Initial commit

checker/interactive.go

@@ -0,0 +1,135 @@
+//go:build standalone
+
+package checker
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net"
+	"net/http"
+	"strings"
+	"sync"
+
+	"github.com/miekg/dns"
+
+	sdk "git.happydns.org/checker-sdk-go/checker"
+)
+
+func (p *delegationProvider) RenderForm() []sdk.CheckerOptionField {
+	return []sdk.CheckerOptionField{
+		{
+			Id:          "domain",
+			Type:        "string",
+			Label:       "Delegated domain",
+			Placeholder: "sub.example.com",
+			Required:    true,
+			Description: "Fully-qualified name of the delegated zone to check.",
+		},
+	}
+}
+
+func (p *delegationProvider) ParseForm(r *http.Request) (sdk.CheckerOptions, error) {
+	domain := strings.TrimSpace(r.FormValue("domain"))
+	if domain == "" {
+		return nil, fmt.Errorf("domain is required")
+	}
+	fqdn := dns.Fqdn(domain)
+	labels := dns.SplitDomainName(fqdn)
+	if len(labels) < 2 {
+		return nil, fmt.Errorf("%q has no parent zone", domain)
+	}
+	parentZone := strings.Join(labels[1:], ".")
+	subdomain := labels[0]
+
+	resolver := interactiveResolver()
+
+	ctx := r.Context()
+	var (
+		wg        sync.WaitGroup
+		nsRecords []*dns.NS
+		dsRecords []*dns.DS
+		nsErr     error
+		dsErr     error
+	)
+	wg.Add(2)
+	go func() {
+		defer wg.Done()
+		nsRecords, nsErr = lookupRecords[*dns.NS](ctx, resolver, fqdn, dns.TypeNS, false)
+	}()
+	go func() {
+		defer wg.Done()
+		dsRecords, dsErr = lookupRecords[*dns.DS](ctx, resolver, fqdn, dns.TypeDS, true)
+	}()
+	wg.Wait()
+
+	if nsErr != nil {
+		return nil, fmt.Errorf("NS lookup for %s: %w", domain, nsErr)
+	}
+	if len(nsRecords) == 0 {
+		return nil, fmt.Errorf("no NS records found for %s", domain)
+	}
+	if dsErr != nil {
+		return nil, fmt.Errorf("DS lookup for %s: %w", domain, dsErr)
+	}
+
+	body, err := json.Marshal(delegationService{NameServers: nsRecords, DS: dsRecords})
+	if err != nil {
+		return nil, fmt.Errorf("marshal delegation service: %w", err)
+	}
+
+	svc := serviceMessage{
+		Type:    "abstract.Delegation",
+		Service: body,
+	}
+
+	return sdk.CheckerOptions{
+		"domain_name": parentZone,
+		"subdomain":   subdomain,
+		"service":     svc,
+	}, nil
+}
+
+var (
+	resolverOnce sync.Once
+	resolverAddr string
+
+	interactiveClient = &dns.Client{Timeout: dnsTimeout}
+)
+
+func interactiveResolver() string {
+	resolverOnce.Do(func() {
+		cfg, err := dns.ClientConfigFromFile("/etc/resolv.conf")
+		if err != nil || len(cfg.Servers) == 0 {
+			resolverAddr = net.JoinHostPort("1.1.1.1", "53")
+			return
+		}
+		resolverAddr = net.JoinHostPort(cfg.Servers[0], cfg.Port)
+	})
+	return resolverAddr
+}
+
+func lookupRecords[T dns.RR](ctx context.Context, resolver, fqdn string, qtype uint16, edns bool) ([]T, error) {
+	msg := new(dns.Msg)
+	msg.SetQuestion(fqdn, qtype)
+	msg.RecursionDesired = true
+	if edns {
+		msg.SetEdns0(4096, true)
+	}
+
+	in, _, err := interactiveClient.ExchangeContext(ctx, msg, resolver)
+	if err != nil {
+		return nil, err
+	}
+	if in.Rcode != dns.RcodeSuccess && in.Rcode != dns.RcodeNameError {
+		return nil, fmt.Errorf("rcode %s", dns.RcodeToString[in.Rcode])
+	}
+
+	var out []T
+	for _, rr := range in.Answer {
+		if t, ok := rr.(T); ok {
+			out = append(out, t)
+		}
+	}
+	return out, nil
+}