/*
    * Copyright (C) 2010, 2013, 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
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   * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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  package org.eclipse.jgit.transport;
  
  import static org.eclipse.jgit.util.HttpSupport.HDR_AUTHORIZATION;
  import static org.eclipse.jgit.util.HttpSupport.HDR_WWW_AUTHENTICATE;
  
  import java.io.IOException;
  import java.io.UnsupportedEncodingException;
  import java.net.URL;
  import java.security.MessageDigest;
  import java.security.NoSuchAlgorithmException;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.LinkedHashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.Map.Entry;
  import java.util.Random;
  
  import org.eclipse.jgit.transport.http.HttpConnection;
  import org.eclipse.jgit.util.Base64;
  import org.eclipse.jgit.util.GSSManagerFactory;
  import org.ietf.jgss.GSSContext;
  import org.ietf.jgss.GSSException;
  import org.ietf.jgss.GSSManager;
  import org.ietf.jgss.GSSName;
  import org.ietf.jgss.Oid;
  
  /**
   * Support class to populate user authentication data on a connection.
   * <p>
   * Instances of an HttpAuthMethod are not thread-safe, as some implementations
   * may need to maintain per-connection state information.
   */
  abstract class HttpAuthMethod {
  	/**
  	 * Enum listing the http authentication method types supported by jgit. They
  	 * are sorted by priority order!!!
  	 */
  	public enum Type {
  		NONE {
  			@Override
  			public HttpAuthMethod method(String hdr) {
  				return None.INSTANCE;
  			}
  
  			@Override
  			public String getSchemeName() {
  				return "None"; //$NON-NLS-1$
  			}
  		},
  		BASIC {
  			@Override
  			public HttpAuthMethod method(String hdr) {
  				return new Basic();
  			}
  
 			@Override
 			public String getSchemeName() {
 				return "Basic"; //$NON-NLS-1$
 			}
 		},
 		DIGEST {
 			@Override
 			public HttpAuthMethod method(String hdr) {
 				return new Digest(hdr);
 			}
 
 			@Override
 			public String getSchemeName() {
 				return "Digest"; //$NON-NLS-1$
 			}
 		},
 		NEGOTIATE {
 			@Override
 			public HttpAuthMethod method(String hdr) {
 				return new Negotiate(hdr);
 			}
 
 			@Override
 			public String getSchemeName() {
 				return "Negotiate"; //$NON-NLS-1$
 			}
 		};
 		/**
 		 * Creates a HttpAuthMethod instance configured with the provided HTTP
 		 * WWW-Authenticate header.
 		 *
 		 * @param hdr the http header
 		 * @return a configured HttpAuthMethod instance
 		 */
 		public abstract HttpAuthMethod method(String hdr);
 
 		/**
 		 * @return the name of the authentication scheme in the form to be used
 		 *         in HTTP authentication headers as specified in RFC2617 and
 		 *         RFC4559
 		 */
 		public abstract String getSchemeName();
 	}
 
 	static final String EMPTY_STRING = ""; //$NON-NLS-1$
 	static final String SCHEMA_NAME_SEPARATOR = " "; //$NON-NLS-1$
 
 	/**
 	 * Handle an authentication failure and possibly return a new response.
 	 *
 	 * @param conn
 	 *            the connection that failed.
 	 * @return new authentication method to try.
 	 */
 	static HttpAuthMethod scanResponse(final HttpConnection conn) {
 		final Map<String, List<String>> headers = conn.getHeaderFields();
 		HttpAuthMethod authentication = Type.NONE.method(EMPTY_STRING);
 
 		for (final Entry<String, List<String>> entry : headers.entrySet()) {
 			if (HDR_WWW_AUTHENTICATE.equalsIgnoreCase(entry.getKey())) {
 				if (entry.getValue() != null) {
 					for (final String value : entry.getValue()) {
 						if (value != null && value.length() != 0) {
 							final String[] valuePart = value.split(
 									SCHEMA_NAME_SEPARATOR, 2);
 
 							try {
 								Type methodType = Type.valueOf(valuePart[0].toUpperCase());
 								if (authentication.getType().compareTo(methodType) >= 0) {
 									continue;
 								}
 
 								final String param;
 								if (valuePart.length == 1)
 									param = EMPTY_STRING;
 								else
 									param = valuePart[1];
 
 								authentication = methodType
 										.method(param);
 							} catch (IllegalArgumentException e) {
 								// This auth method is not supported
 							}
 						}
 					}
 				}
 				break;
 			}
 		}
 
 		return authentication;
 	}
 
 	protected final Type type;
 
 	protected HttpAuthMethod(Type type) {
 		this.type = type;
 	}
 
 	/**
 	 * Update this method with the credentials from the URIish.
 	 *
 	 * @param uri
 	 *            the URI used to create the connection.
 	 * @param credentialsProvider
 	 *            the credentials provider, or null. If provided,
 	 *            {@link URIish#getPass() credentials in the URI} are ignored.
 	 *
 	 * @return true if the authentication method is able to provide
 	 *         authorization for the given URI
 	 */
 	boolean authorize(URIish uri, CredentialsProvider credentialsProvider) {
 		String username;
 		String password;
 
 		if (credentialsProvider != null) {
 			CredentialItem.Username u = new CredentialItem.Username();
 			CredentialItem.Password p = new CredentialItem.Password();
 
 			if (credentialsProvider.supports(u, p)
 					&& credentialsProvider.get(uri, u, p)) {
 				username = u.getValue();
 				password = new String(p.getValue());
 				p.clear();
 			} else
 				return false;
 		} else {
 			username = uri.getUser();
 			password = uri.getPass();
 		}
 		if (username != null) {
 			authorize(username, password);
 			return true;
 		}
 		return false;
 	}
 
 	/**
 	 * Update this method with the given username and password pair.
 	 *
 	 * @param user
 	 * @param pass
 	 */
 	abstract void authorize(String user, String pass);
 
 	/**
 	 * Update connection properties based on this authentication method.
 	 *
 	 * @param conn
 	 * @throws IOException
 	 */
 	abstract void configureRequest(HttpConnection conn) throws IOException;
 
 	/**
 	 * Gives the method type associated to this http auth method
 	 *
 	 * @return the method type
 	 */
 	public Type getType() {
 		return type;
 	}
 
 	/** Performs no user authentication. */
 	private static class None extends HttpAuthMethod {
 		static final None INSTANCE = new None();
 		public None() {
 			super(Type.NONE);
 		}
 
 		@Override
 		void authorize(String user, String pass) {
 			// Do nothing when no authentication is enabled.
 		}
 
 		@Override
 		void configureRequest(HttpConnection conn) throws IOException {
 			// Do nothing when no authentication is enabled.
 		}
 	}
 
 	/** Performs HTTP basic authentication (plaintext username/password). */
 	private static class Basic extends HttpAuthMethod {
 		private String user;
 
 		private String pass;
 
 		public Basic() {
 			super(Type.BASIC);
 		}
 
 		@Override
 		void authorize(final String username, final String password) {
 			this.user = username;
 			this.pass = password;
 		}
 
 		@Override
 		void configureRequest(final HttpConnection conn) throws IOException {
 			String ident = user + ":" + pass; //$NON-NLS-1$
 			String enc = Base64.encodeBytes(ident.getBytes("UTF-8")); //$NON-NLS-1$
 			conn.setRequestProperty(HDR_AUTHORIZATION, type.getSchemeName()
 					+ " " + enc); //$NON-NLS-1$
 		}
 	}
 
 	/** Performs HTTP digest authentication. */
 	private static class Digest extends HttpAuthMethod {
 		private static final Random PRNG = new Random();
 
 		private final Map<String, String> params;
 
 		private int requestCount;
 
 		private String user;
 
 		private String pass;
 
 		Digest(String hdr) {
 			super(Type.DIGEST);
 			params = parse(hdr);
 
 			final String qop = params.get("qop"); //$NON-NLS-1$
 			if ("auth".equals(qop)) { //$NON-NLS-1$
 				final byte[] bin = new byte[8];
 				PRNG.nextBytes(bin);
 				params.put("cnonce", Base64.encodeBytes(bin)); //$NON-NLS-1$
 			}
 		}
 
 		@Override
 		void authorize(final String username, final String password) {
 			this.user = username;
 			this.pass = password;
 		}
 
 		@SuppressWarnings("boxing")
 		@Override
 		void configureRequest(final HttpConnection conn) throws IOException {
 			final Map<String, String> r = new LinkedHashMap<String, String>();
 
 			final String realm = params.get("realm"); //$NON-NLS-1$
 			final String nonce = params.get("nonce"); //$NON-NLS-1$
 			final String cnonce = params.get("cnonce"); //$NON-NLS-1$
 			final String uri = uri(conn.getURL());
 			final String qop = params.get("qop"); //$NON-NLS-1$
 			final String method = conn.getRequestMethod();
 
 			final String A1 = user + ":" + realm + ":" + pass; //$NON-NLS-1$ //$NON-NLS-2$
 			final String A2 = method + ":" + uri; //$NON-NLS-1$
 
 			r.put("username", user); //$NON-NLS-1$
 			r.put("realm", realm); //$NON-NLS-1$
 			r.put("nonce", nonce); //$NON-NLS-1$
 			r.put("uri", uri); //$NON-NLS-1$
 
 			final String response, nc;
 			if ("auth".equals(qop)) { //$NON-NLS-1$
 				nc = String.format("%08x", ++requestCount); //$NON-NLS-1$
 				response = KD(H(A1), nonce + ":" + nc + ":" + cnonce + ":" //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
 						+ qop + ":" //$NON-NLS-1$
 						+ H(A2));
 			} else {
 				nc = null;
 				response = KD(H(A1), nonce + ":" + H(A2)); //$NON-NLS-1$
 			}
 			r.put("response", response); //$NON-NLS-1$
 			if (params.containsKey("algorithm")) //$NON-NLS-1$
 				r.put("algorithm", "MD5"); //$NON-NLS-1$ //$NON-NLS-2$
 			if (cnonce != null && qop != null)
 				r.put("cnonce", cnonce); //$NON-NLS-1$
 			if (params.containsKey("opaque")) //$NON-NLS-1$
 				r.put("opaque", params.get("opaque")); //$NON-NLS-1$ //$NON-NLS-2$
 			if (qop != null)
 				r.put("qop", qop); //$NON-NLS-1$
 			if (nc != null)
 				r.put("nc", nc); //$NON-NLS-1$
 
 			StringBuilder v = new StringBuilder();
 			for (Map.Entry<String, String> e : r.entrySet()) {
 				if (v.length() > 0)
 					v.append(", "); //$NON-NLS-1$
 				v.append(e.getKey());
 				v.append('=');
 				v.append('"');
 				v.append(e.getValue());
 				v.append('"');
 			}
 			conn.setRequestProperty(HDR_AUTHORIZATION, type.getSchemeName()
 					+ " " + v); //$NON-NLS-1$
 		}
 
 		private static String uri(URL u) {
 			StringBuilder r = new StringBuilder();
 			r.append(u.getProtocol());
 			r.append("://"); //$NON-NLS-1$
 			r.append(u.getHost());
 			if (0 < u.getPort()) {
 				if (u.getPort() == 80 && "http".equals(u.getProtocol())) { //$NON-NLS-1$
 					/* nothing */
 				} else if (u.getPort() == 443
 						&& "https".equals(u.getProtocol())) { //$NON-NLS-1$
 					/* nothing */
 				} else {
 					r.append(':').append(u.getPort());
 				}
 			}
 			r.append(u.getPath());
 			if (u.getQuery() != null)
 				r.append('?').append(u.getQuery());
 			return r.toString();
 		}
 
 		private static String H(String data) {
 			try {
 				MessageDigest md = newMD5();
 				md.update(data.getBytes("UTF-8")); //$NON-NLS-1$
 				return LHEX(md.digest());
 			} catch (UnsupportedEncodingException e) {
 				throw new RuntimeException("UTF-8 encoding not available", e); //$NON-NLS-1$
 			}
 		}
 
 		private static String KD(String secret, String data) {
 			try {
 				MessageDigest md = newMD5();
 				md.update(secret.getBytes("UTF-8")); //$NON-NLS-1$
 				md.update((byte) ':');
 				md.update(data.getBytes("UTF-8")); //$NON-NLS-1$
 				return LHEX(md.digest());
 			} catch (UnsupportedEncodingException e) {
 				throw new RuntimeException("UTF-8 encoding not available", e); //$NON-NLS-1$
 			}
 		}
 
 		private static MessageDigest newMD5() {
 			try {
 				return MessageDigest.getInstance("MD5"); //$NON-NLS-1$
 			} catch (NoSuchAlgorithmException e) {
 				throw new RuntimeException("No MD5 available", e); //$NON-NLS-1$
 			}
 		}
 
 		private static final char[] LHEX = { '0', '1', '2', '3', '4', '5', '6',
 				'7', '8', '9', //
 				'a', 'b', 'c', 'd', 'e', 'f' };
 
 		private static String LHEX(byte[] bin) {
 			StringBuilder r = new StringBuilder(bin.length * 2);
 			for (int i = 0; i < bin.length; i++) {
 				byte b = bin[i];
 				r.append(LHEX[(b >>> 4) & 0x0f]);
 				r.append(LHEX[b & 0x0f]);
 			}
 			return r.toString();
 		}
 
 		private static Map<String, String> parse(String auth) {
 			Map<String, String> p = new HashMap<String, String>();
 			int next = 0;
 			while (next < auth.length()) {
 				if (next < auth.length() && auth.charAt(next) == ',') {
 					next++;
 				}
 				while (next < auth.length()
 						&& Character.isWhitespace(auth.charAt(next))) {
 					next++;
 				}
 
 				int eq = auth.indexOf('=', next);
 				if (eq < 0 || eq + 1 == auth.length()) {
 					return Collections.emptyMap();
 				}
 
 				final String name = auth.substring(next, eq);
 				final String value;
 				if (auth.charAt(eq + 1) == '"') {
 					int dq = auth.indexOf('"', eq + 2);
 					if (dq < 0) {
 						return Collections.emptyMap();
 					}
 					value = auth.substring(eq + 2, dq);
 					next = dq + 1;
 
 				} else {
 					int space = auth.indexOf(' ', eq + 1);
 					int comma = auth.indexOf(',', eq + 1);
 					if (space < 0)
 						space = auth.length();
 					if (comma < 0)
 						comma = auth.length();
 
 					final int e = Math.min(space, comma);
 					value = auth.substring(eq + 1, e);
 					next = e + 1;
 				}
 				p.put(name, value);
 			}
 			return p;
 		}
 	}
 
 	private static class Negotiate extends HttpAuthMethod {
 		private static final GSSManagerFactory GSS_MANAGER_FACTORY = GSSManagerFactory
 				.detect();
 
 		private static final Oid OID;
 		static {
 			try {
 				// OID for SPNEGO
 				OID = new Oid("1.3.6.1.5.5.2"); //$NON-NLS-1$
 			} catch (GSSException e) {
 				throw new Error("Cannot create NEGOTIATE oid.", e); //$NON-NLS-1$
 			}
 		}
 
 		private final byte[] prevToken;
 
 		public Negotiate(String hdr) {
 			super(Type.NEGOTIATE);
 			prevToken = Base64.decode(hdr);
 		}
 
 		@Override
 		void authorize(String user, String pass) {
 			// not used
 		}
 
 		@Override
 		void configureRequest(HttpConnection conn) throws IOException {
 			GSSManager gssManager = GSS_MANAGER_FACTORY.newInstance(conn
 					.getURL());
 			String host = conn.getURL().getHost();
 			String peerName = "HTTP@" + host.toLowerCase(); //$NON-NLS-1$
 			try {
 				GSSName gssName = gssManager.createName(peerName,
 						GSSName.NT_HOSTBASED_SERVICE);
 				GSSContext context = gssManager.createContext(gssName, OID,
 						null, GSSContext.DEFAULT_LIFETIME);
 				// Respect delegation policy in HTTP/SPNEGO.
 				context.requestCredDeleg(true);
 
 				byte[] token = context.initSecContext(prevToken, 0,
 						prevToken.length);
 
 				conn.setRequestProperty(HDR_AUTHORIZATION, getType().getSchemeName()
 						+ " " + Base64.encodeBytes(token)); //$NON-NLS-1$
 			} catch (GSSException e) {
 				IOException ioe = new IOException();
 				ioe.initCause(e);
 				throw ioe;
 			}
 		}
 	}
 }