diff --git a/src/Olm.cpp b/src/Olm.cpp
index 994a3a67..466fe940 100644
--- a/src/Olm.cpp
+++ b/src/Olm.cpp
@@ -3,6 +3,7 @@
#include "Olm.h"
#include "Cache.h"
+#include "Cache_p.h"
#include "Logging.h"
#include "MatrixClient.h"
#include "Utils.h"
@@ -551,4 +552,50 @@ send_megolm_key_to_device(const std::string &user_id,
});
}
+DecryptionResult
+decryptEvent(const MegolmSessionIndex &index,
+ const mtx::events::EncryptedEvent<mtx::events::msg::Encrypted> &event)
+{
+ try {
+ if (!cache::client()->inboundMegolmSessionExists(index)) {
+ return {DecryptionErrorCode::MissingSession, std::nullopt, std::nullopt};
+ }
+ } catch (const lmdb::error &e) {
+ return {DecryptionErrorCode::DbError, e.what(), std::nullopt};
+ }
+
+ // TODO: Lookup index,event_id,origin_server_ts tuple for replay attack errors
+ // TODO: Verify sender_key
+
+ std::string msg_str;
+ try {
+ auto session = cache::client()->getInboundMegolmSession(index);
+ auto res = olm::client()->decrypt_group_message(session, event.content.ciphertext);
+ msg_str = std::string((char *)res.data.data(), res.data.size());
+ } catch (const lmdb::error &e) {
+ return {DecryptionErrorCode::DbError, e.what(), std::nullopt};
+ } catch (const mtx::crypto::olm_exception &e) {
+ return {DecryptionErrorCode::DecryptionFailed, e.what(), std::nullopt};
+ }
+
+ // Add missing fields for the event.
+ json body = json::parse(msg_str);
+ body["event_id"] = event.event_id;
+ body["sender"] = event.sender;
+ body["origin_server_ts"] = event.origin_server_ts;
+ body["unsigned"] = event.unsigned_data;
+
+ // relations are unencrypted in content...
+ if (json old_ev = event; old_ev["content"].count("m.relates_to") != 0)
+ body["content"]["m.relates_to"] = old_ev["content"]["m.relates_to"];
+
+ mtx::events::collections::TimelineEvent te;
+ try {
+ mtx::events::collections::from_json(body, te);
+ } catch (std::exception &e) {
+ return {DecryptionErrorCode::ParsingFailed, e.what(), std::nullopt};
+ }
+
+ return {std::nullopt, std::nullopt, std::move(te.data)};
+}
} // namespace olm
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