension obfuscation on trusted websites
+  // e.g. Gmail might think evil.exe. is safe, so we don't want it to become
+  // evil.exe when we download it
+  trimmed_trailing_character_count += path.length();
+  TrimWhitespace(path, TRIM_TRAILING, &path);
+  trimmed_trailing_character_count -= path.length();
   file_util::ReplaceIllegalCharactersInPath(&path, '-');
+  path.append(trimmed_trailing_character_count, '-');
   return path;
 #else
   std::string path = filename;