feat: add optional digital signature verification for HDF5 filter plugins
Introduce an opt-in plugin signing and verification system that allows
HDF5 deployments to require cryptographically signed filter plugins before
loading them. Disabled by default (HDF5_REQUIRE_SIGNED_PLUGINS=OFF).
New tool: h5sign
- Signs plugin shared libraries by appending an RSA signature and a
14-byte footer (algo_id | sig_len | 8-byte magic | format_ver) to the
binary without modifying the original content.
- Supports SHA-512 (default), SHA-256, SHA-384, and their PSS variants
(-a/--algorithm flag).
- Detects already-signed plugins; --force strips the old signature and
re-signs.
- Security hardened: keeps the file descriptor open through hashing and
appending (no TOCTOU window), enforces a 2048-bit minimum RSA key size,
rolls back partial writes on failure, and rejects paths that are not
regular files.
Verification (H5PLsig.c)
- At plugin load time, reads the footer, validates the magic and format
version, then checks the RSA signature against all public keys found in
the KeyStore directory.
- File is hashed once; per-key verification operates on the pre-computed
digest (no redundant I/O for multi-key keystores).
- Plugins whose signature hash appears in revoked_signatures.txt are
rejected regardless of key validity.
- Runtime debug output via HDF5_DEBUG=pl.
KeyStore management
- Trusted public keys are PEM files in a directory specified by
HDF5_PLUGIN_KEYSTORE_DIR (build time) or HDF5_PLUGIN_KEYSTORE (env var).
- HDF5_LOCK_PLUGIN_KEYSTORE cmake option disables the env-var override for
security-hardened deployments.
Test infrastructure
- h5signverifytest: positive, negative, tamper, re-sign, and revocation
test cases.
- CTest fixture-based dependency graph (FIXTURES_SETUP/FIXTURES_REQUIRED)
replaces fragile DEPENDS chains so tests remain correct under -R filtering.
- Dedicated signed-plugins.yml CI workflow; full test suite scoped to
H5SIGN and H5PLUGIN-signature tests to avoid unrelated flaky failures.
- Cross-platform: Linux, macOS, and Windows (MSVC-compatible, BIO-based
OpenSSL I/O, HDsleep/HDsetenv portability wrappers).
Documentation: docs/PLUGIN_SIGNATURE_README.md covers usage, footer
format, revocation file format, FAQ, and troubleshooting.
Co-authored-by: Glenn Song <gsong@hdfgroup.org>
Co-authored-by: github-actions <41898282+github-actions[bot]@users.noreply.github.com>
