package gemini import ( "bufio" "crypto/tls" "errors" "log" "net" "net/url" "strconv" "strings" "time" ) // 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 CertificateDir // CreateCertificate, if not nil, will be called to create a new certificate // if the current one is expired or missing. CreateCertificate 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[responderKey]Responder hosts map[string]bool } type responderKey struct { scheme string hostname string } // Register registers a responder for the given pattern. // // Patterns 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"). func (s *Server) Register(pattern string, responder Responder) { if pattern == "" { panic("gemini: invalid pattern") } if responder == nil { panic("gemini: nil responder") } if s.responders == nil { s.responders = map[responderKey]Responder{} s.hosts = map[string]bool{} } split := strings.SplitN(pattern, "://", 2) var key responderKey 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] = responder s.hosts[key.hostname] = true } // RegisterFunc registers a responder function for the given pattern. func (s *Server) RegisterFunc(pattern string, responder func(*ResponseWriter, *Request)) { s.Register(pattern, ResponderFunc(responder)) } // 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) } } func (s *Server) getCertificate(h *tls.ClientHelloInfo) (*tls.Certificate, error) { cert, err := s.getCertificateFor(h.ServerName) if err != nil { // Try wildcard wildcard := strings.SplitN(h.ServerName, ".", 2) if len(wildcard) == 2 { cert, err = s.getCertificateFor("*." + wildcard[1]) } } return cert, err } func (s *Server) getCertificateFor(hostname string) (*tls.Certificate, error) { if _, ok := s.hosts[hostname]; !ok { return nil, errors.New("hostname not registered") } // Generate a new certificate if it is missing or expired cert, ok := s.Certificates.Lookup(hostname) if !ok || cert.Leaf != nil && cert.Leaf.NotAfter.Before(time.Now()) { if s.CreateCertificate != nil { cert, err := s.CreateCertificate(hostname) if err == nil { s.Certificates.Add(hostname, cert) if err := s.Certificates.Write(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) { if d := s.ReadTimeout; d != 0 { conn.SetReadDeadline(time.Now().Add(d)) } if d := s.WriteTimeout; d != 0 { conn.SetWriteDeadline(time.Now().Add(d)) } r := bufio.NewReader(conn) w := newResponseWriter(conn) // Read requested URL rawurl, err := r.ReadString('\r') if err != nil { return } // Read terminating line feed if b, err := r.ReadByte(); err != nil { return } else if b != '\n' { w.WriteStatus(StatusBadRequest) } // Trim carriage return rawurl = rawurl[:len(rawurl)-1] // Ensure URL is valid if len(rawurl) > 1024 { w.WriteStatus(StatusBadRequest) } else if url, err := url.Parse(rawurl); err != nil || url.User != nil { // Note that we return an error status if User is specified in the URL w.WriteStatus(StatusBadRequest) } else { // Store information about the TLS connection var connState tls.ConnectionState var cert *tls.Certificate if tlsConn, ok := conn.(*tls.Conn); ok { connState = tlsConn.ConnectionState() if len(connState.PeerCertificates) > 0 { peerCert := connState.PeerCertificates[0] // Store the TLS certificate cert = &tls.Certificate{ Certificate: [][]byte{peerCert.Raw}, Leaf: peerCert, } } } req := &Request{ URL: url, RemoteAddr: conn.RemoteAddr(), TLS: connState, Certificate: cert, } resp := s.responder(req) if resp != nil { resp.Respond(w, req) } else { w.WriteStatus(StatusNotFound) } } w.b.Flush() conn.Close() } func (s *Server) responder(r *Request) Responder { if h, ok := s.responders[responderKey{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[responderKey{r.URL.Scheme, "*." + wildcard[1]}]; 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...) } } // ResponseWriter is used by a Gemini handler to construct a Gemini response. type ResponseWriter struct { b *bufio.Writer bodyAllowed bool wroteHeader bool mediatype string } func newResponseWriter(conn net.Conn) *ResponseWriter { return &ResponseWriter{ b: bufio.NewWriter(conn), } } // WriteHeader writes the response header. // If the header has already been written, WriteHeader does nothing. // // Meta contains more information related to the response status. // For successful responses, Meta should contain the mimetype of the response. // For failure responses, Meta should contain a short description of the failure. // Meta should not be longer than 1024 bytes. func (w *ResponseWriter) WriteHeader(status Status, meta string) { if w.wroteHeader { return } w.b.WriteString(strconv.Itoa(int(status))) w.b.WriteByte(' ') w.b.WriteString(meta) w.b.Write(crlf) // Only allow body to be written on successful status codes. if status.Class() == StatusClassSuccess { w.bodyAllowed = true } w.wroteHeader = true } // WriteStatus writes the response header with the given status code. // // WriteStatus is equivalent to WriteHeader(status, status.Message()) func (w *ResponseWriter) WriteStatus(status Status) { w.WriteHeader(status, status.Message()) } // SetMediaType sets the media type that will be written for a successful response. // If the mimetype is not set, it will default to "text/gemini". func (w *ResponseWriter) SetMediaType(mediatype string) { w.mediatype = mediatype } // Write writes the response body. // If the response status does not allow for a response body, Write returns // ErrBodyNotAllowed. // // If the response header has not yet been written, Write calls WriteHeader // with StatusSuccess and the mimetype set in SetMimetype. func (w *ResponseWriter) Write(b []byte) (int, error) { if !w.wroteHeader { mediatype := w.mediatype if mediatype == "" { mediatype = "text/gemini" } w.WriteHeader(StatusSuccess, mediatype) } if !w.bodyAllowed { return 0, ErrBodyNotAllowed } return w.b.Write(b) } // A Responder responds to a Gemini request. type Responder interface { // Respond accepts a Request and constructs a Response. Respond(*ResponseWriter, *Request) } // ResponderFunc is a wrapper around a bare function that implements Responder. type ResponderFunc func(*ResponseWriter, *Request) func (f ResponderFunc) Respond(w *ResponseWriter, r *Request) { f(w, r) }