tor-browser

commit 5536bc805c2cb95644f15e828c0ae18fd70e9408
parent 39d07234cfea49c813053b01908d35626d75f1c5
Author: alwu <alwu@mozilla.com>
Date:   Thu, 16 Oct 2025 19:00:37 +0000

Bug 1994550 - part1 : set CBCS related encryption information properly. r=jolin

For CBCS, the value of the crypto byte block and the skip byte block are
crucial, and it is also common to see the use of a constant IV for CBCS
for simplicity. This patch sets those attributes properly for the Media
Foundation Media Engine.

Differential Revision: https://phabricator.services.mozilla.com/D268803

Diffstat:
M
dom/media/ipc/PMediaDecoderParams.ipdlh
 | 
3
+++
M
dom/media/ipc/RemoteMediaData.cpp
 | 
6
++++++
M
dom/media/platforms/wmf/MFMediaEngineStream.cpp
 | 
38
++++++++++++++++++++++++++++++++------

3 files changed, 41 insertions(+), 6 deletions(-)
diff --git a/dom/media/ipc/PMediaDecoderParams.ipdlh b/dom/media/ipc/PMediaDecoderParams.ipdlh
@@ -22,9 +22,12 @@ struct MediaDataIPDL
 struct CryptoInfo {
   CryptoScheme mEncryptionScheme;
   uint8_t[] mIV;
+  uint8_t[] mConstantIV;
   uint8_t[] mKeyId;
   uint32_t[] mClearBytes;
   uint32_t[] mCipherBytes;
+  uint8_t mCryptByteBlock;
+  uint8_t mSkipByteBlock;
 };
 
 } // namespace mozilla
diff --git a/dom/media/ipc/RemoteMediaData.cpp b/dom/media/ipc/RemoteMediaData.cpp
@@ -154,9 +154,12 @@ bool ArrayOfRemoteMediaRawData::Fill(
             ? Some(CryptoInfo{
                   entry->mCrypto.mCryptoScheme,
                   entry->mCrypto.mIV,
+                  entry->mCrypto.mConstantIV,
                   entry->mCrypto.mKeyId,
                   entry->mCrypto.mPlainSizes,
                   entry->mCrypto.mEncryptedSizes,
+                  entry->mCrypto.mCryptByteBlock,
+                  entry->mCrypto.mSkipByteBlock,
               })
             : Nothing()});
   }
@@ -219,10 +222,13 @@ already_AddRefed<MediaRawData> ArrayOfRemoteMediaRawData::ElementAt(
     CryptoSample& cypto = rawData->GetWritableCrypto();
     cypto.mCryptoScheme = sample.mCryptoConfig->mEncryptionScheme();
     cypto.mIV = std::move(sample.mCryptoConfig->mIV());
+    cypto.mConstantIV = std::move(sample.mCryptoConfig->mConstantIV());
     cypto.mIVSize = cypto.mIV.Length();
     cypto.mKeyId = std::move(sample.mCryptoConfig->mKeyId());
     cypto.mPlainSizes = std::move(sample.mCryptoConfig->mClearBytes());
     cypto.mEncryptedSizes = std::move(sample.mCryptoConfig->mCipherBytes());
+    cypto.mCryptByteBlock = sample.mCryptoConfig->mCryptByteBlock();
+    cypto.mSkipByteBlock = sample.mCryptoConfig->mSkipByteBlock();
   }
   perfRecorder.Record();
   return rawData.forget();
diff --git a/dom/media/platforms/wmf/MFMediaEngineStream.cpp b/dom/media/platforms/wmf/MFMediaEngineStream.cpp
@@ -366,10 +366,10 @@ HRESULT MFMediaEngineStream::CreateInputSample(IMFSample** aSample) {
   MOZ_ASSERT(mRawDataQueueForFeedingEngine.GetSize() != 0);
   RefPtr<MediaRawData> data = mRawDataQueueForFeedingEngine.PopFront();
   SLOGV("CreateInputSample, pop data [%" PRId64 ", %" PRId64
-        "] (duration=%" PRId64 ", kf=%d), queue size=%zu",
+        "] (duration=%" PRId64 ", kf=%d, encrypted=%d), queue size=%zu",
         data->mTime.ToMicroseconds(), data->GetEndTime().ToMicroseconds(),
         data->mDuration.ToMicroseconds(), data->mKeyframe,
-        mRawDataQueueForFeedingEngine.GetSize());
+        data->mCrypto.IsEncrypted(), mRawDataQueueForFeedingEngine.GetSize());
   PROFILER_MARKER(
       nsPrintfCString(
           "pop %s (stream=%" PRIu64 ")",
@@ -414,12 +414,26 @@ HRESULT MFMediaEngineStream::AddEncryptAttributes(
   // Scheme
   MFSampleEncryptionProtectionScheme protectionScheme;
   if (aCryptoConfig.mCryptoScheme == CryptoScheme::Cenc) {
+    SLOG("Set CENC encryption");
     protectionScheme = MFSampleEncryptionProtectionScheme::
         MF_SAMPLE_ENCRYPTION_PROTECTION_SCHEME_AES_CTR;
   } else if (aCryptoConfig.mCryptoScheme == CryptoScheme::Cbcs ||
              aCryptoConfig.mCryptoScheme == CryptoScheme::Cbcs_1_9) {
     protectionScheme = MFSampleEncryptionProtectionScheme::
         MF_SAMPLE_ENCRYPTION_PROTECTION_SCHEME_AES_CBC;
+    SLOG("Set CBC pattern encryption, crypt=%u, skip=%u",
+         aCryptoConfig.mCryptByteBlock, aCryptoConfig.mSkipByteBlock);
+    // Only need to set them when they are non-zero. See
+    // https://learn.microsoft.com/en-us/windows/win32/medfound/mfsampleextension-encryption-cryptbyteblock
+    // https://learn.microsoft.com/en-us/windows/win32/medfound/mfsampleextension-encryption-skipbyteblock
+    if (aCryptoConfig.mCryptByteBlock > 0 && aCryptoConfig.mSkipByteBlock > 0) {
+      RETURN_IF_FAILED(
+          aSample->SetUINT32(MFSampleExtension_Encryption_CryptByteBlock,
+                             aCryptoConfig.mCryptByteBlock));
+      RETURN_IF_FAILED(
+          aSample->SetUINT32(MFSampleExtension_Encryption_SkipByteBlock,
+                             aCryptoConfig.mSkipByteBlock));
+    }
   } else {
     SLOG("Unexpected encryption scheme");
     return MF_E_UNEXPECTED;
@@ -439,10 +453,22 @@ HRESULT MFMediaEngineStream::AddEncryptAttributes(
   // to store last key id and set it in CDM to refresh the decryptor.
 
   // IV
-  RETURN_IF_FAILED(aSample->SetBlob(
-      MFSampleExtension_Encryption_SampleID,
-      reinterpret_cast<const uint8_t*>(aCryptoConfig.mIV.Elements()),
-      aCryptoConfig.mIVSize));
+  if (aCryptoConfig.mIVSize != 0) {
+    // Per-sample IV, usually seen in CENC.
+    SLOG("Use sample IV for decryption, IV size=%u", aCryptoConfig.mIVSize);
+    RETURN_IF_FAILED(aSample->SetBlob(
+        MFSampleExtension_Encryption_SampleID,
+        reinterpret_cast<const uint8_t*>(aCryptoConfig.mIV.Elements()),
+        aCryptoConfig.mIVSize));
+  } else {
+    // A constant IV for all samples, usually seen in CBCS.
+    SLOG("Use constant IV for decryption, constantIV length=%zu",
+         aCryptoConfig.mConstantIV.Length());
+    RETURN_IF_FAILED(aSample->SetBlob(
+        MFSampleExtension_Encryption_SampleID,
+        reinterpret_cast<const uint8_t*>(aCryptoConfig.mConstantIV.Elements()),
+        aCryptoConfig.mConstantIV.Length()));
+  }
 
   // Subsample entries.
   MOZ_ASSERT(aCryptoConfig.mEncryptedSizes.Length() ==