Implement OpenSSL-Based Decryptor

Implements an object that does AES-CTR-128 by invoking OpenSSL.

Change-Id: I8457899ec8b69bd8f0d727029985c9580911cf99

1 files changed, 67 insertions, 0 deletions

diff --git a/drm/mediadrm/plugins/clearkey/AesCtrDecryptor.cpp b/drm/mediadrm/plugins/clearkey/AesCtrDecryptor.cpp
new file mode 100644
index 0000000..01f8d65
--- /dev/null
+++ b/drm/mediadrm/plugins/clearkey/AesCtrDecryptor.cpp
@@ -0,0 +1,67 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+//#define LOG_NDEBUG 0
+#define LOG_TAG "ClearKeyCryptoPlugin"
+#include <utils/Log.h>
+
+#include <openssl/aes.h>
+
+#include "AesCtrDecryptor.h"
+
+namespace clearkeydrm {
+
+static const size_t kBlockBitCount = kBlockSize * 8;
+
+android::status_t AesCtrDecryptor::decrypt(const android::Vector<uint8_t>& key,
+        const Iv iv, const uint8_t* source,
+        uint8_t* destination,
+        const SubSample* subSamples,
+        size_t numSubSamples,
+        size_t* bytesDecryptedOut) {
+    uint32_t blockOffset = 0;
+    uint8_t previousEncryptedCounter[kBlockSize];
+    memset(previousEncryptedCounter, 0, kBlockSize);
+
+    size_t offset = 0;
+    AES_KEY opensslKey;
+    AES_set_encrypt_key(key.array(), kBlockBitCount, &opensslKey);
+    Iv opensslIv;
+    memcpy(opensslIv, iv, sizeof(opensslIv));
+
+    for (size_t i = 0; i < numSubSamples; ++i) {
+        const SubSample& subSample = subSamples[i];
+
+        if (subSample.mNumBytesOfClearData > 0) {
+            memcpy(destination + offset, source + offset,
+                    subSample.mNumBytesOfClearData);
+            offset += subSample.mNumBytesOfClearData;
+        }
+
+        if (subSample.mNumBytesOfEncryptedData > 0) {
+            AES_ctr128_encrypt(source + offset, destination + offset,
+                    subSample.mNumBytesOfEncryptedData, &opensslKey,
+                    opensslIv, previousEncryptedCounter,
+                    &blockOffset);
+            offset += subSample.mNumBytesOfEncryptedData;
+        }
+    }
+
+    *bytesDecryptedOut = offset;
+    return android::OK;
+}
+
+} // namespace clearkeydrm