PGPSessionKeyEncryptedData: Make Mister-Zuccherato prevention optional

pg/src/main/java/org/bouncycastle/openpgp/PGPEncryptedDataList.java

@@ -202,4 +202,20 @@ public PGPSessionKeyEncryptedData extractSessionKeyEncryptedData()
     {
         return new PGPSessionKeyEncryptedData(data);
     }
+
+    /**
+     * Create a decryption method using a {@link PGPSessionKey}.
+     * This method can be used to decrypt messages which do not contain a SKESK or PKESK packet using a session key.
+     * If <pre>enableQuickCheck</pre> is set to true, upon decryption, the 2-octet quick-check is performed
+     * to early reject wrong session-keys.
+     * NOTE: The quick check should only be enabled for symmetrically encrypted data, in order to prevent
+     * attacks via the Mister-Zuccherato oracle.
+     *
+     * @param enableQuickCheck whether to enable the 2-octet SEIPDv1 quick check.
+     * @return session key encrypted data
+     */
+    public PGPSessionKeyEncryptedData extractSessionKeyEncryptedData(boolean enableQuickCheck)
+    {
+        return new PGPSessionKeyEncryptedData(data, enableQuickCheck);
+    }
 }

pg/src/main/java/org/bouncycastle/openpgp/PGPSessionKeyEncryptedData.java

@@ -13,9 +13,17 @@
 public class PGPSessionKeyEncryptedData
     extends PGPSymmetricKeyEncryptedData
 {
+    private final boolean enableQuickCheck;
+
     PGPSessionKeyEncryptedData(InputStreamPacket encData)
+    {
+        this(encData, false);
+    }
+
+    PGPSessionKeyEncryptedData(InputStreamPacket encData, boolean enableQuickCheck)
     {
         super(encData);
+        this.enableQuickCheck = enableQuickCheck;
     }
 
     @Override
@@ -69,6 +77,6 @@ public InputStream getDataStream(
     @Override
     protected boolean isPublicKeyEncrypted()
     {
-        return true;
+        return !enableQuickCheck;
     }
 }