de.schlichtherle.truezip.zip.WinZipAesEntryExtraField Maven / Gradle / Ivy

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The file system driver family for ZIP and related archive file types. Add the JAR artifact of this module to the run time class path to make its file system drivers available for service location in the client API modules.

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/*
 * Copyright (C) 2005-2013 Schlichtherle IT Services.
 * All rights reserved. Use is subject to license terms.
 */
package de.schlichtherle.truezip.zip;

import de.schlichtherle.truezip.crypto.param.AesKeyStrength;
import static de.schlichtherle.truezip.crypto.param.AesKeyStrength.BITS_128;
import static de.schlichtherle.truezip.zip.LittleEndian.readUShort;
import static de.schlichtherle.truezip.zip.LittleEndian.writeShort;
import javax.annotation.concurrent.NotThreadSafe;

/**
 * WinZip AES Extra Field.
 *
 * @since   TrueZIP 7.3
 * @see     AES Encryption Information: Encryption Specification AE-1 and AE-2 (WinZip Computing, S.L.)
 * @see     AES Coding Tips for Developers (WinZip Computing, S.L.)
 * @see     RawZipOutputStream$WinZipAesOutputMethod
 * @author  Christian Schlichtherle
 */
@NotThreadSafe
final class WinZipAesEntryExtraField extends ExtraField {

    private static final int DATA_SIZE = 7;
    private static final int VENDOR_ID = 'A' | ('E' << 8);
    private static final AesKeyStrength[] KEY_STRENGTHS = AesKeyStrength.values();

    /**
     * Entries of this type do include the standard ZIP CRC-32
     * value.
     * For use with {@link #setVendorVersion(int)}/{@link #getVendorVersion()}.
     */
    static final int VV_AE_1 = 1;

    /**
     * Entries of this type do not include the standard ZIP CRC-32
     * value.
     * For use with {@link #setVendorVersion(int)}/{@link #getVendorVersion()}.
     */
    static final int VV_AE_2 = 2;

    private short vendorVersion = VV_AE_1;
    private byte encryptionStrength = encryptionStrength(BITS_128);
    private short method;

    /**
     * Constructs a new WinZip AES Extra Field.
     */
    WinZipAesEntryExtraField() {
    }

    private static byte encryptionStrength(AesKeyStrength keyStrength) {
        return (byte) (keyStrength.ordinal() + 1);
    }

    private static AesKeyStrength keyStrength(int encryptionStrength) {
        return KEY_STRENGTHS[(encryptionStrength - 1) & UByte.MAX_VALUE];
    }

    @Override
    int getHeaderId() {
        return WINZIP_AES_ID;
    }

    @Override
    int getDataSize() {
        return DATA_SIZE;
    }

    /**
     * Returns the vendor version.
     *
     * @see #VV_AE_1
     * @see #VV_AE_2
     */
    int getVendorVersion() {
        return vendorVersion & UShort.MAX_VALUE;
    }

    /**
     * Sets the vendor version.
     *
     * @see    #VV_AE_1
     * @see    #VV_AE_2
     * @param  vendorVersion the vendor version.
     * @throws IllegalArgumentException
     */
    void setVendorVersion(final int vendorVersion) {
        if (vendorVersion < VV_AE_1 || VV_AE_2 < vendorVersion)
            throw new IllegalArgumentException("" + vendorVersion);
        this.vendorVersion = (short) vendorVersion;
    }

    int getVendorId() {
        return VENDOR_ID;
    }

    AesKeyStrength getKeyStrength() {
        return keyStrength(this.encryptionStrength);
    }

    void setKeyStrength(final AesKeyStrength keyStrength) {
        this.encryptionStrength = encryptionStrength(keyStrength);
    }

    int getMethod() {
        return method & UShort.MAX_VALUE;
    }

    void setMethod(final int compressionMethod) {
        assert UShort.check(compressionMethod);
        this.method = (short) compressionMethod;
    }

    @Override
    void readFrom(final byte[] buf, int off, final int len) {
        if (DATA_SIZE != len) throw new IllegalArgumentException();
        setVendorVersion(readUShort(buf, off));
        off += 2;
        final int vendorId = (short) readUShort(buf, off);
        off += 2;
        if (VENDOR_ID != vendorId) throw new IllegalArgumentException();
        setKeyStrength(keyStrength(buf[off])); // checked
        off += 1;
        setMethod(readUShort(buf, off));
        // off += 2;
    }

    @Override
    void writeTo(byte[] buf, int off) {
        writeShort(this.vendorVersion, buf, off);
        off += 2;
        writeShort(VENDOR_ID, buf, off);
        off += 2;
        buf[off] = this.encryptionStrength;
        off += 1;
        writeShort(this.method, buf, off);
        // off += 2;
    }
}