Implemented AES-CBC with Ciphertext Stealing for WVM decryption.

Change-Id: I4a1ba4247bb6f055905663568699b06d7c18a968

media/base/aes_encryptor.cc

@@ -143,10 +143,10 @@ bool AesCtrEncryptor::SetIv(const std::vector<uint8>& iv) {
   return true;
 }
 
-AesCbcEncryptor::AesCbcEncryptor() {}
+AesCbcPkcs5Encryptor::AesCbcPkcs5Encryptor() {}
-AesCbcEncryptor::~AesCbcEncryptor() {}
+AesCbcPkcs5Encryptor::~AesCbcPkcs5Encryptor() {}
 
-bool AesCbcEncryptor::InitializeWithIv(const std::vector<uint8>& key,
+bool AesCbcPkcs5Encryptor::InitializeWithIv(const std::vector<uint8>& key,
                                             const std::vector<uint8>& iv) {
   if (!IsKeySizeValidForAes(key.size())) {
     LOG(ERROR) << "Invalid AES key size: " << key.size();
@@ -164,7 +164,7 @@ bool AesCbcEncryptor::InitializeWithIv(const std::vector<uint8>& key,
   return true;
 }
 
-void AesCbcEncryptor::Encrypt(const std::string& plaintext,
+void AesCbcPkcs5Encryptor::Encrypt(const std::string& plaintext,
                                    std::string* ciphertext) {
   DCHECK(ciphertext);
   DCHECK(encrypt_key_);
@@ -185,7 +185,7 @@ void AesCbcEncryptor::Encrypt(const std::string& plaintext,
                   AES_ENCRYPT);
 }
 
-bool AesCbcEncryptor::SetIv(const std::vector<uint8>& iv) {
+bool AesCbcPkcs5Encryptor::SetIv(const std::vector<uint8>& iv) {
   if (iv.size() != AES_BLOCK_SIZE) {
     LOG(ERROR) << "Invalid IV size: " << iv.size();
     return false;
@@ -195,10 +195,10 @@ bool AesCbcEncryptor::SetIv(const std::vector<uint8>& iv) {
   return true;
 }
 
-AesCbcDecryptor::AesCbcDecryptor() {}
+AesCbcPkcs5Decryptor::AesCbcPkcs5Decryptor() {}
-AesCbcDecryptor::~AesCbcDecryptor() {}
+AesCbcPkcs5Decryptor::~AesCbcPkcs5Decryptor() {}
 
-bool AesCbcDecryptor::InitializeWithIv(const std::vector<uint8>& key,
+bool AesCbcPkcs5Decryptor::InitializeWithIv(const std::vector<uint8>& key,
                                             const std::vector<uint8>& iv) {
   if (!IsKeySizeValidForAes(key.size())) {
     LOG(ERROR) << "Invalid AES key size: " << key.size();
@@ -216,7 +216,7 @@ bool AesCbcDecryptor::InitializeWithIv(const std::vector<uint8>& key,
   return true;
 }
 
-bool AesCbcDecryptor::Decrypt(const std::string& ciphertext,
+bool AesCbcPkcs5Decryptor::Decrypt(const std::string& ciphertext,
                                    std::string* plaintext) {
   if ((ciphertext.size() % AES_BLOCK_SIZE) != 0) {
     LOG(ERROR) << "Expecting cipher text size to be multiple of "
@@ -246,7 +246,226 @@ bool AesCbcDecryptor::Decrypt(const std::string& ciphertext,
   return true;
 }
 
-bool AesCbcDecryptor::SetIv(const std::vector<uint8>& iv) {
+bool AesCbcPkcs5Decryptor::SetIv(const std::vector<uint8>& iv) {
+  if (iv.size() != AES_BLOCK_SIZE) {
+    LOG(ERROR) << "Invalid IV size: " << iv.size();
+    return false;
+  }
+
+  iv_ = iv;
+  return true;
+}
+
+AesCbcCtsEncryptor::AesCbcCtsEncryptor() {}
+AesCbcCtsEncryptor::~AesCbcCtsEncryptor() {}
+
+bool AesCbcCtsEncryptor::InitializeWithIv(const std::vector<uint8>& key,
+                                          const std::vector<uint8>& iv) {
+  if (!IsKeySizeValidForAes(key.size())) {
+    LOG(ERROR) << "Invalid AES key size: " << key.size();
+    return false;
+  }
+  if (iv.size() != AES_BLOCK_SIZE) {
+    LOG(ERROR) << "Invalid IV size: " << iv.size();
+    return false;
+  }
+
+  encrypt_key_.reset(new AES_KEY());
+  CHECK_EQ(AES_set_encrypt_key(&key[0], key.size() * 8, encrypt_key_.get()), 0);
+
+  iv_ = iv;
+  return true;
+}
+
+void AesCbcCtsEncryptor::Encrypt(const uint8* plaintext,
+                                 size_t size,
+                                 uint8* ciphertext) {
+  DCHECK(plaintext);
+  DCHECK(ciphertext);
+
+  if (size < AES_BLOCK_SIZE) {
+    // Don't have a full block, leave unencrypted.
+    memcpy(ciphertext, plaintext, size);
+    return;
+  }
+
+  std::vector<uint8> iv(iv_);
+  size_t residual_block_size = size % AES_BLOCK_SIZE;
+  size_t cbc_size = size - residual_block_size;
+
+  // Encrypt everything but the residual block using CBC.
+  AES_cbc_encrypt(plaintext,
+                  ciphertext,
+                  cbc_size,
+                  encrypt_key_.get(),
+                  &iv[0],
+                  AES_ENCRYPT);
+  if (residual_block_size == 0) {
+    // No residual block. No need to do ciphertext stealing.
+    return;
+  }
+
+  // Zero-pad the residual block and encrypt using CBC.
+  std::vector<uint8> residual_block(plaintext + size - residual_block_size,
+                                    plaintext + size);
+  residual_block.resize(AES_BLOCK_SIZE, 0);
+  AES_cbc_encrypt(&residual_block[0],
+                  &residual_block[0],
+                  AES_BLOCK_SIZE,
+                  encrypt_key_.get(),
+                  &iv[0],
+                  AES_ENCRYPT);
+
+  // Replace the last full block with the zero-padded, encrypted residual block,
+  // and replace the residual block with the equivalent portion of the last full
+  // encrypted block. It may appear that some encrypted bits of the last full
+  // block are lost, but they are not, as they were used as the IV when
+  // encrypting the zero-padded residual block.
+  uint8* residual_ciphertext_block = ciphertext + size - residual_block_size;
+  memcpy(residual_ciphertext_block,
+         residual_ciphertext_block - AES_BLOCK_SIZE,
+         residual_block_size);
+  memcpy(residual_ciphertext_block - AES_BLOCK_SIZE,
+         residual_block.data(),
+         AES_BLOCK_SIZE);
+}
+
+void AesCbcCtsEncryptor::Encrypt(const std::vector<uint8>& plaintext,
+                                 std::vector<uint8>* ciphertext) {
+  DCHECK(ciphertext);
+
+  ciphertext->resize(plaintext.size(), 0);
+  if (plaintext.empty())
+    return;
+
+  return Encrypt(plaintext.data(), plaintext.size(), &(*ciphertext)[0]);
+}
+
+bool AesCbcCtsEncryptor::SetIv(const std::vector<uint8>& iv) {
+  if (iv.size() != AES_BLOCK_SIZE) {
+    LOG(ERROR) << "Invalid IV size: " << iv.size();
+    return false;
+  }
+
+  iv_ = iv;
+  return true;
+}
+
+AesCbcCtsDecryptor::AesCbcCtsDecryptor() {}
+AesCbcCtsDecryptor::~AesCbcCtsDecryptor() {}
+
+bool AesCbcCtsDecryptor::InitializeWithIv(const std::vector<uint8>& key,
+                                          const std::vector<uint8>& iv) {
+  if (!IsKeySizeValidForAes(key.size())) {
+    LOG(ERROR) << "Invalid AES key size: " << key.size();
+    return false;
+  }
+  if (iv.size() != AES_BLOCK_SIZE) {
+    LOG(ERROR) << "Invalid IV size: " << iv.size();
+    return false;
+  }
+
+  decrypt_key_.reset(new AES_KEY());
+  CHECK_EQ(AES_set_decrypt_key(&key[0], key.size() * 8, decrypt_key_.get()), 0);
+
+  iv_ = iv;
+  return true;
+}
+
+void AesCbcCtsDecryptor::Decrypt(const uint8* ciphertext,
+                                 size_t size,
+                                 uint8* plaintext) {
+  DCHECK(ciphertext);
+  DCHECK(plaintext);
+
+  if (size < AES_BLOCK_SIZE) {
+    // Don't have a full block, leave unencrypted.
+    memcpy(plaintext, ciphertext, size);
+    return;
+  }
+
+  std::vector<uint8> iv(iv_);
+  size_t residual_block_size = size % AES_BLOCK_SIZE;
+
+  if (residual_block_size == 0) {
+    // No residual block. No need to do ciphertext stealing.
+    AES_cbc_encrypt(ciphertext,
+                    plaintext,
+                    size,
+                    decrypt_key_.get(),
+                    &iv[0],
+                    AES_DECRYPT);
+    return;
+  }
+
+  // AES-CBC decrypt everything up to the next-to-last full block.
+  size_t cbc_size = size - residual_block_size;
+  if (cbc_size > AES_BLOCK_SIZE) {
+    AES_cbc_encrypt(ciphertext,
+                    plaintext,
+                    cbc_size - AES_BLOCK_SIZE,
+                    decrypt_key_.get(),
+                    &iv[0],
+                    AES_DECRYPT);
+  }
+
+  // Determine what the last IV should be so that we can "skip ahead" in the
+  // CBC decryption.
+  std::vector<uint8> last_iv(ciphertext + size - residual_block_size,
+                             ciphertext + size);
+  last_iv.resize(AES_BLOCK_SIZE, 0);
+
+  // Decrypt the next-to-last block using the IV determined above. This decrypts
+  // the residual block bits.
+  AES_cbc_encrypt(ciphertext + size - residual_block_size - AES_BLOCK_SIZE,
+                  plaintext + size - residual_block_size - AES_BLOCK_SIZE,
+                  AES_BLOCK_SIZE,
+                  decrypt_key_.get(),
+                  &last_iv[0],
+                  AES_DECRYPT);
+
+  // Swap back the residual block bits and the next-to-last full block.
+  if (plaintext == ciphertext) {
+    uint8* ptr1 = plaintext + size - residual_block_size;
+    uint8* ptr2 = plaintext + size - residual_block_size - AES_BLOCK_SIZE;
+    for (size_t i = 0; i < residual_block_size; ++i) {
+      uint8 temp = *ptr1;
+      *ptr1 = *ptr2;
+      *ptr2 = temp;
+      ++ptr1;
+      ++ptr2;
+    }
+  } else {
+    uint8* residual_plaintext_block = plaintext + size - residual_block_size;
+    memcpy(residual_plaintext_block,
+           residual_plaintext_block - AES_BLOCK_SIZE,
+           residual_block_size);
+    memcpy(residual_plaintext_block - AES_BLOCK_SIZE,
+           ciphertext + size - residual_block_size,
+           residual_block_size);
+  }
+
+  // Decrypt the last full block.
+  AES_cbc_encrypt(plaintext + size - residual_block_size - AES_BLOCK_SIZE,
+                  plaintext + size - residual_block_size - AES_BLOCK_SIZE,
+                  AES_BLOCK_SIZE,
+                  decrypt_key_.get(),
+                  &iv[0],
+                  AES_DECRYPT);
+}
+
+void AesCbcCtsDecryptor::Decrypt(const std::vector<uint8>& ciphertext,
+                                 std::vector<uint8>* plaintext) {
+  DCHECK(plaintext);
+
+  plaintext->resize(ciphertext.size(), 0);
+  if (ciphertext.empty())
+    return;
+
+  return Decrypt(ciphertext.data(), ciphertext.size(), &(*plaintext)[0]);
+}
+
+bool AesCbcCtsDecryptor::SetIv(const std::vector<uint8>& iv) {
   if (iv.size() != AES_BLOCK_SIZE) {
     LOG(ERROR) << "Invalid IV size: " << iv.size();
     return false;

media/base/aes_encryptor.h

@@ -21,6 +21,7 @@ typedef struct aes_key_st AES_KEY;
 namespace edash_packager {
 namespace media {
 
+// Class which implements AES-CTR counter-mode encryption/decryption.
 class AesCtrEncryptor {
  public:
   AesCtrEncryptor();
@@ -109,10 +110,12 @@ class AesCtrEncryptor {
   DISALLOW_COPY_AND_ASSIGN(AesCtrEncryptor);
 };
 
-class AesCbcEncryptor {
+// Class which implements AES-CBC (Cipher block chaining) encryption with
+// PKCS#5 padding.
+class AesCbcPkcs5Encryptor {
  public:
-  AesCbcEncryptor();
+  AesCbcPkcs5Encryptor();
-  ~AesCbcEncryptor();
+  ~AesCbcPkcs5Encryptor();
 
   /// Initialize the encryptor with specified key and IV.
   /// @param key should be 128 bits or 192 bits or 256 bits in size as defined
@@ -135,13 +138,15 @@ class AesCbcEncryptor {
   std::vector<uint8> iv_;
   scoped_ptr<AES_KEY> encrypt_key_;
 
-  DISALLOW_COPY_AND_ASSIGN(AesCbcEncryptor);
+  DISALLOW_COPY_AND_ASSIGN(AesCbcPkcs5Encryptor);
 };
 
-class AesCbcDecryptor {
+// Class which implements AES-CBC (Cipher block chaining) decryption with
+// PKCS#5 padding.
+class AesCbcPkcs5Decryptor {
  public:
-  AesCbcDecryptor();
+  AesCbcPkcs5Decryptor();
-  ~AesCbcDecryptor();
+  ~AesCbcPkcs5Decryptor();
 
   /// Initialize the decryptor with specified key and IV.
   /// @param key should be 128 bits or 192 bits or 256 bits in size as defined
@@ -165,7 +170,92 @@ class AesCbcDecryptor {
   std::vector<uint8> iv_;
   scoped_ptr<AES_KEY> decrypt_key_;
 
-  DISALLOW_COPY_AND_ASSIGN(AesCbcDecryptor);
+  DISALLOW_COPY_AND_ASSIGN(AesCbcPkcs5Decryptor);
+};
+
+// Class which implements AES-CBC (Cipher block chaining) encryption with
+// Ciphertext stealing.
+class AesCbcCtsEncryptor {
+ public:
+  AesCbcCtsEncryptor();
+  ~AesCbcCtsEncryptor();
+
+  /// Initialize the encryptor with specified key and IV.
+  /// @param key should be 128 bits or 192 bits or 256 bits in size as defined
+  ///        in AES spec.
+  /// @param iv should be 16 bytes in size.
+  /// @return true on successful initialization, false otherwise.
+  bool InitializeWithIv(const std::vector<uint8>& key,
+                        const std::vector<uint8>& iv);
+
+  /// @param plaintext points to the data to be encrypted.
+  /// @param size is the number of bytes to be encrypted. If less than 16
+  ///        bytes, it will be copied in the clear.
+  /// @param ciphertext should not be NULL. The buffer should be at least
+  ///        @a size bytes in length.
+  void Encrypt(const uint8* plaintext,
+               size_t size,
+               uint8* ciphertext);
+
+  /// @param plaintext contains the data to be encrypted. If less than 16
+  ///        bytes in size, it will be copied in the clear.
+  /// @param ciphertext should not be NULL. Caller retains ownership.
+  void Encrypt(const std::vector<uint8>& plaintext,
+               std::vector<uint8>* ciphertext);
+
+  /// @param iv is the initialization vector. Should be 16 bytes in size.
+  /// @return true if successful, false if the input is invalid.
+  bool SetIv(const std::vector<uint8>& iv);
+
+  const std::vector<uint8>& iv() const { return iv_; }
+
+ private:
+  std::vector<uint8> iv_;
+  scoped_ptr<AES_KEY> encrypt_key_;
+
+  DISALLOW_COPY_AND_ASSIGN(AesCbcCtsEncryptor);
+};
+
+// Class which implements AES-CBC (Cipher block chaining) decryption with
+// Ciphertext stealing.
+class AesCbcCtsDecryptor {
+ public:
+  AesCbcCtsDecryptor();
+  ~AesCbcCtsDecryptor();
+
+  /// Initialize the decryptor with specified key and IV.
+  /// @param key should be 128 bits or 192 bits or 256 bits in size as defined
+  ///        in AES spec.
+  /// @param iv should be 16 bytes in size.
+  /// @return true on successful initialization, false otherwise.
+  bool InitializeWithIv(const std::vector<uint8>& key,
+                        const std::vector<uint8>& iv);
+
+  /// @param ciphertext points to the data to be decrypted.
+  /// @param size is the number of bytes to be decrypted. If less than 16
+  ///        bytes, it will be copied in the clear.
+  /// @param plaintext should not be NULL. The buffer should be at least
+  ///        @a size bytes in length.
+  void Decrypt(const uint8* ciphertext,
+               size_t size,
+               uint8* plaintext);
+
+  /// @param ciphertext contains the data to be decrypted. If less than 16
+  ///        bytes in size, it will be copied in the clear.
+  /// @param plaintext should not be NULL. Caller retains ownership.
+  void Decrypt(const std::vector<uint8>& ciphertext,
+               std::vector<uint8>* plaintext);
+
+  /// @return true if successful, false if the input is invalid.
+  bool SetIv(const std::vector<uint8>& iv);
+
+  const std::vector<uint8>& iv() const { return iv_; }
+
+ private:
+  std::vector<uint8> iv_;
+  scoped_ptr<AES_KEY> decrypt_key_;
+
+  DISALLOW_COPY_AND_ASSIGN(AesCbcCtsDecryptor);
 };
 
 }  // namespace media

media/base/aes_encryptor_unittest.cc

@@ -17,10 +17,10 @@ const uint32 kAesBlockSize = 16;
 
 // From NIST SP 800-38a test case: - F.5.1 CTR-AES128.Encrypt
 // http://csrc.nist.gov/publications/nistpubs/800-38a/sp800-38a.pdf
-const uint8 kAesCtrKey[] = {0x2b, 0x7e, 0x15, 0x16, 0x28, 0xae, 0xd2, 0xa6,
+const uint8 kAesKey[] = {0x2b, 0x7e, 0x15, 0x16, 0x28, 0xae, 0xd2, 0xa6,
                          0xab, 0xf7, 0x15, 0x88, 0x09, 0xcf, 0x4f, 0x3c};
 
-const uint8 kAesCtrIv[] = {0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7,
+const uint8 kAesIv[] = {0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7,
                         0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff};
 
 const uint8 kAesCtrPlaintext[] = {
@@ -136,8 +136,8 @@ namespace media {
 class AesCtrEncryptorTest : public testing::Test {
  public:
   virtual void SetUp() {
-    key_.assign(kAesCtrKey, kAesCtrKey + arraysize(kAesCtrKey));
+    key_.assign(kAesKey, kAesKey + arraysize(kAesKey));
-    iv_.assign(kAesCtrIv, kAesCtrIv + arraysize(kAesCtrIv));
+    iv_.assign(kAesIv, kAesIv + arraysize(kAesIv));
     plaintext_.assign(kAesCtrPlaintext,
                       kAesCtrPlaintext + arraysize(kAesCtrPlaintext));
     ciphertext_.assign(kAesCtrCiphertext,
@@ -298,13 +298,13 @@ INSTANTIATE_TEST_CASE_P(IvTestCases,
                         AesCtrEncryptorIvTest,
                         ::testing::ValuesIn(kIvTestCases));
 
-class AesCbcEncryptorTestEncryptionDecryption : public testing::Test {
+class AesCbcPkcs5EncryptorTestEncryptionDecryption : public testing::Test {
  public:
   void TestEncryptionDecryption(const std::vector<uint8>& key,
                                 const std::vector<uint8>& iv,
                                 const std::string& plaintext,
                                 const std::string& expected_ciphertext_hex) {
-    AesCbcEncryptor encryptor;
+    AesCbcPkcs5Encryptor encryptor;
     EXPECT_TRUE(encryptor.InitializeWithIv(key, iv));
 
     std::string ciphertext;
@@ -312,7 +312,7 @@ class AesCbcEncryptorTestEncryptionDecryption : public testing::Test {
     EXPECT_EQ(expected_ciphertext_hex,
               base::HexEncode(ciphertext.data(), ciphertext.size()));
 
-    AesCbcDecryptor decryptor;
+    AesCbcPkcs5Decryptor decryptor;
     ASSERT_TRUE(decryptor.InitializeWithIv(key, iv));
 
     std::string decrypted;
@@ -321,7 +321,7 @@ class AesCbcEncryptorTestEncryptionDecryption : public testing::Test {
   }
 };
 
-TEST_F(AesCbcEncryptorTestEncryptionDecryption, EncryptAES256CBC) {
+TEST_F(AesCbcPkcs5EncryptorTestEncryptionDecryption, EncryptAES256CBC) {
   // NIST SP 800-38A test vector F.2.5 CBC-AES256.Encrypt.
   static const uint8 kAesCbcKey[] = {
       0x60, 0x3d, 0xeb, 0x10, 0x15, 0xca, 0x71, 0xbe, 0x2b, 0x73, 0xae,
@@ -370,7 +370,7 @@ TEST_F(AesCbcEncryptorTestEncryptionDecryption, EncryptAES256CBC) {
   TestEncryptionDecryption(key, iv, plaintext, expected_ciphertext_hex);
 }
 
-TEST_F(AesCbcEncryptorTestEncryptionDecryption, EncryptAES128CBCRegression) {
+TEST_F(AesCbcPkcs5EncryptorTestEncryptionDecryption, EncryptAES128CBCRegression) {
   const std::string kKey = "128=SixteenBytes";
   const std::string kIv = "Sweet Sixteen IV";
   const std::string kPlaintext =
@@ -385,7 +385,7 @@ TEST_F(AesCbcEncryptorTestEncryptionDecryption, EncryptAES128CBCRegression) {
   TestEncryptionDecryption(key, iv, kPlaintext, kExpectedCiphertextHex);
 }
 
-TEST_F(AesCbcEncryptorTestEncryptionDecryption, EncryptAES192CBCRegression) {
+TEST_F(AesCbcPkcs5EncryptorTestEncryptionDecryption, EncryptAES192CBCRegression) {
   const std::string kKey = "192bitsIsTwentyFourByte!";
   const std::string kIv = "Sweet Sixteen IV";
   const std::string kPlaintext = "Small text";
@@ -397,7 +397,7 @@ TEST_F(AesCbcEncryptorTestEncryptionDecryption, EncryptAES192CBCRegression) {
   TestEncryptionDecryption(key, iv, kPlaintext, kExpectedCiphertextHex);
 }
 
-class AesCbcEncryptorTest : public testing::Test {
+class AesCbcPkcs5EncryptorTest : public testing::Test {
  public:
   virtual void SetUp() {
     const std::string kKey = "128=SixteenBytes";
@@ -411,18 +411,18 @@ class AesCbcEncryptorTest : public testing::Test {
   std::vector<uint8> iv_;
 };
 
-TEST_F(AesCbcEncryptorTest, UnsupportedKeySize) {
+TEST_F(AesCbcPkcs5EncryptorTest, UnsupportedKeySize) {
-  AesCbcEncryptor encryptor;
+  AesCbcPkcs5Encryptor encryptor;
   EXPECT_FALSE(encryptor.InitializeWithIv(std::vector<uint8>(15, 0), iv_));
 }
 
-TEST_F(AesCbcEncryptorTest, UnsupportedIvSize) {
+TEST_F(AesCbcPkcs5EncryptorTest, UnsupportedIvSize) {
-  AesCbcEncryptor encryptor;
+  AesCbcPkcs5Encryptor encryptor;
   EXPECT_FALSE(encryptor.InitializeWithIv(key_, std::vector<uint8>(14, 0)));
 }
 
-TEST_F(AesCbcEncryptorTest, EmptyEncrypt) {
+TEST_F(AesCbcPkcs5EncryptorTest, EmptyEncrypt) {
-  AesCbcEncryptor encryptor;
+  AesCbcPkcs5Encryptor encryptor;
   ASSERT_TRUE(encryptor.InitializeWithIv(key_, iv_));
 
   std::string ciphertext;
@@ -432,13 +432,119 @@ TEST_F(AesCbcEncryptorTest, EmptyEncrypt) {
             base::HexEncode(ciphertext.data(), ciphertext.size()));
 }
 
-TEST_F(AesCbcEncryptorTest, CipherTextNotMultipleOfBlockSize) {
+TEST_F(AesCbcPkcs5EncryptorTest, CipherTextNotMultipleOfBlockSize) {
-  AesCbcDecryptor decryptor;
+  AesCbcPkcs5Decryptor decryptor;
   ASSERT_TRUE(decryptor.InitializeWithIv(key_, iv_));
 
   std::string plaintext;
   EXPECT_FALSE(decryptor.Decrypt("1", &plaintext));
 }
 
+class AesCbcCtsEncryptorDecryptorTest : public testing::Test {
+ public:
+  virtual void SetUp() {
+    key_.assign(kAesKey, kAesKey + arraysize(kAesKey));
+    iv_.assign(kAesIv, kAesIv + arraysize(kAesIv));
+  }
+
+  void TestEncryptDecryptSeparateBuffers(
+      const std::vector<uint8>& plaintext,
+      const std::vector<uint8>& expected_ciphertext) {
+    ASSERT_TRUE(encryptor_.InitializeWithIv(key_, iv_));
+    ASSERT_TRUE(decryptor_.InitializeWithIv(key_, iv_));
+
+    std::vector<uint8> encrypted;
+    encryptor_.Encrypt(plaintext, &encrypted);
+    EXPECT_EQ(expected_ciphertext, encrypted);
+
+    std::vector<uint8> decrypted;
+    decryptor_.Decrypt(encrypted, &decrypted);
+    EXPECT_EQ(plaintext, decrypted);
+  }
+
+  void TestEncryptDecryptInPlace(
+      const std::vector<uint8>& plaintext,
+      const std::vector<uint8>& expected_ciphertext) {
+    ASSERT_TRUE(encryptor_.InitializeWithIv(key_, iv_));
+    ASSERT_TRUE(decryptor_.InitializeWithIv(key_, iv_));
+
+    std::vector<uint8> buffer(plaintext);
+    encryptor_.Encrypt(buffer, &buffer);
+    EXPECT_EQ(expected_ciphertext, buffer);
+    decryptor_.Decrypt(buffer, &buffer);
+    EXPECT_EQ(plaintext, buffer);
+  }
+
+ protected:
+  std::vector<uint8> key_;
+  std::vector<uint8> iv_;
+  AesCbcCtsEncryptor encryptor_;
+  AesCbcCtsDecryptor decryptor_;
+};
+
+TEST_F(AesCbcCtsEncryptorDecryptorTest, TestWithResidualBytes) {
+  std::vector<uint8> plaintext;
+  ASSERT_TRUE(base::HexStringToBytes(
+      "e0818f2dc7caaa9edf09285a0c1fca98d39e9b08a47ab6911c4bbdf27d94"
+      "f917cdffc9ebb307141f23b0d3921e0ed7f86eb09381286f8e7a4f",
+      &plaintext));
+
+  std::vector<uint8> ciphertext;
+  ASSERT_TRUE(base::HexStringToBytes(
+      "b40a0b8704c74e22e8030cad6f272b34ace54cc7c9c64b2018bbcf23df018"
+      "39b14899441cf74a9fb2f2b229a609146f31be8e8a826eb6e857e",
+      &ciphertext));
+
+  TestEncryptDecryptSeparateBuffers(plaintext, ciphertext);
+  TestEncryptDecryptInPlace(plaintext, ciphertext);
+}
+
+TEST_F(AesCbcCtsEncryptorDecryptorTest, TestEvenBlocks) {
+  std::vector<uint8> plaintext;
+  ASSERT_TRUE(base::HexStringToBytes(
+      "3f593e7a204a5e70f2814dca05aa49d36f2daddc9a24e0515802c539efc3"
+      "1094b3ad6c26d6f5c0e387545ce6a4c2c14d",
+      &plaintext));
+
+  std::vector<uint8> ciphertext;
+  ASSERT_TRUE(base::HexStringToBytes(
+      "5f32cd0504b27b25ee04090d88d37d340c9c0a9fa50b05358b98fad4302ea"
+      "480148d8aa091f4e7d186a7223df153f6f7",
+      &ciphertext));
+
+  TestEncryptDecryptSeparateBuffers(plaintext, ciphertext);
+  TestEncryptDecryptInPlace(plaintext, ciphertext);
+}
+
+TEST_F(AesCbcCtsEncryptorDecryptorTest, TestOneBlockAndAHalf) {
+  std::vector<uint8> plaintext;
+  ASSERT_TRUE(base::HexStringToBytes(
+      "3f593e7a204a5e70f2814dca05aa49d36f2daddc9a4302ea",
+      &plaintext));
+
+  std::vector<uint8> ciphertext;
+  ASSERT_TRUE(base::HexStringToBytes(
+      "623fc113fe02ce85628deb58d652c6995f32cd0504b27b25",
+      &ciphertext));
+
+  TestEncryptDecryptSeparateBuffers(plaintext, ciphertext);
+  TestEncryptDecryptInPlace(plaintext, ciphertext);
+}
+
+TEST_F(AesCbcCtsEncryptorDecryptorTest, TestZeroEncryptedBlocks) {
+  std::vector<uint8> plaintext;
+  ASSERT_TRUE(base::HexStringToBytes("3f593e7a204a5e70f2", &plaintext));
+
+  TestEncryptDecryptSeparateBuffers(plaintext, plaintext);
+  TestEncryptDecryptInPlace(plaintext, plaintext);
+}
+
+TEST_F(AesCbcCtsEncryptorDecryptorTest, TestZeroBytes) {
+  std::vector<uint8> plaintext;
+
+  TestEncryptDecryptSeparateBuffers(plaintext, plaintext);
+  TestEncryptDecryptInPlace(plaintext, plaintext);
+}
+
 }  // namespace media
 }  // namespace edash_packager

media/base/request_signer.cc

@@ -19,7 +19,7 @@ RequestSigner::RequestSigner(const std::string& signer_name)
 RequestSigner::~RequestSigner() {}
 
 AesRequestSigner::AesRequestSigner(const std::string& signer_name,
-                                   scoped_ptr<AesCbcEncryptor> encryptor)
+                                   scoped_ptr<AesCbcPkcs5Encryptor> encryptor)
     : RequestSigner(signer_name), aes_cbc_encryptor_(encryptor.Pass()) {
   DCHECK(aes_cbc_encryptor_);
 }
@@ -39,7 +39,7 @@ AesRequestSigner* AesRequestSigner::CreateSigner(const std::string& signer_name,
     return NULL;
   }
 
-  scoped_ptr<AesCbcEncryptor> encryptor(new AesCbcEncryptor());
+  scoped_ptr<AesCbcPkcs5Encryptor> encryptor(new AesCbcPkcs5Encryptor());
   if (!encryptor->InitializeWithIv(aes_key, iv))
     return NULL;
   return new AesRequestSigner(signer_name, encryptor.Pass());

media/base/request_signer.h

@@ -15,7 +15,7 @@
 namespace edash_packager {
 namespace media {
 
-class AesCbcEncryptor;
+class AesCbcPkcs5Encryptor;
 class RsaPrivateKey;
 
 /// Abstract class used for signature generation.
@@ -57,9 +57,9 @@ class AesRequestSigner : public RequestSigner {
 
  private:
   AesRequestSigner(const std::string& signer_name,
-                   scoped_ptr<AesCbcEncryptor> encryptor);
+                   scoped_ptr<AesCbcPkcs5Encryptor> encryptor);
 
-  scoped_ptr<AesCbcEncryptor> aes_cbc_encryptor_;
+  scoped_ptr<AesCbcPkcs5Encryptor> aes_cbc_encryptor_;
 
   DISALLOW_COPY_AND_ASSIGN(AesRequestSigner);
 };