From cce3d79fc98a63052a9ccae2f2d28c6af422f35e Mon Sep 17 00:00:00 2001
From: xenolf <xenolf@users.noreply.github.com>
Date: Mon, 16 Nov 2015 23:57:41 +0100
Subject: [PATCH] Add DNS-01

---
 acme/dns_challenge.go | 86 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 86 insertions(+)

diff --git a/acme/dns_challenge.go b/acme/dns_challenge.go
index 8d2a213b..f519c6dc 100644
--- a/acme/dns_challenge.go
+++ b/acme/dns_challenge.go
@@ -1 +1,87 @@
 package acme
+
+import (
+	"bufio"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net/http"
+	"os"
+	"time"
+)
+
+const (
+	dnsTemplate = "_acme-challenge.%s. 300 IN TXT \"%s\""
+)
+
+// dnsChallenge implements the dns-01 challenge according to ACME 7.5
+type dnsChallenge struct {
+	jws *jws
+}
+
+func (s *dnsChallenge) Solve(chlng challenge, domain string) error {
+
+	logf("[INFO] acme: Trying to solve DNS-01")
+
+	// Generate the Key Authorization for the challenge
+	keyAuth, err := getKeyAuthorization(chlng.Token, &s.jws.privKey.PublicKey)
+	if err != nil {
+		return err
+	}
+
+	keyAuthShaBytes := sha256.Sum256([]byte(keyAuth))
+	// FIXME: Currently boulder does not conform to the spec as in it uses hex encoding instead
+	// of the base64 encoding mentioned by the spec. Fix this if either the spec or boulder changes!
+	keyAuthSha := hex.EncodeToString(keyAuthShaBytes[:sha256.Size])
+
+	dnsRecord := fmt.Sprintf(dnsTemplate, domain, keyAuthSha)
+	logf("[DEBUG] acme: DNS Record: %s", dnsRecord)
+
+	reader := bufio.NewReader(os.Stdin)
+	_, _ = reader.ReadString('\n')
+
+	jsonBytes, err := json.Marshal(challenge{Resource: "challenge", Type: chlng.Type, Token: chlng.Token, KeyAuthorization: keyAuth})
+	if err != nil {
+		return errors.New("Failed to marshal network message...")
+	}
+
+	// Tell the server we handle DNS-01
+	resp, err := s.jws.post(chlng.URI, jsonBytes)
+	if err != nil {
+		return fmt.Errorf("Failed to post JWS message. -> %v", err)
+	}
+
+	// Repeatedly check the server for an updated status on our request.
+	var challengeResponse challenge
+Loop:
+	for {
+		if resp.StatusCode >= http.StatusBadRequest {
+			return handleHTTPError(resp)
+		}
+
+		err = json.NewDecoder(resp.Body).Decode(&challengeResponse)
+		resp.Body.Close()
+		if err != nil {
+			return err
+		}
+
+		switch challengeResponse.Status {
+		case "valid":
+			logf("The server validated our request")
+			break Loop
+		case "pending":
+			break
+		case "invalid":
+			return errors.New("The server could not validate our request.")
+		default:
+			return errors.New("The server returned an unexpected state.")
+		}
+
+		time.Sleep(1 * time.Second)
+		resp, err = http.Get(chlng.URI)
+	}
+
+	return nil
+}