Adding JGitV1 and JGitV2 Walk Encryption

Building on top of https://git.eclipse.org/r/#/c/56391/

Here we preserve compatibility with JetS3t
and add 2 new native JGit encryption implementations.

For reference, see connection configuration files:
* Version 0: jgit-s3-connection-v-0.properties
* Version 1: jgit-s3-connection-v-1.properties
* Version 2: jgit-s3-connection-v-2.properties

Change-Id: I713290bcacbe92d88e5ef28ce137de73dd1abe2f
Signed-off-by: Andrei Pozolotin <andrei.pozolotin@gmail.com>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

6 files changed, 694 insertions, 76 deletions

diff --git a/org.eclipse.jgit.test/tst-rsrc/jgit-s3-connection-v-0.properties b/org.eclipse.jgit.test/tst-rsrc/jgit-s3-connection-v-0.properties
new file mode 100644
index 0000000000..2402a4985a
--- /dev/null
+++ b/org.eclipse.jgit.test/tst-rsrc/jgit-s3-connection-v-0.properties
@@ -0,0 +1,11 @@
+#
+# Sample Amazon S3 connection configuration file, Version 0.
+# Version 0 (or lack of version) will produce JetS3tV2 compatible encryption.
+# JetS3tV2 supports only PBE algorithms, with partially compromised AES mode.
+#
+
+accesskey = AKIAIYWXB4ETREBRM123
+secretkey = ozCuIsqxsARoPe3FFyv3F/jiMSc3Yqay7B9UF234
+
+crypto.algorithm = PBEWithMD5AndDES
+password = secret
diff --git a/org.eclipse.jgit.test/tst-rsrc/jgit-s3-connection-v-1.properties b/org.eclipse.jgit.test/tst-rsrc/jgit-s3-connection-v-1.properties
new file mode 100644
index 0000000000..d0d16118e9
--- /dev/null
+++ b/org.eclipse.jgit.test/tst-rsrc/jgit-s3-connection-v-1.properties
@@ -0,0 +1,14 @@
+#
+# Sample Amazon S3 connection configuration file, Version 1.
+# Version 1 will produce JGitV1 compatible encryption.
+# It is JetS3tV2-like mode with proper AES support.
+# JGitV1 uses hard coded encryption parameters.
+# JGitV1 supports only PBE algorithms.
+#
+
+accesskey = AKIAIYWXB4ETREBRM123
+secretkey = ozCuIsqxsARoPe3FFyv3F/jiMSc3Yqay7B9UF234
+
+crypto.algorithm = PBEWithHmacSHA1AndAES_128
+crypto.version = 1
+password = secret
diff --git a/org.eclipse.jgit.test/tst-rsrc/jgit-s3-connection-v-2.properties b/org.eclipse.jgit.test/tst-rsrc/jgit-s3-connection-v-2.properties
new file mode 100644
index 0000000000..731b3247d2
--- /dev/null
+++ b/org.eclipse.jgit.test/tst-rsrc/jgit-s3-connection-v-2.properties
@@ -0,0 +1,48 @@
+#
+# Sample Amazon S3 connection configuration file, Version 2.
+# Version 2 will produce JGitV2 compatible encryption.
+# JGitV2 introduces more flexible control over cipher and key factory parameters.
+# JGitV2 hides actual cipher/key algorithms inside the encryption profile.
+# JGitV2 does not use any hard coded encryption parameters.
+# JGitV2 supports both PBE and Non-PBE algorithms.
+
+accesskey = AKIAIYWXB4ETREBRM123
+secretkey = ozCuIsqxsARoPe3FFyv3F/jiMSc3Yqay7B9UF234
+
+# In Version 2 "crypto.algorithm" is a reference to the encryption "profile".
+crypto.algorithm = custom
+crypto.version = 2
+password = secret
+
+#
+# Encryption profile is a collection of related properties,
+# all having common property root name, or prefix:
+#
+# Cipher algorithm.
+custom.algo = AES/CBC/PKCS5Padding
+# Key factory algorithm.
+custom.key.algo = PBKDF2WithHmacSHA512
+# Key size, bits.
+custom.key.size = 256
+# Number of key generation iterations.
+custom.key.iter = 50000
+# Salt used in key generation (hex value, white space OK).
+custom.key.salt = e2 55 89 67 8e 8d e8 4c
+
+# Same file can store multiple profiles.
+# Only one profile can be active at a time.
+# Active profile is selected via "crypto.algorithm"
+
+#
+# Here is how to create V1 encryption in V2 format:
+#
+# Cipher algorithm.
+legacy.algo = PBEWithHmacSHA1AndAES_128
+# Key factory algorithm.
+legacy.key.algo = PBEWithHmacSHA1AndAES_128
+# Key size, bits.
+legacy.key.size = 32
+# Number of key generation iterations.
+legacy.key.iter = 5000
+# Salt used in key generation (hex value, white space OK).
+legacy.key.salt = A40BC834D695F313
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/transport/WalkEncryptionTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/transport/WalkEncryptionTest.java
index f2701cb41f..042d7ba78b 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/transport/WalkEncryptionTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/transport/WalkEncryptionTest.java
@@ -73,6 +73,7 @@ import java.util.Set;
 import java.util.TreeSet;
 import java.util.UUID;
 
+import javax.crypto.Cipher;
 import javax.crypto.SecretKeyFactory;
 
 import org.apache.log4j.Logger;
@@ -108,8 +109,10 @@ import static org.eclipse.jgit.transport.WalkEncryptionTest.Util.*;
  */
 @RunWith(Suite.class)
 @Suite.SuiteClasses({ //
+		WalkEncryptionTest.Required.class, //
 		WalkEncryptionTest.MinimalSet.class, //
 		WalkEncryptionTest.TestablePBE.class, //
+		WalkEncryptionTest.TestableTransformation.class, //
 })
 public class WalkEncryptionTest {
 
@@ -417,7 +420,12 @@ public class WalkEncryptionTest {
 		// https://www.bouncycastle.org/specifications.html
 		// https://docs.oracle.com/javase/8/docs/technotes/guides/security/SunProviders.html
 		static List<String> cryptoCipherListPBE() {
-			return cryptoCipherList("(PBE).*(WITH).+(AND).+");
+			return cryptoCipherList(WalkEncryption.Vals.REGEX_PBE);
+		}
+
+		// TODO returns inconsistent list.
+		static List<String> cryptoCipherListTrans() {
+			return cryptoCipherList(WalkEncryption.Vals.REGEX_TRANS);
 		}
 
 		static String securityProviderName(String algorithm) throws Exception {
@@ -438,25 +446,6 @@ public class WalkEncryptionTest {
 		}
 
 		/**
-		 * Verify if any security provider published the algorithm.
-		 *
-		 * @param algorithm
-		 * @return result
-		 */
-		static boolean isAlgorithmPresent(String algorithm) {
-			Set<String> cipherSet = Security.getAlgorithms("Cipher");
-			for (String source : cipherSet) {
-				// Standard names are not case-sensitive.
-				// http://docs.oracle.com/javase/8/docs/technotes/guides/security/StandardNames.html
-				String target = algorithm.toUpperCase();
-				if (source.equalsIgnoreCase(target)) {
-					return true;
-				}
-			}
-			return false;
-		}
-
-		/**
 		 * Stream copy.
 		 *
 		 * @param from
@@ -549,6 +538,51 @@ public class WalkEncryptionTest {
 			return System.getenv("HUDSON_HOME") != null;
 		}
 
+		/**
+		 * Setup JCE security policy restrictions. Can remove restrictions when
+		 * restrictions are present, but can not impose them when restrictions
+		 * are missing.
+		 *
+		 * @param restrictedOn
+		 */
+		// http://www.docjar.com/html/api/javax/crypto/JceSecurity.java.html
+		static void policySetup(boolean restrictedOn) {
+			try {
+				java.lang.reflect.Field isRestricted = Class
+						.forName("javax.crypto.JceSecurity")
+						.getDeclaredField("isRestricted");
+				isRestricted.setAccessible(true);
+				isRestricted.set(null, new Boolean(restrictedOn));
+			} catch (Throwable e) {
+				logger.info(
+						"Could not setup JCE security policy restrictions.");
+			}
+		}
+
+		static void reportPolicy() {
+			try {
+				java.lang.reflect.Field isRestricted = Class
+						.forName("javax.crypto.JceSecurity")
+						.getDeclaredField("isRestricted");
+				isRestricted.setAccessible(true);
+				logger.info("JCE security policy restricted="
+						+ isRestricted.get(null));
+			} catch (Throwable e) {
+				logger.info(
+						"Could not report JCE security policy restrictions.");
+			}
+		}
+
+		static List<Object[]> product(List<String> one, List<String> two) {
+			List<Object[]> result = new ArrayList<Object[]>();
+			for (String s1 : one) {
+				for (String s2 : two) {
+					result.add(new Object[] { s1, s2 });
+				}
+			}
+			return result;
+		}
+
 	}
 
 	/**
@@ -605,6 +639,20 @@ public class WalkEncryptionTest {
 		}
 
 		/**
+		 * Generate JGIT S3 connection configuration file.
+		 *
+		 * @param source
+		 * @throws Exception
+		 */
+		static void configCreate(Properties source) throws Exception {
+			Properties target = Props.discover();
+			target.putAll(source);
+			PrintWriter writer = new PrintWriter(JGIT_CONF_FILE);
+			target.store(writer, "JGIT S3 connection configuration file.");
+			writer.close();
+		}
+
+		/**
 		 * Remove JGIT connection configuration file.
 		 *
 		 * @throws Exception
@@ -677,6 +725,55 @@ public class WalkEncryptionTest {
 		}
 
 		/**
+		 * Verify if any security provider published the algorithm.
+		 *
+		 * @param algorithm
+		 * @return result
+		 */
+		static boolean isAlgorithmPresent(String algorithm) {
+			Set<String> cipherSet = Security.getAlgorithms("Cipher");
+			for (String source : cipherSet) {
+				// Standard names are not case-sensitive.
+				// http://docs.oracle.com/javase/8/docs/technotes/guides/security/StandardNames.html
+				String target = algorithm.toUpperCase();
+				if (source.equalsIgnoreCase(target)) {
+					return true;
+				}
+			}
+			return false;
+		}
+
+		static boolean isAlgorithmPresent(Properties props) {
+			String profile = props.getProperty(AmazonS3.Keys.CRYPTO_ALG);
+			String version = props.getProperty(AmazonS3.Keys.CRYPTO_VER,
+					WalkEncryption.Vals.DEFAULT_VERS);
+			String crytoAlgo;
+			String keyAlgo;
+			switch (version) {
+			case WalkEncryption.Vals.DEFAULT_VERS:
+			case WalkEncryption.JGitV1.VERSION:
+				crytoAlgo = profile;
+				keyAlgo = profile;
+				break;
+			case WalkEncryption.JGitV2.VERSION:
+				crytoAlgo = props
+						.getProperty(profile + WalkEncryption.Keys.X_ALGO);
+				keyAlgo = props
+						.getProperty(profile + WalkEncryption.Keys.X_KEY_ALGO);
+				break;
+			default:
+				return false;
+			}
+			try {
+				Cipher.getInstance(crytoAlgo);
+				SecretKeyFactory.getInstance(keyAlgo);
+				return true;
+			} catch (Throwable e) {
+				return false;
+			}
+		}
+
+		/**
 		 * Verify if JRE security policy allows the algorithm.
 		 *
 		 * @param algorithm
@@ -684,7 +781,7 @@ public class WalkEncryptionTest {
 		 */
 		static boolean isAlgorithmAllowed(String algorithm) {
 			try {
-				WalkEncryption crypto = new WalkEncryption.ObjectEncryptionJetS3tV2(
+				WalkEncryption crypto = new WalkEncryption.JetS3tV2(
 						algorithm, JGIT_PASS);
 				verifyCrypto(crypto);
 				return true;
@@ -695,6 +792,15 @@ public class WalkEncryptionTest {
 			}
 		}
 
+		static boolean isAlgorithmAllowed(Properties props) {
+			try {
+				WalkEncryption.instance(props);
+				return true;
+			} catch (GeneralSecurityException e) {
+				return false;
+			}
+		}
+
 		/**
 		 * Verify round trip encryption.
 		 *
@@ -736,6 +842,10 @@ public class WalkEncryptionTest {
 					&& isAlgorithmAllowed(algorithm);
 		}
 
+		static boolean isAlgorithmTestable(Properties props) {
+			return isAlgorithmPresent(props) && isAlgorithmAllowed(props);
+		}
+
 		/**
 		 * Log algorithm, provider, testability.
 		 *
@@ -756,6 +866,26 @@ public class WalkEncryptionTest {
 			}
 		}
 
+		static void reportAlgorithmStatus(Properties props) throws Exception {
+			final boolean present = isAlgorithmPresent(props);
+			final boolean allowed = present && isAlgorithmAllowed(props);
+
+			String profile = props.getProperty(AmazonS3.Keys.CRYPTO_ALG);
+			String version = props.getProperty(AmazonS3.Keys.CRYPTO_VER);
+
+			StringBuilder status = new StringBuilder();
+			status.append(" Version: " + version);
+			status.append(" Profile: " + profile);
+			status.append(" Present: " + present);
+			status.append(" Allowed: " + allowed);
+
+			if (allowed) {
+				logger.info("Testing " + status);
+			} else {
+				logger.warn("Missing " + status);
+			}
+		}
+
 		/**
 		 * Verify if we can perform remote tests.
 		 *
@@ -846,6 +976,7 @@ public class WalkEncryptionTest {
 		public static void initialize() throws Exception {
 			Transport.register(TransportAmazonS3.PROTO_S3);
 			proxySetup();
+			reportPolicy();
 			reportLongTests();
 			reportPublicAddress();
 			reportTestConfigPresent();
@@ -879,26 +1010,26 @@ public class WalkEncryptionTest {
 		/**
 		 * Optional encrypted amazon remote JGIT life cycle test.
 		 *
-		 * @param algorithm
+		 * @param props
 		 * @throws Exception
 		 */
-		void cryptoTestIfCan(String algorithm) throws Exception {
-			reportAlgorithmStatus(algorithm);
+		void cryptoTestIfCan(Properties props) throws Exception {
+			reportAlgorithmStatus(props);
 			assumeTrue(isTestConfigPresent());
-			assumeTrue(isAlgorithmTestable(algorithm));
-			cryptoTest(algorithm);
+			assumeTrue(isAlgorithmTestable(props));
+			cryptoTest(props);
 		}
 
 		/**
 		 * Required encrypted amazon remote JGIT life cycle test.
 		 *
-		 * @param algorithm
+		 * @param props
 		 * @throws Exception
 		 */
-		void cryptoTest(String algorithm) throws Exception {
+		void cryptoTest(Properties props) throws Exception {
 
 			remoteDelete();
-			configCreate(algorithm);
+			configCreate(props);
 			folderDelete(JGIT_LOCAL_DIR);
 
 			String uri = amazonURI();
@@ -990,10 +1121,10 @@ public class WalkEncryptionTest {
 	}
 
 	/**
-	 * Test minimal set of algorithms.
+	 * Verify prerequisites.
 	 */
 	@FixMethodOrder(MethodSorters.NAME_ASCENDING)
-	public static class MinimalSet extends Base {
+	public static class Required extends Base {
 
 		@Test
 		public void test_A1_ValidURI() throws Exception {
@@ -1005,22 +1136,72 @@ public class WalkEncryptionTest {
 		@Test(expected = Exception.class)
 		public void test_A2_CryptoError() throws Exception {
 			assumeTrue(isTestConfigPresent());
-			cryptoTest(ALGO_ERROR);
+			Properties props = new Properties();
+			props.put(AmazonS3.Keys.CRYPTO_ALG, ALGO_ERROR);
+			props.put(AmazonS3.Keys.PASSWORD, JGIT_PASS);
+			cryptoTest(props);
+		}
+
+	}
+
+	/**
+	 * Test minimal set of algorithms.
+	 */
+	@FixMethodOrder(MethodSorters.NAME_ASCENDING)
+	public static class MinimalSet extends Base {
+
+		@Test
+		public void test_V0_Java7_JET() throws Exception {
+			assumeTrue(isTestConfigPresent());
+			Properties props = new Properties();
+			props.put(AmazonS3.Keys.CRYPTO_ALG, ALGO_JETS3T);
+			// Do not set version.
+			props.put(AmazonS3.Keys.PASSWORD, JGIT_PASS);
+			cryptoTestIfCan(props);
 		}
 
 		@Test
-		public void test_A3_CryptoJetS3tDefault() throws Exception {
-			cryptoTestIfCan(ALGO_JETS3T);
+		public void test_V1_Java7_GIT() throws Exception {
+			assumeTrue(isTestConfigPresent());
+			Properties props = new Properties();
+			props.put(AmazonS3.Keys.CRYPTO_ALG, ALGO_JETS3T);
+			props.put(AmazonS3.Keys.CRYPTO_VER, "1");
+			props.put(AmazonS3.Keys.PASSWORD, JGIT_PASS);
+			cryptoTestIfCan(props);
 		}
 
 		@Test
-		public void test_A4_CryptoMinimalAES() throws Exception {
-			cryptoTestIfCan(ALGO_MINIMAL_AES);
+		public void test_V2_Java7_AES() throws Exception {
+			assumeTrue(isTestConfigPresent());
+			// String profile = "default";
+			String profile = "AES/CBC/PKCS5Padding+PBKDF2WithHmacSHA1";
+			Properties props = new Properties();
+			props.put(AmazonS3.Keys.CRYPTO_ALG, profile);
+			props.put(AmazonS3.Keys.CRYPTO_VER, "2");
+			props.put(AmazonS3.Keys.PASSWORD, JGIT_PASS);
+			props.put(profile + WalkEncryption.Keys.X_ALGO, "AES/CBC/PKCS5Padding");
+			props.put(profile + WalkEncryption.Keys.X_KEY_ALGO, "PBKDF2WithHmacSHA1");
+			props.put(profile + WalkEncryption.Keys.X_KEY_SIZE, "128");
+			props.put(profile + WalkEncryption.Keys.X_KEY_ITER, "10000");
+			props.put(profile + WalkEncryption.Keys.X_KEY_SALT, "e2 55 89 67 8e 8d e8 4c");
+			cryptoTestIfCan(props);
 		}
 
 		@Test
-		public void test_A5_CryptoBouncyCastleCBC() throws Exception {
-			cryptoTestIfCan(ALGO_BOUNCY_CASTLE_CBC);
+		public void test_V2_Java8_PBE_AES() throws Exception {
+			assumeTrue(isTestConfigPresent());
+			String profile = "PBEWithHmacSHA512AndAES_256";
+			Properties props = new Properties();
+			props.put(AmazonS3.Keys.CRYPTO_ALG, profile);
+			props.put(AmazonS3.Keys.CRYPTO_VER, "2");
+			props.put(AmazonS3.Keys.PASSWORD, JGIT_PASS);
+			props.put(profile + WalkEncryption.Keys.X_ALGO, "PBEWithHmacSHA512AndAES_256");
+			props.put(profile + WalkEncryption.Keys.X_KEY_ALGO, "PBEWithHmacSHA512AndAES_256");
+			props.put(profile + WalkEncryption.Keys.X_KEY_SIZE, "256");
+			props.put(profile + WalkEncryption.Keys.X_KEY_ITER, "10000");
+			props.put(profile + WalkEncryption.Keys.X_KEY_SALT, "e2 55 89 67 8e 8d e8 4c");
+			policySetup(false);
+			cryptoTestIfCan(props);
 		}
 
 	}
@@ -1033,26 +1214,79 @@ public class WalkEncryptionTest {
 	@FixMethodOrder(MethodSorters.NAME_ASCENDING)
 	public static class TestablePBE extends Base {
 
-		@Parameters(name = "Algorithm: {0}")
-		public static Collection algorimthmList() {
-			List<String> source = cryptoCipherListPBE();
-			List<Object[]> target = new ArrayList<Object[]>();
-			for (String name : source) {
-				target.add(new Object[] { name });
-			}
-			return target;
+		@Parameters(name = "Profile: {0}   Version: {1}")
+		public static Collection<Object[]> argsList() {
+			List<String> algorithmList = new ArrayList<String>();
+			algorithmList.addAll(cryptoCipherListPBE());
+
+			List<String> versionList = new ArrayList<String>();
+			versionList.add("0");
+			versionList.add("1");
+
+			return product(algorithmList, versionList);
+		}
+
+		final String profile;
+
+		final String version;
+
+		final String password = JGIT_PASS;
+
+		public TestablePBE(String profile, String version) {
+			this.profile = profile;
+			this.version = version;
+		}
+
+		@Test
+		public void testCrypto() throws Exception {
+			assumeTrue(permitLongTests());
+			Properties props = new Properties();
+			props.put(AmazonS3.Keys.CRYPTO_ALG, profile);
+			props.put(AmazonS3.Keys.CRYPTO_VER, version);
+			props.put(AmazonS3.Keys.PASSWORD, password);
+			cryptoTestIfCan(props);
+		}
+
+	}
+
+	/**
+	 * Test all present and allowed transformation algorithms.
+	 */
+	// https://github.com/junit-team/junit/wiki/Parameterized-tests
+	@RunWith(Parameterized.class)
+	@FixMethodOrder(MethodSorters.NAME_ASCENDING)
+	public static class TestableTransformation extends Base {
+
+		@Parameters(name = "Profile: {0}   Version: {1}")
+		public static Collection<Object[]> argsList() {
+			List<String> algorithmList = new ArrayList<String>();
+			algorithmList.addAll(cryptoCipherListTrans());
+
+			List<String> versionList = new ArrayList<String>();
+			versionList.add("1");
+
+			return product(algorithmList, versionList);
 		}
 
-		final String algorithm;
+		final String profile;
+
+		final String version;
 
-		public TestablePBE(String algorithm) {
-			this.algorithm = algorithm;
+		final String password = JGIT_PASS;
+
+		public TestableTransformation(String profile, String version) {
+			this.profile = profile;
+			this.version = version;
 		}
 
-		@Test // Can take long time, needs activation.
-		public void test_B1_Crypto() throws Exception {
+		@Test
+		public void testCrypto() throws Exception {
 			assumeTrue(permitLongTests());
-			cryptoTestIfCan(algorithm);
+			Properties props = new Properties();
+			props.put(AmazonS3.Keys.CRYPTO_ALG, profile);
+			props.put(AmazonS3.Keys.CRYPTO_VER, version);
+			props.put(AmazonS3.Keys.PASSWORD, password);
+			cryptoTestIfCan(props);
 		}
 
 	}
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/transport/AmazonS3.java b/org.eclipse.jgit/src/org/eclipse/jgit/transport/AmazonS3.java
index e55066a8bb..0c8ee5d4b6 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/transport/AmazonS3.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/transport/AmazonS3.java
@@ -256,15 +256,7 @@ public class AmazonS3 {
 			throw new IllegalArgumentException("Invalid acl: " + pacl); //$NON-NLS-1$
 
 		try {
-			final String cPas = props.getProperty(Keys.PASSWORD);
-			if (cPas != null) {
-				String cAlg = props.getProperty(Keys.CRYPTO_ALG);
-				if (cAlg == null)
-					cAlg = WalkEncryption.ObjectEncryptionJetS3tV2.JETS3T_ALGORITHM;
-				encryption = new WalkEncryption.ObjectEncryptionJetS3tV2(cAlg, cPas);
-			} else {
-				encryption = WalkEncryption.NONE;
-			}
+			encryption = WalkEncryption.instance(props);
 		} catch (GeneralSecurityException e) {
 			throw new IllegalArgumentException(JGitText.get().invalidEncryption, e);
 		}
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/transport/WalkEncryption.java b/org.eclipse.jgit/src/org/eclipse/jgit/transport/WalkEncryption.java
index e93a2af3ea..fe03bdc867 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/transport/WalkEncryption.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/transport/WalkEncryption.java
@@ -47,9 +47,14 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.net.HttpURLConnection;
+import java.security.AlgorithmParameters;
 import java.security.GeneralSecurityException;
 import java.security.spec.AlgorithmParameterSpec;
+import java.security.spec.KeySpec;
 import java.text.MessageFormat;
+import java.util.Properties;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 
 import javax.crypto.Cipher;
 import javax.crypto.CipherInputStream;
@@ -59,8 +64,11 @@ import javax.crypto.SecretKeyFactory;
 import javax.crypto.spec.IvParameterSpec;
 import javax.crypto.spec.PBEKeySpec;
 import javax.crypto.spec.PBEParameterSpec;
+import javax.crypto.spec.SecretKeySpec;
+import javax.xml.bind.DatatypeConverter;
 
 import org.eclipse.jgit.internal.JGitText;
+import org.eclipse.jgit.util.Base64;
 
 abstract class WalkEncryption {
 	static final WalkEncryption NONE = new NoEncryption();
@@ -69,13 +77,18 @@ abstract class WalkEncryption {
 
 	static final String JETS3T_CRYPTO_ALG = "jets3t-crypto-alg"; //$NON-NLS-1$
 
-	abstract OutputStream encrypt(OutputStream os) throws IOException;
+	// Note: encrypt -> request state machine, step 1.
+	abstract OutputStream encrypt(OutputStream output) throws IOException;
 
-	abstract InputStream decrypt(InputStream in) throws IOException;
+	// Note: encrypt -> request state machine, step 2.
+	abstract void request(HttpURLConnection conn, String prefix) throws IOException;
 
-	abstract void request(HttpURLConnection u, String prefix);
+	// Note: validate -> decrypt state machine, step 1.
+	abstract void validate(HttpURLConnection conn, String prefix) throws IOException;
+
+	// Note: validate -> decrypt state machine, step 2.
+	abstract InputStream decrypt(InputStream input) throws IOException;
 
-	abstract void validate(HttpURLConnection u, String prefix) throws IOException;
 
 	// TODO mixed ciphers
 	// consider permitting mixed ciphers to facilitate algorithm migration
@@ -173,17 +186,17 @@ abstract class WalkEncryption {
 	 * <li>any AES based algorithms such as "PBE...With...And...AES" will not
 	 * work, since they need proper IV setup
 	 */
-	static class ObjectEncryptionJetS3tV2 extends WalkEncryption {
+	static class JetS3tV2 extends WalkEncryption {
 
-		static final String JETS3T_VERSION = "2"; //$NON-NLS-1$
+		static final String VERSION = "2"; //$NON-NLS-1$
 
-		static final String JETS3T_ALGORITHM = "PBEWithMD5AndDES"; //$NON-NLS-1$
+		static final String ALGORITHM = "PBEWithMD5AndDES"; //$NON-NLS-1$
 
-		static final int JETS3T_ITERATIONS = 5000;
+		static final int ITERATIONS = 5000;
 
-		static final int JETS3T_KEY_SIZE = 32;
+		static final int KEY_SIZE = 32;
 
-		static final byte[] JETS3T_SALT = { //
+		static final byte[] SALT = { //
 				(byte) 0xA4, (byte) 0x0B, (byte) 0xC8, (byte) 0x34, //
 				(byte) 0xD6, (byte) 0x95, (byte) 0xF3, (byte) 0x13 //
 		};
@@ -191,7 +204,7 @@ abstract class WalkEncryption {
 		// Size 16, see com.sun.crypto.provider.AESConstants.AES_BLOCK_SIZE
 		static final byte[] ZERO_AES_IV = new byte[16];
 
-		private final String cryptoVer = JETS3T_VERSION;
+		private static final String cryptoVer = VERSION;
 
 		private final String cryptoAlg;
 
@@ -199,10 +212,13 @@ abstract class WalkEncryption {
 
 		private final AlgorithmParameterSpec paramSpec;
 
-		ObjectEncryptionJetS3tV2(final String algo, final String key)
+		JetS3tV2(final String algo, final String key)
 				throws GeneralSecurityException {
 			cryptoAlg = algo;
 
+			// Verify if cipher is present.
+			Cipher cipher = Cipher.getInstance(cryptoAlg);
+
 			// Standard names are not case-sensitive.
 			// http://docs.oracle.com/javase/8/docs/technotes/guides/security/StandardNames.html
 			String cryptoName = cryptoAlg.toUpperCase();
@@ -210,7 +226,7 @@ abstract class WalkEncryption {
 			if (!cryptoName.startsWith("PBE")) //$NON-NLS-1$
 				throw new GeneralSecurityException(JGitText.get().encryptionOnlyPBE);
 
-			PBEKeySpec keySpec = new PBEKeySpec(key.toCharArray(), JETS3T_SALT, JETS3T_ITERATIONS, JETS3T_KEY_SIZE);
+			PBEKeySpec keySpec = new PBEKeySpec(key.toCharArray(), SALT, ITERATIONS, KEY_SIZE);
 			secretKey = SecretKeyFactory.getInstance(algo).generateSecret(keySpec);
 
 			// Detect algorithms which require initialization vector.
@@ -229,12 +245,16 @@ abstract class WalkEncryption {
 				// https://bitbucket.org/jmurty/jets3t/raw/156c00eb160598c2e9937fd6873f00d3190e28ca/src/org/jets3t/service/security/EncryptionUtil.java
 				// http://cr.openjdk.java.net/~mullan/webrevs/ascarpin/webrev.00/raw_files/new/src/share/classes/com/sun/crypto/provider/PBES2Core.java
 				IvParameterSpec paramIV = new IvParameterSpec(ZERO_AES_IV);
-				paramSpec = java8PBEParameterSpec(JETS3T_SALT, JETS3T_ITERATIONS, paramIV);
+				paramSpec = java8PBEParameterSpec(SALT, ITERATIONS, paramIV);
 			} else {
 				// Strict legacy JetS3t V2 compatibility, with no IV support.
-				paramSpec = java7PBEParameterSpec(JETS3T_SALT, JETS3T_ITERATIONS);
+				paramSpec = java7PBEParameterSpec(SALT, ITERATIONS);
 			}
 
+			// Verify if cipher + key are allowed by policy.
+			cipher.init(Cipher.ENCRYPT_MODE, secretKey, paramSpec);
+			cipher.doFinal();
+
 		}
 
 		@Override
@@ -271,4 +291,303 @@ abstract class WalkEncryption {
 			}
 		}
 	}
+
+	/** Encryption property names. */
+	interface Keys {
+		// Remote S3 meta: V1 algorithm name or V2 profile name.
+		String JGIT_PROFILE = "jgit-crypto-profile"; //$NON-NLS-1$
+
+		// Remote S3 meta: JGit encryption implementation version.
+		String JGIT_VERSION = "jgit-crypto-version"; //$NON-NLS-1$
+
+		// Remote S3 meta: base-64 encoded cipher algorithm parameters.
+		String JGIT_CONTEXT = "jgit-crypto-context"; //$NON-NLS-1$
+
+		// Amazon S3 connection configuration file profile property suffixes:
+		String X_ALGO = ".algo"; //$NON-NLS-1$
+		String X_KEY_ALGO = ".key.algo"; //$NON-NLS-1$
+		String X_KEY_SIZE = ".key.size"; //$NON-NLS-1$
+		String X_KEY_ITER = ".key.iter"; //$NON-NLS-1$
+		String X_KEY_SALT = ".key.salt"; //$NON-NLS-1$
+	}
+
+	/** Encryption constants and defaults. */
+	interface Vals {
+		// Compatibility defaults.
+		String DEFAULT_VERS = "0"; //$NON-NLS-1$
+		String DEFAULT_ALGO = JetS3tV2.ALGORITHM;
+		String DEFAULT_KEY_ALGO = JetS3tV2.ALGORITHM;
+		String DEFAULT_KEY_SIZE = Integer.toString(JetS3tV2.KEY_SIZE);
+		String DEFAULT_KEY_ITER = Integer.toString(JetS3tV2.ITERATIONS);
+		String DEFAULT_KEY_SALT = DatatypeConverter.printHexBinary(JetS3tV2.SALT);
+
+		String EMPTY = ""; //$NON-NLS-1$
+
+		// Match white space.
+		String REGEX_WS = "\\s+"; //$NON-NLS-1$
+
+		// Match PBE ciphers, i.e: PBEWithMD5AndDES
+		String REGEX_PBE = "(PBE).*(WITH).+(AND).+"; //$NON-NLS-1$
+
+		// Match transformation ciphers, i.e: AES/CBC/PKCS5Padding
+		String REGEX_TRANS = "(.+)/(.+)/(.+)"; //$NON-NLS-1$
+	}
+
+	static GeneralSecurityException securityError(String message) {
+		return new GeneralSecurityException(
+				MessageFormat.format(JGitText.get().encryptionError, message));
+	}
+
+	/**
+	 * Base implementation of JGit symmetric encryption. Supports V2 properties
+	 * format.
+	 */
+	static abstract class SymmetricEncryption extends WalkEncryption
+			implements Keys, Vals {
+
+		/** Encryption profile, root name of group of related properties. */
+		final String profile;
+
+		/** Encryption version, reflects actual implementation class. */
+		final String version;
+
+		/** Full cipher algorithm name. */
+		final String cipherAlgo;
+
+		/** Cipher algorithm name for parameters lookup. */
+		final String paramsAlgo;
+
+		/** Generated secret key. */
+		final SecretKey secretKey;
+
+		SymmetricEncryption(Properties props) throws GeneralSecurityException {
+
+			profile = props.getProperty(AmazonS3.Keys.CRYPTO_ALG);
+			version = props.getProperty(AmazonS3.Keys.CRYPTO_VER);
+			String pass = props.getProperty(AmazonS3.Keys.PASSWORD);
+
+			cipherAlgo = props.getProperty(profile + X_ALGO, DEFAULT_ALGO);
+
+			String keyAlgo = props.getProperty(profile + X_KEY_ALGO, DEFAULT_KEY_ALGO);
+			String keySize = props.getProperty(profile + X_KEY_SIZE, DEFAULT_KEY_SIZE);
+			String keyIter = props.getProperty(profile + X_KEY_ITER, DEFAULT_KEY_ITER);
+			String keySalt = props.getProperty(profile + X_KEY_SALT, DEFAULT_KEY_SALT);
+
+			// Verify if cipher is present.
+			Cipher cipher = Cipher.getInstance(cipherAlgo);
+
+			// Verify if key factory is present.
+			SecretKeyFactory factory = SecretKeyFactory.getInstance(keyAlgo);
+
+			final int size;
+			try {
+				size = Integer.parseInt(keySize);
+			} catch (Exception e) {
+				throw securityError(X_KEY_SIZE + EMPTY + keySize);
+			}
+
+			final int iter;
+			try {
+				iter = Integer.parseInt(keyIter);
+			} catch (Exception e) {
+				throw securityError(X_KEY_ITER + EMPTY + keyIter);
+			}
+
+			final byte[] salt;
+			try {
+				salt = DatatypeConverter
+						.parseHexBinary(keySalt.replaceAll(REGEX_WS, EMPTY));
+			} catch (Exception e) {
+				throw securityError(X_KEY_SALT + EMPTY + keySalt);
+			}
+
+			KeySpec keySpec = new PBEKeySpec(pass.toCharArray(), salt, iter, size);
+
+			SecretKey keyBase = factory.generateSecret(keySpec);
+
+			String name = cipherAlgo.toUpperCase();
+			Matcher matcherPBE = Pattern.compile(REGEX_PBE).matcher(name);
+			Matcher matcherTrans = Pattern.compile(REGEX_TRANS).matcher(name);
+			if (matcherPBE.matches()) {
+				paramsAlgo = cipherAlgo;
+				secretKey = keyBase;
+			} else if (matcherTrans.find()) {
+				paramsAlgo = matcherTrans.group(1);
+				secretKey = new SecretKeySpec(keyBase.getEncoded(), paramsAlgo);
+			} else {
+				throw new GeneralSecurityException(MessageFormat.format(
+						JGitText.get().unsupportedEncryptionAlgorithm,
+						cipherAlgo));
+			}
+
+			// Verify if cipher + key are allowed by policy.
+			cipher.init(Cipher.ENCRYPT_MODE, secretKey);
+			cipher.doFinal();
+
+		}
+
+		// Shared state encrypt -> request.
+		volatile String context;
+
+		@Override
+		OutputStream encrypt(OutputStream output) throws IOException {
+			try {
+				Cipher cipher = Cipher.getInstance(cipherAlgo);
+				cipher.init(Cipher.ENCRYPT_MODE, secretKey);
+				AlgorithmParameters params = cipher.getParameters();
+				if (params == null) {
+					context = EMPTY;
+				} else {
+					context = Base64.encodeBytes(params.getEncoded());
+				}
+				return new CipherOutputStream(output, cipher);
+			} catch (Exception e) {
+				throw error(e);
+			}
+		}
+
+		@Override
+		void request(HttpURLConnection conn, String prefix) throws IOException {
+			conn.setRequestProperty(prefix + JGIT_PROFILE, profile);
+			conn.setRequestProperty(prefix + JGIT_VERSION, version);
+			conn.setRequestProperty(prefix + JGIT_CONTEXT, context);
+			// No cleanup:
+			// single encrypt can be followed by several request
+			// from the AmazonS3.putImpl() multiple retry attempts
+			// context = null; // Cleanup encrypt -> request transition.
+			// TODO re-factor AmazonS3.putImpl to be more transaction-like
+		}
+
+		// Shared state validate -> decrypt.
+		volatile Cipher decryptCipher;
+
+		@Override
+		void validate(HttpURLConnection conn, String prefix)
+				throws IOException {
+			String prof = conn.getHeaderField(prefix + JGIT_PROFILE);
+			String vers = conn.getHeaderField(prefix + JGIT_VERSION);
+			String cont = conn.getHeaderField(prefix + JGIT_CONTEXT);
+
+			if (prof == null) {
+				throw new IOException(MessageFormat
+						.format(JGitText.get().encryptionError, JGIT_PROFILE));
+			}
+			if (vers == null) {
+				throw new IOException(MessageFormat
+						.format(JGitText.get().encryptionError, JGIT_VERSION));
+			}
+			if (cont == null) {
+				throw new IOException(MessageFormat
+						.format(JGitText.get().encryptionError, JGIT_CONTEXT));
+			}
+			if (!profile.equals(prof)) {
+				throw new IOException(MessageFormat.format(
+						JGitText.get().unsupportedEncryptionAlgorithm, prof));
+			}
+			if (!version.equals(vers)) {
+				throw new IOException(MessageFormat.format(
+						JGitText.get().unsupportedEncryptionVersion, vers));
+			}
+			try {
+				decryptCipher = Cipher.getInstance(cipherAlgo);
+				if (cont.isEmpty()) {
+					decryptCipher.init(Cipher.DECRYPT_MODE, secretKey);
+				} else {
+					AlgorithmParameters params = AlgorithmParameters
+							.getInstance(paramsAlgo);
+					params.init(Base64.decode(cont));
+					decryptCipher.init(Cipher.DECRYPT_MODE, secretKey, params);
+				}
+			} catch (Exception e) {
+				throw error(e);
+			}
+		}
+
+		@Override
+		InputStream decrypt(InputStream input) throws IOException {
+			try {
+				return new CipherInputStream(input, decryptCipher);
+			} finally {
+				decryptCipher = null; // Cleanup validate -> decrypt transition.
+			}
+		}
+	}
+
+	/**
+	 * Provides JetS3t-like encryption with AES support. Uses V1 connection file
+	 * format. For reference, see: 'jgit-s3-connection-v-1.properties'.
+	 */
+	static class JGitV1 extends SymmetricEncryption {
+
+		static final String VERSION = "1"; //$NON-NLS-1$
+
+		// Re-map connection properties V1 -> V2.
+		static Properties wrap(String algo, String pass) {
+			Properties props = new Properties();
+			props.put(AmazonS3.Keys.CRYPTO_ALG, algo);
+			props.put(AmazonS3.Keys.CRYPTO_VER, VERSION);
+			props.put(AmazonS3.Keys.PASSWORD, pass);
+			props.put(algo + Keys.X_ALGO, algo);
+			props.put(algo + Keys.X_KEY_ALGO, algo);
+			props.put(algo + Keys.X_KEY_ITER, DEFAULT_KEY_ITER);
+			props.put(algo + Keys.X_KEY_SIZE, DEFAULT_KEY_SIZE);
+			props.put(algo + Keys.X_KEY_SALT, DEFAULT_KEY_SALT);
+			return props;
+		}
+
+		JGitV1(String algo, String pass)
+				throws GeneralSecurityException {
+			super(wrap(algo, pass));
+			String name = cipherAlgo.toUpperCase();
+			Matcher matcherPBE = Pattern.compile(REGEX_PBE).matcher(name);
+			if (!matcherPBE.matches())
+				throw new GeneralSecurityException(
+						JGitText.get().encryptionOnlyPBE);
+		}
+
+	}
+
+	/**
+	 * Supports both PBE and non-PBE algorithms. Uses V2 connection file format.
+	 * For reference, see: 'jgit-s3-connection-v-2.properties'.
+	 */
+	static class JGitV2 extends SymmetricEncryption {
+
+		static final String VERSION = "2"; //$NON-NLS-1$
+
+		JGitV2(Properties props)
+				throws GeneralSecurityException {
+			super(props);
+		}
+	}
+
+	/**
+	 * Encryption factory.
+	 *
+	 * @param props
+	 * @return instance
+	 * @throws GeneralSecurityException
+	 */
+	static WalkEncryption instance(Properties props)
+			throws GeneralSecurityException {
+
+		String algo = props.getProperty(AmazonS3.Keys.CRYPTO_ALG, Vals.DEFAULT_ALGO);
+		String vers = props.getProperty(AmazonS3.Keys.CRYPTO_VER, Vals.DEFAULT_VERS);
+		String pass = props.getProperty(AmazonS3.Keys.PASSWORD);
+
+		if (pass == null) // Disable encryption.
+			return WalkEncryption.NONE;
+
+		switch (vers) {
+		case Vals.DEFAULT_VERS:
+			return new JetS3tV2(algo, pass);
+		case JGitV1.VERSION:
+			return new JGitV1(algo, pass);
+		case JGitV2.VERSION:
+			return new JGitV2(props);
+		default:
+			throw new GeneralSecurityException(MessageFormat.format(
+					JGitText.get().unsupportedEncryptionVersion, vers));
+		}
+	}
 }