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/*
* ZLint Copyright 2024 Regents of the University of Michigan
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy
* of the License at http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
* implied. See the License for the specific language governing
* permissions and limitations under the License.
*/
package rfc
import (
"fmt"
"sort"
"strings"
"github.com/zmap/zcrypto/x509"
"github.com/zmap/zlint/v3/lint"
"github.com/zmap/zlint/v3/util"
)
type ecdsaAllowedKU struct{}
/*
***********************************************
RFC 8813: 3. Updates to Section 3
If the keyUsage extension is present in a certificate that indicates
id-ecPublicKey in SubjectPublicKeyInfo, then the following values
MUST NOT be present:
keyEncipherment; and
dataEncipherment.
***********************************************
*/
func init() {
lint.RegisterCertificateLint(&lint.CertificateLint{
LintMetadata: lint.LintMetadata{
Name: "e_ecdsa_allowed_ku",
Description: "Key usage values keyEncipherment or dataEncipherment MUST NOT be present in certificates with ECDSA public keys",
Citation: "RFC 8813 Section 3",
Source: lint.RFC8813,
EffectiveDate: util.RFC8813Date,
},
Lint: NewEcdsaAllowedKU,
})
}
func NewEcdsaAllowedKU() lint.LintInterface {
return &ecdsaAllowedKU{}
}
// CheckApplies returns true when the certificate has an ECDSA public key and a key usage extension.
func (l *ecdsaAllowedKU) CheckApplies(c *x509.Certificate) bool {
return c.PublicKeyAlgorithm == x509.ECDSA && util.HasKeyUsageOID(c)
}
// Execute returns an Error level lint.LintResult if the ECDSA certificate
// being linted has the following Key Usage bits set: keyEncipherment or dataEncipherment.
func (l *ecdsaAllowedKU) Execute(c *x509.Certificate) *lint.LintResult {
// RFC 8813, Section 3 "Updates to Section 3" reads:
//
// If the keyUsage extension is present in a certificate that indicates
// id-ecPublicKey in SubjectPublicKeyInfo, then the following values
// MUST NOT be present:
//
// keyEncipherment; and
// dataEncipherment.
var invalidKUs []string
if util.HasKeyUsage(c, x509.KeyUsageKeyEncipherment) {
invalidKUs = append(invalidKUs, util.KeyUsageToString[x509.KeyUsageKeyEncipherment])
}
if util.HasKeyUsage(c, x509.KeyUsageDataEncipherment) {
invalidKUs = append(invalidKUs, util.KeyUsageToString[x509.KeyUsageDataEncipherment])
}
if len(invalidKUs) > 0 {
// Sort the invalid KUs to allow consistent ordering of Details messages for
// unit testing
sort.Strings(invalidKUs)
return &lint.LintResult{
Status: lint.Error,
Details: fmt.Sprintf("Certificate contains invalid key usage(s): %s", strings.Join(invalidKUs, ", ")),
}
}
return &lint.LintResult{Status: lint.Pass}
}
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