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

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3
   4 #include "putty.h"
   5 #include "ssh.h"
   6
   7 #define GET_32BIT_LSB_FIRST(cp) \
   8   (((unsigned long)(unsigned char)(cp)[0]) | \
   9   ((unsigned long)(unsigned char)(cp)[1] << 8) | \
  10   ((unsigned long)(unsigned char)(cp)[2] << 16) | \
  11   ((unsigned long)(unsigned char)(cp)[3] << 24))
  12
  13 #define PUT_32BIT_LSB_FIRST(cp, value) ( \
  14   (cp)[0] = (value), \
  15   (cp)[1] = (value) >> 8, \
  16   (cp)[2] = (value) >> 16, \
  17   (cp)[3] = (value) >> 24 )
  18
  19 #define GET_16BIT_LSB_FIRST(cp) \
  20   (((unsigned long)(unsigned char)(cp)[0]) | \
  21   ((unsigned long)(unsigned char)(cp)[1] << 8))
  22
  23 #define PUT_16BIT_LSB_FIRST(cp, value) ( \
  24   (cp)[0] = (value), \
  25   (cp)[1] = (value) >> 8 )
  26
  27 #define GET_32BIT_MSB_FIRST(cp) \
  28   (((unsigned long)(unsigned char)(cp)[0] << 24) | \
  29   ((unsigned long)(unsigned char)(cp)[1] << 16) | \
  30   ((unsigned long)(unsigned char)(cp)[2] << 8) | \
  31   ((unsigned long)(unsigned char)(cp)[3]))
  32
  33 #define PUT_32BIT_MSB_FIRST(cp, value) ( \
  34   (cp)[0] = (value) >> 24, \
  35   (cp)[1] = (value) >> 16, \
  36   (cp)[2] = (value) >> 8, \
  37   (cp)[3] = (value) )
  38
  39 #define GET_16BIT_MSB_FIRST(cp) \
  40   (((unsigned long)(unsigned char)(cp)[0] << 8) | \
  41   ((unsigned long)(unsigned char)(cp)[1]))
  42
  43 #define PUT_16BIT_MSB_FIRST(cp, value) ( \
  44   (cp)[0] = (value) >> 8, \
  45   (cp)[1] = (value) )
  46
  47 #define GET_16BIT(endian, cp) \
  48   (endian=='B' ? GET_16BIT_MSB_FIRST(cp) : GET_16BIT_LSB_FIRST(cp))
  49
  50 #define PUT_16BIT(endian, cp, val) \
  51   (endian=='B' ? PUT_16BIT_MSB_FIRST(cp, val) : PUT_16BIT_LSB_FIRST(cp, val))
  52
  53 struct X11Auth {
  54     unsigned char data[64];
  55     int len;
  56 };
  57
  58 struct X11Private {
  59     const struct plug_function_table *fn;
  60     /* the above variable absolutely *must* be the first in this structure */
  61     unsigned char firstpkt[12];        /* first X data packet */
  62     struct X11Auth *auth;
  63     char *auth_protocol;
  64     unsigned char *auth_data;
  65     int data_read, auth_plen, auth_psize, auth_dlen, auth_dsize;
  66     int verified;
  67     int throttled, throttle_override;
  68     void *c;                           /* data used by ssh.c */
  69     Socket s;
  70 };
  71
  72 void *x11_invent_auth(char *proto, int protomaxlen,
  73                      char *data, int datamaxlen)
  74 {
  75     struct X11Auth *auth = smalloc(sizeof(struct X11Auth));
  76     char ourdata[64];
  77     int i;
  78
  79     /* MIT-MAGIC-COOKIE-1. Cookie size is 128 bits (16 bytes). */
  80     auth->len = 16;
  81     for (i = 0; i < 16; i++)
  82         auth->data[i] = random_byte();
  83
  84     /* Now format for the recipient. */
  85     strncpy(proto, "MIT-MAGIC-COOKIE-1", protomaxlen);
  86     ourdata[0] = '\0';
  87     for (i = 0; i < auth->len; i++)
  88         sprintf(ourdata + strlen(ourdata), "%02x", auth->data[i]);
  89     strncpy(data, ourdata, datamaxlen);
  90
  91     return auth;
  92 }
  93
  94 static int x11_verify(struct X11Auth *auth,
  95                       char *proto, unsigned char *data, int dlen)
  96 {
  97     if (strcmp(proto, "MIT-MAGIC-COOKIE-1") != 0)
  98         return 0;                      /* wrong protocol attempted */
  99     if (dlen != auth->len)
 100         return 0;                      /* cookie was wrong length */
 101     if (memcmp(auth->data, data, dlen) != 0)
 102         return 0;                      /* cookie was wrong cookie! */
 103     return 1;
 104 }
 105
 106 static int x11_closing(Plug plug, char *error_msg, int error_code,
 107                        int calling_back)
 108 {
 109     struct X11Private *pr = (struct X11Private *) plug;
 110
 111     /*
 112      * We have no way to communicate down the forwarded connection,
 113      * so if an error occurred on the socket, we just ignore it
 114      * and treat it like a proper close.
 115      */
 116     sshfwd_close(pr->c);
 117     x11_close(pr->s);
 118     return 1;
 119 }
 120
 121 static int x11_receive(Plug plug, int urgent, char *data, int len)
 122 {
 123     struct X11Private *pr = (struct X11Private *) plug;
 124
 125     if (sshfwd_write(pr->c, data, len) > 0) {
 126         pr->throttled = 1;
 127         sk_set_frozen(pr->s, 1);
 128     }
 129
 130     return 1;
 131 }
 132
 133 static void x11_sent(Plug plug, int bufsize)
 134 {
 135     struct X11Private *pr = (struct X11Private *) plug;
 136
 137     sshfwd_unthrottle(pr->c, bufsize);
 138 }
 139
 140 /*
 141  * When setting up X forwarding, we should send the screen number
 142  * from the specified local display. This function extracts it from
 143  * the display string.
 144  */
 145 int x11_get_screen_number(char *display)
 146 {
 147     int n;
 148
 149     n = strcspn(display, ":");
 150     if (!display[n])
 151         return 0;
 152     n = strcspn(display, ".");
 153     if (!display[n])
 154         return 0;
 155     return atoi(display + n + 1);
 156 }
 157
 158 /*
 159  * Called to set up the raw connection.
 160  *
 161  * Returns an error message, or NULL on success.
 162  * also, fills the SocketsStructure
 163  */
 164 char *x11_init(Socket * s, char *display, void *c, void *auth)
 165 {
 166     static const struct plug_function_table fn_table = {
 167         x11_closing,
 168         x11_receive,
 169         x11_sent,
 170         NULL
 171     };
 172
 173     SockAddr addr;
 174     int port;
 175     char *err, *dummy_realhost;
 176     char host[128];
 177     int n, displaynum;
 178     struct X11Private *pr;
 179
 180     /*
 181      * Split up display name into host and display-number parts.
 182      */
 183     n = strcspn(display, ":");
 184     if (display[n])
 185         displaynum = atoi(display + n + 1);
 186     else
 187         displaynum = 0;                /* sensible default */
 188     if (n > sizeof(host) - 1)
 189         n = sizeof(host) - 1;
 190     if (n > 0) {
 191         strncpy(host, display, n);
 192         host[n] = '\0';
 193     } else {
 194         /*
 195          * Local display numbers, particularly on Unix, often omit
 196          * the display part completely.
 197          */
 198         strcpy(host, "localhost");
 199     }
 200
 201     port = 6000 + displaynum;
 202
 203     /*
 204      * Try to find host.
 205      */
 206     addr = name_lookup(host, port, &dummy_realhost);
 207     if ((err = sk_addr_error(addr)) != NULL)
 208         return err;
 209
 210     /*
 211      * Open socket.
 212      */
 213     pr = (struct X11Private *) smalloc(sizeof(struct X11Private));
 214     pr->fn = &fn_table;
 215     pr->auth_protocol = NULL;
 216     pr->auth = (struct X11Auth *)auth;
 217     pr->verified = 0;
 218     pr->data_read = 0;
 219     pr->throttled = pr->throttle_override = 0;
 220     pr->c = c;
 221
 222     pr->s = *s = new_connection(addr, dummy_realhost, port, 0, 1, 0, (Plug) pr);
 223     if ((err = sk_socket_error(*s)) != NULL) {
 224         sfree(pr);
 225         return err;
 226     }
 227
 228     sk_set_private_ptr(*s, pr);
 229     sk_addr_free(addr);
 230     return NULL;
 231 }
 232
 233 void x11_close(Socket s)
 234 {
 235     struct X11Private *pr;
 236     if (!s)
 237         return;
 238     pr = (struct X11Private *) sk_get_private_ptr(s);
 239     if (pr->auth_protocol) {
 240         sfree(pr->auth_protocol);
 241         sfree(pr->auth_data);
 242     }
 243
 244     sfree(pr);
 245
 246     sk_close(s);
 247 }
 248
 249 void x11_unthrottle(Socket s)
 250 {
 251     struct X11Private *pr;
 252     if (!s)
 253         return;
 254     pr = (struct X11Private *) sk_get_private_ptr(s);
 255
 256     pr->throttled = 0;
 257     sk_set_frozen(s, pr->throttled || pr->throttle_override);
 258 }
 259
 260 void x11_override_throttle(Socket s, int enable)
 261 {
 262     struct X11Private *pr;
 263     if (!s)
 264         return;
 265     pr = (struct X11Private *) sk_get_private_ptr(s);
 266
 267     pr->throttle_override = enable;
 268     sk_set_frozen(s, pr->throttled || pr->throttle_override);
 269 }
 270
 271 /*
 272  * Called to send data down the raw connection.
 273  */
 274 int x11_send(Socket s, char *data, int len)
 275 {
 276     struct X11Private *pr = (struct X11Private *) sk_get_private_ptr(s);
 277
 278     if (s == NULL)
 279         return 0;
 280
 281     /*
 282      * Read the first packet.
 283      */
 284     while (len > 0 && pr->data_read < 12)
 285         pr->firstpkt[pr->data_read++] = (unsigned char) (len--, *data++);
 286     if (pr->data_read < 12)
 287         return 0;
 288
 289     /*
 290      * If we have not allocated the auth_protocol and auth_data
 291      * strings, do so now.
 292      */
 293     if (!pr->auth_protocol) {
 294         pr->auth_plen = GET_16BIT(pr->firstpkt[0], pr->firstpkt + 6);
 295         pr->auth_dlen = GET_16BIT(pr->firstpkt[0], pr->firstpkt + 8);
 296         pr->auth_psize = (pr->auth_plen + 3) & ~3;
 297         pr->auth_dsize = (pr->auth_dlen + 3) & ~3;
 298         /* Leave room for a terminating zero, to make our lives easier. */
 299         pr->auth_protocol = (char *) smalloc(pr->auth_psize + 1);
 300         pr->auth_data = (unsigned char *) smalloc(pr->auth_dsize);
 301     }
 302
 303     /*
 304      * Read the auth_protocol and auth_data strings.
 305      */
 306     while (len > 0 && pr->data_read < 12 + pr->auth_psize)
 307         pr->auth_protocol[pr->data_read++ - 12] = (len--, *data++);
 308     while (len > 0 && pr->data_read < 12 + pr->auth_psize + pr->auth_dsize)
 309         pr->auth_data[pr->data_read++ - 12 -
 310                       pr->auth_psize] = (unsigned char) (len--, *data++);
 311     if (pr->data_read < 12 + pr->auth_psize + pr->auth_dsize)
 312         return 0;
 313
 314     /*
 315      * If we haven't verified the authentication, do so now.
 316      */
 317     if (!pr->verified) {
 318         int ret;
 319
 320         pr->auth_protocol[pr->auth_plen] = '\0';        /* ASCIZ */
 321         ret = x11_verify(pr->auth, pr->auth_protocol,
 322                          pr->auth_data, pr->auth_dlen);
 323
 324         /*
 325          * If authentication failed, construct and send an error
 326          * packet, then terminate the connection.
 327          */
 328         if (!ret) {
 329             char message[] = "Authentication failed at PuTTY X11 proxy";
 330             unsigned char reply[8 + sizeof(message) + 4];
 331             int msglen = sizeof(message) - 1;   /* skip zero byte */
 332             int msgsize = (msglen + 3) & ~3;
 333             reply[0] = 0;              /* failure */
 334             reply[1] = msglen;         /* length of reason string */
 335             memcpy(reply + 2, pr->firstpkt + 2, 4);     /* major/minor proto vsn */
 336             PUT_16BIT(pr->firstpkt[0], reply + 6, msgsize >> 2);/* data len */
 337             memset(reply + 8, 0, msgsize);
 338             memcpy(reply + 8, message, msglen);
 339             sshfwd_write(pr->c, (char *)reply, 8 + msgsize);
 340             sshfwd_close(pr->c);
 341             x11_close(s);
 342             return 0;
 343         }
 344
 345         /*
 346          * Now we know we're going to accept the connection. Strip
 347          * the auth data. (TODO: if we ever work out how, we should
 348          * replace some real auth data in here.)
 349          */
 350         PUT_16BIT(pr->firstpkt[0], pr->firstpkt + 6, 0);        /* auth proto */
 351         PUT_16BIT(pr->firstpkt[0], pr->firstpkt + 8, 0);        /* auth data */
 352         sk_write(s, (char *)pr->firstpkt, 12);
 353         pr->verified = 1;
 354     }
 355
 356     /*
 357      * After initialisation, just copy data simply.
 358      */
 359
 360     return sk_write(s, data, len);
 361 }