17

I'm looking for a way to programmatically create ssh compatible id_rsa and id_rsa.pub files in Java.

I got as far as creating the KeyPair:

KeyPairGenerator generator;
generator = KeyPairGenerator.getInstance("RSA");
// or: generator = KeyPairGenerator.getInstance("DSA");
generator.initialize(2048);
keyPair = generator.genKeyPair();

I can't figure out however how to create the String representation of the PrivateKey and PublicKey in the KeyPair.

4

4 回答 4

28

ssh 使用的密钥格式在RFC #4253中定义。RSA 公钥的格式如下：

  string    "ssh-rsa"
  mpint     e /* key public exponent */
  mpint     n /* key modulus */

所有数据类型编码都在RFC #4251的第 #5 节中定义。string 和 mpint（多精度整数）类型以这种方式编码：

  4-bytes word: data length (unsigned big-endian 32 bits integer)
  n bytes     : binary representation of the data

例如，字符串“ssh-rsa”的编码是：

  byte[] data = new byte[] {0, 0, 0, 7, 's', 's', 'h', '-', 'r', 's', 'a'};

对公众进行编码：

   public byte[] encodePublicKey(RSAPublicKey key) throws IOException
   {
       ByteArrayOutputStream out = new ByteArrayOutputStream();
       /* encode the "ssh-rsa" string */
       byte[] sshrsa = new byte[] {0, 0, 0, 7, 's', 's', 'h', '-', 'r', 's', 'a'};
       out.write(sshrsa);
       /* Encode the public exponent */
       BigInteger e = key.getPublicExponent();
       byte[] data = e.toByteArray();
       encodeUInt32(data.length, out);
       out.write(data);
       /* Encode the modulus */
       BigInteger m = key.getModulus();
       data = m.toByteArray();
       encodeUInt32(data.length, out);
       out.write(data);
       return out.toByteArray();
   }

   public void encodeUInt32(int value, OutputStream out) throws IOException
   {
       byte[] tmp = new byte[4];
       tmp[0] = (byte)((value >>> 24) & 0xff);
       tmp[1] = (byte)((value >>> 16) & 0xff);
       tmp[2] = (byte)((value >>> 8) & 0xff);
       tmp[3] = (byte)(value & 0xff);
       out.write(tmp);
   }

要对键进行字符串表示，只需在 Base64 中编码返回的字节数组。

对于私钥编码有两种情况：

  1. 私钥不受密码保护。在这种情况下，私钥根据 PKCS#8 标准进行编码，然后使用 Base64 进行编码。可以通过调用获取私钥的PKCS8getEncoded编码RSAPrivateKey。
  2. 私钥受密码保护。在这种情况下，密钥编码是 OpenSSH 专用格式。我不知道是否有任何关于这种格式的文档（当然除了 OpenSSH 源代码）
于 2010-09-14T06:44:02.833 回答
5

gotoalberto对另一个问题的回答（引用如下）适用于 RSA 和 DSA 密钥：

如果你想反转这个过程，即将一个PublicKeyJava 对象编码为 Linuxauthorized_keys条目格式，可以使用以下代码：

    /**
     * Encode PublicKey (DSA or RSA encoded) to authorized_keys like string
     *
     * @param publicKey DSA or RSA encoded
     * @param user username for output authorized_keys like string
     * @return authorized_keys like string
     * @throws IOException
     */
    public static String encodePublicKey(PublicKey publicKey, String user)
            throws IOException {
        String publicKeyEncoded;
        if(publicKey.getAlgorithm().equals("RSA")){
            RSAPublicKey rsaPublicKey = (RSAPublicKey) publicKey;
            ByteArrayOutputStream byteOs = new ByteArrayOutputStream();
            DataOutputStream dos = new DataOutputStream(byteOs);
            dos.writeInt("ssh-rsa".getBytes().length);
            dos.write("ssh-rsa".getBytes());
            dos.writeInt(rsaPublicKey.getPublicExponent().toByteArray().length);
            dos.write(rsaPublicKey.getPublicExponent().toByteArray());
            dos.writeInt(rsaPublicKey.getModulus().toByteArray().length);
            dos.write(rsaPublicKey.getModulus().toByteArray());
            publicKeyEncoded = new String(
                    Base64.encodeBase64(byteOs.toByteArray()));
            return "ssh-rsa " + publicKeyEncoded + " " + user;
        }
        else if(publicKey.getAlgorithm().equals("DSA")){
            DSAPublicKey dsaPublicKey = (DSAPublicKey) publicKey;
            DSAParams dsaParams = dsaPublicKey.getParams();

            ByteArrayOutputStream byteOs = new ByteArrayOutputStream();
            DataOutputStream dos = new DataOutputStream(byteOs);
            dos.writeInt("ssh-dss".getBytes().length);
            dos.write("ssh-dss".getBytes());
            dos.writeInt(dsaParams.getP().toByteArray().length);
            dos.write(dsaParams.getP().toByteArray());
            dos.writeInt(dsaParams.getQ().toByteArray().length);
            dos.write(dsaParams.getQ().toByteArray());
            dos.writeInt(dsaParams.getG().toByteArray().length);
            dos.write(dsaParams.getG().toByteArray());
            dos.writeInt(dsaPublicKey.getY().toByteArray().length);
            dos.write(dsaPublicKey.getY().toByteArray());
            publicKeyEncoded = new String(
                    Base64.encodeBase64(byteOs.toByteArray()));
            return "ssh-dss " + publicKeyEncoded + " " + user;
        }
        else{
            throw new IllegalArgumentException(
                    "Unknown public key encoding: " + publicKey.getAlgorithm());
        }
    }
于 2014-04-11T14:21:55.747 回答
4

正如 Carsten 所提到的，JSch 可以轻松生成这些密钥对。参考它的例子，KeyGen.java

于 2012-04-27T00:43:22.310 回答
2

任何类型（RSA、DSA 等）的通用解决方案PublicKey是使用 SSHJ 的单线：

byte[] b = new Buffer.PlainBuffer().putPublicKey(key).getCompactData()

然后使用Base64.getEncoder().encodeToString(b).

于 2017-04-07T22:09:39.623 回答