/*
    * Copyright (C) 2018, Salesforce.
    * 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,
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  package org.eclipse.jgit.lib.internal;
  
  import static java.nio.file.Files.exists;
  import static java.nio.file.Files.newInputStream;
  
  import java.io.BufferedInputStream;
  import java.io.File;
  import java.io.IOException;
  import java.io.InputStream;
  import java.net.URISyntaxException;
  import java.nio.file.Files;
  import java.nio.file.InvalidPathException;
  import java.nio.file.Path;
  import java.nio.file.Paths;
  import java.text.MessageFormat;
  import java.util.Iterator;
  import java.util.Locale;
  import java.util.stream.Collectors;
  import java.util.stream.Stream;
  
  import org.bouncycastle.gpg.SExprParser;
  import org.bouncycastle.gpg.keybox.BlobType;
  import org.bouncycastle.gpg.keybox.KeyBlob;
  import org.bouncycastle.gpg.keybox.KeyBox;
  import org.bouncycastle.gpg.keybox.KeyInformation;
  import org.bouncycastle.gpg.keybox.PublicKeyRingBlob;
  import org.bouncycastle.gpg.keybox.UserID;
  import org.bouncycastle.openpgp.PGPException;
  import org.bouncycastle.openpgp.PGPPublicKey;
  import org.bouncycastle.openpgp.PGPSecretKey;
  import org.bouncycastle.openpgp.PGPSecretKeyRing;
  import org.bouncycastle.openpgp.PGPSecretKeyRingCollection;
  import org.bouncycastle.openpgp.PGPUtil;
  import org.bouncycastle.openpgp.operator.PBEProtectionRemoverFactory;
  import org.bouncycastle.openpgp.operator.PGPDigestCalculatorProvider;
  import org.bouncycastle.openpgp.operator.jcajce.JcaKeyFingerprintCalculator;
  import org.bouncycastle.openpgp.operator.jcajce.JcaPGPDigestCalculatorProviderBuilder;
  import org.bouncycastle.openpgp.operator.jcajce.JcePBEProtectionRemoverFactory;
  import org.bouncycastle.util.encoders.Hex;
  import org.eclipse.jgit.annotations.NonNull;
  import org.eclipse.jgit.api.errors.CanceledException;
  import org.eclipse.jgit.errors.UnsupportedCredentialItem;
  import org.eclipse.jgit.internal.JGitText;
  import org.eclipse.jgit.util.FS;
  import org.eclipse.jgit.util.SystemReader;
  
  /**
   * Locates GPG keys from either <code>~/.gnupg/private-keys-v1.d</code> or
   * <code>~/.gnupg/secring.gpg</code>
   */
  class BouncyCastleGpgKeyLocator {
  
  	private static final Path GPG_DIRECTORY = findGpgDirectory();
  
  	private static final Path USER_KEYBOX_PATH = GPG_DIRECTORY
  			.resolve("pubring.kbx"); //$NON-NLS-1$
  
 	private static final Path USER_SECRET_KEY_DIR = GPG_DIRECTORY
 			.resolve("private-keys-v1.d"); //$NON-NLS-1$
 
 	private static final Path USER_PGP_LEGACY_SECRING_FILE = GPG_DIRECTORY
 			.resolve("secring.gpg"); //$NON-NLS-1$
 
 	private final String signingKey;
 
 	private BouncyCastleGpgKeyPassphrasePrompt passphrasePrompt;
 
 	private static Path findGpgDirectory() {
 		SystemReader system = SystemReader.getInstance();
 		if (system.isWindows()) {
 			// On Windows prefer %APPDATA%\gnupg if it exists, even if Cygwin is
 			// used.
 			String appData = system.getenv("APPDATA"); //$NON-NLS-1$
 			if (appData != null && !appData.isEmpty()) {
 				try {
 					Path directory = Paths.get(appData).resolve("gnupg"); //$NON-NLS-1$
 					if (Files.isDirectory(directory)) {
 						return directory;
 					}
 				} catch (SecurityException | InvalidPathException e) {
 					// Ignore and return the default location below.
 				}
 			}
 		}
 		// All systems, including Cygwin and even Windows if
 		// %APPDATA%\gnupg doesn't exist: ~/.gnupg
 		File home = FS.DETECTED.userHome();
 		if (home == null) {
 			// Oops. What now?
 			home = new File(".").getAbsoluteFile(); //$NON-NLS-1$
 		}
 		return home.toPath().resolve(".gnupg"); //$NON-NLS-1$
 	}
 
 	/**
 	 * Create a new key locator for the specified signing key.
 	 * <p>
 	 * The signing key must either be a hex representation of a specific key or
 	 * a user identity substring (eg., email address). All keys in the KeyBox
 	 * will be looked up in the order as returned by the KeyBox. A key id will
 	 * be searched before attempting to find a key by user id.
 	 * </p>
 	 *
 	 * @param signingKey
 	 *            the signing key to search for
 	 * @param passphrasePrompt
 	 *            the provider to use when asking for key passphrase
 	 */
 	public BouncyCastleGpgKeyLocator(String signingKey,
 			@NonNull BouncyCastleGpgKeyPassphrasePrompt passphrasePrompt) {
 		this.signingKey = signingKey;
 		this.passphrasePrompt = passphrasePrompt;
 	}
 
 	private PGPSecretKey attemptParseSecretKey(Path keyFile,
 			PGPDigestCalculatorProvider calculatorProvider,
 			PBEProtectionRemoverFactory passphraseProvider,
 			PGPPublicKey publicKey) throws IOException {
 		try (InputStream in = newInputStream(keyFile)) {
 			return new SExprParser(calculatorProvider).parseSecretKey(
 					new BufferedInputStream(in), passphraseProvider, publicKey);
 		} catch (PGPException | ClassCastException e) {
 			return null;
 		}
 	}
 
 	private boolean containsSigningKey(String userId) {
 		return userId.toLowerCase(Locale.ROOT)
 				.contains(signingKey.toLowerCase(Locale.ROOT));
 	}
 
 	private PGPPublicKey findPublicKeyByKeyId(KeyBlob keyBlob)
 			throws IOException {
 		for (KeyInformation keyInfo : keyBlob.getKeyInformation()) {
 			if (signingKey.toLowerCase(Locale.ROOT)
 					.equals(Hex.toHexString(keyInfo.getKeyID())
 							.toLowerCase(Locale.ROOT))) {
 				return getFirstPublicKey(keyBlob);
 			}
 		}
 		return null;
 	}
 
 	private PGPPublicKey findPublicKeyByUserId(KeyBlob keyBlob)
 			throws IOException {
 		for (UserID userID : keyBlob.getUserIds()) {
 			if (containsSigningKey(userID.getUserIDAsString())) {
 				return getFirstPublicKey(keyBlob);
 			}
 		}
 		return null;
 	}
 
 	/**
 	 * Finds a public key associated with the signing key.
 	 *
 	 * @param keyboxFile
 	 *            the KeyBox file
 	 * @return publicKey the public key (maybe <code>null</code>)
 	 * @throws IOException
 	 *             in case of problems reading the file
 	 */
 	private PGPPublicKey findPublicKeyInKeyBox(Path keyboxFile)
 			throws IOException {
 		KeyBox keyBox = readKeyBoxFile(keyboxFile);
 		for (KeyBlob keyBlob : keyBox.getKeyBlobs()) {
 			if (keyBlob.getType() == BlobType.OPEN_PGP_BLOB) {
 				PGPPublicKey key = findPublicKeyByKeyId(keyBlob);
 				if (key != null) {
 					return key;
 				}
 				key = findPublicKeyByUserId(keyBlob);
 				if (key != null) {
 					return key;
 				}
 			}
 		}
 		return null;
 	}
 
 	/**
 	 * Use pubring.kbx when available, if not fallback to secring.gpg or secret
 	 * key path provided to parse and return secret key
 	 *
 	 * @return the secret key
 	 * @throws IOException
 	 *             in case of issues reading key files
 	 * @throws PGPException
 	 *             in case of issues finding a key
 	 * @throws CanceledException
 	 * @throws URISyntaxException
 	 * @throws UnsupportedCredentialItem
 	 */
 	public BouncyCastleGpgKey findSecretKey()
 			throws IOException, PGPException, CanceledException,
 			UnsupportedCredentialItem, URISyntaxException {
 		if (exists(USER_KEYBOX_PATH)) {
 			PGPPublicKey publicKey = //
 					findPublicKeyInKeyBox(USER_KEYBOX_PATH);
 
 			if (publicKey != null) {
 				return findSecretKeyForKeyBoxPublicKey(publicKey,
 						USER_KEYBOX_PATH);
 			}
 
 			throw new PGPException(MessageFormat
 					.format(JGitText.get().gpgNoPublicKeyFound, signingKey));
 		} else if (exists(USER_PGP_LEGACY_SECRING_FILE)) {
 			PGPSecretKey secretKey = findSecretKeyInLegacySecring(signingKey,
 					USER_PGP_LEGACY_SECRING_FILE);
 
 			if (secretKey != null) {
 				return new BouncyCastleGpgKey(secretKey, USER_PGP_LEGACY_SECRING_FILE);
 			}
 
 			throw new PGPException(MessageFormat.format(
 					JGitText.get().gpgNoKeyInLegacySecring, signingKey));
 		}
 
 		throw new PGPException(JGitText.get().gpgNoKeyring);
 	}
 
 	private BouncyCastleGpgKey findSecretKeyForKeyBoxPublicKey(
 			PGPPublicKey publicKey, Path userKeyboxPath)
 			throws PGPException, CanceledException, UnsupportedCredentialItem,
 			URISyntaxException {
 		/*
 		 * this is somewhat brute-force but there doesn't seem to be another
 		 * way; we have to walk all private key files we find and try to open
 		 * them
 		 */
 
 		PGPDigestCalculatorProvider calculatorProvider = new JcaPGPDigestCalculatorProviderBuilder()
 				.build();
 
 		PBEProtectionRemoverFactory passphraseProvider = new JcePBEProtectionRemoverFactory(
 				passphrasePrompt.getPassphrase(publicKey.getFingerprint(),
 						userKeyboxPath));
 
 		try (Stream<Path> keyFiles = Files.walk(USER_SECRET_KEY_DIR)) {
 			for (Path keyFile : keyFiles.filter(Files::isRegularFile)
 					.collect(Collectors.toList())) {
 				PGPSecretKey secretKey = attemptParseSecretKey(keyFile,
 						calculatorProvider, passphraseProvider, publicKey);
 				if (secretKey != null) {
 					return new BouncyCastleGpgKey(secretKey, userKeyboxPath);
 				}
 			}
 
 			passphrasePrompt.clear();
 			throw new PGPException(MessageFormat.format(
 					JGitText.get().gpgNoSecretKeyForPublicKey,
 					Long.toHexString(publicKey.getKeyID())));
 		} catch (RuntimeException e) {
 			passphrasePrompt.clear();
 			throw e;
 		} catch (IOException e) {
 			passphrasePrompt.clear();
 			throw new PGPException(MessageFormat.format(
 					JGitText.get().gpgFailedToParseSecretKey,
 					USER_SECRET_KEY_DIR.toAbsolutePath()), e);
 		}
 	}
 
 	/**
 	 * Return the first suitable key for signing in the key ring collection. For
 	 * this case we only expect there to be one key available for signing.
 	 * </p>
 	 *
 	 * @param signingkey
 	 * @param secringFile
 	 *
 	 * @return the first suitable PGP secret key found for signing
 	 * @throws IOException
 	 *             on I/O related errors
 	 * @throws PGPException
 	 *             on BouncyCastle errors
 	 */
 	private PGPSecretKey findSecretKeyInLegacySecring(String signingkey,
 			Path secringFile) throws IOException, PGPException {
 
 		try (InputStream in = newInputStream(secringFile)) {
 			PGPSecretKeyRingCollection pgpSec = new PGPSecretKeyRingCollection(
 					PGPUtil.getDecoderStream(new BufferedInputStream(in)),
 					new JcaKeyFingerprintCalculator());
 
 			Iterator<PGPSecretKeyRing> keyrings = pgpSec.getKeyRings();
 			while (keyrings.hasNext()) {
 				PGPSecretKeyRing keyRing = keyrings.next();
 				Iterator<PGPSecretKey> keys = keyRing.getSecretKeys();
 				while (keys.hasNext()) {
 					PGPSecretKey key = keys.next();
 					// try key id
 					String fingerprint = Hex
 							.toHexString(key.getPublicKey().getFingerprint())
 							.toLowerCase(Locale.ROOT);
 					if (fingerprint
 							.endsWith(signingkey.toLowerCase(Locale.ROOT))) {
 						return key;
 					}
 					// try user id
 					Iterator<String> userIDs = key.getUserIDs();
 					while (userIDs.hasNext()) {
 						String userId = userIDs.next();
 						if (containsSigningKey(userId)) {
 							return key;
 						}
 					}
 				}
 			}
 		}
 		return null;
 	}
 
 	private PGPPublicKey getFirstPublicKey(KeyBlob keyBlob) throws IOException {
 		return ((PublicKeyRingBlob) keyBlob).getPGPPublicKeyRing()
 				.getPublicKey();
 	}
 
 	private KeyBox readKeyBoxFile(Path keyboxFile) throws IOException {
 		KeyBox keyBox;
 		try (InputStream in = new BufferedInputStream(
 				newInputStream(keyboxFile))) {
 			// note: KeyBox constructor reads in the whole InputStream at once
 			// this code will change in 1.61 to
 			// either 'new BcKeyBox(in)' or 'new JcaKeyBoxBuilder().build(in)'
 			keyBox = new KeyBox(in, new JcaKeyFingerprintCalculator());
 		}
 		return keyBox;
 	}
 }