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package server
import (
"encoding/base64"
"io"
"log/slog"
"net/http"
"codeberg.org/miekg/dns"
"linum/internal/cache"
)
func decodeDNSParam(s string) ([]byte, error) {
if b, err := base64.RawURLEncoding.DecodeString(s); err == nil {
return b, nil
}
return base64.URLEncoding.DecodeString(s)
}
func (s *Server) dohHandler(w http.ResponseWriter, r *http.Request) {
clientIP := parseHTTPClientIP(r.RemoteAddr)
if !s.isAllowed(clientIP) {
slog.Warn("doh query denied by ACL", "client", clientIP)
http.Error(w, "refused", http.StatusForbidden)
return
}
if !s.rateLimit(clientIP.String()) {
slog.Warn("doh query rate limited", "client", clientIP)
http.Error(w, "too many requests", http.StatusTooManyRequests)
return
}
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 := decodeDNSParam(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)
msg.Data = raw
if err := msg.Unpack(); err != nil {
http.Error(w, "invalid dns message", http.StatusBadRequest)
return
}
if len(msg.Question) == 0 {
http.Error(w, "no question", http.StatusBadRequest)
return
}
q := msg.Question[0]
qname := q.Header().Name
qtype := dns.RRToType(q)
qclass := q.Header().Class
if s.blocklist != nil && s.blocklist.IsBlocked(qname) {
httpWriteMsg(w, s.blockedResponse(msg))
slog.Debug("doh query served",
"qname", qname,
"qtype", dns.TypeToString[qtype],
"blocked", true,
)
return
}
if s.cache != nil {
key := cache.Key{Name: qname, Qtype: qtype, Class: qclass}
if packed, ok := s.cache.Get(key); ok {
packed[0] = byte(msg.ID >> 8)
packed[1] = byte(msg.ID)
w.Header().Set("Content-Type", "application/dns-message")
w.Header().Set("Cache-Control", "no-cache, max-age=0")
w.Write(packed)
slog.Debug("doh query served",
"qname", qname,
"qtype", dns.TypeToString[qtype],
"cached", true,
)
return
}
}
resp, _ := s.buildResponse(msg)
httpWriteMsg(w, resp)
slog.Debug("doh query served",
"qname", qname,
"qtype", dns.TypeToString[qtype],
"rcode", dns.RcodeToString[resp.Rcode],
)
}
func httpWriteMsg(w http.ResponseWriter, msg *dns.Msg) {
if err := msg.Pack(); 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(msg.Data); err != nil {
slog.Error("doh write failed", "err", err)
}
}
|
