Improve support for decryption of full sample encrypted cbcs

1. Allow encryption pattern of 0:0, which is treated as 1:0;
2. Remove the special handling of pattern 1:0 in pattern cryptor
   which may not always be correct;
3. Allow senc/saio/saiz boxes to be absent.

Change-Id: I372e61182ec577107e39cb601c3aed80616b036d

packager/media/base/aes_pattern_cryptor.cc

@@ -23,11 +23,9 @@ AesPatternCryptor::AesPatternCryptor(uint8_t crypt_byte_block,
       skip_byte_block_(skip_byte_block),
       encryption_mode_(encryption_mode),
       cryptor_(std::move(cryptor)) {
-  // |crypt_byte_block_| should never be 0. |skip_byte_block_| can be 0 to allow
+  // Treat pattern 0:0 as 1:0.
-  // a special pattern of 1:0, which is the pattern for the case of pattern
+  if (crypt_byte_block_ == 0 && skip_byte_block_ == 0)
-  // encryption when applied to non video tracks.
+    crypt_byte_block_ = 1;
-  DCHECK_NE(crypt_byte_block_, 0u);
-  DCHECK(skip_byte_block_ != 0 || crypt_byte_block_ == 1);
   DCHECK(cryptor_);
   DCHECK(!cryptor_->use_constant_iv());
 }
@@ -51,17 +49,6 @@ bool AesPatternCryptor::CryptInternal(const uint8_t* text,
   }
   *crypt_text_size = text_size;
 
-  // Handle the special pattern 1:0.
-  if (skip_byte_block_ == 0) {
-    DCHECK_EQ(crypt_byte_block_, 1u);
-    const size_t crypt_byte_size = text_size / AES_BLOCK_SIZE * AES_BLOCK_SIZE;
-    if (!cryptor_->Crypt(text, crypt_byte_size, crypt_text))
-      return false;
-    memcpy(crypt_text + crypt_byte_size, text + crypt_byte_size,
-           text_size - crypt_byte_size);
-    return true;
-  }
-
   while (text_size > 0) {
     const size_t crypt_byte_size = crypt_byte_block_ * AES_BLOCK_SIZE;
     if (NeedEncrypt(text_size, crypt_byte_size)) {

packager/media/base/aes_pattern_cryptor.h

@@ -72,7 +72,7 @@ class AesPatternCryptor : public AesCryptor {
 
   bool NeedEncrypt(size_t input_size, size_t target_data_size);
 
-  const uint8_t crypt_byte_block_;
+  uint8_t crypt_byte_block_;
   const uint8_t skip_byte_block_;
   const PatternEncryptionMode encryption_mode_;
   std::unique_ptr<AesCryptor> cryptor_;

packager/media/base/aes_pattern_cryptor_unittest.cc

@@ -219,35 +219,5 @@ TEST(SampleAesPatternCryptor, MoreThan16Bytes) {
   ASSERT_TRUE(pattern_cryptor.Crypt("0123456789abcdef012", &crypt_text));
 }
 
-TEST(FullSampleSpecialPatternTest, Test) {
-  MockAesCryptor* mock_cryptor = new MockAesCryptor();
-  EXPECT_CALL(*mock_cryptor, CryptInternal(_, 96u, _, _))
-      .WillOnce(Invoke([](const uint8_t* text, size_t text_size,
-                          uint8_t* crypt_text, size_t* crypt_text_size) {
-        *crypt_text_size = text_size;
-        for (size_t i = 0; i < text_size; ++i)
-          *crypt_text++ = 'e';
-        return true;
-      }));
-
-  const uint8_t kFulLSampleCryptBlock = 1;
-  const uint8_t kFullSampleSkipBlock = 0;
-  AesPatternCryptor pattern_cryptor(
-      kFulLSampleCryptBlock, kFullSampleSkipBlock,
-      AesPatternCryptor::kSkipIfCryptByteBlockRemaining,
-      AesPatternCryptor::kUseConstantIv,
-      std::unique_ptr<MockAesCryptor>(mock_cryptor));
-
-  std::vector<uint8_t> iv(8, 'i');
-  // SetIv will be called only once by AesPatternCryptor::SetIv.
-  EXPECT_TRUE(pattern_cryptor.SetIv(iv));
-
-  std::string input_text(100, 'c');
-  std::string crypt_text;
-  // More than 16 bytes so mock's CryptInternal should be called.
-  ASSERT_TRUE(pattern_cryptor.Crypt(input_text, &crypt_text));
-  EXPECT_EQ(std::string(96, 'e') + std::string(4, 'c'), crypt_text);
-}
-
 }  // namespace media
 }  // namespace shaka

packager/media/formats/mp4/track_run_iterator.cc

@@ -589,8 +589,11 @@ const TrackEncryption& TrackRunIterator::track_encryption() const {
 }
 
 std::unique_ptr<DecryptConfig> TrackRunIterator::GetDecryptConfig() {
+  std::vector<uint8_t> iv;
+  std::vector<SubsampleEntry> subsamples;
+
   size_t sample_idx = sample_itr_ - run_itr_->samples.begin();
-  DCHECK_LT(sample_idx, run_itr_->sample_encryption_entries.size());
+  if (sample_idx < run_itr_->sample_encryption_entries.size()) {
     const SampleEncryptionEntry& sample_encryption_entry =
         run_itr_->sample_encryption_entries[sample_idx];
     DCHECK(is_encrypted());
@@ -604,9 +607,12 @@ std::unique_ptr<DecryptConfig> TrackRunIterator::GetDecryptConfig() {
       return std::unique_ptr<DecryptConfig>();
     }
 
+    iv = sample_encryption_entry.initialization_vector;
+    subsamples = sample_encryption_entry.subsamples;
+  }
+
   FourCC protection_scheme = is_audio() ? audio_description().sinf.type.type
                                         : video_description().sinf.type.type;
-  std::vector<uint8_t> iv = sample_encryption_entry.initialization_vector;
   if (iv.empty()) {
     if (protection_scheme != FOURCC_cbcs) {
       LOG(WARNING)
@@ -619,8 +625,8 @@ std::unique_ptr<DecryptConfig> TrackRunIterator::GetDecryptConfig() {
     }
   }
   return std::unique_ptr<DecryptConfig>(new DecryptConfig(
-      track_encryption().default_kid, iv, sample_encryption_entry.subsamples,
+      track_encryption().default_kid, iv, subsamples, protection_scheme,
-      protection_scheme, track_encryption().default_crypt_byte_block,
+      track_encryption().default_crypt_byte_block,
       track_encryption().default_skip_byte_block));
 }