ci: add GitHub Actions test pipeline

[Frauschi]

ci: add GitHub Actions test pipeline

Summary

Adds a full GitHub Actions CI pipeline for wolfCert, plus the supporting scripts and a couple of adjacent fixes surfaced while building it out. CI builds (or restores from cache) a named wolfSSL configuration, builds wolfCert to match, and runs the tests. The design splits work into a fast per-PR merge gate and a nightly job set that owns the heavier matrix, cache seeding, sanitizers, and interop.

Workflows

Workflow	Trigger	What it does
pr.yml	PR + push to main/master	Merge gate: canonical config on CMake (-Werror), autoconf, and ASan/UBSan, plus per-PR feature/config gating — EST-only, SCEP-only, server-off, key-alg variants (NO_RSA, ECC-only, RSA-only, no-3DES), TLS 1.3-only, ML-DSA per-level, static-mem, no-malloc, the header-only user_settings.h build, a macOS build, and the two cheapest configure-must-fail assertions.
lint.yml	PR + push	GPL license-header check and CMake↔autoconf parity of both the library and test source lists. No wolfSSL build — fails in seconds.
nightly.yml	schedule + dispatch	Re-runs the wolfSSL-variant matrix against fresh wolfSSL master, seeds the wolfSSL prefix caches so next-day PRs restore instead of build, and runs the macOS extras + full negative-config set.
sanitizers.yml	schedule + dispatch	ASan/UBSan over the full suite, TSan over the threaded roundtrips, valgrind over a representative subset.
interop.yml	schedule + dispatch	Third-party EST/SCEP interop (openssl, micromdm/scep, globalsign/est, cisco/libest, smallstep/step-ca). Best-effort: a dependency that fails to install exits 77 (neutral skip); a real regression fails.

Key design decisions

• PR gate vs nightly split. Feature-gating and build-config variants run on every PR so #ifdef/feature-flag breakage is caught before merge, not after. Nightly keeps the same variant matrix to (a) seed the caches and (b) retest against a fresh wolfSSL master, and owns the slow work (sanitizers, interop, macOS extras, full negative-config set).
• Caching strategy. scripts/ci/build-wolfssl.sh is the single source of truth mapping a config name → wolfSSL ./configure flags. The build-wolfssl composite action caches the install prefix, keyed on the resolved wolfSSL commit + a hash of the exact flags. Nightly owns the shared caches (save: true); PR and interop jobs are restore-only (save: false) so concurrent scheduled jobs never race to save the same key. Footprint is ~5–8 MB/entry, ~0.1 GB steady-state (worst case ~0.6 GB), well under GitHub's self-evicting 10 GB-per-repo cache.
• No source changes for CI plumbing. SIGPIPE from a benign socket teardown race is handled by sigpipe-launcher.sh (CMake, via CMAKE_CROSSCOMPILING_EMULATOR) and a trap '' PIPE shell (autoconf) — neither touches library or test source.
• macOS is bash 3.2. Every step that can run on macos-* stays bash-3.2-clean (no mapfile, guarded empty-array expansion).

Build-system parity (make check == ctest)

• Registered the 6 EST integration tests Makefile.am was missing, so the autoconf make check and CMake ctest now run the identical test set.
• Extended check-buildsystem-parity.sh to machine-enforce test-source parity in addition to library sources — a test added to one build system but not the other now fails lint.yml in seconds.

Code change (not CI): CSR-attribute enforcement

src/est/est_server.c — refactor + hardening of the est_require_csr_attributes enforcement path:

• Collapsed csr_attrs_enforce's err_oid_cap / err_oid_len out-parameters into a single value-result size_t* (capacity in, length out), matching wolfCrypt's word32* outLen convention.
• Hardening: the out-length is reset to 0 on every non-missing path and the caller gates on it, so no current or future error path can render an unpopulated stack buffer into the client-visible HTTP 400 body.
• Added an end-to-end test asserting the 400 response body names the exact missing OID (1.2.840.113549.1.9.7), covering the OID copy that the client-path test can't observe.

Testing

Reproduce a CI job locally:

# Build the wolfSSL config the job uses.
scripts/ci/build-wolfssl.sh full --prefix /tmp/wolfssl

# Build wolfCert against it and run the tests (CMake).
cmake -S . -B build -DWITH_WOLFSSL=/tmp/wolfssl -DWOLFCERT_ENABLE_TESTS=ON
cmake --build build -j
ctest --test-dir build --output-on-failure

# autoconf equivalent
./autogen.sh
PKG_CONFIG_PATH=/tmp/wolfssl/lib/pkgconfig ./configure \
    --with-wolfssl=/tmp/wolfssl --enable-tests
make -j && make check

• All 18 EST/CSR/SCEP unit + integration tests pass locally against the canonical full config.
• A skoll code review of the diff is clean at the Medium+ confidence threshold; the findings it surfaced (interop cache-save race, the CSR-attr enforcement hardening, the missing OID-body assertion) are addressed here.

Notes

• wolfSSL is tracked at master, unpinned (per project decision).
• docs/CI.md documents the pipeline, the config names, and how to reproduce and debug a job locally.

[Frauschi]

Closing in favor of #6 to make sure the new CI tests run in the PR ahead of merging