From c74c212bdfbae4ce66a711d6dc17f22a4cd7be5e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ond=C5=99ej=20Benkovsk=C3=BD?= <ondrej.benkovsky@jamf.com>
Date: Fri, 2 Jun 2023 15:33:34 +0200
Subject: [PATCH] prevent panics when using DoHWriter (#6120)
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Signed-off-by: Ondřej Benkovský <ondrej.benkovsky@jamf.com>
---
 core/dnsserver/https.go | 51 ++++++++++++++++++++++++++++++++++-------
 1 file changed, 43 insertions(+), 8 deletions(-)

diff --git a/core/dnsserver/https.go b/core/dnsserver/https.go
index 382e06efe..015c52ec5 100644
--- a/core/dnsserver/https.go
+++ b/core/dnsserver/https.go
@@ -4,13 +4,11 @@ import (
 	"net"
 	"net/http"
 
-	"github.com/coredns/coredns/plugin/pkg/nonwriter"
+	"github.com/miekg/dns"
 )
 
-// DoHWriter is a nonwriter.Writer that adds more specific LocalAddr and RemoteAddr methods.
+// DoHWriter is a dns.ResponseWriter that adds more specific LocalAddr and RemoteAddr methods.
 type DoHWriter struct {
-	nonwriter.Writer
-
 	// raddr is the remote's address. This can be optionally set.
 	raddr net.Addr
 	// laddr is our address. This can be optionally set.
@@ -18,13 +16,50 @@ type DoHWriter struct {
 
 	// request is the HTTP request we're currently handling.
 	request *http.Request
+
+	// Msg is a response to be written to the client.
+	Msg *dns.Msg
+}
+
+// WriteMsg stores the message to be written to the client.
+func (d *DoHWriter) WriteMsg(m *dns.Msg) error {
+	d.Msg = m
+	return nil
+}
+
+// Write stores the message to be written to the client.
+func (d *DoHWriter) Write(b []byte) (int, error) {
+	d.Msg = new(dns.Msg)
+	return len(b), d.Msg.Unpack(b)
 }
 
 // RemoteAddr returns the remote address.
-func (d *DoHWriter) RemoteAddr() net.Addr { return d.raddr }
+func (d *DoHWriter) RemoteAddr() net.Addr {
+	return d.raddr
+}
 
 // LocalAddr returns the local address.
-func (d *DoHWriter) LocalAddr() net.Addr { return d.laddr }
+func (d *DoHWriter) LocalAddr() net.Addr {
+	return d.laddr
+}
 
-// Request returns the HTTP request
-func (d *DoHWriter) Request() *http.Request { return d.request }
+// Request returns the HTTP request.
+func (d *DoHWriter) Request() *http.Request {
+	return d.request
+}
+
+// Close no-op implementation.
+func (d *DoHWriter) Close() error {
+	return nil
+}
+
+// TsigStatus no-op implementation.
+func (d *DoHWriter) TsigStatus() error {
+	return nil
+}
+
+// TsigTimersOnly no-op implementation.
+func (d *DoHWriter) TsigTimersOnly(_ bool) {}
+
+// Hijack no-op implementation.
+func (d *DoHWriter) Hijack() {}