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 <assert.h>
   8 #include "putty.h"
   9 #include "ssh.h"
  10
  11 void platform_get_x11_auth(char *display, int *protocol,
  12                            unsigned char *data, int *datalen)
  13 {
  14     FILE *fp;
  15     char *command;
  16     int maxsize = *datalen;
  17     char *localbuf;
  18     int proto = -1;
  19
  20     display = x11_display(display);
  21     /*
  22      * Normally we should run `xauth list DISPLAYNAME'. However,
  23      * there's an oddity when the display is local: the display
  24      * `localhost:0' (or `:0') should become just `:0'.
  25      */
  26     if (!strncmp(display, "localhost:", 10)
  27         || !strncmp(display, "unix:", 5))
  28         command = dupprintf("xauth list %s 2>/dev/null",
  29                             strchr(display, ':'));
  30     else
  31         command = dupprintf("xauth list %s 2>/dev/null", display);
  32     sfree(display);
  33     fp = popen(command, "r");
  34     sfree(command);
  35
  36     if (!fp)
  37         return;                        /* assume no auth */
  38
  39     localbuf = snewn(maxsize, char);
  40
  41     while (1) {
  42         /*
  43          * Read a line from stdin, and attempt to parse it into a
  44          * display name (ignored), auth protocol, and auth string.
  45          */
  46         int c, i, hexdigit;
  47         char protoname[64];
  48
  49         /* Skip the display name. */
  50         while (c = getc(fp), c != EOF && c != '\n' && !isspace(c));
  51         if (c == EOF) break;
  52         if (c == '\n') continue;
  53
  54         /* Skip white space. */
  55         while (c != EOF && c != '\n' && isspace(c))
  56             c = getc(fp);
  57         if (c == EOF) break;
  58         if (c == '\n') continue;
  59
  60         /* Read the auth protocol name, and see if it matches any we
  61          * know about. */
  62         i = 0;
  63         while (c != EOF && c != '\n' && !isspace(c)) {
  64             if (i < lenof(protoname)-1) protoname[i++] = c;
  65             c = getc(fp);
  66         }
  67         protoname[i] = '\0';
  68
  69         for (i = X11_NO_AUTH; ++i < X11_NAUTHS ;) {
  70             if (!strcmp(protoname, x11_authnames[i]))
  71                 break;
  72         }
  73         if (i >= X11_NAUTHS || i <= proto) {
  74             /* Unrecognised protocol name, or a worse one than we already have.
  75              * Skip this line. */
  76             while (c != EOF && c != '\n')
  77                 c = getc(fp);
  78             if (c == EOF) break;
  79         }
  80         proto = i;
  81
  82         /* Skip white space. */
  83         while (c != EOF && c != '\n' && isspace(c))
  84             c = getc(fp);
  85         if (c == EOF) break;
  86         if (c == '\n') continue;
  87
  88         /*
  89          * Now grab pairs of hex digits and shove them into `data'.
  90          */
  91         i = 0;
  92         hexdigit = -1;
  93         while (c != EOF && c != '\n') {
  94             int hexval = -1;
  95             if (c >= 'A' && c <= 'F')
  96                 hexval = c + 10 - 'A';
  97             if (c >= 'a' && c <= 'f')
  98                 hexval = c + 10 - 'a';
  99             if (c >= '0' && c <= '9')
 100                 hexval = c - '0';
 101             if (hexval >= 0) {
 102                 if (hexdigit >= 0) {
 103                     hexdigit = (hexdigit << 4) + hexval;
 104                     if (i < maxsize)
 105                         localbuf[i++] = hexdigit;
 106                     hexdigit = -1;
 107                 } else
 108                     hexdigit = hexval;
 109             }
 110             c = getc(fp);
 111         }
 112
 113         *datalen = i;
 114         *protocol = proto;
 115         memcpy(data, localbuf, i);
 116
 117         /* Nonetheless, continue looping round; we might find a better one. */
 118     }
 119     pclose(fp);
 120     sfree(localbuf);
 121 }
 122
 123 const char platform_x11_best_transport[] = "unix";