Olm.cpp

#include "Olm.hpp"

#include "Cache.h"
#include "Logging.hpp"

using namespace mtx::crypto;

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

namespace olm {

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

void
handle_to_device_messages(const std::vector<nlohmann::json> &msgs)
{
        if (msgs.empty())
                return;

        nhlog::crypto()->info("received {} to_device messages", msgs.size());

        for (const auto &msg : msgs) {
                try {
                        OlmMessage olm_msg = msg;
                        handle_olm_message(std::move(olm_msg));
                } catch (const nlohmann::json::exception &e) {
                        nhlog::crypto()->warn(
                          "parsing error for olm message: {} {}", e.what(), msg.dump(2));
                } catch (const std::invalid_argument &e) {
                        nhlog::crypto()->warn(
                          "validation error for olm message: {} {}", e.what(), 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) {
                        nhlog::crypto()->info("decrypted olm payload: {}", payload.value().dump(2));
                        create_inbound_megolm_session(msg.sender, msg.sender_key, payload.value());
                        return;
                }

                // Not a PRE_KEY message
                if (cipher.second.type != 0) {
                        // TODO: log that it should have matched something
                        return;
                }

                handle_pre_key_olm_message(msg.sender, msg.sender_key, cipher.second);
        }
}

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

        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::client()->saveOlmAccount(olm::client()->save("secret"));
        } catch (const olm_exception &e) {
                nhlog::crypto()->critical(
                  "failed to create inbound session with {}: {}", sender, e.what());
                return;
        }

        if (!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 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()->info("decrypted message: \n {}", plaintext.dump(2));

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

        create_inbound_megolm_session(sender, sender_key, plaintext);
}

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

        // Always chech before for existence.
        auto res     = cache::client()->getOutboundMegolmSession(room_id);
        auto payload = olm::client()->encrypt_group_message(res.session, body);

        // 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 = res.data.session_id;
        data.device_id  = device_id;

        auto message_index = olm_outbound_group_session_message_index(res.session);
        nhlog::crypto()->info("next message_index {}", message_index);

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

        return data;
}

boost::optional<json>
try_olm_decryption(const std::string &sender_key, const OlmCipherContent &msg)
{
        auto session_ids = cache::client()->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::client()->getOlmSession(sender_key, id);

                if (!session)
                        continue;

                mtx::crypto::BinaryBuf text;

                try {
                        text = olm::client()->decrypt_message(session->get(), msg.type, msg.body);
                        cache::client()->saveOlmSession(id, std::move(session.value()));

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

        return {};
}

void
create_inbound_megolm_session(const std::string &sender,
                              const std::string &sender_key,
                              const nlohmann::json &payload)
{
        std::string room_id, session_id, session_key;

        try {
                room_id     = payload.at("content").at("room_id");
                session_id  = payload.at("content").at("session_id");
                session_key = payload.at("content").at("session_key");
        } catch (const nlohmann::json::exception &e) {
                nhlog::crypto()->critical(
                  "failed to parse plaintext olm message: {} {}", e.what(), payload.dump(2));
                return;
        }

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

        try {
                auto megolm_session = olm::client()->init_inbound_group_session(session_key);
                cache::client()->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 olm_exception &e) {
                nhlog::crypto()->critical("failed to create inbound megolm session: {}", e.what());
                return;
        }

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

} // namespace olm