net.java.truevfs.comp.zip.WinZipAesExtraField Maven / Gradle / Ivy

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Provides basic functionality for reading and writing ZIP files.
There is a newer version: 0.14.0
/*
 * Copyright (C) 2005-2015 Schlichtherle IT Services.
 * All rights reserved. Use is subject to license terms.
 */
package net.java.truevfs.comp.zip;

import javax.annotation.concurrent.NotThreadSafe;
import net.java.truecommons.key.spec.common.AesKeyStrength;
import static net.java.truecommons.key.spec.common.AesKeyStrength.BITS_128;
import static net.java.truevfs.comp.zip.LittleEndian.readUShort;
import static net.java.truevfs.comp.zip.LittleEndian.writeShort;

/**
 * WinZip AES Extra Field.
 *
 * @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 WinZipAesExtraField 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;

    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;
    }
}