[PATCH v5 02/12] crypto: ecdsa - Adjust tests on length of key parameters

[Stefan Berger]

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@xxxxxxxxxxxxx>
Tested-by: Lukas Wunner <lukas@xxxxxxxxx>
---
 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