1 files changed, 116 insertions, 0 deletions
diff --git a/OpenKeychain/src/main/java/org/bouncycastle/openpgp/operator/jcajce/SessionKeySecretKeyDecryptorBuilder.java b/OpenKeychain/src/main/java/org/bouncycastle/openpgp/operator/jcajce/SessionKeySecretKeyDecryptorBuilder.java
new file mode 100644
index 000000000..6f1b6f5ef
--- /dev/null
+++ b/OpenKeychain/src/main/java/org/bouncycastle/openpgp/operator/jcajce/SessionKeySecretKeyDecryptorBuilder.java
@@ -0,0 +1,116 @@
+/**
+ * Copyright (c) 2016 Vincent Breitmoser
+ *
+ * Licensed under the Bouncy Castle License (MIT license). See LICENSE file for details.
+ */
+
+package org.bouncycastle.openpgp.operator.jcajce;
+
+
+import java.security.InvalidAlgorithmParameterException;
+import java.security.InvalidKeyException;
+import java.security.Provider;
+
+import javax.crypto.BadPaddingException;
+import javax.crypto.Cipher;
+import javax.crypto.IllegalBlockSizeException;
+import javax.crypto.spec.IvParameterSpec;
+import org.bouncycastle.bcpg.S2K;
+import org.bouncycastle.jcajce.util.DefaultJcaJceHelper;
+import org.bouncycastle.jcajce.util.NamedJcaJceHelper;
+import org.bouncycastle.jcajce.util.ProviderJcaJceHelper;
+import org.bouncycastle.openpgp.PGPException;
+import org.bouncycastle.openpgp.operator.PBESecretKeyDecryptor;
+import org.bouncycastle.openpgp.operator.PGPDigestCalculatorProvider;
+
+
+/** This is a builder for a special PBESecretKeyDecryptor which is parametrized by a
+ * fixed session key, which is used in place of the one obtained from a passphrase.
+ */
+public class SessionKeySecretKeyDecryptorBuilder
+{
+    private OperatorHelper helper = new OperatorHelper(new DefaultJcaJceHelper());
+    private PGPDigestCalculatorProvider calculatorProvider;
+
+    private JcaPGPDigestCalculatorProviderBuilder calculatorProviderBuilder;
+
+    public SessionKeySecretKeyDecryptorBuilder()
+    {
+        this.calculatorProviderBuilder = new JcaPGPDigestCalculatorProviderBuilder();
+    }
+
+    public SessionKeySecretKeyDecryptorBuilder(PGPDigestCalculatorProvider calculatorProvider)
+    {
+        this.calculatorProvider = calculatorProvider;
+    }
+
+    public SessionKeySecretKeyDecryptorBuilder setProvider(Provider provider)
+    {
+        this.helper = new OperatorHelper(new ProviderJcaJceHelper(provider));
+
+        if (calculatorProviderBuilder != null)
+        {
+            calculatorProviderBuilder.setProvider(provider);
+        }
+
+        return this;
+    }
+
+    public SessionKeySecretKeyDecryptorBuilder setProvider(String providerName)
+    {
+        this.helper = new OperatorHelper(new NamedJcaJceHelper(providerName));
+
+        if (calculatorProviderBuilder != null)
+        {
+            calculatorProviderBuilder.setProvider(providerName);
+        }
+
+        return this;
+    }
+
+    public PBESecretKeyDecryptor build(final byte[] sessionKey)
+        throws PGPException
+    {
+        if (calculatorProvider == null)
+        {
+            calculatorProvider = calculatorProviderBuilder.build();
+        }
+
+        return new PBESecretKeyDecryptor(null, calculatorProvider)
+        {
+            @Override
+            public byte[] makeKeyFromPassPhrase(int keyAlgorithm, S2K s2k) throws PGPException {
+                return sessionKey;
+            }
+
+            public byte[] recoverKeyData(int encAlgorithm, byte[] key, byte[] iv, byte[] keyData, int keyOff, int keyLen)
+                throws PGPException
+            {
+                try
+                {
+                    Cipher c = helper.createCipher(PGPUtil.getSymmetricCipherName(encAlgorithm) + "/CFB/NoPadding");
+
+                    c.init(Cipher.DECRYPT_MODE, PGPUtil.makeSymmetricKey(encAlgorithm, key), new IvParameterSpec(iv));
+
+                    return c.doFinal(keyData, keyOff, keyLen);
+                }
+                catch (IllegalBlockSizeException e)
+                {
+                    throw new PGPException("illegal block size: " + e.getMessage(), e);
+                }
+                catch (BadPaddingException e)
+                {
+                    throw new PGPException("bad padding: " + e.getMessage(), e);
+                }
+                catch (InvalidAlgorithmParameterException e)
+                {
+                    throw new PGPException("invalid parameter: " + e.getMessage(), e);
+                }
+                catch (InvalidKeyException e)
+                {
+                    throw new PGPException("invalid key: " + e.getMessage(), e);
+                }
+            }
+        };
+    }
+}