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Consistency checks for E2E device downloads

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Check that the user_id and device_id in device query responses match those that
we expect.

This resolves an unknown-key attack whereby Eve can re-sign Bob's keys with her
own key, thus getting Alice to send her messages which she can then forward to
Bob, making Bob think that Alice sent the messages to him.
This commit is contained in:
Richard van der Hoff
2016-10-18 13:40:13 +01:00
parent c5d738d25c
commit aafb1ffdef
2 changed files with 91 additions and 4 deletions
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24
lib/crypto/index.js
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@@ -350,9 +350,22 @@ function _updateStoredDeviceKeysForUser(_olmDevice, userId, userStore,
continue;
}
if (_storeDeviceKeys(
_olmDevice, userId, deviceId, userStore, userResult[deviceId]
)) {
var deviceResult = userResult[deviceId];
// check that the user_id and device_id in the response object are
// correct
if (deviceResult.user_id !== userId) {
console.warn("Mismatched user_id " + deviceResult.user_id +
" in keys from " + userId + ":" + deviceId);
continue;
}
if (deviceResult.device_id !== deviceId) {
console.warn("Mismatched device_id " + deviceResult.device_id +
" in keys from " + userId + ":" + deviceId);
continue;
}
if (_storeDeviceKeys(_olmDevice, userStore, deviceResult)) {
updated = true;
}
}
@@ -365,12 +378,15 @@ function _updateStoredDeviceKeysForUser(_olmDevice, userId, userStore,
*
* returns true if a change was made, else false
*/
function _storeDeviceKeys(_olmDevice, userId, deviceId, userStore, deviceResult) {
function _storeDeviceKeys(_olmDevice, userStore, deviceResult) {
if (!deviceResult.keys) {
// no keys?
return false;
}
var deviceId = deviceResult.device_id;
var userId = deviceResult.user_id;
var signKeyId = "ed25519:" + deviceId;
var signKey = deviceResult.keys[signKeyId];
if (!signKey) {