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     int proto = -1;
  17
  18     /*
  19      * Normally we should run `xauth list DISPLAYNAME'. However,
  20      * there's an oddity when the display is local: the display
  21      * `localhost:0' (or `:0') should become just `:0'.
  22      */
  23     if (!strncmp(display, "localhost:", 10))
  24         command = dupprintf("xauth list %s 2>/dev/null", display+9);
  25     else
  26         command = dupprintf("xauth list %s 2>/dev/null", display);
  27     fp = popen(command, "r");
  28     sfree(command);
  29
  30     if (!fp)
  31         return;                        /* assume no auth */
  32
  33     localbuf = snewn(maxsize, char);
  34
  35     while (1) {
  36         /*
  37          * Read a line from stdin, and attempt to parse it into a
  38          * display name (ignored), auth protocol, and auth string.
  39          */
  40         int c, i, hexdigit;
  41         char protoname[64];
  42
  43         /* Skip the display name. */
  44         while (c = getc(fp), c != EOF && c != '\n' && !isspace(c));
  45         if (c == EOF) break;
  46         if (c == '\n') continue;
  47
  48         /* Skip white space. */
  49         while (c != EOF && c != '\n' && isspace(c))
  50             c = getc(fp);
  51         if (c == EOF) break;
  52         if (c == '\n') continue;
  53
  54         /* Read the auth protocol name, and see if it matches any we
  55          * know about. */
  56         i = 0;
  57         while (c != EOF && c != '\n' && !isspace(c)) {
  58             if (i < lenof(protoname)-1) protoname[i++] = c;
  59             c = getc(fp);
  60         }
  61         protoname[i] = '\0';
  62
  63         for (i = X11_NO_AUTH; ++i < X11_NAUTHS ;) {
  64             if (!strcmp(protoname, x11_authnames[i]))
  65                 break;
  66         }
  67         if (i >= X11_NAUTHS || i <= proto) {
  68             /* Unrecognised protocol name, or a worse one than we already have.
  69              * Skip this line. */
  70             while (c != EOF && c != '\n')
  71                 c = getc(fp);
  72             if (c == EOF) break;
  73         }
  74         proto = i;
  75
  76         /* Skip white space. */
  77         while (c != EOF && c != '\n' && isspace(c))
  78             c = getc(fp);
  79         if (c == EOF) break;
  80         if (c == '\n') continue;
  81
  82         /*
  83          * Now grab pairs of hex digits and shove them into `data'.
  84          */
  85         i = 0;
  86         hexdigit = -1;
  87         while (c != EOF && c != '\n') {
  88             int hexval = -1;
  89             if (c >= 'A' && c <= 'F')
  90                 hexval = c + 10 - 'A';
  91             if (c >= 'a' && c <= 'f')
  92                 hexval = c + 10 - 'a';
  93             if (c >= '0' && c <= '9')
  94                 hexval = c - '0';
  95             if (hexval >= 0) {
  96                 if (hexdigit >= 0) {
  97                     hexdigit = (hexdigit << 4) + hexval;
  98                     if (i < maxsize)
  99                         localbuf[i++] = hexdigit;
 100                     hexdigit = -1;
 101                 } else
 102                     hexdigit = hexval;
 103             }
 104             c = getc(fp);
 105         }
 106
 107         *datalen = i;
 108         *protocol = proto;
 109         memcpy(data, localbuf, i);
 110
 111         /* Nonetheless, continue looping round; we might find a better one. */
 112     }
 113     pclose(fp);
 114     sfree(localbuf);
 115 }