linux-kernel - [PATCH v6 03/13] crypto: ecdsa - Adjust tests on length of key parameters

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Date: Tue, 12 Mar 2024 14:36:08 -0400
From: Stefan Berger <stefanb@...ux.vnet.ibm.com>
To: keyrings@...r.kernel.org, linux-crypto@...r.kernel.org,
        herbert@...dor.apana.org.au, davem@...emloft.net
Cc: linux-kernel@...r.kernel.org, saulo.alessandre@....jus.br, lukas@...ner.de,
        bbhushan2@...vell.com, jarkko@...nel.org,
        Stefan Berger <stefanb@...ux.ibm.com>
Subject: [PATCH v6 03/13] crypto: ecdsa - Adjust tests on length of key parameters

From: Stefan Berger <stefanb@...ux.ibm.com>

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 fully require 'full' digits (= u64), unlike
NIST P192/256/384 that all require multiple 'full' digits.

Signed-off-by: Stefan Berger <stefanb@...ux.ibm.com>
Tested-by: Lukas Wunner <lukas@...ner.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)
-- 
2.43.0