Support key rotation in widevine encryption key source

Change-Id: I05ded15fa666119c86a1d3f1c99123b9cda60b49

app/packager_main.cc

@@ -76,7 +76,10 @@ scoped_ptr<EncryptionKeySource> CreateEncryptionKeySource() {
     }
 
     encryption_key_source.reset(new WidevineEncryptionKeySource(
-        FLAGS_server_url, FLAGS_content_id, signer.Pass()));
+        FLAGS_server_url,
+        FLAGS_content_id,
+        signer.Pass(),
+        FLAGS_crypto_period_duration == 0 ? kDisableKeyRotation : 0));
   } else if (FLAGS_enable_fixed_key_encryption) {
     encryption_key_source = EncryptionKeySource::CreateFromHexStrings(
         FLAGS_key_id, FLAGS_key, FLAGS_pssh, "");

media/base/aes_encryptor.cc

@@ -169,11 +169,12 @@ void AesCbcEncryptor::Encrypt(const std::string& plaintext,
   padded_text.append(num_padding_bytes, static_cast<char>(num_padding_bytes));
 
   ciphertext->resize(padded_text.size());
+  std::vector<uint8> iv(iv_);
   AES_cbc_encrypt(reinterpret_cast<const uint8*>(padded_text.data()),
                   reinterpret_cast<uint8*>(string_as_array(ciphertext)),
                   padded_text.size(),
                   encrypt_key_.get(),
-                  &iv_[0],
+                  &iv[0],
                   AES_ENCRYPT);
 }
 

media/base/encryption_key_source.cc

@@ -30,7 +30,7 @@ Status EncryptionKeySource::GetKey(TrackType track_type, EncryptionKey* key) {
   return Status::OK;
 }
 
-Status EncryptionKeySource::GetCryptoPeriodKey(size_t crypto_period_index,
+Status EncryptionKeySource::GetCryptoPeriodKey(uint32 crypto_period_index,
                                                TrackType track_type,
                                                EncryptionKey* key) {
   NOTIMPLEMENTED();

media/base/encryption_key_source.h

@@ -43,7 +43,7 @@ class EncryptionKeySource {
 
   /// Get encryption key of the specified track type at the specified index.
   /// @return OK on success, an error status otherwise.
-  virtual Status GetCryptoPeriodKey(size_t crypto_period_index,
+  virtual Status GetCryptoPeriodKey(uint32 crypto_period_index,
                                     TrackType track_type,
                                     EncryptionKey* key);
 

media/base/producer_consumer_queue.h

@@ -17,16 +17,26 @@
 
 namespace media {
 
+static const size_t kUnlimitedCapacity = 0u;
+static const int64 kInfiniteTimeout = -1;
+
 /// A thread safe producer consumer queue implementation. It allows the standard
 /// push and pop operations. It also maintains a monotonically-increasing
 /// element position and allows peeking at the element at certain position.
 template <class T>
 class ProducerConsumerQueue {
  public:
-  /// Create a ProducerConsumerQueue.
+  /// Create a ProducerConsumerQueue starting from position 0.
   /// @param capacity is the maximum number of elements that the queue can hold
   ///        at once. A value of zero means unlimited capacity.
   explicit ProducerConsumerQueue(size_t capacity);
+
+  /// Create a ProducerConsumerQueue starting from indicated position.
+  /// @param capacity is the maximum number of elements that the queue can hold
+  ///        at once. A value of zero means unlimited capacity.
+  /// @param starting_pos is the starting head position.
+  ProducerConsumerQueue(size_t capacity, size_t starting_pos);
+
   ~ProducerConsumerQueue();
 
   /// Push an element to the back of the queue. If the queue has reached its
@@ -89,14 +99,14 @@ class ProducerConsumerQueue {
   ///         returned value may be meaningless if the queue is empty.
   size_t HeadPos() const {
     base::AutoLock l(lock_);
-    return head_;
+    return head_pos_;
   }
 
   /// @return The position of the tail element in the queue. Note that the
   ///         returned value may be meaningless if the queue is empty.
   size_t TailPos() const {
     base::AutoLock l(lock_);
-    return head_ + q_.size() - 1;
+    return head_pos_ + q_.size() - 1;
   }
 
   /// @return true if the queue has been stopped using Stop(). This allows
@@ -107,12 +117,12 @@ class ProducerConsumerQueue {
   }
 
  private:
-  // Move head_ to center on pos.
+  // Move head_pos_ to center on pos.
   void SlideHeadOnCenter(size_t pos);
 
   const size_t capacity_;  // Maximum number of elements; zero means unlimited.
   mutable base::Lock lock_;  // Lock protecting all other variables below.
-  size_t head_;              // Head position.
+  size_t head_pos_;          // Head position.
   std::deque<T> q_;          // Internal queue holding the elements.
   base::ConditionVariable not_empty_cv_;
   base::ConditionVariable not_full_cv_;
@@ -126,12 +136,23 @@ class ProducerConsumerQueue {
 template <class T>
 ProducerConsumerQueue<T>::ProducerConsumerQueue(size_t capacity)
     : capacity_(capacity),
-      head_(0),
+      head_pos_(0),
       not_empty_cv_(&lock_),
       not_full_cv_(&lock_),
       new_element_cv_(&lock_),
       stop_requested_(false) {}
 
+template <class T>
+ProducerConsumerQueue<T>::ProducerConsumerQueue(size_t capacity,
+                                                size_t starting_pos)
+    : capacity_(capacity),
+      head_pos_(starting_pos),
+      not_empty_cv_(&lock_),
+      not_full_cv_(&lock_),
+      new_element_cv_(&lock_),
+      stop_requested_(false) {
+}
+
 template <class T>
 ProducerConsumerQueue<T>::~ProducerConsumerQueue() {}
 
@@ -218,7 +239,7 @@ Status ProducerConsumerQueue<T>::Pop(T* element, int64 timeout_ms) {
 
   *element = q_.front();
   q_.pop_front();
-  ++head_;
+  ++head_pos_;
 
   // Signal other consumers if we have more elements.
   if (woken && !q_.empty())
@@ -231,10 +252,11 @@ Status ProducerConsumerQueue<T>::Peek(size_t pos,
                                       T* element,
                                       int64 timeout_ms) {
   base::AutoLock l(lock_);
-  if (pos < head_) {
+  if (pos < head_pos_) {
     return Status(
         error::INVALID_ARGUMENT,
-        base::StringPrintf("pos (%zu) is too small; head is %zu.", pos, head_));
+        base::StringPrintf(
+            "pos (%zu) is too small; head is at %zu.", pos, head_pos_));
   }
 
   bool woken = false;
@@ -242,10 +264,10 @@ Status ProducerConsumerQueue<T>::Peek(size_t pos,
   base::ElapsedTimer timer;
   base::TimeDelta timeout_delta = base::TimeDelta::FromMilliseconds(timeout_ms);
 
-  // Move head_ to create some space (move the sliding window centered @ pos).
+  // Move head to create some space (move the sliding window centered @ pos).
   SlideHeadOnCenter(pos);
 
-  while (pos >= head_ + q_.size()) {
+  while (pos >= head_pos_ + q_.size()) {
     if (stop_requested_)
       return Status(error::STOPPED, "");
 
@@ -262,12 +284,12 @@ Status ProducerConsumerQueue<T>::Peek(size_t pos,
         return Status(error::TIME_OUT, "Time out on peeking.");
       }
     }
-    // Move head_ to create some space (move the sliding window centered @ pos).
+    // Move head to create some space (move the sliding window centered @ pos).
     SlideHeadOnCenter(pos);
     woken = true;
   }
 
-  *element = q_[pos - head_];
+  *element = q_[pos - head_pos_];
 
   // Signal other consumers if we have more elements.
   if (woken && !q_.empty())
@@ -281,11 +303,11 @@ void ProducerConsumerQueue<T>::SlideHeadOnCenter(size_t pos) {
 
   if (capacity_) {
     // Signal producer to proceed if we are going to create some capacity.
-    if (q_.size() == capacity_ && pos > head_ + capacity_ / 2)
+    if (q_.size() == capacity_ && pos > head_pos_ + capacity_ / 2)
       not_full_cv_.Signal();
 
-    while (!q_.empty() && pos > head_ + capacity_ / 2) {
+    while (!q_.empty() && pos > head_pos_ + capacity_ / 2) {
-      ++head_;
+      ++head_pos_;
       q_.pop_front();
     }
   }

media/base/producer_consumer_queue_unittest.cc

@@ -13,10 +13,8 @@
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace {
-const size_t kUnlimitedCapacity = 0u;
 const size_t kCapacity = 10u;
 const int64 kTimeout = 100;  // 0.1s.
-const int64 kInfiniteTimeout = -1;
 
 // Check that the |delta| is approximately |time_in_milliseconds|.
 bool CheckTimeApproxEqual(int64 time_in_milliseconds,

media/base/widevine_encryption_key_source.cc

@@ -7,8 +7,10 @@
 #include "media/base/widevine_encryption_key_source.h"
 
 #include "base/base64.h"
+#include "base/bind.h"
 #include "base/json/json_reader.h"
 #include "base/json/json_writer.h"
+#include "base/memory/ref_counted.h"
 #include "base/stl_util.h"
 #include "base/values.h"
 #include "media/base/http_fetcher.h"
@@ -34,6 +36,11 @@ const char kLicenseStatusTransientError[] = "INTERNAL_ERROR";
 const int kNumTransientErrorRetries = 5;
 const int kFirstRetryDelayMilliseconds = 1000;
 
+// Default crypto period count, which is the number of keys to fetch on every
+// key rotation enabled request.
+const int kDefaultCryptoPeriodCount = 10;
+const int kGetKeyTimeoutInSeconds = 5 * 60;  // 5 minutes.
+
 bool Base64StringToBytes(const std::string& base64_string,
                          std::vector<uint8>* bytes) {
   DCHECK(bytes);
@@ -93,42 +100,68 @@ bool GetPsshData(const base::DictionaryValue& track_dict,
 
 namespace media {
 
+// A ref counted wrapper for EncryptionKeyMap.
+class WidevineEncryptionKeySource::RefCountedEncryptionKeyMap
+    : public base::RefCountedThreadSafe<RefCountedEncryptionKeyMap> {
+ public:
+  explicit RefCountedEncryptionKeyMap(EncryptionKeyMap* encryption_key_map) {
+    DCHECK(encryption_key_map);
+    encryption_key_map_.swap(*encryption_key_map);
+  }
+
+  std::map<EncryptionKeySource::TrackType, EncryptionKey*>& map() {
+    return encryption_key_map_;
+  }
+
+ private:
+  friend class base::RefCountedThreadSafe<RefCountedEncryptionKeyMap>;
+
+  ~RefCountedEncryptionKeyMap() { STLDeleteValues(&encryption_key_map_); }
+
+  EncryptionKeyMap encryption_key_map_;
+
+  DISALLOW_COPY_AND_ASSIGN(RefCountedEncryptionKeyMap);
+};
+
 WidevineEncryptionKeySource::WidevineEncryptionKeySource(
     const std::string& server_url,
     const std::string& content_id,
-    scoped_ptr<RequestSigner> signer)
+    scoped_ptr<RequestSigner> signer,
+    int first_crypto_period_index)
     : http_fetcher_(new SimpleHttpFetcher()),
       server_url_(server_url),
       content_id_(content_id),
       signer_(signer.Pass()),
-      key_fetched_(false) {
+      key_rotation_enabled_(first_crypto_period_index >= 0),
+      crypto_period_count_(kDefaultCryptoPeriodCount),
+      first_crypto_period_index_(first_crypto_period_index),
+      key_production_thread_(
+          "KeyProductionThread",
+          base::Bind(&WidevineEncryptionKeySource::FetchKeysTask,
+                     base::Unretained(this))),
+      key_pool_(kDefaultCryptoPeriodCount,
+                key_rotation_enabled_ ? first_crypto_period_index : 0) {
   DCHECK(signer_);
+  key_production_thread_.Start();
 }
+
 WidevineEncryptionKeySource::~WidevineEncryptionKeySource() {
-  STLDeleteValues(&encryption_key_map_);
+  key_pool_.Stop();
+  key_production_thread_.Join();
 }
 
 Status WidevineEncryptionKeySource::GetKey(TrackType track_type,
                                            EncryptionKey* key) {
-  DCHECK(track_type == TRACK_TYPE_SD || track_type == TRACK_TYPE_HD ||
+  DCHECK(!key_rotation_enabled_);
-         track_type == TRACK_TYPE_AUDIO);
+  return GetKeyInternal(0u, track_type, key);
-  Status status;
-  if (!key_fetched_) {
-    base::AutoLock auto_lock(lock_);
-    if (!key_fetched_) {
-      status = FetchKeys();
-      if (status.ok())
-        key_fetched_ = true;
 }
-  }
+
-  if (!status.ok())
+Status WidevineEncryptionKeySource::GetCryptoPeriodKey(
-    return status;
+    uint32 crypto_period_index,
-  if (encryption_key_map_.find(track_type) == encryption_key_map_.end()) {
+    TrackType track_type,
-    return Status(error::INTERNAL_ERROR,
+    EncryptionKey* key) {
-                  "Cannot find key of type " + TrackTypeToString(track_type));
+  DCHECK(key_rotation_enabled_);
-  }
+  return GetKeyInternal(crypto_period_index, track_type, key);
-  *key = *encryption_key_map_[track_type];
-  return Status::OK;
 }
 
 void WidevineEncryptionKeySource::set_http_fetcher(
@@ -136,9 +169,50 @@ void WidevineEncryptionKeySource::set_http_fetcher(
   http_fetcher_ = http_fetcher.Pass();
 }
 
-Status WidevineEncryptionKeySource::FetchKeys() {
+Status WidevineEncryptionKeySource::GetKeyInternal(
+    uint32 crypto_period_index,
+    TrackType track_type,
+    EncryptionKey* key) {
+  DCHECK_LE(track_type, NUM_VALID_TRACK_TYPES);
+  DCHECK_NE(track_type, TRACK_TYPE_UNKNOWN);
+
+  scoped_refptr<RefCountedEncryptionKeyMap> ref_counted_encryption_key_map;
+  Status status = key_pool_.Peek(crypto_period_index,
+                                 &ref_counted_encryption_key_map,
+                                 kGetKeyTimeoutInSeconds * 1000);
+  if (!status.ok()) {
+    if (status.error_code() == error::STOPPED) {
+      CHECK(!common_encryption_request_status_.ok());
+      return common_encryption_request_status_;
+    }
+    return status;
+  }
+
+  EncryptionKeyMap& encryption_key_map = ref_counted_encryption_key_map->map();
+  if (encryption_key_map.find(track_type) == encryption_key_map.end()) {
+    return Status(error::INTERNAL_ERROR,
+                  "Cannot find key of type " + TrackTypeToString(track_type));
+  }
+  *key = *encryption_key_map[track_type];
+  return Status::OK;
+}
+
+void WidevineEncryptionKeySource::FetchKeysTask() {
+  Status status = FetchKeys(first_crypto_period_index_);
+  if (key_rotation_enabled_) {
+    while (status.ok()) {
+      first_crypto_period_index_ += crypto_period_count_;
+      status = FetchKeys(first_crypto_period_index_);
+    }
+  }
+  common_encryption_request_status_ = status;
+  key_pool_.Stop();
+}
+
+Status WidevineEncryptionKeySource::FetchKeys(
+    uint32 first_crypto_period_index) {
   std::string request;
-  FillRequest(content_id_, &request);
+  FillRequest(content_id_, first_crypto_period_index, &request);
 
   std::string message;
   Status status = SignRequest(request, &message);
@@ -185,6 +259,7 @@ Status WidevineEncryptionKeySource::FetchKeys() {
 }
 
 void WidevineEncryptionKeySource::FillRequest(const std::string& content_id,
+                                              uint32 first_crypto_period_index,
                                               std::string* request) {
   DCHECK(request);
 
@@ -215,6 +290,13 @@ void WidevineEncryptionKeySource::FillRequest(const std::string& content_id,
   drm_types->AppendString("WIDEVINE");
   request_dict.Set("drm_types", drm_types);
 
+  // Build key rotation fields.
+  if (key_rotation_enabled_) {
+    request_dict.SetInteger("first_crypto_period_index",
+                            first_crypto_period_index);
+    request_dict.SetInteger("crypto_period_count", crypto_period_count_);
+  }
+
   base::JSONWriter::Write(&request_dict, request);
 }
 
@@ -288,17 +370,40 @@ bool WidevineEncryptionKeySource::ExtractEncryptionKey(
 
   const base::ListValue* tracks;
   RCHECK(license_dict->GetList("tracks", &tracks));
-  RCHECK(tracks->GetSize() >= NUM_VALID_TRACK_TYPES);
+  RCHECK(key_rotation_enabled_
+             ? tracks->GetSize() >= NUM_VALID_TRACK_TYPES * crypto_period_count_
+             : tracks->GetSize() >= NUM_VALID_TRACK_TYPES);
 
+  int current_crypto_period_index = first_crypto_period_index_;
+
+  EncryptionKeyMap encryption_key_map;
   for (size_t i = 0; i < tracks->GetSize(); ++i) {
     const base::DictionaryValue* track_dict;
     RCHECK(tracks->GetDictionary(i, &track_dict));
 
+    if (key_rotation_enabled_) {
+      int crypto_period_index;
+      RCHECK(
+          track_dict->GetInteger("crypto_period_index", &crypto_period_index));
+      if (crypto_period_index != current_crypto_period_index) {
+        if (crypto_period_index != current_crypto_period_index + 1) {
+          LOG(ERROR) << "Expecting crypto period index "
+                     << current_crypto_period_index << " or "
+                     << current_crypto_period_index + 1 << "; Seen "
+                     << crypto_period_index << " at track " << i;
+          return false;
+        }
+        if (!PushToKeyPool(&encryption_key_map))
+          return false;
+        ++current_crypto_period_index;
+      }
+    }
+
     std::string track_type_str;
     RCHECK(track_dict->GetString("type", &track_type_str));
     TrackType track_type = GetTrackTypeFromString(track_type_str);
     DCHECK_NE(TRACK_TYPE_UNKNOWN, track_type);
-    RCHECK(encryption_key_map_.find(track_type) == encryption_key_map_.end());
+    RCHECK(encryption_key_map.find(track_type) == encryption_key_map.end());
 
     scoped_ptr<EncryptionKey> encryption_key(new EncryptionKey());
     std::vector<uint8> pssh_data;
@@ -307,7 +412,24 @@ bool WidevineEncryptionKeySource::ExtractEncryptionKey(
         !GetPsshData(*track_dict, &pssh_data))
       return false;
     encryption_key->pssh = PsshBoxFromPsshData(pssh_data);
-    encryption_key_map_[track_type] = encryption_key.release();
+    encryption_key_map[track_type] = encryption_key.release();
+  }
+
+  DCHECK(!encryption_key_map.empty());
+  return PushToKeyPool(&encryption_key_map);
+}
+
+bool WidevineEncryptionKeySource::PushToKeyPool(
+    EncryptionKeyMap* encryption_key_map) {
+  DCHECK(encryption_key_map);
+  Status status =
+      key_pool_.Push(scoped_refptr<RefCountedEncryptionKeyMap>(
+                         new RefCountedEncryptionKeyMap(encryption_key_map)),
+                     kInfiniteTimeout);
+  encryption_key_map->clear();
+  if (!status.ok()) {
+    DCHECK_EQ(error::STOPPED, status.error_code());
+    return false;
   }
   return true;
 }

media/base/widevine_encryption_key_source.h

@@ -11,10 +11,13 @@
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
-#include "base/synchronization/lock.h"
+#include "media/base/closure_thread.h"
 #include "media/base/encryption_key_source.h"
+#include "media/base/producer_consumer_queue.h"
 
 namespace media {
+/// A negative crypto period index disables key rotation.
+static const int kDisableKeyRotation = -1;
 
 class HttpFetcher;
 class RequestSigner;
@@ -25,26 +28,47 @@ class WidevineEncryptionKeySource : public EncryptionKeySource {
  public:
   /// @param server_url is the Widevine common encryption server url.
   /// @param content_id the unique id identify the content to be encrypted.
-  /// @param signer must not be NULL.
+  /// @param signer signs the request message. It should not be NULL.
+  /// @param first_crypto_period_index indicates the starting crypto period
+  ///        index. Set it to kDisableKeyRotation to disable key rotation.
   WidevineEncryptionKeySource(const std::string& server_url,
                               const std::string& content_id,
-                              scoped_ptr<RequestSigner> signer);
+                              scoped_ptr<RequestSigner> signer,
+                              int first_crypto_period_index);
   virtual ~WidevineEncryptionKeySource();
 
-  /// EncryptionKeySource implementation override.
+  /// @name EncryptionKeySource implementation overrides.
+  /// @{
   virtual Status GetKey(TrackType track_type, EncryptionKey* key) OVERRIDE;
+  virtual Status GetCryptoPeriodKey(uint32 crypto_period_index,
+                                    TrackType track_type,
+                                    EncryptionKey* key) OVERRIDE;
+  /// @}
 
   /// Inject an @b HttpFetcher object, mainly used for testing.
   /// @param http_fetcher points to the @b HttpFetcher object to be injected.
   void set_http_fetcher(scoped_ptr<HttpFetcher> http_fetcher);
 
  private:
+  typedef std::map<TrackType, EncryptionKey*> EncryptionKeyMap;
+  class RefCountedEncryptionKeyMap;
+
+  // Internal routine for getting keys.
+  Status GetKeyInternal(uint32 crypto_period_index,
+                        TrackType track_type,
+                        EncryptionKey* key);
+
+  // The closure task to fetch keys repeatedly.
+  void FetchKeysTask();
+
   // Fetch keys from server.
-  Status FetchKeys();
+  Status FetchKeys(uint32 first_crypto_period_index);
 
   // Fill |request| with necessary fields for Widevine encryption request.
   // |request| should not be NULL.
-  void FillRequest(const std::string& content_id, std::string* request);
+  void FillRequest(const std::string& content_id,
+                   uint32 first_crypto_period_index,
+                   std::string* request);
   // Sign and properly format |request|.
   // |signed_request| should not be NULL. Return OK on success.
   Status SignRequest(const std::string& request, std::string* signed_request);
@@ -56,6 +80,8 @@ class WidevineEncryptionKeySource : public EncryptionKeySource {
   // failure is because of a transient error from the server. |transient_error|
   // should not be NULL.
   bool ExtractEncryptionKey(const std::string& response, bool* transient_error);
+  // Push the keys to the key pool.
+  bool PushToKeyPool(EncryptionKeyMap* encryption_key_map);
 
   // The fetcher object used to fetch HTTP response from server.
   // It is initialized to a default fetcher on class initialization.
@@ -65,9 +91,12 @@ class WidevineEncryptionKeySource : public EncryptionKeySource {
   std::string content_id_;
   scoped_ptr<RequestSigner> signer_;
 
-  mutable base::Lock lock_;
+  const bool key_rotation_enabled_;
-  bool key_fetched_;  // Protected by lock_;
+  const uint32 crypto_period_count_;
-  std::map<TrackType, EncryptionKey*> encryption_key_map_;
+  uint32 first_crypto_period_index_;
+  ClosureThread key_production_thread_;
+  ProducerConsumerQueue<scoped_refptr<RefCountedEncryptionKeyMap> > key_pool_;
+  Status common_encryption_request_status_;
 
   DISALLOW_COPY_AND_ASSIGN(WidevineEncryptionKeySource);
 };

media/base/widevine_encryption_key_source_unittest.cc

@@ -7,6 +7,7 @@
 #include "media/base/widevine_encryption_key_source.h"
 
 #include "base/base64.h"
+#include "base/strings/string_number_conversions.h"
 #include "base/strings/stringprintf.h"
 #include "media/base/http_fetcher.h"
 #include "media/base/request_signer.h"
@@ -89,6 +90,7 @@ std::string GetPsshDataFromPsshBox(const std::string& pssh_box) {
 
 using ::testing::_;
 using ::testing::DoAll;
+using ::testing::InSequence;
 using ::testing::Return;
 using ::testing::SetArgPointee;
 
@@ -129,9 +131,12 @@ class WidevineEncryptionKeySourceTest : public ::testing::Test {
         mock_http_fetcher_(new MockHttpFetcher()) {}
 
  protected:
-  void CreateWidevineEncryptionKeySource() {
+  void CreateWidevineEncryptionKeySource(int first_crypto_period_index) {
     widevine_encryption_key_source_.reset(new WidevineEncryptionKeySource(
-        kServerUrl, kContentId, mock_request_signer_.PassAs<RequestSigner>()));
+        kServerUrl,
+        kContentId,
+        mock_request_signer_.PassAs<RequestSigner>(),
+        first_crypto_period_index));
     widevine_encryption_key_source_->set_http_fetcher(
         mock_http_fetcher_.PassAs<HttpFetcher>());
   }
@@ -155,11 +160,11 @@ TEST_F(WidevineEncryptionKeySourceTest, GetTrackTypeFromString) {
             EncryptionKeySource::GetTrackTypeFromString("FOO"));
 }
 
-TEST_F(WidevineEncryptionKeySourceTest, GeneratureSignatureFailure) {
+TEST_F(WidevineEncryptionKeySourceTest, GenerateSignatureFailure) {
   EXPECT_CALL(*mock_request_signer_, GenerateSignature(_, _))
       .WillOnce(Return(false));
 
-  CreateWidevineEncryptionKeySource();
+  CreateWidevineEncryptionKeySource(kDisableKeyRotation);
   EncryptionKey encryption_key;
   ASSERT_EQ(Status(error::INTERNAL_ERROR, "Signature generation failed."),
             widevine_encryption_key_source_->GetKey(
@@ -183,7 +188,7 @@ TEST_F(WidevineEncryptionKeySourceTest, HttpPostFailure) {
   EXPECT_CALL(*mock_http_fetcher_, Post(kServerUrl, expected_post_data, _))
       .WillOnce(Return(kMockStatus));
 
-  CreateWidevineEncryptionKeySource();
+  CreateWidevineEncryptionKeySource(kDisableKeyRotation);
   EncryptionKey encryption_key;
   ASSERT_EQ(kMockStatus,
             widevine_encryption_key_source_->GetKey(
@@ -194,13 +199,13 @@ TEST_F(WidevineEncryptionKeySourceTest, LicenseStatusOK) {
   EXPECT_CALL(*mock_request_signer_, GenerateSignature(_, _))
       .WillOnce(Return(true));
 
-  std::string expected_response = base::StringPrintf(
+  std::string mock_response = base::StringPrintf(
       kHttpResponseFormat, Base64Encode(GenerateMockLicenseResponse()).c_str());
 
   EXPECT_CALL(*mock_http_fetcher_, Post(_, _, _))
-      .WillOnce(DoAll(SetArgPointee<2>(expected_response), Return(Status::OK)));
+      .WillOnce(DoAll(SetArgPointee<2>(mock_response), Return(Status::OK)));
 
-  CreateWidevineEncryptionKeySource();
+  CreateWidevineEncryptionKeySource(kDisableKeyRotation);
 
   EncryptionKey encryption_key;
   const std::string kTrackTypes[] = {"SD", "HD", "AUDIO"};
@@ -221,7 +226,7 @@ TEST_F(WidevineEncryptionKeySourceTest, RetryOnTransientError) {
 
   std::string mock_license_status = base::StringPrintf(
       kLicenseResponseFormat, kLicenseStatusTransientError, "");
-  std::string expected_response = base::StringPrintf(
+  std::string mock_response = base::StringPrintf(
       kHttpResponseFormat, Base64Encode(mock_license_status).c_str());
 
   std::string expected_retried_response = base::StringPrintf(
@@ -229,11 +234,11 @@ TEST_F(WidevineEncryptionKeySourceTest, RetryOnTransientError) {
 
   // Retry is expected on transient error.
   EXPECT_CALL(*mock_http_fetcher_, Post(_, _, _))
-      .WillOnce(DoAll(SetArgPointee<2>(expected_response), Return(Status::OK)))
+      .WillOnce(DoAll(SetArgPointee<2>(mock_response), Return(Status::OK)))
       .WillOnce(DoAll(SetArgPointee<2>(expected_retried_response),
                       Return(Status::OK)));
 
-  CreateWidevineEncryptionKeySource();
+  CreateWidevineEncryptionKeySource(kDisableKeyRotation);
   EncryptionKey encryption_key;
   ASSERT_OK(widevine_encryption_key_source_->GetKey(
       EncryptionKeySource::TRACK_TYPE_SD, &encryption_key));
@@ -255,13 +260,131 @@ TEST_F(WidevineEncryptionKeySourceTest, NoRetryOnUnknownError) {
   EXPECT_CALL(*mock_http_fetcher_, Post(_, _, _))
       .WillOnce(DoAll(SetArgPointee<2>(mock_response), Return(Status::OK)));
 
-  CreateWidevineEncryptionKeySource();
+  CreateWidevineEncryptionKeySource(kDisableKeyRotation);
   EncryptionKey encryption_key;
-  ASSERT_EQ(
+  Status status = widevine_encryption_key_source_->GetKey(
-      error::SERVER_ERROR,
+      EncryptionKeySource::TRACK_TYPE_SD, &encryption_key);
-      widevine_encryption_key_source_->GetKey(
+  ASSERT_EQ(error::SERVER_ERROR, status.error_code());
+}
+
+namespace {
+
+const char kCryptoPeriodRequestMessageFormat[] =
+    "{\"content_id\":\"%s\",\"crypto_period_count\":%u,\"drm_types\":["
+    "\"WIDEVINE\"],\"first_crypto_period_index\":%u,\"policy\":\"\","
+    "\"tracks\":[{\"type\":\"SD\"},{\"type\":\"HD\"},{\"type\":\"AUDIO\"}]}";
+
+const char kCryptoPeriodTrackFormat[] =
+    "{\"type\":\"%s\",\"key_id\":\"\",\"key\":"
+    "\"%s\",\"pssh\":[{\"drm_type\":\"WIDEVINE\",\"data\":\"\"}], "
+    "\"crypto_period_index\":%u}";
+
+std::string GetMockKey(const std::string& track_type, uint32 index) {
+  return "MockKey" + track_type + "@" + base::UintToString(index);
+}
+
+std::string GenerateMockLicenseResponse(uint32 initial_crypto_period_index,
+                                        uint32 crypto_period_count) {
+  const std::string kTrackTypes[] = {"SD", "HD", "AUDIO"};
+  std::string tracks;
+  for (uint32 index = initial_crypto_period_index;
+      index < initial_crypto_period_index + crypto_period_count;
+       ++index) {
+    for (size_t i = 0; i < 3; ++i) {
+      if (!tracks.empty())
+        tracks += ",";
+      tracks += base::StringPrintf(
+          kCryptoPeriodTrackFormat,
+          kTrackTypes[i].c_str(),
+          Base64Encode(GetMockKey(kTrackTypes[i], index)).c_str(),
+          index);
+    }
+  }
+  return base::StringPrintf(kLicenseResponseFormat, "OK", tracks.c_str());
+}
+
+}  // namespace
+
+TEST_F(WidevineEncryptionKeySourceTest, KeyRotationTest) {
+  const uint32 kFirstCryptoPeriodIndex = 8;
+  const uint32 kCryptoPeriodCount = 10;
+  // Array of indexes to be checked.
+  const uint32 kCryptoPeriodIndexes[] = {kFirstCryptoPeriodIndex, 17, 37,
+                                         38,                      36, 39};
+  // Derived from kCryptoPeriodIndexes: ceiling((39 - 8 ) / 10).
+  const uint32 kCryptoIterations = 4;
+
+  // Generate expectations in sequence.
+  InSequence dummy;
+  for (uint32 i = 0; i < kCryptoIterations; ++i) {
+    uint32 first_crypto_period_index =
+        kFirstCryptoPeriodIndex + i * kCryptoPeriodCount;
+    std::string expected_message =
+        base::StringPrintf(kCryptoPeriodRequestMessageFormat,
+                           Base64Encode(kContentId).c_str(),
+                           kCryptoPeriodCount,
+                           first_crypto_period_index);
+    EXPECT_CALL(*mock_request_signer_, GenerateSignature(expected_message, _))
+        .WillOnce(DoAll(SetArgPointee<1>(kMockSignature), Return(true)));
+
+    std::string mock_response = base::StringPrintf(
+        kHttpResponseFormat,
+        Base64Encode(GenerateMockLicenseResponse(first_crypto_period_index,
+                                                 kCryptoPeriodCount)).c_str());
+    EXPECT_CALL(*mock_http_fetcher_, Post(_, _, _))
+        .WillOnce(DoAll(SetArgPointee<2>(mock_response), Return(Status::OK)));
+  }
+
+  CreateWidevineEncryptionKeySource(kFirstCryptoPeriodIndex);
+
+  EncryptionKey encryption_key;
+
+  // Index before kFirstCryptoPeriodIndex is invalid.
+  Status status = widevine_encryption_key_source_->GetCryptoPeriodKey(
+      kFirstCryptoPeriodIndex - 1,
       EncryptionKeySource::TRACK_TYPE_SD,
-                                           &encryption_key).error_code());
+      &encryption_key);
+  EXPECT_EQ(error::INVALID_ARGUMENT, status.error_code());
+
+  for (size_t i = 0; i < arraysize(kCryptoPeriodIndexes); ++i) {
+    const std::string kTrackTypes[] = {"SD", "HD", "AUDIO"};
+    for (size_t j = 0; j < 3; ++j) {
+      ASSERT_OK(widevine_encryption_key_source_->GetCryptoPeriodKey(
+          kCryptoPeriodIndexes[i],
+          EncryptionKeySource::GetTrackTypeFromString(kTrackTypes[j]),
+          &encryption_key));
+      EXPECT_EQ(GetMockKey(kTrackTypes[j], kCryptoPeriodIndexes[i]),
+                ToString(encryption_key.key));
+    }
+  }
+
+  // The old crypto period indexes should have been garbage collected.
+  status = widevine_encryption_key_source_->GetCryptoPeriodKey(
+      kFirstCryptoPeriodIndex,
+      EncryptionKeySource::TRACK_TYPE_SD,
+      &encryption_key);
+  EXPECT_EQ(error::INVALID_ARGUMENT, status.error_code());
+}
+
+class WidevineEncryptionKeySourceDeathTest
+    : public WidevineEncryptionKeySourceTest {};
+
+TEST_F(WidevineEncryptionKeySourceDeathTest,
+       GetCryptoPeriodKeyOnNonKeyRotationSource) {
+  CreateWidevineEncryptionKeySource(kDisableKeyRotation);
+  EncryptionKey encryption_key;
+  EXPECT_DEBUG_DEATH(
+      widevine_encryption_key_source_->GetCryptoPeriodKey(
+          0, EncryptionKeySource::TRACK_TYPE_SD, &encryption_key),
+      "");
+}
+
+TEST_F(WidevineEncryptionKeySourceDeathTest, GetKeyOnKeyRotationSource) {
+  CreateWidevineEncryptionKeySource(0);
+  EncryptionKey encryption_key;
+  EXPECT_DEBUG_DEATH(widevine_encryption_key_source_->GetKey(
+                         EncryptionKeySource::TRACK_TYPE_SD, &encryption_key),
+                     "");
 }
 
 }  // namespace media