libgo/go/exp/draw/x11/auth.go

   1 // Copyright 2009 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 package x11
   6
   7 import (
   8         "bufio"
   9         "io"
  10         "os"
  11 )
  12
  13 // readU16BE reads a big-endian uint16 from r, using b as a scratch buffer.
  14 func readU16BE(r io.Reader, b []byte) (uint16, os.Error) {
  15         _, err := io.ReadFull(r, b[0:2])
  16         if err != nil {
  17                 return 0, err
  18         }
  19         return uint16(b[0])<<8 + uint16(b[1]), nil
  20 }
  21
  22 // readStr reads a length-prefixed string from r, using b as a scratch buffer.
  23 func readStr(r io.Reader, b []byte) (string, os.Error) {
  24         n, err := readU16BE(r, b)
  25         if err != nil {
  26                 return "", err
  27         }
  28         if int(n) > len(b) {
  29                 return "", os.NewError("Xauthority entry too long for buffer")
  30         }
  31         _, err = io.ReadFull(r, b[0:n])
  32         if err != nil {
  33                 return "", err
  34         }
  35         return string(b[0:n]), nil
  36 }
  37
  38 // readAuth reads the X authority file and returns the name/data pair for the display.
  39 // displayStr is the "12" out of a $DISPLAY like ":12.0".
  40 func readAuth(displayStr string) (name, data string, err os.Error) {
  41         // b is a scratch buffer to use and should be at least 256 bytes long
  42         // (i.e. it should be able to hold a hostname).
  43         var b [256]byte
  44         // As per /usr/include/X11/Xauth.h.
  45         const familyLocal = 256
  46
  47         fn := os.Getenv("XAUTHORITY")
  48         if fn == "" {
  49                 home := os.Getenv("HOME")
  50                 if home == "" {
  51                         err = os.NewError("Xauthority not found: $XAUTHORITY, $HOME not set")
  52                         return
  53                 }
  54                 fn = home + "/.Xauthority"
  55         }
  56         r, err := os.Open(fn, os.O_RDONLY, 0444)
  57         if err != nil {
  58                 return
  59         }
  60         defer r.Close()
  61         br := bufio.NewReader(r)
  62
  63         hostname, err := os.Hostname()
  64         if err != nil {
  65                 return
  66         }
  67         for {
  68                 family, err := readU16BE(br, b[0:2])
  69                 if err != nil {
  70                         return
  71                 }
  72                 addr, err := readStr(br, b[0:])
  73                 if err != nil {
  74                         return
  75                 }
  76                 disp, err := readStr(br, b[0:])
  77                 if err != nil {
  78                         return
  79                 }
  80                 name0, err := readStr(br, b[0:])
  81                 if err != nil {
  82                         return
  83                 }
  84                 data0, err := readStr(br, b[0:])
  85                 if err != nil {
  86                         return
  87                 }
  88                 if family == familyLocal && addr == hostname && disp == displayStr {
  89                         return name0, data0, nil
  90                 }
  91         }
  92         panic("unreachable")
  93 }