/*
    * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
    * 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,
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   * 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.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;
  import javax.crypto.CipherOutputStream;
  import javax.crypto.SecretKey;
  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();
  
  	static final String JETS3T_CRYPTO_VER = "jets3t-crypto-ver"; //$NON-NLS-1$
  
  	static final String JETS3T_CRYPTO_ALG = "jets3t-crypto-alg"; //$NON-NLS-1$
  
  	// Note: encrypt -> request state machine, step 1.
  	abstract OutputStream encrypt(OutputStream output) throws IOException;
  
  	// Note: encrypt -> request state machine, step 2.
  	abstract void request(HttpURLConnection conn, String prefix) throws IOException;
  
  	// 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;
  
  
  	// TODO mixed ciphers
  	// consider permitting mixed ciphers to facilitate algorithm migration
  	// i.e. user keeps the password, but changes the algorithm
  	// then existing remote entries will still be readable
  	protected void validateImpl(final HttpURLConnection u, final String prefix,
  			final String version, final String name) throws IOException {
  		String v;
 
 		v = u.getHeaderField(prefix + JETS3T_CRYPTO_VER);
 		if (v == null)
 			v = ""; //$NON-NLS-1$
 		if (!version.equals(v))
 			throw new IOException(MessageFormat.format(JGitText.get().unsupportedEncryptionVersion, v));
 
 		v = u.getHeaderField(prefix + JETS3T_CRYPTO_ALG);
 		if (v == null)
 			v = ""; //$NON-NLS-1$
 		// Standard names are not case-sensitive.
 		// http://docs.oracle.com/javase/8/docs/technotes/guides/security/StandardNames.html
 		if (!name.equalsIgnoreCase(v))
 			throw new IOException(MessageFormat.format(JGitText.get().unsupportedEncryptionAlgorithm, v));
 	}
 
 	IOException error(final Throwable why) {
 		final IOException e;
 		e = new IOException(MessageFormat.format(JGitText.get().encryptionError, why.getMessage()));
 		e.initCause(why);
 		return e;
 	}
 
 	private static class NoEncryption extends WalkEncryption {
 		@Override
 		void request(HttpURLConnection u, String prefix) {
 			// Don't store any request properties.
 		}
 
 		@Override
 		void validate(final HttpURLConnection u, final String prefix)
 				throws IOException {
 			validateImpl(u, prefix, "", ""); //$NON-NLS-1$ //$NON-NLS-2$
 		}
 
 		@Override
 		InputStream decrypt(InputStream in) {
 			return in;
 		}
 
 		@Override
 		OutputStream encrypt(OutputStream os) {
 			return os;
 		}
 	}
 
 	// PBEParameterSpec factory for Java (version <= 7).
 	// Does not support AlgorithmParameterSpec.
 	static PBEParameterSpec java7PBEParameterSpec(byte[] salt,
 			int iterationCount) {
 		return new PBEParameterSpec(salt, iterationCount);
 	}
 
 	// PBEParameterSpec factory for Java (version >= 8).
 	// Adds support for AlgorithmParameterSpec.
 	static PBEParameterSpec java8PBEParameterSpec(byte[] salt,
 			int iterationCount, AlgorithmParameterSpec paramSpec) {
 		try {
 			@SuppressWarnings("boxing")
 			PBEParameterSpec instance = PBEParameterSpec.class
 					.getConstructor(byte[].class, int.class,
 							AlgorithmParameterSpec.class)
 					.newInstance(salt, iterationCount, paramSpec);
 			return instance;
 		} catch (Exception e) {
 			throw new RuntimeException(e);
 		}
 	}
 
 	// Current runtime version.
 	// https://docs.oracle.com/javase/7/docs/technotes/guides/versioning/spec/versioning2.html
 	static double javaVersion() {
 		return Double.parseDouble(System.getProperty("java.specification.version")); //$NON-NLS-1$
 	}
 
 	/**
 	 * JetS3t compatibility reference: <a href=
 	 * "https://bitbucket.org/jmurty/jets3t/src/156c00eb160598c2e9937fd6873f00d3190e28ca/src/org/jets3t/service/security/EncryptionUtil.java">
 	 * EncryptionUtil.java</a>
 	 * <p>
 	 * Note: EncryptionUtil is inadequate:
 	 * <li>EncryptionUtil.isCipherAvailableForUse checks encryption only which
 	 * "always works", but in JetS3t both encryption and decryption use non-IV
 	 * aware algorithm parameters for all PBE specs, which breaks in case of AES
 	 * <li>that means that only non-IV algorithms will work round trip in
 	 * JetS3t, such as PBEWithMD5AndDES and PBEWithSHAAndTwofish-CBC
 	 * <li>any AES based algorithms such as "PBE...With...And...AES" will not
 	 * work, since they need proper IV setup
 	 */
 	static class JetS3tV2 extends WalkEncryption {
 
 		static final String VERSION = "2"; //$NON-NLS-1$
 
 		static final String ALGORITHM = "PBEWithMD5AndDES"; //$NON-NLS-1$
 
 		static final int ITERATIONS = 5000;
 
 		static final int KEY_SIZE = 32;
 
 		static final byte[] SALT = { //
 				(byte) 0xA4, (byte) 0x0B, (byte) 0xC8, (byte) 0x34, //
 				(byte) 0xD6, (byte) 0x95, (byte) 0xF3, (byte) 0x13 //
 		};
 
 		// Size 16, see com.sun.crypto.provider.AESConstants.AES_BLOCK_SIZE
 		static final byte[] ZERO_AES_IV = new byte[16];
 
 		private static final String cryptoVer = VERSION;
 
 		private final String cryptoAlg;
 
 		private final SecretKey secretKey;
 
 		private final AlgorithmParameterSpec paramSpec;
 
 		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();
 
 			if (!cryptoName.startsWith("PBE")) //$NON-NLS-1$
 				throw new GeneralSecurityException(JGitText.get().encryptionOnlyPBE);
 
 			PBEKeySpec keySpec = new PBEKeySpec(key.toCharArray(), SALT, ITERATIONS, KEY_SIZE);
 			secretKey = SecretKeyFactory.getInstance(algo).generateSecret(keySpec);
 
 			// Detect algorithms which require initialization vector.
 			boolean useIV = cryptoName.contains("AES"); //$NON-NLS-1$
 
 			// PBEParameterSpec algorithm parameters are supported from Java 8.
 			boolean isJava8 = javaVersion() >= 1.8;
 
 			if (useIV && isJava8) {
 				// Support IV where possible:
 				// * since JCE provider uses random IV for PBE/AES
 				// * and there is no place to store dynamic IV in JetS3t V2
 				// * we use static IV, and tolerate increased security risk
 				// TODO back port this change to JetS3t V2
 				// See:
 				// 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(SALT, ITERATIONS, paramIV);
 			} else {
 				// Strict legacy JetS3t V2 compatibility, with no IV support.
 				paramSpec = java7PBEParameterSpec(SALT, ITERATIONS);
 			}
 
 			// Verify if cipher + key are allowed by policy.
 			cipher.init(Cipher.ENCRYPT_MODE, secretKey, paramSpec);
 			cipher.doFinal();
 
 		}
 
 		@Override
 		void request(final HttpURLConnection u, final String prefix) {
 			u.setRequestProperty(prefix + JETS3T_CRYPTO_VER, cryptoVer);
 			u.setRequestProperty(prefix + JETS3T_CRYPTO_ALG, cryptoAlg);
 		}
 
 		@Override
 		void validate(final HttpURLConnection u, final String prefix)
 				throws IOException {
 			validateImpl(u, prefix, cryptoVer, cryptoAlg);
 		}
 
 		@Override
 		OutputStream encrypt(final OutputStream os) throws IOException {
 			try {
 				final Cipher cipher = Cipher.getInstance(cryptoAlg);
 				cipher.init(Cipher.ENCRYPT_MODE, secretKey, paramSpec);
 				return new CipherOutputStream(os, cipher);
 			} catch (GeneralSecurityException e) {
 				throw error(e);
 			}
 		}
 
 		@Override
 		InputStream decrypt(final InputStream in) throws IOException {
 			try {
 				final Cipher cipher = Cipher.getInstance(cryptoAlg);
 				cipher.init(Cipher.DECRYPT_MODE, secretKey, paramSpec);
 				return new CipherInputStream(in, cipher);
 			} catch (GeneralSecurityException e) {
 				throw error(e);
 			}
 		}
 	}
 
 	/** 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));
 		}
 	}
 }