HW-only keys#409
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Pull request overview
This PR adds an optional “hardware keystore” front-end (WOLFHSM_CFG_HWKEYSTORE) and introduces a new hardware-only keyId signaling flag, allowing clients to reference hardware-resident KEKs for keywrap operations while ensuring the key material is never cached, persisted, or exported.
Changes:
- Adds the
wh_HwKeystore_*module (callback + optional lock) and wires it intowhServerContext/whServerConfigwhen enabled. - Extends keyId encoding/translation to support hardware-only keys (
WH_KEYID_CLIENT_HW_FLAG↔WH_KEYTYPE_HW) and updates server keystore policy to reject HW-only ids for all non-keywrap keystore operations. - Updates keywrap KEK resolution to fetch HW-only KEKs from the hardware keystore into a local buffer (with zeroization), and adds/refactors tests + documentation for the feature.
Reviewed changes
Copilot reviewed 19 out of 19 changed files in this pull request and generated 4 comments.
Show a summary per file
| File | Description |
|---|---|
wolfhsm/wh_settings.h |
Adds HW keystore config macros and default max HW key size. |
wolfhsm/wh_server.h |
Adds optional hwKeystore pointer in server config/context behind WOLFHSM_CFG_HWKEYSTORE. |
wolfhsm/wh_keyid.h |
Introduces HW-only client flag, WH_KEYTYPE_HW, and related helpers/docs. |
wolfhsm/wh_hwkeystore.h |
New public header defining the HW keystore front-end API and types. |
wolfhsm/wh_client.h |
Documents async DataWrap/DataUnwrap request/response APIs and adds WH_CLIENT_KEYID_MAKE_HW(). |
src/wh_server.c |
Plumbs hwKeystore from whServerConfig into whServerContext. |
src/wh_server_keystore.c |
Enforces HW-only keystore rejections and adds keywrap KEK resolution that can fetch HW KEKs. |
src/wh_keyid.c |
Implements HW-only flag ↔ type translation in keyId conversion helpers. |
src/wh_hwkeystore.c |
New implementation of the HW keystore front-end (validation + optional locking). |
test/config/wolfhsm_cfg.h |
Enables WOLFHSM_CFG_HWKEYSTORE in the legacy test configuration. |
test/wh_test_keywrap.h |
Adds declarations for HW keystore test callback/test case. |
test/wh_test_keywrap.c |
Adds legacy keywrap-focused HW-only KEK tests and a test backend callback. |
test/wh_test_crypto.c |
Binds the HW keystore into the in-process server config for relevant test paths. |
test-refactor/config/wolfhsm_cfg.h |
Enables WOLFHSM_CFG_HWKEYSTORE in refactor test configuration. |
test-refactor/wh_test_list.c |
Registers new HW keystore tests in misc/server groups. |
test-refactor/server/wh_test_hwkeystore_server.c |
New server-side unit tests for HW keystore module + keystore rejection behavior. |
test-refactor/misc/wh_test_hwkeystore.c |
New end-to-end HW-only KEK keywrap/datawrap tests using a private mem-transport client/server pair. |
docs/src/9-Configuration.md |
Documents new HW keystore configuration macros. |
docs/src/5-Features.md |
Adds a “Hardware-Only Keys” feature section describing behavior and constraints. |
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Fenrir Automated Review — PR #409
Scan targets checked: wolfhsm-core-bugs, wolfhsm-crypto-bugs, wolfhsm-src
No new issues found in the changed files. ✅
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Fenrir Automated Review — PR #409
Scan targets checked: wolfhsm-core-bugs, wolfhsm-crypto-bugs, wolfhsm-src
No new issues found in the changed files. ✅
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Adds extremely basic support for hardware-only keys. Keys are tagged as hardware-only by the client through the upper keyId flag bits, just like global or wrapped keys. On the server-side the abstraction is the start of a shim layer with configurable backend supporting various operations -- currently just a "get key" operation.
The only server component that currently can use hardware-only keys is the keywrap module. Others could be brought online in the future.
Notably, this PR deliberately does NOT integrate caching hardware keys into the keycache, and therefore does not require adding a new keytype (yet). This means HW keys only exist transiently and there does not yet need to be any management/lifecycle/eviction.
Support for HW crypto with HW keys is therefore delegated to the platform-specific server-side crypto callbacks, since there is no "generic" way to handle this. The port's cryptoCb has direct access to the keyId and so can determine if it is a HW only keyId and can act appropriately.