Matrix Client Library in C

This is a library implementing parts of the Matrix Client-Server API. It is written in C and supports sending and receiving of messages, including end-to-end encryption. Device verification is also supported.

Building

Building requires a C/C++ compiler and make.

To build the dependencies run make deps. All dependencies are included in this repository.

To build any of the examples run make out/examples/<example>.

To use the library:

Add src/matrix.c to compilation
Add either src/matrix_http_mongoose.c or src/matrix_http_esp32.c to compilation
Add out/*.o to compilation
Add include path src/
Add include path ext/olm/include/
Add include path ext/mjson/src/
Add include path ext/mongoose/

To build the example for the ESP32 start an ESP-IDF shell in esp32/esp_project or esp32/esp_project_riscv and run:

idf.py build
idf.py flash
idf.py monitor

Examples for the ESP32 are in esp32/esp_project/main. There are currently two, SendEncrypted and Verify. The example can be set in esp32/esp_project(_risc_v)/main/CMakeLists.txt as the second argument after SRCS.

Any code using the library should compile under ESP-IDF if the following code is added at the end of the file: ```c #include "wifi.h"

void app_main(void) { wifi_init(WIFI_SSID, WIFI_PASSWORD);

main();

}

```

To use the library in an ESP-IDF project:

Add the matrix and olm components (can be found in esp32/esp_project/components/)
Add wifi.c/.h (can be found in esp32/esp_project/main/)
Add SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fpermissive") to CMakeLists.txt
Call wifi_init("<SSID>", "<PASSWORD>") before initializing the library

Dependencies

Mongoose

mjson

Olm

Examples

(De)Initialization

```c MatrixClient * client = (MatrixClient*)malloc(sizeof(MatrixClient)); MatrixClientInit(client);

MatrixHttpInit(&client->hc, SERVER); MatrixClientSetUserId(client, USER_ID);

MatrixClientLoginPassword(client, USERNAME, PASSWORD, DEVICE_NAME);

MatrixClientDeleteDevice(client);

MatrixHttpDeinit(&client->hc); ```

Uploading keys

c MatrixClientGenerateOnetimeKeys(client, 10); MatrixClientUploadOnetimeKeys(client); MatrixClientUploadDeviceKeys(client);

Sending an encrypted message

```c MatrixMegolmOutSession * megolmOutSession; MatrixClientNewMegolmOutSession(&client, ROOM_ID, &megolmOutSession);

MatrixClientShareMegolmOutSession(&client, USER_ID, DEVICE_ID2, megolmOutSession);

MatrixClientSendEventEncrypted(&client, ROOM_ID, "m.room.message", "{"body":"Hello","msgtype":"m.text"}"); ```

Verification

```c // Request an encrypted event to enable verification STATIC char eventBuffer[1024]; MatrixClientGetRoomEvent(client, ROOM_ID, EVENT_ID, eventBuffer, 1024);

#define SYNC_BUFFER_SIZE 1024*10 STATIC char syncBuffer[SYNC_BUFFER_SIZE]; STATIC char nextBatch[1024];

while (! client->verified) { MatrixClientSync(client, syncBuffer, SYNC_BUFFER_SIZE, nextBatch, 1024); } ```