kmgmt: add encoder import-object wrappers

[yosuke-wolfssl]

Problem

The encoder OSSL_FUNC_ENCODER_IMPORT_OBJECT slot must be
void *(void *encoder_ctx, int selection, const OSSL_PARAM[]): it receives the
context from OSSL_FUNC_ENCODER_NEWCTX and returns a newly allocated key. All 72
encoder dispatch tables registered the key-management import instead, which is
int (wp_<Alg> *key, int, const OSSL_PARAM[]). The DFUNC cast hides both
mismatches:

• Arg 1 — OpenSSL passes a wp_<Alg>EncDecCtx * (7 scalar fields) where a much
  larger key struct is expected, so the import writes key material past its end.
• Return — the int 1/0 is read as the object pointer, so encoder_encode()
  dereferences it and encoder_destruct_pkey() frees it.

import_object is called only when the key's keymgmt provider differs from the
encoder's, i.e. OSSL_ENCODER_CTX_new_for_pkey() on a foreign key in a
multi-provider OSSL_LIB_CTX. Registering the slot is what makes wolfProvider's
encoders eligible for that path — collect_encoder() skips a foreign encoder whose
import_object is NULL. The sharpest case is a key from OpenSSL's FIPS provider,
which ships no encoders of its own. Not reachable in single-provider or
replace-default deployments.

Fix (src/wp_*_kmgmt.c)

A correctly typed wp_<alg>_import_object() per algorithm, mirroring OpenSSL's own
ossl_prov_import_key() and the existing wp_<alg>_export_object() wrappers:

static wp_Ecc* wp_ecc_import_object(wp_EccEncDecCtx* ctx, int selection,
    const OSSL_PARAM params[])
{
    wp_Ecc* ecc = wp_ecc_new(ctx->provCtx);

    if ((ecc != NULL) && (!wp_ecc_import(ecc, selection, params))) {
        wp_ecc_free(ecc);
        ecc = NULL;
    }
    return ecc;
}

File	Tables	Key allocated with
wp_ecx_kmgmt.c	24	wp_ecx_new_by_type(ctx->provCtx, ctx->keyType, NULL)
wp_mldsa_kmgmt.c	18	ctx->newKey(ctx->provCtx)
wp_rsa_kmgmt.c	12	wp_rsa_base_new(ctx->provCtx, ctx->type)
wp_ecc_kmgmt.c	10	wp_ecc_new(ctx->provCtx)
wp_dh_kmgmt.c	8	wp_dh_new(ctx->provCtx)

OSSL_FUNC_ENCODER_FREE_OBJECT (wp_<alg>_free) is already shaped for a real key
object and is unchanged. wp_ecx_new_by_type() factors the key-type chain out of
wp_ecx_decode() so both callers share it.

Closes f_11552.

Tests

test_encoder_import_object() in test/test_pkey.c drives the dispatch entry
directly, so it does not depend on which encoder OpenSSL would pick: it pulls the
encoder and keymgmt tables from the provider's operation query, runs NEWCTX and
IMPORT_OBJECT over parameters from EVP_PKEY_todata() on a default-provider key,
checks the returned object against the keymgmt export, then calls FREE_OBJECT and
FREECTX. Per-algorithm drivers cover RSA and RSA-PSS, EC, all four ECX key types,
DH and ML-DSA-44 — every context-dependent allocation branch above.

Verification

• Clean build under the project's -Werror flag set; no new warnings.
• Unit suite 211 passed, 0 failed.
• Negative control: with the fix reverted, EC and X25519 abort with SIGSEGV and
  RSA and DH fail on a NULL object.

[Copilot]

Pull request overview

Fixes wolfProvider encoder dispatch tables to implement OSSL_FUNC_ENCODER_IMPORT_OBJECT with the correct “import-object” semantics (receive encoder ctx, allocate and return a new provider key object), preventing memory corruption and invalid frees when encoding keys owned by a different provider in multi-provider OSSL_LIB_CTX scenarios.

Changes:

• Add per-algorithm *_import_object() wrappers that allocate a new key object and import parameters into it, and register them in encoder dispatch tables.
• Refactor ECX key allocation into wp_ecx_new_by_type() so decode and import-object share the same key-type selection logic.
• Add unit tests that directly drive NEWCTX + IMPORT_OBJECT + FREE_OBJECT + FREECTX and validate imported key material via keymgmt export.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
test/unit.h	Declares new import-object contract test helpers and per-alg test entrypoints.
test/unit.c	Registers new import-object tests in the unit test table.
test/test_pkey.c	Implements generic provider dispatch-table probing + import-object contract test harness.
test/test_rsa.c	Adds RSA/RSA-PSS coverage for encoder import-object behavior.
test/test_ecc.c	Adds EC encoder import-object test (P-256 public+params).
test/test_ecx.c	Adds ECX import-object coverage across X25519/ED25519/X448/ED448 variants.
test/test_dh.c	Adds DH import-object test using named group parameters.
test/test_mldsa.c	Adds ML-DSA-44 import-object test coverage.
src/wp_rsa_kmgmt.c	Adds wp_rsa_import_object() and wires it into all RSA encoder dispatch tables.
src/wp_ecc_kmgmt.c	Adds wp_ecc_import_object() and wires it into ECC encoder dispatch tables.
src/wp_ecx_kmgmt.c	Adds wp_ecx_new_by_type() + wp_ecx_import_object() and updates ECX encoder dispatch tables.
src/wp_dh_kmgmt.c	Adds wp_dh_import_object() and wires it into DH encoder dispatch tables.
src/wp_mldsa_kmgmt.c	Adds wp_mldsa_import_object() and wires it into ML-DSA encoder dispatch tables (macro-generated).

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[wolfSSL-Fenrir-bot]

Fenrir Automated Review — PR #475

Scan targets checked: wolfprovider-bugs
Failed targets: wolfprovider-src

⚠️ Review incomplete — one or more scan targets failed before findings could be produced. See the Fenrir PR review detail page for logs.