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Serialise Olm prekey decryptions

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If they overlap, they can both try to create new sessions, but this
removes the OTK so it will only work once.

Fixes https://github.com/vector-im/riot-web/issues/13229
This commit is contained in:
David Baker
2020-04-17 17:47:46 +01:00
parent 57233416d9
commit 83879fa945
2 changed files with 20 additions and 0 deletions
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17
src/crypto/algorithms/olm.js
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@@ -264,6 +264,23 @@ OlmDecryption.prototype.decryptEvent = async function(event) {
*/
OlmDecryption.prototype._decryptMessage = async function(
theirDeviceIdentityKey, message,
) {
// This is a wrapper that serialises decryptions of prekey messages, because
// otherwise we race between deciding we have no active sessions for the message
// and creating a new one, which we can only do once because it removes the OTK.
if (message.type !== 0) {
// not a prekey message: we can safely just try & decrypt it
return this._reallyDecryptMessage(theirDeviceIdentityKey, message);
} else {
this._olmDevice._olmPrekeyPromise = this._olmDevice._olmPrekeyPromise.then(() => {
return this._reallyDecryptMessage(theirDeviceIdentityKey, message);
});
return await this._olmDevice._olmPrekeyPromise;
}
};
OlmDecryption.prototype._reallyDecryptMessage = async function(
theirDeviceIdentityKey, message,
) {
const sessionIds = await this._olmDevice.getSessionIdsForDevice(
theirDeviceIdentityKey,