Extract insecure Cipher factory

Bazel runs ErrorProne by default and ErrorProne rightly complains that
allowing the user to specify any Cipher can lead to insecure code
(in particular, getCipher("AES") operates in ECB mode). Unfortunately
this is required to support existing repositories insecurely stored
on S3.

Extract the insecure factory code to its own class so this can be built
as a java_library() with this check disabled.

Change-Id: I34f381965bdaa25d5aa8ebf6d8d5271b238334e0

org.eclipse.jgit/src/org/eclipse/jgit/transport/InsecureCipherFactory.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright (C) 2016, Google Inc.
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package org.eclipse.jgit.transport;
+
+import java.security.NoSuchAlgorithmException;
+
+import javax.crypto.Cipher;
+import javax.crypto.NoSuchPaddingException;
+
+/**
+ * <b>DO NOT USE</b> Factory to create any cipher.
+ * <p>
+ * This is a hack for {@link WalkEncryption} to create any cipher configured by
+ * the end-user. Using this class allows JGit to violate ErrorProne's security
+ * recommendations (<a
+ * href="http://errorprone.info/bugpattern/InsecureCryptoUsage"
+ * >InsecureCryptoUsage</a>), which is not secure.
+ */
+class InsecureCipherFactory {
+	static Cipher create(String algo)
+			throws NoSuchAlgorithmException, NoSuchPaddingException {
+		return Cipher.getInstance(algo);
+	}
+}

org.eclipse.jgit/src/org/eclipse/jgit/transport/WalkEncryption.java

@@ -188,7 +188,7 @@ abstract class WalkEncryption {
 			cryptoAlg = algo;
 
 			// Verify if cipher is present.
-			Cipher cipher = Cipher.getInstance(cryptoAlg);
+			Cipher cipher = InsecureCipherFactory.create(cryptoAlg);
 
 			// Standard names are not case-sensitive.
 			// http://docs.oracle.com/javase/8/docs/technotes/guides/security/StandardNames.html
@@ -240,7 +240,7 @@ abstract class WalkEncryption {
 		@Override
 		OutputStream encrypt(final OutputStream os) throws IOException {
 			try {
-				final Cipher cipher = Cipher.getInstance(cryptoAlg);
+				final Cipher cipher = InsecureCipherFactory.create(cryptoAlg);
 				cipher.init(Cipher.ENCRYPT_MODE, secretKey, paramSpec);
 				return new CipherOutputStream(os, cipher);
 			} catch (GeneralSecurityException e) {
@@ -251,7 +251,7 @@ abstract class WalkEncryption {
 		@Override
 		InputStream decrypt(final InputStream in) throws IOException {
 			try {
-				final Cipher cipher = Cipher.getInstance(cryptoAlg);
+				final Cipher cipher = InsecureCipherFactory.create(cryptoAlg);
 				cipher.init(Cipher.DECRYPT_MODE, secretKey, paramSpec);
 				return new CipherInputStream(in, cipher);
 			} catch (GeneralSecurityException e) {
@@ -342,7 +342,7 @@ abstract class WalkEncryption {
 			String keySalt = props.getProperty(profile + X_KEY_SALT, DEFAULT_KEY_SALT);
 
 			// Verify if cipher is present.
-			Cipher cipher = Cipher.getInstance(cipherAlgo);
+			Cipher cipher = InsecureCipherFactory.create(cipherAlgo);
 
 			// Verify if key factory is present.
 			SecretKeyFactory factory = SecretKeyFactory.getInstance(keyAlgo);
@@ -400,7 +400,7 @@ abstract class WalkEncryption {
 		@Override
 		OutputStream encrypt(OutputStream output) throws IOException {
 			try {
-				Cipher cipher = Cipher.getInstance(cipherAlgo);
+				Cipher cipher = InsecureCipherFactory.create(cipherAlgo);
 				cipher.init(Cipher.ENCRYPT_MODE, secretKey);
 				AlgorithmParameters params = cipher.getParameters();
 				if (params == null) {
@@ -457,7 +457,7 @@ abstract class WalkEncryption {
 						JGitText.get().unsupportedEncryptionVersion, vers));
 			}
 			try {
-				decryptCipher = Cipher.getInstance(cipherAlgo);
+				decryptCipher = InsecureCipherFactory.create(cipherAlgo);
 				if (cont.isEmpty()) {
 					decryptCipher.init(Cipher.DECRYPT_MODE, secretKey);
 				} else {