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keep track of event ID and timestamp of decrypted messages

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This is to avoid false positives when detecting replay attacks.

fixes: vector-im/riot-web#3712

Signed-off-by: Hubert Chathi <hubert@uhoreg.ca>
This commit is contained in:
Hubert Chathi
2017-10-11 22:49:44 -04:00
parent f5f8867326
commit 8f252992e4
3 changed files with 109 additions and 7 deletions
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83
spec/unit/crypto/algorithms/megolm.spec.js
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@ -181,5 +181,88 @@ describe("MegolmDecryption", function() {
expect(payload.content.session_key).toExist();
});
});
it("can detect replay attacks", function() {
// trying to decrypt two different messages (marked by different
// event IDs or timestamps) using the same (sender key, session id,
// message index) triple should result in an exception being thrown
// as it should be detected as a replay attack.
const sessionId = groupSession.session_id();
const cipherText = groupSession.encrypt(JSON.stringify({
room_id: ROOM_ID,
content: 'testytest',
}));
const event1 = new MatrixEvent({
type: 'm.room.encrypted',
room_id: ROOM_ID,
content: {
algorithm: 'm.megolm.v1.aes-sha2',
sender_key: "SENDER_CURVE25519",
session_id: sessionId,
ciphertext: cipherText,
},
event_id: "$event1",
origin_server_ts: 1507753886000,
});
const successHandler = expect.createSpy();
const failureHandler = expect.createSpy()
.andCall((err) => {
expect(err.toString()).toMatch(
/Duplicate message index, possible replay attack/,
);
});
return megolmDecryption.decryptEvent(event1).then((res) => {
const event2 = new MatrixEvent({
type: 'm.room.encrypted',
room_id: ROOM_ID,
content: {
algorithm: 'm.megolm.v1.aes-sha2',
sender_key: "SENDER_CURVE25519",
session_id: sessionId,
ciphertext: cipherText,
},
event_id: "$event2",
origin_server_ts: 1507754149000,
});
return megolmDecryption.decryptEvent(event2);
}).then(
successHandler,
failureHandler,
).then(() => {
expect(successHandler).toNotHaveBeenCalled();
expect(failureHandler).toHaveBeenCalled();
});
});
it("allows re-decryption of the same event", function() {
// in contrast with the previous test, if the event ID and
// timestamp are the same, then it should not be considered a
// replay attack
const sessionId = groupSession.session_id();
const cipherText = groupSession.encrypt(JSON.stringify({
room_id: ROOM_ID,
content: 'testytest',
}));
const event = new MatrixEvent({
type: 'm.room.encrypted',
room_id: ROOM_ID,
content: {
algorithm: 'm.megolm.v1.aes-sha2',
sender_key: "SENDER_CURVE25519",
session_id: sessionId,
ciphertext: cipherText,
},
event_id: "$event1",
origin_server_ts: 1507753886000,
});
return megolmDecryption.decryptEvent(event).then((res) => {
return megolmDecryption.decryptEvent(event);
// test is successful if no exception is thrown
});
});
});
});