Add OSCORE Support

[ln4c]

This pull request aims to provide support for OSCORE in libcoap-rs.
It adds a new feature flag "oscore" which has to be activated to enable all functions regarding OSCORE under which we provide the following:

libcoap	libcoap-rs
coap_oscore_conf_t	OscoreConf::new
coap_new_oscore_recipient	CoapContext::new_oscore_recipient
coap_delete_oscore_recipient	CoapContext::delete_oscore_recipient
coap_new_client_session_oscore	CoapClientSession::connect_oscore
coap_context_oscore_server	CoapContext::oscore_server

We introduced two new structs OscoreConf and OscoreRecipient which are currently located within oscore.rs.

We also added new errors to allow for error-handling by the user in errors.rs.

There is also a minimal client and server example available, deriving from the official documentation.

Security was a priority and all unsafe calls have been annotated with an appropriate security notice, as is the standard for this project.

[github-actions]

Workflow Status Report

Generated for commit 0a33cbf on Tue Aug 5 21:14:01 UTC 2025.

In case of failure, clippy warnings and rustfmt changes (if any) will be indicated as CI check warnings in the file comparison view.

Documentation: Download

Coverage Report: Download

Note: Online versions of documentation and coverage reports may not be available indefinitely, especially after the pull request was merged.

Code Coverage Report

Coverage target is 80%.

Expand to view coverage statistics

file	coverage	covered	missed_lines
libcoap-sys/src/lib.rs	77.78%	133 / 171	370-381, 489-492, 500, 527-544, 669-672, 756-759
libcoap/src/context.rs	59.52%	175 / 294	131, 196-241, 252-257, 275, 304, 351-355, 388, 403-404, 595-611, 645, 650, 666, 674-836
libcoap/src/crypto/pki_rpk/key.rs	56.32%	49 / 87	179-213, 242-250, 252-255, 261-263
libcoap/src/crypto/pki_rpk/mod.rs	26.44%	87 / 329	36-275, 454-486, 507-605, 613, 616, 650-668, 678-680, 685-687, 692-694, 755, 767-903
libcoap/src/crypto/pki_rpk/pki.rs	76.15%	99 / 130	90-149, 302-315
libcoap/src/crypto/pki_rpk/rpk.rs	68.33%	41 / 60	68-98, 160-171
libcoap/src/crypto/psk/client.rs	43.31%	55 / 127	71-75, 83, 106-192, 234-242, 269-271, 276-278, 306-338
libcoap/src/crypto/psk/key.rs	55.42%	46 / 83	42-49, 163-205
libcoap/src/crypto/psk/mod.rs	0.00%	0 / 24	30-96
libcoap/src/crypto/psk/server.rs	32.43%	48 / 148	70-89, 97, 100, 117-120, 146-148, 153-155, 160-162, 190-241, 262, 278-403
libcoap/src/error.rs	0.00%	0 / 6	148-228
libcoap/src/event.rs	29.73%	11 / 37	36-168
libcoap/src/lib.rs	0.00%	0 / 33	62-165
libcoap/src/mem.rs	72.56%	119 / 164	148-163, 196-198, 210-212, 280, 296-298, 319-324, 353-355, 369, 381-393, 454-456, 473, 481-488, 507, 527, 531
libcoap/src/message/mod.rs	57.37%	183 / 319	105-108, 110-131, 139-145, 147-168, 172, 174, 176, 208, 210, 213-222, 225-243, 245-249, 265-275, 295-302, 398-399, 441, 447, 478, 488-491, 497-499, 506, 511-523, 529, 549-551, 561-563
libcoap/src/message/request.rs	33.79%	99 / 293	51, 68-202, 228-256, 264-365, 371-375, 380-381, 383-386, 389, 395-400, 430-432, 436, 439-441, 444-446, 449, 452, 455, 458, 461, 472-479
libcoap/src/message/response.rs	22.17%	45 / 203	36-160, 165, 168, 171, 174, 177, 195-325, 329-334, 360
libcoap/src/prng.rs	54.79%	40 / 73	66, 78-116, 139-149, 196
libcoap/src/protocol.rs	33.33%	54 / 162	164-166, 171-176, 178-193, 195-196, 203-208, 210-225, 227-228, 285-287, 308, 322-324, 369-374, 383-388, 444-469, 475-488, 520, 522
libcoap/src/resource.rs	67.23%	160 / 238	62, 94-96, 171-176, 183-208, 214-219, 249, 266-288, 300-303, 319-339, 351-354, 387-396, 529-531
libcoap/src/session/client.rs	87.27%	96 / 110	168, 195, 262, 270-272, 278-280, 327-333
libcoap/src/session/mod.rs	41.13%	102 / 248	62-74, 105, 115-230, 240-285, 294-310, 319-330, 359, 363, 395-415, 437, 445, 477, 484, 502-508, 583, 589
libcoap/src/session/server.rs	80.88%	55 / 68	75-77, 81, 152, 162-164, 179, 194-200
libcoap/src/transport.rs	72.73%	16 / 22	29-36, 55
libcoap/src/types.rs	54.69%	268 / 490	71-125, 131-160, 210-243, 253-265, 272-278, 284-286, 295, 371, 411, 450, 562, 571, 583, 610, 636-705, 758, 803-824, 845-868, 879-964
libcoap/tests/common/dtls.rs	93.02%	40 / 43	49, 54-55
libcoap/tests/common/mod.rs	92.00%	69 / 75	85-88, 92, 126
libcoap/tests/dtls_pki_client_server_test.rs	100.00%	65 / 65
libcoap/tests/dtls_psk_client_server_test.rs	100.00%	21 / 21
libcoap/tests/dtls_rpk_client_server_test.rs	100.00%	6 / 6
libcoap/tests/tcp_client_server_test.rs	100.00%	17 / 17
libcoap/tests/udp_client_server_test.rs	100.00%	17 / 17

Total coverage: 53.23%

[pulsastrix]

Hi, thanks for the contribution!
You can find my initial comments below.

Regarding the examples: Would it be possible to add an abridged version of the examples (without the EDHOC part) to the examples subdirectory or to the module-level rustdoc in oscore.rs?
That way, we can use those as (no_run) tests.

Lastly, it would also be nice if we had a runnable test case that runs both a server and a client and performs a basic request, akin to the test cases already present for UDP and DTLS.

[pulsastrix]

Sorry for the long wait, I was a bit preoccupied with finishing my thesis 😅.

Here is my second review of this PR, most of these comments are just minor optimizations and stuff regarding memory leaks.

[ln4c]

Thank you for your suggestions and please excuse my delayed response. Apart from the improvement for save_seq_num_func, these issues should now be resolved.

[pulsastrix]

Thank you for your suggestions and please excuse my delayed response.

No problem, thanks again for your work on this.

Apart from the improvement for save_seq_num_func, these issues should now be resolved.

LGTM! (aside from the comments that were moved to/will be addressed in separate issues)