COSE HPKE Support

[aidangarske]

• Adds default off COSE HPKE P0 support for Encrypt0 and multi recipient Encrypt
• Requires WOLFCOSE_EXPERIMENTAL plus each selected HPKE operation macro
• Keeps WOLFCOSE_EXPERIMENTAL alone free of feature code
• Adds paired CLI commands self tests and an HPKE P0 example
• Covers all six HPKE enable selectors with negative acknowledgement tests
• Updates HPKE CI to use the experimental acknowledgement
• Adds experimental feature status scope and graduation documentation
• Validation passed make experimental-check and HPKE example runs
• Full HPKE CLI validation passed 44 tests with 0 failures

#4

[Copilot]

🔵 Needs a closer look

It introduces new cryptographic message parsing and key-management paths for attacker-controlled inputs, warranting final human security review despite strong gating and test additions.

Pull request overview

Adds experimental (opt-in) COSE-HPKE P0 support to wolfCOSE, including integrated Encrypt0 HPKE-0 and multi-recipient Encrypt HPKE-0-KE, with build-time acknowledgement gating and supporting tool/test/docs/CI coverage.

Changes:

• Introduces HPKE-0 integrated Encrypt0 encrypt/decrypt APIs and HPKE-0-KE recipient key-encryption support inside wc_CoseEncrypt_{Encrypt,Decrypt}.
• Extends wolfcose_tool with HPKE keygen/export and HPKE encrypt/decrypt commands, plus CLI self-tests and negative-path hardening for key output paths (POSIX).
• Adds an HPKE example program, dedicated experimental HPKE CI workflow, and documentation for build/validation and experimental feature status.

File summaries

File	Description
tools/wolfcose_tool.c	Adds HPKE CLI commands, HPKE keygen with guarded output handling, and HPKE round-trip self-tests.
src/wolfcose.c	Implements HPKE P0 primitives, HPKE header parsing support, and HPKE-0/HPKE-0-KE encryption/decryption logic.
scripts/cmdline-test.sh	Adds opt-in HPKE CLI coverage and negative-path tests gated by EXPECT_HPKE.
Makefile	Adds hpke demo target, HPKE-aware experimental gates, and strict C99 HPKE compilation lane.
include/wolfcose/wolfcose.h	Publishes draft HPKE constants and integrated Encrypt0 HPKE API declarations.
include/wolfcose/settings.h	Adds experimental acknowledgement + fine-grained HPKE enable/disable macros and backend requirements.
examples/hpke_demo.c	New example demonstrating HPKE-0 Encrypt0 and HPKE-0-KE multi-recipient Encrypt flows.
docs/Testing.md	Documents opt-in HPKE test/build workflow and coverage expectations.
docs/Macros.md	Documents COSE-HPKE experimental gates and links to experimental status page.
docs/Home.md	Adds navigation entry for Experimental features.
docs/Getting-Started.md	Adds HPKE backend prerequisites and quickstart usage for HPKE demo/tool.
docs/Experimental.md	New page tracking experimental feature status, draft versioning, and graduation plan.
docs/_Sidebar.md	Adds Experimental page to docs sidebar.
.github/workflows/cose-hpke.yml	New CI workflow validating HPKE unit tests, example, strict C99 lane, and CLI commands.

Review details

• Files reviewed: 15/15 changed files
• Comments generated: 1
• Review effort level: Lite

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