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server.go
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server.go
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package guac
import (
"fmt"
logger "github.com/sirupsen/logrus"
"io"
"net/http"
"strings"
)
const (
readPrefix string = "read:"
writePrefix string = "write:"
readPrefixLength = len(readPrefix)
writePrefixLength = len(writePrefix)
uuidLength = 36
)
// Server uses HTTP requests to talk to guacd (as opposed to WebSockets in ws_server.go)
type Server struct {
tunnels *TunnelMap
connect func(*http.Request) (Tunnel, error)
}
// NewServer constructor
func NewServer(connect func(r *http.Request) (Tunnel, error)) *Server {
return &Server{
tunnels: NewTunnelMap(),
connect: connect,
}
}
// Registers the given tunnel such that future read/write requests to that tunnel will be properly directed.
func (s *Server) registerTunnel(tunnel Tunnel) {
s.tunnels.Put(tunnel.GetUUID(), tunnel)
logger.Debugf("Registered tunnel %v.", tunnel.GetUUID())
}
// Deregisters the given tunnel such that future read/write requests to that tunnel will be rejected.
func (s *Server) deregisterTunnel(tunnel Tunnel) {
s.tunnels.Remove(tunnel.GetUUID())
logger.Debugf("Deregistered tunnel %v.", tunnel.GetUUID())
}
// Returns the tunnel with the given UUID.
func (s *Server) getTunnel(tunnelUUID string) (ret Tunnel, err error) {
var ok bool
ret, ok = s.tunnels.Get(tunnelUUID)
if !ok {
err = ErrResourceNotFound.NewError("No such tunnel.")
}
return
}
func (s *Server) sendError(response http.ResponseWriter, guacStatus Status, message string) {
response.Header().Set("Guacamole-Status-Code", fmt.Sprintf("%v", guacStatus.GetGuacamoleStatusCode()))
response.Header().Set("Guacamole-Error-Message", message)
response.WriteHeader(guacStatus.GetHTTPStatusCode())
}
func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
err := s.handleTunnelRequestCore(w, r)
if err == nil {
return
}
guacErr := err.(*ErrGuac)
switch guacErr.Kind {
case ErrClient:
logger.Warn("HTTP tunnel request rejected: ", err.Error())
s.sendError(w, guacErr.Status, err.Error())
default:
logger.Error("HTTP tunnel request failed: ", err.Error())
logger.Debug("Internal error in HTTP tunnel.", err)
s.sendError(w, guacErr.Status, "Internal server error.")
}
return
}
func (s *Server) handleTunnelRequestCore(response http.ResponseWriter, request *http.Request) (err error) {
query := request.URL.RawQuery
if len(query) == 0 {
return ErrClient.NewError("No query string provided.")
}
// Call the supplied connect callback upon HTTP connect request
if query == "connect" {
tunnel, e := s.connect(request)
if e != nil {
err = ErrResourceNotFound.NewError("No tunnel created.", e.Error())
return
}
s.registerTunnel(tunnel)
// Ensure buggy browsers do not cache response
response.Header().Set("Cache-Control", "no-cache")
_, e = response.Write([]byte(tunnel.GetUUID()))
if e != nil {
err = ErrServer.NewError(e.Error())
return
}
return
}
// Connect has already been called so we use the UUID to do read and writes to the existing session
if strings.HasPrefix(query, readPrefix) && len(query) >= readPrefixLength+uuidLength {
err = s.doRead(response, request, query[readPrefixLength:readPrefixLength+uuidLength])
} else if strings.HasPrefix(query, writePrefix) && len(query) >= writePrefixLength+uuidLength {
err = s.doWrite(response, request, query[writePrefixLength:writePrefixLength+uuidLength])
} else {
err = ErrClient.NewError("Invalid tunnel operation: " + query)
}
return
}
// doRead takes guacd messages and sends them in the response
func (s *Server) doRead(response http.ResponseWriter, request *http.Request, tunnelUUID string) error {
tunnel, err := s.getTunnel(tunnelUUID)
if err != nil {
return err
}
reader := tunnel.AcquireReader()
defer tunnel.ReleaseReader()
// Note that although we are sending text, Webkit browsers will
// buffer 1024 bytes before starting a normal stream if we use
// anything but application/octet-stream.
response.Header().Set("Content-Type", "application/octet-stream")
response.Header().Set("Cache-Control", "no-cache")
if v, ok := response.(http.Flusher); ok {
v.Flush()
}
err = s.writeSome(response, reader, tunnel)
if err == nil {
// success
return err
}
switch err.(*ErrGuac).Kind {
// Send end-of-stream marker and close tunnel if connection is closed
case ErrConnectionClosed:
s.deregisterTunnel(tunnel)
tunnel.Close()
// End-of-instructions marker
_, _ = response.Write([]byte("0.;"))
if v, ok := response.(http.Flusher); ok {
v.Flush()
}
default:
logger.Debugln("Error writing to output", err)
s.deregisterTunnel(tunnel)
tunnel.Close()
}
return err
}
// writeSome drains the guacd buffer holding instructions into the response
func (s *Server) writeSome(response http.ResponseWriter, guacd InstructionReader, tunnel Tunnel) (err error) {
var message []byte
for {
message, err = guacd.ReadSome()
if err != nil {
s.deregisterTunnel(tunnel)
tunnel.Close()
return
}
if len(message) == 0 {
return
}
_, e := response.Write(message)
if e != nil {
err = ErrOther.NewError(e.Error())
return
}
if !guacd.Available() {
if v, ok := response.(http.Flusher); ok {
v.Flush()
}
}
// No more messages another guacd can take over
if tunnel.HasQueuedReaderThreads() {
break
}
}
// End-of-instructions marker
if _, err = response.Write([]byte("0.;")); err != nil {
return err
}
if v, ok := response.(http.Flusher); ok {
v.Flush()
}
return nil
}
// doWrite takes data from the request and sends it to guacd
func (s *Server) doWrite(response http.ResponseWriter, request *http.Request, tunnelUUID string) error {
tunnel, err := s.getTunnel(tunnelUUID)
if err != nil {
return err
}
// We still need to set the content type to avoid the default of
// text/html, as such a content type would cause some browsers to
// attempt to parse the result, even though the JavaScript client
// does not explicitly request such parsing.
response.Header().Set("Content-Type", "application/octet-stream")
response.Header().Set("Cache-Control", "no-cache")
response.Header().Set("Content-Length", "0")
writer := tunnel.AcquireWriter()
defer tunnel.ReleaseWriter()
_, err = io.Copy(writer, request.Body)
if err != nil {
s.deregisterTunnel(tunnel)
if err = tunnel.Close(); err != nil {
logger.Debug("Error closing tunnel")
}
}
return err
}