go-gemini/server.go
2020-10-24 15:15:32 -04:00

531 lines
15 KiB
Go

package gemini
import (
"bufio"
"crypto/tls"
"crypto/x509"
"log"
"net"
"net/url"
"path"
"sort"
"strconv"
"strings"
"sync"
"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
// CertificateStore contains the certificates used by the server.
CertificateStore CertificateStore
// GetCertificate, if not nil, will be called to retrieve the certificate
// to use for a given hostname.
// If the certificate is nil, the connection will be aborted.
GetCertificate func(hostname string, store *CertificateStore) *tls.Certificate
// registered responders
responders map[responderKey]Responder
}
type responderKey struct {
scheme string
hostname string
wildcard bool
}
// Register registers a responder for the given pattern.
// Patterns must be in the form of scheme://hostname (e.g. gemini://example.com).
// If no scheme is specified, a default scheme of gemini:// is assumed.
// 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{}
}
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]
}
split = strings.SplitN(key.hostname, ".", 2)
if len(split) == 2 && split[0] == "*" {
key.hostname = split[1]
key.wildcard = true
}
s.responders[key] = responder
}
// 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()
config := &tls.Config{
ClientAuth: tls.RequestClientCert,
MinVersion: tls.VersionTLS12,
GetCertificate: func(h *tls.ClientHelloInfo) (*tls.Certificate, error) {
if s.GetCertificate != nil {
return s.GetCertificate(h.ServerName, &s.CertificateStore), nil
}
return s.CertificateStore.Lookup(h.ServerName)
},
}
tlsListener := tls.NewListener(ln, config)
return s.Serve(tlsListener)
}
// 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
}
log.Printf("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)
}
}
// respond responds to a connection.
func (s *Server) respond(conn net.Conn) {
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.WriteHeader(StatusBadRequest, "Bad request")
}
// Trim carriage return
rawurl = rawurl[:len(rawurl)-1]
// Ensure URL is valid
if len(rawurl) > 1024 {
w.WriteHeader(StatusBadRequest, "Bad request")
} 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.WriteHeader(StatusBadRequest, "Bad request")
} else {
// If no scheme is specified, assume a default scheme of gemini://
if url.Scheme == "" {
url.Scheme = "gemini"
}
req := &Request{
URL: url,
RemoteAddr: conn.RemoteAddr(),
TLS: conn.(*tls.Conn).ConnectionState(),
}
s.responder(req).Respond(w, req)
}
w.b.Flush()
conn.Close()
}
func (s *Server) responder(r *Request) Responder {
if h, ok := s.responders[responderKey{r.URL.Scheme, r.URL.Hostname(), false}]; 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], true}]; ok {
return h
}
}
return ResponderFunc(NotFound)
}
// ResponseWriter is used by a Gemini handler to construct a Gemini response.
type ResponseWriter struct {
b *bufio.Writer
bodyAllowed bool
wroteHeader bool
mimetype 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 int, meta string) {
if w.wroteHeader {
return
}
w.b.WriteString(strconv.Itoa(status))
w.b.WriteByte(' ')
w.b.WriteString(meta)
w.b.Write(crlf)
// Only allow body to be written on successful status codes.
if status/10 == StatusClassSuccess {
w.bodyAllowed = true
}
w.wroteHeader = true
}
// SetMimetype sets the mimetype that will be written for a successful response.
// The provided mimetype will only be used if Write is called without calling
// WriteHeader.
// If the mimetype is not set, it will default to "text/gemini".
func (w *ResponseWriter) SetMimetype(mimetype string) {
w.mimetype = mimetype
}
// Write writes the response body.
// If the response status does not allow for a response body, Write returns
// ErrBodyNotAllowed.
//
// If WriteHeader has not yet been called, Write calls
// WriteHeader(StatusSuccess, mimetype) where mimetype is the mimetype set in
// SetMimetype. If no mimetype is set, a default of "text/gemini" will be used.
func (w *ResponseWriter) Write(b []byte) (int, error) {
if !w.wroteHeader {
mimetype := w.mimetype
if mimetype == "" {
mimetype = "text/gemini"
}
w.WriteHeader(StatusSuccess, mimetype)
}
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)
}
// Input returns the request query.
// If no input is provided, it responds with StatusInput.
func Input(w *ResponseWriter, r *Request, prompt string) (string, bool) {
if r.URL.ForceQuery || r.URL.RawQuery != "" {
return r.URL.RawQuery, true
}
w.WriteHeader(StatusInput, prompt)
return "", false
}
// SensitiveInput returns the request query.
// If no input is provided, it responds with StatusSensitiveInput.
func SensitiveInput(w *ResponseWriter, r *Request, prompt string) (string, bool) {
if r.URL.ForceQuery || r.URL.RawQuery != "" {
return r.URL.RawQuery, true
}
w.WriteHeader(StatusSensitiveInput, prompt)
return "", false
}
// Redirect replies to the request with a redirect to the given URL.
func Redirect(w *ResponseWriter, r *Request, url string) {
w.WriteHeader(StatusRedirect, url)
}
// PermanentRedirect replies to the request with a permanent redirect to the given URL.
func PermanentRedirect(w *ResponseWriter, r *Request, url string) {
w.WriteHeader(StatusRedirectPermanent, url)
}
// NotFound replies to the request with the NotFound status code.
func NotFound(w *ResponseWriter, r *Request) {
w.WriteHeader(StatusNotFound, "Not found")
}
// Gone replies to the request with the Gone status code.
func Gone(w *ResponseWriter, r *Request) {
w.WriteHeader(StatusGone, "Gone")
}
// CertificateRequired responds to the request with the CertificateRequired
// status code.
func CertificateRequired(w *ResponseWriter, r *Request) {
w.WriteHeader(StatusCertificateRequired, "Certificate required")
}
// CertificateNotAuthorized responds to the request with
// the CertificateNotAuthorized status code.
func CertificateNotAuthorized(w *ResponseWriter, r *Request) {
w.WriteHeader(StatusCertificateNotAuthorized, "Certificate not authorized")
}
// Certificate returns the request certificate. If one is not provided,
// it returns nil and responds with StatusCertificateRequired.
func Certificate(w *ResponseWriter, r *Request) (*x509.Certificate, bool) {
if len(r.TLS.PeerCertificates) == 0 {
CertificateRequired(w, r)
return nil, false
}
return r.TLS.PeerCertificates[0], true
}
// ResponderFunc is a wrapper around a bare function that implements Handler.
type ResponderFunc func(*ResponseWriter, *Request)
func (f ResponderFunc) Respond(w *ResponseWriter, r *Request) {
f(w, r)
}
// The following code is modified from the net/http package.
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// ServeMux is a Gemini request multiplexer.
// It matches the URL of each incoming request against a list of registered
// patterns and calls the handler for the pattern that
// most closely matches the URL.
//
// Patterns name fixed, rooted paths, like "/favicon.ico",
// or rooted subtrees, like "/images/" (note the trailing slash).
// Longer patterns take precedence over shorter ones, so that
// if there are handlers registered for both "/images/"
// and "/images/thumbnails/", the latter handler will be
// called for paths beginning "/images/thumbnails/" and the
// former will receive requests for any other paths in the
// "/images/" subtree.
//
// Note that since a pattern ending in a slash names a rooted subtree,
// the pattern "/" matches all paths not matched by other registered
// patterns, not just the URL with Path == "/".
//
// If a subtree has been registered and a request is received naming the
// subtree root without its trailing slash, ServeMux redirects that
// request to the subtree root (adding the trailing slash). This behavior can
// be overridden with a separate registration for the path without
// the trailing slash. For example, registering "/images/" causes ServeMux
// to redirect a request for "/images" to "/images/", unless "/images" has
// been registered separately.
//
// ServeMux also takes care of sanitizing the URL request path and
// redirecting any request containing . or .. elements or repeated slashes
// to an equivalent, cleaner URL.
type ServeMux struct {
mu sync.RWMutex
m map[string]muxEntry
es []muxEntry // slice of entries sorted from longest to shortest.
}
type muxEntry struct {
r Responder
pattern string
}
// cleanPath returns the canonical path for p, eliminating . and .. elements.
func cleanPath(p string) string {
if p == "" {
return "/"
}
if p[0] != '/' {
p = "/" + p
}
np := path.Clean(p)
// path.Clean removes trailing slash except for root;
// put the trailing slash back if necessary.
if p[len(p)-1] == '/' && np != "/" {
// Fast path for common case of p being the string we want:
if len(p) == len(np)+1 && strings.HasPrefix(p, np) {
np = p
} else {
np += "/"
}
}
return np
}
// Find a handler on a handler map given a path string.
// Most-specific (longest) pattern wins.
func (mux *ServeMux) match(path string) Responder {
// Check for exact match first.
v, ok := mux.m[path]
if ok {
return v.r
}
// Check for longest valid match. mux.es contains all patterns
// that end in / sorted from longest to shortest.
for _, e := range mux.es {
if strings.HasPrefix(path, e.pattern) {
return e.r
}
}
return nil
}
// redirectToPathSlash determines if the given path needs appending "/" to it.
// This occurs when a handler for path + "/" was already registered, but
// not for path itself. If the path needs appending to, it creates a new
// URL, setting the path to u.Path + "/" and returning true to indicate so.
func (mux *ServeMux) redirectToPathSlash(path string, u *url.URL) (*url.URL, bool) {
mux.mu.RLock()
shouldRedirect := mux.shouldRedirectRLocked(path)
mux.mu.RUnlock()
if !shouldRedirect {
return u, false
}
path = path + "/"
u = &url.URL{Path: path, RawQuery: u.RawQuery}
return u, true
}
// shouldRedirectRLocked reports whether the given path and host should be redirected to
// path+"/". This should happen if a handler is registered for path+"/" but
// not path -- see comments at ServeMux.
func (mux *ServeMux) shouldRedirectRLocked(path string) bool {
if _, exist := mux.m[path]; exist {
return false
}
n := len(path)
if n == 0 {
return false
}
if _, exist := mux.m[path+"/"]; exist {
return path[n-1] != '/'
}
return false
}
// Respond dispatches the request to the responder whose
// pattern most closely matches the request URL.
func (mux *ServeMux) Respond(w *ResponseWriter, r *Request) {
path := cleanPath(r.URL.Path)
// If the given path is /tree and its handler is not registered,
// redirect for /tree/.
if u, ok := mux.redirectToPathSlash(path, r.URL); ok {
Redirect(w, r, u.String())
return
}
if path != r.URL.Path {
u := *r.URL
u.Path = path
Redirect(w, r, u.String())
return
}
mux.mu.RLock()
defer mux.mu.RUnlock()
resp := mux.match(path)
if resp == nil {
NotFound(w, r)
return
}
resp.Respond(w, r)
}
// Handle registers the responder for the given pattern.
// If a responder already exists for pattern, Handle panics.
func (mux *ServeMux) Handle(pattern string, responder Responder) {
mux.mu.Lock()
defer mux.mu.Unlock()
if pattern == "" {
panic("gemini: invalid pattern")
}
if responder == nil {
panic("gemini: nil responder")
}
if _, exist := mux.m[pattern]; exist {
panic("gemini: multiple registrations for " + pattern)
}
if mux.m == nil {
mux.m = make(map[string]muxEntry)
}
e := muxEntry{responder, pattern}
mux.m[pattern] = e
if pattern[len(pattern)-1] == '/' {
mux.es = appendSorted(mux.es, e)
}
}
func appendSorted(es []muxEntry, e muxEntry) []muxEntry {
n := len(es)
i := sort.Search(n, func(i int) bool {
return len(es[i].pattern) < len(e.pattern)
})
if i == n {
return append(es, e)
}
// we now know that i points at where we want to insert
es = append(es, muxEntry{}) // try to grow the slice in place, any entry works.
copy(es[i+1:], es[i:]) // move shorter entries down
es[i] = e
return es
}
// HandleFunc registers the responder function for the given pattern.
func (mux *ServeMux) HandleFunc(pattern string, responder func(*ResponseWriter, *Request)) {
if responder == nil {
panic("gemini: nil responder")
}
mux.Handle(pattern, ResponderFunc(responder))
}