From 755cc434d0d8672d3f1c3c5db718f273886d3e6d Mon Sep 17 00:00:00 2001
From: Konstantinos Sideris <sideris.konstantin@gmail.com>
Date: Sat, 15 Sep 2018 17:56:03 +0300
Subject: [PATCH] Add methods for importing/exporting inbound megolm sessions
---
include/mtxclient/crypto/client.hpp | 10 ++++-
lib/crypto/client.cpp | 30 +++++++++++++++
tests/e2ee.cpp | 59 +++++++++++++++++++++++++++++
3 files changed, 98 insertions(+), 1 deletion(-)
diff --git a/include/mtxclient/crypto/client.hpp b/include/mtxclient/crypto/client.hpp
index ef16c3f5f..7c46b5d2d 100644
--- a/include/mtxclient/crypto/client.hpp
+++ b/include/mtxclient/crypto/client.hpp
@@ -214,10 +214,18 @@ session_id(OlmSession *s);
std::string
session_id(OlmOutboundGroupSession *s);
-//! Retrieve the session key.
+//! Retrieve the session key from an *outbound* megolm session.
std::string
session_key(OlmOutboundGroupSession *s);
+//! Retrieve the session key from an *inbound* megolm session.
+std::string
+export_session(OlmInboundGroupSession *s);
+
+//! Create an *inbound* megolm session from an exported session key.
+InboundGroupSessionPtr
+import_session(const std::string &session_key);
+
bool
matches_inbound_session(OlmSession *session, const std::string &one_time_key_message);
diff --git a/lib/crypto/client.cpp b/lib/crypto/client.cpp
index 22f95ecd7..0d0f39619 100644
--- a/lib/crypto/client.cpp
+++ b/lib/crypto/client.cpp
@@ -437,6 +437,36 @@ mtx::crypto::session_key(OlmOutboundGroupSession *s)
return std::string(tmp.begin(), tmp.end());
}
+std::string
+mtx::crypto::export_session(OlmInboundGroupSession *s)
+{
+ const size_t len = olm_export_inbound_group_session_length(s);
+ const uint32_t index = olm_inbound_group_session_first_known_index(s);
+
+ auto session_key = create_buffer(len);
+ const int rc =
+ olm_export_inbound_group_session(s, session_key.data(), session_key.size(), index);
+
+ if (rc == -1)
+ throw olm_exception("session_key", s);
+
+ return std::string(session_key.begin(), session_key.end());
+}
+
+InboundGroupSessionPtr
+mtx::crypto::import_session(const std::string &session_key)
+{
+ auto session = create_olm_object<InboundSessionObject>();
+
+ const int rc = olm_import_inbound_group_session(
+ session.get(), reinterpret_cast<const uint8_t *>(session_key.data()), session_key.size());
+
+ if (rc == -1)
+ throw olm_exception("import_session", session.get());
+
+ return session;
+}
+
bool
mtx::crypto::matches_inbound_session(OlmSession *session, const std::string &one_time_key_message)
{
diff --git a/tests/e2ee.cpp b/tests/e2ee.cpp
index 1a1f0e05f..dd0aa9ed8 100644
--- a/tests/e2ee.cpp
+++ b/tests/e2ee.cpp
@@ -1071,6 +1071,65 @@ TEST(ExportSessions, EncryptDecrypt)
EXPECT_EQ(json(keys).dump(), json(restored_keys).dump());
}
+TEST(ExportSessions, InboundMegolmSessions)
+{
+ auto alice = std::make_shared<OlmClient>();
+ alice->create_new_account();
+ alice->generate_one_time_keys(1);
+
+ auto bob = std::make_shared<OlmClient>();
+ bob->create_new_account();
+ bob->generate_one_time_keys(1);
+
+ // ==================== SESSION SETUP =================== //
+
+ // Alice wants to send an encrypted megolm message to Bob.
+ const std::string secret_message = "Hey, Bob!";
+
+ // Alice creates an outbound megolm session that will be used by both parties.
+ auto outbound_megolm_session = alice->init_outbound_group_session();
+ auto msg_index = olm_outbound_group_session_message_index(outbound_megolm_session.get());
+ ASSERT_EQ(msg_index, 0);
+
+ // Alice extracts the session id & session key so she can share them with Bob.
+ const auto session_id = mtx::crypto::session_id(outbound_megolm_session.get());
+ const auto session_key = mtx::crypto::session_key(outbound_megolm_session.get());
+
+ // Encrypt the message using megolm.
+ auto encrypted_secret_message =
+ alice->encrypt_group_message(outbound_megolm_session.get(), secret_message);
+
+ msg_index = olm_outbound_group_session_message_index(outbound_megolm_session.get());
+ ASSERT_EQ(msg_index, 1);
+
+ // Bob will use the session_key to create an inbound megolm session.
+ // The session_id will be used to map future messages to this session.
+ auto inbound_megolm_session = bob->init_inbound_group_session(session_key);
+
+ // Bob can finally decrypt Alice's original message.
+ auto ciphertext =
+ std::string((char *)encrypted_secret_message.data(), encrypted_secret_message.size());
+ auto bob_plaintext = bob->decrypt_group_message(inbound_megolm_session.get(), ciphertext);
+
+ auto output_str = std::string((char *)bob_plaintext.data.data(), bob_plaintext.data.size());
+ ASSERT_EQ(output_str, secret_message);
+
+ // ==================== SESSION IMPORT/EXPORT =================== //
+
+ auto exported_session_key = export_session(inbound_megolm_session.get());
+ auto restored_inbound_session = import_session(exported_session_key);
+
+ // Decrypt message again.
+ auto restored_ciphertext =
+ std::string((char *)encrypted_secret_message.data(), encrypted_secret_message.size());
+ auto restored_plaintext =
+ bob->decrypt_group_message(restored_inbound_session.get(), restored_ciphertext);
+
+ auto restored_output_str =
+ std::string((char *)restored_plaintext.data.data(), restored_plaintext.data.size());
+ ASSERT_EQ(restored_output_str, secret_message);
+}
+
TEST(Encryption, DISABLED_HandleRoomKeyEvent) {}
TEST(Encryption, DISABLED_HandleRoomKeyRequestEvent) {}
TEST(Encryption, DISABLED_HandleNewDevices) {}
--
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