feat: add domain verification (#560)

* feat: add domain verification

* add checks

* add and fix tests

* fix go.mod

* regenerate proto

internal/api/http/domain_check.go

@@ -0,0 +1,83 @@
+package http
+
+import (
+	"fmt"
+	"io/ioutil"
+	"net"
+	"net/http"
+
+	"github.com/caos/zitadel/internal/errors"
+)
+
+type CheckType int
+
+const (
+	CheckTypeHTTP CheckType = iota
+	CheckTypeDNS
+
+	HTTPPattern = "https://%s/.well-known/zitadel-challenge/%s"
+	DNSPattern  = "_zitadel-challenge.%s"
+)
+
+func ValidateDomain(domain, token, verifier string, checkType CheckType) error {
+	switch checkType {
+	case CheckTypeHTTP:
+		return ValidateDomainHTTP(domain, token, verifier)
+	case CheckTypeDNS:
+		return ValidateDomainDNS(domain, verifier)
+	default:
+		return errors.ThrowInvalidArgument(nil, "HTTP-Iqd11", "Errors.Internal")
+	}
+}
+
+func ValidateDomainHTTP(domain, token, verifier string) error {
+	resp, err := http.Get(tokenUrlHTTP(domain, token))
+	if err != nil {
+		return errors.ThrowInternal(err, "HTTP-BH42h", "Errors.Internal")
+	}
+	if resp.StatusCode != 200 {
+		return errors.ThrowInternal(err, "HTTP-G2zsw", "Errors.Internal")
+	}
+	defer resp.Body.Close()
+	body, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return errors.ThrowInternal(err, "HTTP-HB432", "Errors.Internal")
+	}
+	if string(body) == verifier {
+		return nil
+	}
+	return errors.ThrowInvalidArgument(err, "HTTP-GH422", "Errors.Internal")
+}
+
+func ValidateDomainDNS(domain, verifier string) error {
+	txtRecords, err := net.LookupTXT(tokenUrlDNS(domain))
+	if err != nil {
+		return errors.ThrowInternal(err, "HTTP-Hwsw2", "Errors.Internal")
+	}
+
+	for _, record := range txtRecords {
+		if record == verifier {
+			return nil
+		}
+	}
+	return errors.ThrowInvalidArgument(err, "HTTP-G241f", "Errors.Internal")
+}
+
+func TokenUrl(domain, token string, checkType CheckType) (string, error) {
+	switch checkType {
+	case CheckTypeHTTP:
+		return tokenUrlHTTP(domain, token), nil
+	case CheckTypeDNS:
+		return tokenUrlDNS(domain), nil
+	default:
+		return "", errors.ThrowInvalidArgument(nil, "HTTP-Iqd11", "")
+	}
+}
+
+func tokenUrlHTTP(domain, token string) string {
+	return fmt.Sprintf(HTTPPattern, domain, token)
+}
+
+func tokenUrlDNS(domain string) string {
+	return fmt.Sprintf(DNSPattern, domain)
+}