Re: [PATCH v5 10/10] integrity: support EC-RDSA signatures for asymmetric_verify

From: Thiago Jung Bauermann
Date: Mon Feb 25 2019 - 16:57:36 EST



Hello Vitaly,

Vitaly Chikunov <vt@xxxxxxxxxxxx> writes:

> Allow to use EC-RDSA signatures for IMA by determining signature type by
> the hash algorithm name. This works good for EC-RDSA since Streebog and
> EC-RDSA should always be used together.
>
> Cc: Mimi Zohar <zohar@xxxxxxxxxxxxx>
> Cc: Dmitry Kasatkin <dmitry.kasatkin@xxxxxxxxx>
> Cc: linux-integrity@xxxxxxxxxxxxxxx
> Signed-off-by: Vitaly Chikunov <vt@xxxxxxxxxxxx>
> ---
> security/integrity/digsig_asymmetric.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/security/integrity/digsig_asymmetric.c b/security/integrity/digsig_asymmetric.c
> index d775e03fbbcc..c4a3313e0210 100644
> --- a/security/integrity/digsig_asymmetric.c
> +++ b/security/integrity/digsig_asymmetric.c
> @@ -104,9 +104,14 @@ int asymmetric_verify(struct key *keyring, const char *sig,
>
> memset(&pks, 0, sizeof(pks));
>
> - pks.pkey_algo = "rsa";
> pks.hash_algo = hash_algo_name[hdr->hash_algo];
> - pks.encoding = "pkcs1";
> + if (!strncmp(pks.hash_algo, "streebog", 8)) {

Is it possible to test hdr->hash_algo instead of pkcs.hash_algo? IMHO if
an integer value is available it's preferable to check it rather than
doing a string comparison.

Also, it would be good to have a comment here mentioning that Streebog
and EC-RDSA should always be used together

> + pks.pkey_algo = "ecrdsa";
> + pks.encoding = "raw";
> + } else {
> + pks.pkey_algo = "rsa";
> + pks.encoding = "pkcs1";
> + }
> pks.digest = (u8 *)data;
> pks.digest_size = datalen;
> pks.s = hdr->sig;

--
Thiago Jung Bauermann
IBM Linux Technology Center