commit cea86c937dc278ba6b2100c238b1d5206bbae2f0 Author: David Fifield david@bamsoftware.com Date: Tue Apr 11 22:18:47 2017 -0700
Use ListenAndServe{TLS} rather than separate Listen and Serve.
The net/http package provides ListenAndServe and ListenAndServeTLS functions, but it doesn't provide a way to set up a listener without also entering an infinite serve loop. This matters for ListenAndServeTLS, which sets up a lot of magic behind the scenes for TLS and HTTP/2 support. Formerly, we had copy-pasted code from ListenAndServeTLS, but that code has only gotten more complicated in upstream net/http.
The price we pay for this is that it's no longer possible for a server bindaddr to ask to listen on port 0 (i.e., a random ephemeral port). That's because we never get a change to find out what the listening address is, before entering the serve loop.
What we gain is HTTP/2 support; formerly our copy-pasted code had the side effect of disabling HTTP/2, because it was copied from an older version and did things like config.NextProtos = []string{"http/1.1"}
The new code calls http2.ConfigureServer first, but that's not what's providing HTTP/2 support. HTTP/2 support happens by default. The reason we call http2.ConfigureServer is because we need to set TLSConfig.GetCertificate, and http2.ConfigureServer is a convenient way to initialize TLSConfig in a way that is guaranteed to work with HTTP/2. --- meek-server/meek-server.go | 116 +++++++++++++++++++++++---------------------- 1 file changed, 60 insertions(+), 56 deletions(-)
diff --git a/meek-server/meek-server.go b/meek-server/meek-server.go index 2b49897..dcb0c5c 100644 --- a/meek-server/meek-server.go +++ b/meek-server/meek-server.go @@ -38,6 +38,7 @@ import (
"git.torproject.org/pluggable-transports/goptlib.git" "golang.org/x/crypto/acme/autocert" + "golang.org/x/net/http2" )
const ( @@ -273,65 +274,65 @@ func (state *State) ExpireSessions() { } }
-func listenTLS(network string, addr *net.TCPAddr, getCertificate func(*tls.ClientHelloInfo) (*tls.Certificate, error)) (net.Listener, error) { - // This is cribbed from the source of net/http.Server.ListenAndServeTLS. - // We have to separate the Listen and Serve parts because we need to - // report the listening address before entering Serve (which is an - // infinite loop). +func initServer(addr *net.TCPAddr, + getCertificate func(*tls.ClientHelloInfo) (*tls.Certificate, error), + listenAndServe func(*http.Server)) (*http.Server, error) { + // We're not capable of listening on port 0 (i.e., an ephemeral port + // unknown in advance). The reason is that while the net/http package + // exposes ListenAndServe and ListenAndServeTLS, those functions never + // return, so there's no opportunity to find out what the port number + // is, in between the Listen and Serve steps. // https://groups.google.com/d/msg/Golang-nuts/3F1VRCCENp8/3hcayZiwYM8J - config := &tls.Config{} - config.NextProtos = []string{"http/1.1"} - config.GetCertificate = getCertificate - - conn, err := net.ListenTCP(network, addr) - if err != nil { - return nil, err - } - - // Additionally disable SSLv3 because of the POODLE attack. - // http://googleonlinesecurity.blogspot.com/2014/10/this-poodle-bites-exploitin... - // https://code.google.com/p/go/source/detail?r=ad9e191a51946e43f1abac8b6a2fefb... - config.MinVersion = tls.VersionTLS10 - - tlsListener := tls.NewListener(conn, config) - - return tlsListener, nil -} - -func startListener(network string, addr *net.TCPAddr) (net.Listener, error) { - ln, err := net.ListenTCP(network, addr) - if err != nil { - return nil, err + if addr.Port == 0 { + return nil, fmt.Errorf("cannot listen on port %d; configure a port using ServerTransportListenAddr", addr.Port) } - log.Printf("listening with plain HTTP on %s", ln.Addr()) - return startServer(ln) -} - -func startListenerTLS(network string, addr *net.TCPAddr, getCertificate func(*tls.ClientHelloInfo) (*tls.Certificate, error)) (net.Listener, error) { - ln, err := listenTLS(network, addr, getCertificate) - if err != nil { - return nil, err - } - log.Printf("listening with HTTPS on %s", ln.Addr()) - return startServer(ln) -}
-func startServer(ln net.Listener) (net.Listener, error) { state := NewState() go state.ExpireSessions() + server := &http.Server{ + Addr: addr.String(), Handler: state, ReadTimeout: readWriteTimeout, WriteTimeout: readWriteTimeout, } - go func() { - defer ln.Close() - err := server.Serve(ln) + // We need to override server.TLSConfig.GetCertificate--but first + // server.TLSConfig needs to be non-nil. If we just create our own new + // &tls.Config, it will lack the default settings that the net/http + // package sets up for things like HTTP/2. Therefore we first call + // http2.ConfigureServer for its side effect of initializing + // server.TLSConfig properly. An alternative would be to make a dummy + // net.Listener, call Serve on it, and let it return. + // https://github.com/golang/go/issues/16588#issuecomment-237386446 + err := http2.ConfigureServer(server, nil) + if err != nil { + return server, err + } + server.TLSConfig.GetCertificate = getCertificate + + go listenAndServe(server) + + return server, nil +} + +func startServer(addr *net.TCPAddr) (*http.Server, error) { + return initServer(addr, nil, func(server *http.Server) { + log.Printf("listening with plain HTTP on %s", addr) + err := server.ListenAndServe() if err != nil { - log.Printf("Error in Serve: %s", err) + log.Printf("Error in ListenAndServe: %s", err) } - }() - return ln, nil + }) +} + +func startServerTLS(addr *net.TCPAddr, getCertificate func(*tls.ClientHelloInfo) (*tls.Certificate, error)) (*http.Server, error) { + return initServer(addr, getCertificate, func(server *http.Server) { + log.Printf("listening with HTTPS on %s", addr) + err := server.ListenAndServeTLS("", "") + if err != nil { + log.Printf("Error in ListenAndServeTLS: %s", err) + } + }) }
func getCertificateCacheDir() (string, error) { @@ -438,7 +439,7 @@ func main() { }
log.Printf("starting version %s (%s)", programVersion, runtime.Version()) - listeners := make([]net.Listener, 0) + servers := make([]*http.Server, 0) for _, bindaddr := range ptInfo.Bindaddrs { if port != 0 { bindaddr.Addr.Port = port @@ -449,18 +450,18 @@ func main() { pt.SmethodError(bindaddr.MethodName, "The --acme-hostnames option requires one of the bindaddrs to be on port 443.") break } - var ln net.Listener + var server *http.Server if disableTLS { - ln, err = startListener("tcp", bindaddr.Addr) + server, err = startServer(bindaddr.Addr) } else { - ln, err = startListenerTLS("tcp", bindaddr.Addr, getCertificate) + server, err = startServerTLS(bindaddr.Addr, getCertificate) } if err != nil { pt.SmethodError(bindaddr.MethodName, err.Error()) break } - pt.Smethod(bindaddr.MethodName, ln.Addr()) - listeners = append(listeners, ln) + pt.Smethod(bindaddr.MethodName, bindaddr.Addr) + servers = append(servers, server) default: pt.SmethodError(bindaddr.MethodName, "no such method") } @@ -482,9 +483,12 @@ func main() { log.Printf("got signal %s", sig) } } - for _, ln := range listeners { - ln.Close() - } + /* + // Not supported until go1.8. + for _, server := range servers { + server.Close() + } + */
if sig == syscall.SIGTERM { log.Printf("done")