Bug 1771423 - Set Content-Type to an empty string for an empty blob with no type. r=kershaw,smaug,necko-reviewers

Set the Content-Type to an empty string for an blob when the type was not
given. Ensure that the channel Content-Type is not overriden in the case
that it was previously set and the blob type is not valid.

Depends on D147568

Differential Revision: https://phabricator.services.mozilla.com/D147481

dom/fetch/FetchDriver.cpp

@@ -1025,13 +1025,13 @@ FetchDriver::OnStartRequest(nsIRequest* aRequest) {
       if (NS_SUCCEEDED(rv) && !contentCharset.IsEmpty()) {
         contentType += ";charset="_ns + contentCharset;
       }
-
-      IgnoredErrorResult result;
-      response->Headers()->Append("Content-Type"_ns, contentType, result);
-      MOZ_ASSERT(!result.Failed());
     }
 
-    if (contentLength > 0) {
+    IgnoredErrorResult result;
+    response->Headers()->Append("Content-Type"_ns, contentType, result);
+    MOZ_ASSERT(!result.Failed());
+
+    if (contentLength >= 0) {
       nsAutoCString contentLenStr;
       contentLenStr.AppendInt(contentLength);
 

dom/file/uri/BlobURLChannel.cpp

@@ -26,6 +26,18 @@ BlobURLChannel::BlobURLChannel(nsIURI* aURI, nsILoadInfo* aLoadInfo)
 
 BlobURLChannel::~BlobURLChannel() = default;
 
+NS_IMETHODIMP
+BlobURLChannel::SetContentType(const nsACString& aContentType) {
+  // If the blob type is empty, set the content type of the channel to the
+  // empty string.
+  if (aContentType.IsEmpty()) {
+    mContentType.Truncate();
+    return NS_OK;
+  }
+
+  return nsBaseChannel::SetContentType(aContentType);
+}
+
 nsresult BlobURLChannel::OpenContentStream(bool aAsync,
                                            nsIInputStream** aResult,
                                            nsIChannel** aChannel) {

dom/file/uri/BlobURLChannel.h

@@ -21,6 +21,8 @@ class BlobURLChannel final : public nsBaseChannel {
  public:
   BlobURLChannel(nsIURI* aURI, nsILoadInfo* aLoadInfo);
 
+  NS_IMETHOD SetContentType(const nsACString& aContentType) override;
+
  private:
   ~BlobURLChannel() override;
 

dom/file/uri/BlobURLInputStream.cpp

@@ -13,6 +13,7 @@
 #include "mozilla/dom/ContentChild.h"
 #include "mozilla/dom/IPCBlobUtils.h"
 #include "nsStreamUtils.h"
+#include "nsMimeTypes.h"
 
 namespace mozilla::dom {
 
@@ -461,9 +462,21 @@ nsresult BlobURLInputStream::StoreBlobImplStream(
     already_AddRefed<BlobImpl> aBlobImpl, const MutexAutoLock& aProofOfLock) {
   MOZ_ASSERT(NS_IsMainThread(), "Only call on main thread");
   const RefPtr<BlobImpl> blobImpl = aBlobImpl;
-  nsAutoString contentType;
-  blobImpl->GetType(contentType);
-  mChannel->SetContentType(NS_ConvertUTF16toUTF8(contentType));
+  nsAutoString blobContentType;
+  nsAutoCString channelContentType;
+
+  blobImpl->GetType(blobContentType);
+  mChannel->GetContentType(channelContentType);
+  // A empty content type is the correct channel content type in the case of a
+  // fetch of a blob where the type was not set. It is invalid in others cases
+  // such as a XHR (See https://xhr.spec.whatwg.org/#response-mime-type). The
+  // XMLHttpRequestMainThread will set the channel content type to the correct
+  // fallback value before this point, so we need to be careful to only override
+  // it when the blob type is valid.
+  if (!blobContentType.IsEmpty() ||
+      channelContentType.EqualsLiteral(UNKNOWN_CONTENT_TYPE)) {
+    mChannel->SetContentType(NS_ConvertUTF16toUTF8(blobContentType));
+  }
 
   auto cleanupOnExit = MakeScopeExit([&] { mChannel = nullptr; });
 

dom/xhr/XMLHttpRequestMainThread.cpp

@@ -1888,7 +1888,7 @@ XMLHttpRequestMainThread::OnStartRequest(nsIRequest* request) {
   // Fallback to 'application/octet-stream'
   nsAutoCString type;
   channel->GetContentType(type);
-  if (type.EqualsLiteral(UNKNOWN_CONTENT_TYPE)) {
+  if (type.IsEmpty() || type.EqualsLiteral(UNKNOWN_CONTENT_TYPE)) {
     channel->SetContentType(nsLiteralCString(APPLICATION_OCTET_STREAM));
   }
 

netwerk/base/nsBaseChannel.h

@@ -292,8 +292,6 @@ class nsBaseChannel
   nsCOMPtr<nsISupports> mOwner;
   nsCOMPtr<nsISupports> mSecurityInfo;
   nsCOMPtr<nsIChannel> mRedirectChannel;
-  nsCString mContentType;
-  nsCString mContentCharset;
   uint32_t mLoadFlags{LOAD_NORMAL};
   bool mQueriedProgressSink{true};
   bool mSynthProgressEvents{false};
@@ -303,6 +301,8 @@ class nsBaseChannel
   uint32_t mRedirectFlags{0};
 
  protected:
+  nsCString mContentType;
+  nsCString mContentCharset;
   nsCOMPtr<nsIURI> mURI;
   nsCOMPtr<nsILoadGroup> mLoadGroup;
   nsCOMPtr<nsILoadInfo> mLoadInfo;

netwerk/ipc/DocumentLoadListener.cpp

@@ -246,7 +246,8 @@ class ParentProcessDocumentOpenInfo final : public nsDocumentOpenInfo,
     // The one exception is nsUnknownDecoder, which works in the parent
     // (and we need to know what the content type is before we can
     // decide if it will be handled in the parent), so we run that here.
-    if (mContentType.LowerCaseEqualsASCII(UNKNOWN_CONTENT_TYPE)) {
+    if (mContentType.LowerCaseEqualsASCII(UNKNOWN_CONTENT_TYPE) ||
+        mContentType.IsEmpty()) {
       return nsDocumentOpenInfo::TryStreamConversion(aChannel);
     }
 

netwerk/protocol/viewsource/nsViewSourceChannel.cpp

@@ -457,7 +457,8 @@ nsViewSourceChannel::GetContentType(nsACString& aContentType) {
     // content decoder will then kick in automatically, and it
     // will call our SetOriginalContentType method instead of our
     // SetContentType method to set the type it determines.
-    if (!contentType.EqualsLiteral(UNKNOWN_CONTENT_TYPE)) {
+    if (!contentType.EqualsLiteral(UNKNOWN_CONTENT_TYPE) &&
+        !contentType.IsEmpty()) {
       contentType = VIEWSOURCE_CONTENT_TYPE;
     }
 

uriloader/base/nsURILoader.cpp

@@ -568,7 +568,15 @@ nsresult nsDocumentOpenInfo::ConvertData(nsIRequest* request,
 
 nsresult nsDocumentOpenInfo::TryStreamConversion(nsIChannel* aChannel) {
   constexpr auto anyType = "*/*"_ns;
-  nsresult rv = ConvertData(aChannel, m_contentListener, mContentType, anyType);
+
+  // A empty content type should be treated like the unknown content type.
+  nsCString srcContentType(mContentType);
+  if (srcContentType.IsEmpty()) {
+    srcContentType.AssignLiteral(UNKNOWN_CONTENT_TYPE);
+  }
+
+  nsresult rv =
+      ConvertData(aChannel, m_contentListener, srcContentType, anyType);
   if (NS_FAILED(rv)) {
     m_targetStreamListener = nullptr;
   } else if (m_targetStreamListener) {