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KEYS: asymmetric: Fix ECDSA use via keyctl uapi 

When support for ECDSA keys was added, constraints for data & signature
sizes were never updated.  This makes it impossible to use such keys via
keyctl API from userspace.

Update constraint on max_data_size to 64 bytes in order to support
SHA512-based signatures. Also update the signature length constraints
per ECDSA signature encoding described in RFC 5480.

Fixes: 299f561a66 ("x509: Add support for parsing x509 certs with ECDSA keys")
Signed-off-by: Denis Kenzior <denkenz@gmail.com>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
This commit is contained in:
Denis Kenzior 2022-08-26 09:51:19 -05:00 committed by Jarkko Sakkinen
parent c95e8f6fd1
commit 10de7b5429
1 changed files with 22 additions and 2 deletions
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24
crypto/asymmetric_keys/public_key.c
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@ -186,8 +186,28 @@ static int software_key_query(const struct kernel_pkey_params *params,
len = crypto_akcipher_maxsize(tfm);
info->key_size = len * 8;
info->max_data_size = len;
info->max_sig_size = len;
if (strncmp(pkey->pkey_algo, "ecdsa", 5) == 0) {
/*
* ECDSA key sizes are much smaller than RSA, and thus could
* operate on (hashed) inputs that are larger than key size.
* For example SHA384-hashed input used with secp256r1
* based keys. Set max_data_size to be at least as large as
* the largest supported hash size (SHA512)
*/
info->max_data_size = 64;
/*
* Verify takes ECDSA-Sig (described in RFC 5480) as input,
* which is actually 2 'key_size'-bit integers encoded in
* ASN.1. Account for the ASN.1 encoding overhead here.
*/
info->max_sig_size = 2 * (len + 3) + 2;
} else {
info->max_data_size = len;
info->max_sig_size = len;
}
info->max_enc_size = len;
info->max_dec_size = len;
info->supported_ops = (KEYCTL_SUPPORTS_ENCRYPT |