git.distorted.org.uk Git - u/mdw/putty/blob - x11fwd.c

   1 #include <windows.h>
   2 #include <stdio.h>
   3 #include <stdlib.h>
   4
   5 #include "putty.h"
   6 #include "ssh.h"
   7
   8 #ifndef FALSE
   9 #define FALSE 0
  10 #endif
  11 #ifndef TRUE
  12 #define TRUE 1
  13 #endif
  14
  15 #define GET_32BIT_LSB_FIRST(cp) \
  16   (((unsigned long)(unsigned char)(cp)[0]) | \
  17   ((unsigned long)(unsigned char)(cp)[1] << 8) | \
  18   ((unsigned long)(unsigned char)(cp)[2] << 16) | \
  19   ((unsigned long)(unsigned char)(cp)[3] << 24))
  20
  21 #define PUT_32BIT_LSB_FIRST(cp, value) ( \
  22   (cp)[0] = (value), \
  23   (cp)[1] = (value) >> 8, \
  24   (cp)[2] = (value) >> 16, \
  25   (cp)[3] = (value) >> 24 )
  26
  27 #define GET_16BIT_LSB_FIRST(cp) \
  28   (((unsigned long)(unsigned char)(cp)[0]) | \
  29   ((unsigned long)(unsigned char)(cp)[1] << 8))
  30
  31 #define PUT_16BIT_LSB_FIRST(cp, value) ( \
  32   (cp)[0] = (value), \
  33   (cp)[1] = (value) >> 8 )
  34
  35 #define GET_32BIT_MSB_FIRST(cp) \
  36   (((unsigned long)(unsigned char)(cp)[0] << 24) | \
  37   ((unsigned long)(unsigned char)(cp)[1] << 16) | \
  38   ((unsigned long)(unsigned char)(cp)[2] << 8) | \
  39   ((unsigned long)(unsigned char)(cp)[3]))
  40
  41 #define PUT_32BIT_MSB_FIRST(cp, value) ( \
  42   (cp)[0] = (value) >> 24, \
  43   (cp)[1] = (value) >> 16, \
  44   (cp)[2] = (value) >> 8, \
  45   (cp)[3] = (value) )
  46
  47 #define GET_16BIT_MSB_FIRST(cp) \
  48   (((unsigned long)(unsigned char)(cp)[0] << 8) | \
  49   ((unsigned long)(unsigned char)(cp)[1]))
  50
  51 #define PUT_16BIT_MSB_FIRST(cp, value) ( \
  52   (cp)[0] = (value) >> 8, \
  53   (cp)[1] = (value) )
  54
  55 #define GET_16BIT(endian, cp) \
  56   (endian=='B' ? GET_16BIT_MSB_FIRST(cp) : GET_16BIT_LSB_FIRST(cp))
  57
  58 #define PUT_16BIT(endian, cp, val) \
  59   (endian=='B' ? PUT_16BIT_MSB_FIRST(cp, val) : PUT_16BIT_LSB_FIRST(cp, val))
  60
  61 extern void sshfwd_close(void *);
  62 extern void sshfwd_write(void *, char *, int);
  63
  64 struct X11Private {
  65     struct plug_function_table *fn;
  66     /* the above variable absolutely *must* be the first in this structure */
  67     unsigned char firstpkt[12];        /* first X data packet */
  68     char *auth_protocol;
  69     unsigned char *auth_data;
  70     int data_read, auth_plen, auth_psize, auth_dlen, auth_dsize;
  71     int verified;
  72     void *c;                           /* data used by ssh.c */
  73     Socket s;
  74 };
  75
  76 void x11_close (Socket s);
  77
  78 static unsigned char x11_authdata[64];
  79 static int x11_authdatalen;
  80
  81 void x11_invent_auth(char *proto, int protomaxlen,
  82                      char *data, int datamaxlen) {
  83     char ourdata[64];
  84     int i;
  85
  86     /* MIT-MAGIC-COOKIE-1. Cookie size is 128 bits (16 bytes). */
  87     x11_authdatalen = 16;
  88     for (i = 0; i < 16; i++)
  89         x11_authdata[i] = random_byte();
  90
  91     /* Now format for the recipient. */
  92     strncpy(proto, "MIT-MAGIC-COOKIE-1", protomaxlen);
  93     ourdata[0] = '\0';
  94     for (i = 0; i < x11_authdatalen; i++)
  95         sprintf(ourdata+strlen(ourdata), "%02x", x11_authdata[i]);
  96     strncpy(data, ourdata, datamaxlen);
  97 }
  98
  99 static int x11_verify(char *proto, unsigned char *data, int dlen) {
 100     if (strcmp(proto, "MIT-MAGIC-COOKIE-1") != 0)
 101         return 0;                      /* wrong protocol attempted */
 102     if (dlen != x11_authdatalen)
 103         return 0;                      /* cookie was wrong length */
 104     if (memcmp(x11_authdata, data, dlen) != 0)
 105         return 0;                      /* cookie was wrong cookie! */
 106     return 1;
 107 }
 108
 109 static int x11_closing (Plug plug, char *error_msg, int error_code, int calling_back) {
 110     struct X11Private *pr = (struct X11Private *) plug;
 111
 112     /*
 113      * We have no way to communicate down the forwarded connection,
 114      * so if an error occurred on the socket, we just ignore it
 115      * and treat it like a proper close.
 116      */
 117     sshfwd_close(pr->c);
 118     x11_close(pr->s);
 119     return 1;
 120 }
 121
 122 static int x11_receive (Plug plug, int urgent, char *data, int len) {
 123     struct X11Private *pr = (struct X11Private *) plug;
 124
 125     sshfwd_write(pr->c, data, len);
 126     return 1;
 127 }
 128
 129 /*
 130  * Called to set up the raw connection.
 131  *
 132  * Returns an error message, or NULL on success.
 133  * also, fills the SocketsStructure
 134  */
 135 char *x11_init (Socket *s, char *display, void *c) {
 136     static struct plug_function_table fn_table = {
 137         x11_closing,
 138         x11_receive
 139     };
 140
 141     SockAddr addr;
 142     int port;
 143     char *err, *dummy_realhost;
 144     char host[128];
 145     int n, displaynum;
 146     struct X11Private *pr;
 147
 148     /*
 149      * Split up display name into host and display-number parts.
 150      */
 151     n = strcspn(display, ":");
 152     if (display[n])
 153         displaynum = atoi(display+n+1);
 154     else
 155         displaynum = 0;                /* sensible default */
 156     if (n > sizeof(host)-1)
 157         n = sizeof(host)-1;
 158     strncpy(host, display, n);
 159     host[n] = '\0';
 160
 161     /*
 162      * Try to find host.
 163      */
 164     addr = sk_namelookup(host, &dummy_realhost);
 165     if ( (err = sk_addr_error(addr)) )
 166         return err;
 167
 168     port = 6000 + displaynum;
 169
 170     /*
 171      * Open socket.
 172      */
 173     pr = (struct X11Private *)smalloc(sizeof(struct X11Private));
 174     pr->fn = &fn_table;
 175     pr->auth_protocol = NULL;
 176     pr->verified = 0;
 177     pr->data_read = 0;
 178     pr->c = c;
 179
 180     pr->s = *s = sk_new(addr, port, 0, 1, (Plug) pr);
 181     if ( (err = sk_socket_error(*s)) ) {
 182         sfree (pr);
 183         return err;
 184     }
 185
 186     sk_set_private_ptr(*s, pr);
 187     sk_addr_free(addr);
 188     return NULL;
 189 }
 190
 191 void x11_close (Socket s) {
 192     struct X11Private *pr;
 193         if (!s)
 194                 return;
 195         pr = (struct X11Private *)sk_get_private_ptr(s);
 196
 197     if (pr->auth_protocol) {
 198         sfree(pr->auth_protocol);
 199         sfree(pr->auth_data);
 200     }
 201
 202     sfree(pr);
 203
 204     sk_close(s);
 205 }
 206
 207 /*
 208  * Called to send data down the raw connection.
 209  */
 210 void x11_send (Socket s, char *data, int len) {
 211     struct X11Private *pr = (struct X11Private *)sk_get_private_ptr(s);
 212
 213     if (s == NULL)
 214         return;
 215
 216     /*
 217      * Read the first packet.
 218      */
 219     while (len > 0 && pr->data_read < 12)
 220         pr->firstpkt[pr->data_read++] = (unsigned char)(len--, *data++);
 221     if (pr->data_read < 12)
 222         return;
 223
 224     /*
 225      * If we have not allocated the auth_protocol and auth_data
 226      * strings, do so now.
 227      */
 228     if (!pr->auth_protocol) {
 229         pr->auth_plen = GET_16BIT(pr->firstpkt[0], pr->firstpkt+6);
 230         pr->auth_dlen = GET_16BIT(pr->firstpkt[0], pr->firstpkt+8);
 231         pr->auth_psize = (pr->auth_plen + 3) &~ 3;
 232         pr->auth_dsize = (pr->auth_dlen + 3) &~ 3;
 233         /* Leave room for a terminating zero, to make our lives easier. */
 234         pr->auth_protocol = (char *)smalloc(pr->auth_psize+1);
 235         pr->auth_data = (char *)smalloc(pr->auth_dsize);
 236     }
 237
 238     /*
 239      * Read the auth_protocol and auth_data strings.
 240      */
 241     while (len > 0 && pr->data_read < 12 + pr->auth_psize)
 242         pr->auth_protocol[pr->data_read++ - 12] = (len--, *data++);
 243     while (len > 0 && pr->data_read < 12 + pr->auth_psize + pr->auth_dsize)
 244         pr->auth_data[pr->data_read++ - 12 -
 245                       pr->auth_psize] = (unsigned char)(len--, *data++);
 246     if (pr->data_read < 12 + pr->auth_psize + pr->auth_dsize)
 247         return;
 248
 249     /*
 250      * If we haven't verified the authentication, do so now.
 251      */
 252     if (!pr->verified) {
 253         int ret;
 254
 255         pr->auth_protocol[pr->auth_plen] = '\0';   /* ASCIZ */
 256         ret = x11_verify(pr->auth_protocol, pr->auth_data, pr->auth_dlen);
 257
 258         /*
 259          * If authentication failed, construct and send an error
 260          * packet, then terminate the connection.
 261          */
 262         if (!ret) {
 263             char message[] = "Authentication failed at PuTTY X11 proxy";
 264             unsigned char reply[8 + sizeof(message) + 4];
 265             int msglen = sizeof(message)-1;   /* skip zero byte */
 266             int msgsize = (msglen+3) &~ 3;
 267             reply[0] = 0;              /* failure */
 268             reply[1] = msglen;         /* length of reason string */
 269             memcpy(reply+2, pr->firstpkt+2, 4);   /* major/minor proto vsn */
 270             PUT_16BIT(pr->firstpkt[0], reply+6, msglen >> 2);   /* data len */
 271             memset(reply+8, 0, msgsize);
 272             memcpy(reply+8, message, msglen);
 273             sshfwd_write(pr->c, reply, 8+msgsize);
 274             sshfwd_close(pr->c);
 275             x11_close(s);
 276             return;
 277         }
 278
 279         /*
 280          * Now we know we're going to accept the connection. Strip
 281          * the auth data. (TODO: if we ever work out how, we should
 282          * replace some real auth data in here.)
 283          */
 284         PUT_16BIT(pr->firstpkt[0], pr->firstpkt+6, 0);   /* auth proto */
 285         PUT_16BIT(pr->firstpkt[0], pr->firstpkt+8, 0);   /* auth data */
 286         sk_write(s, pr->firstpkt, 12);
 287         pr->verified = 1;
 288     }
 289
 290     /*
 291      * After initialisation, just copy data simply.
 292      */
 293
 294     sk_write(s, data, len);
 295 }