linux-kernel - [PATCH v2 02/14] crypto: ecdsa - Adjust tests on length of key parameters

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Date: Thu, 15 Feb 2024 18:14:01 -0500
From: Stefan Berger <stefanb@...ux.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,
        Stefan Berger <stefanb@...ux.ibm.com>
Subject: [PATCH v2 02/14] crypto: ecdsa - Adjust tests on length of key parameters

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>
---
 crypto/ecdsa.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/crypto/ecdsa.c b/crypto/ecdsa.c
index ba8fb76fd165..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)
@@ -239,7 +239,7 @@ static int ecdsa_set_pub_key(struct crypto_akcipher *tfm, const void *key, unsig
 	keylen--;
 	digitlen = keylen >> 1;

-	ndigits = digitlen / sizeof(u64);
+	ndigits = DIV_ROUND_UP(digitlen, sizeof(u64));
 	if (ndigits != ctx->curve->g.ndigits)
 		return -EINVAL;

-- 
2.43.0