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SubjectRe: [PATCH 10/18] crypto: dh - introduce support for ephemeral key generation to dh-generic
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Am Mittwoch, 1. Dezember 2021, 01:48:50 CET schrieb Nicolai Stange:

Hi Nicolai,

> The support for NVME in-band authentication currently in the works ([1])
> needs to generate ephemeral DH keys. Make dh-generic's ->set_secret()
> to generate an ephemeral key via the recently added crypto_dh_gen_privkey()
> in case the input ->key_size is zero. Note that this behaviour is in
> analogy to ecdh's ->set_secret().
>
> [1] https://lkml.kernel.org/r/20211122074727.25988-4-hare@suse.de
>
> Signed-off-by: Nicolai Stange <nstange@suse.de>
> ---
> crypto/dh.c | 24 ++++++++++++++++++++----
> 1 file changed, 20 insertions(+), 4 deletions(-)
>
> diff --git a/crypto/dh.c b/crypto/dh.c
> index 131b80064cb1..2e49b114e038 100644
> --- a/crypto/dh.c
> +++ b/crypto/dh.c
> @@ -71,25 +71,41 @@ static int dh_set_secret(struct crypto_kpp *tfm, const
> void *buf, {
> struct dh_ctx *ctx = dh_get_ctx(tfm);
> struct dh params;
> + char key[CRYPTO_DH_MAX_PRIVKEY_SIZE];
> + int err;
>
> /* Free the old MPI key if any */
> dh_clear_ctx(ctx);
>
> - if (crypto_dh_decode_key(buf, len, &params) < 0)
> + err = crypto_dh_decode_key(buf, len, &params);
> + if (err)
> goto err_clear_ctx;
>
> - if (dh_set_params(ctx, &params) < 0)
> + if (!params.key_size) {

As this params data may come from user space, shouldn't we use the same logic
as in ecdh's set_key function:

if (!params.key || !params.key_size)

?


> + err = crypto_dh_gen_privkey(params.group_id, key,
> + &params.key_size);
> + if (err)
> + goto err_clear_ctx;
> + params.key = key;
> + }
> +
> + err = dh_set_params(ctx, &params);
> + if (err)
> goto err_clear_ctx;
>
> ctx->xa = mpi_read_raw_data(params.key, params.key_size);
> - if (!ctx->xa)
> + if (!ctx->xa) {
> + err = -EINVAL;
> goto err_clear_ctx;
> + }
> +
> + memzero_explicit(key, sizeof(key));
>
> return 0;
>
> err_clear_ctx:
> dh_clear_ctx(ctx);
> - return -EINVAL;
> + return err;
> }
>
> /*


Ciao
Stephan


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