Olm.cpp

// SPDX-FileCopyrightText: 2021 Nheko Contributors
//
// SPDX-License-Identifier: GPL-3.0-or-later

#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;

constexpr auto MEGOLM_ALGO = "m.megolm.v1.aes-sha2";
}

namespace olm {
static void
backup_session_key(const MegolmSessionIndex &idx,
                   const GroupSessionData &data,
                   mtx::crypto::InboundGroupSessionPtr &session);

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();
}

static void
handle_secret_request(const mtx::events::DeviceEvent<mtx::events::msg::SecretRequest> *e,
                      const std::string &sender)
{
    using namespace mtx::events;

    if (e->content.action != mtx::events::msg::RequestAction::Request)
        return;

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

    if (sender != local_user.to_string())
        return;

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

    if (!verificationStatus)
        return;

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

    if (std::find(verificationStatus->verified_devices.begin(),
                  verificationStatus->verified_devices.end(),
                  e->content.requesting_device_id) == verificationStatus->verified_devices.end())
        return;

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

    send_encrypted_to_device_messages(
      {{local_user.to_string(), {{e->content.requesting_device_id}}}}, secretSend);

    nhlog::net()->info("Sent secret '{}' to ({},{})",
                       e->content.name,
                       local_user.to_string(),
                       e->content.requesting_device_id);
}

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;
                cache::client()->query_keys(
                  olm_msg.sender, [olm_msg](const UserKeyCache &userKeys, mtx::http::RequestErr e) {
                      if (e) {
                          nhlog::crypto()->error("Failed to query user keys, dropping olm "
                                                 "message");
                          return;
                      }
                      handle_olm_message(std::move(olm_msg), userKeys);
                  });
            } 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 if (auto e =
                     std::get_if<mtx::events::DeviceEvent<mtx::events::msg::SecretRequest>>(&msg)) {
            handle_secret_request(e, e->sender);
        } else {
            nhlog::crypto()->warn("unhandled event: {}", j_msg.dump(2));
        }
    }
}

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

    if (msg.sender_key == olm::client()->identity_keys().ed25519) {
        nhlog::crypto()->warn("Ignoring olm message from ourselves!");
        return;
    }

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

    bool failed_decryption = false;

    for (const auto &cipher : msg.ciphertext) {
        // We skip messages not meant for the current device.
        if (cipher.first != my_key) {
            nhlog::crypto()->debug(
              "Skipping message for {} since we are {}.", 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!");
                failed_decryption = true;
                continue;
            }
        }

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

            // Other properties are included in order to prevent an attacker from
            // publishing someone else's curve25519 keys as their own and subsequently
            // claiming to have sent messages which they didn't. sender must correspond
            // to the user who sent the event, recipient to the local user, and
            // recipient_keys to the local ed25519 key.
            std::string receiver_ed25519 = payload["recipient_keys"]["ed25519"];
            if (receiver_ed25519.empty() ||
                receiver_ed25519 != olm::client()->identity_keys().ed25519) {
                nhlog::crypto()->warn("Decrypted event doesn't include our ed25519: {}",
                                      payload.dump());
                return;
            }
            std::string receiver = payload["recipient"];
            if (receiver.empty() || receiver != http::client()->user_id().to_string()) {
                nhlog::crypto()->warn("Decrypted event doesn't include our user_id: {}",
                                      payload.dump());
                return;
            }

            // Clients must confirm that the sender_key and the ed25519 field value
            // under the keys property match the keys returned by /keys/query for the
            // given user, and must also verify the signature of the payload. Without
            // this check, a client cannot be sure that the sender device owns the
            // private part of the ed25519 key it claims to have in the Olm payload.
            // This is crucial when the ed25519 key corresponds to a verified device.
            std::string sender_ed25519 = payload["keys"]["ed25519"];
            if (sender_ed25519.empty()) {
                nhlog::crypto()->warn("Decrypted event doesn't include sender ed25519: {}",
                                      payload.dump());
                return;
            }

            bool from_their_device = false;
            for (auto [device_id, key] : otherUserDeviceKeys.device_keys) {
                auto c_key = key.keys.find("curve25519:" + device_id);
                auto e_key = key.keys.find("ed25519:" + device_id);

                if (c_key == key.keys.end() || e_key == key.keys.end()) {
                    nhlog::crypto()->warn("Skipping device {} as we have no keys for it.",
                                          device_id);
                } else if (c_key->second == msg.sender_key && e_key->second == sender_ed25519) {
                    from_their_device = true;
                    break;
                }
            }
            if (!from_their_device) {
                nhlog::crypto()->warn("Decrypted event isn't sent from a device "
                                      "listed by that user! {}",
                                      payload.dump());
                return;
            }

            {
                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());
                    return;
                }
                device_event = temp_events.at(0);
            }

            using namespace mtx::events;
            if (auto e1 = std::get_if<DeviceEvent<msg::KeyVerificationAccept>>(&device_event)) {
                ChatPage::instance()->receivedDeviceVerificationAccept(e1->content);
            } else if (auto e2 =
                         std::get_if<DeviceEvent<msg::KeyVerificationRequest>>(&device_event)) {
                ChatPage::instance()->receivedDeviceVerificationRequest(e2->content, e2->sender);
            } else if (auto e3 =
                         std::get_if<DeviceEvent<msg::KeyVerificationCancel>>(&device_event)) {
                ChatPage::instance()->receivedDeviceVerificationCancel(e3->content);
            } else if (auto e4 = std::get_if<DeviceEvent<msg::KeyVerificationKey>>(&device_event)) {
                ChatPage::instance()->receivedDeviceVerificationKey(e4->content);
            } else if (auto e5 = std::get_if<DeviceEvent<msg::KeyVerificationMac>>(&device_event)) {
                ChatPage::instance()->receivedDeviceVerificationMac(e5->content);
            } else if (auto e6 =
                         std::get_if<DeviceEvent<msg::KeyVerificationStart>>(&device_event)) {
                ChatPage::instance()->receivedDeviceVerificationStart(e6->content, e6->sender);
            } else if (auto e7 =
                         std::get_if<DeviceEvent<msg::KeyVerificationReady>>(&device_event)) {
                ChatPage::instance()->receivedDeviceVerificationReady(e7->content);
            } else if (auto e8 =
                         std::get_if<DeviceEvent<msg::KeyVerificationDone>>(&device_event)) {
                ChatPage::instance()->receivedDeviceVerificationDone(e8->content);
            } else if (auto roomKey = std::get_if<DeviceEvent<msg::RoomKey>>(&device_event)) {
                create_inbound_megolm_session(*roomKey, msg.sender_key, sender_ed25519);
            } else if (auto forwardedRoomKey =
                         std::get_if<DeviceEvent<msg::ForwardedRoomKey>>(&device_event)) {
                forwardedRoomKey->content.forwarding_curve25519_key_chain.push_back(msg.sender_key);
                import_inbound_megolm_session(*forwardedRoomKey);
            } 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())
                    return;

                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)
                        return;

                    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);
                          }
                      });

                    nhlog::crypto()->info("Storing secret {}", secret_name->second);
                    cache::client()->storeSecret(secret_name->second, e->content.secret);

                    request_id_to_secret_name.erase(secret_name);
                }

            } else if (auto sec_req = std::get_if<DeviceEvent<msg::SecretRequest>>(&device_event)) {
                handle_secret_request(sec_req, msg.sender);
            }

            return;
        } else {
            failed_decryption = true;
        }
    }

    if (failed_decryption) {
        try {
            std::map<std::string, std::vector<std::string>> targets;
            for (auto [device_id, key] : otherUserDeviceKeys.device_keys) {
                if (key.keys.at("curve25519:" + device_id) == msg.sender_key)
                    targets[msg.sender].push_back(device_id);
            }

            send_encrypted_to_device_messages(
              targets, mtx::events::DeviceEvent<mtx::events::msg::Dummy>{}, true);
            nhlog::crypto()->info(
              "Recovering from broken olm channel with {}:{}", msg.sender, msg.sender_key);
        } catch (std::exception &e) {
            nhlog::crypto()->error("Failed to recover from broken olm sessions: {}", e.what());
        }
    }
}

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(cache::client()->pickleSecret()));
    } 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, UserSettings::instance()->onlyShareKeysWithVerifiedUsers());

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

    if (cache::outboundMegolmSessionExists(room_id)) {
        auto res                = cache::getOutboundMegolmSession(room_id);
        auto encryptionSettings = cache::client()->roomEncryptionSettings(room_id);
        mtx::events::state::Encryption defaultSettings;

        // rotate if we crossed the limits for this key
        if (res.data.message_index <
              encryptionSettings.value_or(defaultSettings).rotation_period_msgs &&
            (QDateTime::currentMSecsSinceEpoch() - res.data.timestamp) <
              encryptionSettings.value_or(defaultSettings).rotation_period_ms) {
            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.deviceids) {
                        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.deviceids.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.
        GroupSessionData session_data{};
        session_data.message_index              = 0;
        session_data.timestamp                  = QDateTime::currentMSecsSinceEpoch();
        session_data.sender_claimed_ed25519_key = olm::client()->identity_keys().ed25519;

        sendSessionTo.clear();

        for (const auto &[user, devices] : members) {
            sendSessionTo[user]               = {};
            session_data.currently.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.currently.keys[user].deviceids[device_id_] = 0;
                    }
                }
            }
        }

        {
            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);
            backup_session_key(index, session_data, megolm_session);
            cache::saveInboundMegolmSession(index, std::move(megolm_session), session_data);
        }

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

    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);

    // relations shouldn't be encrypted...
    mtx::common::Relations relations = mtx::common::parse_relations(body["content"]);

    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.relations  = relations;

    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].deviceids.count(device_id_))
                group_session_data.currently.keys[user].deviceids[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) {
            nhlog::crypto()->warn("Unknown olm session: {}:{}", sender_key, id);
            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,
                              const std::string &sender_ed25519)
{
    MegolmSessionIndex index;
    index.room_id    = roomKey.content.room_id;
    index.session_id = roomKey.content.session_id;
    index.sender_key = sender_key;

    try {
        GroupSessionData data{};
        data.forwarding_curve25519_key_chain = {sender_key};
        data.sender_claimed_ed25519_key      = sender_ed25519;

        auto megolm_session =
          olm::client()->init_inbound_group_session(roomKey.content.session_key);
        backup_session_key(index, data, megolm_session);
        cache::saveInboundMegolmSession(index, std::move(megolm_session), data);
    } 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);

        GroupSessionData data{};
        data.forwarding_curve25519_key_chain = roomKey.content.forwarding_curve25519_key_chain;
        data.sender_claimed_ed25519_key      = roomKey.content.sender_claimed_ed25519_key;
        // may have come from online key backup, so we can't trust it...
        data.trusted = false;
        // if we got it forwarded from the sender, assume it is trusted. They may still have
        // used key backup, but it is unlikely.
        if (roomKey.content.forwarding_curve25519_key_chain.size() == 1 &&
            roomKey.content.forwarding_curve25519_key_chain.back() == roomKey.content.sender_key) {
            data.trusted = true;
        }

        backup_session_key(index, data, megolm_session);
        cache::saveInboundMegolmSession(index, std::move(megolm_session), data);
    } 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
backup_session_key(const MegolmSessionIndex &idx,
                   const GroupSessionData &data,
                   mtx::crypto::InboundGroupSessionPtr &session)
{
    try {
        if (!UserSettings::instance()->useOnlineKeyBackup()) {
            // Online key backup disabled
            return;
        }

        auto backupVersion = cache::client()->backupVersion();
        if (!backupVersion) {
            // no trusted OKB
            return;
        }

        using namespace mtx::crypto;

        auto decryptedSecret = cache::secret(mtx::secret_storage::secrets::megolm_backup_v1);
        if (!decryptedSecret) {
            // no backup key available
            return;
        }
        auto sessionDecryptionKey = to_binary_buf(base642bin(*decryptedSecret));

        auto public_key = mtx::crypto::CURVE25519_public_key_from_private(sessionDecryptionKey);

        mtx::responses::backup::SessionData sessionData;
        sessionData.algorithm                       = mtx::crypto::MEGOLM_ALGO;
        sessionData.forwarding_curve25519_key_chain = data.forwarding_curve25519_key_chain;
        sessionData.sender_claimed_keys["ed25519"]  = data.sender_claimed_ed25519_key;
        sessionData.sender_key                      = idx.sender_key;
        sessionData.session_key = mtx::crypto::export_session(session.get(), -1);

        auto encrypt_session = mtx::crypto::encrypt_session(sessionData, public_key);

        mtx::responses::backup::SessionBackup bk;
        bk.first_message_index = olm_inbound_group_session_first_known_index(session.get());
        bk.forwarded_count     = data.forwarding_curve25519_key_chain.size();
        bk.is_verified         = false;
        bk.session_data        = std::move(encrypt_session);

        http::client()->put_room_keys(
          backupVersion->version,
          idx.room_id,
          idx.session_id,
          bk,
          [idx](mtx::http::RequestErr err) {
              if (err) {
                  nhlog::net()->warn("failed to backup session key ({}:{}): {} ({})",
                                     idx.room_id,
                                     idx.session_id,
                                     err->matrix_error.error,
                                     static_cast<int>(err->status_code));
              } else {
                  nhlog::crypto()->debug(
                    "backed up session key ({}:{})", idx.room_id, idx.session_id);
              }
          });
    } catch (std::exception &e) {
        nhlog::net()->warn("failed to backup session key: {}", e.what());
    }
}

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

void
lookup_keybackup(const std::string room, const std::string session_id)
{
    if (!UserSettings::instance()->useOnlineKeyBackup()) {
        // Online key backup disabled
        return;
    }

    auto backupVersion = cache::client()->backupVersion();
    if (!backupVersion) {
        // no trusted OKB
        return;
    }

    using namespace mtx::crypto;

    auto decryptedSecret = cache::secret(mtx::secret_storage::secrets::megolm_backup_v1);
    if (!decryptedSecret) {
        // no backup key available
        return;
    }
    auto sessionDecryptionKey = to_binary_buf(base642bin(*decryptedSecret));

    http::client()->room_keys(
      backupVersion->version,
      room,
      session_id,
      [room, session_id, sessionDecryptionKey](const mtx::responses::backup::SessionBackup &bk,
                                               mtx::http::RequestErr err) {
          if (err) {
              if (err->status_code != 404)
                  nhlog::crypto()->error("Failed to dowload key {}:{}: {} - {}",
                                         room,
                                         session_id,
                                         mtx::errors::to_string(err->matrix_error.errcode),
                                         err->matrix_error.error);
              return;
          }
          try {
              auto session = decrypt_session(bk.session_data, sessionDecryptionKey);

              if (session.algorithm != mtx::crypto::MEGOLM_ALGO)
                  // don't know this algorithm
                  return;

              MegolmSessionIndex index;
              index.room_id    = room;
              index.session_id = session_id;
              index.sender_key = session.sender_key;

              GroupSessionData data{};
              data.forwarding_curve25519_key_chain = session.forwarding_curve25519_key_chain;
              data.sender_claimed_ed25519_key      = session.sender_claimed_keys["ed25519"];
              // online key backup can't be trusted, because anyone can upload to it.
              data.trusted = false;

              auto megolm_session =
                olm::client()->import_inbound_group_session(session.session_key);

              if (!cache::inboundMegolmSessionExists(index) ||
                  olm_inbound_group_session_first_known_index(megolm_session.get()) <
                    olm_inbound_group_session_first_known_index(
                      cache::getInboundMegolmSession(index).get())) {
                  cache::saveInboundMegolmSession(index, std::move(megolm_session), data);

                  nhlog::crypto()->info("imported inbound megolm session "
                                        "from key backup ({}, {})",
                                        room,
                                        session_id);

                  // call on UI thread
                  QTimer::singleShot(0, ChatPage::instance(), [index] {
                      ChatPage::instance()->receivedSessionKey(index.room_id, index.session_id);
                  });
              }
          } 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;
          }
      });
}

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);
      });

    // http::client()->room_keys
}

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 (unless it is actually us