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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
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 * This code 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
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 * 2 along with this work; if not, write to the Free Software Foundation,
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package sun.security.ec;

import java.io.IOException;
import java.math.BigInteger;

import java.security.*;
import java.security.spec.*;

import sun.security.util.*;

This class implements encoding and decoding of Elliptic Curve parameters
as specified in RFC 3279.
However, only named curves are currently supported.
ASN.1 from RFC 3279 follows. Note that X9.62 (2005) has added some additional
options.
   EcpkParameters ::= CHOICE {
     ecParameters  ECParameters,
     namedCurve    OBJECT IDENTIFIER,
     implicitlyCA  NULL }
   ECParameters ::= SEQUENCE {
      version   ECPVer,          -- version is always 1
      fieldID   FieldID,         -- identifies the finite field over
                                 -- which the curve is defined
      curve     Curve,           -- coefficients a and b of the
                                 -- elliptic curve
      base      ECPoint,         -- specifies the base point P
                                 -- on the elliptic curve
      order     INTEGER,         -- the order n of the base point
      cofactor  INTEGER OPTIONAL -- The integer h = #E(Fq)/n
      }
   ECPVer ::= INTEGER {ecpVer1(1)}
   Curve ::= SEQUENCE {
      a         FieldElement,
      b         FieldElement,
      seed      BIT STRING OPTIONAL }
   FieldElement ::= OCTET STRING
   ECPoint ::= OCTET STRING

Author:
 Andreas Sterbenz
Since:
  1.6/**
 * This class implements encoding and decoding of Elliptic Curve parameters
 * as specified in RFC 3279.
 *
 * However, only named curves are currently supported.
 *
 * ASN.1 from RFC 3279 follows. Note that X9.62 (2005) has added some additional
 * options.
 *
 * <pre>
 *    EcpkParameters ::= CHOICE {
 *      ecParameters  ECParameters,
 *      namedCurve    OBJECT IDENTIFIER,
 *      implicitlyCA  NULL }
 *
 *    ECParameters ::= SEQUENCE {
 *       version   ECPVer,          -- version is always 1
 *       fieldID   FieldID,         -- identifies the finite field over
 *                                  -- which the curve is defined
 *       curve     Curve,           -- coefficients a and b of the
 *                                  -- elliptic curve
 *       base      ECPoint,         -- specifies the base point P
 *                                  -- on the elliptic curve
 *       order     INTEGER,         -- the order n of the base point
 *       cofactor  INTEGER OPTIONAL -- The integer h = #E(Fq)/n
 *       }
 *
 *    ECPVer ::= INTEGER {ecpVer1(1)}
 *
 *    Curve ::= SEQUENCE {
 *       a         FieldElement,
 *       b         FieldElement,
 *       seed      BIT STRING OPTIONAL }
 *
 *    FieldElement ::= OCTET STRING
 *
 *    ECPoint ::= OCTET STRING
 * </pre>
 *
 * @since   1.6
 * @author  Andreas Sterbenz
 */
public final class ECParameters extends AlgorithmParametersSpi {

    public ECParameters() {
        // empty
    }

    // Used by SunPKCS11 and SunJSSE.
    public static ECPoint decodePoint(byte[] data, EllipticCurve curve)
            throws IOException {
        if ((data.length == 0) || (data[0] != 4)) {
            throw new IOException("Only uncompressed point format supported");
        }
        int n = (curve.getField().getFieldSize() + 7 ) >> 3;
        if (data.length != (n * 2) + 1) {
            throw new IOException("Point does not match field size");
        }
        byte[] xb = new byte[n];
        byte[] yb = new byte[n];
        System.arraycopy(data, 1, xb, 0, n);
        System.arraycopy(data, n + 1, yb, 0, n);
        return new ECPoint(new BigInteger(1, xb), new BigInteger(1, yb));
    }

    // Used by SunPKCS11 and SunJSSE.
    public static byte[] encodePoint(ECPoint point, EllipticCurve curve) {
        // get field size in bytes (rounding up)
        int n = (curve.getField().getFieldSize() + 7) >> 3;
        byte[] xb = trimZeroes(point.getAffineX().toByteArray());
        byte[] yb = trimZeroes(point.getAffineY().toByteArray());
        if ((xb.length > n) || (yb.length > n)) {
            throw new RuntimeException
                ("Point coordinates do not match field size");
        }
        byte[] b = new byte[1 + (n << 1)];
        b[0] = 4; // uncompressed
        System.arraycopy(xb, 0, b, n - xb.length + 1, xb.length);
        System.arraycopy(yb, 0, b, b.length - yb.length, yb.length);
        return b;
    }

    // Copied from the SunPKCS11 code - should be moved to a common location.
    // trim leading (most significant) zeroes from the result
    static byte[] trimZeroes(byte[] b) {
        int i = 0;
        while ((i < b.length - 1) && (b[i] == 0)) {
            i++;
        }
        if (i == 0) {
            return b;
        }
        byte[] t = new byte[b.length - i];
        System.arraycopy(b, i, t, 0, t.length);
        return t;
    }

    // Convert the given ECParameterSpec object to a NamedCurve object.
    // If params does not represent a known named curve, return null.
    // Used by SunPKCS11.
    public static NamedCurve getNamedCurve(ECParameterSpec params) {
        if ((params instanceof NamedCurve) || (params == null)) {
            return (NamedCurve)params;
        }
        // This is a hack to allow SunJSSE to work with 3rd party crypto
        // providers for ECC and not just SunPKCS11.
        // This can go away once we decide how to expose curve names in the
        // public API.
        // Note that it assumes that the 3rd party provider encodes named
        // curves using the short form, not explicitly. If it did that, then
        // the SunJSSE TLS ECC extensions are wrong, which could lead to
        // interoperability problems.
        int fieldSize = params.getCurve().getField().getFieldSize();
        for (ECParameterSpec namedCurve : NamedCurve.knownECParameterSpecs()) {
            // ECParameterSpec does not define equals, so check all the
            // components ourselves.
            // Quick field size check first
            if (namedCurve.getCurve().getField().getFieldSize() != fieldSize) {
                continue;
            }
            if (namedCurve.getCurve().equals(params.getCurve()) == false) {
                continue;
            }
            if (namedCurve.getGenerator().equals(params.getGenerator()) == false) {
                continue;
            }
            if (namedCurve.getOrder().equals(params.getOrder()) == false) {
                continue;
            }
            if (namedCurve.getCofactor() != params.getCofactor()) {
                continue;
            }
            // everything matches our named curve, return it
            return (NamedCurve)namedCurve;
        }
        // no match found
        return null;
    }

    // Used by SunJSSE.
    public static String getCurveName(ECParameterSpec params) {
        NamedCurve curve = getNamedCurve(params);
        return (curve == null) ? null : curve.getObjectIdentifier().toString();
    }

    // Used by SunPKCS11.
    public static byte[] encodeParameters(ECParameterSpec params) {
        NamedCurve curve = getNamedCurve(params);
        if (curve == null) {
            throw new RuntimeException("Not a known named curve: " + params);
        }
        return curve.getEncoded();
    }

    // Used by SunPKCS11.
    public static ECParameterSpec decodeParameters(byte[] params) throws IOException {
        DerValue encodedParams = new DerValue(params);
        if (encodedParams.tag == DerValue.tag_ObjectId) {
            ObjectIdentifier oid = encodedParams.getOID();
            ECParameterSpec spec = NamedCurve.getECParameterSpec(oid);
            if (spec == null) {
                throw new IOException("Unknown named curve: " + oid);
            }
            return spec;
        }

        throw new IOException("Only named ECParameters supported");

        // The code below is incomplete.
        // It is left as a starting point for a complete parsing implementation.

/*
        if (encodedParams.tag != DerValue.tag_Sequence) {
            throw new IOException("Unsupported EC parameters, tag: " + encodedParams.tag);
        }

        encodedParams.data.reset();

        DerInputStream in = encodedParams.data;

        int version = in.getInteger();
        if (version != 1) {
            throw new IOException("Unsupported EC parameters version: " + version);
        }
        ECField field = parseField(in);
        EllipticCurve curve = parseCurve(in, field);
        ECPoint point = parsePoint(in, curve);

        BigInteger order = in.getBigInteger();
        int cofactor = 0;

        if (in.available() != 0) {
            cofactor = in.getInteger();
        }

        // XXX HashAlgorithm optional

        if (encodedParams.data.available() != 0) {
            throw new IOException("encoded params have " +
                                  encodedParams.data.available() +
                                  " extra bytes");
        }

        return new ECParameterSpec(curve, point, order, cofactor);
*/
    }

/*
    private static final ObjectIdentifier fieldTypePrime =
        ObjectIdentifier.newInternal(new int[] {1, 2, 840, 10045, 1, 1});

    private static final ObjectIdentifier fieldTypeChar2 =
        ObjectIdentifier.newInternal(new int[] {1, 2, 840, 10045, 1, 2});

    private static ECField parseField(DerInputStream in) throws IOException {
        DerValue v = in.getDerValue();
        ObjectIdentifier oid = v.data.getOID();
        if (oid.equals(fieldTypePrime) == false) {
            throw new IOException("Only prime fields supported: " + oid);
        }
        BigInteger fieldSize = v.data.getBigInteger();
        return new ECFieldFp(fieldSize);
    }

    private static EllipticCurve parseCurve(DerInputStream in, ECField field)
            throws IOException {
        DerValue v = in.getDerValue();
        byte[] ab = v.data.getOctetString();
        byte[] bb = v.data.getOctetString();
        return new EllipticCurve(field, new BigInteger(1, ab), new BigInteger(1, bb));
    }

    private static ECPoint parsePoint(DerInputStream in, EllipticCurve curve)
            throws IOException {
        byte[] data = in.getOctetString();
        return decodePoint(data, curve);
    }
*/

    // used by ECPublicKeyImpl and ECPrivateKeyImpl
    static AlgorithmParameters getAlgorithmParameters(ECParameterSpec spec)
            throws InvalidKeyException {
        try {
            AlgorithmParameters params = AlgorithmParameters.getInstance
                                        ("EC", ECKeyFactory.ecInternalProvider);
            params.init(spec);
            return params;
        } catch (GeneralSecurityException e) {
            throw new InvalidKeyException("EC parameters error", e);
        }
    }

    // AlgorithmParameterSpi methods

    // The parameters these AlgorithmParameters object represents.
    // Currently, it is always an instance of NamedCurve.
    private ECParameterSpec paramSpec;

    protected void engineInit(AlgorithmParameterSpec paramSpec)
            throws InvalidParameterSpecException {
        if (paramSpec instanceof ECParameterSpec) {
            this.paramSpec = getNamedCurve((ECParameterSpec)paramSpec);
            if (this.paramSpec == null) {
                throw new InvalidParameterSpecException
                    ("Not a supported named curve: " + paramSpec);
            }
        } else if (paramSpec instanceof ECGenParameterSpec) {
            String name = ((ECGenParameterSpec)paramSpec).getName();
            ECParameterSpec spec = NamedCurve.getECParameterSpec(name);
            if (spec == null) {
                throw new InvalidParameterSpecException("Unknown curve: " + name);
            }
            this.paramSpec = spec;
        } else if (paramSpec == null) {
            throw new InvalidParameterSpecException
                ("paramSpec must not be null");
        } else {
            throw new InvalidParameterSpecException
                ("Only ECParameterSpec and ECGenParameterSpec supported");
        }
    }

    protected void engineInit(byte[] params) throws IOException {
        paramSpec = decodeParameters(params);
    }

    protected void engineInit(byte[] params, String decodingMethod) throws IOException {
        engineInit(params);
    }

    protected <T extends AlgorithmParameterSpec> T engineGetParameterSpec(Class<T> spec)
            throws InvalidParameterSpecException {
        if (spec.isAssignableFrom(ECParameterSpec.class)) {
            return spec.cast(paramSpec);
        } else if (spec.isAssignableFrom(ECGenParameterSpec.class)) {
            return spec.cast(new ECGenParameterSpec(getCurveName(paramSpec)));
        } else {
            throw new InvalidParameterSpecException
                ("Only ECParameterSpec and ECGenParameterSpec supported");
        }
    }

    protected byte[] engineGetEncoded() throws IOException {
        return encodeParameters(paramSpec);
    }

    protected byte[] engineGetEncoded(String encodingMethod) throws IOException {
        return engineGetEncoded();
    }

    protected String engineToString() {
        return paramSpec.toString();
    }
}