59 lines
1.8 KiB
Go
59 lines
1.8 KiB
Go
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package mailstore
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import (
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"context"
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"net"
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"strings"
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)
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// spamKeywords is a tiny, obvious-spam subject keyword list — a coarse signal only.
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var spamKeywords = []string{"viagra", "casino", "lottery winner", "click here now", "wire transfer urgent", "nigerian prince"}
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// SpamScore is a lightweight built-in heuristic — always runs, regardless of whether
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// rspamd (rspamd.go) is also enabled; both are additive, not either/or. Higher is more
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// suspicious; compare against [Mailstore] spam_reject_score.
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// ponytail: naive keyword/weight heuristic, not a real Bayesian/ML scorer — upgrade or
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// lean harder on rspamd if false-positive rate matters.
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func SpamScore(peerIP string, headers map[string]string, dkimPass, spfPass bool) int {
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score := 0
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if !spfPass {
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score += 2
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}
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if !dkimPass {
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score++
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}
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if CheckDNSBL(peerIP) {
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score += 5
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}
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subject := strings.ToLower(headers["subject"])
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for _, kw := range spamKeywords {
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if strings.Contains(subject, kw) {
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score++
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}
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}
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return score
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}
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// CheckDNSBL looks up peerIP against the Spamhaus ZEN DNSBL. Per RFC 5782, a listing
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// response is always an A record in 127.0.0.0/8 — checking for that range (rather than
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// "any resolution succeeded") avoids false positives from a resolver that hijacks
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// NXDOMAIN into a search/ad page instead of returning an error.
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func CheckDNSBL(peerIP string) bool {
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ip := net.ParseIP(peerIP)
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if ip == nil || ip.To4() == nil {
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return false
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}
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octets := strings.Split(ip.To4().String(), ".")
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reversed := octets[3] + "." + octets[2] + "." + octets[1] + "." + octets[0]
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addrs, err := net.DefaultResolver.LookupHost(context.Background(), reversed+".zen.spamhaus.org")
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if err != nil {
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return false
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}
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for _, a := range addrs {
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if resolved := net.ParseIP(a); resolved != nil && resolved.To4() != nil && resolved.To4()[0] == 127 {
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return true
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}
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}
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return false
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}
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