git.distorted.org.uk Git - u/mdw/putty/blob - unix/ux_x11.c

   1 /*
   2  * ux_x11.c: fetch local auth data for X forwarding.
   3  */
   4
   5 #include <ctype.h>
   6 #include <unistd.h>
   7 #include "putty.h"
   8
   9 void platform_get_x11_auth(char *display, int *protocol,
  10                            unsigned char *data, int *datalen)
  11 {
  12     FILE *fp;
  13     char *command;
  14     int maxsize = *datalen;
  15     char *localbuf;
  16
  17     /*
  18      * Normally we should run `xauth list DISPLAYNAME'. However,
  19      * there's an oddity when the display is local: the display
  20      * `localhost:0' (or `:0') should become just `:0'.
  21      */
  22     if (!strncmp(display, "localhost:", 10))
  23         command = dupprintf("xauth list %s 2>/dev/null", display+9);
  24     else
  25         command = dupprintf("xauth list %s 2>/dev/null", display);
  26     fp = popen(command, "r");
  27     sfree(command);
  28
  29     if (!fp)
  30         return;                        /* assume no auth */
  31
  32     localbuf = snewn(maxsize, char);
  33
  34     while (1) {
  35         /*
  36          * Read a line from stdin, and attempt to parse it into a
  37          * display name (ignored), auth protocol, and auth string.
  38          */
  39         int c, i, hexdigit, proto;
  40         char protoname[64];
  41
  42         /* Skip the display name. */
  43         while (c = getc(fp), c != EOF && c != '\n' && !isspace(c));
  44         if (c == EOF) break;
  45         if (c == '\n') continue;
  46
  47         /* Skip white space. */
  48         while (c != EOF && c != '\n' && isspace(c))
  49             c = getc(fp);
  50         if (c == EOF) break;
  51         if (c == '\n') continue;
  52
  53         /* Read the auth protocol name, and see if it matches any we
  54          * know about. */
  55         i = 0;
  56         while (c != EOF && c != '\n' && !isspace(c)) {
  57             if (i < lenof(protoname)-1) protoname[i++] = c;
  58             c = getc(fp);
  59         }
  60         protoname[i] = '\0';
  61
  62         for (i = X11_NO_AUTH; ++i < X11_NAUTHS ;) {
  63             if (!strcmp(protoname, x11_authnames[i]))
  64                 break;
  65         }
  66         if (i >= X11_NAUTHS || i <= proto) {
  67             /* Unrecognised protocol name, or a worse one than we already have.
  68              * Skip this line. */
  69             while (c != EOF && c != '\n')
  70                 c = getc(fp);
  71             if (c == EOF) break;
  72         }
  73         proto = i;
  74
  75         /* Skip white space. */
  76         while (c != EOF && c != '\n' && isspace(c))
  77             c = getc(fp);
  78         if (c == EOF) break;
  79         if (c == '\n') continue;
  80
  81         /*
  82          * Now grab pairs of hex digits and shove them into `data'.
  83          */
  84         i = 0;
  85         hexdigit = -1;
  86         while (c != EOF && c != '\n') {
  87             int hexval = -1;
  88             if (c >= 'A' && c <= 'F')
  89                 hexval = c + 10 - 'A';
  90             if (c >= 'a' && c <= 'f')
  91                 hexval = c + 10 - 'a';
  92             if (c >= '0' && c <= '9')
  93                 hexval = c - '0';
  94             if (hexval >= 0) {
  95                 if (hexdigit >= 0) {
  96                     hexdigit = (hexdigit << 4) + hexval;
  97                     if (i < maxsize)
  98                         localbuf[i++] = hexdigit;
  99                     hexdigit = -1;
 100                 } else
 101                     hexdigit = hexval;
 102             }
 103             c = getc(fp);
 104         }
 105
 106         *datalen = i;
 107         *protocol = proto;
 108         memcpy(data, localbuf, i);
 109
 110         /* Nonetheless, continue looping round; we might find a better one. */
 111     }
 112     pclose(fp);
 113     sfree(localbuf);
 114 }