Add unit test to verify signature

Merge from widevine repo of http://go/wvgerrit/21521

On devices that use provisioning 3.0, the function
OEMCrypto_GenerateSignature will only be used for a license renewal.
This CL adds a call to OEMCrypto_GenerateSignature to the refresh key
tests.  Otherwise, there would be no coverage at all for that
function.

Change-Id: Icbd568eea3f9f256cc9b0b441f7907b316bb5b69

libwvdrmengine/oemcrypto/test/oec_session_util.cpp

@@ -385,6 +385,28 @@ void Session::ClientSignMessage(const vector<uint8_t>& data,
        &(data.front()), data.size(), &(signature->front()), &md_len);
 }
 
+// This verifies the signature computed by OEMCrypto using the client mac keys.
+// This is used when a device requests a license renewal.  It is also used for
+// a license request authenticated by a keybox.  The first use case is needed
+// for devices with a keybox or without.
+void Session::VerifyClientSignature(size_t data_length) {
+  vector<uint8_t> data(data_length);
+  for(int i=0; i < data.size(); i++) data[i] = i % 0xFF;
+  OEMCryptoResult sts;
+  size_t gen_signature_length = 0;
+  sts = OEMCrypto_GenerateSignature(session_id(), &data[0], data.size(),
+                                    NULL, &gen_signature_length);
+  ASSERT_EQ(OEMCrypto_ERROR_SHORT_BUFFER, sts);
+  ASSERT_EQ(static_cast<size_t>(32), gen_signature_length);
+  vector<uint8_t> gen_signature(gen_signature_length);
+  sts = OEMCrypto_GenerateSignature(session_id(), &data[0], data.size(),
+                                    &gen_signature[0], &gen_signature_length);
+  ASSERT_EQ(OEMCrypto_SUCCESS, sts);
+  std::vector<uint8_t> expected_signature;
+  ClientSignMessage(data, &expected_signature);
+  ASSERT_EQ(expected_signature, gen_signature);
+}
+
 void Session::FillKeyArray(const MessageData& data,
                            OEMCrypto_KeyObject* key_array) {
   for (unsigned int i = 0; i < num_keys_; i++) {

libwvdrmengine/oemcrypto/test/oec_session_util.h

@@ -148,6 +148,7 @@ class Session {
                         std::vector<uint8_t>* signature);
   void ClientSignMessage(const vector<uint8_t>& data,
                          std::vector<uint8_t>* signature);
+  void VerifyClientSignature(size_t data_length = 400);
   void FillKeyArray(const MessageData& data, OEMCrypto_KeyObject* key_array);
   void FillRefreshArray(OEMCrypto_KeyRefreshObject* key_array,
                         size_t key_count);

libwvdrmengine/oemcrypto/test/oemcrypto_test.cpp

@@ -1155,6 +1155,7 @@ TEST_P(SessionTestRefreshKeyTest, RefreshWithNonce) {
   ASSERT_NO_FATAL_FAILURE(s.LoadTestKeys("", new_mac_keys_));
   uint32_t nonce;
   s.GenerateNonce(&nonce);
+  ASSERT_NO_FATAL_FAILURE(s.VerifyClientSignature());
   ASSERT_NO_FATAL_FAILURE(s.RefreshTestKeys(
       num_keys_, wvoec_mock::kControlNonceEnabled, nonce, OEMCrypto_SUCCESS));
 }
@@ -1168,6 +1169,7 @@ TEST_P(SessionTestRefreshKeyTest, RefreshNoNonce) {
   ASSERT_NO_FATAL_FAILURE(s.LoadTestKeys("", new_mac_keys_));
   uint32_t nonce;
   s.GenerateNonce(&nonce);
+  ASSERT_NO_FATAL_FAILURE(s.VerifyClientSignature());
   ASSERT_NO_FATAL_FAILURE(
       s.RefreshTestKeys(num_keys_, 0, 0, OEMCrypto_SUCCESS));
 }
@@ -1181,6 +1183,7 @@ TEST_P(SessionTestRefreshKeyTest, RefreshOldNonce) {
   ASSERT_NO_FATAL_FAILURE(s.EncryptAndSign());
   ASSERT_NO_FATAL_FAILURE(s.LoadTestKeys("", new_mac_keys_));
   uint32_t nonce = s.get_nonce();
+  ASSERT_NO_FATAL_FAILURE(s.VerifyClientSignature());
   ASSERT_NO_FATAL_FAILURE(
       s.RefreshTestKeys(num_keys_, wvoec_mock::kControlNonceEnabled, nonce,
                         OEMCrypto_ERROR_INVALID_NONCE));
@@ -1196,6 +1199,7 @@ TEST_P(SessionTestRefreshKeyTest, RefreshBadNonce) {
   ASSERT_NO_FATAL_FAILURE(s.LoadTestKeys("", new_mac_keys_));
   uint32_t nonce;
   s.GenerateNonce(&nonce);
+  ASSERT_NO_FATAL_FAILURE(s.VerifyClientSignature());
   nonce ^= 42;
   ASSERT_NO_FATAL_FAILURE(
       s.RefreshTestKeys(num_keys_, wvoec_mock::kControlNonceEnabled, nonce,
@@ -1213,6 +1217,7 @@ TEST_P(SessionTestRefreshKeyTest, RefreshLargeBuffer) {
   ASSERT_NO_FATAL_FAILURE(s.LoadTestKeys("", new_mac_keys_));
   uint32_t nonce;
   s.GenerateNonce(&nonce);
+  ASSERT_NO_FATAL_FAILURE(s.VerifyClientSignature(kMaxMessageSize));
   ASSERT_NO_FATAL_FAILURE(s.RefreshTestKeys(
       num_keys_, wvoec_mock::kControlNonceEnabled, nonce, OEMCrypto_SUCCESS));
 }