Message parser and encoder.

components/net/sf/briar/protocol/MessageEncoderImpl.java

@@ -0,0 +1,63 @@
+package net.sf.briar.protocol;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.security.GeneralSecurityException;
+import java.security.KeyPair;
+import java.security.MessageDigest;
+import java.security.Signature;
+
+import net.sf.briar.api.protocol.AuthorId;
+import net.sf.briar.api.protocol.GroupId;
+import net.sf.briar.api.protocol.Message;
+import net.sf.briar.api.protocol.MessageEncoder;
+import net.sf.briar.api.protocol.MessageId;
+import net.sf.briar.api.serial.Writer;
+import net.sf.briar.api.serial.WriterFactory;
+
+class MessageEncoderImpl implements MessageEncoder {
+
+	private final Signature signature;
+	private final MessageDigest messageDigest;
+	private final WriterFactory writerFactory;
+
+	MessageEncoderImpl(Signature signature, MessageDigest messageDigest,
+			WriterFactory writerFactory) {
+		this.signature = signature;
+		this.messageDigest = messageDigest;
+		this.writerFactory = writerFactory;
+	}
+
+	public Message encodeMessage(MessageId parent, GroupId group, String nick,
+			KeyPair keyPair, byte[] body) throws IOException,
+			GeneralSecurityException {
+		long timestamp = System.currentTimeMillis();
+		byte[] encodedKey = keyPair.getPublic().getEncoded();
+		ByteArrayOutputStream out = new ByteArrayOutputStream();
+		Writer w = writerFactory.createWriter(out);
+		w.writeRaw(parent);
+		w.writeRaw(group);
+		w.writeInt64(timestamp);
+		w.writeUtf8(nick);
+		w.writeRaw(encodedKey);
+		w.writeRaw(body);
+		byte[] signable = out.toByteArray();
+		signature.initSign(keyPair.getPrivate());
+		signature.update(signable);
+		byte[] sig = signature.sign();
+		w.writeRaw(sig);
+		byte[] raw = out.toByteArray();
+		w.close();
+		// The message ID is the hash of the entire message
+		messageDigest.reset();
+		messageDigest.update(raw);
+		MessageId id = new MessageId(messageDigest.digest());
+		// The author ID is the hash of the author's nick and public key
+		messageDigest.reset();
+		messageDigest.update(nick.getBytes("UTF-8"));
+		messageDigest.update((byte) 0); // Null separator
+		messageDigest.update(encodedKey);
+		AuthorId author = new AuthorId(messageDigest.digest());
+		return new MessageImpl(id, parent, group, author, timestamp, raw);
+	}
+}

components/net/sf/briar/protocol/MessageImpl.java

@@ -12,16 +12,16 @@ public class MessageImpl implements Message {
 	private final GroupId group;
 	private final AuthorId author;
 	private final long timestamp;
-	private final byte[] body;
+	private final byte[] raw;
 
 	public MessageImpl(MessageId id, MessageId parent, GroupId group,
-			AuthorId author, long timestamp, byte[] body) {
+			AuthorId author, long timestamp, byte[] raw) {
 		this.id = id;
 		this.parent = parent;
 		this.group = group;
 		this.author = author;
 		this.timestamp = timestamp;
-		this.body = body;
+		this.raw = raw;
 	}
 
 	public MessageId getId() {
@@ -45,11 +45,11 @@ public class MessageImpl implements Message {
 	}
 
 	public int getSize() {
-		return body.length;
+		return raw.length;
 	}
 
 	public byte[] getBytes() {
-		return body;
+		return raw;
 	}
 
 	@Override

components/net/sf/briar/protocol/MessageParserImpl.java

@@ -0,0 +1,84 @@
+package net.sf.briar.protocol;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.security.GeneralSecurityException;
+import java.security.MessageDigest;
+import java.security.PublicKey;
+import java.security.Signature;
+import java.security.SignatureException;
+
+import net.sf.briar.api.crypto.KeyParser;
+import net.sf.briar.api.protocol.AuthorId;
+import net.sf.briar.api.protocol.GroupId;
+import net.sf.briar.api.protocol.Message;
+import net.sf.briar.api.protocol.MessageId;
+import net.sf.briar.api.protocol.MessageParser;
+import net.sf.briar.api.protocol.UniqueId;
+import net.sf.briar.api.serial.FormatException;
+import net.sf.briar.api.serial.Reader;
+import net.sf.briar.api.serial.ReaderFactory;
+
+class MessageParserImpl implements MessageParser {
+
+	private final KeyParser keyParser;
+	private final Signature signature;
+	private final MessageDigest messageDigest;
+	private final ReaderFactory readerFactory;
+
+	MessageParserImpl(KeyParser keyParser, Signature signature,
+			MessageDigest messageDigest, ReaderFactory readerFactory) {
+		this.keyParser = keyParser;
+		this.signature = signature;
+		this.messageDigest = messageDigest;
+		this.readerFactory = readerFactory;
+	}
+
+	public Message parseMessage(byte[] raw) throws IOException,
+			GeneralSecurityException {
+		if(raw.length > Message.MAX_SIZE) throw new FormatException();
+		ByteArrayInputStream in = new ByteArrayInputStream(raw);
+		Reader r = readerFactory.createReader(in);
+		// Read the parent message ID
+		byte[] idBytes = r.readRaw();
+		if(idBytes.length != UniqueId.LENGTH) throw new FormatException();
+		MessageId parent = new MessageId(idBytes);
+		// Read the group ID
+		idBytes = r.readRaw();
+		if(idBytes.length != UniqueId.LENGTH) throw new FormatException();
+		GroupId group = new GroupId(idBytes);
+		// Read the timestamp
+		long timestamp = r.readInt64();
+		// Hash the author's nick and public key to get the author ID
+		String nick = r.readUtf8();
+		byte[] encodedKey = r.readRaw();
+		PublicKey publicKey = keyParser.parsePublicKey(encodedKey);
+		messageDigest.reset();
+		messageDigest.update(nick.getBytes("UTF-8"));
+		messageDigest.update((byte) 0); // Null separator
+		messageDigest.update(encodedKey);
+		AuthorId author = new AuthorId(messageDigest.digest());
+		// Skip the message body
+		r.readRaw();
+		// Read the signature and work out how long the signed message is
+		byte[] sig = r.readRaw();
+		int length = raw.length - sig.length - bytesToEncode(sig.length);
+		// Verify the signature
+		signature.initVerify(publicKey);
+		signature.update(raw, 0, length);
+		if(!signature.verify(sig)) throw new SignatureException();
+		// Hash the message, including the signature, to get the message ID
+		messageDigest.reset();
+		messageDigest.update(raw);
+		MessageId id = new MessageId(messageDigest.digest());
+		return new MessageImpl(id, parent, group, author, timestamp, raw);
+	}
+
+	// FIXME: Work out a better way of doing this
+	private int bytesToEncode(int i) {
+		if(i >= 0 && i <= Byte.MAX_VALUE) return 2;
+		if(i >= Byte.MIN_VALUE && i <= Byte.MAX_VALUE) return 3;
+		if(i >= Short.MIN_VALUE && i <= Short.MAX_VALUE) return 4;
+		return 6;
+	}
+}