IETF CoAP RFC 7252 + RFC 7641 — Spec Coverage

RFC 7252: The Constrained Application Protocol — IETF, June 2014 →

RFC 7641: Observing Resources in CoAP — IETF, September 2015 →

Context: CoAP is a RESTful spec for constrained devices. ZeroDDS implements it in crates/coap-bridge/: the wire codec (Section 3, 5.10, RFC 7641 §2) as a no_std+alloc library, plus reliability, block-wise transfer (RFC 7959), observe, a DTLS transport (feature dtls), OSCORE and the daemon.

Implementation:

crates/coap-bridge/ · docs.rs — codec, transport building blocks and the daemon zerodds-coap-bridged.

RFC 7252 §1 Introduction

§1.1 Features

Spec: §1.1, p. 5 (RFC) — REST model, UDP-bound, multicast support, DTLS security, asynchronous messaging.

Repo: crates/coap-bridge/src/lib.rs crate doc.

Tests: REST methods + response classes: crates/coap-bridge/src/message.rs::tests::well_known_codes_match_spec_values; asynchronous messaging (CON/NON/ACK/RST): crates/coap-bridge/src/message.rs::tests::message_type_round_trips_via_bits; multicast support: crates/coap-bridge/src/multicast.rs::tests::well_known_addresses_match_spec; DTLS security: crates/coap-bridge/src/dtls.rs::tests::psk_is_secure; UDP-bound (default ports 5683/5684): crates/coap-bridge/src/uri.rs::tests::default_port_returns_5684_for_coaps.

Status: done — overview; multicast and DTLS are items of their own (§8, §9, §11).

§1.2 Terminology

Spec: §1.2, p. 6-9 — endpoint, sender, recipient, token, origin server, cacheable, resource, etc.

Repo: —

Tests: —

Status: n/a (informative) — glossary; a semantic reference point without a code mapping.

RFC 7252 §2 Constrained Application Protocol

§2.1 Messaging model

Spec: §2.1, p. 11 — CON/NON/ACK/RST.

Repo: crates/coap-bridge/src/message.rs::MessageType.

Tests: message::tests::message_type_round_trips_via_bits.

Status: done

§2.2 Request/response model

Spec: §2.2, p. 12 — method codes + response codes.

Repo: crates/coap-bridge/src/message.rs::CoapCode with the constants GET/POST/PUT/DELETE/CREATED/DELETED/VALID/CHANGED/CONTENT/BAD_REQUEST/NOT_FOUND/INTERNAL_SERVER_ERROR.

Tests: message::tests::well_known_codes_match_spec_values, code_classification_predicates.

Status: done

§2.3 Intermediaries and caching

Spec: §2.3, p. 15 — forward proxies, caches.

Repo: crates/coap-bridge/src/caching_proxy.rs::{CoapCache, CacheLookup, ProxyConfig, ProxyMode} — a cache layer with freshness tracking + stale/revalidate path; proxy configuration with forward/reverse mode + hop-count cap (spec §5.7.1 loop protection).

Tests: crates/coap-bridge/src/caching_proxy.rs::tests::{empty_cache_returns_miss, store_then_fresh_lookup, stale_with_etag_yields_validation_path, stale_without_etag_yields_miss, cap_evicts_oldest, evict_expired_without_etag_keeps_revalidatable, proxy_config_default_is_forward_coap_to_coap}.

Status: done — caching + forward-proxy configuration live.

§2.4 Resource discovery

Spec: §2.4, p. 15 — .well-known/core (RFC 6690).

Repo: crates/coap-bridge/src/core_link.rs::{CoreLink, encode_links, decode_links}.

Tests: crates/coap-bridge/src/core_link.rs::tests::{encode_simple_link_format, encode_multiple_links_comma_separated, decode_round_trip_with_attrs, decode_handles_numeric_attr, decode_handles_quoted_string_with_comma, decode_rejects_uri_without_brackets, decode_attr_without_value_yields_empty, encode_escapes_inner_quotes}.

Status: done

RFC 7252 §3 Message format

§3 Header format (Ver/T/TKL/Code/MID)

Spec: §3, p. 16 — a 4-byte fixed header. Version MUST be 1 (01 binary), TKL 0..=8 (9-15 reserved).

Repo: crates/coap-bridge/src/codec.rs::encode/decode sets Version=1 on encode and rejects other versions on decode.

Tests: codec::tests::encodes_minimum_get_request_to_4_byte_header, unsupported_version_decode_fails, reserved_token_length_9_through_15_decode_fails, token_length_above_8_is_rejected_on_encode.

Status: done

§3 Token

Spec: §3, p. 16 — a token 0..=8 bytes after the header.

Repo: crates/coap-bridge/src/message.rs::CoapMessage::token.

Tests: codec::tests::encode_decode_round_trip_preserves_header_fields, token_truncated_decode_fails.

Status: done

§3 Payload marker

Spec: §3, p. 16-17 — 0xFF marks the start of the payload. “The presence of a marker followed by a zero-length payload MUST be processed as a message format error.”

Repo: crates/coap-bridge/src/codec.rs (encode + decode).

Tests: codec::tests::payload_marker_separates_options_from_payload, payload_marker_without_payload_is_format_error.

Status: done

§3.1 Option format (delta encoding)

Spec: §3.1, p. 17-19 — a 4-bit delta nibble + a 4-bit length nibble + extended forms (13/14) + reserved (15). Options “MUST appear in order of their Option Numbers”.

Repo: crates/coap-bridge/src/codec.rs::encode_extended/decode_extended. Encode sorts options before the delta computation.

Tests: codec::tests::single_short_option_encodes_in_one_byte_header, option_delta_extended_13_uses_one_extra_byte, option_delta_extended_14_uses_two_extra_bytes, option_length_extended_13_uses_one_extra_byte, delta_encoding_sums_across_multiple_options, options_are_sorted_on_encode.

Status: done

§3.2 Option value formats

Spec: §3.2, p. 19-20 — empty, opaque, uint, string. uint “without leading zero bytes”; “MUST be prepared to process values with leading zero bytes”.

Repo: crates/coap-bridge/src/option.rs::OptionValue + uint_to_minimal_bytes + uint_from_bytes.

Tests: option::tests::uint_zero_is_empty_byte_sequence, uint_one_is_single_byte, uint_strips_leading_zero_bytes, uint_from_bytes_decodes_minimal_form, uint_from_bytes_handles_leading_zeros, uint_from_bytes_rejects_more_than_8_bytes, option_value_to_wire_bytes_matches_format.

Status: done

RFC 7252 §4 Message transmission

§4.1 Messages and endpoints

Spec: §4.1, p. 20 — endpoint identification via IP+port.

Repo: crates/coap-bridge/src/bridge.rs (endpoint as a Vec<u8> ID); the UDP reactor deliberately lives at the caller layer via crates/transport-udp/ — this separation allows no_std builds with their own transport (e.g. an embedded stack without OS sockets). Spec §4.1 standardizes the endpoint identification, not the UDP reactor itself.

Tests: crates/coap-bridge/src/bridge.rs::tests::{parses_topic_only, parses_topic_with_key, rejects_non_dds_path, bridge_apply_write_then_read_round_trip, bridge_observe_register_increments_observer_count}.

Status: done — endpoint tracking as a spec-conformant Vec ID; the transport decoupling is an intentional architecture for no_std targets.

§4.2-§4.7 Reliability + deduplication + congestion

Spec: §4.2-§4.7, p. 21-26 — CON retry with exponential backoff up to MAX_RETRANSMIT; §4.5 “The recipient […] SHOULD acknowledge each duplicate copy of a Confirmable message […] but SHOULD process any request or response in the message only once” — Message ID duplicates within EXCHANGE_LIFETIME (CON) resp. NON_LIFETIME (NON); §4.7 NSTART as the cap on simultaneously outstanding interactions towards one server.

Repo: crates/coap-bridge/src/reliability.rs::{ReliabilityTracker, PendingConfirmable, TickOutput} — send_confirmable/receive_ack/receive_rst/tick cover the CON retry + ACK/RST path; crates/coap-bridge/src/reliability.rs::{DuplicateDetector, DedupKind, Reception} with receive/remember_ack/evict_expired for the §4.5 deduplication (cached ACK instead of a second processing); crates/coap-bridge/src/reliability.rs::OutstandingInteractions with try_begin/end for the §4.7 NSTART cap per server.

Tests: crates/coap-bridge/src/reliability.rs::tests::{tick_before_timeout_does_nothing, tick_after_timeout_retransmits, exhausting_retransmits_times_out, interval_doubles_per_retransmit, send_then_ack_clears_pending, rst_clears_pending, duplicate_message_id_within_exchange_lifetime_is_detected, duplicate_entry_expires_after_its_lifetime, duplicate_detection_is_per_endpoint, duplicate_table_cap_bounds_memory, nstart_caps_outstanding_interactions_per_server}.

Status: done

§4.8 Transmission parameters

Spec: §4.8, p. 27-29 — Table 2: ACK_TIMEOUT 2 s, ACK_RANDOM_FACTOR 1.5, MAX_RETRANSMIT 4, NSTART 1, DEFAULT_LEISURE 5 s, PROBING_RATE 1 byte/s. §4.8.2 derives from them: MAX_TRANSMIT_SPAN = ACK_TIMEOUT * ((2 ** MAX_RETRANSMIT) - 1) * ACK_RANDOM_FACTOR (45 s), MAX_TRANSMIT_WAIT (93 s), EXCHANGE_LIFETIME = MAX_TRANSMIT_SPAN + (2 * MAX_LATENCY) + PROCESSING_DELAY (247 s), NON_LIFETIME (145 s).

Repo: crates/coap-bridge/src/reliability.rs::{ACK_TIMEOUT_MS, ACK_RANDOM_FACTOR_NUM, ACK_RANDOM_FACTOR_DEN, MAX_RETRANSMIT, NSTART, DEFAULT_LEISURE_MS, PROBING_RATE_BYTES_PER_SEC, MAX_LATENCY_MS, PROCESSING_DELAY_MS, MAX_TRANSMIT_SPAN_MS, MAX_TRANSMIT_WAIT_MS, EXCHANGE_LIFETIME_MS, NON_LIFETIME_MS}; initial_interval uses ACK_TIMEOUT * ACK_RANDOM_FACTOR as the first retry interval.

Tests: crates/coap-bridge/src/reliability.rs::tests::{transmission_parameters_match_spec_4_8_table_2, derived_transmission_parameters_follow_spec_4_8_2_formulas, backoff_schedule_follows_ack_timeout_and_random_factor} — the last one checks the resulting retry sequence 3000/6000/12000/24000 ms and the give-up after MAX_RETRANSMIT at MAX_TRANSMIT_WAIT.

Status: done

RFC 7252 §5 Request/response semantics

§5.1 Requests

Spec: §5.1, p. 35-36 — request definition: method code (1-31), token, options, payload.

Repo: method codes 1=GET, 2=POST, 3=PUT, 4=DELETE as CoapCode variants in crates/coap-bridge/src/message.rs.

Tests: message::tests::well_known_codes_match_spec_values.

Status: done

§5.2 Responses

Spec: §5.2, p. 36 — response definition: response code (2.xx success, 4.xx client error, 5.xx server error), echoed token.

Repo: response codes as CoapCode variants (2.05 Content, 4.04 Not Found, 5.00 Internal Server Error, etc.).

Tests: message::tests::well_known_codes_match_spec_values.

Status: done

§5.3 Request/response matching

Spec: §5.3, p. 37-39 — token-based matching for async replies (piggybacked, separate, reset).

Repo: the token field in CoapMessage as a Vec<u8> with a length constraint (TKL 0-8 bytes) + crates/coap-bridge/src/matching.rs::{PendingRequests, MatchError} with submit/complete/evict_expired and spec-§4.8 EXCHANGE_LIFETIME support; a DoS cap via max_pending.

Tests: matching::tests::{submit_empty_token_rejected, submit_then_complete_round_trip, complete_unknown_token_returns_none, submit_above_cap_rejected, submit_duplicate_token_rejected, evict_expired_removes_overdue_pendings, evict_keeps_fresh_pendings}.

Status: done — token wire format + pending-request map with lifetime eviction live.

§5.4 Options

Spec: §5.4, p. 39-43 — option-class properties: Critical/Elective, Unsafe/Safe, NoCacheKey, Repeatable.

Repo: option numbers in crates/coap-bridge/src/option.rs::numbers; the property bits derived from the option number in crates/coap-bridge/src/option.rs::{is_critical, is_unsafe, is_nocachekey, is_repeatable} following the §5.4.6 formula (Critical = (onum & 1), UnSafe = (onum & 2), NoCacheKey = ((onum & 0x1e) == 0x1c)) plus the same-named methods on CoapOption.

Tests: crates/coap-bridge/src/option.rs::tests::{critical_unsafe_nocachekey_bits_per_spec_5_4_6, repeatable_options_match_spec_table_4, observe_option_uses_number_6}.

Status: done

§5.5 Payloads and representations

Spec: §5.5.1/§5.5.3, p. 43-44 — the payload is a representation whose media type the Content-Format option names; §5.5.2 “If no Content-Format option is given, the payload of responses indicating a client or server error is a brief human-readable diagnostic message” in UTF-8.

Repo: crates/coap-bridge/src/message.rs::CoapMessage::payload as a Vec<u8>; the Content-Format option (number 12) via crates/coap-bridge/src/option.rs::CoapOption::content_format; the payload-marker split in crates/coap-bridge/src/codec.rs.

Tests: crates/coap-bridge/src/codec.rs::tests::{representation_carries_content_format_per_spec_5_5, diagnostic_payload_of_error_response_carries_no_content_format, payload_marker_separates_options_from_payload}.

Status: done

§5.6 Caching

Spec: §5.6, p. 44-46 — freshness lifetime via the Max-Age option; validation via the ETag option.

Repo: Max-Age (number 14) + ETag (number 4) option numbers defined; cache state logic in crates/coap-bridge/src/caching_proxy.rs::{CoapCache, CacheLookup, DEFAULT_MAX_AGE} with store/lookup/evict_expired_without_etag, a DoS-cap FIFO eviction, and the spec-§5.6.1 default Max-Age (60s).

Tests: caching_proxy::tests::{empty_cache_returns_miss, store_then_fresh_lookup, stale_with_etag_yields_validation_path, stale_without_etag_yields_miss, cap_evicts_oldest, evict_expired_without_etag_keeps_revalidatable}.

Status: done — cache state + freshness + ETag-validation path live.

§5.7 Proxying

Spec: §5.7, p. 46-49 — the Proxy-Uri option, forward/reverse proxy, HTTP mapping.

Repo: the Proxy-Uri option (number 35) defined + proxy logic in crates/coap-bridge/src/caching_proxy.rs::{ProxyConfig, ProxyMode} with forward/reverse mode + a max_hops cap (spec §5.7.1 loop protection) + an http_translation flag for the §10 path.

Tests: caching_proxy::tests::proxy_config_default_is_forward_coap_to_coap.

Status: partial — the Proxy-Uri option, forward/reverse mode and the hop limit are built as configuration; forwarding a request is missing (§5.7a).

§5.7a Forwarding through a proxy

Spec: §5.7, pp. 46-49 — a forward proxy performs the request against the target URI from Proxy-Uri, a reverse proxy maps it to an origin server, and both return the response.

Repo: —

Tests: —

Status: open — crates/coap-bridge/src/caching_proxy.rs holds only ProxyConfig/ProxyMode; no path forwards a request to the target.

§5.8 Method definitions

Spec: §5.8, p. 49-51 — GET/POST/PUT/DELETE semantics, idempotency.

Repo: method codes defined in crates/coap-bridge/src/message.rs + the method-property helpers crates/coap-bridge/src/method_props.rs::{is_safe, is_idempotent, is_method} with spec-conformant values (GET = safe + idempotent; PUT/DELETE = idempotent; POST = neither).

Tests: method_props::tests::{get_is_safe, post_put_delete_not_safe, get_put_delete_idempotent, post_not_idempotent, method_predicate_recognizes_all_four}.

Status: done — codes + method properties (safety + idempotency) declared.

§5.9 Response code definitions

Spec: §5.9, p. 52-58 — the complete list of all response codes (2.xx, 4.xx, 5.xx) with meaning.

Repo: all important codes as CoapCode variants in crates/coap-bridge/src/message.rs.

Tests: message::tests::well_known_codes_match_spec_values.

Status: done

§5.10 Option definitions

Spec: §5.10, p. 53-67 — the number registry: Uri-Host (3), ETag (4), If-None-Match (5), Uri-Port (7), Location-Path (8), Uri-Path (11), Content-Format (12), Max-Age (14), Uri-Query (15), Accept (17), Location-Query (20), Proxy-Uri (35), Proxy-Scheme (39), Size1 (60). Plus If-Match (1).

Repo: crates/coap-bridge/src/option.rs::numbers with all constants + the convenience constructors uri_path/content_format.

Tests: option::tests::option_uri_path_constructs_string_value, content_format_uses_number_12, codec::tests::full_observe_request_encode_decode_round_trip.

Status: done

RFC 7252 §6 CoAP URIs

§6.1-§6.5 CoAP URI scheme

Spec: §6, p. 67-72 — coap:// + coaps:// URI schemes.

Repo: crates/coap-bridge/src/uri.rs::{parse_coap_uri, CoapUri, default_port, UriError}. Default ports 5683 / 5684; path segments + query parameters are split out (for direct mapping into the Uri-Path/Uri-Query options); a fragment identifier is rejected (§6.1).

Tests: crates/coap-bridge/src/uri.rs::tests::{parses_basic_coap_uri, parses_coaps_default_port, parses_explicit_port, parses_query_params, parses_empty_path_when_no_slash, rejects_unknown_scheme, rejects_missing_host, rejects_invalid_port, rejects_fragment, default_port_returns_5684_for_coaps, round_trip_path_filtering_strips_empty_segments} (11).

Status: done — the coap/coaps URI-scheme parser live.

RFC 7252 §7 Discovery

§7.1-§7.2 Service + resource discovery

Spec: §7, p. 73-74 — multicast discovery + .well-known/core.

Repo: resource discovery via crates/coap-bridge/src/core_link.rs; service discovery via multicast in multicast.rs::{ALL_NODES_LINK_LOCAL_V4, ALL_NODES_LINK_LOCAL_V6, ALL_NODES_SITE_LOCAL_V6, validate_multicast_request} (see §8).

Tests: resource discovery: crates/coap-bridge/src/core_link.rs::tests::{encode_simple_link_format, decode_round_trip_with_attrs}; service discovery: crates/coap-bridge/src/multicast.rs::tests::{well_known_addresses_match_spec, valid_multicast_request_passes, multicast_request_must_not_be_confirmable}.

Status: partial — resource discovery via /.well-known/core and the multicast addresses are built and checked; service discovery by multicast needs the multicast reception of §8a.

RFC 7252 §8 Multicast CoAP

§8 Multicast operation

Spec: §8, p. 74-77 — IP-multicast semantics.

Repo: crates/coap-bridge/src/multicast.rs::{ALL_NODES_LINK_LOCAL_V4 ("224.0.1.187"), ALL_NODES_LINK_LOCAL_V6 ("FF02::FD"), ALL_NODES_SITE_LOCAL_V6 ("FF05::FD"), DEFAULT_LEISURE (5s), is_ipv4_multicast, is_ipv6_multicast, validate_multicast_request, leisure_delay, MulticastError} with spec-§8.1 NON-only validation + the §8.2 leisure-time helper.

Tests: multicast::tests::* (9 tests): ipv4_multicast_recognizes_class_d_range, ipv6_multicast_recognizes_ff_prefix, multicast_request_must_not_be_confirmable, multicast_request_must_have_token, valid_multicast_request_passes, leisure_delay_within_max, leisure_delay_zero_when_leisure_is_zero, well_known_addresses_match_spec, default_leisure_is_5_seconds.

Status: partial — multicast addresses, the NON-only check, the token requirement and the leisure time are built and checked; group join, sending and receiving in the daemon are missing (§8a).

§8a Multicast sending and receiving in the daemon

Spec: §8, pp. 74-77 — send and receive requests to an IP multicast group; a server answers after the leisure time.

Repo: —

Tests: —

Status: open — crates/coap-bridge/src/ joins no multicast group (no join_multicast_v4/join_multicast_v6); no socket path uses the helpers of multicast.rs.

RFC 7252 §9 Securing CoAP

§9 DTLS mode

Spec: §9, p. 77-86 — NoSec/PreSharedKey/RawPublicKey/Certificate modes.

Repo: crates/coap-bridge/src/dtls.rs::{DtlsMode, DtlsConfigError, validate_dtls_mode} with all four modes: - NoSec (default port 5683). - PreSharedKey { identity, key } (spec §9.1.1 — PSK ≥ 16 bytes recommended, identity required). - RawPublicKey { public_key, spki_der } (spec §9.1.2 — SubjectPublicKeyInfo DER-encoded). - Certificate { cert_chain, trust_anchors } (spec §9.1.3 — X.509 chain validation against trust anchors).

An is_secure() predicate + default_port() (5683/5684) + name() for logging. DTLS 1.2 transport in crates/coap-bridge/src/dtls_transport.rs (feature dtls, webrtc-dtls) with PSK and certificate.

Tests: crates/coap-bridge/src/dtls.rs::tests::{nosec_is_not_secure, psk_is_secure, raw_public_key_is_secure, certificate_is_secure, validate_psk_short_key_rejected, validate_psk_empty_identity_rejected, validate_psk_valid, validate_certificate_empty_chain_rejected, validate_certificate_no_trust_anchors_rejected, validate_raw_public_key_empty_rejected, validate_nosec_passes}; crates/coap-bridge/tests/dtls_coap_e2e.rs::{dtls_coap_get_content_roundtrip, dtls_psk_handshake_carries_coap, dtls_psk_unknown_identity_is_refused, dtls_certificate_files_and_rotation_keep_sessions_alive}; crates/coap-bridge/tests/daemon_dtls_e2e.rs::daemon_serves_coaps_over_dtls_request_response_and_observe.

Status: partial — NoSec, PreSharedKey and Certificate run over the DTLS transport; RawPublicKey exists only as configuration (§9a).

§9a RawPublicKey mode in the DTLS transport

Spec: §9, p. 68 (text version) — “The NoSec and RawPublicKey modes are mandatory to implement for this specification.”; §9.1.3.2 RawPublicKey (RFC 7250).

Repo: —

Tests: —

Status: open — crates/coap-bridge/src/dtls.rs knows DtlsMode::RawPublicKey as configuration; crates/coap-bridge/src/dtls_transport.rs negotiates only PSK and certificate (DtlsPeerIdentity::{Psk, Certificate}), a handshake with a raw public key (RFC 7250) is missing.

RFC 7252 §10-§13 Inter-op + security + IANA + acknowledgments

§10 HTTP cross-protocol mapping

Spec: §10, p. 86-91 — HTTP↔︎CoAP translation for proxy use cases. §10.1 status-code mapping (Tab 8); §10.2 method mapping (Tab 9).

Repo: crates/coap-bridge/src/caching_proxy.rs::{http_status_to_coap, coap_to_http_status, http_method_to_coap, coap_method_to_http} with spec-§10.1/§10.2-conformant mapping (200↔︎2.05, 404↔︎4.04, 500↔︎5.00, GET↔︎1, POST↔︎2, PUT↔︎3, DELETE↔︎4, etc.).

Tests: caching_proxy::tests::{http_200_maps_to_coap_2_05, http_404_maps_to_coap_4_04, http_500_maps_to_coap_5_00, http_unknown_returns_none, coap_to_http_round_trip, http_get_maps_to_coap_1, http_unknown_method_returns_none, coap_method_round_trip}.

Status: done — HTTP status and method mapping bidirectional.

§11.1 Parsing and URI processing

Spec: §11.1, p. 80 (RFC) — “the URI processing code in CoAP implementations […] should be implemented with special care. CoAP access control implementations need to ensure they don’t introduce vulnerabilities through discrepancies between the code deriving access control decisions from a URI and the code finally serving up the resource addressed by the URI.”

Repo: crates/coap-bridge/src/codec.rs (decode), crates/coap-bridge/src/uri.rs (parse_coap_uri).

Tests: crates/coap-bridge/tests/fuzz_smoke.rs::fuzz_coap_decode_no_panic, crates/coap-bridge/src/uri.rs::tests::rejects_fragment.

Status: partial — decoder robustness and URI decomposition are tested; no test checks that the access decision (topic ACL) and serving use the same decomposition of the URI.

§11.2 Cache: no delivery to requests with lesser transport security

Spec: §11.2, p. 81 (RFC) — “a caching proxy MUST NOT make cached values available to requests that have lesser transport-security properties than those the proxy would require to perform request forwarding in the first place.”

Repo: —

Tests: —

Status: open — CoapCache (crates/coap-bridge/src/caching_proxy.rs) stores and serves entries without regard to the transport security of the request.

§11.2 coaps responses not in a shared cache

Spec: §11.2, p. 81 (RFC) — “responses to”coaps” identified requests are never “public” and thus MUST NOT be reused for shared caching, unless the cache is able to make equivalent access control decisions to the ones that led to the cached entry.”

Repo: —

Tests: —

Status: open — CoapCache does not distinguish responses to coap and coaps requests.

§11.3 No large amplification without authentication

Spec: §11.3, p. 82 (RFC) — “large amplification factors SHOULD NOT be provided in the response if the request is not authenticated.”

Repo: —

Tests: —

Status: open — no code found that limits the response size for unauthenticated requests.

§11.3 Multicast requests only authenticated and only for specific resources

Spec: §11.3, p. 82 (RFC) — “CoAP servers SHOULD NOT accept multicast requests that can not be authenticated in some way […]. If possible, a CoAP server SHOULD limit the support for multicast requests to the specific resources where the feature is required.”

Repo: —

Tests: —

Status: open — the daemon (crates/coap-bridge/src/daemon/) does not distinguish multicast from unicast requests and restricts multicast neither to authenticated requests nor to resources.

§11.3 Detect the multicast destination via IPV6_RECVPKTINFO

Spec: §11.3, p. 82 (RFC) — “Implementations SHOULD make use of modern APIs such as IPV6_RECVPKTINFO [RFC3542], if available, to make this determination.”

Repo: —

Tests: —

Status: open — no code in crates/coap-bridge reads the destination address of a received packet.

§11.4, §11.5 IP spoofing and cross-protocol attacks

Spec: §11.4–§11.5, p. 83–86 (RFC) — threat analysis (forged Reset/ACK/responses, multicast spoofing, DNS replies read as CoAP messages).

Repo: —

Tests: —

Status: n/a (informative) — description of attacks without a requirement of its own; the countermeasure named (non-trivial, randomized token) is §5.3.1.

§11.6 Constrained-node considerations

Spec: §11.6, p. 86 (RFC) — “the node MUST NOT be used for processes that require good entropy, such as key generation. […] Special care must be taken in implementation of cryptographic primitives.”

Repo: —

Tests: —

Status: open — the OSCORE cryptography uses aes, ccm, hmac and sha2 from RustCrypto; no test checks constant-time behaviour. The bridge generates no keys.

§12.1, §12.2, §12.4–§12.7 IANA registrations

Spec: §12.1–§12.2, §12.4–§12.7, p. 86–97 (RFC) — instructions to IANA: code registries, option numbers registry, URI schemes coap and coaps, ports 5683 and 5684.

Repo: —

Tests: —

Status: n/a (informative) — registration instructions to IANA; the values themselves are items §5.8, §5.9, §5.10 and §6.

§12.3 CoAP Content-Formats registry

Spec: §12.3, p. 91–93 (RFC) — initial entries: text/plain; charset=utf-8 = 0, application/link-format = 40, application/xml = 41, application/octet-stream = 42, application/exi = 47, application/json = 50.

Repo: —

Tests: —

Status: open — crates/coap-bridge/src/daemon/server.rs sets 40 for application/link-format, without a test; there are no constants for the other entries.

§12.8 Multicast address registration

Spec: §12.8, p. 97 (RFC) — “All CoAP Nodes”: IPv4 224.0.1.187, IPv6 FF0X::FD; “CoAP needs the Link-Local and Site-Local scopes only.”

Repo: crates/coap-bridge/src/multicast.rs (ALL_NODES_LINK_LOCAL_V4, ALL_NODES_LINK_LOCAL_V6, ALL_NODES_SITE_LOCAL_V6).

Tests: crates/coap-bridge/src/multicast.rs::tests::well_known_addresses_match_spec.

Status: done

§13 Acknowledgements

Spec: §13, p. 97 (RFC) — acknowledgements.

Repo: —

Tests: —

Status: n/a (informative) — acknowledgements.

RFC 7641 §2 Observe option

§2 Observe option (number 6)

Spec: RFC 7641 §2, p. 4 — the Observe option (number 6) with values: 0 = register, 1 = deregister, 2-0xFFFFFF = sequence number.

Repo: crates/coap-bridge/src/option.rs::CoapOption::observe(value) + the numbers::OBSERVE constant.

Tests: option::tests::observe_option_uses_number_6, codec::tests::full_observe_request_encode_decode_round_trip.

Status: done

RFC 7641 §3-§5 Notification + state + reordering

Spec: RFC 7641 §3.1/§3.4/§3.6, p. 7-14 — registration via Observe = 0, a monotonically increasing sequence number modulo 2^24, and the reordering rule: a new notification (V2, T2) is fresher than the stored one (V1, T1) exactly when (V1 < V2 and V2 - V1 < 2^23) or (V1 > V2 and V1 - V2 > 2^23) or T2 > T1 + 128 seconds; §3.6 deregistration ends the observe relationship.

Repo: crates/coap-bridge/src/observe.rs::{ObserveRegistry, ObserverEntry} with register/deregister/observers_of/next_seq for notification sequencing per path; crates/coap-bridge/src/observe.rs::{notification_is_fresher, FRESHNESS_WINDOW_MS} for the §3.4 reordering rule.

Tests: crates/coap-bridge/src/observe.rs::tests::{register_then_observers_lists_one, next_seq_increments_per_observer, next_seq_wraps_at_24_bits, notifications_are_ordered_by_sequence_number_per_spec_3_4, wrapped_sequence_number_is_still_recognised_as_fresher, notification_older_than_the_freshness_window_is_always_accepted, deregister_ends_the_observe_relationship_per_spec_3_6}.

Status: done

Audit status

27 done / 5 partial / 10 open / 0 blocked / 4 n/a (informative).

Test run: cargo test -p zerodds-coap-bridge — 202 lib inline + 17 integration = 219 tests green, 0 failed, 3 ignored (interop tests against external libcoap binaries). Modules with tests: blockwise, bridge, caching_proxy, codec, core_link, daemon, dtls, matching, message, method_props, multicast, observe, option, oscore, reliability, uri.

Open items: coap-rfc-7252.open.en.md.

IETF CoAP RFC 7252 + RFC 7641 — Spec-Coverage

RFC 7252: The Constrained Application Protocol — IETF, June 2014 →

RFC 7641: Observing Resources in CoAP — IETF, September 2015 →

Kontext: CoAP ist eine RESTful-Spec für eingeschränkte Geräte. ZeroDDS implementiert sie in crates/coap-bridge/: Wire-Codec (Section 3, 5.10, RFC 7641 §2) als no_std+alloc-Library, dazu Reliability, Block-Wise Transfer (RFC 7959), Observe, einen DTLS-Transport (Feature dtls), OSCORE und den Daemon.

Implementation:

crates/coap-bridge/ · docs.rs — Codec, Transport-Bausteine und Daemon zerodds-coap-bridged.

RFC 7252 §1 Introduction

§1.1 Features

Spec: §1.1, S. 5 (RFC) — REST-Modell, UDP-Bound, Multicast-Support, DTLS-Security, Asynchron-Messaging.

Repo: crates/coap-bridge/src/lib.rs Crate-Doc.

Tests: REST-Methoden + Response-Klassen: crates/coap-bridge/src/message.rs::tests::well_known_codes_match_spec_values; Asynchron-Messaging (CON/NON/ACK/RST): crates/coap-bridge/src/message.rs::tests::message_type_round_trips_via_bits; Multicast-Support: crates/coap-bridge/src/multicast.rs::tests::well_known_addresses_match_spec; DTLS-Security: crates/coap-bridge/src/dtls.rs::tests::psk_is_secure; UDP-Bound (Default-Ports 5683/5684): crates/coap-bridge/src/uri.rs::tests::default_port_returns_5684_for_coaps.

Status: done — Übersicht; Multicast und DTLS stehen als eigene Items (§8, §9, §11).

§1.2 Terminology

Spec: §1.2, S. 6-9 — Endpoint, Sender, Recipient, Token, Origin Server, Cacheable, Resource, etc.

Repo: —

Tests: —

Status: n/a (informative) — Glossar; semantischer Bezugspunkt ohne Code-Mapping.

RFC 7252 §2 Constrained Application Protocol

§2.1 Messaging Model

Spec: §2.1, S. 11 — CON/NON/ACK/RST.

Repo: crates/coap-bridge/src/message.rs::MessageType.

Tests: message::tests::message_type_round_trips_via_bits.

Status: done

§2.2 Request/Response Model

Spec: §2.2, S. 12 — Method-Codes + Response-Codes.

Repo: crates/coap-bridge/src/message.rs::CoapCode mit Konstanten GET/POST/PUT/DELETE/CREATED/DELETED/VALID/CHANGED/CONTENT/BAD_REQUEST/ NOT_FOUND/INTERNAL_SERVER_ERROR.

Tests: message::tests::well_known_codes_match_spec_values, code_classification_predicates.

Status: done

§2.3 Intermediaries and Caching

Spec: §2.3, S. 15 — Forward-Proxies, Caches.

Repo: crates/coap-bridge/src/caching_proxy.rs::{CoapCache, CacheLookup, ProxyConfig, ProxyMode} — Cache-Layer mit Freshness-Tracking + Stale/Revalidate-Pfad; Proxy-Configuration mit Forward-/Reverse-Mode + Hop-Count-Cap (Spec §5.7.1 Loop-Schutz).

Status: done — Caching + Forward-Proxy-Configuration live.

§2.4 Resource Discovery

Spec: §2.4, S. 15 — .well-known/core (RFC 6690).

Repo: crates/coap-bridge/src/core_link.rs::{CoreLink, encode_links, decode_links}.

Status: done

RFC 7252 §3 Message Format

§3 Header-Format (Ver/T/TKL/Code/MID)

Spec: §3, S. 16 — 4-Byte-Fixed-Header. Version MUST be 1 (01 binary), TKL 0..=8 (9-15 reserved).

Repo: crates/coap-bridge/src/codec.rs::encode/decode setzt Version=1 beim Encode und rejected andere Versionen beim Decode.

Status: done

§3 Token

Spec: §3, S. 16 — Token 0..=8 Bytes nach Header.

Repo: crates/coap-bridge/src/message.rs::CoapMessage::token.

Tests: codec::tests::encode_decode_round_trip_preserves_header_fields, token_truncated_decode_fails.

Status: done

§3 Payload Marker

Spec: §3, S. 16-17 — 0xFF markiert Beginn des Payload. “The presence of a marker followed by a zero-length payload MUST be processed as a message format error.”

Repo: crates/coap-bridge/src/codec.rs (Encode + Decode).

Tests: codec::tests::payload_marker_separates_options_from_payload, payload_marker_without_payload_is_format_error.

Status: done

§3.1 Option Format (Delta-Encoding)

Spec: §3.1, S. 17-19 — 4-bit Delta-Nibble + 4-bit Length-Nibble + Extended-Forms (13/14) + Reserved (15). Options “MUST appear in order of their Option Numbers”.

Repo: crates/coap-bridge/src/codec.rs::encode_extended/ decode_extended. Encode sortiert Options vor Delta-Berechnung.

Status: done

§3.2 Option Value Formats

Spec: §3.2, S. 19-20 — empty, opaque, uint, string. uint “without leading zero bytes”; “MUST be prepared to process values with leading zero bytes”.

Repo: crates/coap-bridge/src/option.rs::OptionValue + uint_to_minimal_bytes + uint_from_bytes.

Status: done

RFC 7252 §4 Message Transmission

§4.1 Messages and Endpoints

Spec: §4.1, S. 20 — Endpoint-Identifikation via IP+Port.

Repo: crates/coap-bridge/src/bridge.rs (Endpoint als Vec<u8>-ID); UDP-Reactor lebt bewusst auf Caller-Schicht via crates/transport-udp/ — diese Trennung erlaubt no_std-Builds mit eigenem Transport (z.B. embedded-Stack ohne OS-Sockets). Spec §4.1 normiert die Endpoint-Identifikation, nicht den UDP- Reactor selbst.

Status: done — Endpoint-Tracking als spec-konforme Vec-ID; Transport-Decoupling ist beabsichtigte Architektur für no_std- Targets.

§4.2-§4.7 Reliability + Deduplication + Congestion

Spec: §4.2-§4.7, S. 21-26 — CON-Retry mit exponentiellem Backoff bis MAX_RETRANSMIT; §4.5 „The recipient […] SHOULD acknowledge each duplicate copy of a Confirmable message […] but SHOULD process any request or response in the message only once” — Message-ID-Duplikate innerhalb EXCHANGE_LIFETIME (CON) bzw. NON_LIFETIME (NON); §4.7 NSTART als Obergrenze gleichzeitig ausstehender Interaktionen gegenüber einem Server.

Repo: crates/coap-bridge/src/reliability.rs::{ReliabilityTracker, PendingConfirmable, TickOutput} — send_confirmable/receive_ack/ receive_rst/tick decken CON-Retry + ACK/RST-Pfad ab; crates/coap-bridge/src/reliability.rs::{DuplicateDetector, DedupKind, Reception} mit receive/remember_ack/evict_expired für die §4.5- Deduplikation (ACK aus dem Cache statt zweiter Verarbeitung); crates/coap-bridge/src/reliability.rs::OutstandingInteractions mit try_begin/end für die §4.7-NSTART-Schranke pro Server.

Status: done

§4.8 Transmission Parameters

Spec: §4.8, S. 27-29 — Tab. 2: ACK_TIMEOUT 2 s, ACK_RANDOM_FACTOR 1.5, MAX_RETRANSMIT 4, NSTART 1, DEFAULT_LEISURE 5 s, PROBING_RATE 1 Byte/s. §4.8.2 leitet daraus ab: MAX_TRANSMIT_SPAN = ACK_TIMEOUT * ((2 ** MAX_RETRANSMIT) - 1) * ACK_RANDOM_FACTOR (45 s), MAX_TRANSMIT_WAIT (93 s), EXCHANGE_LIFETIME = MAX_TRANSMIT_SPAN + (2 * MAX_LATENCY) + PROCESSING_DELAY (247 s), NON_LIFETIME (145 s).

Repo: crates/coap-bridge/src/reliability.rs::{ACK_TIMEOUT_MS, ACK_RANDOM_FACTOR_NUM, ACK_RANDOM_FACTOR_DEN, MAX_RETRANSMIT, NSTART, DEFAULT_LEISURE_MS, PROBING_RATE_BYTES_PER_SEC, MAX_LATENCY_MS, PROCESSING_DELAY_MS, MAX_TRANSMIT_SPAN_MS, MAX_TRANSMIT_WAIT_MS, EXCHANGE_LIFETIME_MS, NON_LIFETIME_MS}; initial_interval setzt ACK_TIMEOUT * ACK_RANDOM_FACTOR als erstes Retry-Intervall.

Tests: crates/coap-bridge/src/reliability.rs::tests::{transmission_parameters_match_spec_4_8_table_2, derived_transmission_parameters_follow_spec_4_8_2_formulas, backoff_schedule_follows_ack_timeout_and_random_factor} — der letzte prüft die daraus folgende Retry-Folge 3000/6000/12000/24000 ms und den Abbruch nach MAX_RETRANSMIT bei MAX_TRANSMIT_WAIT.

Status: done

RFC 7252 §5 Request/Response Semantics

§5.1 Requests

Spec: §5.1, S. 35-36 — Request-Definition: Method-Code (1-31), Token, Options, Payload.

Repo: Method-Codes 1=GET, 2=POST, 3=PUT, 4=DELETE als CoapCode-Varianten in crates/coap-bridge/src/message.rs.

Tests: message::tests::well_known_codes_match_spec_values.

Status: done

§5.2 Responses

Spec: §5.2, S. 36 — Response-Definition: Response-Code (2.xx Success, 4.xx Client-Error, 5.xx Server-Error), Echoed Token.

Repo: Response-Codes als CoapCode-Varianten (2.05 Content, 4.04 Not Found, 5.00 Internal Server Error etc.).

Tests: message::tests::well_known_codes_match_spec_values.

Status: done

§5.3 Request/Response Matching

Spec: §5.3, S. 37-39 — Token-basiertes Matching für Async- Replies (Piggybacked, Separate, Reset).

Repo: Token-Field im CoapMessage als Vec<u8> mit Längen- Constraint (TKL 0-8 Bytes) + crates/coap-bridge/src/matching.rs:: {PendingRequests, MatchError} mit submit/complete/ evict_expired und Spec-§4.8-EXCHANGE_LIFETIME-Support; DoS-Cap über max_pending.

Status: done — Token-Wire-Format + Pending-Request-Map mit Lifetime-Eviction live.

§5.4 Options

Spec: §5.4, S. 39-43 — Option-Class-Properties: Critical/Elective, Unsafe/Safe, NoCacheKey, Repeatable.

Repo: Option-Numbers in crates/coap-bridge/src/option.rs::numbers; Property-Bits aus der Option-Number in crates/coap-bridge/src/option.rs::{is_critical, is_unsafe, is_nocachekey, is_repeatable} nach der §5.4.6-Formel (Critical = (onum & 1), UnSafe = (onum & 2), NoCacheKey = ((onum & 0x1e) == 0x1c)) plus die gleichnamigen Methoden auf CoapOption.

Tests: crates/coap-bridge/src/option.rs::tests::{critical_unsafe_nocachekey_bits_per_spec_5_4_6, repeatable_options_match_spec_table_4, observe_option_uses_number_6}.

Status: done

§5.5 Payloads and Representations

Spec: §5.5.1/§5.5.3, S. 43-44 — Payload als Repräsentation, deren Medientyp die Content-Format-Option benennt; §5.5.2 „If no Content-Format option is given, the payload of responses indicating a client or server error is a brief human-readable diagnostic message” in UTF-8.

Repo: crates/coap-bridge/src/message.rs::CoapMessage::payload als Vec<u8>; Content-Format-Option (Number 12) über crates/coap-bridge/src/option.rs::CoapOption::content_format; Payload-Marker-Trennung in crates/coap-bridge/src/codec.rs.

Status: done

§5.6 Caching

Spec: §5.6, S. 44-46 — Freshness-Lifetime via Max-Age-Option; Validation via ETag-Option.

Repo: Max-Age (Number 14) + ETag (Number 4) Option-Numbers definiert; Cache-State-Logik in crates/coap-bridge/src/caching_proxy.rs::{CoapCache, CacheLookup, DEFAULT_MAX_AGE} mit store/lookup/evict_expired_without_etag, DoS-Cap-FIFO-Eviction und Spec-§5.6.1-Default-Max-Age (60s).

Status: done — Cache-State + Freshness + ETag-Validation-Pfad live.

§5.7 Proxying

Spec: §5.7, S. 46-49 — Proxy-Uri-Option, Forward-/Reverse-Proxy, HTTP-Mapping.

Repo: Proxy-Uri-Option (Number 35) definiert + Proxy-Logik in crates/coap-bridge/src/caching_proxy.rs::{ProxyConfig, ProxyMode} mit Forward/Reverse-Mode + max_hops-Cap (Spec §5.7.1 Loop-Schutz) + http_translation-Flag für §10-Pfad.

Tests: caching_proxy::tests::proxy_config_default_is_forward_coap_to_coap.

Status: partial — Proxy-Uri-Option, Forward-/Reverse-Modus und Hop-Grenze sind als Konfiguration gebaut; das Weiterleiten eines Requests fehlt (§5.7a).

§5.7a Weiterleiten durch einen Proxy

Spec: §5.7, S. 46-49 — ein Forward-Proxy führt den Request mit der Ziel-URI aus Proxy-Uri aus, ein Reverse-Proxy bildet ihn auf einen Ursprungs-Server ab, und beide liefern die Response zurück.

Repo: —

Tests: —

Status: open — crates/coap-bridge/src/caching_proxy.rs hält nur ProxyConfig/ProxyMode; kein Pfad sendet einen Request an das Ziel weiter.

§5.8 Method Definitions

Spec: §5.8, S. 49-51 — GET/POST/PUT/DELETE-Semantik, Idempotency.

Repo: Method-Codes definiert in crates/coap-bridge/src/message.rs + Method-Property- Helpers crates/coap-bridge/src/method_props.rs::{is_safe, is_idempotent, is_method} mit Spec-konformen Werten (GET = safe + idempotent; PUT/DELETE = idempotent; POST = weder).

Tests: method_props::tests::{get_is_safe, post_put_delete_not_safe, get_put_delete_idempotent, post_not_idempotent, method_predicate_recognizes_all_four}.

Status: done — Codes + Method-Properties (Safety + Idempotency) ausgewiesen.

§5.9 Response Code Definitions

Spec: §5.9, S. 52-58 — vollständige Liste aller Response-Codes (2.xx, 4.xx, 5.xx) mit Bedeutung.

Repo: Alle wichtigen Codes als CoapCode-Varianten in crates/coap-bridge/src/message.rs.

Tests: message::tests::well_known_codes_match_spec_values.

Status: done

§5.10 Option Definitions

Spec: §5.10, S. 53-67 — Number-Registry: Uri-Host (3), ETag (4), If-None-Match (5), Uri-Port (7), Location-Path (8), Uri-Path (11), Content-Format (12), Max-Age (14), Uri-Query (15), Accept (17), Location-Query (20), Proxy-Uri (35), Proxy-Scheme (39), Size1 (60). Plus If-Match (1).

Repo: crates/coap-bridge/src/option.rs::numbers mit allen Konstanten + Convenience-Konstruktoren uri_path/content_format.

Tests: option::tests::option_uri_path_constructs_string_value, content_format_uses_number_12, codec::tests::full_observe_request_encode_decode_round_trip.

Status: done

RFC 7252 §6 CoAP URIs

§6.1-§6.5 CoAP-URI-Scheme

Spec: §6, S. 67-72 — coap:// + coaps:// URI-Schemen.

Repo: crates/coap-bridge/src/uri.rs::{parse_coap_uri, CoapUri, default_port, UriError}. Default-Ports 5683 / 5684; Path-Segmente + Query-Parameter werden aufgeteilt (zur direkten Mapping in Uri-Path/Uri-Query-Options); Fragment-Identifier rejected (§6.1).

Status: done — coap/coaps URI-Scheme-Parser live.

RFC 7252 §7 Discovery

§7.1-§7.2 Service + Resource Discovery

Spec: §7, S. 73-74 — Multicast-Discovery + .well-known/core.

Repo: Resource-Discovery via crates/coap-bridge/src/core_link.rs; Service-Discovery via Multicast in multicast.rs::{ALL_NODES_LINK_LOCAL_V4, ALL_NODES_LINK_LOCAL_V6, ALL_NODES_SITE_LOCAL_V6, validate_multicast_request} (siehe §8).

Tests: Resource-Discovery: crates/coap-bridge/src/core_link.rs::tests::{encode_simple_link_format, decode_round_trip_with_attrs}; Service-Discovery: crates/coap-bridge/src/multicast.rs::tests::{well_known_addresses_match_spec, valid_multicast_request_passes, multicast_request_must_not_be_confirmable}.

Status: partial — Resource-Discovery über /.well-known/core und die Multicast-Adressen sind gebaut und geprüft; Service-Discovery per Multicast braucht den Multicast-Empfang aus §8a.

RFC 7252 §8 Multicast CoAP

§8 Multicast Operation

Spec: §8, S. 74-77 — IP-Multicast-Semantik.

Repo: crates/coap-bridge/src/multicast.rs::{ALL_NODES_LINK_LOCAL_V4 ("224.0.1.187"), ALL_NODES_LINK_LOCAL_V6 ("FF02::FD"), ALL_NODES_SITE_LOCAL_V6 ("FF05::FD"), DEFAULT_LEISURE (5s), is_ipv4_multicast, is_ipv6_multicast, validate_multicast_request, leisure_delay, MulticastError} mit Spec-§8.1-konformer NON-only- Validation + §8.2 Leisure-Time-Helper.

Tests: multicast::tests::* (9 Tests): ipv4_multicast_recognizes_class_d_range, ipv6_multicast_recognizes_ff_prefix, multicast_request_must_not_be_confirmable, multicast_request_must_have_token, valid_multicast_request_passes, leisure_delay_within_max, leisure_delay_zero_when_leisure_is_zero, well_known_addresses_match_spec, default_leisure_is_5_seconds.

Status: partial — Multicast-Adressen, NON-only-Prüfung, Token-Pflicht und Leisure-Zeit sind gebaut und geprüft; Gruppenbeitritt, Senden und Empfangen im Daemon fehlen (§8a).

§8a Multicast-Versand und -Empfang im Daemon

Spec: §8, S. 74-77 — Requests an eine IP-Multicast-Gruppe senden und empfangen; ein Server antwortet nach der Leisure-Zeit.

Repo: —

Tests: —

Status: open — crates/coap-bridge/src/ tritt keiner Multicast-Gruppe bei (kein join_multicast_v4/join_multicast_v6); die Helfer aus multicast.rs werden von keinem Socket-Pfad benutzt.

RFC 7252 §9 Securing CoAP

§9 DTLS Mode

Spec: §9, S. 77-86 — NoSec/PreSharedKey/RawPublicKey/Certificate- Modi.

Repo: crates/coap-bridge/src/dtls.rs::{DtlsMode, DtlsConfigError, validate_dtls_mode} mit allen vier Modi: - NoSec (Default-Port 5683). - PreSharedKey { identity, key } (Spec §9.1.1 — PSK ≥ 16 bytes empfohlen, identity required). - RawPublicKey { public_key, spki_der } (Spec §9.1.2 — SubjectPublicKeyInfo DER-encoded). - Certificate { cert_chain, trust_anchors } (Spec §9.1.3 — X.509-Chain-Validation gegen Trust-Anchors).

is_secure()-Predicate + default_port() (5683/5684) + name() für Logging. DTLS-1.2-Transport in crates/coap-bridge/src/dtls_transport.rs (Feature dtls, webrtc-dtls) mit PSK und Zertifikat.

Status: partial — NoSec, PreSharedKey und Certificate laufen über den DTLS-Transport; RawPublicKey ist nur als Konfiguration vorhanden (§9a).

§9a RawPublicKey-Modus im DTLS-Transport

Spec: §9, S. 68 (Textfassung) — „The NoSec and RawPublicKey modes are mandatory to implement for this specification.“; §9.1.3.2 RawPublicKey (RFC 7250).

Repo: —

Tests: —

Status: open — crates/coap-bridge/src/dtls.rs kennt DtlsMode::RawPublicKey als Konfiguration; crates/coap-bridge/src/dtls_transport.rs handelt nur PSK und Zertifikat aus (DtlsPeerIdentity::{Psk, Certificate}), ein Handshake mit Raw Public Key (RFC 7250) fehlt.

RFC 7252 §10-§13 Inter-Op + Security + IANA + Acknowledgments

§10 HTTP Cross-Proto-Mapping

Spec: §10, S. 86-91 — HTTP↔︎CoAP-Translation für Proxy-Use-Cases. §10.1 Status-Code-Mapping (Tab 8); §10.2 Method-Mapping (Tab 9).

Repo: crates/coap-bridge/src/caching_proxy.rs::{http_status_to_coap, coap_to_http_status, http_method_to_coap, coap_method_to_http} mit Spec-§10.1/§10.2-konformem Mapping (200↔︎2.05, 404↔︎4.04, 500↔︎5.00, GET↔︎1, POST↔︎2, PUT↔︎3, DELETE↔︎4 etc.).

Status: done — HTTP-Status- und Method-Mapping bidirektional.

§11.1 Parsing und URI-Verarbeitung

Spec: §11.1, S. 80 (RFC) — “the URI processing code in CoAP implementations […] should be implemented with special care. CoAP access control implementations need to ensure they don’t introduce vulnerabilities through discrepancies between the code deriving access control decisions from a URI and the code finally serving up the resource addressed by the URI.”

Repo: crates/coap-bridge/src/codec.rs (decode), crates/coap-bridge/src/uri.rs (parse_coap_uri).

Tests: crates/coap-bridge/tests/fuzz_smoke.rs::fuzz_coap_decode_no_panic, crates/coap-bridge/src/uri.rs::tests::rejects_fragment.

Status: partial — Robustheit des Decoders und die URI-Zerlegung sind getestet; kein Test prüft, dass Zugriffsentscheidung (Topic-ACL) und Auslieferung dieselbe Zerlegung der URI verwenden.

§11.2 Cache: keine Auslieferung an Anfragen mit geringerer Transportsicherheit

Spec: §11.2, S. 81 (RFC) — “a caching proxy MUST NOT make cached values available to requests that have lesser transport-security properties than those the proxy would require to perform request forwarding in the first place.”

Repo: —

Tests: —

Status: open — CoapCache (crates/coap-bridge/src/caching_proxy.rs) speichert und liefert Einträge ohne Bezug auf die Transportsicherheit der Anfrage.

§11.2 coaps-Antworten nicht im geteilten Cache

Spec: §11.2, S. 81 (RFC) — “responses to”coaps” identified requests are never “public” and thus MUST NOT be reused for shared caching, unless the cache is able to make equivalent access control decisions to the ones that led to the cached entry.”

Repo: —

Tests: —

Status: open — CoapCache unterscheidet nicht zwischen Antworten auf coap- und coaps-Anfragen.

§11.3 Keine große Verstärkung ohne Authentifizierung

Spec: §11.3, S. 82 (RFC) — “large amplification factors SHOULD NOT be provided in the response if the request is not authenticated.”

Repo: —

Tests: —

Status: open — kein Code gefunden, der die Antwortgröße für nicht authentifizierte Anfragen begrenzt.

§11.3 Multicast-Anfragen nur authentifiziert und nur für bestimmte Ressourcen

Spec: §11.3, S. 82 (RFC) — “CoAP servers SHOULD NOT accept multicast requests that can not be authenticated in some way […]. If possible, a CoAP server SHOULD limit the support for multicast requests to the specific resources where the feature is required.”

Repo: —

Tests: —

Status: open — der Daemon (crates/coap-bridge/src/daemon/) unterscheidet Multicast- und Unicast-Anfragen nicht und schränkt Multicast weder auf authentifizierte Anfragen noch auf Ressourcen ein.

§11.3 Multicast-Ziel über IPV6_RECVPKTINFO erkennen

Spec: §11.3, S. 82 (RFC) — “Implementations SHOULD make use of modern APIs such as IPV6_RECVPKTINFO [RFC3542], if available, to make this determination.”

Repo: —

Tests: —

Status: open — kein Code in crates/coap-bridge liest die Zieladresse eines empfangenen Pakets.

§11.4, §11.5 IP-Spoofing und Cross-Protocol-Angriffe

Spec: §11.4–§11.5, S. 83–86 (RFC) — Bedrohungsanalyse (gefälschte Reset/ACK/Antworten, Multicast-Spoofing, DNS-Antworten als CoAP-Nachricht).

Repo: —

Tests: —

Status: n/a (informative) — Beschreibung von Angriffen ohne eigene Anforderung; die genannte Gegenmaßnahme (nicht triviales, zufälliges Token) ist §5.3.1.

§11.6 Constrained-Node Considerations

Spec: §11.6, S. 86 (RFC) — “the node MUST NOT be used for processes that require good entropy, such as key generation. […] Special care must be taken in implementation of cryptographic primitives.”

Repo: —

Tests: —

Status: open — die OSCORE-Kryptografie verwendet aes, ccm, hmac und sha2 aus RustCrypto; kein Test prüft die Laufzeitkonstanz. Die Bridge erzeugt keine Schlüssel.

§12.1, §12.2, §12.4–§12.7 IANA-Registrierungen

Spec: §12.1–§12.2, §12.4–§12.7, S. 86–97 (RFC) — Anweisungen an die IANA: Code-Registries, Option-Numbers-Registry, URI-Schemes coap und coaps, Ports 5683 und 5684.

Repo: —

Tests: —

Status: n/a (informative) — Registrierungsanweisungen an die IANA; die Werte selbst sind als Items §5.8, §5.9, §5.10 und §6 geführt.

§12.3 CoAP Content-Formats Registry

Spec: §12.3, S. 91–93 (RFC) — Anfangseinträge: text/plain; charset=utf-8 = 0, application/link-format = 40, application/xml = 41, application/octet-stream = 42, application/exi = 47, application/json = 50.

Repo: —

Tests: —

Status: open — crates/coap-bridge/src/daemon/server.rs setzt 40 für application/link-format, ohne Test; für die übrigen Einträge gibt es keine Konstanten.

§12.8 Multicast Address Registration

Spec: §12.8, S. 97 (RFC) — “All CoAP Nodes”: IPv4 224.0.1.187, IPv6 FF0X::FD; “CoAP needs the Link-Local and Site-Local scopes only.”

Repo: crates/coap-bridge/src/multicast.rs (ALL_NODES_LINK_LOCAL_V4, ALL_NODES_LINK_LOCAL_V6, ALL_NODES_SITE_LOCAL_V6).

Tests: crates/coap-bridge/src/multicast.rs::tests::well_known_addresses_match_spec.

Status: done

§13 Acknowledgements

Spec: §13, S. 97 (RFC) — Danksagung.

Repo: —

Tests: —

Status: n/a (informative) — Danksagung.

RFC 7641 §2 Observe Option

§2 Observe Option (Number 6)

Spec: RFC 7641 §2, S. 4 — Observe-Option (Number 6) mit Werten: 0 = register, 1 = deregister, 2-0xFFFFFF = sequence number.

Repo: crates/coap-bridge/src/option.rs::CoapOption::observe(value) + numbers::OBSERVE Konstante.

Tests: option::tests::observe_option_uses_number_6, codec::tests::full_observe_request_encode_decode_round_trip.

Status: done

RFC 7641 §3-§5 Notification + State + Reordering

Spec: RFC 7641 §3.1/§3.4/§3.6, S. 7-14 — Registrierung über Observe = 0, monoton steigende Sequenznummer modulo 2^24, und die Reordering-Regel: eine neue Notification (V2, T2) ist frischer als die gespeicherte (V1, T1) genau dann, wenn (V1 < V2 and V2 - V1 < 2^23) oder (V1 > V2 and V1 - V2 > 2^23) oder T2 > T1 + 128 seconds; §3.6 Deregistrierung beendet die Observe-Beziehung.

Repo: crates/coap-bridge/src/observe.rs::{ObserveRegistry, ObserverEntry} mit register/deregister/observers_of/next_seq für Notification-Sequencing pro Path; crates/coap-bridge/src/observe.rs::{notification_is_fresher, FRESHNESS_WINDOW_MS} für die §3.4-Reordering-Regel.

Status: done

Audit-Status

27 done / 5 partial / 10 open / 0 blocked / 4 n/a (informative).

Test-Lauf: cargo test -p zerodds-coap-bridge — 202 lib-Inline + 17 Integration = 219 Tests grün, 0 failed, 3 ignored (Interop-Tests gegen externe libcoap-Binaries). Module mit Tests: blockwise, bridge, caching_proxy, codec, core_link, daemon, dtls, matching, message, method_props, multicast, observe, option, oscore, reliability, uri.

Offene Punkte: coap-rfc-7252.open.md.