package gemini import ( "crypto/tls" "errors" "log" "net" "strings" "time" "git.sr.ht/~adnano/go-gemini/certificate" ) // Server is a Gemini server. type Server struct { // Addr specifies the address that the server should listen on. // If Addr is empty, the server will listen on the address ":1965". Addr string // ReadTimeout is the maximum duration for reading a request. ReadTimeout time.Duration // WriteTimeout is the maximum duration before timing out // writes of the response. WriteTimeout time.Duration // Certificates contains the certificates used by the server. Certificates certificate.Dir // GetCertificate, if not nil, will be called to retrieve a new certificate // if the current one is expired or missing. GetCertificate func(hostname string) (tls.Certificate, error) // ErrorLog specifies an optional logger for errors accepting connections // and file system errors. // If nil, logging is done via the log package's standard logger. ErrorLog *log.Logger // registered responders responders map[handlerKey]Handler hosts map[string]bool } type handlerKey struct { scheme string hostname string } // Handle registers the handler for the given pattern. // If a handler already exists for pattern, Handle panics. // // The pattern must be in the form of "hostname" or "scheme://hostname". // If no scheme is specified, a scheme of "gemini://" is implied. // Wildcard patterns are supported (e.g. "*.example.com"). // To handle any hostname, use the wildcard pattern "*". func (s *Server) Handle(pattern string, handler Handler) { if pattern == "" { panic("gemini: invalid pattern") } if handler == nil { panic("gemini: nil responder") } if s.responders == nil { s.responders = map[handlerKey]Handler{} s.hosts = map[string]bool{} } split := strings.SplitN(pattern, "://", 2) var key handlerKey if len(split) == 2 { key.scheme = split[0] key.hostname = split[1] } else { key.scheme = "gemini" key.hostname = split[0] } if _, ok := s.responders[key]; ok { panic("gemini: multiple registrations for " + pattern) } s.responders[key] = handler s.hosts[key.hostname] = true } // HandleFunc registers the handler function for the given pattern. func (s *Server) HandleFunc(pattern string, handler func(ResponseWriter, *Request)) { s.Handle(pattern, HandlerFunc(handler)) } // ListenAndServe listens for requests at the server's configured address. func (s *Server) ListenAndServe() error { addr := s.Addr if addr == "" { addr = ":1965" } ln, err := net.Listen("tcp", addr) if err != nil { return err } defer ln.Close() return s.Serve(tls.NewListener(ln, &tls.Config{ ClientAuth: tls.RequestClientCert, MinVersion: tls.VersionTLS12, GetCertificate: s.getCertificate, })) } // Serve listens for requests on the provided listener. func (s *Server) Serve(l net.Listener) error { var tempDelay time.Duration // how long to sleep on accept failure for { rw, err := l.Accept() if err != nil { // If this is a temporary error, sleep if ne, ok := err.(net.Error); ok && ne.Temporary() { if tempDelay == 0 { tempDelay = 5 * time.Millisecond } else { tempDelay *= 2 } if max := 1 * time.Second; tempDelay > max { tempDelay = max } s.logf("gemini: Accept error: %v; retrying in %v", err, tempDelay) time.Sleep(tempDelay) continue } // Otherwise, return the error return err } tempDelay = 0 go s.respond(rw) } } // getCertificate retrieves a certificate for the given client hello. func (s *Server) getCertificate(h *tls.ClientHelloInfo) (*tls.Certificate, error) { cert, err := s.lookupCertificate(h.ServerName, h.ServerName) if err != nil { // Try wildcard wildcard := strings.SplitN(h.ServerName, ".", 2) if len(wildcard) == 2 { // Use the wildcard pattern as the hostname. hostname := "*." + wildcard[1] cert, err = s.lookupCertificate(hostname, hostname) } // Try "*" wildcard if err != nil { // Use the server name as the hostname // since "*" is not a valid hostname. cert, err = s.lookupCertificate("*", h.ServerName) } } return cert, err } // lookupCertificate retrieves the certificate for the given hostname, // if and only if the provided pattern is registered. // If no certificate is found in the certificate store or the certificate // is expired, it calls GetCertificate to retrieve a new certificate. func (s *Server) lookupCertificate(pattern, hostname string) (*tls.Certificate, error) { if _, ok := s.hosts[pattern]; !ok { return nil, errors.New("hostname not registered") } cert, ok := s.Certificates.Lookup(hostname) if !ok || cert.Leaf != nil && cert.Leaf.NotAfter.Before(time.Now()) { if s.GetCertificate != nil { cert, err := s.GetCertificate(hostname) if err == nil { if err := s.Certificates.Add(hostname, cert); err != nil { s.logf("gemini: Failed to write new certificate for %s: %s", hostname, err) } } return &cert, err } return nil, errors.New("no certificate") } return &cert, nil } // respond responds to a connection. func (s *Server) respond(conn net.Conn) { defer conn.Close() if d := s.ReadTimeout; d != 0 { _ = conn.SetReadDeadline(time.Now().Add(d)) } if d := s.WriteTimeout; d != 0 { _ = conn.SetWriteDeadline(time.Now().Add(d)) } w := NewResponseWriter(conn) defer func() { _ = w.Flush() }() req, err := ReadRequest(conn) if err != nil { w.Status(StatusBadRequest) return } // Store information about the TLS connection if tlsConn, ok := conn.(*tls.Conn); ok { state := tlsConn.ConnectionState() req.TLS = &state if len(req.TLS.PeerCertificates) > 0 { peerCert := req.TLS.PeerCertificates[0] // Store the TLS certificate req.Certificate = &tls.Certificate{ Certificate: [][]byte{peerCert.Raw}, Leaf: peerCert, } } } resp := s.responder(req) if resp == nil { w.Status(StatusNotFound) return } resp.ServeGemini(w, req) } func (s *Server) responder(r *Request) Handler { if h, ok := s.responders[handlerKey{r.URL.Scheme, r.URL.Hostname()}]; ok { return h } wildcard := strings.SplitN(r.URL.Hostname(), ".", 2) if len(wildcard) == 2 { if h, ok := s.responders[handlerKey{r.URL.Scheme, "*." + wildcard[1]}]; ok { return h } } if h, ok := s.responders[handlerKey{r.URL.Scheme, "*"}]; ok { return h } return nil } func (s *Server) logf(format string, args ...interface{}) { if s.ErrorLog != nil { s.ErrorLog.Printf(format, args...) } else { log.Printf(format, args...) } } // A Handler responds to a Gemini request. // // ServeGemini should write the response header and data to the ResponseWriter // and then return. type Handler interface { ServeGemini(ResponseWriter, *Request) } // The HandlerFunc type is an adapter to allow the use of ordinary functions // as Gemini handlers. If f is a function with the appropriate signature, // HandlerFunc(f) is a Handler that calls f. type HandlerFunc func(ResponseWriter, *Request) // ServeGemini calls f(w, r). func (f HandlerFunc) ServeGemini(w ResponseWriter, r *Request) { f(w, r) }