introduce CachingDataDecryptorFactory towards cached session keys

this commit introduces the CachingDataDecryptorFactory, which wraps
a DataDecryptorFactory but supports caching of decrypted session keys.

this change also gets rid of runtimeexception based control flow in
PgpDecryptVerify.

1 files changed, 76 insertions, 0 deletions

diff --git a/OpenKeychain/src/main/java/org/spongycastle/openpgp/operator/jcajce/CachingDataDecryptorFactory.java b/OpenKeychain/src/main/java/org/spongycastle/openpgp/operator/jcajce/CachingDataDecryptorFactory.java
new file mode 100644
index 000000000..d35f1d751
--- /dev/null
+++ b/OpenKeychain/src/main/java/org/spongycastle/openpgp/operator/jcajce/CachingDataDecryptorFactory.java
@@ -0,0 +1,76 @@
+/**
+ * Copyright (c) 2013-2014 Philipp Jakubeit, Signe Rüsch, Dominik Schürmann
+ *
+ * Licensed under the Bouncy Castle License (MIT license). See LICENSE file for details.
+ */
+
+package org.spongycastle.openpgp.operator.jcajce;
+
+import org.spongycastle.jcajce.util.NamedJcaJceHelper;
+import org.spongycastle.openpgp.PGPException;
+import org.spongycastle.openpgp.PGPPublicKeyEncryptedData;
+import org.spongycastle.openpgp.operator.PGPDataDecryptor;
+import org.spongycastle.openpgp.operator.PublicKeyDataDecryptorFactory;
+
+import java.nio.ByteBuffer;
+import java.util.Map;
+
+public class CachingDataDecryptorFactory implements PublicKeyDataDecryptorFactory
+{
+    private final PublicKeyDataDecryptorFactory mWrappedDecryptor;
+    private final Map<ByteBuffer, byte[]> mSessionKeyCache;
+
+    private OperatorHelper mOperatorHelper;
+
+    public CachingDataDecryptorFactory(String providerName,
+            final Map<ByteBuffer,byte[]> sessionKeyCache)
+    {
+        mWrappedDecryptor = null;
+        mSessionKeyCache = sessionKeyCache;
+
+        mOperatorHelper = new OperatorHelper(new NamedJcaJceHelper(providerName));
+    }
+
+    public CachingDataDecryptorFactory(PublicKeyDataDecryptorFactory wrapped,
+            final Map<ByteBuffer,byte[]> sessionKeyCache)
+    {
+        mWrappedDecryptor = wrapped;
+        mSessionKeyCache = sessionKeyCache;
+
+    }
+
+    public boolean hasCachedSessionData(PGPPublicKeyEncryptedData encData) throws PGPException {
+        ByteBuffer bi = ByteBuffer.wrap(encData.getSessionKey()[0]);
+        return mSessionKeyCache.containsKey(bi);
+    }
+
+    public Map<ByteBuffer, byte[]> getCachedSessionKeys() {
+        return mSessionKeyCache;
+    }
+
+    public boolean canDecrypt() {
+        return mWrappedDecryptor != null;
+    }
+
+    @Override
+    public byte[] recoverSessionData(int keyAlgorithm, byte[][] secKeyData) throws PGPException {
+        ByteBuffer bi = ByteBuffer.wrap(secKeyData[0]);  // encoded MPI
+        if (mSessionKeyCache.containsKey(bi)) {
+            return mSessionKeyCache.get(bi);
+        }
+
+        byte[] sessionData = mWrappedDecryptor.recoverSessionData(keyAlgorithm, secKeyData);
+        mSessionKeyCache.put(bi, sessionData);
+        return sessionData;
+    }
+
+    @Override
+    public PGPDataDecryptor createDataDecryptor(boolean withIntegrityPacket, int encAlgorithm, byte[] key)
+            throws PGPException {
+        if (mWrappedDecryptor != null) {
+            return mWrappedDecryptor.createDataDecryptor(withIntegrityPacket, encAlgorithm, key);
+        }
+        return mOperatorHelper.createDataDecryptor(withIntegrityPacket, encAlgorithm, key);
+    }
+
+}