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package dnsserver
import (
"context"
"crypto/tls"
"fmt"
stdlog "log"
"net"
"net/http"
"strconv"
"time"
"github.com/coredns/caddy"
"github.com/coredns/coredns/plugin/metrics/vars"
"github.com/coredns/coredns/plugin/pkg/dnsutil"
"github.com/coredns/coredns/plugin/pkg/doh"
clog "github.com/coredns/coredns/plugin/pkg/log"
"github.com/coredns/coredns/plugin/pkg/response"
"github.com/coredns/coredns/plugin/pkg/reuseport"
"github.com/coredns/coredns/plugin/pkg/transport"
)
// ServerHTTPS represents an instance of a DNS-over-HTTPS server.
type ServerHTTPS struct {
*Server
httpsServer *http.Server
listenAddr net.Addr
tlsConfig *tls.Config
validRequest func(*http.Request) bool
}
// loggerAdapter is a simple adapter around CoreDNS logger made to implement io.Writer in order to log errors from HTTP server
type loggerAdapter struct {
}
func (l *loggerAdapter) Write(p []byte) (n int, err error) {
clog.Debug(string(p))
return len(p), nil
}
// HTTPRequestKey is the context key for the current processed HTTP request (if current processed request was done over DOH)
type HTTPRequestKey struct{}
// NewServerHTTPS returns a new CoreDNS HTTPS server and compiles all plugins in to it.
func NewServerHTTPS(addr string, group []*Config) (*ServerHTTPS, error) {
s, err := NewServer(addr, group)
if err != nil {
return nil, err
}
// The *tls* plugin must make sure that multiple conflicting
// TLS configuration returns an error: it can only be specified once.
var tlsConfig *tls.Config
for _, z := range s.zones {
for _, conf := range z {
// Should we error if some configs *don't* have TLS?
tlsConfig = conf.TLSConfig
}
}
// http/2 is recommended when using DoH. We need to specify it in next protos
// or the upgrade won't happen.
if tlsConfig != nil {
tlsConfig.NextProtos = []string{"h2", "http/1.1"}
}
// Use a custom request validation func or use the standard DoH path check.
var validator func(*http.Request) bool
for _, z := range s.zones {
for _, conf := range z {
validator = conf.HTTPRequestValidateFunc
}
}
if validator == nil {
validator = func(r *http.Request) bool { return r.URL.Path == doh.Path }
}
srv := &http.Server{
ReadTimeout: s.readTimeout,
WriteTimeout: s.writeTimeout,
IdleTimeout: s.idleTimeout,
ErrorLog: stdlog.New(&loggerAdapter{}, "", 0),
}
sh := &ServerHTTPS{
Server: s, tlsConfig: tlsConfig, httpsServer: srv, validRequest: validator,
}
sh.httpsServer.Handler = sh
return sh, nil
}
// Compile-time check to ensure Server implements the caddy.GracefulServer interface
var _ caddy.GracefulServer = &Server{}
// Serve implements caddy.TCPServer interface.
func (s *ServerHTTPS) Serve(l net.Listener) error {
s.m.Lock()
s.listenAddr = l.Addr()
s.m.Unlock()
if s.tlsConfig != nil {
l = tls.NewListener(l, s.tlsConfig)
}
return s.httpsServer.Serve(l)
}
// ServePacket implements caddy.UDPServer interface.
func (s *ServerHTTPS) ServePacket(p net.PacketConn) error { return nil }
// Listen implements caddy.TCPServer interface.
func (s *ServerHTTPS) Listen() (net.Listener, error) {
l, err := reuseport.Listen("tcp", s.Addr[len(transport.HTTPS+"://"):])
if err != nil {
return nil, err
}
return l, nil
}
// ListenPacket implements caddy.UDPServer interface.
func (s *ServerHTTPS) ListenPacket() (net.PacketConn, error) { return nil, nil }
// OnStartupComplete lists the sites served by this server
// and any relevant information, assuming Quiet is false.
func (s *ServerHTTPS) OnStartupComplete() {
if Quiet {
return
}
out := startUpZones(transport.HTTPS+"://", s.Addr, s.zones)
if out != "" {
fmt.Print(out)
}
}
// Stop stops the server. It blocks until the server is totally stopped.
func (s *ServerHTTPS) Stop() error {
s.m.Lock()
defer s.m.Unlock()
if s.httpsServer != nil {
s.httpsServer.Shutdown(context.Background())
}
return nil
}
// ServeHTTP is the handler that gets the HTTP request and converts to the dns format, calls the plugin
// chain, converts it back and write it to the client.
func (s *ServerHTTPS) ServeHTTP(w http.ResponseWriter, r *http.Request) {
if !s.validRequest(r) {
http.Error(w, "", http.StatusNotFound)
s.countResponse(http.StatusNotFound)
return
}
msg, err := doh.RequestToMsg(r)
if err != nil {
http.Error(w, err.Error(), http.StatusBadRequest)
s.countResponse(http.StatusBadRequest)
return
}
// Create a DoHWriter with the correct addresses in it.
h, p, _ := net.SplitHostPort(r.RemoteAddr)
port, _ := strconv.Atoi(p)
dw := &DoHWriter{
laddr: s.listenAddr,
raddr: &net.TCPAddr{IP: net.ParseIP(h), Port: port},
request: r,
}
// We just call the normal chain handler - all error handling is done there.
// We should expect a packet to be returned that we can send to the client.
ctx := context.WithValue(context.Background(), Key{}, s.Server)
ctx = context.WithValue(ctx, LoopKey{}, 0)
ctx = context.WithValue(ctx, HTTPRequestKey{}, r)
s.ServeDNS(ctx, dw, msg)
// See section 4.2.1 of RFC 8484.
// We are using code 500 to indicate an unexpected situation when the chain
// handler has not provided any response message.
if dw.Msg == nil {
http.Error(w, "No response", http.StatusInternalServerError)
s.countResponse(http.StatusInternalServerError)
return
}
buf, _ := dw.Msg.Pack()
mt, _ := response.Typify(dw.Msg, time.Now().UTC())
age := dnsutil.MinimalTTL(dw.Msg, mt)
w.Header().Set("Content-Type", doh.MimeType)
w.Header().Set("Cache-Control", fmt.Sprintf("max-age=%f", age.Seconds()))
w.Header().Set("Content-Length", strconv.Itoa(len(buf)))
w.WriteHeader(http.StatusOK)
s.countResponse(http.StatusOK)
w.Write(buf)
}
func (s *ServerHTTPS) countResponse(status int) {
vars.HTTPSResponsesCount.WithLabelValues(s.Addr, strconv.Itoa(status)).Inc()
}
// Shutdown stops the server (non gracefully).
func (s *ServerHTTPS) Shutdown() error {
if s.httpsServer != nil {
s.httpsServer.Shutdown(context.Background())
}
return nil
}
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