android/media/MediaDrm.java

/*
 * Copyright (C) 2013 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.
 */

package android.media;

import android.media.MediaDrmException;
import java.lang.ref.WeakReference;
import java.util.UUID;
import java.util.HashMap;
import java.util.List;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.os.Bundle;
import android.os.Parcel;
import android.util.Log;

/**
 * MediaDrm can be used to obtain keys for decrypting protected media streams, in
 * conjunction with {@link android.media.MediaCrypto}.  The MediaDrm APIs
 * are designed to support the ISO/IEC 23001-7: Common Encryption standard, but
 * may also be used to implement other encryption schemes.
 * <p>
 * Encrypted content is prepared using an encryption server and stored in a content
 * library. The encrypted content is streamed or downloaded from the content library to
 * client devices via content servers.  Licenses to view the content are obtained from
 * a License Server.
 * <p>
 * <p><img src="../../../images/mediadrm_overview.png"
 *      alt="MediaDrm Overview diagram"
 *      border="0" /></p>
 * <p>
 * Keys are requested from the license server using a key request. The key
 * response is delivered to the client app, which provides the response to the
 * MediaDrm API.
 * <p>
 * A Provisioning server may be required to distribute device-unique credentials to
 * the devices.
 * <p>
 * Enforcing requirements related to the number of devices that may play content
 * simultaneously can be performed either through key renewal or using the secure
 * stop methods.
 * <p>
 * The following sequence diagram shows the interactions between the objects
 * involved while playing back encrypted content:
 * <p>
 * <p><img src="../../../images/mediadrm_decryption_sequence.png"
 *         alt="MediaDrm Overview diagram"
 *         border="0" /></p>
 * <p>
 * The app first constructs {@link android.media.MediaExtractor} and
 * {@link android.media.MediaCodec} objects. It accesses the DRM-scheme-identifying UUID,
 * typically from metadata in the content, and uses this UUID to construct an instance
 * of a MediaDrm object that is able to support the DRM scheme required by the content.
 * Crypto schemes are assigned 16 byte UUIDs.  The method {@link #isCryptoSchemeSupported}
 * can be used to query if a given scheme is supported on the device.
 * <p>
 * The app calls {@link #openSession} to generate a sessionId that will uniquely identify
 * the session in subsequent interactions. The app next uses the MediaDrm object to
 * obtain a key request message and send it to the license server, then provide
 * the server's response to the MediaDrm object.
 * <p>
 * Once the app has a sessionId, it can construct a MediaCrypto object from the UUID and
 * sessionId.  The MediaCrypto object is registered with the MediaCodec in the
 * {@link MediaCodec.#configure} method to enable the codec to decrypt content.
 * <p>
 * When the app has constructed {@link android.media.MediaExtractor},
 * {@link android.media.MediaCodec} and {@link android.media.MediaCrypto} objects,
 * it proceeds to pull samples from the extractor and queue them into the decoder.  For
 * encrypted content, the samples returned from the extractor remain encrypted, they
 * are only decrypted when the samples are delivered to the decoder.
 * <p>
 * <a name="Callbacks"></a>
 * <h3>Callbacks</h3>
 * <p>Applications should register for informational events in order
 * to be informed of key state updates during playback or streaming.
 * Registration for these events is done via a call to
 * {@link #setOnEventListener}. In order to receive the respective
 * callback associated with this listener, applications are required to create
 * MediaDrm objects on a thread with its own Looper running (main UI
 * thread by default has a Looper running).
 */
public final class MediaDrm {

    private final static String TAG = "MediaDrm";

    private EventHandler mEventHandler;
    private OnEventListener mOnEventListener;

    private int mNativeContext;

    /**
     * Query if the given scheme identified by its UUID is supported on
     * this device.
     * @param uuid The UUID of the crypto scheme.
     */
    public static final boolean isCryptoSchemeSupported(UUID uuid) {
        return isCryptoSchemeSupportedNative(getByteArrayFromUUID(uuid));
    }

    private static final byte[] getByteArrayFromUUID(UUID uuid) {
        long msb = uuid.getMostSignificantBits();
        long lsb = uuid.getLeastSignificantBits();

        byte[] uuidBytes = new byte[16];
        for (int i = 0; i < 8; ++i) {
            uuidBytes[i] = (byte)(msb >>> (8 * (7 - i)));
            uuidBytes[8 + i] = (byte)(lsb >>> (8 * (7 - i)));
        }

        return uuidBytes;
    }

    private static final native boolean isCryptoSchemeSupportedNative(byte[] uuid);

    /**
     * Instantiate a MediaDrm object using opaque, crypto scheme specific
     * data.
     * @param uuid The UUID of the crypto scheme.
     */
    public MediaDrm(UUID uuid) throws MediaDrmException {
        Looper looper;
        if ((looper = Looper.myLooper()) != null) {
            mEventHandler = new EventHandler(this, looper);
        } else if ((looper = Looper.getMainLooper()) != null) {
            mEventHandler = new EventHandler(this, looper);
        } else {
            mEventHandler = null;
        }

        /* Native setup requires a weak reference to our object.
         * It's easier to create it here than in C++.
         */
        native_setup(new WeakReference<MediaDrm>(this),
                     getByteArrayFromUUID(uuid));
    }

    /**
     * Register a callback to be invoked when an event occurs
     *
     * @param listener the callback that will be run
     */
    public void setOnEventListener(OnEventListener listener)
    {
        mOnEventListener = listener;
    }

    /**
     * Interface definition for a callback to be invoked when a drm event
     * occurs
     */
    public interface OnEventListener
    {
        /**
         * Called when an event occurs that requires the app to be notified
         *
         * @param md the MediaDrm object on which the event occurred
         * @param sessionId the DRM session ID on which the event occurred
         * @param event indicates the event type
         * @param extra an secondary error code
         * @param data optional byte array of data that may be associated with the event
         */
        void onEvent(MediaDrm md, byte[] sessionId, int event, int extra, byte[] data);
    }

    /**
     * This event type indicates that the app needs to request a certificate from
     * the provisioning server.  The request message data is obtained using
     * {@link #getProvisionRequest}
     */
    public static final int EVENT_PROVISION_REQUIRED = 1;

    /**
     * This event type indicates that the app needs to request keys from a license
     * server.  The request message data is obtained using {@link #getKeyRequest}.
     */
    public static final int EVENT_KEY_REQUIRED = 2;

    /**
     * This event type indicates that the licensed usage duration for keys in a session
     * has expired.  The keys are no longer valid.
     */
    public static final int EVENT_KEY_EXPIRED = 3;

    /**
     * This event may indicate some specific vendor-defined condition, see your
     * DRM provider documentation for details
     */
    public static final int EVENT_VENDOR_DEFINED = 4;

    private static final int DRM_EVENT = 200;

    private class EventHandler extends Handler
    {
        private MediaDrm mMediaDrm;

        public EventHandler(MediaDrm md, Looper looper) {
            super(looper);
            mMediaDrm = md;
        }

        @Override
        public void handleMessage(Message msg) {
            if (mMediaDrm.mNativeContext == 0) {
                Log.w(TAG, "MediaDrm went away with unhandled events");
                return;
            }
            switch(msg.what) {

            case DRM_EVENT:
                Log.i(TAG, "Drm event (" + msg.arg1 + "," + msg.arg2 + ")");

                if (mOnEventListener != null) {
                    if (msg.obj != null && msg.obj instanceof Parcel) {
                        Parcel parcel = (Parcel)msg.obj;
                        byte[] sessionId = parcel.createByteArray();
                        if (sessionId.length == 0) {
                            sessionId = null;
                        }
                        byte[] data = parcel.createByteArray();
                        if (data.length == 0) {
                            data = null;
                        }
                        mOnEventListener.onEvent(mMediaDrm, sessionId, msg.arg1, msg.arg2, data);
                    }
                }
                return;

            default:
                Log.e(TAG, "Unknown message type " + msg.what);
                return;
            }
        }
    }

    /*
     * This method is called from native code when an event occurs.  This method
     * just uses the EventHandler system to post the event back to the main app thread.
     * We use a weak reference to the original MediaPlayer object so that the native
     * code is safe from the object disappearing from underneath it.  (This is
     * the cookie passed to native_setup().)
     */
    private static void postEventFromNative(Object mediadrm_ref,
                                            int eventType, int extra, Object obj)
    {
        MediaDrm md = (MediaDrm)((WeakReference)mediadrm_ref).get();
        if (md == null) {
            return;
        }
        if (md.mEventHandler != null) {
            Message m = md.mEventHandler.obtainMessage(DRM_EVENT, eventType, extra, obj);
            md.mEventHandler.sendMessage(m);
        }
    }

    /**
     * Open a new session with the MediaDrm object.  A session ID is returned.
     */
    public native byte[] openSession();

    /**
     * Close a session on the MediaDrm object that was previously opened
     * with {@link #openSession}.
     */
    public native void closeSession(byte[] sessionId);

    /**
     * This key request type species that the keys will be for online use, they will
     * not be saved to the device for subsequent use when the device is not connected
     * to a network.
     */
    public static final int KEY_TYPE_STREAMING = 1;

    /**
     * This key request type specifies that the keys will be for offline use, they
     * will be saved to the device for use when the device is not connected to a network.
     */
    public static final int KEY_TYPE_OFFLINE = 2;

    /**
     * This key request type specifies that previously saved offline keys should be released.
     */
    public static final int KEY_TYPE_RELEASE = 3;

    /**
     * Contains the opaque data an app uses to request keys from a license server
     */
    public final static class KeyRequest {
        KeyRequest() {}

        /**
         * Get the opaque message data
         */
        public byte[] getData() { return mData; }

        /**
         * Get the default URL to use when sending the key request message to a
         * server, if known.  The app may prefer to use a different license
         * server URL from other sources.
         */
        public String getDefaultUrl() { return mDefaultUrl; }

        private byte[] mData;
        private String mDefaultUrl;
    };

    /**
     * A key request/response exchange occurs between the app and a license server
     * to obtain or release keys used to decrypt encrypted content.
     * <p>
     * getKeyRequest() is used to obtain an opaque key request byte array that is
     * delivered to the license server.  The opaque key request byte array is returned
     * in KeyRequest.data.  The recommended URL to deliver the key request to is
     * returned in KeyRequest.defaultUrl.
     * <p>
     * After the app has received the key request response from the server,
     * it should deliver to the response to the DRM engine plugin using the method
     * {@link #provideKeyResponse}.
     *
     * @param scope may be a sessionId or a keySetId, depending on the specified keyType.
     * When the keyType is KEY_TYPE_STREAMING or KEY_TYPE_OFFLINE,
     * scope should be set to the sessionId the keys will be provided to.  When the keyType
     * is KEY_TYPE_RELEASE, scope should be set to the keySetId of the keys
     * being released. Releasing keys from a device invalidates them for all sessions.
     * @param init container-specific data, its meaning is interpreted based on the
     * mime type provided in the mimeType parameter.  It could contain, for example,
     * the content ID, key ID or other data obtained from the content metadata that is
     * required in generating the key request. init may be null when keyType is
     * KEY_TYPE_RELEASE.
     * @param mimeType identifies the mime type of the content
     * @param keyType specifes the type of the request. The request may be to acquire
     * keys for streaming or offline content, or to release previously acquired
     * keys, which are identified by a keySetId.
     * @param optionalParameters are included in the key request message to
     * allow a client application to provide additional message parameters to the server.
     */
    public native KeyRequest getKeyRequest(byte[] scope, byte[] init,
                                           String mimeType, int keyType,
                                           HashMap<String, String> optionalParameters);


    /**
     * A key response is received from the license server by the app, then it is
     * provided to the DRM engine plugin using provideKeyResponse. The byte array
     * returned is a keySetId that can be used to later restore the keys to a new
     * session with the method {@link #restoreKeys}, enabling offline key use.
     *
     * @param sessionId the session ID for the DRM session
     * @param response the byte array response from the server
     */
    public native byte[] provideKeyResponse(byte[] sessionId, byte[] response);

    /**
     * Restore persisted offline keys into a new session.  keySetId identifies the
     * keys to load, obtained from a prior call to {@link #provideKeyResponse}.
     *
     * @param sessionId the session ID for the DRM session
     * @param keySetId identifies the saved key set to restore
     */
    public native void restoreKeys(byte[] sessionId, byte[] keySetId);

    /**
     * Remove the current keys from a session.
     *
     * @param sessionId the session ID for the DRM session
     */
    public native void removeKeys(byte[] sessionId);

    /**
     * Request an informative description of the key status for the session.  The status is
     * in the form of {name, value} pairs.  Since DRM license policies vary by vendor,
     * the specific status field names are determined by each DRM vendor.  Refer to your
     * DRM provider documentation for definitions of the field names for a particular
     * DRM engine plugin.
     *
     * @param sessionId the session ID for the DRM session
     */
    public native HashMap<String, String> queryKeyStatus(byte[] sessionId);

    /**
     * Contains the opaque data an app uses to request a certificate from a provisioning
     * server
     */
    public final static class ProvisionRequest {
        ProvisionRequest() {}

        /**
         * Get the opaque message data
         */
        public byte[] getData() { return mData; }

        /**
         * Get the default URL to use when sending the provision request
         * message to a server, if known. The app may prefer to use a different
         * provisioning server URL obtained from other sources.
         */
        public String getDefaultUrl() { return mDefaultUrl; }

        private byte[] mData;
        private String mDefaultUrl;
    }

    /**
     * A provision request/response exchange occurs between the app and a provisioning
     * server to retrieve a device certificate.  If provisionining is required, the
     * EVENT_PROVISION_REQUIRED event will be sent to the event handler.
     * getProvisionRequest is used to obtain the opaque provision request byte array that
     * should be delivered to the provisioning server. The provision request byte array
     * is returned in ProvisionRequest.data. The recommended URL to deliver the provision
     * request to is returned in ProvisionRequest.defaultUrl.
     */
    public native ProvisionRequest getProvisionRequest();

    /**
     * After a provision response is received by the app, it is provided to the DRM
     * engine plugin using this method.
     *
     * @param response the opaque provisioning response byte array to provide to the
     * DRM engine plugin.
     */
    public native void provideProvisionResponse(byte[] response);

    /**
     * A means of enforcing limits on the number of concurrent streams per subscriber
     * across devices is provided via SecureStop. This is achieved by securely
     * monitoring the lifetime of sessions.
     * <p>
     * Information from the server related to the current playback session is written
     * to persistent storage on the device when each MediaCrypto object is created.
     * <p>
     * In the normal case, playback will be completed, the session destroyed and the
     * Secure Stops will be queried. The app queries secure stops and forwards the
     * secure stop message to the server which verifies the signature and notifies the
     * server side database that the session destruction has been confirmed. The persisted
     * record on the client is only removed after positive confirmation that the server
     * received the message using releaseSecureStops().
     */
    public native List<byte[]> getSecureStops();


    /**
     * Process the SecureStop server response message ssRelease.  After authenticating
     * the message, remove the SecureStops identified in the response.
     *
     * @param ssRelease the server response indicating which secure stops to release
     */
    public native void releaseSecureStops(byte[] ssRelease);


    /**
     * String property name: identifies the maker of the DRM engine plugin
     */
    public static final String PROPERTY_VENDOR = "vendor";

    /**
     * String property name: identifies the version of the DRM engine plugin
     */
    public static final String PROPERTY_VERSION = "version";

    /**
     * String property name: describes the DRM engine plugin
     */
    public static final String PROPERTY_DESCRIPTION = "description";

    /**
     * String property name: a comma-separated list of cipher and mac algorithms
     * supported by CryptoSession.  The list may be empty if the DRM engine
     * plugin does not support CryptoSession operations.
     */
    public static final String PROPERTY_ALGORITHMS = "algorithms";

    /**
     * Read a DRM engine plugin String property value, given the property name string.
     * <p>
     * Standard fields names are:
     * {@link #PROPERTY_VENDOR}, {@link #PROPERTY_VERSION},
     * {@link #PROPERTY_DESCRIPTION}, {@link #PROPERTY_ALGORITHM}
     */
    public native String getPropertyString(String propertyName);


    /**
     * Byte array property name: the device unique identifier is established during
     * device provisioning and provides a means of uniquely identifying each device.
     */
    public static final String PROPERTY_DEVICE_UNIQUE_ID = "deviceUniqueId";

    /**
     * Read a DRM engine plugin byte array property value, given the property name string.
     * <p>
     * Standard fields names are {@link #PROPERTY_DEVICE_UNIQUE_ID}
     */
    public native byte[] getPropertyByteArray(String propertyName);


    /**
     * Set a DRM engine plugin String property value.
     */
    public native void setPropertyString(String propertyName, String value);

    /**
     * Set a DRM engine plugin byte array property value.
     */
    public native void setPropertyByteArray(String propertyName, byte[] value);


    private static final native void setCipherAlgorithmNative(MediaDrm drm, byte[] sessionId,
                                                              String algorithm);

    private static final native void setMacAlgorithmNative(MediaDrm drm, byte[] sessionId,
                                                           String algorithm);

    private static final native byte[] encryptNative(MediaDrm drm, byte[] sessionId,
                                                     byte[] keyId, byte[] input, byte[] iv);

    private static final native byte[] decryptNative(MediaDrm drm, byte[] sessionId,
                                                     byte[] keyId, byte[] input, byte[] iv);

    private static final native byte[] signNative(MediaDrm drm, byte[] sessionId,
                                                  byte[] keyId, byte[] message);

    private static final native boolean verifyNative(MediaDrm drm, byte[] sessionId,
                                                     byte[] keyId, byte[] message,
                                                     byte[] signature);

    /**
     * In addition to supporting decryption of DASH Common Encrypted Media, the
     * MediaDrm APIs provide the ability to securely deliver session keys from
     * an operator's session key server to a client device, based on the factory-installed
     * root of trust, and then perform encrypt, decrypt, sign and verify operations
     * with the session key on arbitrary user data.
     * <p>
     * The CryptoSession class implements generic encrypt/decrypt/sign/verify methods
     * based on the established session keys.  These keys are exchanged using the
     * getKeyRequest/provideKeyResponse methods.
     * <p>
     * Applications of this capability could include securing various types of
     * purchased or private content, such as applications, books and other media,
     * photos or media delivery protocols.
     * <p>
     * Operators can create session key servers that are functionally similar to a
     * license key server, except that instead of receiving license key requests and
     * providing encrypted content keys which are used specifically to decrypt A/V media
     * content, the session key server receives session key requests and provides
     * encrypted session keys which can be used for general purpose crypto operations.
     * <p>
     * A CryptoSession is obtained using {@link #getCryptoSession}
     */
    public final class CryptoSession {
        private MediaDrm mDrm;
        private byte[] mSessionId;

        CryptoSession(MediaDrm drm, byte[] sessionId,
                      String cipherAlgorithm, String macAlgorithm)
        {
            mSessionId = sessionId;
            mDrm = drm;
            setCipherAlgorithmNative(drm, sessionId, cipherAlgorithm);
            setMacAlgorithmNative(drm, sessionId, macAlgorithm);
        }

        /**
         * Encrypt data using the CryptoSession's cipher algorithm
         *
         * @param keyid specifies which key to use
         * @param input the data to encrypt
         * @param iv the initialization vector to use for the cipher
         */
        public byte[] encrypt(byte[] keyid, byte[] input, byte[] iv) {
            return encryptNative(mDrm, mSessionId, keyid, input, iv);
        }

        /**
         * Decrypt data using the CryptoSessions's cipher algorithm
         *
         * @param keyid specifies which key to use
         * @param input the data to encrypt
         * @param iv the initialization vector to use for the cipher
         */
        public byte[] decrypt(byte[] keyid, byte[] input, byte[] iv) {
            return decryptNative(mDrm, mSessionId, keyid, input, iv);
        }

        /**
         * Sign data using the CryptoSessions's mac algorithm.
         *
         * @param keyid specifies which key to use
         * @param message the data for which a signature is to be computed
         */
        public byte[] sign(byte[] keyid, byte[] message) {
            return signNative(mDrm, mSessionId, keyid, message);
        }

        /**
         * Verify a signature using the CryptoSessions's mac algorithm. Return true
         * if the signatures match, false if they do no.
         *
         * @param keyid specifies which key to use
         * @param message the data to verify
         * @param signature the reference signature which will be compared with the
         *        computed signature
         */
        public boolean verify(byte[] keyid, byte[] message, byte[] signature) {
            return verifyNative(mDrm, mSessionId, keyid, message, signature);
        }
    };

    /**
     * Obtain a CryptoSession object which can be used to encrypt, decrypt,
     * sign and verify messages or data using the session keys established
     * for the session using methods {@link #getKeyRequest} and
     * {@link #provideKeyResponse} using a session key server.
     *
     * @param sessionId the session ID for the session containing keys
     * to be used for encrypt, decrypt, sign and/or verify
     * @param cipherAlgorithm the algorithm to use for encryption and
     * decryption ciphers. The algorithm string conforms to JCA Standard
     * Names for Cipher Transforms and is case insensitive.  For example
     * "AES/CBC/NoPadding".
     * @param macAlgorithm the algorithm to use for sign and verify
     * The algorithm string conforms to JCA Standard Names for Mac
     * Algorithms and is case insensitive.  For example "HmacSHA256".
     * <p>
     * The list of supported algorithms for a DRM engine plugin can be obtained
     * using the method {@link #getPropertyString} with the property name
     * "algorithms".
     */
    public CryptoSession getCryptoSession(byte[] sessionId,
                                          String cipherAlgorithm,
                                          String macAlgorithm)
    {
        return new CryptoSession(this, sessionId, cipherAlgorithm, macAlgorithm);
    }

    @Override
    protected void finalize() {
        native_finalize();
    }

    public native final void release();
    private static native final void native_init();

    private native final void native_setup(Object mediadrm_this, byte[] uuid);

    private native final void native_finalize();

    static {
        System.loadLibrary("media_jni");
        native_init();
    }
}