/*
 * Copyright 2004 - 2013 Wayne Grant
 *           2013 - 2025 Kai Kramer
 *
 * This file is part of KeyStore Explorer.
 *
 * KeyStore Explorer is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * KeyStore Explorer is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with KeyStore Explorer.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.kse.crypto.signing;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.math.BigInteger;
import java.net.URL;
import java.net.URLConnection;
import java.security.KeyManagementException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.cert.X509Certificate;

import javax.net.ssl.HttpsURLConnection;
import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLSocketFactory;
import javax.net.ssl.TrustManager;
import javax.net.ssl.X509TrustManager;

import org.apache.commons.io.IOUtils;
import org.bouncycastle.asn1.ASN1ObjectIdentifier;
import org.bouncycastle.asn1.cmp.PKIFailureInfo;
import org.bouncycastle.tsp.TSPException;
import org.bouncycastle.tsp.TimeStampRequest;
import org.bouncycastle.tsp.TimeStampRequestGenerator;
import org.bouncycastle.tsp.TimeStampResponse;
import org.bouncycastle.tsp.TimeStampToken;
import org.bouncycastle.util.encoders.Base64;
import org.kse.crypto.digest.DigestType;

public class TimeStampingClient {

    private TimeStampingClient() {
    }

    /**
     * Get RFC 3161 timeStampToken.
     *
     * @param tsaUrl  Location of TSA
     * @param data    The data to be time-stamped
     * @param hashAlg The algorithm used for generating a hash value of the data to be time-stamped
     * @return encoded, TSA signed data of the timeStampToken
     * @throws IOException when request to TSA server fails
     */
    public static byte[] getTimeStampToken(String tsaUrl, byte[] data, DigestType hashAlg) throws IOException {

        TimeStampResponse response = null;
        try {

            // calculate hash value
            MessageDigest digest = MessageDigest.getInstance(hashAlg.jce());
            byte[] hashValue = digest.digest(data);

            // Set up the time stamp request
            TimeStampRequestGenerator tsqGenerator = new TimeStampRequestGenerator();
            tsqGenerator.setCertReq(true);
            BigInteger nonce = BigInteger.valueOf(System.currentTimeMillis());
            TimeStampRequest request = tsqGenerator.generate(new ASN1ObjectIdentifier(hashAlg.oid()), hashValue, nonce);
            byte[] requestBytes = request.getEncoded();

            // send http request
            byte[] respBytes = queryServer(tsaUrl, requestBytes);

            // process response
            response = new TimeStampResponse(respBytes);

            // validate communication level attributes (RFC 3161 PKIStatus)
            response.validate(request);
            PKIFailureInfo failure = response.getFailInfo();
            int value = failure == null ? 0 : failure.intValue();
            if (value != 0) {
                throw new IOException("Server returned error code: " + value);
            }
        } catch (NoSuchAlgorithmException | TSPException e) {
            throw new IOException(e);
        }

        // extract the time stamp token
        TimeStampToken tsToken = response.getTimeStampToken();
        if (tsToken == null) {
            throw new IOException("TSA returned no time stamp token: " + response.getStatusString());
        }

        return tsToken.getEncoded();
    }

    /**
     * Get timestamp token (HTTP communication)
     *
     * @return TSA response, raw bytes (RFC 3161 encoded)
     * @throws IOException when request to TSA server fails
     */
    private static byte[] queryServer(String tsaUrl, byte[] requestBytes) throws IOException {

        // Install the all-trusting trust manager
        SSLContext sc;
        try {
            sc = SSLContext.getInstance("SSL");
            sc.init(null, new TrustManager[] { new X509TrustManager() {
                @Override
                public java.security.cert.X509Certificate[] getAcceptedIssuers() {
                    return null;
                }

                @Override
                public void checkClientTrusted(X509Certificate[] certs, String authType) {
                }

                @Override
                public void checkServerTrusted(X509Certificate[] certs, String authType) {
                }
            } }, new java.security.SecureRandom());
        } catch (NoSuchAlgorithmException | KeyManagementException e) {
            throw new IOException(e);
        }
        SSLSocketFactory defaultSSLSocketFactory = HttpsURLConnection.getDefaultSSLSocketFactory();
        HttpsURLConnection.setDefaultSSLSocketFactory(sc.getSocketFactory());

        try {
            URL url = new URL(tsaUrl);
            URLConnection con = url.openConnection();
            con.setDoInput(true);
            con.setDoOutput(true);
            con.setUseCaches(false);
            con.setRequestProperty("Content-Type", "application/timestamp-query");
            con.setRequestProperty("Content-Transfer-Encoding", "binary");

            OutputStream out = con.getOutputStream();
            out.write(requestBytes);
            out.close();

            InputStream is = con.getInputStream();
            byte[] respBytes = IOUtils.toByteArray(is);
            String encoding = con.getContentEncoding();
            if (encoding != null && encoding.equalsIgnoreCase("base64")) {
                respBytes = Base64.decode(new String(respBytes));
            }
            return respBytes;

        } finally {
            // restore default trust manager
            HttpsURLConnection.setDefaultSSLSocketFactory(defaultSSLSocketFactory);
        }
    }
}
