Adjust time for unit tests

Merge from Widevine repo of http://go/wvgerrit/96843

This CL modifies the system time used by the reference OEMCrypto so
that it recovers from a clock rollback. When the clock rolls back, it
now adjusts the current time and continues forward. This is needed
when running unit tests on some platforms that reset the clock at
the beginning of a test.

Bug: 152649427
Test: unit tests on buildbot. (No production code on Android)
Change-Id: I7edcdc0cd4e5938c9a54e745d3a0e008f9eb13ed

libwvdrmengine/oemcrypto/ref/src/oemcrypto_engine_ref.cpp

@@ -95,19 +95,22 @@ SessionContext* CryptoEngine::FindSession(SessionId sid) {
   return nullptr;
 }
 
-int64_t CryptoEngine::OnlineTime() {
+int64_t CryptoEngine::MonotonicTime() {
   // Use the monotonic clock for times that don't have to be stable across
   // device boots.
-  int64_t now = wvcdm::Clock().GetCurrentTime();
+  int64_t now =
+      wvcdm::Clock().GetCurrentTime() + offline_time_info_.rollback_offset;
   static int64_t then = now;
-  if (now < then) now = then;
+  if (now < then) {
+    offline_time_info_.rollback_offset += then - now;
+    now = then;
+  }
   then = now;
   return now;
 }
 
-int64_t CryptoEngine::RollbackCorrectedOfflineTime() {
+int64_t CryptoEngine::SystemTime() {
-  // Add any time offsets in the past to the current time.
+  const int64_t current_time = MonotonicTime();
-  int64_t current_time = OnlineTime() + offline_time_info_.rollback_offset;
   // Write time info to disk if kTimeInfoUpdateWindowInSeconds has elapsed since
   // last write.
   if (current_time - offline_time_info_.previous_time >
@@ -125,9 +128,9 @@ std::string CryptoEngine::GetUsageTimeFileFullPath() const {
   // TODO(fredgc, jfore): Address how this property is presented to the ref.
   // For now, the file path is empty.
   /*if (!wvcdm::Properties::GetDeviceFilesBasePath(wvcdm::kSecurityLevelL3,
-                                                   &file_path)) {
+    &file_path)) {
-      LOGE("RollbackCorrectedOfflineTime: Unable to get base path");
+    LOGE("Unable to get base path");
-  }*/
+    }*/
   return file_path + kStoredUsageTimeFileName;
 }
 
@@ -148,8 +151,7 @@ bool CryptoEngine::LoadOfflineTimeInfo(const std::string& file_path) {
     std::unique_ptr<wvcdm::File> file =
         file_system->Open(file_path, wvcdm::FileSystem::kReadOnly);
     if (!file) {
-      LOGE("RollbackCorrectedOfflineTime: File open failed: %s",
+      LOGE("File open failed: %s", file_path.c_str());
-           file_path.c_str());
       return false;
     }
     // Load time info from previous call.
@@ -164,7 +166,7 @@ bool CryptoEngine::LoadOfflineTimeInfo(const std::string& file_path) {
 
     // Detect offline time rollback after loading from disk.
     // Add any time offsets in the past to the current time.
-    int64_t current_time = OnlineTime() + offline_time_info_.rollback_offset;
+    int64_t current_time = MonotonicTime();
     if (offline_time_info_.previous_time > current_time) {
       // Current time is earlier than the previously saved time. Time has been
       // rolled back. Update the rollback offset.
@@ -184,7 +186,7 @@ bool CryptoEngine::SaveOfflineTimeInfo(const std::string& file_path) {
   // earlier offline rollback, the rollback offset will be updated in
   // LoadOfflineTimeInfo().  It guarantees that the current time to be saved
   // will never go back.
-  int64_t current_time = OnlineTime() + offline_time_info_.rollback_offset;
+  const int64_t current_time = MonotonicTime();
   // The new previous_time will either stay the same or move forward.
   if (current_time > offline_time_info_.previous_time)
     offline_time_info_.previous_time = current_time;
@@ -213,8 +215,7 @@ bool CryptoEngine::SaveOfflineTimeInfo(const std::string& file_path) {
   file = file_system->Open(
       file_path, wvcdm::FileSystem::kCreate | wvcdm::FileSystem::kTruncate);
   if (!file) {
-    LOGE("RollbackCorrectedOfflineTime: File open failed: %s",
+    LOGE("File open failed: %s", file_path.c_str());
-         file_path.c_str());
     return false;
   }
   file->Write(reinterpret_cast<char*>(&encrypted_buffer[0]), sizeof(TimeInfo));

libwvdrmengine/oemcrypto/ref/src/oemcrypto_engine_ref.h

@@ -104,8 +104,7 @@ class CryptoEngine {
   }
 
   // The OEMCrypto system time. Prevents time rollback.
-  // TODO(b/145836634): Combine RollbackCorrectedOfflineTime with OnlineTime().
+  int64_t SystemTime();
-  int64_t SystemTime() { return RollbackCorrectedOfflineTime(); }
 
   // Verify that this nonce does not collide with another nonce in any session.
   virtual bool NonceCollision(uint32_t nonce);
@@ -224,11 +223,8 @@ class CryptoEngine {
   }
 
  protected:
-  // System clock, measuring time in seconds.
+  // System clock, measuring time in seconds, including anti-rollback offset.
-  int64_t OnlineTime();
+  int64_t MonotonicTime();
-
-  // System clock with antirollback protection, measuring time in seconds.
-  int64_t RollbackCorrectedOfflineTime();
 
   bool LoadOfflineTimeInfo(const std::string& file_path);
   bool SaveOfflineTimeInfo(const std::string& file_path);