CoAP-SPARK is a library implementing the Constrained Application Protocol (CoAP) as defined in RFC 7252, developed in the SPARK language, the formally verified subset of the Ada programming language.
The objective is to build a formally verified working CoAP implementation, mainly for academic purposes.
CoAP-SPARK uses:
- Alire as source package manager (independently installed)
- RecordFlux as a tool facilitating the implementation of the verifiable protocol parser and the state machine of a session (included as Git submodule)
- WolfSSL as library for implementing the DTLS communications (included as Git submodule)
- GNAT 14.2.1 (toolchain managed by Alire)
- GNATProve 14.1.1 (dependency managed by Alire)
- bbt 0.0.6 for testing (installable via Alire)
Clone the repository recursing on submodules:
git clone --recurse-submodules https://github.com/mgrojo/coap_spark.git
The source code generated by RecordFlux is already added to the repository. If you want to generate it yourself, follow these two steps:
Build RecordFlux following instructions on
tools/RecordFlux/doc/development_guide/index.rst.
Generate source code from the CoAP model using RecordFlux with:
make generate
Install Alire and build the library running:
alr build
For building the client program:
cd client ; alr build
Install bbt running:
alr install bbt
And then run the tests with:
cd client/tests ; make
See client/tests/coap_client_tests.md
for the specification of these tests.
There are also some unit tests for the library. To run them, enter the tests/
directory and run:
cd tests; alr run
The project (library and client) is currently proved up to the silver mode.
The proof/ directory constains the results of passing GNATProve. You can replay it running:
alr gnatprove --replay
Or if you want to start afresh,for example, using a different version of
gnatprove, simply run:
alr gnatprove
The project is using gnatprove from the Alire community index. You can install it running this:
alr install gnatprove
The Colibri solver has to be installed separately, for example, from the
GNAT Community Edition 2021. After installation,
and before running gnatprove, you have to put {GNAT-2021-HOME}/libexec/spark/bin
in the PATH, so gnatprove can find the colibri executable.
CoAP-SPARK is a working and verified implementation of CoAP from the client side.
The main objective of CoAP-SPARK is to be the subject of my Master's Thesis, but I think it can be used in scenarios where this limitations are not an issue:
- There are no retransmissions.
- Block-wise transfers are not implemented. This isn't part of main RFC 7252 for CoAP, but of the RFC 7959.
- It only supports NoSec and PreSharedKey security modes.
There's no server implementation for the moment, but it wouldn't be too difficult to add, following the example of the client.
Regarding the implemented client is able to substitute libcoap's coap-client when called from a project like ikea-smartlight.
Bug reports, feedback or suggestions on how to improve the library are very welcome.