/*
 * 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.
 */
package org.apache.catalina.valves;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.security.NoSuchProviderException;
import java.security.cert.CertificateFactory;
import java.security.cert.X509Certificate;

import jakarta.servlet.ServletException;

import org.apache.catalina.Globals;
import org.apache.catalina.connector.Request;
import org.apache.catalina.connector.Response;
import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;

When using mod_proxy_http, the client SSL information is not included in the
protocol (unlike mod_jk and mod_proxy_ajp). To make the client SSL
information available to Tomcat, some additional configuration is required.
In httpd, mod_headers is used to add the SSL information as HTTP headers. In
Tomcat, this valve is used to read the information from the HTTP headers and
insert it into the request.

Note: Ensure that the headers are always set by httpd for all requests to
prevent a client spoofing SSL information by sending fake headers. 

In httpd.conf add the following:
<IfModule ssl_module>
  RequestHeader set SSL_CLIENT_CERT "%{SSL_CLIENT_CERT}s"
  RequestHeader set SSL_CIPHER "%{SSL_CIPHER}s"
  RequestHeader set SSL_SESSION_ID "%{SSL_SESSION_ID}s"
  RequestHeader set SSL_CIPHER_USEKEYSIZE "%{SSL_CIPHER_USEKEYSIZE}s"
</IfModule>

In server.xml, configure this valve under the Engine element in server.xml:
<Engine ...>
  <Valve className="org.apache.catalina.valves.SSLValve" />
  <Host ... />
</Engine>

/**
 * When using mod_proxy_http, the client SSL information is not included in the
 * protocol (unlike mod_jk and mod_proxy_ajp). To make the client SSL
 * information available to Tomcat, some additional configuration is required.
 * In httpd, mod_headers is used to add the SSL information as HTTP headers. In
 * Tomcat, this valve is used to read the information from the HTTP headers and
 * insert it into the request.<p>
 *
 * <b>Note: Ensure that the headers are always set by httpd for all requests to
 * prevent a client spoofing SSL information by sending fake headers. </b><p>
 *
 * In httpd.conf add the following:
 * <pre>
 * &lt;IfModule ssl_module&gt;
 *   RequestHeader set SSL_CLIENT_CERT "%{SSL_CLIENT_CERT}s"
 *   RequestHeader set SSL_CIPHER "%{SSL_CIPHER}s"
 *   RequestHeader set SSL_SESSION_ID "%{SSL_SESSION_ID}s"
 *   RequestHeader set SSL_CIPHER_USEKEYSIZE "%{SSL_CIPHER_USEKEYSIZE}s"
 * &lt;/IfModule&gt;
 * </pre>
 *
 * In server.xml, configure this valve under the Engine element in server.xml:
 * <pre>
 * &lt;Engine ...&gt;
 *   &lt;Valve className="org.apache.catalina.valves.SSLValve" /&gt;
 *   &lt;Host ... /&gt;
 * &lt;/Engine&gt;
 * </pre>
 */
public class SSLValve extends ValveBase {

    private static final Log log = LogFactory.getLog(SSLValve.class);

    private String sslClientCertHeader = "ssl_client_cert";
    private String sslCipherHeader = "ssl_cipher";
    private String sslSessionIdHeader = "ssl_session_id";
    private String sslCipherUserKeySizeHeader = "ssl_cipher_usekeysize";

    //------------------------------------------------------ Constructor
    public SSLValve() {
        super(true);
    }


    public String getSslClientCertHeader() {
        return sslClientCertHeader;
    }

    public void setSslClientCertHeader(String sslClientCertHeader) {
        this.sslClientCertHeader = sslClientCertHeader;
    }

    public String getSslCipherHeader() {
        return sslCipherHeader;
    }

    public void setSslCipherHeader(String sslCipherHeader) {
        this.sslCipherHeader = sslCipherHeader;
    }

    public String getSslSessionIdHeader() {
        return sslSessionIdHeader;
    }

    public void setSslSessionIdHeader(String sslSessionIdHeader) {
        this.sslSessionIdHeader = sslSessionIdHeader;
    }

    public String getSslCipherUserKeySizeHeader() {
        return sslCipherUserKeySizeHeader;
    }

    public void setSslCipherUserKeySizeHeader(String sslCipherUserKeySizeHeader) {
        this.sslCipherUserKeySizeHeader = sslCipherUserKeySizeHeader;
    }


    public String mygetHeader(Request request, String header) {
        String strcert0 = request.getHeader(header);
        if (strcert0 == null) {
            return null;
        }
        /* mod_header writes "(null)" when the ssl variable is no filled */
        if ("(null)".equals(strcert0)) {
            return null;
        }
        return strcert0;
    }


    @Override
    public void invoke(Request request, Response response) throws IOException, ServletException {
        /*
         * Known behaviours of reverse proxies that are handled by the
         * processing below:
         * - mod_header converts the '\n' into ' '
         * - nginx converts the '\n' into multiple ' '
         *
         * The code assumes that the trimmed header value starts with
         * '-----BEGIN CERTIFICATE-----' and ends with
         * '-----END CERTIFICATE-----'.
         *
         * Note: As long as the BEGIN marker and the rest of the content are on
         *       separate lines, the CertificateFactory is tolerant of any
         *       additional whitespace.
         */
        String headerValue = mygetHeader(request, sslClientCertHeader);
        if (headerValue != null) {
            headerValue = headerValue.trim();
            if (headerValue.length() > 27) {
                String body = headerValue.substring(27);
                String header = "-----BEGIN CERTIFICATE-----\n";
                String strcerts = header.concat(body);
                ByteArrayInputStream bais = new ByteArrayInputStream(
                        strcerts.getBytes(StandardCharsets.ISO_8859_1));
                X509Certificate jsseCerts[] = null;
                String providerName = (String) request.getConnector().getProperty(
                        "clientCertProvider");
                try {
                    CertificateFactory cf;
                    if (providerName == null) {
                        cf = CertificateFactory.getInstance("X.509");
                    } else {
                        cf = CertificateFactory.getInstance("X.509", providerName);
                    }
                    X509Certificate cert = (X509Certificate) cf.generateCertificate(bais);
                    jsseCerts = new X509Certificate[1];
                    jsseCerts[0] = cert;
                } catch (java.security.cert.CertificateException e) {
                    log.warn(sm.getString("sslValve.certError", strcerts), e);
                } catch (NoSuchProviderException e) {
                    log.error(sm.getString(
                            "sslValve.invalidProvider", providerName), e);
                }
                request.setAttribute(Globals.CERTIFICATES_ATTR, jsseCerts);
            }
        }
        headerValue = mygetHeader(request, sslCipherHeader);
        if (headerValue != null) {
            request.setAttribute(Globals.CIPHER_SUITE_ATTR, headerValue);
        }
        headerValue = mygetHeader(request, sslSessionIdHeader);
        if (headerValue != null) {
            request.setAttribute(Globals.SSL_SESSION_ID_ATTR, headerValue);
        }
        headerValue = mygetHeader(request, sslCipherUserKeySizeHeader);
        if (headerValue != null) {
            request.setAttribute(Globals.KEY_SIZE_ATTR, Integer.valueOf(headerValue));
        }
        getNext().invoke(request, response);
    }
}