/*
 * JBoss, Home of Professional Open Source.
 * Copyright 2014 Red Hat, Inc., and individual contributors
 * as indicated by the @author tags.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package io.undertow.server.handlers;

import io.undertow.UndertowLogger;
import io.undertow.server.BasicSSLSessionInfo;
import io.undertow.server.ExchangeCompletionListener;
import io.undertow.server.HandlerWrapper;
import io.undertow.server.HttpHandler;
import io.undertow.server.HttpServerExchange;
import io.undertow.server.SSLSessionInfo;
import io.undertow.server.handlers.builder.HandlerBuilder;
import io.undertow.util.Certificates;
import io.undertow.util.HeaderMap;

import javax.security.cert.CertificateException;

import static io.undertow.util.Headers.SSL_CIPHER;
import static io.undertow.util.Headers.SSL_CLIENT_CERT;
import static io.undertow.util.Headers.SSL_SESSION_ID;

import java.util.Collections;
import java.util.Map;
import java.util.Set;

Handler that sets SSL information on the connection based on the following headers:


SSL_CLIENT_CERT
SSL_CIPHER
SSL_SESSION_ID


If this handler is present in the chain it will always override the SSL session information,
even if these headers are not present.

This handler MUST only be used on servers that are behind a reverse proxy, where the reverse proxy
has been configured to always set these header for EVERY request (or strip existing headers with these
names if no SSL information is present). Otherwise it may be possible for a malicious client to spoof
a SSL connection.
Author:
Stuart Douglas/**
 * Handler that sets SSL information on the connection based on the following headers:
 * <p>
 * <ul>
 * <li>SSL_CLIENT_CERT</li>
 * <li>SSL_CIPHER</li>
 * <li>SSL_SESSION_ID</li>
 * </ul>
 * <p>
 * If this handler is present in the chain it will always override the SSL session information,
 * even if these headers are not present.
 * <p>
 * This handler MUST only be used on servers that are behind a reverse proxy, where the reverse proxy
 * has been configured to always set these header for EVERY request (or strip existing headers with these
 * names if no SSL information is present). Otherwise it may be possible for a malicious client to spoof
 * a SSL connection.
 *
 * @author Stuart Douglas
 */
public class SSLHeaderHandler implements HttpHandler {

    public static final String HTTPS = "https";

    private static final ExchangeCompletionListener CLEAR_SSL_LISTENER = new ExchangeCompletionListener() {
        @Override
        public void exchangeEvent(HttpServerExchange exchange, NextListener nextListener) {
            exchange.getConnection().setSslSessionInfo(null);
            nextListener.proceed();
        }
    };

    private final HttpHandler next;

    public SSLHeaderHandler(HttpHandler next) {
        this.next = next;
    }

    @Override
    public void handleRequest(HttpServerExchange exchange) throws Exception {
        HeaderMap requestHeaders = exchange.getRequestHeaders();
        final String sessionId = requestHeaders.getFirst(SSL_SESSION_ID);
        final String cipher = requestHeaders.getFirst(SSL_CIPHER);
        String clientCert = requestHeaders.getFirst(SSL_CLIENT_CERT);
        //the proxy client replaces \n with ' '
        if (clientCert != null && clientCert.length() > 28) {
            StringBuilder sb = new StringBuilder(clientCert.length() + 1);
            sb.append(Certificates.BEGIN_CERT);
            sb.append('\n');
            sb.append(clientCert.replace(' ', '\n').substring(28, clientCert.length() - 26));//core certificate data
            sb.append('\n');
            sb.append(Certificates.END_CERT);
            clientCert = sb.toString();
        }
        if (clientCert != null || sessionId != null || cipher != null) {
            try {
                SSLSessionInfo info = new BasicSSLSessionInfo(sessionId, cipher, clientCert);
                exchange.setRequestScheme(HTTPS);
                exchange.getConnection().setSslSessionInfo(info);
                exchange.addExchangeCompleteListener(CLEAR_SSL_LISTENER);
            } catch (java.security.cert.CertificateException | CertificateException e) {
                UndertowLogger.REQUEST_LOGGER.debugf(e, "Could not create certificate from header %s", clientCert);
            }
        }
        next.handleRequest(exchange);
    }



    public static class Builder implements HandlerBuilder {

        @Override
        public String name() {
            return "ssl-headers";
        }

        @Override
        public Map<String, Class<?>> parameters() {
            return Collections.emptyMap();
        }

        @Override
        public Set<String> requiredParameters() {
            return Collections.emptySet();
        }

        @Override
        public String defaultParameter() {
            return null;
        }

        @Override
        public HandlerWrapper build(Map<String, Object> config) {
            return new Wrapper();
        }

    }

    private static class Wrapper implements HandlerWrapper {
        @Override
        public HttpHandler wrap(HttpHandler handler) {
            return new SSLHeaderHandler(handler);
        }
    }
}