gecko/media/gmp-clearkey/0.1/ClearKeyDecryptionManager.cpp

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include <string.h>
#include <vector>

#include "ClearKeyDecryptionManager.h"
#include "gmp-decryption.h"
#include "mozilla/Assertions.h"
#include "mozilla/Attributes.h"

class ClearKeyDecryptor : public RefCounted
{
public:
  MOZ_IMPLICIT ClearKeyDecryptor();

  void InitKey(const Key& aKey);
  bool HasKey() const { return !!mKey.size(); }

  GMPErr Decrypt(uint8_t* aBuffer, uint32_t aBufferSize,
                 GMPEncryptedBufferMetadata* aMetadata);

  const Key& DecryptionKey() const { return mKey; }

private:
  ~ClearKeyDecryptor();

  Key mKey;
};


/* static */ ClearKeyDecryptionManager* ClearKeyDecryptionManager::sInstance = nullptr;

/* static */ ClearKeyDecryptionManager*
ClearKeyDecryptionManager::Get()
{
  if (!sInstance) {
    sInstance = new ClearKeyDecryptionManager();
  }
  return sInstance;
}

ClearKeyDecryptionManager::ClearKeyDecryptionManager()
{
  CK_LOGD("ClearKeyDecryptionManager::ClearKeyDecryptionManager");
}

ClearKeyDecryptionManager::~ClearKeyDecryptionManager()
{
  CK_LOGD("ClearKeyDecryptionManager::~ClearKeyDecryptionManager");

  sInstance = nullptr;

  for (auto it = mDecryptors.begin(); it != mDecryptors.end(); it++) {
    it->second->Release();
  }
  mDecryptors.clear();
}

bool
ClearKeyDecryptionManager::HasSeenKeyId(const KeyId& aKeyId) const
{
  CK_LOGD("ClearKeyDecryptionManager::HasSeenKeyId");
  return mDecryptors.find(aKeyId) != mDecryptors.end();
}

bool
ClearKeyDecryptionManager::IsExpectingKeyForKeyId(const KeyId& aKeyId) const
{
  CK_LOGD("ClearKeyDecryptionManager::IsExpectingKeyForKeyId");
  const auto& decryptor = mDecryptors.find(aKeyId);
  return decryptor != mDecryptors.end() && !decryptor->second->HasKey();
}

bool
ClearKeyDecryptionManager::HasKeyForKeyId(const KeyId& aKeyId) const
{
  CK_LOGD("ClearKeyDecryptionManager::HasKeyForKeyId");
  const auto& decryptor = mDecryptors.find(aKeyId);
  return decryptor != mDecryptors.end() && decryptor->second->HasKey();
}

const Key&
ClearKeyDecryptionManager::GetDecryptionKey(const KeyId& aKeyId)
{
  MOZ_ASSERT(HasKeyForKeyId(aKeyId));
  return mDecryptors[aKeyId]->DecryptionKey();
}

void
ClearKeyDecryptionManager::InitKey(KeyId aKeyId, Key aKey)
{
  CK_LOGD("ClearKeyDecryptionManager::InitKey");
  if (IsExpectingKeyForKeyId(aKeyId)) {
    mDecryptors[aKeyId]->InitKey(aKey);
  }
}

void
ClearKeyDecryptionManager::ExpectKeyId(KeyId aKeyId)
{
  CK_LOGD("ClearKeyDecryptionManager::ExpectKeyId");
  if (!HasSeenKeyId(aKeyId)) {
    mDecryptors[aKeyId] = new ClearKeyDecryptor();
  }
  mDecryptors[aKeyId]->AddRef();
}

void
ClearKeyDecryptionManager::ReleaseKeyId(KeyId aKeyId)
{
  CK_LOGD("ClearKeyDecryptionManager::ReleaseKeyId");
  ClearKeyDecryptor* decryptor = mDecryptors[aKeyId];
  if (!decryptor->Release()) {
    mDecryptors.erase(aKeyId);
  }
}

GMPErr
ClearKeyDecryptionManager::Decrypt(uint8_t* aBuffer, uint32_t aBufferSize,
                                   GMPEncryptedBufferMetadata* aMetadata)
{
  CK_LOGD("ClearKeyDecryptionManager::Decrypt");
  KeyId keyId(aMetadata->KeyId(), aMetadata->KeyId() + aMetadata->KeyIdSize());

  if (!HasKeyForKeyId(keyId)) {
    return GMPNoKeyErr;
  }

  return mDecryptors[keyId]->Decrypt(aBuffer, aBufferSize, aMetadata);
}

ClearKeyDecryptor::ClearKeyDecryptor()
{
  CK_LOGD("ClearKeyDecryptor ctor");
}

ClearKeyDecryptor::~ClearKeyDecryptor()
{
  CK_LOGD("ClearKeyDecryptor dtor; key ID = %08x...", *(uint32_t*)&mKey[0]);
}

void
ClearKeyDecryptor::InitKey(const Key& aKey)
{
  mKey = aKey;
}

GMPErr
ClearKeyDecryptor::Decrypt(uint8_t* aBuffer, uint32_t aBufferSize,
                           GMPEncryptedBufferMetadata* aMetadata)
{
  CK_LOGD("ClearKeyDecryptor::Decrypt");
  // If the sample is split up into multiple encrypted subsamples, we need to
  // stitch them into one continuous buffer for decryption.
  std::vector<uint8_t> tmp(aBufferSize);

  if (aMetadata->NumSubsamples()) {
    // Take all encrypted parts of subsamples and stitch them into one
    // continuous encrypted buffer.
    unsigned char* data = aBuffer;
    unsigned char* iter = &tmp[0];
    for (size_t i = 0; i < aMetadata->NumSubsamples(); i++) {
      data += aMetadata->ClearBytes()[i];
      uint32_t cipherBytes = aMetadata->CipherBytes()[i];

      memcpy(iter, data, cipherBytes);

      data += cipherBytes;
      iter += cipherBytes;
    }

    tmp.resize((size_t)(iter - &tmp[0]));
  } else {
    memcpy(&tmp[0], aBuffer, aBufferSize);
  }

  MOZ_ASSERT(aMetadata->IVSize() == 8 || aMetadata->IVSize() == 16);
  std::vector<uint8_t> iv(aMetadata->IV(), aMetadata->IV() + aMetadata->IVSize());
  iv.insert(iv.end(), CLEARKEY_KEY_LEN - aMetadata->IVSize(), 0);

  ClearKeyUtils::DecryptAES(mKey, tmp, iv);

  if (aMetadata->NumSubsamples()) {
    // Take the decrypted buffer, split up into subsamples, and insert those
    // subsamples back into their original position in the original buffer.
    unsigned char* data = aBuffer;
    unsigned char* iter = &tmp[0];
    for (size_t i = 0; i < aMetadata->NumSubsamples(); i++) {
      data += aMetadata->ClearBytes()[i];
      uint32_t cipherBytes = aMetadata->CipherBytes()[i];

      memcpy(data, iter, cipherBytes);

      data += cipherBytes;
      iter += cipherBytes;
    }
  } else {
    memcpy(aBuffer, &tmp[0], aBufferSize);
  }

  return GMPNoErr;
}