package org.apache.archiva.redback.rest.services.interceptors;
/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */


import org.apache.archiva.redback.configuration.UserConfiguration;
import org.apache.cxf.jaxrs.utils.JAXRSUtils;
import org.apache.cxf.message.Message;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Service;

import javax.annotation.PostConstruct;
import javax.inject.Inject;
import javax.inject.Named;
import javax.servlet.http.HttpServletRequest;
import javax.ws.rs.container.ContainerRequestContext;
import javax.ws.rs.container.ContainerRequestFilter;
import javax.ws.rs.core.Response;
import javax.ws.rs.ext.Provider;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;

/**
 * Created by Martin Stockhammer on 19.01.17.
 *
 * This interceptor tries to check if requests come from a valid origin and
 * are not generated by another site on behalf of the real client.
 *
 * We are using some of the techniques mentioned in
 * https://www.owasp.org/index.php/Cross-Site_Request_Forgery_(CSRF)_Prevention_Cheat_Sheet
 *
 * Try to find Origin and Referer of the request.
 * Match them to the target address, that may be either statically configured or is determined
 * by the Host/X-Forwarded-For Header.
 *
 *
 */
@Provider
@Service( "requestValidationInterceptor#rest" )
public class RequestValidationInterceptor extends AbstractInterceptor implements ContainerRequestFilter {


    private static final String X_FORWARDED_PROTO = "X-Forwarded-Proto";
    private static final String X_FORWARDED_HOST = "X-Forwarded-Host";
    private static final String ORIGIN = "Origin";
    private static final String REFERER = "Referer";
    private static final String CFG_REST_BASE_URL = "rest.baseUrl";
    private static final String CFG_REST_CSRF_ABSENTORIGIN_DENY = "rest.csrffilter.absentorigin.deny";
    private static final String CFG_REST_CSRF_ENABLED = "rest.csrffilter.enabled";

    private final Logger log = LoggerFactory.getLogger( getClass() );

    private boolean enabled = true;
    private boolean useStaticUrl = false;
    private boolean denyAbsentHeaders = true;
    private URL baseUrl;
    private HttpServletRequest httpRequest = null;

    private UserConfiguration config;

    @Inject
    public RequestValidationInterceptor(@Named( value = "userConfiguration#default" )
                                                        UserConfiguration config) {
        this.config = config;
    }

    @PostConstruct
    public void init() {
        String baseUrlStr = config.getString(CFG_REST_BASE_URL, "");
        if (!"".equals(baseUrlStr.trim())) {
            try {
                baseUrl = new URL(baseUrlStr);
                useStaticUrl = true;
            } catch (MalformedURLException ex) {
                log.error("Configured baseUrl (rest.baseUrl={}) is invalid. Message: {}", baseUrlStr, ex.getMessage());
            }
        } else {
            useStaticUrl = false;
        }
        denyAbsentHeaders = config.getBoolean(CFG_REST_CSRF_ABSENTORIGIN_DENY,true);
        enabled = config.getBoolean(CFG_REST_CSRF_ENABLED,true);
        if (!enabled) {
            log.info("CSRF Filter is disabled by configuration");
        }
    }

    @Override
    public void filter(ContainerRequestContext containerRequestContext) throws IOException {
        if (enabled) {
            HttpServletRequest request = getRequest();
            URL targetUrl = getTargetUrl(request);
            if (targetUrl == null) {
                log.error("Could not verify target URL.");
                containerRequestContext.abortWith(Response.status(Response.Status.FORBIDDEN).build());
            }
            if (!checkSourceRequestHeader(targetUrl, request)) {
                log.warn("HTTP Header check failed. Assuming CSRF attack.");
                containerRequestContext.abortWith(Response.status(Response.Status.FORBIDDEN).build());
            }
        }
    }

    private HttpServletRequest getRequest() {
        if (httpRequest!=null) {
            return httpRequest;
        }  else {
            Message message = JAXRSUtils.getCurrentMessage();
            return getHttpServletRequest(message);
        }
    }

    private URL getTargetUrl(HttpServletRequest request) {
        if (useStaticUrl) {
            return baseUrl;
        } else {
            URL requestUrl;
            try {
                requestUrl = new URL(request.getRequestURL().toString());
            } catch (MalformedURLException ex) {
                log.error("Bad Request URL {}, Message: {}", request.getRequestURL(), ex.getMessage());
                return null;
            }
            String xforwarded = request.getHeader(X_FORWARDED_HOST);
            String xforwardedProto = request.getHeader(X_FORWARDED_PROTO);
            if (xforwardedProto==null) {
                xforwardedProto=requestUrl.getProtocol();
            }
            if (xforwarded!=null) {
                try {
                    return new URL(xforwardedProto+"://"+xforwarded);
                } catch (MalformedURLException ex) {
                    log.warn("X-Forwarded-Host Header is malformed: {}", ex.getMessage());
                }
            }
            return requestUrl;
        }
    }

    private int getPort(final URL url) {
        return url.getPort() > 0 ? url.getPort() : url.getDefaultPort();
    }

    private boolean checkSourceRequestHeader(final URL targetUrl, final HttpServletRequest request) {
        boolean headerFound=false;
        String origin = request.getHeader(ORIGIN);
        int targetPort = getPort(targetUrl);
        if (origin!=null) {
            try {
                URL originUrl = new URL(origin);
                headerFound=true;
                log.debug("Origin Header URL found: {}", originUrl);
                if (!targetUrl.getProtocol().equals(originUrl.getProtocol())) {
                    log.warn("Origin Header Protocol does not match originUrl={}, targetUrl={}",  originUrl, targetUrl);
                    return false;
                }
                if (!targetUrl.getHost().equals(originUrl.getHost())) {
                    log.warn("Origin Header Host does not match originUrl={}, targetUrl={}",originUrl,targetUrl);
                    return false;
                }
                int originPort = getPort(originUrl);
                if (targetPort != originPort) {
                    log.warn("Origin Header Port does not match originUrl={}, targetUrl={}",originUrl,targetUrl);
                    return false;
                }
            } catch (MalformedURLException ex) {
                log.warn("Bad URL in Origin HTTP-Header: {}. Message: {}",origin, ex.getMessage());
                return false;
            }
        }
        String referer = request.getHeader(REFERER);
        if (referer!=null) {
            try {
                URL refererUrl = new URL(referer);
                headerFound=true;
                log.debug("Referer Header URL found: {}",refererUrl);
                if (!targetUrl.getHost().equals(refererUrl.getHost())) {
                    log.warn("Referer Header Host does not match refererUrl={}, targetUrl={}",refererUrl,targetUrl);
                    return false;
                }
                int refererPort = getPort(refererUrl);
                if (targetPort != refererPort) {
                    log.warn("Referer Header Port does not match refererUrl={}, targetUrl={}",refererUrl,targetUrl);
                    return false;
                }
            } catch (MalformedURLException ex) {
                log.warn("Bad URL in Referer HTTP-Header: {}, Message: {}", referer, ex.getMessage());
                return false;
            }
        }
        if (!headerFound && denyAbsentHeaders) {
            log.warn("Neither Origin nor Referer header found. Request is denied.");
            return false;
        }
        return true;
    }

    public void setHttpRequest(HttpServletRequest request) {
        this.httpRequest = request;
    }
}