go-gemini/server.go

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package gemini
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import (
"bufio"
"crypto/tls"
"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
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// Certificates contains the certificates used by the server.
Certificates CertificateStore
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// CreateCertificate, if not nil, will be called to create a new certificate
// if the current one is expired or missing.
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CreateCertificate func(hostname string) (tls.Certificate, error)
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// registered responders
responders map[responderKey]Responder
hosts map[string]bool
}
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type responderKey struct {
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scheme string
hostname string
}
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// Register registers a responder for the given pattern.
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//
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// 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").
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func (s *Server) Register(pattern string, responder Responder) {
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if pattern == "" {
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panic("gemini: invalid pattern")
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}
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if responder == nil {
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panic("gemini: nil responder")
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}
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if s.responders == nil {
s.responders = map[responderKey]Responder{}
s.hosts = map[string]bool{}
}
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split := strings.SplitN(pattern, "://", 2)
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var key responderKey
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if len(split) == 2 {
key.scheme = split[0]
key.hostname = split[1]
} else {
key.scheme = "gemini"
key.hostname = split[0]
}
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if _, ok := s.responders[key]; ok {
panic("gemini: multiple registrations for " + pattern)
}
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s.responders[key] = responder
s.hosts[key.hostname] = true
}
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// RegisterFunc registers a responder function for the given pattern.
func (s *Server) RegisterFunc(pattern string, responder func(*ResponseWriter, *Request)) {
s.Register(pattern, ResponderFunc(responder))
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}
// 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()
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return s.Serve(tls.NewListener(ln, &tls.Config{
ClientAuth: tls.RequestClientCert,
MinVersion: tls.VersionTLS12,
GetCertificate: s.getCertificate,
}))
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}
// 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
}
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log.Printf("gemini: Accept error: %v; retrying in %v", err, tempDelay)
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time.Sleep(tempDelay)
continue
}
// Otherwise, return the error
return err
}
tempDelay = 0
go s.respond(rw)
}
}
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func (s *Server) getCertificate(h *tls.ClientHelloInfo) (*tls.Certificate, error) {
cert, err := s.getCertificateFor(h.ServerName)
if err != nil {
// Try wildcard
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wildcard := strings.SplitN(h.ServerName, ".", 2)
if len(wildcard) == 2 {
cert, err = s.getCertificateFor("*." + wildcard[1])
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}
}
return cert, err
}
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func (s *Server) getCertificateFor(hostname string) (*tls.Certificate, error) {
if _, ok := s.hosts[hostname]; !ok {
return nil, ErrCertificateNotFound
}
cert, err := s.Certificates.Lookup(hostname)
switch err {
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case ErrCertificateNotFound, ErrCertificateExpired:
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if s.CreateCertificate != nil {
cert, err := s.CreateCertificate(hostname)
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if err == nil {
s.Certificates.Add(hostname, cert)
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}
return &cert, err
}
}
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return cert, err
}
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// 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))
}
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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' {
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w.WriteStatus(StatusBadRequest)
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}
// Trim carriage return
rawurl = rawurl[:len(rawurl)-1]
// Ensure URL is valid
if len(rawurl) > 1024 {
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w.WriteStatus(StatusBadRequest)
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} 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
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w.WriteStatus(StatusBadRequest)
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} else {
// If no scheme is specified, assume a default scheme of gemini://
if url.Scheme == "" {
url.Scheme = "gemini"
}
// Store information about the TLS connection
connState := conn.(*tls.Conn).ConnectionState()
var cert *tls.Certificate
if len(connState.PeerCertificates) > 0 {
peerCert := connState.PeerCertificates[0]
// Store the TLS certificate
cert = &tls.Certificate{
Certificate: [][]byte{peerCert.Raw},
Leaf: peerCert,
}
}
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req := &Request{
URL: url,
RemoteAddr: conn.RemoteAddr(),
TLS: connState,
Certificate: cert,
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}
resp := s.responder(req)
if resp != nil {
resp.Respond(w, req)
} else {
w.WriteStatus(StatusNotFound)
}
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}
w.b.Flush()
conn.Close()
}
func (s *Server) responder(r *Request) Responder {
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if h, ok := s.responders[responderKey{r.URL.Scheme, r.URL.Hostname()}]; ok {
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return h
}
wildcard := strings.SplitN(r.URL.Hostname(), ".", 2)
if len(wildcard) == 2 {
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if h, ok := s.responders[responderKey{r.URL.Scheme, "*." + wildcard[1]}]; ok {
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return h
}
}
return nil
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}
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// ResponseWriter is used by a Gemini handler to construct a Gemini response.
type ResponseWriter struct {
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b *bufio.Writer
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bodyAllowed bool
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wroteHeader bool
mimetype string
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}
func newResponseWriter(conn net.Conn) *ResponseWriter {
return &ResponseWriter{
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b: bufio.NewWriter(conn),
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}
}
// WriteHeader writes the response header.
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// If the header has already been written, WriteHeader does nothing.
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//
// 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) {
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if w.wroteHeader {
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return
}
w.b.WriteString(strconv.Itoa(int(status)))
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w.b.WriteByte(' ')
w.b.WriteString(meta)
w.b.Write(crlf)
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// Only allow body to be written on successful status codes.
if status.Class() == StatusClassSuccess {
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w.bodyAllowed = true
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}
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w.wroteHeader = true
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}
// WriteStatus writes the response header with the given status code.
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//
// WriteStatus is equivalent to WriteHeader(status, status.Message())
func (w *ResponseWriter) WriteStatus(status Status) {
w.WriteHeader(status, status.Message())
}
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// SetMimetype sets the mimetype that will be written for a successful response.
// If the mimetype is not set, it will default to "text/gemini".
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func (w *ResponseWriter) SetMimetype(mimetype string) {
w.mimetype = mimetype
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}
// Write writes the response body.
// If the response status does not allow for a response body, Write returns
// ErrBodyNotAllowed.
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//
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// If the response header has not yet been written, Write calls WriteHeader
// with StatusSuccess and the mimetype set in SetMimetype.
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func (w *ResponseWriter) Write(b []byte) (int, error) {
if !w.wroteHeader {
mimetype := w.mimetype
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if mimetype == "" {
mimetype = "text/gemini"
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}
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w.WriteHeader(StatusSuccess, mimetype)
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}
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if !w.bodyAllowed {
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return 0, ErrBodyNotAllowed
}
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return w.b.Write(b)
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}
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// A Responder responds to a Gemini request.
type Responder interface {
// Respond accepts a Request and constructs a Response.
Respond(*ResponseWriter, *Request)
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}
// 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)
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}
// Input returns the request query.
// If the query is invalid or no query is provided, ok will be false.
//
// Example:
//
// input, ok := gemini.Input(req)
// if !ok {
// w.WriteHeader(gemini.StatusInput, "Prompt")
// return
// }
// // ...
//
func Input(r *Request) (query string, ok bool) {
if r.URL.ForceQuery || r.URL.RawQuery != "" {
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query, err := url.QueryUnescape(r.URL.RawQuery)
return query, err == nil
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}
return "", false
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}