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_close(Socket s);
  73
  74 void *x11_invent_auth(char *proto, int protomaxlen,
  75                      char *data, int datamaxlen)
  76 {
  77     struct X11Auth *auth = smalloc(sizeof(struct X11Auth));
  78     char ourdata[64];
  79     int i;
  80
  81     /* MIT-MAGIC-COOKIE-1. Cookie size is 128 bits (16 bytes). */
  82     auth->len = 16;
  83     for (i = 0; i < 16; i++)
  84         auth->data[i] = random_byte();
  85
  86     /* Now format for the recipient. */
  87     strncpy(proto, "MIT-MAGIC-COOKIE-1", protomaxlen);
  88     ourdata[0] = '\0';
  89     for (i = 0; i < auth->len; i++)
  90         sprintf(ourdata + strlen(ourdata), "%02x", auth->data[i]);
  91     strncpy(data, ourdata, datamaxlen);
  92
  93     return auth;
  94 }
  95
  96 static int x11_verify(struct X11Auth *auth,
  97                       char *proto, unsigned char *data, int dlen)
  98 {
  99     if (strcmp(proto, "MIT-MAGIC-COOKIE-1") != 0)
 100         return 0;                      /* wrong protocol attempted */
 101     if (dlen != auth->len)
 102         return 0;                      /* cookie was wrong length */
 103     if (memcmp(auth->data, data, dlen) != 0)
 104         return 0;                      /* cookie was wrong cookie! */
 105     return 1;
 106 }
 107
 108 static int x11_closing(Plug plug, char *error_msg, int error_code,
 109                        int calling_back)
 110 {
 111     struct X11Private *pr = (struct X11Private *) plug;
 112
 113     /*
 114      * We have no way to communicate down the forwarded connection,
 115      * so if an error occurred on the socket, we just ignore it
 116      * and treat it like a proper close.
 117      */
 118     sshfwd_close(pr->c);
 119     x11_close(pr->s);
 120     return 1;
 121 }
 122
 123 static int x11_receive(Plug plug, int urgent, char *data, int len)
 124 {
 125     struct X11Private *pr = (struct X11Private *) plug;
 126
 127     if (sshfwd_write(pr->c, data, len) > 0) {
 128         pr->throttled = 1;
 129         sk_set_frozen(pr->s, 1);
 130     }
 131
 132     return 1;
 133 }
 134
 135 static void x11_sent(Plug plug, int bufsize)
 136 {
 137     struct X11Private *pr = (struct X11Private *) plug;
 138
 139     sshfwd_unthrottle(pr->c, bufsize);
 140 }
 141
 142 /*
 143  * When setting up X forwarding, we should send the screen number
 144  * from the specified local display. This function extracts it from
 145  * the display string.
 146  */
 147 int x11_get_screen_number(char *display)
 148 {
 149     int n;
 150
 151     n = strcspn(display, ":");
 152     if (!display[n])
 153         return 0;
 154     n = strcspn(display, ".");
 155     if (!display[n])
 156         return 0;
 157     return atoi(display + n + 1);
 158 }
 159
 160 /*
 161  * Called to set up the raw connection.
 162  *
 163  * Returns an error message, or NULL on success.
 164  * also, fills the SocketsStructure
 165  */
 166 char *x11_init(Socket * s, char *display, void *c, void *auth)
 167 {
 168     static const struct plug_function_table fn_table = {
 169         x11_closing,
 170         x11_receive,
 171         x11_sent,
 172         NULL
 173     };
 174
 175     SockAddr addr;
 176     int port;
 177     char *err, *dummy_realhost;
 178     char host[128];
 179     int n, displaynum;
 180     struct X11Private *pr;
 181
 182     /*
 183      * Split up display name into host and display-number parts.
 184      */
 185     n = strcspn(display, ":");
 186     if (display[n])
 187         displaynum = atoi(display + n + 1);
 188     else
 189         displaynum = 0;                /* sensible default */
 190     if (n > sizeof(host) - 1)
 191         n = sizeof(host) - 1;
 192     if (n > 0) {
 193         strncpy(host, display, n);
 194         host[n] = '\0';
 195     } else {
 196         /*
 197          * Local display numbers, particularly on Unix, often omit
 198          * the display part completely.
 199          */
 200         strcpy(host, "localhost");
 201     }
 202
 203     port = 6000 + displaynum;
 204
 205     /*
 206      * Try to find host.
 207      */
 208     addr = name_lookup(host, port, &dummy_realhost);
 209     if ((err = sk_addr_error(addr)) != NULL)
 210         return err;
 211
 212     /*
 213      * Open socket.
 214      */
 215     pr = (struct X11Private *) smalloc(sizeof(struct X11Private));
 216     pr->fn = &fn_table;
 217     pr->auth_protocol = NULL;
 218     pr->auth = (struct X11Auth *)auth;
 219     pr->verified = 0;
 220     pr->data_read = 0;
 221     pr->throttled = pr->throttle_override = 0;
 222     pr->c = c;
 223
 224     pr->s = *s = new_connection(addr, dummy_realhost, port, 0, 1, 0, (Plug) pr);
 225     if ((err = sk_socket_error(*s)) != NULL) {
 226         sfree(pr);
 227         return err;
 228     }
 229
 230     sk_set_private_ptr(*s, pr);
 231     sk_addr_free(addr);
 232     return NULL;
 233 }
 234
 235 void x11_close(Socket s)
 236 {
 237     struct X11Private *pr;
 238     if (!s)
 239         return;
 240     pr = (struct X11Private *) sk_get_private_ptr(s);
 241     if (pr->auth_protocol) {
 242         sfree(pr->auth_protocol);
 243         sfree(pr->auth_data);
 244     }
 245
 246     sfree(pr);
 247
 248     sk_close(s);
 249 }
 250
 251 void x11_unthrottle(Socket s)
 252 {
 253     struct X11Private *pr;
 254     if (!s)
 255         return;
 256     pr = (struct X11Private *) sk_get_private_ptr(s);
 257
 258     pr->throttled = 0;
 259     sk_set_frozen(s, pr->throttled || pr->throttle_override);
 260 }
 261
 262 void x11_override_throttle(Socket s, int enable)
 263 {
 264     struct X11Private *pr;
 265     if (!s)
 266         return;
 267     pr = (struct X11Private *) sk_get_private_ptr(s);
 268
 269     pr->throttle_override = enable;
 270     sk_set_frozen(s, pr->throttled || pr->throttle_override);
 271 }
 272
 273 /*
 274  * Called to send data down the raw connection.
 275  */
 276 int x11_send(Socket s, char *data, int len)
 277 {
 278     struct X11Private *pr = (struct X11Private *) sk_get_private_ptr(s);
 279
 280     if (s == NULL)
 281         return 0;
 282
 283     /*
 284      * Read the first packet.
 285      */
 286     while (len > 0 && pr->data_read < 12)
 287         pr->firstpkt[pr->data_read++] = (unsigned char) (len--, *data++);
 288     if (pr->data_read < 12)
 289         return 0;
 290
 291     /*
 292      * If we have not allocated the auth_protocol and auth_data
 293      * strings, do so now.
 294      */
 295     if (!pr->auth_protocol) {
 296         pr->auth_plen = GET_16BIT(pr->firstpkt[0], pr->firstpkt + 6);
 297         pr->auth_dlen = GET_16BIT(pr->firstpkt[0], pr->firstpkt + 8);
 298         pr->auth_psize = (pr->auth_plen + 3) & ~3;
 299         pr->auth_dsize = (pr->auth_dlen + 3) & ~3;
 300         /* Leave room for a terminating zero, to make our lives easier. */
 301         pr->auth_protocol = (char *) smalloc(pr->auth_psize + 1);
 302         pr->auth_data = (unsigned char *) smalloc(pr->auth_dsize);
 303     }
 304
 305     /*
 306      * Read the auth_protocol and auth_data strings.
 307      */
 308     while (len > 0 && pr->data_read < 12 + pr->auth_psize)
 309         pr->auth_protocol[pr->data_read++ - 12] = (len--, *data++);
 310     while (len > 0 && pr->data_read < 12 + pr->auth_psize + pr->auth_dsize)
 311         pr->auth_data[pr->data_read++ - 12 -
 312                       pr->auth_psize] = (unsigned char) (len--, *data++);
 313     if (pr->data_read < 12 + pr->auth_psize + pr->auth_dsize)
 314         return 0;
 315
 316     /*
 317      * If we haven't verified the authentication, do so now.
 318      */
 319     if (!pr->verified) {
 320         int ret;
 321
 322         pr->auth_protocol[pr->auth_plen] = '\0';        /* ASCIZ */
 323         ret = x11_verify(pr->auth, pr->auth_protocol,
 324                          pr->auth_data, pr->auth_dlen);
 325
 326         /*
 327          * If authentication failed, construct and send an error
 328          * packet, then terminate the connection.
 329          */
 330         if (!ret) {
 331             char message[] = "Authentication failed at PuTTY X11 proxy";
 332             unsigned char reply[8 + sizeof(message) + 4];
 333             int msglen = sizeof(message) - 1;   /* skip zero byte */
 334             int msgsize = (msglen + 3) & ~3;
 335             reply[0] = 0;              /* failure */
 336             reply[1] = msglen;         /* length of reason string */
 337             memcpy(reply + 2, pr->firstpkt + 2, 4);     /* major/minor proto vsn */
 338             PUT_16BIT(pr->firstpkt[0], reply + 6, msgsize >> 2);/* data len */
 339             memset(reply + 8, 0, msgsize);
 340             memcpy(reply + 8, message, msglen);
 341             sshfwd_write(pr->c, (char *)reply, 8 + msgsize);
 342             sshfwd_close(pr->c);
 343             x11_close(s);
 344             return 0;
 345         }
 346
 347         /*
 348          * Now we know we're going to accept the connection. Strip
 349          * the auth data. (TODO: if we ever work out how, we should
 350          * replace some real auth data in here.)
 351          */
 352         PUT_16BIT(pr->firstpkt[0], pr->firstpkt + 6, 0);        /* auth proto */
 353         PUT_16BIT(pr->firstpkt[0], pr->firstpkt + 8, 0);        /* auth data */
 354         sk_write(s, (char *)pr->firstpkt, 12);
 355         pr->verified = 1;
 356     }
 357
 358     /*
 359      * After initialisation, just copy data simply.
 360      */
 361
 362     return sk_write(s, data, len);
 363 }