Hi! > ecdh_set_secret() casts a void* pointer to a const u64* in order to > feed it into ecc_is_key_valid(). This is not generally permitted by > the C standard, and leads to actual misalignment faults on ARMv6 > cores. In some cases, these are fixed up in software, but this still > leads to performance hits that are entirely avoidable. > > So let's copy the key into the ctx buffer first, which we will do > anyway in the common case, and which guarantees correct alignment.
Fair enough... but: params.key_size is validated in
ecc_is_key_valid(), and that now happens _after_ memcpy.
How is it guaranteed that we don't overflow the buffer during memcpy?
> +++ b/crypto/ecdh.c
> @@ -57,12 +57,13 @@ static int ecdh_set_secret(struct crypto
> return ecc_gen_privkey(ctx->curve_id, ctx->ndigits,
> ctx->private_key);
>
> - if (ecc_is_key_valid(ctx->curve_id, ctx->ndigits,
> - (const u64 *)params.key, params.key_size) < 0)
> - return -EINVAL;
> -
> memcpy(ctx->private_key, params.key, params.key_size);
>
> + if (ecc_is_key_valid(ctx->curve_id, ctx->ndigits,
> + ctx->private_key, params.key_size) < 0) {
> + memzero_explicit(ctx->private_key, params.key_size);
> + return -EINVAL;
> + }
> return 0;
Best regards,
Pavel
--
DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
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