Check the return value from Signature.verify(). *cough*

api/net/sf/briar/api/protocol/BatchBuilder.java

@@ -1,8 +1,7 @@
 package net.sf.briar.api.protocol;
 
 import java.io.IOException;
-import java.security.InvalidKeyException;
+import java.security.GeneralSecurityException;
-import java.security.SignatureException;
 
 public interface BatchBuilder {
 
@@ -13,5 +12,5 @@ public interface BatchBuilder {
 	void setSignature(byte[] sig);
 
 	/** Builds and returns the batch. */
-	Batch build() throws IOException, SignatureException, InvalidKeyException;
+	Batch build() throws IOException, GeneralSecurityException;
 }

api/net/sf/briar/api/protocol/HeaderBuilder.java

@@ -1,8 +1,7 @@
 package net.sf.briar.api.protocol;
 
 import java.io.IOException;
-import java.security.InvalidKeyException;
+import java.security.GeneralSecurityException;
-import java.security.SignatureException;
 import java.util.Map;
 
 public interface HeaderBuilder {
@@ -20,5 +19,5 @@ public interface HeaderBuilder {
 	void setSignature(byte[] sig);
 
 	/** Builds and returns the header. */
-	Header build() throws IOException, SignatureException, InvalidKeyException;
+	Header build() throws IOException, GeneralSecurityException;
 }

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

@@ -1,7 +1,7 @@
 package net.sf.briar.protocol;
 
 import java.io.IOException;
-import java.security.InvalidKeyException;
+import java.security.GeneralSecurityException;
 import java.security.KeyPair;
 import java.security.MessageDigest;
 import java.security.Signature;
@@ -24,13 +24,12 @@ public class IncomingBatchBuilder extends BatchBuilderImpl {
 		this.sig = sig;
 	}
 
-	public Batch build() throws IOException, SignatureException,
+	public Batch build() throws IOException, GeneralSecurityException {
-	InvalidKeyException {
 		if(sig == null) throw new IllegalStateException();
 		byte[] raw = getSignableRepresentation();
 		signature.initVerify(keyPair.getPublic());
 		signature.update(raw);
-		signature.verify(sig);
+		if(!signature.verify(sig)) throw new SignatureException();
 		messageDigest.reset();
 		messageDigest.update(raw);
 		messageDigest.update(sig);

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

@@ -1,7 +1,7 @@
 package net.sf.briar.protocol;
 
 import java.io.IOException;
-import java.security.InvalidKeyException;
+import java.security.GeneralSecurityException;
 import java.security.KeyPair;
 import java.security.MessageDigest;
 import java.security.Signature;
@@ -28,13 +28,12 @@ class IncomingHeaderBuilder extends HeaderBuilderImpl {
 		this.sig = sig;
 	}
 
-	public Header build() throws IOException, SignatureException,
+	public Header build() throws IOException, GeneralSecurityException {
-	InvalidKeyException {
 		if(sig == null) throw new IllegalStateException();
 		byte[] raw = getSignableRepresentation();
 		signature.initVerify(keyPair.getPublic());
 		signature.update(raw);
-		signature.verify(sig);
+		if(!signature.verify(sig)) throw new SignatureException();
 		messageDigest.reset();
 		messageDigest.update(raw);
 		messageDigest.update(sig);

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

@@ -1,11 +1,10 @@
 package net.sf.briar.protocol;
 
 import java.io.IOException;
-import java.security.InvalidKeyException;
+import java.security.GeneralSecurityException;
 import java.security.KeyPair;
 import java.security.MessageDigest;
 import java.security.Signature;
-import java.security.SignatureException;
 
 import net.sf.briar.api.protocol.Batch;
 import net.sf.briar.api.protocol.BatchId;
@@ -22,8 +21,7 @@ public class OutgoingBatchBuilder extends BatchBuilderImpl {
 		throw new UnsupportedOperationException();
 	}
 
-	public Batch build() throws IOException, SignatureException,
+	public Batch build() throws IOException, GeneralSecurityException {
-	InvalidKeyException {
 		byte[] raw = getSignableRepresentation();
 		signature.initSign(keyPair.getPrivate());
 		signature.update(raw);

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

@@ -1,11 +1,10 @@
 package net.sf.briar.protocol;
 
 import java.io.IOException;
-import java.security.InvalidKeyException;
+import java.security.GeneralSecurityException;
 import java.security.KeyPair;
 import java.security.MessageDigest;
 import java.security.Signature;
-import java.security.SignatureException;
 import java.util.HashSet;
 import java.util.Set;
 
@@ -26,8 +25,7 @@ public class OutgoingHeaderBuilder extends HeaderBuilderImpl {
 		throw new UnsupportedOperationException();
 	}
 
-	public Header build() throws IOException, SignatureException,
+	public Header build() throws IOException, GeneralSecurityException {
-	InvalidKeyException {
 		byte[] raw = getSignableRepresentation();
 		signature.initSign(keyPair.getPrivate());
 		signature.update(raw);

test/net/sf/briar/protocol/BundleReadWriteTest.java

@@ -3,6 +3,8 @@ package net.sf.briar.protocol;
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
+import java.io.RandomAccessFile;
+import java.security.GeneralSecurityException;
 import java.security.KeyPair;
 import java.security.KeyPairGenerator;
 import java.security.MessageDigest;
@@ -149,6 +151,55 @@ public class BundleReadWriteTest extends TestCase {
 		r.close();
 	}
 
+
+	@Test
+	public void testModifyingBundleBreaksSignature() throws Exception {
+
+		testWriteBundle();
+
+		RandomAccessFile f = new RandomAccessFile(bundle, "rw");
+		f.seek(bundle.length() - 50);
+		byte b = f.readByte();
+		f.seek(bundle.length() - 50);
+		f.writeByte(b + 1);
+		f.close();
+
+		MessageParser messageParser = new MessageParser() {
+			public Message parseMessage(byte[] body) throws FormatException,
+			SignatureException {
+				// FIXME: Really parse the message
+				return message;
+			}
+		};
+		Provider<HeaderBuilder> headerBuilderProvider =
+			new Provider<HeaderBuilder>() {
+			public HeaderBuilder get() {
+				return new IncomingHeaderBuilder(keyPair, sig, digest, wf);
+			}
+		};
+		Provider<BatchBuilder> batchBuilderProvider =
+			new Provider<BatchBuilder>() {
+			public BatchBuilder get() {
+				return new IncomingBatchBuilder(keyPair, sig, digest, wf);
+			}
+		};
+
+		FileInputStream in = new FileInputStream(bundle);
+		Reader reader = new ReaderFactoryImpl().createReader(in);
+		BundleReader r = new BundleReaderImpl(reader, bundle.length(),
+				messageParser, headerBuilderProvider, batchBuilderProvider);
+
+		Header h = r.getHeader();
+		assertEquals(acks, h.getAcks());
+		assertEquals(subs, h.getSubscriptions());
+		assertEquals(transports, h.getTransports());
+		try {
+			r.getNextBatch();
+			assertTrue(false);
+		} catch(GeneralSecurityException expected) {}
+		r.close();
+	}
+
 	@After
 	public void tearDown() {
 		TestUtils.deleteTestDirectory(testDir);