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