Initial commit

checker/rule.go

@@ -0,0 +1,125 @@
+package checker
+
+import (
+	"context"
+	"fmt"
+	"strings"
+
+	sdk "git.happydns.org/checker-sdk-go/checker"
+)
+
+func Rule() sdk.CheckRule {
+	return &smtpRule{}
+}
+
+type smtpRule struct{}
+
+func (r *smtpRule) Name() string {
+	return "smtp_server"
+}
+
+func (r *smtpRule) Description() string {
+	return "Checks MX discovery, SMTP connectivity, STARTTLS, PTR/FCrDNS and mail-acceptance posture for an email-receiving domain"
+}
+
+func (r *smtpRule) Evaluate(ctx context.Context, obs sdk.ObservationGetter, opts sdk.CheckerOptions) sdk.CheckState {
+	var data SMTPData
+	if err := obs.Get(ctx, ObservationKeySMTP, &data); err != nil {
+		return sdk.CheckState{
+			Status:  sdk.StatusError,
+			Message: fmt.Sprintf("failed to load SMTP observation: %v", err),
+			Code:    "smtp.observation_error",
+		}
+	}
+
+	issues := append([]Issue(nil), data.Issues...)
+
+	// Fold related TLS observations so cert/chain problems show up on the
+	// SMTP service page without requiring the user to open a separate
+	// report.
+	related, _ := obs.GetRelated(ctx, TLSRelatedKey)
+	issues = append(issues, tlsIssuesFromRelated(related)...)
+
+	worst := sdk.StatusOK
+	critMsgs, warnMsgs := []string{}, []string{}
+	var firstCritCode, firstWarnCode string
+
+	for _, is := range issues {
+		switch is.Severity {
+		case SeverityCrit:
+			if worst < sdk.StatusCrit {
+				worst = sdk.StatusCrit
+			}
+			if firstCritCode == "" {
+				firstCritCode = is.Code
+			}
+			critMsgs = append(critMsgs, is.Message)
+		case SeverityWarn:
+			if worst < sdk.StatusWarn {
+				worst = sdk.StatusWarn
+			}
+			if firstWarnCode == "" {
+				firstWarnCode = is.Code
+			}
+			warnMsgs = append(warnMsgs, is.Message)
+		}
+	}
+
+	// Null-MX is a *declared* refusal of mail; it's an INFO, not a fail.
+	if data.MX.NullMX {
+		return sdk.CheckState{
+			Status:  sdk.StatusInfo,
+			Message: "Domain refuses all email via null MX (RFC 7505).",
+			Code:    CodeNullMX,
+			Meta: map[string]any{
+				"null_mx": true,
+			},
+		}
+	}
+
+	meta := map[string]any{
+		"has_ipv4":          data.Coverage.HasIPv4,
+		"has_ipv6":          data.Coverage.HasIPv6,
+		"any_starttls":      data.Coverage.AnySTARTTLS,
+		"all_starttls":      data.Coverage.AllSTARTTLS,
+		"all_accept_mail":   data.Coverage.AllAcceptMail,
+		"mx_count":          len(data.MX.Records),
+		"endpoint_count":    len(data.Endpoints),
+		"native_issues":     len(data.Issues),
+		"related_tls_count": len(related),
+	}
+
+	switch worst {
+	case sdk.StatusOK:
+		return sdk.CheckState{
+			Status:  sdk.StatusOK,
+			Message: fmt.Sprintf("SMTP operational (%d MX, %d endpoints, TLS=%v)", len(data.MX.Records), len(data.Endpoints), data.Coverage.AllSTARTTLS),
+			Code:    "smtp.ok",
+			Meta:    meta,
+		}
+	case sdk.StatusWarn:
+		return sdk.CheckState{
+			Status:  sdk.StatusWarn,
+			Message: "SMTP works with warnings: " + joinTop(warnMsgs, 2),
+			Code:    firstWarnCode,
+			Meta:    meta,
+		}
+	default:
+		return sdk.CheckState{
+			Status:  sdk.StatusCrit,
+			Message: "SMTP broken: " + joinTop(critMsgs, 2),
+			Code:    firstCritCode,
+			Meta:    meta,
+		}
+	}
+}
+
+func joinTop(msgs []string, n int) string {
+	if len(msgs) == 0 {
+		return ""
+	}
+	if len(msgs) <= n {
+		return strings.Join(msgs, "; ")
+	}
+	return strings.Join(msgs[:n], "; ") + fmt.Sprintf(" (+%d more)", len(msgs)-n)
+}