Do not use the code in this repository for anything serious; there might be unidentified security vulnerabilities present. You are encouraged to report such issues when found.
This repository contains two libraries:
-
xmpp.c: a bare minimum framework for keeping track of an XMPP session. -
omemo.c: a compact implementation of OMEMO.
-
Run on embedded: support for ESP32 on ESP-IDF & Raspberry Pi Pico [W] on pico-sdk (untested).
-
Be portable to any OS; empower any system to connect to XMPP networks.
-
Be compatible with the major XMPP clients and servers (Prosody guaranteed).
-
Low amount of code while still being readable.
-
Control of memory management (when possible).
-
Implement the XMPP spec word-for-word.
-
Have an extension/plugin system or support multiple versions of a protocol, for additional features you must patch the library.
omemo.c contains implementations of X3DH, Double Ratchet and
Protobuf with an API that is specifically tailored to OMEMO. We do not
have dependencies on (any) libsignal or libolm code.
Curve25519 and Ed25519 functions are handled by the
c25519 library, which is
included as amalgamation in /c25519.c and /c25519.h. Some changes
have been made there which can be inspected with $ git diff 2eef25dc -- c25519.*. This Curve25519 implementation is noticably slower than
curve25519_donna. Decrypting messages can take hundreds of
milliseconds to seconds and filling a hundred prekeys can take up to
minutes on microcontrollers. To speed things up, cosmopolitan's
overhaul
of the Everest Curve25519
implementation is enabled on supported systems.
The version of OMEMO implemented is 0.3.0, updating this library to a newer version of OMEMO should be trivial, but supporting multiple versions at once will probably make the code a mess.
-
MbedTLS 3.0+
-
C99 compiler
-
docker-compose (for testing)
Running the tests:
$ make start-prosody
$ make test
Using this library for your own project:
Copy over /xmpp.c, /xmpp.h, /yxml.c and /yxml.h to your
project.
If you want to use OMEMO, copy over /omemo.c, /omemo.h,
/c25519.c and /c25519.h.
In both cases, you must link against libmbedcrypto (and/or configure your mbedtls build to only include the needed functions.
The im.c example shows how additional
functionality can be used in combination with the library. The example
is not a feature complete instant messenger and for simplicity's sake
the code is full of hardcoded and spec deviating behaviour that should
not represent a serious XMPP client.
Run the im (instant messenger) example:
$ make runim
By default the localhost self-signed certificate is used. For a simple
test you can spin up prosody ($ make start-prosody) and run the echo
bot ($ make start-omemo-bot).
Compile the esp-idf version of the im:
$ cat > examples/esp-im/config.h <<EOF
#define IM_WIFI_SSID "ssid"
#define IM_WIFI_PASS "password"
#define IM_SERVER_IP "192.168.1.2"
EOF$ make esp-im
$ ESP_DEV=/dev/ttyUSB0 make esp-upload
$ ESP_DEV=/dev/ttyUSB0 make esp-monitor
xmpp-omemo-demo.mp4
The code in this repository is licensed under ISC, all vendored code in this repository is also permissively licensed:
yxml is licensed under MIT, c25519 is in the public domain and Everest Curve25519 is licensed under Apache-2.0.
While not directly included, MbedTLS is dual-licensed under Apache-2.0 or GPL-2.0-or-later.