Distinguish between recoverable and unrecoverable errors.

components/net/sf/briar/transport/ConnectionReaderFactoryImpl.java

@@ -49,9 +49,9 @@ class ConnectionReaderFactoryImpl implements ConnectionReaderFactory {
 		// No error correction
 		IncomingErrorCorrectionLayer correcter =
 			new NullIncomingErrorCorrectionLayer(decrypter);
-		// Create the reader
+		// Create the reader - don't tolerate errors
 		Mac mac = crypto.getMac();
-		return new ConnectionReaderImpl(correcter, mac, macKey);
+		return new ConnectionReaderImpl(correcter, mac, macKey, false);
 	}
 
 	public ConnectionReader createConnectionReader(SegmentSource in,
@@ -80,8 +80,8 @@ class ConnectionReaderFactoryImpl implements ConnectionReaderFactory {
 		// No error correction
 		IncomingErrorCorrectionLayer correcter =
 			new NullIncomingErrorCorrectionLayer(decrypter);
-		// Create the reader
+		// Create the reader - don't tolerate errors
 		Mac mac = crypto.getMac();
-		return new ConnectionReaderImpl(correcter, mac, macKey);
+		return new ConnectionReaderImpl(correcter, mac, macKey, false);
 	}
 }

components/net/sf/briar/transport/ConnectionReaderImpl.java

@@ -20,15 +20,17 @@ class ConnectionReaderImpl extends InputStream implements ConnectionReader {
 
 	private final IncomingErrorCorrectionLayer in;
 	private final Mac mac;
+	private final boolean tolerateErrors;
 	private final Frame frame;
 
 	private long frameNumber = 0L;
 	private int offset = 0, length = 0;
 
 	ConnectionReaderImpl(IncomingErrorCorrectionLayer in, Mac mac,
-			ErasableKey macKey) {
+			ErasableKey macKey, boolean tolerateErrors) {
 		this.in = in;
 		this.mac = mac;
+		this.tolerateErrors = tolerateErrors;
 		// Initialise the MAC
 		try {
 			mac.init(macKey);
@@ -47,7 +49,7 @@ class ConnectionReaderImpl extends InputStream implements ConnectionReader {
 
 	@Override
 	public int read() throws IOException {
-		while(length == 0) if(!readFrame()) return -1;
+		while(length == 0) if(!readValidFrame()) return -1;
 		int b = frame.getBuffer()[offset] & 0xff;
 		offset++;
 		length--;
@@ -61,7 +63,7 @@ class ConnectionReaderImpl extends InputStream implements ConnectionReader {
 
 	@Override
 	public int read(byte[] b, int off, int len) throws IOException {
-		while(length == 0) if(!readFrame()) return -1;
+		while(length == 0) if(!readValidFrame()) return -1;
 		len = Math.min(len, length);
 		System.arraycopy(frame.getBuffer(), offset, b, off, len);
 		offset += len;
@@ -69,33 +71,46 @@ class ConnectionReaderImpl extends InputStream implements ConnectionReader {
 		return len;
 	}
 
-	private boolean readFrame() throws IOException {
+	private boolean readValidFrame() throws IOException {
+		while(true) {
+			try {
+				return readFrame();
+			} catch(InvalidDataException e) {
+				if(tolerateErrors) continue;
+				throw new FormatException();
+			}
+		}
+	}
+
+	private boolean readFrame() throws IOException, InvalidDataException {
 		assert length == 0;
 		// Don't allow more than 2^32 frames to be read
-		if(frameNumber > MAX_32_BIT_UNSIGNED) throw new IllegalStateException();
+		if(frameNumber > MAX_32_BIT_UNSIGNED)
+			throw new IllegalStateException();
 		// Read a frame
 		Collection<Long> window = Collections.singleton(frameNumber);
 		if(!in.readFrame(frame, window)) return false;
 		// Check that the frame number is correct and the length is legal
 		byte[] buf = frame.getBuffer();
 		if(!HeaderEncoder.validateHeader(buf, frameNumber))
-			throw new FormatException();
+			throw new InvalidDataException();
 		// Check that the payload and padding lengths are correct
 		int payload = HeaderEncoder.getPayloadLength(buf);
 		int padding = HeaderEncoder.getPaddingLength(buf);
 		if(frame.getLength() != FRAME_HEADER_LENGTH + payload + padding
-				+ MAC_LENGTH) throw new FormatException();
+				+ MAC_LENGTH) throw new InvalidDataException();
 		// Check that the padding is all zeroes
 		int paddingStart = FRAME_HEADER_LENGTH + payload;
 		for(int i = paddingStart; i < paddingStart + padding; i++) {
-			if(buf[i] != 0) throw new FormatException();
+			if(buf[i] != 0) throw new InvalidDataException();
 		}
 		// Check the MAC
 		int macStart = FRAME_HEADER_LENGTH + payload + padding;
 		mac.update(buf, 0, macStart);
 		byte[] expectedMac = mac.doFinal();
 		for(int i = 0; i < expectedMac.length; i++) {
-			if(expectedMac[i] != buf[macStart + i]) throw new FormatException();
+			if(expectedMac[i] != buf[macStart + i])
+				throw new InvalidDataException();
 		}
 		offset = FRAME_HEADER_LENGTH;
 		length = payload;

components/net/sf/briar/transport/IncomingEncryptionLayer.java

@@ -9,6 +9,10 @@ interface IncomingEncryptionLayer {
 	/**
 	 * Reads a segment, excluding its tag, into the given buffer. Returns false
 	 * if no more segments can be read from the connection.
+	 * @throws IOException if an unrecoverable error occurs and the connection
+	 * must be closed.
+	 * @throws InvalidDataException if a recoverable error occurs. The caller
+	 * may choose whether to retry the read or close the connection.
 	 */
-	boolean readSegment(Segment s) throws IOException;
+	boolean readSegment(Segment s) throws IOException, InvalidDataException;
 }

components/net/sf/briar/transport/IncomingErrorCorrectionLayer.java

@@ -9,6 +9,11 @@ interface IncomingErrorCorrectionLayer {
 	 * Reads a frame into the given buffer. The frame number must be contained
 	 * in the given window. Returns false if no more frames can be read from
 	 * the connection.
+	 * @throws IOException if an unrecoverable error occurs and the connection
+	 * must be closed.
+	 * @throws InvalidDataException if a recoverable error occurs. The caller
+	 * may choose whether to retry the read or close the connection.
 	 */
-	boolean readFrame(Frame f, Collection<Long> window) throws IOException;
+	boolean readFrame(Frame f, Collection<Long> window) throws IOException,
+	InvalidDataException;
 }

components/net/sf/briar/transport/IncomingSegmentedEncryptionLayer.java

@@ -11,7 +11,6 @@ import java.security.GeneralSecurityException;
 import javax.crypto.Cipher;
 import javax.crypto.spec.IvParameterSpec;
 
-import net.sf.briar.api.FormatException;
 import net.sf.briar.api.crypto.ErasableKey;
 import net.sf.briar.api.plugins.SegmentSource;
 import net.sf.briar.api.transport.Segment;
@@ -32,22 +31,23 @@ class IncomingSegmentedEncryptionLayer implements IncomingEncryptionLayer {
 
 	IncomingSegmentedEncryptionLayer(SegmentSource in, Cipher tagCipher,
 			Cipher segCipher, ErasableKey tagKey, ErasableKey segKey,
-			boolean tagEverySegment, Segment s) {
+			boolean tagEverySegment, Segment bufferedSegment) {
 		this.in = in;
 		this.tagCipher = tagCipher;
 		this.segCipher = segCipher;
 		this.tagKey = tagKey;
 		this.segKey = segKey;
 		this.tagEverySegment = tagEverySegment;
+		this.bufferedSegment = bufferedSegment;
 		blockSize = segCipher.getBlockSize();
 		if(blockSize < FRAME_HEADER_LENGTH)
 			throw new IllegalArgumentException();
 		iv = IvEncoder.encodeIv(0L, blockSize);
 		segment = new SegmentImpl();
-		bufferedSegment = s;
 	}
 
-	public boolean readSegment(Segment s) throws IOException {
+	public boolean readSegment(Segment s) throws IOException,
+	InvalidDataException {
 		boolean expectTag = tagEverySegment || firstSegment;
 		firstSegment = false;
 		try {
@@ -62,14 +62,14 @@ class IncomingSegmentedEncryptionLayer implements IncomingEncryptionLayer {
 			}
 			int offset = expectTag ? TAG_LENGTH : 0;
 			int length = segment.getLength();
-			if(length > MAX_SEGMENT_LENGTH) throw new FormatException();
+			if(length > MAX_SEGMENT_LENGTH) throw new InvalidDataException();
 			if(length < offset + FRAME_HEADER_LENGTH + MAC_LENGTH)
-				throw new FormatException();
+				throw new InvalidDataException();
 			byte[] ciphertext = segment.getBuffer();
 			// If a tag is expected then decrypt and validate it
 			if(expectTag) {
 				long seg = TagEncoder.decodeTag(ciphertext, tagCipher, tagKey);
-				if(seg == -1) throw new FormatException();
+				if(seg == -1) throw new InvalidDataException();
 				segmentNumber = seg;
 			}
 			// Decrypt the segment

components/net/sf/briar/transport/InvalidDataException.java

@@ -0,0 +1,7 @@
+package net.sf.briar.transport;
+
+/** An exception that indicates a recoverable formatting error. */
+class InvalidDataException extends Exception {
+
+	private static final long serialVersionUID = 4455775710413826953L;
+}

components/net/sf/briar/transport/NullIncomingErrorCorrectionLayer.java

@@ -16,7 +16,7 @@ class NullIncomingErrorCorrectionLayer implements IncomingErrorCorrectionLayer {
 	}
 
 	public boolean readFrame(Frame f, Collection<Long> window)
-	throws IOException {
+	throws IOException, InvalidDataException {
 		while(true) {
 			if(!in.readSegment(segment)) return false;
 			byte[] buf = segment.getBuffer();