Fix ML-DSA key cache size check for verify-only builds

[miyazakh]

Summary

When WOLFSSL_DILITHIUM_VERIFY_ONLY is defined, the server only needs to
cache the public key DER, not the full keypair. The previous static assert
unconditionally required the cache buffer to fit a full keypair DER, causing
unnecessary failures in verify-only configurations.

This change introduces WH_SERVER_MLDSA_MAX_CACHE_DER_SIZE to select the
correct maximum size at compile time:

• WOLFSSL_DILITHIUM_VERIFY_ONLY defined: MLDSA_MAX_PUB_KEY_DER_SIZE
• Otherwise: MLDSA_MAX_BOTH_KEY_DER_SIZE

The static assert is updated to use this macro so it reflects the actual
requirement for each build configuration.

Testing

• Build with and without WOLFSSL_DILITHIUM_VERIFY_ONLY and confirm the
  static assert passes in both cases.

[Copilot]

Pull request overview

Fixes an ML-DSA server key-cache sizing check to accommodate WOLFSSL_DILITHIUM_VERIFY_ONLY builds where only the public key DER needs to be cached, avoiding unnecessary compile-time failures in verify-only configurations.

Changes:

• Adds a configuration-dependent ML-DSA maximum cache DER size selection in wh_server_crypto.c.
• Updates the key-cache static assert logic for verify-only vs full-keypair builds.

Comments suppressed due to low confidence (1)

src/wh_server_crypto.c:787

• In WOLFSSL_DILITHIUM_VERIFY_ONLY builds the static assert now allows WOLFHSM_CFG_SERVER_KEYCACHE_BIG_BUFSIZE to be sized for only the public-key DER, but wh_Server_MlDsaKeyCacheImport() still hard-codes MLDSA_MAX_BOTH_KEY_DER_SIZE when acquiring a cache slot and serializing. That can make verify-only builds pass the compile-time check but fail key cache import at runtime due to the larger requested size. Use WH_SERVER_MLDSA_MAX_CACHE_DER_SIZE for the cache-slot check and serialization sizing.

#endif

int wh_Server_MlDsaKeyCacheImport(whServerContext* ctx, wc_MlDsaKey* key,
                                  whKeyId keyId, whNvmFlags flags,
                                  uint16_t label_len, uint8_t* label)

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[padelsbach]

Looks good, but can you please add simple test cases to build-and-test.yml and build-and-test-refactor.yml

[wolfSSL-Fenrir-bot]

Fenrir Automated Review — PR #452

Scan targets checked: wolfhsm-crypto-bugs, wolfhsm-src
Findings: 1

Medium (1)

wh_Server_MlDsaKeyCacheImport hardcodes MLDSA_MAX_BOTH_KEY_DER_SIZE after static assert is relaxed

File: src/wh_server_crypto.c:800
Function: wh_Server_MlDsaKeyCacheImport
Category: Logic errors

wh_Server_MlDsaKeyCacheImport() still requests MLDSA_MAX_BOTH_KEY_DER_SIZE from wh_Server_KeystoreGetCacheSlotChecked(), but the PR now allows WOLFHSM_CFG_SERVER_KEYCACHE_BIG_BUFSIZE >= MLDSA_MAX_PUB_KEY_DER_SIZE in verify-only mode, so key import fails at runtime in any minimally-configured verify-only build.

Recommendation: Replace both MLDSA_MAX_BOTH_KEY_DER_SIZE occurrences in wh_Server_MlDsaKeyCacheImport() with WH_SERVER_MLDSA_MAX_CACHE_DER_SIZE.

Referenced code: src/wh_server_crypto.c:800-804 (5 lines)

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This review was generated automatically by Fenrir. Findings are non-blocking.

[padelsbach]

Agree with the Fenrir finding. Please correct uses of WH_SERVER_MLDSA_MAX_CACHE_DER_SIZE.

[wolfSSL-Fenrir-bot]

Fenrir Automated Review — PR #452

Scan targets checked: wolfhsm-crypto-bugs, wolfhsm-src

Findings: 2
2 finding(s) posted as inline comments (see file-level comments below)

This review was generated automatically by Fenrir. Findings are non-blocking.

[padelsbach]

@miyazakh there was a github outage earlier which caused test failures. Can you push again to re-trigger CI?

[miyazakh]

@padelsbach
It seems that all the tests passed after manual re-testing.

[padelsbach]

LGTM, will give @bigbrett a chance for a final review.