Streamline cast certificate loading

This CL adds special code to create a session and sign a
message with an RSA key without initializing the full session.

This is to fix:
b/16130551 Molly does not show up in CAST device list

Change-Id: I4a14b312ef67e666c7c9504fe8135c6924be4c0d

libwvdrmengine/mediadrm/src/WVGenericCryptoInterface.cpp

@@ -0,0 +1,49 @@
+//
+// Copyright 2013 Google Inc. All Rights Reserved.
+//
+
+//#define LOG_NDEBUG 0
+#define LOG_TAG "WVCdm"
+#include <utils/Log.h>
+
+#include "WVGenericCryptoInterface.h"
+
+#include "wv_cdm_constants.h"
+
+namespace wvdrm {
+
+using namespace android;
+using namespace std;
+using namespace wvcdm;
+
+OEMCryptoResult WVGenericCryptoInterface::signRSA(const uint8_t* wrapped_rsa_key,
+                                                  size_t wrapped_rsa_key_length,
+                                                  const uint8_t* message,
+                                                  size_t message_length,
+                                                  Vector<uint8_t>& signature,
+                                                  RSA_Padding_Scheme padding_scheme) {
+  OEMCrypto_SESSION session;
+  OEMCryptoResult sts = OEMCrypto_OpenSession(&session);
+  if (sts != OEMCrypto_SUCCESS) return sts;
+  sts = OEMCrypto_LoadDeviceRSAKey(session, wrapped_rsa_key,
+                                   wrapped_rsa_key_length);
+  if (sts == OEMCrypto_SUCCESS) {
+    size_t signatureSize = 0;
+    sts = OEMCrypto_GenerateRSASignature(session, message, message_length,
+                                         NULL, &signatureSize,
+                                         padding_scheme);
+    if (sts == OEMCrypto_SUCCESS) {
+      // Should be short buffer.
+      sts = OEMCrypto_ERROR_UNKNOWN_FAILURE;
+    } else if (sts == OEMCrypto_ERROR_SHORT_BUFFER) {
+      signature.resize(signatureSize);
+      sts = OEMCrypto_GenerateRSASignature(session, message, message_length,
+                                           signature.editArray(), &signatureSize,
+                                           padding_scheme);
+    }
+  }
+  OEMCrypto_CloseSession(session);
+  return sts;
+}
+
+}  // namespace wvdrm