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linuxkm ecdh: force zero shared secret buffer, and clear old key. #8685

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Merged
douzzer merged 1 commit into from
Apr 17, 2025
Merged

linuxkm ecdh: force zero shared secret buffer, and clear old key. #8685

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32 changes: 31 additions & 1 deletion linuxkm/lkcapi_ecdh_glue.c
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Original file line number Diff line number Diff line change
Expand Up @@ -30,6 +30,14 @@
#include <wolfssl/wolfcrypt/ecc.h>
#include <crypto/ecdh.h>

/* need misc.c for ForceZero(). */
#ifdef NO_INLINE
#include <wolfssl/wolfcrypt/misc.h>
#else
#define WOLFSSL_MISC_INCLUDED
#include <wolfcrypt/src/misc.c>
#endif

#define WOLFKM_ECDH_DRIVER ("ecdh-wolfcrypt")

#define WOLFKM_ECDH_P192_NAME ("ecdh-nist-p192")
Expand Down Expand Up @@ -167,6 +175,24 @@ static int km_ecdh_set_secret(struct crypto_kpp *tfm, const void *buf,
return -EINVAL;
}

if (ctx->key->type == ECC_PRIVATEKEY ||
ctx->key->type == ECC_PRIVATEKEY_ONLY) {
/* private key already set. force clear it. */
wc_ecc_free(ctx->key);

err = wc_ecc_init(ctx->key);
if (unlikely(err < 0)) {
return -ENOMEM;
}

#ifdef ECC_TIMING_RESISTANT
err = wc_ecc_set_rng(ctx->key, &ctx->rng);
if (unlikely(err < 0)) {
return -ENOMEM;
}
#endif /* ECC_TIMING_RESISTANT */
}

if (!params.key || !params.key_size) {
/* Empty secret payload. Generate our own ecc key pair */
err = wc_ecc_make_key_ex(&ctx->rng, ctx->curve_len, ctx->key,
Expand Down Expand Up @@ -544,7 +570,11 @@ static int km_ecdh_compute_shared_secret(struct kpp_request *req)
scatterwalk_map_and_copy(shared_secret, req->dst, 0, shared_secret_len, 1);

ecdh_shared_secret_end:
if (shared_secret) { free(shared_secret); shared_secret = NULL; }
if (shared_secret) {
ForceZero(shared_secret, shared_secret_len);
free(shared_secret);
shared_secret = NULL;
}
if (pub) { free(pub); pub = NULL; }

if (ecc_pub) {
Expand Down