Make net::DataURL's MIME string check stricter

net/base/data_url.cc

Index: net/base/data_url.cc
diff --git a/net/base/data_url.cc b/net/base/data_url.cc
index e7b46cd44ceb5bc144d29ffc99fb4489a1a02eaf..07fbd1ebc36e7db2f3362ff7e5daf92c90e33512 100644
--- a/net/base/data_url.cc
+++ b/net/base/data_url.cc
@@ -13,6 +13,7 @@
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
 #include "net/base/escape.h"
+#include "net/http/http_util.h"
 #include "url/gurl.h"
 
 namespace net {
@@ -59,9 +60,18 @@ bool DataURL::Parse(const GURL& url, std::string* mime_type,
     }
   }
 
-  // fallback to defaults if nothing specified in the URL:
-  if (mime_type->empty())
+  if (mime_type->empty()) {
+    // fallback to defaults if nothing specified in the URL:
     mime_type->assign("text/plain");
+  } else {
+    // Check grammar.

[asanka, 2014/03/26 19:42:09]

Consider using IsMimeType() instead?

[tyoshino (SeeGerritForStatus), 2014/03/26 22:07:00]

I considered that. But IsMimeType() doesn't check token grammar, accepts "*" and
is too strict (allow only IANA registered top level types and x- prefixed ones).
So, I refrained from using that.

I checked again why IsMimeType() is designed like this. It was originally part
of web_intents_registry.cc. Where the code which is now in IsMimeType() worked
as a validation for MIME type pattern to be passed to MatchesMimeType().

https://chromiumcodereview.appspot.com/10448109/diff/23003/chrome/browser/int...

As web_intents_registry.cc has gone and the only user of IsMimeType() is
pepper_file_system_browser_host.cc where it's not expected to check pattern
grammar but just MIME grammar, we could just make IsMimeType():
- stop accepting "*"
- separate registered top-level type validation into a separate method
- validate token grammar on type and subtype

Are you fine with this?

[asanka, 2014/03/26 22:29:42]

SGTM

+    std::vector<std::string> mime_type_components;
+    base::SplitString(*mime_type, '/', &mime_type_components);
+    if (mime_type_components.size() != 2 ||
+        !HttpUtil::IsToken(mime_type_components[0]) ||
+        !HttpUtil::IsToken(mime_type_components[1]))
+      return false;
+  }
   if (charset->empty())
     charset->assign("US-ASCII");