nvme-auth: allow mixing of secret and hash lengths

We can now use any of the secret transformation hashes with a
secret, regardless of the secret size.
e.g. a 32 byte key with the SHA-512(64 byte) hash.

The example secret from the spec should now be permitted with
any of the following:
DHHC-1:00:ia6zGodOr4SEG0Zzaw398rpY0wqipUWj4jWjUh4HWUz6aQ2n:
DHHC-1:01:ia6zGodOr4SEG0Zzaw398rpY0wqipUWj4jWjUh4HWUz6aQ2n:
DHHC-1:02:ia6zGodOr4SEG0Zzaw398rpY0wqipUWj4jWjUh4HWUz6aQ2n:
DHHC-1:03:ia6zGodOr4SEG0Zzaw398rpY0wqipUWj4jWjUh4HWUz6aQ2n:

Note: Secrets are still restricted to 32,48 or 64 bits.
Co-developed-by: Akash Appaiah <Akash.Appaiah@dell.com>
Signed-off-by: Akash Appaiah <Akash.Appaiah@dell.com>
Signed-off-by: Mark O'Donovan <shiftee@posteo.net>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>

drivers/nvme/common/auth.c

@@ -190,14 +190,6 @@ struct nvme_dhchap_key *nvme_auth_extract_key(unsigned char *secret,
 		goto out_free_secret;
 	}
 
-	if (key_hash > 0 &&
-	    (key_len - 4) != nvme_auth_hmac_hash_len(key_hash)) {
-		pr_err("Mismatched key len %d for %s\n", key_len,
-		       nvme_auth_hmac_name(key_hash));
-		ret = -EINVAL;
-		goto out_free_secret;
-	}
-
 	/* The last four bytes is the CRC in little-endian format */
 	key_len -= 4;
 	/*