happyDeliver/pkg/analyzer/dns_dkim.go

116 lines
3.2 KiB
Go

// This file is part of the happyDeliver (R) project.
// Copyright (c) 2025 happyDomain
// Authors: Pierre-Olivier Mercier, et al.
//
// This program is offered under a commercial and under the AGPL license.
// For commercial licensing, contact us at <contact@happydomain.org>.
//
// For AGPL licensing:
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
package analyzer
import (
"context"
"fmt"
"strings"
"git.happydns.org/happyDeliver/internal/api"
)
// checkapi.DKIMRecord looks up and validates DKIM record for a domain and selector
func (d *DNSAnalyzer) checkDKIMRecord(domain, selector string) *api.DKIMRecord {
// DKIM records are at: selector._domainkey.domain
dkimDomain := fmt.Sprintf("%s._domainkey.%s", selector, domain)
ctx, cancel := context.WithTimeout(context.Background(), d.Timeout)
defer cancel()
txtRecords, err := d.resolver.LookupTXT(ctx, dkimDomain)
if err != nil {
return &api.DKIMRecord{
Selector: selector,
Domain: domain,
Valid: false,
Error: api.PtrTo(fmt.Sprintf("Failed to lookup DKIM record: %v", err)),
}
}
if len(txtRecords) == 0 {
return &api.DKIMRecord{
Selector: selector,
Domain: domain,
Valid: false,
Error: api.PtrTo("No DKIM record found"),
}
}
// Concatenate all TXT record parts (DKIM can be split)
dkimRecord := strings.Join(txtRecords, "")
// Basic validation - should contain "v=DKIM1" and "p=" (public key)
if !d.validateDKIM(dkimRecord) {
return &api.DKIMRecord{
Selector: selector,
Domain: domain,
Record: api.PtrTo(dkimRecord),
Valid: false,
Error: api.PtrTo("DKIM record appears malformed"),
}
}
return &api.DKIMRecord{
Selector: selector,
Domain: domain,
Record: &dkimRecord,
Valid: true,
}
}
// validateDKIM performs basic DKIM record validation
func (d *DNSAnalyzer) validateDKIM(record string) bool {
// Should contain p= tag (public key)
if !strings.Contains(record, "p=") {
return false
}
// Often contains v=DKIM1 but not required
// If v= is present, it should be DKIM1
if strings.Contains(record, "v=") && !strings.Contains(record, "v=DKIM1") {
return false
}
return true
}
func (d *DNSAnalyzer) calculateDKIMScore(results *api.DNSResults) (score int) {
// DKIM provides strong email authentication
if results.DkimRecords != nil && len(*results.DkimRecords) > 0 {
hasValidDKIM := false
for _, dkim := range *results.DkimRecords {
if dkim.Valid {
hasValidDKIM = true
break
}
}
if hasValidDKIM {
score += 100
} else {
// Partial credit if DKIM record exists but has issues
score += 25
}
}
return
}