src/java.base/share/classes/sun/security/x509/X509Key.java

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package sun.security.x509;

import java.io.*;
import java.util.Arrays;
import java.security.Key;
import java.security.PublicKey;
import java.security.KeyFactory;
import java.security.Security;
import java.security.Provider;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.X509EncodedKeySpec;

import sun.security.util.HexDumpEncoder;
import sun.security.util.*;

/**
 * Holds an X.509 key, for example a public key found in an X.509
 * certificate.  Includes a description of the algorithm to be used
 * with the key; these keys normally are used as
 * "SubjectPublicKeyInfo".
 *
 * <P>While this class can represent any kind of X.509 key, it may be
 * desirable to provide subclasses which understand how to parse keying
 * data.   For example, RSA public keys have two members, one for the
 * public modulus and one for the prime exponent.  If such a class is
 * provided, it is used when parsing X.509 keys.  If one is not provided,
 * the key still parses correctly.
 *
 * @author David Brownell
 */
public class X509Key implements PublicKey, DerEncoder {

    /** use serialVersionUID from JDK 1.1. for interoperability */
    @java.io.Serial
    private static final long serialVersionUID = -5359250853002055002L;

    /* The algorithm information (name, parameters, etc). */
    protected AlgorithmId algid;

    /* BitArray form of key */
    private transient BitArray bitStringKey = null;

    /* The encoding for the key. */
    protected byte[] encodedKey;

    /**
     * Default constructor.  The key constructed must have its key
     * and algorithm initialized before it may be used, for example
     * by using <code>decode</code>.
     */
    public X509Key() { }

    /*
     * Build and initialize as a "default" key.  All X.509 key
     * data is stored and transmitted losslessly, but no knowledge
     * about this particular algorithm is available.
     */
    @SuppressWarnings("this-escape")
    public X509Key(AlgorithmId algid, BitArray key) {
        this.algid = algid;
        setKey(key);
        encode();
    }

    /**
     * Sets the key in the BitArray form.
     */
    protected void setKey(BitArray key) {
        this.bitStringKey = (BitArray)key.clone();
    }

    /**
     * Gets the key. The key may or may not be byte aligned.
     * @return a BitArray containing the key.
     */
    public BitArray getKey() {
        return (BitArray)bitStringKey.clone();
    }

    /**
     * Construct X.509 subject public key from a DER value.  If
     * the runtime environment is configured with a specific class for
     * this kind of key, a subclass is returned.  Otherwise, a generic
     * X509Key object is returned.
     *
     * <P>This mechanism guarantees that keys (and algorithms) may be
     * freely manipulated and transferred, without risk of losing
     * information.  Also, when a key (or algorithm) needs some special
     * handling, that specific need can be accommodated.
     *
     * @param in the DER-encoded SubjectPublicKeyInfo value
     * @exception IOException on data format errors
     */
    public static PublicKey parse(DerValue in) throws IOException
    {
        AlgorithmId     algorithm;
        PublicKey       subjectKey;

        if (in.tag != DerValue.tag_Sequence)
            throw new IOException("corrupt subject key");

        algorithm = AlgorithmId.parse(in.data.getDerValue());
        try {
            subjectKey = buildX509Key(algorithm,
                in.data.getUnalignedBitString());

        } catch (InvalidKeyException e) {
            throw new IOException("subject key, " + e.getMessage(), e);
        }

        if (in.data.available() != 0)
            throw new IOException("excess subject key");
        return subjectKey;
    }

    /**
     * Parse the key bits.  This may be redefined by subclasses to take
     * advantage of structure within the key.  For example, RSA public
     * keys encapsulate two unsigned integers (modulus and exponent) as
     * DER values within the <code>key</code> bits; Diffie-Hellman and
     * DSS/DSA keys encapsulate a single unsigned integer.
     *
     * <P>This function is called when creating X.509 SubjectPublicKeyInfo
     * values using the X509Key member functions, such as <code>parse</code>
     * and <code>decode</code>.
     *
     * @exception InvalidKeyException on invalid key encodings.
     */
    protected void parseKeyBits() throws InvalidKeyException {
        getEncodedInternal();
    }

    /*
     * Factory interface, building the kind of key associated with this
     * specific algorithm ID or else returning this generic base class.
     * See the description above.
     */
    static PublicKey buildX509Key(AlgorithmId algid, BitArray key)
      throws IOException, InvalidKeyException
    {
        /*
         * Use the algid and key parameters to produce the ASN.1 encoding
         * of the key, which will then be used as the input to the
         * key factory.
         */
        DerOutputStream x509EncodedKeyStream = new DerOutputStream();
        encode(x509EncodedKeyStream, algid, key);
        X509EncodedKeySpec x509KeySpec
            = new X509EncodedKeySpec(x509EncodedKeyStream.toByteArray());

        try {
            // Instantiate the key factory of the appropriate algorithm
            KeyFactory keyFac = KeyFactory.getInstance(algid.getName());

            // Generate the public key
            return keyFac.generatePublic(x509KeySpec);
        } catch (NoSuchAlgorithmException e) {
            // Return generic X509Key with opaque key data (see below)
        } catch (InvalidKeySpecException e) {
            throw new InvalidKeyException(e.getMessage(), e);
        }

        /*
         * Try again using JDK1.1-style for backwards compatibility.
         */
        String classname = "";
        try {
            Provider sunProvider;

            sunProvider = Security.getProvider("SUN");
            if (sunProvider == null)
                throw new InstantiationException();
            classname = sunProvider.getProperty("PublicKey.X.509." +
              algid.getName());
            if (classname == null) {
                throw new InstantiationException();
            }

            Class<?> keyClass = null;
            try {
                keyClass = Class.forName(classname);
            } catch (ClassNotFoundException e) {
                ClassLoader cl = ClassLoader.getSystemClassLoader();
                if (cl != null) {
                    keyClass = cl.loadClass(classname);
                }
            }

            @SuppressWarnings("deprecation")
            Object      inst = (keyClass != null) ? keyClass.newInstance() : null;
            X509Key     result;

            if (inst instanceof X509Key) {
                result = (X509Key) inst;
                result.algid = algid;
                result.setKey(key);
                result.parseKeyBits();
                return result;
            }
        } catch (ClassNotFoundException | InstantiationException e) {
        } catch (IllegalAccessException e) {
            // this should not happen.
            throw new IOException (classname + " [internal error]");
        }

        return new X509Key(algid, key);
    }

    /**
     * Returns the algorithm to be used with this key.
     */
    public String getAlgorithm() {
        return algid.getName();
    }

    /**
     * Returns the algorithm ID to be used with this key.
     */
    public AlgorithmId getAlgorithmId() { return algid; }

    /**
     * Encode SubjectPublicKeyInfo sequence on the DER output stream.
     */
    @Override
    public final void encode(DerOutputStream out) {
        encode(out, this.algid, getKey());
    }

    /**
     * Returns the DER-encoded form of the key as a byte array.
     */
    public byte[] getEncoded() {
        return getEncodedInternal().clone();
    }

    private byte[] getEncodedInternal() {
        byte[] encoded = encodedKey;
        if (encoded == null) {
            DerOutputStream out = new DerOutputStream();
            encode(out);
            encodedKey = encoded = out.toByteArray();
        }
        return encoded;
    }

    /**
     * Returns the format for this key: "X.509"
     */
    public String getFormat() {
        return "X.509";
    }

    /**
     * Returns the DER-encoded form of the key as a byte array.
     */
    public byte[] encode() {
        return getEncodedInternal().clone();
    }

    /*
     * Returns a printable representation of the key
     */
    public String toString()
    {
        HexDumpEncoder  encoder = new HexDumpEncoder();

        return "algorithm = " + algid.toString()
            + ", unparsed keybits = \n" + encoder.encodeBuffer(bitStringKey.toByteArray());
    }

    /**
     * Initialize an X509Key object from a DerValue, obeying the X.509
     * <code>SubjectPublicKeyInfo</code> format.  That is, the data is a
     * sequence consisting of an algorithm ID and a bit string which holds
     * the key.  (That bit string is often used to encapsulate another DER
     * encoded sequence.)
     *
     * <P>Subclasses should not normally redefine this method; they should
     * instead provide a <code>parseKeyBits</code> method to parse any
     * fields inside the <code>key</code> member.
     *
     * <P>The exception to this rule is that since private keys need not
     * be encoded using the X.509 <code>SubjectPublicKeyInfo</code> format,
     * private keys may override this method, <code>encode</code>, and
     * of course <code>getFormat</code>.
     *
     * @param val a DER-encoded X.509 SubjectPublicKeyInfo value
     * @exception InvalidKeyException on parsing errors.
     */
    public void decode(DerValue val) throws InvalidKeyException {
        try {
            if (val.tag != DerValue.tag_Sequence)
                throw new InvalidKeyException("invalid key format");

            algid = AlgorithmId.parse(val.data.getDerValue());
            setKey(val.data.getUnalignedBitString());
            parseKeyBits();
            if (val.data.available() != 0)
                throw new InvalidKeyException ("excess key data");

        } catch (IOException e) {
            throw new InvalidKeyException("Unable to decode key", e);
        }
    }

    public void decode(byte[] encodedKey) throws InvalidKeyException {
        try {
            decode(new DerValue(encodedKey));
        } catch (IOException e) {
            throw new InvalidKeyException("Unable to decode key", e);
        }
    }

    /**
     * Serialization write ... X.509 keys serialize as
     * themselves, and they're parsed when they get read back.
     */
    @java.io.Serial
    private void writeObject(ObjectOutputStream stream) throws IOException {
        stream.write(getEncoded());
    }

    /**
     * Serialization read ... X.509 keys serialize as
     * themselves, and they're parsed when they get read back.
     */
    @java.io.Serial
    private void readObject(ObjectInputStream stream) throws IOException {
        try {
            decode(new DerValue(stream));
        } catch (InvalidKeyException e) {
            throw new IOException("deserialized key is invalid", e);
        }
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        }
        if (!(obj instanceof Key)) {
            return false;
        }
        byte[] thisEncoded = this.getEncodedInternal();
        byte[] otherEncoded;
        if (obj instanceof X509Key) {
            otherEncoded = ((X509Key) obj).getEncodedInternal();
        } else {
            otherEncoded = ((Key) obj).getEncoded();
        }
        return Arrays.equals(thisEncoded, otherEncoded);
    }

    /**
     * Calculates a hash code value for the object. Objects
     * which are equal will also have the same hashcode.
     */
    @Override
    public int hashCode() {
        return Arrays.hashCode(getEncodedInternal());
    }

    /*
     * Produce SubjectPublicKey encoding from algorithm id and key material.
     */
    static void encode(DerOutputStream out, AlgorithmId algid, BitArray key) {
            DerOutputStream tmp = new DerOutputStream();
            algid.encode(tmp);
            tmp.putUnalignedBitString(key);
            out.write(DerValue.tag_Sequence, tmp);
    }
}