diff mbox series

[v7,03/13] crypto: ecdsa - Adjust tests on length of key parameters

Message ID 20240320114725.1644921-4-stefanb@linux.ibm.com (mailing list archive)
State Changes Requested
Delegated to: Herbert Xu
Headers show
Series [v7,01/13] crypto: ecc - Use ECC_CURVE_NIST_P192/256/384_DIGITS where possible | expand

Commit Message

Stefan Berger March 20, 2024, 11:47 a.m. UTC
In preparation for support of NIST P521, adjust the basic tests on the
length of the provided key parameters to only ensure that the length of the
x plus y coordinates parameter array is not an odd number and that each
coordinate fits into an array of 'ndigits' digits. Mathematical tests on
the key's parameters are then done in ecc_is_pubkey_valid_full rejecting
invalid keys.

The change is necessary since NIST P521 keys do not have keys with
coordinates that each require 'full' digits (= all bits in u64 used).
NIST P521 only requires 2 bytes (9 bits) in the most significant digit
unlike NIST P192/256/384 that each require multiple 'full' digits.

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Tested-by: Lukas Wunner <lukas@wunner.de>
---
 crypto/ecdsa.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Jarkko Sakkinen March 21, 2024, 5:11 p.m. UTC | #1
On Wed Mar 20, 2024 at 1:47 PM EET, Stefan Berger wrote:
> In preparation for support of NIST P521, adjust the basic tests on the
> length of the provided key parameters to only ensure that the length of the
> x plus y coordinates parameter array is not an odd number and that each
> coordinate fits into an array of 'ndigits' digits. Mathematical tests on
> the key's parameters are then done in ecc_is_pubkey_valid_full rejecting
> invalid keys.
>
> The change is necessary since NIST P521 keys do not have keys with
> coordinates that each require 'full' digits (= all bits in u64 used).
> NIST P521 only requires 2 bytes (9 bits) in the most significant digit
> unlike NIST P192/256/384 that each require multiple 'full' digits.
>
> Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
> Tested-by: Lukas Wunner <lukas@wunner.de>
> ---
>  crypto/ecdsa.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/crypto/ecdsa.c b/crypto/ecdsa.c
> index 6653dec17327..64e1e69d53ba 100644
> --- a/crypto/ecdsa.c
> +++ b/crypto/ecdsa.c
> @@ -230,7 +230,7 @@ static int ecdsa_set_pub_key(struct crypto_akcipher *tfm, const void *key, unsig
>  	if (ret < 0)
>  		return ret;
>  
> -	if (keylen < 1 || (((keylen - 1) >> 1) % sizeof(u64)) != 0)
> +	if (keylen < 1 || ((keylen - 1) & 1) != 0)
>  		return -EINVAL;
>  	/* we only accept uncompressed format indicated by '4' */
>  	if (d[0] != 4)

Had to write this down to the paper to fully get it but yeah makes
sense (especially since I just truncated 4 KiB blocks to 1 KiB
in my doc update :-)) but yeah seems to be correct:


Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>

I guess that in this case I can give also tested-by since I actually
did test the formula (on paper):

Tested-by: Jarkko Sakkinen <jarkko@kernel.org>

As in general for tested-by's for patches I've sent or seen in
circulation there's bunch of convetions I've encountered so I do
agree that it is up to Herbert to decide the correct one.

BR, Jarkko
diff mbox series

Patch

diff --git a/crypto/ecdsa.c b/crypto/ecdsa.c
index 6653dec17327..64e1e69d53ba 100644
--- a/crypto/ecdsa.c
+++ b/crypto/ecdsa.c
@@ -230,7 +230,7 @@  static int ecdsa_set_pub_key(struct crypto_akcipher *tfm, const void *key, unsig
 	if (ret < 0)
 		return ret;
 
-	if (keylen < 1 || (((keylen - 1) >> 1) % sizeof(u64)) != 0)
+	if (keylen < 1 || ((keylen - 1) & 1) != 0)
 		return -EINVAL;
 	/* we only accept uncompressed format indicated by '4' */
 	if (d[0] != 4)