java - ftp4jライブラリでSSLを使用する方法

Question

ftp4jのドキュメントが非常に軽いので、現在行き詰まっています。これによると： ドキュメント

SSL証明書を使用して接続するようにライブラリを設定できます。私が抱えている問題は、ライブラリがどのSSL証明書を受け入れ、どのSSL証明書を受け入れないかをどのように知るかを理解することです（詐欺師の場合）。何か助けはありますか？ありがとう！

編集：SSL証明書をインポートし、ライブラリが特定のSSL証明書を持つ特定のサーバーにのみ接続するようにする方法を知りたいです。

Answer 1

SunのInstallCert.javaを使用して、受け入れたい証明書を別のストアに保存することができます。次に、FTPClientをセットアップするときに、この別のストアを使用します。

Oracleが引き継いだ後、インターネット上で見つけるのがますます難しくなるので、以下のバージョンのInstallCert.javaを含めました...

/*
 * Copyright 2006 Sun Microsystems, Inc.  All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 *   - Neither the name of Sun Microsystems nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
/**
 * http://blogs.sun.com/andreas/resource/InstallCert.java
 * Use:
 * java InstallCert hostname
 * Example:
 *% java InstallCert ecc.fedora.redhat.com
 */

import javax.net.ssl.*;
import java.io.*;
import java.security.KeyStore;
import java.security.MessageDigest;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;

/**
 * Class used to add the server's certificate to the KeyStore
 * with your trusted certificates.
 */
public class InstallCert {

    public static void main(String[] args) throws Exception {
    String host;
    int port;
    char[] passphrase;
    if ((args.length == 1) || (args.length == 2)) {
        String[] c = args[0].split(":");
        host = c[0];
        port = (c.length == 1) ? 443 : Integer.parseInt(c[1]);
        String p = (args.length == 1) ? "changeit" : args[1];
        passphrase = p.toCharArray();
    } else {
        System.out.println("Usage: java InstallCert <host>[:port] [passphrase]");
        return;
    }

    File file = new File("jssecacerts");
    if (file.isFile() == false) {
        char SEP = File.separatorChar;
        File dir = new File(System.getProperty("java.home") + SEP
                + "lib" + SEP + "security");
        file = new File(dir, "jssecacerts");
        if (file.isFile() == false) {
            file = new File(dir, "cacerts");
        }
    }
    System.out.println("Loading KeyStore " + file + "...");
    InputStream in = new FileInputStream(file);
    KeyStore ks = KeyStore.getInstance(KeyStore.getDefaultType());
    ks.load(in, passphrase);
    in.close();

    SSLContext context = SSLContext.getInstance("TLS");
    TrustManagerFactory tmf =
            TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
    tmf.init(ks);
    X509TrustManager defaultTrustManager = (X509TrustManager) tmf.getTrustManagers()[0];
    SavingTrustManager tm = new SavingTrustManager(defaultTrustManager);
    context.init(null, new TrustManager[]{tm}, null);
    SSLSocketFactory factory = context.getSocketFactory();

    System.out.println("Opening connection to " + host + ":" + port + "...");
    SSLSocket socket = (SSLSocket) factory.createSocket(host, port);
    socket.setSoTimeout(10000);
    try {
        System.out.println("Starting SSL handshake...");
        socket.startHandshake();
        socket.close();
        System.out.println();
        System.out.println("No errors, certificate is already trusted");
    } catch (SSLException e) {
        System.out.println();
        e.printStackTrace(System.out);
    }

    X509Certificate[] chain = tm.chain;
    if (chain == null) {
        System.out.println("Could not obtain server certificate chain");
        return;
    }

    BufferedReader reader =
            new BufferedReader(new InputStreamReader(System.in));

    System.out.println();
    System.out.println("Server sent " + chain.length + " certificate(s):");
    System.out.println();
    MessageDigest sha1 = MessageDigest.getInstance("SHA1");
    MessageDigest md5 = MessageDigest.getInstance("MD5");
    for (int i = 0; i < chain.length; i++) {
        X509Certificate cert = chain[i];
        System.out.println
                (" " + (i + 1) + " Subject " + cert.getSubjectDN());
        System.out.println("   Issuer  " + cert.getIssuerDN());
        sha1.update(cert.getEncoded());
        System.out.println("   sha1    " + toHexString(sha1.digest()));
        md5.update(cert.getEncoded());
        System.out.println("   md5     " + toHexString(md5.digest()));
        System.out.println();
    }

    System.out.println("Enter certificate to add to trusted keystore or 'q' to quit: [1]");
    String line = reader.readLine().trim();
    int k;
    try {
        k = (line.length() == 0) ? 0 : Integer.parseInt(line) - 1;
    } catch (NumberFormatException e) {
        System.out.println("KeyStore not changed");
        return;
    }

    X509Certificate cert = chain[k];
    String alias = host + "-" + (k + 1);
    ks.setCertificateEntry(alias, cert);

    OutputStream out = new FileOutputStream("jssecacerts");
    ks.store(out, passphrase);
    out.close();

    System.out.println();
    System.out.println(cert);
    System.out.println();
        System.out.println
                ("Added certificate to keystore 'jssecacerts' using alias '"
                        + alias + "'");
    }

    private static final char[] HEXDIGITS = "0123456789abcdef".toCharArray();

    private static String toHexString(byte[] bytes) {
        StringBuilder sb = new StringBuilder(bytes.length * 3);
        for (int b : bytes) {
            b &= 0xff;
            sb.append(HEXDIGITS[b >> 4]);
            sb.append(HEXDIGITS[b & 15]);
            sb.append(' ');
        }
        return sb.toString();
    }

private static class SavingTrustManager implements X509TrustManager {

        private final X509TrustManager tm;
        private X509Certificate[] chain;

        SavingTrustManager(X509TrustManager tm) {
            this.tm = tm;
        }

        public X509Certificate[] getAcceptedIssuers() {
            throw new UnsupportedOperationException();
        }

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

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

そのコードは、提供する新しい証明書を追加する前に、JREによって提供される証明書のコピーを作成します。それを望まず、代わりに証明書のみを保存する場合は、次の部分を削除する必要があります。

if (file.isFile() == false) {
        char SEP = File.separatorChar;
        File dir = new File(System.getProperty("java.home") + SEP
                + "lib" + SEP + "security");
        file = new File(dir, "jssecacerts");
        if (file.isFile() == false) {
            file = new File(dir, "cacerts");
        }
    }

これで、証明書を含むファイルがある場合、これを使用して、FTPClientに提供するSSLSocketFactoryを作成できます。

次のような証明書マネージャーを作成できます。

import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
import java.security.KeyStore;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;

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

public class CertManager {

private static final char[] passphrase = "changeit".toCharArray();
private String rootPath;
private SSLSocketFactory factory;
private SavingTrustManager trustManager;
private KeyStore keyStore;


/**
 * Creates a CertManager.
 * @param rootPath Path to directory where the file 'jssecacerts' is located.
 */
public CertManager(String rootPath){
    this.rootPath = rootPath;       
}

/**
 * Gets a SSLSocketFactory with the trusted certs.
 * @return
 * @throws Exception
 */
public SSLSocketFactory getSSLSocketFactory() throws Exception {
    //Load trusted certs
    File file = new File(rootPath+"jssecacerts");

    System.out.println("Loading KeyStore " + file + "...");
    InputStream in = new FileInputStream(file);
    keyStore = KeyStore.getInstance(KeyStore.getDefaultType());
    keyStore.load(in, passphrase);
    in.close();

    //Use these certs 
    SSLContext context = SSLContext.getInstance("TLS");
    TrustManagerFactory tmf =
        TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
    tmf.init(keyStore);
    X509TrustManager defaultTrustManager = (X509TrustManager)tmf.getTrustManagers()[0];
    trustManager = new SavingTrustManager(defaultTrustManager);
    context.init(null, new TrustManager[] {trustManager}, null);
    factory = context.getSocketFactory();
    return factory;
}

private static class SavingTrustManager implements X509TrustManager {

    private final X509TrustManager tm;
    private X509Certificate[] chain;

    SavingTrustManager(X509TrustManager tm) {
        this.tm = tm;
    }

    public X509Certificate[] getAcceptedIssuers() {         
        return tm.getAcceptedIssuers();
    }

    public void checkClientTrusted(X509Certificate[] chain, String authType)
    throws CertificateException {
        this.chain = chain;
        tm.checkClientTrusted(chain, authType);
    }

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

証明書マネージャーを使用して、FTPクライアントに提供するSSLSocketFactoryを取得します。

...
FTPClient client = new FTPClient();
CertManager certMan = new CertManager("");
SSLSocketFactory sslSocketFactory = null;
try{
    sslSocketFactory = certMan.getSSLSocketFactory();
} catch (Exception e) {
    e.printStackTrace();
}
client.setSSLSocketFactory(sslSocketFactory);
client.setSecurity(FTPClient.SECURITY_FTPS); // or client.setSecurity(FTPClient.SECURITY_FTPES);
...