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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 (
"errors"
"fmt"
"regexp"
"github.com/zmap/zcrypto/encoding/asn1"
"github.com/zmap/zcrypto/x509"
"github.com/zmap/zlint/v3/lint"
"github.com/zmap/zlint/v3/util"
)
func init() {
lint.RegisterCertificateLint(&lint.CertificateLint{
LintMetadata: lint.LintMetadata{
Name: "e_subject_printable_string_badalpha",
Description: "PrintableString type's alphabet only includes a-z, A-Z, 0-9, and 11 special characters",
Citation: "RFC 5280: Appendix B. ASN.1 Notes",
Source: lint.RFC5280,
EffectiveDate: util.RFC2459Date,
},
Lint: NewSubjectPrintableStringBadAlpha,
})
}
func NewSubjectPrintableStringBadAlpha() lint.LintInterface {
return &subjectPrintableStringBadAlpha{}
}
var (
// Per RFC 5280, Appendix B. ASN.1 Notes:
// The character string type PrintableString supports a very basic Latin
// character set: the lowercase letters 'a' through 'z', uppercase
// letters 'A' through 'Z', the digits '0' through '9', eleven special
// characters ' = ( ) + , - . / : ? and space.
printableStringRegex = regexp.MustCompile(`^[a-zA-Z0-9\=\(\)\+,\-.\/:\? ']+$`)
)
// validatePrintableString returns an error if the provided encoded printable
// string doesn't adhere to the character set defined in RFC 5280.
func validatePrintableString(rawPS []byte) error {
if !printableStringRegex.Match(rawPS) {
return errors.New("encoded PrintableString contained illegal characters")
}
return nil
}
type subjectPrintableStringBadAlpha struct {
}
// CheckApplies returns true for any certificate with a non-empty RawSubject.
func (l *subjectPrintableStringBadAlpha) CheckApplies(c *x509.Certificate) bool {
return len(c.RawSubject) > 0
}
// Execute checks the certificate's RawSubject to ensure that any
// PrintableString attribute/value pairs in the Subject match the character set
// defined for this type in RFC 5280. An lint.Error level lint.LintResult is returned if any
// of the PrintableString attributes do not match a regular expression for the
// allowed character set.
func (l *subjectPrintableStringBadAlpha) Execute(c *x509.Certificate) *lint.LintResult {
rdnSequence := util.RawRDNSequence{}
rest, err := asn1.Unmarshal(c.RawSubject, &rdnSequence)
if err != nil {
return &lint.LintResult{
Status: lint.Fatal,
Details: "Failed to Unmarshal RawSubject into RawRDNSequence",
}
}
if len(rest) > 0 {
return &lint.LintResult{
Status: lint.Fatal,
Details: "Trailing data after RawSubject RawRDNSequence",
}
}
for _, attrTypeAndValueSet := range rdnSequence {
for _, attrTypeAndValue := range attrTypeAndValueSet {
// If the attribute type is a PrintableString the bytes of the attribute
// value must match the printable string alphabet.
if attrTypeAndValue.Value.Tag == asn1.TagPrintableString {
if err := validatePrintableString(attrTypeAndValue.Value.Bytes); err != nil {
return &lint.LintResult{
Status: lint.Error,
Details: fmt.Sprintf("RawSubject attr oid %s %s",
attrTypeAndValue.Type, err.Error()),
}
}
}
}
}
return &lint.LintResult{
Status: lint.Pass,
}
}
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