I have several e-mail accounts on several mail servers and I found myself in a situation when I needed more flexibility in the way I set up my vacation message. Being involved in several open source projects and subscribed to many open mailing lists, I needed to make sure I don’t spam those lists or users of those lists (who may not know me) with my vacation auto-replies. Even people I do want to notify don’t need to get my auto-reply to every message that reaches me – notification once in several days is good enough. And I needed to customize the vacation message for internal recipients (e.g. providing links to internal resources) and have it slightly more detailed than the auto-replies that go to external people.

So, a couple of months back, the weekend before my summer vacation I sat down and implemented a simple utility that provides me with this flexibility. Since then I used it several times, fixed a few issues, and Alexis (a colleague of mine) contributed some more improvements. At this point I am pretty confident the tool works smoothly, so decided to release version 1.0. Give it a try if you are in a similar situation – the tool and the source code are available at http://hg.alutam.com/ooomailer.

• Un-/marshalling collection types
  Until 1.9.1, JAXB un-/marshalling in Jersey worked only for Collection and List interfaces. I.e. if your resource method returned (or took as a parameter) Collection<Foo> or List<Foo> (where Foo was a JAXB bean), de-/serialization from/to XML/JSON would work, but if it returned LinkedList<Foo> or Set<Foo> or any other Collection subtype, it would not work. This is fixed in 1.9.1 and you can now return and retrieve any well-known interfaces that extend Collection (such as Set, Queue, etc.) and their implementations which have default public constructor.
• PostReplaceFilter improvements
  PostReplaceFilter can be used to support clients which can’t send the full range of HTTP methods. It enables converting POST requests to other methods such as PUT or DELETE. If a POST request comes with a different method specified in X-HTTP-Method-Override header, the filter will replace POST in the request with that specified method. This has been in Jersey for a while, but only supported method overriding using the X-HTTP-Method-Override header. In 1.9.1 you can now use “_method” query parameter as well, and when overriding POST to GET the filter will convert all the form parameters to query parameters. Whether both header and query parameter are looked at by the filter (or only the header or only the query parameter) is configurable. Thanks to gk5885, Fredy Nagy and Florian Hars for sharing their views and patches.

import java.io.IOException;
import java.io.InputStream;

public class ZipDecryptInputStream extends InputStream {
    private static final int[] CRC_TABLE = new int[256];
    // compute the table
    // (could also have it pre-computed - see http://snippets.dzone.com/tag/crc32)
    static {
        for (int i = 0; i < 256; i++) {
            int r = i;
            for (int j = 0; j < 8; j++) {
                if ((r & 1) == 1) {
                    r = (r >>> 1) ^ 0xedb88320;
                } else {
                    r >>>= 1;
                }
            }
            CRC_TABLE[i] = r;
        }
    }

    private static final int DECRYPT_HEADER_SIZE = 12;
    private static final int[] LFH_SIGNATURE = {0x50, 0x4b, 0x03, 0x04};

    private final InputStream delegate;
    private final String password;
    private final int keys[] = new int[3];

    private State state = State.SIGNATURE;
    private int skipBytes;
    private int compressedSize;
    private int value;
    private int valuePos;
    private int valueInc;

    public ZipDecryptInputStream(InputStream stream, String password) {
        this.delegate = stream;
        this.password = password;
    }

    @Override
    public int read() throws IOException {
        int result = delegate.read();
        if (skipBytes == 0) {
            switch (state) {
                case SIGNATURE:
                    if (result != LFH_SIGNATURE[valuePos]) {
                        state = State.TAIL;
                    } else {
                        valuePos++;
                        if (valuePos >= LFH_SIGNATURE.length) {
                            skipBytes = 2;
                            state = State.FLAGS;
                        }
                    }
                    break;
                case FLAGS:
                    if ((result & 1) == 0) {
                        throw new IllegalStateException("ZIP not password protected.");
                    }
                    if ((result & 64) == 64) {
                        throw new IllegalStateException("Strong encryption used.");
                    }
                    if ((result & 8) == 8) {
                        throw new IllegalStateException("Unsupported ZIP format.");
                    }
                    result -= 1;
                    compressedSize = 0;
                    valuePos = 0;
                    valueInc = DECRYPT_HEADER_SIZE;
                    state = State.COMPRESSED_SIZE;
                    skipBytes = 11;
                    break;
                case COMPRESSED_SIZE:
                    compressedSize += result << (8 * valuePos);
                    result -= valueInc;
                    if (result < 0) {
                        valueInc = 1;
                        result += 256;
                    } else {
                        valueInc = 0;
                    }
                    valuePos++;
                    if (valuePos > 3) {
                        valuePos = 0;
                        value = 0;
                        state = State.FN_LENGTH;
                        skipBytes = 4;
                    }
                    break;
                case FN_LENGTH:
                case EF_LENGTH:
                    value += result << 8 * valuePos;
                    if (valuePos == 1) {
                        valuePos = 0;
                        if (state == State.FN_LENGTH) {
                            state = State.EF_LENGTH;
                        } else {
                            state = State.HEADER;
                            skipBytes = value;
                        }
                    } else {
                        valuePos = 1;
                    }
                    break;
                case HEADER:
                    initKeys(password);
                    for (int i = 0; i < DECRYPT_HEADER_SIZE; i++) {
                        updateKeys((byte) (result ^ decryptByte()));
                        result = delegate.read();
                    }
                    compressedSize -= DECRYPT_HEADER_SIZE;
                    state = State.DATA;
                    // intentionally no break
                case DATA:
                    result = (result ^ decryptByte()) & 0xff;
                    updateKeys((byte) result);
                    compressedSize--;
                    if (compressedSize == 0) {
                        valuePos = 0;
                        state = State.SIGNATURE;
                    }
                    break;
                case TAIL:
                    // do nothing
            }
        } else {
            skipBytes--;
        }
        return result;
    }

    @Override
    public void close() throws IOException {
        delegate.close();
        super.close();
    }

    private void initKeys(String password) {
        keys[0] = 305419896;
        keys[1] = 591751049;
        keys[2] = 878082192;
        for (int i = 0; i < password.length(); i++) {
            updateKeys((byte) (password.charAt(i) & 0xff));
        }
    }

    private void updateKeys(byte charAt) {
        keys[0] = crc32(keys[0], charAt);
        keys[1] += keys[0] & 0xff;
        keys[1] = keys[1] * 134775813 + 1;
        keys[2] = crc32(keys[2], (byte) (keys[1] >> 24));
    }

    private byte decryptByte() {
        int temp = keys[2] | 2;
        return (byte) ((temp * (temp ^ 1)) >>> 8);
    }

    private int crc32(int oldCrc, byte charAt) {
        return ((oldCrc >>> 8) ^ CRC_TABLE[(oldCrc ^ charAt) & 0xff]);
    }

    private static enum State {
        SIGNATURE, FLAGS, COMPRESSED_SIZE, FN_LENGTH, EF_LENGTH, HEADER, DATA, TAIL
    }
}

These are the limitations:

• Only the “Traditional PKWARE Encryption” is supported (spec. section VII)
• Files that have the “compressed length” information at the end of the data section (rather than at the beginning) are not supported (see “general purpose bit flag”, bit 3 in section V, subsection J in the spec.)

And this is how you can use it in your code:

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.zip.ZipEntry;
import java.util.zip.ZipInputStream;

// usage: java Main [filename] [password]
public class Main {
    public static void main(String[] args) throws IOException {
        // password-protected zip file I need to read
        FileInputStream fis = new FileInputStream(args[0]);
        // wrap it in the decrypt stream
        ZipDecryptInputStream zdis = new ZipDecryptInputStream(fis, args[1]);
        // wrap the decrypt stream by the ZIP input stream
        ZipInputStream zis = new ZipInputStream(zdis);

        // read all the zip entries and save them as files
        ZipEntry ze;
        while ((ze = zis.getNextEntry()) != null) {
            FileOutputStream fos = new FileOutputStream(ze.getName());
            int b;
            while ((b = zis.read()) != -1) {
                fos.write(b);
            }
            fos.close();
            zis.closeEntry();
        }
        zis.close();
    }
}