dns codec, udp server (reuseport, 4096 buffers), tcp server, doh listener post get without tls, concurrent, ends0, fuzz)

1 files changed, 75 insertions, 0 deletions

diff --git a/internal/server/doh.go b/internal/server/doh.go
new file mode 100644
index 0000000..e9cf466
--- /dev/null
+++ b/internal/server/doh.go
@@ -0,0 +1,75 @@
+package server
+
+import (
+	"encoding/base64"
+	"github.com/miekg/dns"
+	"io"
+	"log/slog"
+	"net/http"
+)
+
+func (s *Server) dohHandler(w http.ResponseWriter, r *http.Request) {
+	var raw []byte
+
+	switch r.Method {
+	case http.MethodPost:
+		ct := r.Header.Get("Content-Type")
+		if ct != "application/dns-message" {
+			http.Error(w, "unsupported content type", http.StatusUnsupportedMediaType)
+			return
+		}
+		body, err := io.ReadAll(http.MaxBytesReader(w, r.Body, 65535))
+		if err != nil {
+			http.Error(w, "read body", http.StatusBadRequest)
+			return
+		}
+		raw = body
+	case http.MethodGet:
+		param := r.URL.Query().Get("dns")
+		if param == "" {
+			http.Error(w, "missing dns param", http.StatusBadRequest)
+			return
+		}
+		decoded, err := base64.RawURLEncoding.DecodeString(param)
+		if err != nil {
+			http.Error(w, "invalid base64url", http.StatusBadRequest)
+			return
+		}
+		raw = decoded
+	default:
+		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
+		return
+	}
+
+	msg := new(dns.Msg)
+	if err := msg.Unpack(raw); err != nil {
+		http.Error(w, "invalid dns message", http.StatusBadRequest)
+		return
+	}
+
+	if len(msg.Question) == 0 {
+		http.Error(w, "no question", http.StatusBadRequest)
+		return
+	}
+
+	resp := buildResponse(msg)
+	packed, err := resp.Pack()
+	if err != nil {
+		http.Error(w, "pack response", http.StatusInternalServerError)
+		return
+	}
+
+	w.Header().Set("Content-Type", "application/dns-message")
+	w.Header().Set("Cache-Control", "no-cache, max-age=0")
+	if _, err := w.Write(packed); err != nil {
+		slog.Error("doh write failed", "err", err)
+		return
+	}
+
+	slog.Info("doh query served",
+		"qname", msg.Question[0].Name,
+		"qtype", dns.TypeToString[msg.Question[0].Qtype],
+		"rcode", dns.RcodeToString[resp.Rcode],
+		"client", r.RemoteAddr,
+	)
+}