Suppress error for removing lingering offline licenses.

[ Merge of http://go/wvgerrit/97963 ]

There are situations where an offline license file will remain on the
system after it's usage entry has been deleted.  This would result in
its key set ID being reported as present by the CDM, but any
operations acting upon it will result in an error.

The app should be able to remove the license without error, so long
as the license file exists and no other OEMCrypto operations fail.

This change introduces a new error code LICENSE_USAGE_ENTRY_MISSING,
which indicates that a license's usage entry cannot be found.

A new integration test checks that the CDM can handle the calls to
removeOfflineLicense().

Bug: 137034719
Test: Android unit and integration tests
Change-Id: Ibdbe963b7f7e3ac97b446300d8e3896cdee7abc5

libwvdrmengine/cdm/core/src/cdm_engine.cpp

@@ -169,10 +169,13 @@ CdmResponseType CdmEngine::OpenKeySetSession(
     key_set_in_use =
         release_key_sets_.find(key_set_id) != release_key_sets_.end();
   }
-  if (key_set_in_use) CloseKeySetSession(key_set_id);
+  if (key_set_in_use) {
+    LOGD("Reopening existing key session");
+    CloseKeySetSession(key_set_id);
+  }
 
   CdmSessionId session_id;
-  CdmResponseType sts =
+  const CdmResponseType sts =
       OpenSession(KEY_SYSTEM, property_set, event_listener,
                   nullptr /* forced_session_id */, &session_id);
 
@@ -1114,14 +1117,19 @@ CdmResponseType CdmEngine::RemoveOfflineLicense(
   property_set.set_security_level(
       security_level == kSecurityLevelL3 ? kLevel3 : kLevelDefault);
   DeviceFiles handle(file_system_);
+
+  if (!handle.Init(security_level)) {
+    LOGE("Cannot initialize device files: security_level = %s",
+         security_level == kSecurityLevelL3 ? "L3" : "Default");
+    return REMOVE_OFFLINE_LICENSE_ERROR_1;
+  }
+
   CdmResponseType sts = OpenKeySetSession(key_set_id, &property_set,
                                           nullptr /* event listener */);
   if (sts != NO_ERROR) {
-    if (!handle.Init(security_level)) {
-      LOGE("Cannot initialize device files");
-    }
+    LOGE("Failed to open key set session: status = %d", static_cast<int>(sts));
     handle.DeleteLicense(key_set_id);
-    return REMOVE_OFFLINE_LICENSE_ERROR_1;
+    return sts;
   }
 
   CdmSessionId session_id;
@@ -1141,6 +1149,14 @@ CdmResponseType CdmEngine::RemoveOfflineLicense(
       session_id = iter->second.first;
       sts = RemoveLicense(session_id);
     }
+  } else if (sts == LICENSE_USAGE_ENTRY_MISSING) {
+    // It is possible that the CDM is tracking a key set ID, but has
+    // removed the usage information associated with it.  In this case,
+    // it will no longer be possible to load the license for release;
+    // and the file should simply be deleted.
+    LOGW("License usage entry is missing, deleting license file");
+    handle.DeleteLicense(key_set_id);
+    sts = NO_ERROR;
   }
 
   if (sts != NO_ERROR) {

libwvdrmengine/cdm/core/src/cdm_session.cpp

@@ -282,6 +282,9 @@ CdmResponseType CdmSession::RestoreOfflineSession(const CdmKeySetId& key_set_id,
             key_response_, &provider_session_token) ||
         usage_table_header_ == nullptr) {
       provider_session_token.clear();
+    } else if (!VerifyOfflineUsageEntry()) {
+      LOGE("License usage entry is invalid, cannot restore");
+      return LICENSE_USAGE_ENTRY_MISSING;
     } else {
       CdmResponseType sts = usage_table_header_->LoadEntry(
           crypto_session_.get(), usage_entry_, usage_entry_number_);
@@ -1131,6 +1134,25 @@ void CdmSession::UpdateRequestLatencyTiming(CdmResponseType sts) {
   license_request_latency_.Clear();
 }
 
+bool CdmSession::VerifyOfflineUsageEntry() {
+  // Check that the current license is the same as the expected
+  // entry in the usage table.  It is possible that the license has
+  // been removed from the usage table but the license file remains.
+  if (usage_entry_number_ >= usage_table_header_->size()) {
+    LOGD("License usage entry does not exist: entry_number = %u, size = %zu",
+         usage_entry_number_, usage_table_header_->size());
+    return false;
+  }
+  const CdmUsageEntryInfo& usage_entry_info =
+      usage_table_header_->usage_entry_info().at(usage_entry_number_);
+  if (usage_entry_info.storage_type != kStorageLicense ||
+      usage_entry_info.key_set_id != key_set_id_) {
+    LOGD("License usage entry does not match");
+    return false;
+  }
+  return true;
+}
+
 // For testing only - takes ownership of pointers
 
 void CdmSession::set_license_parser(CdmLicense* license_parser) {