/*
 * Copyright (c) 2004, PostgreSQL Global Development Group
 * See the LICENSE file in the project root for more information.
 */

package org.postgresql.ssl;

import org.postgresql.util.GT;

import java.io.BufferedInputStream;
import java.io.ByteArrayInputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.security.GeneralSecurityException;
import java.security.KeyStore;
import java.security.cert.CertificateException;
import java.security.cert.CertificateFactory;
import java.security.cert.X509Certificate;
import java.util.UUID;

import javax.net.ssl.SSLContext;
import javax.net.ssl.TrustManager;
import javax.net.ssl.TrustManagerFactory;
import javax.net.ssl.X509TrustManager;

Provides a SSLSocketFactory that authenticates the remote server against an explicit pre-shared
SSL certificate. This is more secure than using the NonValidatingFactory as it prevents "man in
the middle" attacks. It is also more secure than relying on a central CA signing your server's
certificate as it pins the server's certificate.
This class requires a single String parameter specified by setting the connection property
sslfactoryarg. The value of this property is the PEM-encoded remote server's SSL
certificate.
Where the certificate is loaded from is based upon the prefix of the sslfactoryarg property.
The following table lists the valid set of prefixes.


    
Prefix
    
Example
    
Explanation


    
classpath:
    
classpath:ssl/server.crt
    
Loaded from the classpath.


    
file:
    
file:/foo/bar/server.crt
    
Loaded from the filesystem.


    
env:
    
env:mydb_cert
    
Loaded from string value of the mydb_cert environment variable.


    
sys:
    
sys:mydb_cert
    
Loaded from string value of the mydb_cert system property.


    
-----BEGIN CERTIFICATE------
    

        
-----BEGIN CERTIFICATE-----
MIIDQzCCAqygAwIBAgIJAOd1tlfiGoEoMA0GCSqGSIb3DQEBBQUAMHUxCzAJBgNV
[... truncated ...]
UCmmYqgiVkAGWRETVo+byOSDZ4swb10=
-----END CERTIFICATE-----
        
     
    
Loaded from string value of the argument.


/**
 * <p>Provides a SSLSocketFactory that authenticates the remote server against an explicit pre-shared
 * SSL certificate. This is more secure than using the NonValidatingFactory as it prevents "man in
 * the middle" attacks. It is also more secure than relying on a central CA signing your server's
 * certificate as it pins the server's certificate.</p>
 *
 * <p>This class requires a single String parameter specified by setting the connection property
 * <code>sslfactoryarg</code>. The value of this property is the PEM-encoded remote server's SSL
 * certificate.</p>
 *
 * <p>Where the certificate is loaded from is based upon the prefix of the <code>sslfactoryarg</code> property.
 * The following table lists the valid set of prefixes.</p>
 *
 * <table border="1" summary="Valid prefixes for sslfactoryarg">
 * <tr>
 *     <th>Prefix</th>
 *     <th>Example</th>
 *     <th>Explanation</th>
 * </tr>
 * <tr>
 *     <td><code>classpath:</code></td>
 *     <td><code>classpath:ssl/server.crt</code></td>
 *     <td>Loaded from the classpath.</td>
 * </tr>
 * <tr>
 *     <td><code>file:</code></td>
 *     <td><code>file:/foo/bar/server.crt</code></td>
 *     <td>Loaded from the filesystem.</td>
 * </tr>
 * <tr>
 *     <td><code>env:</code></td>
 *     <td><code>env:mydb_cert</code></td>
 *     <td>Loaded from string value of the <code>mydb_cert</code> environment variable.</td>
 * </tr>
 * <tr>
 *     <td><code>sys:</code></td>
 *     <td><code>sys:mydb_cert</code></td>
 *     <td>Loaded from string value of the <code>mydb_cert</code> system property.</td>
 * </tr>
 * <tr>
 *     <td><pre>-----BEGIN CERTIFICATE------</pre></td>
 *     <td>
 *         <pre>
 * -----BEGIN CERTIFICATE-----
 * MIIDQzCCAqygAwIBAgIJAOd1tlfiGoEoMA0GCSqGSIb3DQEBBQUAMHUxCzAJBgNV
 * [... truncated ...]
 * UCmmYqgiVkAGWRETVo+byOSDZ4swb10=
 * -----END CERTIFICATE-----
 *         </pre>
*      </td>
 *     <td>Loaded from string value of the argument.</td>
 * </tr>
 * </table>
 */

public class SingleCertValidatingFactory extends WrappedFactory {
  private static final String FILE_PREFIX = "file:";
  private static final String CLASSPATH_PREFIX = "classpath:";
  private static final String ENV_PREFIX = "env:";
  private static final String SYS_PROP_PREFIX = "sys:";

  public SingleCertValidatingFactory(String sslFactoryArg) throws GeneralSecurityException {
    if (sslFactoryArg == null || sslFactoryArg.equals("")) {
      throw new GeneralSecurityException(GT.tr("The sslfactoryarg property may not be empty."));
    }
    InputStream in = null;
    try {
      if (sslFactoryArg.startsWith(FILE_PREFIX)) {
        String path = sslFactoryArg.substring(FILE_PREFIX.length());
        in = new BufferedInputStream(new FileInputStream(path));
      } else if (sslFactoryArg.startsWith(CLASSPATH_PREFIX)) {
        String path = sslFactoryArg.substring(CLASSPATH_PREFIX.length());
        in = new BufferedInputStream(
            Thread.currentThread().getContextClassLoader().getResourceAsStream(path));
      } else if (sslFactoryArg.startsWith(ENV_PREFIX)) {
        String name = sslFactoryArg.substring(ENV_PREFIX.length());
        String cert = System.getenv(name);
        if (cert == null || "".equals(cert)) {
          throw new GeneralSecurityException(GT.tr(
              "The environment variable containing the server's SSL certificate must not be empty."));
        }
        in = new ByteArrayInputStream(cert.getBytes("UTF-8"));
      } else if (sslFactoryArg.startsWith(SYS_PROP_PREFIX)) {
        String name = sslFactoryArg.substring(SYS_PROP_PREFIX.length());
        String cert = System.getProperty(name);
        if (cert == null || "".equals(cert)) {
          throw new GeneralSecurityException(GT.tr(
              "The system property containing the server's SSL certificate must not be empty."));
        }
        in = new ByteArrayInputStream(cert.getBytes("UTF-8"));
      } else if (sslFactoryArg.startsWith("-----BEGIN CERTIFICATE-----")) {
        in = new ByteArrayInputStream(sslFactoryArg.getBytes("UTF-8"));
      } else {
        throw new GeneralSecurityException(GT.tr(
            "The sslfactoryarg property must start with the prefix file:, classpath:, env:, sys:, or -----BEGIN CERTIFICATE-----."));
      }

      SSLContext ctx = SSLContext.getInstance("TLS");
      ctx.init(null, new TrustManager[]{new SingleCertTrustManager(in)}, null);
      factory = ctx.getSocketFactory();
    } catch (RuntimeException e) {
      throw e;
    } catch (Exception e) {
      if (e instanceof GeneralSecurityException) {
        throw (GeneralSecurityException) e;
      }
      throw new GeneralSecurityException(GT.tr("An error occurred reading the certificate"), e);
    } finally {
      if (in != null) {
        try {
          in.close();
        } catch (Exception e2) {
          // ignore
        }
      }
    }
  }

  public static class SingleCertTrustManager implements X509TrustManager {
    X509Certificate cert;
    X509TrustManager trustManager;

    public SingleCertTrustManager(InputStream in) throws IOException, GeneralSecurityException {
      KeyStore ks = KeyStore.getInstance(KeyStore.getDefaultType());
      // Note: KeyStore requires it be loaded even if you don't load anything into it:
      ks.load(null);
      CertificateFactory cf = CertificateFactory.getInstance("X509");
      cert = (X509Certificate) cf.generateCertificate(in);
      ks.setCertificateEntry(UUID.randomUUID().toString(), cert);
      TrustManagerFactory tmf =
          TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
      tmf.init(ks);
      for (TrustManager tm : tmf.getTrustManagers()) {
        if (tm instanceof X509TrustManager) {
          trustManager = (X509TrustManager) tm;
          break;
        }
      }
      if (trustManager == null) {
        throw new GeneralSecurityException(GT.tr("No X509TrustManager found"));
      }
    }

    public void checkClientTrusted(X509Certificate[] chain, String authType)
        throws CertificateException {
    }

    public void checkServerTrusted(X509Certificate[] chain, String authType)
        throws CertificateException {
      trustManager.checkServerTrusted(chain, authType);
    }

    public X509Certificate[] getAcceptedIssuers() {
      return new X509Certificate[]{cert};
    }
  }
}