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Wed, 06 Mar 2024 22:23:13 +0000 Received: from smtpav01.dal12v.mail.ibm.com (smtpav01.dal12v.mail.ibm.com [10.241.53.100]) by smtprelay04.wdc07v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 426MNASQ28508472 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 6 Mar 2024 22:23:12 GMT Received: from smtpav01.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C2AF558062; Wed, 6 Mar 2024 22:23:08 +0000 (GMT) Received: from smtpav01.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4FC4D58058; Wed, 6 Mar 2024 22:23:08 +0000 (GMT) Received: from sbct-3.pok.ibm.com (unknown [9.47.158.153]) by smtpav01.dal12v.mail.ibm.com (Postfix) with ESMTP; Wed, 6 Mar 2024 22:23:08 +0000 (GMT) From: Stefan Berger To: keyrings@vger.kernel.org, linux-crypto@vger.kernel.org, herbert@gondor.apana.org.au, davem@davemloft.net Cc: linux-kernel@vger.kernel.org, saulo.alessandre@tse.jus.br, lukas@wunner.de, Stefan Berger Subject: [PATCH v5 11/12] crypto: asymmetric_keys - Adjust signature size calculation for NIST P521 Date: Wed, 6 Mar 2024 17:22:56 -0500 Message-ID: <20240306222257.979304-12-stefanb@linux.ibm.com> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240306222257.979304-1-stefanb@linux.ibm.com> References: <20240306222257.979304-1-stefanb@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-crypto@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-GUID: _O9rktJyayujSsv9haRpYPw9T09uALa4 X-Proofpoint-ORIG-GUID: _O9rktJyayujSsv9haRpYPw9T09uALa4 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.1011,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2024-03-06_12,2024-03-05_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 suspectscore=0 adultscore=0 impostorscore=0 bulkscore=0 phishscore=0 mlxscore=0 mlxlogscore=999 spamscore=0 malwarescore=0 lowpriorityscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2311290000 definitions=main-2403060181 Adjust the calculation of the maximum signature size for support of NIST P521. While existing curves may prepend a 0 byte to their coordinates (to make the number positive), NIST P521 will not do this since only the first bit in the most significant byte is used. If the encoding of the x & y coordinates requires at least 128 bytes then an additional byte is needed for the encoding of the length. Take this into account when calculating the maximum signature size. Signed-off-by: Stefan Berger Reviewed-by: Lukas Wunner Tested-by: Lukas Wunner --- crypto/asymmetric_keys/public_key.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/crypto/asymmetric_keys/public_key.c b/crypto/asymmetric_keys/public_key.c index e5f22691febd..16cc0be28929 100644 --- a/crypto/asymmetric_keys/public_key.c +++ b/crypto/asymmetric_keys/public_key.c @@ -233,6 +233,7 @@ static int software_key_query(const struct kernel_pkey_params *params, info->key_size = len * 8; if (strncmp(pkey->pkey_algo, "ecdsa", 5) == 0) { + int slen = len; /* * ECDSA key sizes are much smaller than RSA, and thus could * operate on (hashed) inputs that are larger than key size. @@ -246,8 +247,19 @@ static int software_key_query(const struct kernel_pkey_params *params, * 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. + * + * NIST P192/256/384 may prepend a '0' to a coordinate to + * indicate a positive integer. NIST P521 never needs it. */ - info->max_sig_size = 2 * (len + 3) + 2; + if (strcmp(pkey->pkey_algo, "ecdsa-nist-p521") != 0) + slen += 1; + /* Length of encoding the x & y coordinates */ + slen = 2 * (slen + 2); + /* + * If coordinate encoding takes at least 128 bytes then an + * additional byte for length encoding is needed. + */ + info->max_sig_size = 1 + (slen >= 128) + 1 + slen; } else { info->max_data_size = len; info->max_sig_size = len;