94 lines
3 KiB
Go
94 lines
3 KiB
Go
// This file is part of the happyDeliver (R) project.
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// Copyright (c) 2025 happyDomain
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// Authors: Pierre-Olivier Mercier, et al.
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//
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// This program is offered under a commercial and under the AGPL license.
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// For commercial licensing, contact us at <contact@happydomain.org>.
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//
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// For AGPL licensing:
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Affero General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Affero General Public License for more details.
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//
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// You should have received a copy of the GNU Affero General Public License
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// along with this program. If not, see <https://www.gnu.org/licenses/>.
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package analyzer
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import (
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"context"
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"git.happydns.org/happyDeliver/internal/api"
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)
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// checkPTRAndForward performs reverse DNS lookup (PTR) and forward confirmation (A/AAAA)
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// Returns PTR hostnames and their corresponding forward-resolved IPs
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func (d *DNSAnalyzer) checkPTRAndForward(ip string) ([]string, []string) {
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ctx, cancel := context.WithTimeout(context.Background(), d.Timeout)
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defer cancel()
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// Perform reverse DNS lookup (PTR)
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ptrNames, err := d.resolver.LookupAddr(ctx, ip)
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if err != nil || len(ptrNames) == 0 {
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return nil, nil
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}
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var forwardIPs []string
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seenIPs := make(map[string]bool)
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// For each PTR record, perform forward DNS lookup (A/AAAA)
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for _, ptrName := range ptrNames {
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// Look up A records
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ctx, cancel := context.WithTimeout(context.Background(), d.Timeout)
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aRecords, err := d.resolver.LookupHost(ctx, ptrName)
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cancel()
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if err == nil {
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for _, forwardIP := range aRecords {
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if !seenIPs[forwardIP] {
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forwardIPs = append(forwardIPs, forwardIP)
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seenIPs[forwardIP] = true
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}
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}
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}
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}
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return ptrNames, forwardIPs
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}
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// Proper reverse DNS (PTR) and forward-confirmed reverse DNS (FCrDNS) is important for deliverability
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func (d *DNSAnalyzer) calculatePTRScore(results *api.DNSResults, senderIP string) (score int) {
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if results.PtrRecords != nil && len(*results.PtrRecords) > 0 {
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// 50 points for having PTR records
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score += 50
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if len(*results.PtrRecords) > 1 {
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// Penalty has it's bad to have multiple PTR records
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score -= 15
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}
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// Additional 50 points for forward-confirmed reverse DNS (FCrDNS)
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// This means the PTR hostname resolves back to IPs that include the original sender IP
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if results.PtrForwardRecords != nil && len(*results.PtrForwardRecords) > 0 && senderIP != "" {
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// Verify that the sender IP is in the list of forward-resolved IPs
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fcrDnsValid := false
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for _, forwardIP := range *results.PtrForwardRecords {
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if forwardIP == senderIP {
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fcrDnsValid = true
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break
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}
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}
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if fcrDnsValid {
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score += 50
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}
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}
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}
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return
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}
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