gotty/app/app.go

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package app
import (
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"crypto/rand"
"encoding/base64"
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"errors"
"io/ioutil"
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"log"
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"math/big"
"net"
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"net/http"
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"net/url"
"os"
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"os/exec"
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"strconv"
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"strings"
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"text/template"
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"github.com/braintree/manners"
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"github.com/elazarl/go-bindata-assetfs"
"github.com/gorilla/websocket"
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"github.com/hashicorp/hcl"
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"github.com/kr/pty"
)
type App struct {
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command []string
options *Options
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upgrader *websocket.Upgrader
server *manners.GracefulServer
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titleTemplate *template.Template
}
type Options struct {
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Address string `hcl:"address"`
Port string `hcl:"port"`
PermitWrite bool `hcl:"permit_write"`
EnableBasicAuth bool `hcl:"enable_basic_auth"`
Credential string `hcl:"credential"`
EnableRandomUrl bool `hcl:"enable_random_url"`
RandomUrlLength int `hcl:"random_url_length"`
IndexFile string `hcl:"index_file"`
EnableTLS bool `hcl:"enable_tls"`
TLSCrtFile string `hcl:"tls_crt_file"`
TLSKeyFile string `hcl:"tls_key_file"`
TitleFormat string `hcl:"title_format"`
EnableReconnect bool `hcl:"enable_reconnect"`
ReconnectTime int `hcl:"reconnect_time"`
Once bool `hcl:"once"`
Preferences map[string]interface{} `hcl:"preferences"`
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}
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var DefaultOptions = Options{
Address: "",
Port: "8080",
PermitWrite: false,
EnableBasicAuth: false,
Credential: "",
EnableRandomUrl: false,
RandomUrlLength: 8,
IndexFile: "",
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EnableTLS: false,
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TLSCrtFile: "~/.gotty.crt",
TLSKeyFile: "~/.gotty.key",
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TitleFormat: "GoTTY - {{ .Command }} ({{ .Hostname }})",
EnableReconnect: false,
ReconnectTime: 10,
Once: false,
Preferences: make(map[string]interface{}),
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}
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func New(command []string, options *Options) (*App, error) {
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titleTemplate, err := template.New("title").Parse(options.TitleFormat)
if err != nil {
return nil, errors.New("Title format string syntax error")
}
return &App{
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command: command,
options: options,
upgrader: &websocket.Upgrader{
ReadBufferSize: 1024,
WriteBufferSize: 1024,
Subprotocols: []string{"gotty"},
},
titleTemplate: titleTemplate,
}, nil
}
func ApplyConfigFile(options *Options, filePath string) error {
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filePath = ExpandHomeDir(filePath)
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if _, err := os.Stat(filePath); os.IsNotExist(err) {
return err
}
fileString := []byte{}
log.Printf("Loading config file at: %s", filePath)
fileString, err := ioutil.ReadFile(filePath)
if err != nil {
return err
}
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if err := hcl.Decode(options, string(fileString)); err != nil {
return err
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}
return nil
}
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func (app *App) Run() error {
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if app.options.PermitWrite {
log.Printf("Permitting clients to write input to the PTY.")
}
if app.options.Once {
log.Printf("Once option is provided, accepting only one client")
}
path := ""
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if app.options.EnableRandomUrl {
path += "/" + generateRandomString(app.options.RandomUrlLength)
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}
endpoint := net.JoinHostPort(app.options.Address, app.options.Port)
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wsHandler := http.HandlerFunc(app.handleWS)
customIndexHandler := http.HandlerFunc(app.handleCustomIndex)
authTokenHandler := http.HandlerFunc(app.handleAuthToken)
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staticHandler := http.FileServer(
&assetfs.AssetFS{Asset: Asset, AssetDir: AssetDir, Prefix: "static"},
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)
var siteMux = http.NewServeMux()
if app.options.IndexFile != "" {
log.Printf("Using index file at " + app.options.IndexFile)
siteMux.Handle(path+"/", customIndexHandler)
} else {
siteMux.Handle(path+"/", http.StripPrefix(path+"/", staticHandler))
}
siteMux.Handle(path+"/auth_token.js", authTokenHandler)
siteMux.Handle(path+"/js/", http.StripPrefix(path+"/", staticHandler))
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siteMux.Handle(path+"/favicon.png", http.StripPrefix(path+"/", staticHandler))
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siteHandler := http.Handler(siteMux)
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if app.options.EnableBasicAuth {
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log.Printf("Using Basic Authentication")
siteHandler = wrapBasicAuth(siteHandler, app.options.Credential)
}
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wsMux := http.NewServeMux()
wsMux.Handle("/", siteHandler)
wsMux.Handle(path+"/ws", wsHandler)
siteHandler = (http.Handler(wsMux))
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siteHandler = wrapLogger(siteHandler)
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scheme := "http"
if app.options.EnableTLS {
scheme = "https"
}
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log.Printf(
"Server is starting with command: %s",
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strings.Join(app.command, " "),
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)
if app.options.Address != "" {
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log.Printf(
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"URL: %s",
(&url.URL{Scheme: scheme, Host: endpoint, Path: path + "/"}).String(),
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)
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} else {
for _, address := range listAddresses() {
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log.Printf(
"URL: %s",
(&url.URL{
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Scheme: scheme,
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Host: net.JoinHostPort(address, app.options.Port),
Path: path + "/",
}).String(),
)
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}
}
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var err error
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app.server = manners.NewWithServer(
&http.Server{Addr: endpoint, Handler: siteHandler},
)
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if app.options.EnableTLS {
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crtFile := ExpandHomeDir(app.options.TLSCrtFile)
keyFile := ExpandHomeDir(app.options.TLSKeyFile)
log.Printf("TLS crt file: " + crtFile)
log.Printf("TLS key file: " + keyFile)
err = app.server.ListenAndServeTLS(crtFile, keyFile)
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} else {
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err = app.server.ListenAndServe()
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}
if err != nil {
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return err
}
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log.Printf("Exiting...")
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return nil
}
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func (app *App) handleWS(w http.ResponseWriter, r *http.Request) {
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log.Printf("New client connected: %s", r.RemoteAddr)
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if r.Method != "GET" {
http.Error(w, "Method not allowed", 405)
return
}
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conn, err := app.upgrader.Upgrade(w, r, nil)
if err != nil {
log.Print("Failed to upgrade connection: " + err.Error())
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return
}
_, initMessage, err := conn.ReadMessage()
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if err != nil || string(initMessage) != app.options.Credential {
log.Print("Failed to authenticate websocket connection")
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conn.Close()
return
}
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cmd := exec.Command(app.command[0], app.command[1:]...)
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ptyIo, err := pty.Start(cmd)
if err != nil {
log.Print("Failed to execute command")
return
}
log.Printf("Command is running for client %s with PID %d", r.RemoteAddr, cmd.Process.Pid)
context := &clientContext{
app: app,
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request: r,
connection: conn,
command: cmd,
pty: ptyIo,
}
context.goHandleClient()
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}
func (app *App) handleCustomIndex(w http.ResponseWriter, r *http.Request) {
http.ServeFile(w, r, ExpandHomeDir(app.options.IndexFile))
}
func (app *App) handleAuthToken(w http.ResponseWriter, r *http.Request) {
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w.Write([]byte("var gotty_auth_token = '" + app.options.Credential + "';"))
}
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func (app *App) Exit() (firstCall bool) {
if app.server != nil {
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firstCall = app.server.Close()
if firstCall {
log.Printf("Received Exit command, waiting for all clients to close sessions...")
}
return firstCall
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}
return true
}
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func wrapLogger(handler http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
rw := &responseWrapper{w, 200}
handler.ServeHTTP(rw, r)
log.Printf("%s %d %s %s", r.RemoteAddr, rw.status, r.Method, r.URL.Path)
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})
}
func wrapBasicAuth(handler http.Handler, credential string) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
token := strings.SplitN(r.Header.Get("Authorization"), " ", 2)
if len(token) != 2 || strings.ToLower(token[0]) != "basic" {
w.Header().Set("WWW-Authenticate", `Basic realm="GoTTY"`)
http.Error(w, "Bad Request", http.StatusUnauthorized)
return
}
payload, err := base64.StdEncoding.DecodeString(token[1])
if err != nil {
http.Error(w, "Internal Server Error", http.StatusInternalServerError)
return
}
if credential != string(payload) {
w.Header().Set("WWW-Authenticate", `Basic realm="GoTTY"`)
http.Error(w, "authorization failed", http.StatusUnauthorized)
return
}
log.Printf("Basic Authentication Succeeded: %s", r.RemoteAddr)
handler.ServeHTTP(w, r)
})
}
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func generateRandomString(length int) string {
const base = 36
size := big.NewInt(base)
n := make([]byte, length)
for i, _ := range n {
c, _ := rand.Int(rand.Reader, size)
n[i] = strconv.FormatInt(c.Int64(), base)[0]
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}
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return string(n)
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}
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func listAddresses() (addresses []string) {
ifaces, _ := net.Interfaces()
addresses = make([]string, 0, len(ifaces))
for _, iface := range ifaces {
ifAddrs, _ := iface.Addrs()
for _, ifAddr := range ifAddrs {
switch v := ifAddr.(type) {
case *net.IPNet:
addresses = append(addresses, v.IP.String())
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case *net.IPAddr:
addresses = append(addresses, v.IP.String())
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}
}
}
return
}
func ExpandHomeDir(path string) string {
if path[0:2] == "~/" {
return os.Getenv("HOME") + path[1:]
} else {
return path
}
}