[BlobStorage] Enforcing renderer constraints to prevent broken blobs

third_party/WebKit/Source/core/fileapi/File.cpp

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 66 matching lines @@
     const String& path,
     const String& fileSystemName,
     File::ContentTypeLookupPolicy policy) {
   return createBlobDataForFileWithType(
       path, getContentTypeFromFileName(fileSystemName, policy));
 }
 
 static std::unique_ptr<BlobData> createBlobDataForFileWithMetadata(
     const String& fileSystemName,
     const FileMetadata& metadata) {
-  std::unique_ptr<BlobData> blobData = BlobData::create();
+  std::unique_ptr<BlobData> blobData;
+  if (metadata.length == BlobDataItem::toEndOfFile) {

[pwnall, 2017/03/06 21:13:45]

Tests?

[dmurph, 2017/03/06 23:43:29]

Tested by one or more of:
FileTest.fileSystemFileWithNativeSnapshot
V8ScriptValueSerializerTest.RoundTripFileNativeSnapshot
FileListTest.pathsForUserVisibleFiles
WebDragDataTest.items

[pwnall, 2017/03/06 23:45:12]

Do we know for sure that we have coverage of both branches?

[dmurph, 2017/03/29 23:19:24]

Checked. Added one test for case where we have the file length in metadata.

+    blobData = BlobData::createForFileWithUnknownSize(
+        metadata.platformPath, metadata.modificationTime / msPerSecond);
+  } else {
+    blobData = BlobData::create();
+    blobData->appendFile(metadata.platformPath, 0, metadata.length,
+                         metadata.modificationTime / msPerSecond);
+  }
   blobData->setContentType(
       getContentTypeFromFileName(fileSystemName, File::WellKnownContentTypes));
-  blobData->appendFile(metadata.platformPath, 0, metadata.length,
-                       metadata.modificationTime / msPerSecond);
   return blobData;
 }
 
 static std::unique_ptr<BlobData> createBlobDataForFileSystemURL(
     const KURL& fileSystemURL,
     const FileMetadata& metadata) {
-  std::unique_ptr<BlobData> blobData = BlobData::create();
+  std::unique_ptr<BlobData> blobData;
+  if (metadata.length == BlobDataItem::toEndOfFile) {
+    blobData = BlobData::createForFileSystemURLWithUnknownSize(
+        fileSystemURL, metadata.modificationTime / msPerSecond);
+  } else {
+    blobData = BlobData::create();
+    blobData->appendFileSystemURL(fileSystemURL, 0, metadata.length,
+                                  metadata.modificationTime / msPerSecond);
+  }
   blobData->setContentType(getContentTypeFromFileName(
       fileSystemURL.path(), File::WellKnownContentTypes));
-  blobData->appendFileSystemURL(fileSystemURL, 0, metadata.length,
-                                metadata.modificationTime / msPerSecond);
   return blobData;
 }
 
 // static
 File* File::create(
     ExecutionContext* context,
     const HeapVector<ArrayBufferOrArrayBufferViewOrBlobOrUSVString>& fileBits,
     const String& fileName,
     const FilePropertyBag& options,
     ExceptionState& exceptionState) {
@@ skipping 285 matching lines @@
   if (m_fileSystemURL.isEmpty() != other.m_fileSystemURL.isEmpty())
     return false;
 
   if (!m_fileSystemURL.isEmpty())
     return m_fileSystemURL == other.m_fileSystemURL;
 
   return uuid() == other.uuid();
 }
 
 }  // namespace blink