On Wed, Jan 21, 2026 at 10:36:04PM +0000, David Howells wrote:
> Calculate the SHA256 hash for blacklisting purposes independently of the
> signature hash (which may be something other than SHA256).
>
> This is necessary because when ML-DSA is used, no digest is calculated.
>
> Note that this represents a change of behaviour in that the hash used for
> the blacklist check would previously have been whatever digest was used
> for, say, RSA-based signatures. It may be that this is inadvisable.
>
> Signed-off-by: David Howells <[email protected]>
> cc: Lukas Wunner <[email protected]>
> cc: Ignat Korchagin <[email protected]>
> cc: Stephan Mueller <[email protected]>
> cc: Eric Biggers <[email protected]>
> cc: Herbert Xu <[email protected]>
> cc: [email protected]
> cc: [email protected]
> ---
> crypto/asymmetric_keys/x509_parser.h | 2 ++
> crypto/asymmetric_keys/x509_public_key.c | 23 +++++++++++++----------
> 2 files changed, 15 insertions(+), 10 deletions(-)
>
> diff --git a/crypto/asymmetric_keys/x509_parser.h
> b/crypto/asymmetric_keys/x509_parser.h
> index 0688c222806b..b7aeebdddb36 100644
> --- a/crypto/asymmetric_keys/x509_parser.h
> +++ b/crypto/asymmetric_keys/x509_parser.h
> @@ -9,12 +9,14 @@
> #include <linux/time.h>
> #include <crypto/public_key.h>
> #include <keys/asymmetric-type.h>
> +#include <crypto/sha2.h>
>
> struct x509_certificate {
> struct x509_certificate *next;
> struct x509_certificate *signer; /* Certificate that signed this
> one */
> struct public_key *pub; /* Public key details */
> struct public_key_signature *sig; /* Signature parameters */
> + u8 sha256[SHA256_DIGEST_SIZE]; /* Hash for blacklist
> purposes */
> char *issuer; /* Name of certificate issuer */
> char *subject; /* Name of certificate subject
> */
> struct asymmetric_key_id *id; /* Issuer + Serial number */
> diff --git a/crypto/asymmetric_keys/x509_public_key.c
> b/crypto/asymmetric_keys/x509_public_key.c
> index 12e3341e806b..6d002e3b20c5 100644
> --- a/crypto/asymmetric_keys/x509_public_key.c
> +++ b/crypto/asymmetric_keys/x509_public_key.c
> @@ -31,6 +31,19 @@ int x509_get_sig_params(struct x509_certificate *cert)
>
> pr_devel("==>%s()\n", __func__);
>
> + /* Calculate a SHA256 hash of the TBS and check it against the
> + * blacklist.
> + */
> + sha256(cert->tbs, cert->tbs_size, cert->sha256);
> + ret = is_hash_blacklisted(cert->sha256, sizeof(cert->sha256),
> + BLACKLIST_HASH_X509_TBS);
> + if (ret == -EKEYREJECTED) {
> + pr_err("Cert %*phN is blacklisted\n",
> + (int)sizeof(cert->sha256), cert->sha256);
> + cert->blacklisted = true;
> + ret = 0;
> + }
> +
> sig->s = kmemdup(cert->raw_sig, cert->raw_sig_size, GFP_KERNEL);
> if (!sig->s)
> return -ENOMEM;
> @@ -65,19 +78,9 @@ int x509_get_sig_params(struct x509_certificate *cert)
>
> ret = crypto_shash_digest(desc, cert->tbs, cert->tbs_size,
> sig->digest);
> -
nit: spurious diff unrelated to change
> if (ret < 0)
> goto error_2;
>
> - ret = is_hash_blacklisted(sig->digest, sig->digest_size,
> - BLACKLIST_HASH_X509_TBS);
> - if (ret == -EKEYREJECTED) {
> - pr_err("Cert %*phN is blacklisted\n",
> - sig->digest_size, sig->digest);
> - cert->blacklisted = true;
> - ret = 0;
> - }
> -
> error_2:
> kfree(desc);
> error:
>
I hold on for commentary (nit was is not reason to not give
reviewed-by) tho it looks to me acceptable.
BR, Jarkko
