Olm.cpp

#include "Olm.h"

#include <QObject>
#include <QTimer>

#include <nlohmann/json.hpp>
#include <variant>

#include <mtx/responses/common.hpp>
#include <mtx/secret_storage.hpp>

#include "Cache.h"
#include "Cache_p.h"
#include "ChatPage.h"
#include "DeviceVerificationFlow.h"
#include "Logging.h"
#include "MatrixClient.h"
#include "UserSettingsPage.h"
#include "Utils.h"

namespace {
auto client_ = std::make_unique<mtx::crypto::OlmClient>();

std::map<std::string, std::string> request_id_to_secret_name;

const std::string STORAGE_SECRET_KEY("secret");
constexpr auto MEGOLM_ALGO = "m.megolm.v1.aes-sha2";
}

namespace olm {
void
from_json(const nlohmann::json &obj, OlmMessage &msg)
{
        if (obj.at("type") != "m.room.encrypted")
                throw std::invalid_argument("invalid type for olm message");

        if (obj.at("content").at("algorithm") != OLM_ALGO)
                throw std::invalid_argument("invalid algorithm for olm message");

        msg.sender     = obj.at("sender");
        msg.sender_key = obj.at("content").at("sender_key");
        msg.ciphertext = obj.at("content")
                           .at("ciphertext")
                           .get<std::map<std::string, mtx::events::msg::OlmCipherContent>>();
}

mtx::crypto::OlmClient *
client()
{
        return client_.get();
}

void
handle_to_device_messages(const std::vector<mtx::events::collections::DeviceEvents> &msgs)
{
        if (msgs.empty())
                return;
        nhlog::crypto()->info("received {} to_device messages", msgs.size());
        nlohmann::json j_msg;

        for (const auto &msg : msgs) {
                j_msg = std::visit([](auto &e) { return json(e); }, std::move(msg));
                if (j_msg.count("type") == 0) {
                        nhlog::crypto()->warn("received message with no type field: {}",
                                              j_msg.dump(2));
                        continue;
                }

                std::string msg_type = j_msg.at("type");

                if (msg_type == to_string(mtx::events::EventType::RoomEncrypted)) {
                        try {
                                olm::OlmMessage olm_msg = j_msg;
                                handle_olm_message(std::move(olm_msg));
                        } catch (const nlohmann::json::exception &e) {
                                nhlog::crypto()->warn(
                                  "parsing error for olm message: {} {}", e.what(), j_msg.dump(2));
                        } catch (const std::invalid_argument &e) {
                                nhlog::crypto()->warn("validation error for olm message: {} {}",
                                                      e.what(),
                                                      j_msg.dump(2));
                        }

                } else if (msg_type == to_string(mtx::events::EventType::RoomKeyRequest)) {
                        nhlog::crypto()->warn("handling key request event: {}", j_msg.dump(2));
                        try {
                                mtx::events::DeviceEvent<mtx::events::msg::KeyRequest> req = j_msg;
                                if (req.content.action == mtx::events::msg::RequestAction::Request)
                                        handle_key_request_message(req);
                                else
                                        nhlog::crypto()->warn(
                                          "ignore key request (unhandled action): {}",
                                          req.content.request_id);
                        } catch (const nlohmann::json::exception &e) {
                                nhlog::crypto()->warn(
                                  "parsing error for key_request message: {} {}",
                                  e.what(),
                                  j_msg.dump(2));
                        }
                } else if (msg_type == to_string(mtx::events::EventType::KeyVerificationAccept)) {
                        auto message = std::get<
                          mtx::events::DeviceEvent<mtx::events::msg::KeyVerificationAccept>>(msg);
                        ChatPage::instance()->receivedDeviceVerificationAccept(message.content);
                } else if (msg_type == to_string(mtx::events::EventType::KeyVerificationRequest)) {
                        auto message = std::get<
                          mtx::events::DeviceEvent<mtx::events::msg::KeyVerificationRequest>>(msg);
                        ChatPage::instance()->receivedDeviceVerificationRequest(message.content,
                                                                                message.sender);
                } else if (msg_type == to_string(mtx::events::EventType::KeyVerificationCancel)) {
                        auto message = std::get<
                          mtx::events::DeviceEvent<mtx::events::msg::KeyVerificationCancel>>(msg);
                        ChatPage::instance()->receivedDeviceVerificationCancel(message.content);
                } else if (msg_type == to_string(mtx::events::EventType::KeyVerificationKey)) {
                        auto message =
                          std::get<mtx::events::DeviceEvent<mtx::events::msg::KeyVerificationKey>>(
                            msg);
                        ChatPage::instance()->receivedDeviceVerificationKey(message.content);
                } else if (msg_type == to_string(mtx::events::EventType::KeyVerificationMac)) {
                        auto message =
                          std::get<mtx::events::DeviceEvent<mtx::events::msg::KeyVerificationMac>>(
                            msg);
                        ChatPage::instance()->receivedDeviceVerificationMac(message.content);
                } else if (msg_type == to_string(mtx::events::EventType::KeyVerificationStart)) {
                        auto message = std::get<
                          mtx::events::DeviceEvent<mtx::events::msg::KeyVerificationStart>>(msg);
                        ChatPage::instance()->receivedDeviceVerificationStart(message.content,
                                                                              message.sender);
                } else if (msg_type == to_string(mtx::events::EventType::KeyVerificationReady)) {
                        auto message = std::get<
                          mtx::events::DeviceEvent<mtx::events::msg::KeyVerificationReady>>(msg);
                        ChatPage::instance()->receivedDeviceVerificationReady(message.content);
                } else if (msg_type == to_string(mtx::events::EventType::KeyVerificationDone)) {
                        auto message =
                          std::get<mtx::events::DeviceEvent<mtx::events::msg::KeyVerificationDone>>(
                            msg);
                        ChatPage::instance()->receivedDeviceVerificationDone(message.content);
                } else {
                        nhlog::crypto()->warn("unhandled event: {}", j_msg.dump(2));
                }
        }
}

void
handle_olm_message(const OlmMessage &msg)
{
        nhlog::crypto()->info("sender    : {}", msg.sender);
        nhlog::crypto()->info("sender_key: {}", msg.sender_key);

        const auto my_key = olm::client()->identity_keys().curve25519;

        for (const auto &cipher : msg.ciphertext) {
                // We skip messages not meant for the current device.
                if (cipher.first != my_key)
                        continue;

                const auto type = cipher.second.type;
                nhlog::crypto()->info("type: {}", type == 0 ? "OLM_PRE_KEY" : "OLM_MESSAGE");

                auto payload = try_olm_decryption(msg.sender_key, cipher.second);

                if (payload.is_null()) {
                        // Check for PRE_KEY message
                        if (cipher.second.type == 0) {
                                payload = handle_pre_key_olm_message(
                                  msg.sender, msg.sender_key, cipher.second);
                        } else {
                                nhlog::crypto()->error("Undecryptable olm message!");
                                continue;
                        }
                }

                if (!payload.is_null()) {
                        mtx::events::collections::DeviceEvents device_event;

                        {
                                std::string msg_type = payload["type"];
                                json event_array     = json::array();
                                event_array.push_back(payload);

                                std::vector<mtx::events::collections::DeviceEvents> temp_events;
                                mtx::responses::utils::parse_device_events(event_array,
                                                                           temp_events);
                                if (temp_events.empty()) {
                                        nhlog::crypto()->warn("Decrypted unknown event: {}",
                                                              payload.dump());
                                        continue;
                                }
                                device_event = temp_events.at(0);
                        }

                        using namespace mtx::events;
                        if (auto e =
                              std::get_if<DeviceEvent<msg::KeyVerificationAccept>>(&device_event)) {
                                ChatPage::instance()->receivedDeviceVerificationAccept(e->content);
                        } else if (auto e = std::get_if<DeviceEvent<msg::KeyVerificationRequest>>(
                                     &device_event)) {
                                ChatPage::instance()->receivedDeviceVerificationRequest(e->content,
                                                                                        e->sender);
                        } else if (auto e = std::get_if<DeviceEvent<msg::KeyVerificationCancel>>(
                                     &device_event)) {
                                ChatPage::instance()->receivedDeviceVerificationCancel(e->content);
                        } else if (auto e = std::get_if<DeviceEvent<msg::KeyVerificationKey>>(
                                     &device_event)) {
                                ChatPage::instance()->receivedDeviceVerificationKey(e->content);
                        } else if (auto e = std::get_if<DeviceEvent<msg::KeyVerificationMac>>(
                                     &device_event)) {
                                ChatPage::instance()->receivedDeviceVerificationMac(e->content);
                        } else if (auto e = std::get_if<DeviceEvent<msg::KeyVerificationStart>>(
                                     &device_event)) {
                                ChatPage::instance()->receivedDeviceVerificationStart(e->content,
                                                                                      e->sender);
                        } else if (auto e = std::get_if<DeviceEvent<msg::KeyVerificationReady>>(
                                     &device_event)) {
                                ChatPage::instance()->receivedDeviceVerificationReady(e->content);
                        } else if (auto e = std::get_if<DeviceEvent<msg::KeyVerificationDone>>(
                                     &device_event)) {
                                ChatPage::instance()->receivedDeviceVerificationDone(e->content);
                        } else if (auto roomKey =
                                     std::get_if<DeviceEvent<msg::RoomKey>>(&device_event)) {
                                create_inbound_megolm_session(*roomKey, msg.sender_key);
                        } else if (auto roomKey = std::get_if<DeviceEvent<msg::ForwardedRoomKey>>(
                                     &device_event)) {
                                import_inbound_megolm_session(*roomKey);
                        } else if (auto e =
                                     std::get_if<DeviceEvent<msg::SecretSend>>(&device_event)) {
                                auto local_user = http::client()->user_id();

                                if (msg.sender != local_user.to_string())
                                        continue;

                                auto secret_name =
                                  request_id_to_secret_name.find(e->content.request_id);

                                if (secret_name != request_id_to_secret_name.end()) {
                                        nhlog::crypto()->info("Received secret: {}",
                                                              secret_name->second);

                                        mtx::events::msg::SecretRequest secretRequest{};
                                        secretRequest.action =
                                          mtx::events::msg::RequestAction::Cancellation;
                                        secretRequest.requesting_device_id =
                                          http::client()->device_id();
                                        secretRequest.request_id = e->content.request_id;

                                        auto verificationStatus =
                                          cache::verificationStatus(local_user.to_string());

                                        if (!verificationStatus)
                                                continue;

                                        auto deviceKeys = cache::userKeys(local_user.to_string());
                                        std::string sender_device_id;
                                        if (deviceKeys) {
                                                for (auto &[dev, key] : deviceKeys->device_keys) {
                                                        if (key.keys["curve25519:" + dev] ==
                                                            msg.sender_key) {
                                                                sender_device_id = dev;
                                                                break;
                                                        }
                                                }
                                        }

                                        std::map<
                                          mtx::identifiers::User,
                                          std::map<std::string, mtx::events::msg::SecretRequest>>
                                          body;

                                        for (const auto &dev :
                                             verificationStatus->verified_devices) {
                                                if (dev != secretRequest.requesting_device_id &&
                                                    dev != sender_device_id)
                                                        body[local_user][dev] = secretRequest;
                                        }

                                        http::client()
                                          ->send_to_device<mtx::events::msg::SecretRequest>(
                                            http::client()->generate_txn_id(),
                                            body,
                                            [name =
                                               secret_name->second](mtx::http::RequestErr err) {
                                                    if (err) {
                                                            nhlog::net()->error(
                                                              "Failed to send request cancellation "
                                                              "for secrect "
                                                              "'{}'",
                                                              name);
                                                            return;
                                                    }
                                            });

                                        cache::client()->storeSecret(secret_name->second,
                                                                     e->content.secret);

                                        request_id_to_secret_name.erase(secret_name);
                                }

                        } else if (auto e =
                                     std::get_if<DeviceEvent<msg::SecretRequest>>(&device_event)) {
                                if (e->content.action != mtx::events::msg::RequestAction::Request)
                                        continue;

                                auto local_user = http::client()->user_id();

                                if (msg.sender != local_user.to_string())
                                        continue;

                                auto verificationStatus =
                                  cache::verificationStatus(local_user.to_string());

                                if (!verificationStatus)
                                        continue;

                                auto deviceKeys = cache::userKeys(local_user.to_string());
                                if (!deviceKeys)
                                        continue;

                                for (auto &[dev, key] : deviceKeys->device_keys) {
                                        if (key.keys["curve25519:" + dev] == msg.sender_key) {
                                                if (std::find(
                                                      verificationStatus->verified_devices.begin(),
                                                      verificationStatus->verified_devices.end(),
                                                      dev) ==
                                                    verificationStatus->verified_devices.end())
                                                        break;

                                                // this is a verified device
                                                mtx::events::DeviceEvent<
                                                  mtx::events::msg::SecretSend>
                                                  secretSend;
                                                secretSend.type = EventType::SecretSend;
                                                secretSend.content.request_id =
                                                  e->content.request_id;

                                                auto secret =
                                                  cache::client()->secret(e->content.name);
                                                if (!secret)
                                                        break;

                                                secretSend.content.secret = secret.value();

                                                send_encrypted_to_device_messages(
                                                  {{local_user.to_string(), {{dev}}}}, secretSend);

                                                nhlog::net()->info("Sent secret to ({},{})",
                                                                   local_user.to_string(),
                                                                   dev);

                                                break;
                                        }
                                }
                        }

                        return;
                }
        }
}

nlohmann::json
handle_pre_key_olm_message(const std::string &sender,
                           const std::string &sender_key,
                           const mtx::events::msg::OlmCipherContent &content)
{
        nhlog::crypto()->info("opening olm session with {}", sender);

        mtx::crypto::OlmSessionPtr inbound_session = nullptr;
        try {
                inbound_session =
                  olm::client()->create_inbound_session_from(sender_key, content.body);

                // We also remove the one time key used to establish that
                // session so we'll have to update our copy of the account object.
                cache::saveOlmAccount(olm::client()->save("secret"));
        } catch (const mtx::crypto::olm_exception &e) {
                nhlog::crypto()->critical(
                  "failed to create inbound session with {}: {}", sender, e.what());
                return {};
        }

        if (!mtx::crypto::matches_inbound_session_from(
              inbound_session.get(), sender_key, content.body)) {
                nhlog::crypto()->warn("inbound olm session doesn't match sender's key ({})",
                                      sender);
                return {};
        }

        mtx::crypto::BinaryBuf output;
        try {
                output =
                  olm::client()->decrypt_message(inbound_session.get(), content.type, content.body);
        } catch (const mtx::crypto::olm_exception &e) {
                nhlog::crypto()->critical(
                  "failed to decrypt olm message {}: {}", content.body, e.what());
                return {};
        }

        auto plaintext = json::parse(std::string((char *)output.data(), output.size()));
        nhlog::crypto()->debug("decrypted message: \n {}", plaintext.dump(2));

        try {
                nhlog::crypto()->debug("New olm session: {}",
                                       mtx::crypto::session_id(inbound_session.get()));
                cache::saveOlmSession(
                  sender_key, std::move(inbound_session), QDateTime::currentMSecsSinceEpoch());
        } catch (const lmdb::error &e) {
                nhlog::db()->warn(
                  "failed to save inbound olm session from {}: {}", sender, e.what());
        }

        return plaintext;
}

mtx::events::msg::Encrypted
encrypt_group_message(const std::string &room_id, const std::string &device_id, nlohmann::json body)
{
        using namespace mtx::events;
        using namespace mtx::identifiers;

        auto own_user_id = http::client()->user_id().to_string();

        auto members = cache::client()->getMembersWithKeys(room_id);

        std::map<std::string, std::vector<std::string>> sendSessionTo;
        mtx::crypto::OutboundGroupSessionPtr session = nullptr;
        OutboundGroupSessionData group_session_data;

        if (cache::outboundMegolmSessionExists(room_id)) {
                auto res = cache::getOutboundMegolmSession(room_id);

                auto member_it             = members.begin();
                auto session_member_it     = res.data.currently.keys.begin();
                auto session_member_it_end = res.data.currently.keys.end();

                while (member_it != members.end() || session_member_it != session_member_it_end) {
                        if (member_it == members.end()) {
                                // a member left, purge session!
                                nhlog::crypto()->debug(
                                  "Rotating megolm session because of left member");
                                break;
                        }

                        if (session_member_it == session_member_it_end) {
                                // share with all remaining members
                                while (member_it != members.end()) {
                                        sendSessionTo[member_it->first] = {};

                                        if (member_it->second)
                                                for (const auto &dev :
                                                     member_it->second->device_keys)
                                                        if (member_it->first != own_user_id ||
                                                            dev.first != device_id)
                                                                sendSessionTo[member_it->first]
                                                                  .push_back(dev.first);

                                        ++member_it;
                                }

                                session = std::move(res.session);
                                break;
                        }

                        if (member_it->first > session_member_it->first) {
                                // a member left, purge session
                                nhlog::crypto()->debug(
                                  "Rotating megolm session because of left member");
                                break;
                        } else if (member_it->first < session_member_it->first) {
                                // new member, send them the session at this index
                                sendSessionTo[member_it->first] = {};

                                if (member_it->second) {
                                        for (const auto &dev : member_it->second->device_keys)
                                                if (member_it->first != own_user_id ||
                                                    dev.first != device_id)
                                                        sendSessionTo[member_it->first].push_back(
                                                          dev.first);
                                }

                                ++member_it;
                        } else {
                                // compare devices
                                bool device_removed = false;
                                for (const auto &dev : session_member_it->second.devices) {
                                        if (!member_it->second ||
                                            !member_it->second->device_keys.count(dev.first)) {
                                                device_removed = true;
                                                break;
                                        }
                                }

                                if (device_removed) {
                                        // device removed, rotate session!
                                        nhlog::crypto()->debug(
                                          "Rotating megolm session because of removed device of {}",
                                          member_it->first);
                                        break;
                                }

                                // check for new devices to share with
                                if (member_it->second)
                                        for (const auto &dev : member_it->second->device_keys)
                                                if (!session_member_it->second.devices.count(
                                                      dev.first) &&
                                                    (member_it->first != own_user_id ||
                                                     dev.first != device_id))
                                                        sendSessionTo[member_it->first].push_back(
                                                          dev.first);

                                ++member_it;
                                ++session_member_it;
                                if (member_it == members.end() &&
                                    session_member_it == session_member_it_end) {
                                        // all devices match or are newly added
                                        session = std::move(res.session);
                                }
                        }
                }

                group_session_data = std::move(res.data);
        }

        if (!session) {
                nhlog::ui()->debug("creating new outbound megolm session");

                // Create a new outbound megolm session.
                session                = olm::client()->init_outbound_group_session();
                const auto session_id  = mtx::crypto::session_id(session.get());
                const auto session_key = mtx::crypto::session_key(session.get());

                // Saving the new megolm session.
                OutboundGroupSessionData session_data{};
                session_data.session_id    = mtx::crypto::session_id(session.get());
                session_data.session_key   = mtx::crypto::session_key(session.get());
                session_data.message_index = 0;

                sendSessionTo.clear();

                for (const auto &[user, devices] : members) {
                        sendSessionTo[user]               = {};
                        session_data.initially.keys[user] = {};
                        if (devices) {
                                for (const auto &[device_id_, key] : devices->device_keys) {
                                        (void)key;
                                        if (device_id != device_id_ || user != own_user_id) {
                                                sendSessionTo[user].push_back(device_id_);
                                                session_data.initially.keys[user]
                                                  .devices[device_id_] = 0;
                                        }
                                }
                        }
                }

                cache::saveOutboundMegolmSession(room_id, session_data, session);
                group_session_data = std::move(session_data);

                {
                        MegolmSessionIndex index;
                        index.room_id    = room_id;
                        index.session_id = session_id;
                        index.sender_key = olm::client()->identity_keys().curve25519;
                        auto megolm_session =
                          olm::client()->init_inbound_group_session(session_key);
                        cache::saveInboundMegolmSession(index, std::move(megolm_session));
                }
        }

        mtx::events::DeviceEvent<mtx::events::msg::RoomKey> megolm_payload{};
        megolm_payload.content.algorithm   = MEGOLM_ALGO;
        megolm_payload.content.room_id     = room_id;
        megolm_payload.content.session_id  = mtx::crypto::session_id(session.get());
        megolm_payload.content.session_key = mtx::crypto::session_key(session.get());
        megolm_payload.type                = mtx::events::EventType::RoomKey;

        if (!sendSessionTo.empty())
                olm::send_encrypted_to_device_messages(sendSessionTo, megolm_payload);

        mtx::common::ReplyRelatesTo relation;
        mtx::common::RelatesTo r_relation;

        // relations shouldn't be encrypted...
        if (body["content"].contains("m.relates_to") &&
            body["content"]["m.relates_to"].contains("m.in_reply_to")) {
                relation = body["content"]["m.relates_to"];
                body["content"].erase("m.relates_to");
        } else if (body["content"]["m.relates_to"].contains("event_id")) {
                r_relation = body["content"]["m.relates_to"];
                body["content"].erase("m.relates_to");
        }

        auto payload = olm::client()->encrypt_group_message(session.get(), body.dump());

        // Prepare the m.room.encrypted event.
        msg::Encrypted data;
        data.ciphertext   = std::string((char *)payload.data(), payload.size());
        data.sender_key   = olm::client()->identity_keys().curve25519;
        data.session_id   = mtx::crypto::session_id(session.get());
        data.device_id    = device_id;
        data.algorithm    = MEGOLM_ALGO;
        data.relates_to   = relation;
        data.r_relates_to = r_relation;

        group_session_data.message_index = olm_outbound_group_session_message_index(session.get());
        nhlog::crypto()->debug("next message_index {}", group_session_data.message_index);

        // update current set of members for the session with the new members and that message_index
        for (const auto &[user, devices] : sendSessionTo) {
                if (!group_session_data.currently.keys.count(user))
                        group_session_data.currently.keys[user] = {};

                for (const auto &device_id_ : devices) {
                        if (!group_session_data.currently.keys[user].devices.count(device_id_))
                                group_session_data.currently.keys[user].devices[device_id_] =
                                  group_session_data.message_index;
                }
        }

        // We need to re-pickle the session after we send a message to save the new message_index.
        cache::updateOutboundMegolmSession(room_id, group_session_data, session);

        return data;
}

nlohmann::json
try_olm_decryption(const std::string &sender_key, const mtx::events::msg::OlmCipherContent &msg)
{
        auto session_ids = cache::getOlmSessions(sender_key);

        nhlog::crypto()->info("attempt to decrypt message with {} known session_ids",
                              session_ids.size());

        for (const auto &id : session_ids) {
                auto session = cache::getOlmSession(sender_key, id);

                if (!session)
                        continue;

                mtx::crypto::BinaryBuf text;

                try {
                        text = olm::client()->decrypt_message(session->get(), msg.type, msg.body);
                        nhlog::crypto()->debug("Updated olm session: {}",
                                               mtx::crypto::session_id(session->get()));
                        cache::saveOlmSession(
                          id, std::move(session.value()), QDateTime::currentMSecsSinceEpoch());
                } catch (const mtx::crypto::olm_exception &e) {
                        nhlog::crypto()->debug("failed to decrypt olm message ({}, {}) with {}: {}",
                                               msg.type,
                                               sender_key,
                                               id,
                                               e.what());
                        continue;
                } catch (const lmdb::error &e) {
                        nhlog::crypto()->critical("failed to save session: {}", e.what());
                        return {};
                }

                try {
                        return json::parse(std::string_view((char *)text.data(), text.size()));
                } catch (const json::exception &e) {
                        nhlog::crypto()->critical(
                          "failed to parse the decrypted session msg: {} {}",
                          e.what(),
                          std::string_view((char *)text.data(), text.size()));
                }
        }

        return {};
}

void
create_inbound_megolm_session(const mtx::events::DeviceEvent<mtx::events::msg::RoomKey> &roomKey,
                              const std::string &sender_key)
{
        MegolmSessionIndex index;
        index.room_id    = roomKey.content.room_id;
        index.session_id = roomKey.content.session_id;
        index.sender_key = sender_key;

        try {
                auto megolm_session =
                  olm::client()->init_inbound_group_session(roomKey.content.session_key);
                cache::saveInboundMegolmSession(index, std::move(megolm_session));
        } catch (const lmdb::error &e) {
                nhlog::crypto()->critical("failed to save inbound megolm session: {}", e.what());
                return;
        } catch (const mtx::crypto::olm_exception &e) {
                nhlog::crypto()->critical("failed to create inbound megolm session: {}", e.what());
                return;
        }

        nhlog::crypto()->info(
          "established inbound megolm session ({}, {})", roomKey.content.room_id, roomKey.sender);

        ChatPage::instance()->receivedSessionKey(index.room_id, index.session_id);
}

void
import_inbound_megolm_session(
  const mtx::events::DeviceEvent<mtx::events::msg::ForwardedRoomKey> &roomKey)
{
        MegolmSessionIndex index;
        index.room_id    = roomKey.content.room_id;
        index.session_id = roomKey.content.session_id;
        index.sender_key = roomKey.content.sender_key;

        try {
                auto megolm_session =
                  olm::client()->import_inbound_group_session(roomKey.content.session_key);
                cache::saveInboundMegolmSession(index, std::move(megolm_session));
        } catch (const lmdb::error &e) {
                nhlog::crypto()->critical("failed to save inbound megolm session: {}", e.what());
                return;
        } catch (const mtx::crypto::olm_exception &e) {
                nhlog::crypto()->critical("failed to import inbound megolm session: {}", e.what());
                return;
        }

        nhlog::crypto()->info(
          "established inbound megolm session ({}, {})", roomKey.content.room_id, roomKey.sender);

        ChatPage::instance()->receivedSessionKey(index.room_id, index.session_id);
}

void
mark_keys_as_published()
{
        olm::client()->mark_keys_as_published();
        cache::saveOlmAccount(olm::client()->save(STORAGE_SECRET_KEY));
}

void
send_key_request_for(mtx::events::EncryptedEvent<mtx::events::msg::Encrypted> e,
                     const std::string &request_id,
                     bool cancel)
{
        using namespace mtx::events;

        nhlog::crypto()->debug("sending key request: sender_key {}, session_id {}",
                               e.content.sender_key,
                               e.content.session_id);

        mtx::events::msg::KeyRequest request;
        request.action = cancel ? mtx::events::msg::RequestAction::Cancellation
                                : mtx::events::msg::RequestAction::Request;

        request.algorithm            = MEGOLM_ALGO;
        request.room_id              = e.room_id;
        request.sender_key           = e.content.sender_key;
        request.session_id           = e.content.session_id;
        request.request_id           = request_id;
        request.requesting_device_id = http::client()->device_id();

        nhlog::crypto()->debug("m.room_key_request: {}", json(request).dump(2));

        std::map<mtx::identifiers::User, std::map<std::string, decltype(request)>> body;
        body[mtx::identifiers::parse<mtx::identifiers::User>(e.sender)][e.content.device_id] =
          request;
        body[http::client()->user_id()]["*"] = request;

        http::client()->send_to_device(
          http::client()->generate_txn_id(), body, [e](mtx::http::RequestErr err) {
                  if (err) {
                          nhlog::net()->warn("failed to send "
                                             "send_to_device "
                                             "message: {}",
                                             err->matrix_error.error);
                  }

                  nhlog::net()->info("m.room_key_request sent to {}:{} and your own devices",
                                     e.sender,
                                     e.content.device_id);
          });
}

void
handle_key_request_message(const mtx::events::DeviceEvent<mtx::events::msg::KeyRequest> &req)
{
        if (req.content.algorithm != MEGOLM_ALGO) {
                nhlog::crypto()->debug("ignoring key request {} with invalid algorithm: {}",
                                       req.content.request_id,
                                       req.content.algorithm);
                return;
        }

        // Check if we were the sender of the session being requested.
        if (req.content.sender_key != olm::client()->identity_keys().curve25519) {
                nhlog::crypto()->debug("ignoring key request {} because we were not the sender: "
                                       "\nrequested({}) ours({})",
                                       req.content.request_id,
                                       req.content.sender_key,
                                       olm::client()->identity_keys().curve25519);
                return;
        }

        // Check if we have the keys for the requested session.
        if (!cache::outboundMegolmSessionExists(req.content.room_id)) {
                nhlog::crypto()->warn("requested session not found in room: {}",
                                      req.content.room_id);

                return;
        }

        // Check that the requested session_id and the one we have saved match.
        MegolmSessionIndex index{};
        index.room_id    = req.content.room_id;
        index.session_id = req.content.session_id;
        index.sender_key = olm::client()->identity_keys().curve25519;

        const auto session = cache::getInboundMegolmSession(index);
        if (!session) {
                nhlog::crypto()->warn("No session with id {} in db", req.content.session_id);
                return;
        }

        if (!cache::isRoomMember(req.sender, req.content.room_id)) {
                nhlog::crypto()->warn(
                  "user {} that requested the session key is not member of the room {}",
                  req.sender,
                  req.content.room_id);
                return;
        }

        // check if device is verified
        auto verificationStatus = cache::verificationStatus(req.sender);
        bool verifiedDevice     = false;
        if (verificationStatus &&
            ChatPage::instance()->userSettings()->shareKeysWithTrustedUsers()) {
                for (const auto &dev : verificationStatus->verified_devices) {
                        if (dev == req.content.requesting_device_id) {
                                verifiedDevice = true;
                                nhlog::crypto()->debug("Verified device: {}", dev);
                                break;
                        }
                }
        }

        if (!utils::respondsToKeyRequests(req.content.room_id) && !verifiedDevice) {
                nhlog::crypto()->debug("ignoring all key requests for room {}",
                                       req.content.room_id);
                return;
        }

        auto session_key = mtx::crypto::export_session(session.get());
        //
        // Prepare the m.room_key event.
        //
        mtx::events::msg::ForwardedRoomKey forward_key{};
        forward_key.algorithm   = MEGOLM_ALGO;
        forward_key.room_id     = index.room_id;
        forward_key.session_id  = index.session_id;
        forward_key.session_key = session_key;
        forward_key.sender_key  = index.sender_key;

        // TODO(Nico): Figure out if this is correct
        forward_key.sender_claimed_ed25519_key      = olm::client()->identity_keys().ed25519;
        forward_key.forwarding_curve25519_key_chain = {};

        send_megolm_key_to_device(req.sender, req.content.requesting_device_id, forward_key);
}

void
send_megolm_key_to_device(const std::string &user_id,
                          const std::string &device_id,
                          const mtx::events::msg::ForwardedRoomKey &payload)
{
        mtx::events::DeviceEvent<mtx::events::msg::ForwardedRoomKey> room_key;
        room_key.content = payload;
        room_key.type    = mtx::events::EventType::ForwardedRoomKey;

        std::map<std::string, std::vector<std::string>> targets;
        targets[user_id] = {device_id};
        send_encrypted_to_device_messages(targets, room_key);
}

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.get(), 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)};
}

//! Send encrypted to device messages, targets is a map from userid to device ids or {} for all
//! devices
void
send_encrypted_to_device_messages(const std::map<std::string, std::vector<std::string>> targets,
                                  const mtx::events::collections::DeviceEvents &event,
                                  bool force_new_session)
{
        nlohmann::json ev_json = std::visit([](const auto &e) { return json(e); }, event);

        std::map<std::string, std::vector<std::string>> keysToQuery;
        mtx::requests::ClaimKeys claims;
        std::map<mtx::identifiers::User, std::map<std::string, mtx::events::msg::OlmEncrypted>>
          messages;
        std::map<std::string, std::map<std::string, DevicePublicKeys>> pks;

        for (const auto &[user, devices] : targets) {
                auto deviceKeys = cache::client()->userKeys(user);

                // no keys for user, query them
                if (!deviceKeys) {
                        keysToQuery[user] = devices;
                        continue;
                }

                auto deviceTargets = devices;
                if (devices.empty()) {
                        deviceTargets.clear();
                        for (const auto &[device, keys] : deviceKeys->device_keys) {
                                (void)keys;
                                deviceTargets.push_back(device);
                        }
                }

                for (const auto &device : deviceTargets) {
                        if (!deviceKeys->device_keys.count(device)) {
                                keysToQuery[user] = {};
                                break;
                        }

                        auto d = deviceKeys->device_keys.at(device);

                        auto session =
                          cache::getLatestOlmSession(d.keys.at("curve25519:" + device));
                        if (!session || force_new_session) {
                                claims.one_time_keys[user][device] = mtx::crypto::SIGNED_CURVE25519;
                                pks[user][device].ed25519          = d.keys.at("ed25519:" + device);
                                pks[user][device].curve25519 = d.keys.at("curve25519:" + device);
                                continue;
                        }

                        messages[mtx::identifiers::parse<mtx::identifiers::User>(user)][device] =
                          olm::client()
                            ->create_olm_encrypted_content(session->get(),
                                                           ev_json,
                                                           UserId(user),
                                                           d.keys.at("ed25519:" + device),
                                                           d.keys.at("curve25519:" + device))
                            .get<mtx::events::msg::OlmEncrypted>();

                        try {
                                nhlog::crypto()->debug("Updated olm session: {}",
                                                       mtx::crypto::session_id(session->get()));
                                cache::saveOlmSession(d.keys.at("curve25519:" + device),
                                                      std::move(*session),
                                                      QDateTime::currentMSecsSinceEpoch());
                        } catch (const lmdb::error &e) {
                                nhlog::db()->critical("failed to save outbound olm session: {}",
                                                      e.what());
                        } catch (const mtx::crypto::olm_exception &e) {
                                nhlog::crypto()->critical(
                                  "failed to pickle outbound olm session: {}", e.what());
                        }
                }
        }

        if (!messages.empty())
                http::client()->send_to_device<mtx::events::msg::OlmEncrypted>(
                  http::client()->generate_txn_id(), messages, [](mtx::http::RequestErr err) {
                          if (err) {