PubkeyUtils.java

/*
 * ConnectBot: simple, powerful, open-source SSH client for Android
 * Copyright 2007 Kenny Root, Jeffrey Sharkey
 *
 * Licensed 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 com.iiordanov.pubkeygenerator;

import java.io.IOException;
import java.math.BigInteger;
import java.security.AlgorithmParameters;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.Key;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SecureRandom;
import java.security.interfaces.DSAParams;
import java.security.interfaces.DSAPrivateKey;
import java.security.interfaces.DSAPublicKey;
import java.security.interfaces.RSAPrivateCrtKey;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.DSAPublicKeySpec;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.InvalidParameterSpecException;
import java.security.spec.KeySpec;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.RSAPublicKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.Arrays;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.EncryptedPrivateKeyInfo;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.PBEParameterSpec;
import javax.crypto.spec.SecretKeySpec;

import android.util.Log;

import com.trilead.ssh2.crypto.Base64;
import com.trilead.ssh2.crypto.PEMDecoder;
import com.trilead.ssh2.crypto.PEMStructure;
import com.trilead.ssh2.signature.DSASHA1Verify;
import com.trilead.ssh2.signature.RSASHA1Verify;

public class PubkeyUtils {
	public final static String TAG = "PubkeyUtils";

	public static final String PKCS8_START = "-----BEGIN PRIVATE KEY-----";
	public static final String PKCS8_END = "-----END PRIVATE KEY-----";

	// Size in bytes of salt to use.
	private static final int SALT_SIZE = 8;

	// Number of iterations for password hashing. PKCS#5 recommends 1000
	private static final int ITERATIONS = 1000;

	public static String formatKey(Key key){
		String algo = key.getAlgorithm();
		String fmt = key.getFormat();
		byte[] encoded = key.getEncoded();
		return "Key[algorithm=" + algo + ", format=" + fmt +
			", bytes=" + encoded.length + "]";
	}

	public static byte[] sha256(byte[] data) throws NoSuchAlgorithmException {
		return MessageDigest.getInstance("SHA-256").digest(data);
	}

	public static byte[] cipher(int mode, byte[] data, byte[] secret) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException {
		SecretKeySpec secretKeySpec = new SecretKeySpec(sha256(secret), "AES");
		Cipher c = Cipher.getInstance("AES");
		c.init(mode, secretKeySpec);
		return c.doFinal(data);
	}

	public static byte[] encrypt(byte[] cleartext, String secret) throws Exception {
		byte[] salt = new byte[SALT_SIZE];

		byte[] ciphertext = Encryptor.encrypt(salt, ITERATIONS, secret, cleartext);

		byte[] complete = new byte[salt.length + ciphertext.length];

		System.arraycopy(salt, 0, complete, 0, salt.length);
		System.arraycopy(ciphertext, 0, complete, salt.length, ciphertext.length);

		Arrays.fill(salt, (byte) 0x00);
		Arrays.fill(ciphertext, (byte) 0x00);

		return complete;
	}

	public static byte[] decrypt(byte[] complete, String secret) throws Exception {
		try {
			byte[] salt = new byte[SALT_SIZE];
			byte[] ciphertext = new byte[complete.length - salt.length];

			System.arraycopy(complete, 0, salt, 0, salt.length);
			System.arraycopy(complete, salt.length, ciphertext, 0, ciphertext.length);

			return Encryptor.decrypt(salt, ITERATIONS, secret, ciphertext);
		} catch (Exception e) {
			Log.d("decrypt", "Could not decrypt with new method", e);
			// We might be using the old encryption method.
			return cipher(Cipher.DECRYPT_MODE, complete, secret.getBytes());
		}
	}

	public static byte[] getEncodedPublic(PublicKey pk) {
		return new X509EncodedKeySpec(pk.getEncoded()).getEncoded();
	}

	public static byte[] getEncodedPrivate(PrivateKey pk) {
		return new PKCS8EncodedKeySpec(pk.getEncoded()).getEncoded();
	}

	public static byte[] getEncodedPrivate(PrivateKey pk, String secret) throws Exception {
		if (secret.length() > 0)
			return encrypt(getEncodedPrivate(pk), secret);
		else
			return getEncodedPrivate(pk);
	}

	public static PrivateKey decodePrivate(byte[] encoded, String keyType) throws NoSuchAlgorithmException, InvalidKeySpecException {
		PKCS8EncodedKeySpec privKeySpec = new PKCS8EncodedKeySpec(encoded);
		KeyFactory kf = KeyFactory.getInstance(keyType);
		return kf.generatePrivate(privKeySpec);
	}

	public static PrivateKey decodePrivate(byte[] encoded, String keyType, String secret) throws Exception {
		if (secret != null && secret.length() > 0)
			return decodePrivate(decrypt(encoded, secret), keyType);
		else
			return decodePrivate(encoded, keyType);
	}

	public static PublicKey decodePublic(byte[] encoded, String keyType) throws NoSuchAlgorithmException, InvalidKeySpecException {
		X509EncodedKeySpec pubKeySpec = new X509EncodedKeySpec(encoded);
		KeyFactory kf = KeyFactory.getInstance(keyType);
		return kf.generatePublic(pubKeySpec);
	}

	public static KeyPair recoverKeyPair(byte[] encoded) throws NoSuchAlgorithmException, InvalidKeySpecException, NoSuchProviderException {
		KeySpec privKeySpec = new PKCS8EncodedKeySpec(encoded);
		KeySpec pubKeySpec;

		PrivateKey priv;
		PublicKey pub;
		KeyFactory kf;
		try {
			kf = KeyFactory.getInstance(PubkeyDatabase.KEY_TYPE_RSA, "BC");
			priv = kf.generatePrivate(privKeySpec);

			pubKeySpec = new RSAPublicKeySpec(((RSAPrivateCrtKey) priv)
					.getModulus(), ((RSAPrivateCrtKey) priv)
					.getPublicExponent());

			pub = kf.generatePublic(pubKeySpec);
        } catch (ClassCastException e) {
            kf = KeyFactory.getInstance(PubkeyDatabase.KEY_TYPE_DSA, "BC");
            priv = kf.generatePrivate(privKeySpec);

            DSAParams params = ((DSAPrivateKey) priv).getParams();

            // Calculate public key Y
            BigInteger y = params.getG().modPow(((DSAPrivateKey) priv).getX(),
                            params.getP());

            pubKeySpec = new DSAPublicKeySpec(y, params.getP(), params.getQ(),
                            params.getG());

            pub = kf.generatePublic(pubKeySpec);
        }

		return new KeyPair(pub, priv);
	}


	/**
	 * Tries to recover key/pair with no passphrase, and if successful returns true. Otherwise returns false.
	 * @param sshPrivKey private key base64 encoded.
	 * @return
	 */
	public static boolean isEncrypted (String sshPrivKey) {
		KeyPair kp = PubkeyUtils.decryptAndRecoverKeyPair (sshPrivKey, "");
		if (kp == null)
			return true;
		return false;
	}
	
	/** Recovers the key-pair from the private key (and passphrase if provided).
	 *
	 * @param sshPrivKey private key base64 encoded.
	 * @param passphrase passphrase as a plain string.
	 * @return true if successful and false otherwise
	 * @author Iordan K. Iordanov
	 */
	public static KeyPair decryptAndRecoverKeyPair (String sshPrivKey, String passphrase) {
		KeyPair kp = null;
		if (sshPrivKey == null) {
			Log.e (TAG, "SSH private key is null.");
			return null;	
		} else if (sshPrivKey.length() == 0) {
			Log.i (TAG, "SSH private key is empty, not recovering");
			return null;
		}
		if (passphrase == null)
			passphrase = new String ("");

		try {
			if (passphrase.length() != 0) {
				Log.i(TAG, "Passphrase not empty, trying to decrypt key.");
				// Try decrypting key with passphrase entered by user.
				byte [] decrypted = PubkeyUtils.decrypt(android.util.Base64.decode(sshPrivKey,
														android.util.Base64.DEFAULT), passphrase);
				kp = PubkeyUtils.recoverKeyPair(decrypted);
			} else {
				Log.i(TAG, "Passphrase empty, recovering directly.");
				// There was no passphrase entered, so key is probably not encrypted.
				kp = PubkeyUtils.recoverKeyPair(android.util.Base64.decode(sshPrivKey,
												android.util.Base64.DEFAULT));
			}
		} catch (Exception e) {
			Log.i(TAG, "Either key is not encrypted and we were given passphrase, or the passphrase is wrong," +
					"or the key is corrupt.");
			e.printStackTrace();
			return null;
		}
		return kp;
	}

	/*
	 * OpenSSH compatibility methods
	 */

    public static String convertToOpenSSHFormat(PublicKey pk, String origNickname) throws IOException, InvalidKeyException {
        String nickname = origNickname;
        if (nickname == null)
            nickname = "pubkeygenerator@mobiledevice";

        if (pk instanceof RSAPublicKey) {
            String data = "ssh-rsa ";
            data += String.valueOf(Base64.encode(RSASHA1Verify.encodeSSHRSAPublicKey((RSAPublicKey)pk)));
            return data + " " + nickname;
        } else if (pk instanceof DSAPublicKey) {
            String data = "ssh-dss ";
            data += String.valueOf(Base64.encode(DSASHA1Verify.encodeSSHDSAPublicKey((DSAPublicKey)pk)));
            return data + " " + nickname;
        }

        throw new InvalidKeyException("Unknown key type");
    }

	/*
	 * OpenSSH compatibility methods
	 */

	public static String exportPEM(PrivateKey key, String secret) throws NoSuchAlgorithmException, InvalidParameterSpecException, NoSuchPaddingException, InvalidKeyException, InvalidAlgorithmParameterException, InvalidKeySpecException, IllegalBlockSizeException, IOException {
		StringBuilder sb = new StringBuilder();

		byte[] data = key.getEncoded();

		sb.append(PKCS8_START);
		sb.append('\n');

		if (secret != null) {
			byte[] salt = new byte[8];
			SecureRandom random = new SecureRandom();
			random.nextBytes(salt);

			PBEParameterSpec defParams = new PBEParameterSpec(salt, 1);
			AlgorithmParameters params = AlgorithmParameters.getInstance(key.getAlgorithm());

			params.init(defParams);

			PBEKeySpec pbeSpec = new PBEKeySpec(secret.toCharArray());

			SecretKeyFactory keyFact = SecretKeyFactory.getInstance(key.getAlgorithm());
			Cipher cipher = Cipher.getInstance(key.getAlgorithm());
			cipher.init(Cipher.WRAP_MODE, keyFact.generateSecret(pbeSpec), params);

			byte[] wrappedKey = cipher.wrap(key);

			EncryptedPrivateKeyInfo pinfo = new EncryptedPrivateKeyInfo(params, wrappedKey);

			data = pinfo.getEncoded();

			sb.append("Proc-Type: 4,ENCRYPTED\n");
			sb.append("DEK-Info: DES-EDE3-CBC,");
			sb.append(encodeHex(salt));
			sb.append("\n\n");
		}

		int i = sb.length();
		sb.append(Base64.encode(data));
		for (i += 63; i < sb.length(); i += 64) {
			sb.insert(i, "\n");
		}

		sb.append('\n');
		sb.append(PKCS8_END);
		sb.append('\n');

		return sb.toString();
	}

	private static final char[] HEX_DIGITS = { '0', '1', '2', '3', '4', '5', '6',
			'7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
	protected static String encodeHex(byte[] bytes) {
		final char[] hex = new char[bytes.length * 2];

		int i = 0;
		for (byte b : bytes) {
			hex[i++] = HEX_DIGITS[(b >> 4) & 0x0f];
			hex[i++] = HEX_DIGITS[b & 0x0f];
		}

		return String.valueOf(hex);
	}

	public static String getPubkeyString(PubkeyBean pubkey) {
		try {
			PublicKey pk = pubkey.getPublicKey();
			return convertToOpenSSHFormat(pk, pubkey.getNickname());
		} catch (Exception e) {
			e.printStackTrace();
		}
		return null;
	}

	public static String getPrivkeyString(PubkeyBean pubkey, String passphrase) {
		String data = null;
		boolean imported = PubkeyDatabase.KEY_TYPE_IMPORTED.equals(pubkey.getType());
		if (imported)
			try {
				data = new String(pubkey.getPrivateKey());
			} catch (Exception e) {
				e.printStackTrace();
			}
		else {
			try {
				PrivateKey pk = null;
				if (passphrase == null)
					pk = decodePrivate(pubkey.getPrivateKey(), pubkey.getType());
				else
					pk = decodePrivate(pubkey.getPrivateKey(), pubkey.getType(), passphrase);
				data = exportPEM(pk, passphrase);
			} catch (Exception e) {
				e.printStackTrace();
			}
		}
		return data;
	}
	
	// Deprecated method that handles only non-encrypted keys.
	public static KeyPair importPEM (String pem) {
        byte [] encoded   = null;
		KeyPair recovered = null;

		// Get rid of any header and footer.
        String privKeyPEM = pem.replace("-----BEGIN RSA PRIVATE KEY-----\n", "");
        privKeyPEM = privKeyPEM.replace("-----END RSA PRIVATE KEY-----", "");
        privKeyPEM = privKeyPEM.replace("-----BEGIN DSA PRIVATE KEY-----\n", "");
        privKeyPEM = privKeyPEM.replace("-----END DSA PRIVATE KEY-----", "");
        privKeyPEM = privKeyPEM.replace("-----BEGIN PRIVATE KEY-----\n", "");
        privKeyPEM = privKeyPEM.replace("-----END PRIVATE KEY-----", "");

        try {
       		encoded = android.util.Base64.decode(privKeyPEM, android.util.Base64.DEFAULT);      	
        	recovered = recoverKeyPair(encoded);
		} catch (Exception e) {
			Log.e (TAG, "Could not recover keypair from PEM string.");
			e.printStackTrace();
			return null;
		}
		return recovered;
	}
	
	public static KeyPair importPkcs8 (String pem) throws Exception {
        byte [] encoded   = null;
		KeyPair recovered = null;

		// Get rid of any header and footer.
        String privKeyPEM = pem.replace(PKCS8_START + "\n", "");
        privKeyPEM = privKeyPEM.replace(PKCS8_END,          "");

        try {
       		encoded = android.util.Base64.decode(privKeyPEM, android.util.Base64.DEFAULT);      	
           	recovered = recoverKeyPair(encoded);
		} catch (Exception e) {
			Log.e (TAG, "Could not recover keypair from PKCS8 string.");
			e.printStackTrace();
		}
		return recovered;
	}
	
	// New method that uses additional PEMDecoder functionality
    public static KeyPair importPem (String pem, String passphrase) throws Exception {
    	PEMStructure ps = null;
		KeyPair recovered = null;

    	try {
    		ps = PEMDecoder.parsePEM(pem.toCharArray());
    	} catch (Exception e) {
			Log.e (TAG, "Key not in PEM format or corrupt.");
			e.printStackTrace();
			return recovered;
    	}

		if (PEMDecoder.isPEMEncrypted(ps)) {
			try {
				PEMDecoder.decode(ps, passphrase);
			} catch (Exception e) {
				throw new Exception("Failed to decrypt PEM. It is encrypted, but wrong passphrase was specified. " +
									"Please specify correct passphrase in the appropriate field, and import again.");
			}
		}
		
        try {
        	recovered = recoverKeyPair(ps.data);
        } catch (Exception e) {
			Log.e (TAG, "Could not recover key-pair from PEM string.");
			e.printStackTrace();
		}
		return recovered;
    }

    // This function first tries to import keys in PEM format and failing that, tries passphrase-less PKCS8 format.
    public static KeyPair tryImportingPemAndPkcs8 (String pem, String passphrase) throws Exception {
    	KeyPair pair = null;
   		// Try to import as PEM
    	pair = importPem (pem, passphrase);
   		// If PEM import failed, try to import as PKCS#8
   		if (pair == null) {
   			pair = importPkcs8 (pem);
   		}
   		// If both failed, throw an exception to alert the user to the failure.
   		if (pair == null) {
   			throw new Exception("Failed to recover key-pair from file. Supported formats are " +
   								"encrypted/unencrypted RSA key in PEM format or unencrypted RSA/DSA " +
   								"key in PKCS8 format. Keys generated with 'ssh-keygen -t rsa' are known to work.");
   		}
    	return pair;
    }
    
}