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Only remove unsigned prekey if bundled message decrypts properly.

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This commit is contained in:
Moxie Marlinspike 2014-08-04 11:36:02 -07:00
parent b147a90463
commit 006c9aae7b
4 changed files with 90 additions and 16 deletions
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2
libaxolotl/src/androidTest/java/org/whispersystems/test/InMemorySignedPreKeyStore.java
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@ -18,7 +18,7 @@ public class InMemorySignedPreKeyStore implements SignedPreKeyStore {
public SignedPreKeyRecord loadSignedPreKey(int signedPreKeyId) throws InvalidKeyIdException {
try {
if (!store.containsKey(signedPreKeyId)) {
throw new InvalidKeyIdException("No such signedprekeyrecord!");
throw new InvalidKeyIdException("No such signedprekeyrecord! " + signedPreKeyId);
}
return new SignedPreKeyRecord(store.get(signedPreKeyId));

66
libaxolotl/src/androidTest/java/org/whispersystems/test/SessionBuilderTest.java
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@ -19,13 +19,13 @@ import org.whispersystems.libaxolotl.protocol.CiphertextMessage;
import org.whispersystems.libaxolotl.protocol.KeyExchangeMessage;
import org.whispersystems.libaxolotl.protocol.PreKeyWhisperMessage;
import org.whispersystems.libaxolotl.protocol.WhisperMessage;
import org.whispersystems.libaxolotl.state.SignedPreKeyRecord;
import org.whispersystems.libaxolotl.state.SignedPreKeyStore;
import org.whispersystems.libaxolotl.state.IdentityKeyStore;
import org.whispersystems.libaxolotl.state.PreKeyBundle;
import org.whispersystems.libaxolotl.state.PreKeyRecord;
import org.whispersystems.libaxolotl.state.PreKeyStore;
import org.whispersystems.libaxolotl.state.SessionStore;
import org.whispersystems.libaxolotl.state.SignedPreKeyRecord;
import org.whispersystems.libaxolotl.state.SignedPreKeyStore;
import org.whispersystems.libaxolotl.util.Pair;
import java.util.HashSet;
@ -406,6 +406,68 @@ public class SessionBuilderTest extends AndroidTestCase {
}
public void testBadMessageBundle() throws InvalidKeyException, UntrustedIdentityException, InvalidVersionException, InvalidMessageException, DuplicateMessageException, LegacyMessageException, InvalidKeyIdException {
SessionStore aliceSessionStore = new InMemorySessionStore();
SignedPreKeyStore aliceSignedPreKeyStore = new InMemorySignedPreKeyStore();
PreKeyStore alicePreKeyStore = new InMemoryPreKeyStore();
IdentityKeyStore aliceIdentityKeyStore = new InMemoryIdentityKeyStore();
SessionBuilder aliceSessionBuilder = new SessionBuilder(aliceSessionStore, alicePreKeyStore,
aliceSignedPreKeyStore,
aliceIdentityKeyStore,
BOB_RECIPIENT_ID, 1);
SessionStore bobSessionStore = new InMemorySessionStore();
PreKeyStore bobPreKeyStore = new InMemoryPreKeyStore();
SignedPreKeyStore bobSignedPreKeyStore = new InMemorySignedPreKeyStore();
IdentityKeyStore bobIdentityKeyStore = new InMemoryIdentityKeyStore();
ECKeyPair bobPreKeyPair = Curve.generateKeyPair();
ECKeyPair bobSignedPreKeyPair = Curve.generateKeyPair();
byte[] bobSignedPreKeySignature = Curve.calculateSignature(bobIdentityKeyStore.getIdentityKeyPair().getPrivateKey(),
bobSignedPreKeyPair.getPublicKey().serialize());
PreKeyBundle bobPreKey = new PreKeyBundle(bobIdentityKeyStore.getLocalRegistrationId(), 1,
31337, bobPreKeyPair.getPublicKey(),
22, bobSignedPreKeyPair.getPublicKey(), bobSignedPreKeySignature,
bobIdentityKeyStore.getIdentityKeyPair().getPublicKey());
bobPreKeyStore.storePreKey(31337, new PreKeyRecord(bobPreKey.getPreKeyId(), bobPreKeyPair));
bobSignedPreKeyStore.storeSignedPreKey(22, new SignedPreKeyRecord(22, System.currentTimeMillis(), bobSignedPreKeyPair, bobSignedPreKeySignature));
aliceSessionBuilder.process(bobPreKey);
String originalMessage = "L'homme est condamné à être libre";
SessionCipher aliceSessionCipher = new SessionCipher(aliceSessionStore, alicePreKeyStore, aliceSignedPreKeyStore, aliceIdentityKeyStore, BOB_RECIPIENT_ID, 1);
CiphertextMessage outgoingMessageOne = aliceSessionCipher.encrypt(originalMessage.getBytes());
assertTrue(outgoingMessageOne.getType() == CiphertextMessage.PREKEY_TYPE);
byte[] goodMessage = outgoingMessageOne.serialize();
byte[] badMessage = new byte[goodMessage.length];
System.arraycopy(goodMessage, 0, badMessage, 0, badMessage.length);
badMessage[badMessage.length-10] ^= 0x01;
PreKeyWhisperMessage incomingMessage = new PreKeyWhisperMessage(badMessage);
SessionCipher bobSessionCipher = new SessionCipher(bobSessionStore, bobPreKeyStore, bobSignedPreKeyStore, bobIdentityKeyStore, ALICE_RECIPIENT_ID, 1);
byte[] plaintext = new byte[0];
try {
plaintext = bobSessionCipher.decrypt(incomingMessage);
throw new AssertionError("Decrypt should have failed!");
} catch (InvalidMessageException e) {
// good.
}
assertTrue(bobPreKeyStore.containsPreKey(31337));
plaintext = bobSessionCipher.decrypt(new PreKeyWhisperMessage(goodMessage));
assertTrue(originalMessage.equals(new String(plaintext)));
assertTrue(!bobPreKeyStore.containsPreKey(31337));
}
public void testBasicKeyExchange() throws InvalidKeyException, LegacyMessageException, InvalidMessageException, DuplicateMessageException, UntrustedIdentityException, StaleKeyExchangeException, InvalidVersionException, NoSessionException {
SessionStore aliceSessionStore = new InMemorySessionStore();
PreKeyStore alicePreKeyStore = new InMemoryPreKeyStore();

24
libaxolotl/src/main/java/org/whispersystems/libaxolotl/SessionBuilder.java
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@ -88,32 +88,34 @@ public class SessionBuilder {
* @throws org.whispersystems.libaxolotl.InvalidKeyException when the message is formatted incorrectly.
* @throws org.whispersystems.libaxolotl.UntrustedIdentityException when the {@link IdentityKey} of the sender is untrusted.
*/
/*package*/ void process(SessionRecord sessionRecord, PreKeyWhisperMessage message)
/*package*/ int process(SessionRecord sessionRecord, PreKeyWhisperMessage message)
throws InvalidKeyIdException, InvalidKeyException, UntrustedIdentityException
{
int messageVersion = message.getMessageVersion();
IdentityKey theirIdentityKey = message.getIdentityKey();
int unsignedPreKeyId;
if (!identityKeyStore.isTrustedIdentity(recipientId, theirIdentityKey)) {
throw new UntrustedIdentityException();
}
switch (messageVersion) {
case 2: processV2(sessionRecord, message); break;
case 3: processV3(sessionRecord, message); break;
case 2: unsignedPreKeyId = processV2(sessionRecord, message); break;
case 3: unsignedPreKeyId = processV3(sessionRecord, message); break;
default: throw new AssertionError("Unknown version: " + messageVersion);
}
identityKeyStore.saveIdentity(recipientId, theirIdentityKey);
return unsignedPreKeyId;
}
private void processV3(SessionRecord sessionRecord, PreKeyWhisperMessage message)
private int processV3(SessionRecord sessionRecord, PreKeyWhisperMessage message)
throws UntrustedIdentityException, InvalidKeyIdException, InvalidKeyException
{
if (sessionRecord.hasSessionState(message.getMessageVersion(), message.getBaseKey().serialize())) {
Log.w(TAG, "We've already setup a session for this V3 message, letting bundled message fall through...");
return;
return -1;
}
boolean simultaneousInitiate = sessionRecord.getSessionState().hasUnacknowledgedPreKeyMessage();
@ -145,11 +147,13 @@ public class SessionBuilder {
if (simultaneousInitiate) sessionRecord.getSessionState().setNeedsRefresh(true);
if (message.getPreKeyId() >= 0 && message.getPreKeyId() != Medium.MAX_VALUE) {
preKeyStore.removePreKey(message.getPreKeyId());
return message.getPreKeyId();
} else {
return -1;
}
}
private void processV2(SessionRecord sessionRecord, PreKeyWhisperMessage message)
private int processV2(SessionRecord sessionRecord, PreKeyWhisperMessage message)
throws UntrustedIdentityException, InvalidKeyIdException, InvalidKeyException
{
@ -157,7 +161,7 @@ public class SessionBuilder {
sessionStore.containsSession(recipientId, deviceId))
{
Log.w(TAG, "We've already processed the prekey part of this V2 session, letting bundled message fall through...");
return;
return -1;
}
ECKeyPair ourPreKey = preKeyStore.loadPreKey(message.getPreKeyId()).getKeyPair();
@ -183,7 +187,9 @@ public class SessionBuilder {
if (simultaneousInitiate) sessionRecord.getSessionState().setNeedsRefresh(true);
if (message.getPreKeyId() != Medium.MAX_VALUE) {
preKeyStore.removePreKey(message.getPreKeyId());
return message.getPreKeyId();
} else {
return -1;
}
}

14
libaxolotl/src/main/java/org/whispersystems/libaxolotl/SessionCipher.java
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@ -63,6 +63,7 @@ public class SessionCipher {
private final SessionStore sessionStore;
private final SessionBuilder sessionBuilder;
private final PreKeyStore preKeyStore;
private final long recipientId;
private final int deviceId;
@ -82,6 +83,7 @@ public class SessionCipher {
this.sessionStore = sessionStore;
this.recipientId = recipientId;
this.deviceId = deviceId;
this.preKeyStore = preKeyStore;
this.sessionBuilder = new SessionBuilder(sessionStore, preKeyStore, signedPreKeyStore,
identityKeyStore, recipientId, deviceId);
}
@ -145,12 +147,16 @@ public class SessionCipher {
InvalidKeyIdException, InvalidKeyException, UntrustedIdentityException
{
synchronized (SESSION_LOCK) {
SessionRecord sessionRecord = sessionStore.loadSession(recipientId, deviceId);
sessionBuilder.process(sessionRecord, ciphertext);
byte[] plaintext = decrypt(sessionRecord, ciphertext.getWhisperMessage());
SessionRecord sessionRecord = sessionStore.loadSession(recipientId, deviceId);
int unsignedPreKeyId = sessionBuilder.process(sessionRecord, ciphertext);
byte[] plaintext = decrypt(sessionRecord, ciphertext.getWhisperMessage());
sessionStore.storeSession(recipientId, deviceId, sessionRecord);
if (unsignedPreKeyId >=0) {
preKeyStore.removePreKey(unsignedPreKeyId);
}
return plaintext;
}
}