package rfc

/*
 * ZLint Copyright 2020 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.
 */

/************************************************************************
RFC 5280: 4.2.1.6
When the subjectAltName extension contains a domain name system
   label, the domain name MUST be stored in the dNSName (an IA5String).
   The name MUST be in the "preferred name syntax", as specified by
   Section 3.5 of [RFC1034] and as modified by Section 2.1 of
   [RFC1123].  Note that while uppercase and lowercase letters are
   allowed in domain names, no significance is attached to the case.  In
   addition, while the string " " is a legal domain name, subjectAltName
   extensions with a dNSName of " " MUST NOT be used.  Finally, the use
   of the DNS representation for Internet mail addresses
   (subscriber.example.com instead of subscriber@example.com) MUST NOT
   be used; such identities are to be encoded as rfc822Name.  Rules for
   encoding internationalized domain names are specified in Section 7.2.
************************************************************************/

import (
	"github.com/zmap/zcrypto/x509"
	"github.com/zmap/zlint/v2/lint"
	"github.com/zmap/zlint/v2/util"
)

type SANIsSpaceDNS struct{}

func (l *SANIsSpaceDNS) Initialize() error {
	return nil
}

func (l *SANIsSpaceDNS) CheckApplies(c *x509.Certificate) bool {
	return util.IsExtInCert(c, util.SubjectAlternateNameOID)
}

func (l *SANIsSpaceDNS) Execute(c *x509.Certificate) *lint.LintResult {
	for _, dns := range c.DNSNames {
		if dns == " " {
			return &lint.LintResult{Status: lint.Error}
		}
	}
	return &lint.LintResult{Status: lint.Pass}
}

func init() {
	lint.RegisterLint(&lint.Lint{
		Name:          "e_ext_san_space_dns_name",
		Description:   "The dNSName ` ` MUST NOT be used",
		Citation:      "RFC 5280: 4.2.1.6",
		Source:        lint.RFC5280,
		EffectiveDate: util.RFC2459Date,
		Lint:          &SANIsSpaceDNS{},
	})
}
