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## pkcs8.js

#### Summary

Basic helper functions to convert PKCS#8 data to GP keys and vice versa

Class Summary
PKCS8 |

    /**
     *  ---------
     * |.##> <##.|  Open Smart Card Development Platform (www.openscdp.org)
     * |#       #|
     * |#       #|  Copyright (c) 1999-2009 CardContact Software & System Consulting
     * |'##> <##'|  Andreas Schwier, 32429 Minden, Germany (www.cardcontact.de)
     *  ---------
     *
     *  This file is part of OpenSCDP.
     *
     *  OpenSCDP is free software; you can redistribute it and/or modify
     *  it under the terms of the GNU General Public License version 2 as
     *  published by the Free Software Foundation.
     *
     *  OpenSCDP 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 OpenSCDP; if not, write to the Free Software
     *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
     *
     * @fileoverview Basic helper functions to convert PKCS#8 data to GP keys and vice versa
     */

    /**
     * Empty constructor
     */
    function PKCS8() {
    }

    PKCS8.idEcPublicKey = new ByteString("id-ecPublicKey", OID);
    PKCS8.rsaEncryption = new ByteString("1.2.840.113549.1.1.1", OID);

    /**
     * Convert x/y coordinates to uncompressed format
     *
     * @param {ByteString} x the x coordinate
     * @param {ByteString} y the y coordinate
     * @type ByteString
     * @return ByteString containing compressed format
     *
     */
    PKCS8.encodeUncompressedECPoint = function(x,y) {

    	bb = new ByteBuffer();

    	// uncompressed encoding
    	bb.append(new ByteString("04", HEX));
    	bb.append(x);
    	bb.append(y);

    	return bb.toByteString();
    }

    /**
     * Convert uncompressed format to x and y coordinates
     *
     * @param {ByteString} compressed point
     * @type Object
     * @return Object with ByteString properties x and y
     *
     */
    PKCS8.decodeUncompressedECPoint = function(uncompressedPoint) {

    	// Determine the size of the coordinates ignoring the indicator byte '04'
    	var length = uncompressedPoint.length - 1;

    	var sizeOfCoordinate = length >> 1;

    	var xValue = uncompressedPoint.bytes(1, sizeOfCoordinate);
    	var yValue = uncompressedPoint.bytes(1 + sizeOfCoordinate, sizeOfCoordinate);

    	return { x:xValue, y:yValue };
    }

    /**
     * Integer to octet string conversion
     *
     * @param {ByteString} value the encoded integer value
     * @param {Number} the number of digits
     * @type ByteString
     * @return the truncated or padded result
     */
    PKCS8.I2O = function(value, length) {
    	if (value.length > length) {
    		value = value.right(length);
    	}
    	while (value.length < length) {
    		value = PKCS8.PAD.left((length - value.length - 1 & 15) + 1).concat(value);
    	}
    	return value;
    }
    PKCS8.PAD = new ByteString("00000000000000000000000000000000", HEX);

    /**
     * Strips leading zeros of a ByteString
     *
     * @param {ByteString} value the ByteString value
     * @return the stripped ByteString object, may be an empty ByteString
     * @type ByteString
     */
    PKCS8.stripLeadingZeros = function(value, size) {
    	if (typeof(size) == "undefined") {
    		var limit = value.length;
    	} else {
    		limit = value.length - size;
    	}

    	var i = 0;
    	for (; (i < limit) && (value.byteAt(i) == 0); i++);

    	return value.bytes(i);
    }

    /**
     * Removes leading zeros and prepends a single '00' to ByteStrings which have the most significant bit set.
     *
     * This prevent interpretation of the integer representation if converted into
     * a signed ASN1 INTEGER.
     *
     * @param {ByteString} value the value to convert
     * @return the converted value
     * @type ByteString
     */
    PKCS8.convertUnsignedInteger = function(value) {
    	assert(value.length > 0);

    	var i = 0;
    	for (; (i < value.length - 1) && (value.byteAt(i) == 0); i++);

    	if (value.byteAt(i) >= 0x80) {
    		value = (new ByteString("00", HEX)).concat(value.bytes(i));
    	} else {
    		value = value.bytes(i);
    	}

    	return value;
    }

    /**
     * Encode a given GP ECC private key as specified by the PKCS#8 format
     *
     * @param {Key} the private key object that should be encoded
     * @return the encoded PKCS#8 private key
     * @type ByteString
     */
    PKCS8.encodeECCKeyUsingPKCS8Format = function(privateKey) {
    	var privateKeyInfo = new ASN1(ASN1.SEQUENCE);

    	// Set the version number - must be zero
    	privateKeyInfo.add(new ASN1(ASN1.INTEGER, new ByteString("00", HEX)));

    	var privateKeyAlgorithm = new ASN1(ASN1.SEQUENCE);
    	privateKeyAlgorithm.add(new ASN1(ASN1.OBJECT_IDENTIFIER, PKCS8.idEcPublicKey));

    	var domainInfo = new ASN1(ASN1.SEQUENCE);

    	// Cofactor - must be 1
    	domainInfo.add(new ASN1(ASN1.INTEGER, PKCS8.stripLeadingZeros(privateKey.getComponent(Key.ECC_H))));

    	var field = new ASN1(ASN1.SEQUENCE);

    	// we are using a prime field
    	field.add(new ASN1(ASN1.OBJECT_IDENTIFIER, new ByteString("prime-field", OID))); // prime field

    	var primeOrder = privateKey.getComponent(Key.ECC_P);
    	if (primeOrder.byteAt(0) >= 0x80) { // signed int? -> add 0x00
    		field.add(new ASN1(ASN1.INTEGER, new ByteString("00", HEX).concat(privateKey.getComponent(Key.ECC_P))));
    	} else {
    		field.add(new ASN1(ASN1.INTEGER, privateKey.getComponent(Key.ECC_P)));
    	}

    	domainInfo.add(field);

    	// Coefficients a and b
    	var coeff = new ASN1(ASN1.SEQUENCE);

    	// first coefficient
    	coeff.add(new ASN1(ASN1.OCTET_STRING, privateKey.getComponent(Key.ECC_A)));

    	// second coefficient
    	coeff.add(new ASN1(ASN1.OCTET_STRING, privateKey.getComponent(Key.ECC_B)));

    	domainInfo.add(coeff);

    	// Base point (uncompressed)
    	var gx = privateKey.getComponent(Key.ECC_GX);
    	var gy = privateKey.getComponent(Key.ECC_GY);

    	domainInfo.add(new ASN1(ASN1.OCTET_STRING, PKCS8.encodeUncompressedECPoint(gx, gy)));

    	// group order generated by the base point
    	var groupOrder = privateKey.getComponent(Key.ECC_N);
    	if (groupOrder.byteAt(0) >= 0x80) { // signed int? -> add 0x00
    		domainInfo.add(new ASN1(ASN1.INTEGER, new ByteString("00", HEX).concat(privateKey.getComponent(Key.ECC_N))));
    	} else {
    		domainInfo.add(new ASN1(ASN1.INTEGER, privateKey.getComponent(Key.ECC_N)));
    	}

    	privateKeyAlgorithm.add(domainInfo);

    	// encode the key information
    	privateKeyInfo.add(privateKeyAlgorithm);

    	// encode the private key
    	var encodedPrivateKey = new ASN1(ASN1.OCTET_STRING);

    	var pk = privateKey.getComponent(Key.ECC_D);
    	var key = new ASN1(ASN1.SEQUENCE);
    	key.add(new ASN1(ASN1.INTEGER, new ByteString("01", HEX)));
    	key.add(new ASN1(ASN1.OCTET_STRING, pk));

    	encodedPrivateKey.add(key);

    	privateKeyInfo.add(encodedPrivateKey);

    //	print(privateKeyInfo);
    	return privateKeyInfo.getBytes();
    }

    /**
     * Encode RSA private key as defined in PKCS#1
     *
     * RSAPrivateKey ::= SEQUENCE {
     *     version           Version,
     *     modulus           INTEGER,  -- n
     *     publicExponent    INTEGER,  -- e
     *     privateExponent   INTEGER,  -- d
     *     prime1            INTEGER,  -- p
     *     prime2            INTEGER,  -- q
     *     exponent1         INTEGER,  -- d mod (p-1)
     *     exponent2         INTEGER,  -- d mod (q-1)
     *     coefficient       INTEGER,  -- (inverse of q) mod p
     *     otherPrimeInfos   OtherPrimeInfos OPTIONAL
     * }
     * @param {Key} privateKey the private RSA key in CRT format
     * @type ByteString
     * @return the encoded RSA key
     */
    PKCS8.encodeRSAKey = function(privateKey, publicKey) {
    	var rsaPrivateKey =
    		new ASN1(ASN1.SEQUENCE);

    	rsaPrivateKey.add(new ASN1(ASN1.INTEGER, ByteString.valueOf(0)));
    	if (typeof(publicKey) != "undefined") {
    		rsaPrivateKey.add(new ASN1(ASN1.INTEGER, PKCS8.convertUnsignedInteger(publicKey.getComponent(Key.MODULUS))));
    		rsaPrivateKey.add(new ASN1(ASN1.INTEGER, PKCS8.convertUnsignedInteger(publicKey.getComponent(Key.EXPONENT))));
    	} else {
    		rsaPrivateKey.add(new ASN1(ASN1.INTEGER, ByteString.valueOf(0)));
    		rsaPrivateKey.add(new ASN1(ASN1.INTEGER, ByteString.valueOf(0)));
    	}
    	rsaPrivateKey.add(new ASN1(ASN1.INTEGER, ByteString.valueOf(0)));		// Private Exponent not at interface for CRT format
    	rsaPrivateKey.add(new ASN1(ASN1.INTEGER, PKCS8.convertUnsignedInteger(privateKey.getComponent(Key.CRT_P))));
    	rsaPrivateKey.add(new ASN1(ASN1.INTEGER, PKCS8.convertUnsignedInteger(privateKey.getComponent(Key.CRT_Q))));
    	rsaPrivateKey.add(new ASN1(ASN1.INTEGER, PKCS8.convertUnsignedInteger(privateKey.getComponent(Key.CRT_DP1))));
    	rsaPrivateKey.add(new ASN1(ASN1.INTEGER, PKCS8.convertUnsignedInteger(privateKey.getComponent(Key.CRT_DQ1))));
    	rsaPrivateKey.add(new ASN1(ASN1.INTEGER, PKCS8.convertUnsignedInteger(privateKey.getComponent(Key.CRT_PQ))));

    	return rsaPrivateKey.getBytes();
    }

    /**
     * Encode a given GP RSA private key as specified by the PKCS#8 format
     *
     * @param {Key} the private key object that should be encoded
     * @return the encoded PKCS#8 private key
     * @type ByteString
     */
    PKCS8.encodeRSAKeyUsingPKCS8Format = function(privateKey, publicKey) {
    	var privateKeyInfo = new ASN1(ASN1.SEQUENCE);

    	// Set the version number - must be zero
    	privateKeyInfo.add(new ASN1(ASN1.INTEGER, new ByteString("00", HEX)));

    	var privateKeyAlgorithm = new ASN1(ASN1.SEQUENCE);
    	privateKeyAlgorithm.add(new ASN1(ASN1.OBJECT_IDENTIFIER, PKCS8.rsaEncryption));
    	privateKeyAlgorithm.add(new ASN1(ASN1.NULL));

    	// encode the key information
    	privateKeyInfo.add(privateKeyAlgorithm);

    	// encode the private key
    	var encodedPrivateKey = new ASN1(ASN1.OCTET_STRING, PKCS8.encodeRSAKey(privateKey, publicKey));

    	privateKeyInfo.add(encodedPrivateKey);

    //	print(privateKeyInfo);
    	return privateKeyInfo.getBytes();
    }

    /**
     * Encode a given GP private key as specified by the PKCS#8 format
     *
     * For now we only support the encoding of ECC private keys in a prime field
     *
     * @param {Key} the private key object that should be encoded
     * @return the encoded PKCS#8 private key
     * @type ByteString
     */
    PKCS8.encodeKeyUsingPKCS8Format = function(privateKey, publicKey) {

    	assert(privateKey.getType() == Key.PRIVATE);
    	if (typeof(privateKey.getComponent(Key.ECC_P)) != "undefined") {
    		return PKCS8.encodeECCKeyUsingPKCS8Format(privateKey);
    	} else {
    		return PKCS8.encodeRSAKeyUsingPKCS8Format(privateKey, publicKey);
    	}
    }

    /**
     * Decode a given PKCS#8 ECC private key from the given ByteString and create a GP key object
     *
     * For now we only support the decoding of ECC private keys in a prime field
     *
     * @param {ASN1} algparam the algorithm parameter from AlgorithmInfo
     * @param {ASN1} privateKey the privateKey element from the PKCS#8 structure
     * @return the GP key object
     * @type Key
     */
    PKCS8.decodeECCKeyFromPKCS8Format = function(domainParameter, encodedKey) {

    	var key = new Key();

    	key.setType(Key.PRIVATE);

    	key.setComponent(Key.ECC_D, encodedKey.get(1).value);

    	// Decode the domain parameters
    	var cofactor = domainParameter.get(0);
    	key.setComponent(Key.ECC_H, cofactor.value);

    	var order = domainParameter.get(1).get(1);
    	key.setComponent(Key.ECC_P, PKCS8.stripLeadingZeros(order.value));

    	var coeff_A = domainParameter.get(2).get(0);
    	key.setComponent(Key.ECC_A, coeff_A.value);

    	var coeff_B = domainParameter.get(2).get(1);
    	key.setComponent(Key.ECC_B, coeff_B.value);

    	var generatorPoint = domainParameter.get(3).value;

    	var coordinates = PKCS8.decodeUncompressedECPoint(generatorPoint);

    	key.setComponent(Key.ECC_GX, coordinates.x);
    	key.setComponent(Key.ECC_GY, coordinates.y);

    	var groupOrder = domainParameter.get(4);

    	key.setComponent(Key.ECC_N, PKCS8.stripLeadingZeros(groupOrder.value));

    	return key;
    }

    /**
     * Decode a given PKCS#8 RSA private key from the given ByteString and create a GP key object
     *
     * @param {ByteString} the private key object in PKCS#8 format
     * @param {ASN1} algparam the algorithm parameter from AlgorithmInfo
     * @param {ASN1} privateKey the privateKey element from the PKCS#8 structure
     * @return the GP key object
     * @type Key
     */
    PKCS8.decodeRSAKeyFromPKCS8Format = function(algparam, privateKey) {

    	var key = new Key();

    	key.setType(Key.PRIVATE);

    	assert(algparam.tag == ASN1.NULL);
    	assert(!algparam.isconstructed);
    	assert(algparam.length == 0);

    	assert(privateKey.tag == ASN1.SEQUENCE);
    	assert(privateKey.isconstructed);
    	assert(privateKey.elements >= 9);

    	for (var i = 0; i < 9; i++) {
    		var e = privateKey.get(i);
    		assert(e.tag == ASN1.INTEGER);
    		assert(!e.isconstructed);
    	}

    	assert(privateKey.get(0).value.toUnsigned() == 0);

    	var p = PKCS8.stripLeadingZeros(privateKey.get(4).value);
    	var l = p.length;
    	key.setComponent(Key.CRT_P,   p);
    	key.setComponent(Key.CRT_Q,   PKCS8.I2O(privateKey.get(5).value, l));
    	key.setComponent(Key.CRT_DP1, PKCS8.I2O(privateKey.get(6).value, l));
    	key.setComponent(Key.CRT_DQ1, PKCS8.I2O(privateKey.get(7).value, l));
    	key.setComponent(Key.CRT_PQ,  PKCS8.I2O(privateKey.get(8).value, l));

    	return key;
    }

    /**
     * Decode a given PKCS#8 private key from the given ByteString and create a GP key object
     *
     * For now we only support the decoding of ECC private keys in a prime field
     *
     * @param {ByteString} the private key object in PKCS#8 format
     * @return the GP key object
     * @type Key
     */
    PKCS8.decodeKeyFromPKCS8Format = function(encodedKey) {
    	var p8 = new ASN1(encodedKey);

    	assert(p8.isconstructed);
    	assert(p8.elements >= 3);

    	var version = p8.get(0);
    	assert(version.tag == ASN1.INTEGER);
    	assert(version.value.toUnsigned() == 0);

    	var pkai = p8.get(1);
    	assert(pkai.tag == ASN1.SEQUENCE);
    	assert(pkai.isconstructed);
    	assert(pkai.elements == 2);
    	var keytype = pkai.get(0);

    	assert(keytype.tag == ASN1.OBJECT_IDENTIFIER);

    	var algparam = pkai.get(1);

    	var privateKey = p8.get(2);
    	assert(privateKey.tag == ASN1.OCTET_STRING);
    	if (privateKey.isconstructed) {
    		privateKey = privateKey.get(0);
    	} else {
    		privateKey = new ASN1(privateKey.value);
    	}

    	if (keytype.value.equals(PKCS8.rsaEncryption)) {
    		return PKCS8.decodeRSAKeyFromPKCS8Format(algparam, privateKey);
    	} else if (keytype.value.equals(PKCS8.idEcPublicKey)) {
    		return PKCS8.decodeECCKeyFromPKCS8Format(algparam, privateKey);
    	} else {
    		throw new Error("Unknown key type " + keytype.value.toString(OID));
    	}
    }

    /**
     * Simple self-test
     */
    PKCS8.test = function() {

    	// Set OID for EC curve
    	var ecCurve = "1.3.36.3.3.2.8.1.1.7";

        var crypto = new Crypto("BC");

        // Create empty public key object
        var pubKey = new Key();
        pubKey.setType(Key.PUBLIC);
        pubKey.setComponent(Key.ECC_CURVE_OID, new ByteString(ecCurve, OID));

        // Create empty private key object
        var priKey = new Key();
        priKey.setType(Key.PRIVATE);
        priKey.setComponent(Key.ECC_CURVE_OID, new ByteString(ecCurve, OID));

        // Generate key pair
        crypto.generateKeyPair(Crypto.EC, pubKey, priKey);

        // Encode
        var p8Key = PKCS8.encodeKeyUsingPKCS8Format(priKey);

        // Decode
        var decodedKeyObject = PKCS8.decodeKeyFromPKCS8Format(p8Key);

        // Compare
        assert(decodedKeyObject.getComponent(Key.ECC_D).equals(priKey.getComponent(Key.ECC_D)));

        assert(decodedKeyObject.getComponent(Key.ECC_GX).equals(priKey.getComponent(Key.ECC_GX)));
        assert(decodedKeyObject.getComponent(Key.ECC_GY).equals(priKey.getComponent(Key.ECC_GY)));
        assert(decodedKeyObject.getComponent(Key.ECC_A).equals(pubKey.getComponent(Key.ECC_A)));
        assert(decodedKeyObject.getComponent(Key.ECC_B).equals(pubKey.getComponent(Key.ECC_B)));

        // Encode
        var refp8Key = PKCS8.encodeKeyUsingPKCS8Format(decodedKeyObject);

        // Compare
        assert(p8Key.equals(refp8Key));

        // Create empty public key object
    	var pubKey = new Key();
        pubKey.setType(Key.PUBLIC);
        pubKey.setSize(1024);

        // Create empty private key object
        var priKey = new Key();
        priKey.setType(Key.PRIVATE);

        // Generate key pair
        crypto.generateKeyPair(Crypto.RSA, pubKey, priKey);

        // Encode
        var p8Key = PKCS8.encodeKeyUsingPKCS8Format(priKey);

        // Decode
        var decodedKeyObject = PKCS8.decodeKeyFromPKCS8Format(p8Key);

        // Compare
        assert(decodedKeyObject.getComponent(Key.CRT_P).equals(priKey.getComponent(Key.CRT_P)));
        assert(decodedKeyObject.getComponent(Key.CRT_Q).equals(priKey.getComponent(Key.CRT_Q)));
        assert(decodedKeyObject.getComponent(Key.CRT_DP1).equals(priKey.getComponent(Key.CRT_DP1)));
        assert(decodedKeyObject.getComponent(Key.CRT_DQ1).equals(priKey.getComponent(Key.CRT_DQ1)));
        assert(decodedKeyObject.getComponent(Key.CRT_PQ).equals(priKey.getComponent(Key.CRT_PQ)));

        // Encode
        var refp8Key = PKCS8.encodeKeyUsingPKCS8Format(decodedKeyObject);

        // Compare
        assert(p8Key.equals(refp8Key));
    }

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