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  * Called to set up the raw connection.
 144  *
 145  * Returns an error message, or NULL on success.
 146  * also, fills the SocketsStructure
 147  */
 148 char *x11_init(Socket * s, char *display, void *c, void *auth)
 149 {
 150     static const struct plug_function_table fn_table = {
 151         x11_closing,
 152         x11_receive,
 153         x11_sent,
 154         NULL
 155     };
 156
 157     SockAddr addr;
 158     int port;
 159     char *err, *dummy_realhost;
 160     char host[128];
 161     int n, displaynum;
 162     struct X11Private *pr;
 163
 164     /*
 165      * Split up display name into host and display-number parts.
 166      */
 167     n = strcspn(display, ":");
 168     if (display[n])
 169         displaynum = atoi(display + n + 1);
 170     else
 171         displaynum = 0;                /* sensible default */
 172     if (n > sizeof(host) - 1)
 173         n = sizeof(host) - 1;
 174     strncpy(host, display, n);
 175     host[n] = '\0';
 176
 177     /*
 178      * Try to find host.
 179      */
 180     addr = sk_namelookup(host, &dummy_realhost);
 181     if ((err = sk_addr_error(addr)))
 182         return err;
 183
 184     port = 6000 + displaynum;
 185
 186     /*
 187      * Open socket.
 188      */
 189     pr = (struct X11Private *) smalloc(sizeof(struct X11Private));
 190     pr->fn = &fn_table;
 191     pr->auth_protocol = NULL;
 192     pr->auth = (struct X11Auth *)auth;
 193     pr->verified = 0;
 194     pr->data_read = 0;
 195     pr->throttled = pr->throttle_override = 0;
 196     pr->c = c;
 197
 198     pr->s = *s = new_connection(addr, dummy_realhost, port, 0, 1, 0, (Plug) pr);
 199     if ((err = sk_socket_error(*s))) {
 200         sfree(pr);
 201         return err;
 202     }
 203
 204     sk_set_private_ptr(*s, pr);
 205     sk_addr_free(addr);
 206     return NULL;
 207 }
 208
 209 void x11_close(Socket s)
 210 {
 211     struct X11Private *pr;
 212     if (!s)
 213         return;
 214     pr = (struct X11Private *) sk_get_private_ptr(s);
 215     if (pr->auth_protocol) {
 216         sfree(pr->auth_protocol);
 217         sfree(pr->auth_data);
 218     }
 219
 220     sfree(pr);
 221
 222     sk_close(s);
 223 }
 224
 225 void x11_unthrottle(Socket s)
 226 {
 227     struct X11Private *pr;
 228     if (!s)
 229         return;
 230     pr = (struct X11Private *) sk_get_private_ptr(s);
 231
 232     pr->throttled = 0;
 233     sk_set_frozen(s, pr->throttled || pr->throttle_override);
 234 }
 235
 236 void x11_override_throttle(Socket s, int enable)
 237 {
 238     struct X11Private *pr;
 239     if (!s)
 240         return;
 241     pr = (struct X11Private *) sk_get_private_ptr(s);
 242
 243     pr->throttle_override = enable;
 244     sk_set_frozen(s, pr->throttled || pr->throttle_override);
 245 }
 246
 247 /*
 248  * Called to send data down the raw connection.
 249  */
 250 int x11_send(Socket s, char *data, int len)
 251 {
 252     struct X11Private *pr = (struct X11Private *) sk_get_private_ptr(s);
 253
 254     if (s == NULL)
 255         return 0;
 256
 257     /*
 258      * Read the first packet.
 259      */
 260     while (len > 0 && pr->data_read < 12)
 261         pr->firstpkt[pr->data_read++] = (unsigned char) (len--, *data++);
 262     if (pr->data_read < 12)
 263         return 0;
 264
 265     /*
 266      * If we have not allocated the auth_protocol and auth_data
 267      * strings, do so now.
 268      */
 269     if (!pr->auth_protocol) {
 270         pr->auth_plen = GET_16BIT(pr->firstpkt[0], pr->firstpkt + 6);
 271         pr->auth_dlen = GET_16BIT(pr->firstpkt[0], pr->firstpkt + 8);
 272         pr->auth_psize = (pr->auth_plen + 3) & ~3;
 273         pr->auth_dsize = (pr->auth_dlen + 3) & ~3;
 274         /* Leave room for a terminating zero, to make our lives easier. */
 275         pr->auth_protocol = (char *) smalloc(pr->auth_psize + 1);
 276         pr->auth_data = (char *) smalloc(pr->auth_dsize);
 277     }
 278
 279     /*
 280      * Read the auth_protocol and auth_data strings.
 281      */
 282     while (len > 0 && pr->data_read < 12 + pr->auth_psize)
 283         pr->auth_protocol[pr->data_read++ - 12] = (len--, *data++);
 284     while (len > 0 && pr->data_read < 12 + pr->auth_psize + pr->auth_dsize)
 285         pr->auth_data[pr->data_read++ - 12 -
 286                       pr->auth_psize] = (unsigned char) (len--, *data++);
 287     if (pr->data_read < 12 + pr->auth_psize + pr->auth_dsize)
 288         return 0;
 289
 290     /*
 291      * If we haven't verified the authentication, do so now.
 292      */
 293     if (!pr->verified) {
 294         int ret;
 295
 296         pr->auth_protocol[pr->auth_plen] = '\0';        /* ASCIZ */
 297         ret = x11_verify(pr->auth, pr->auth_protocol,
 298                          pr->auth_data, pr->auth_dlen);
 299
 300         /*
 301          * If authentication failed, construct and send an error
 302          * packet, then terminate the connection.
 303          */
 304         if (!ret) {
 305             char message[] = "Authentication failed at PuTTY X11 proxy";
 306             unsigned char reply[8 + sizeof(message) + 4];
 307             int msglen = sizeof(message) - 1;   /* skip zero byte */
 308             int msgsize = (msglen + 3) & ~3;
 309             reply[0] = 0;              /* failure */
 310             reply[1] = msglen;         /* length of reason string */
 311             memcpy(reply + 2, pr->firstpkt + 2, 4);     /* major/minor proto vsn */
 312             PUT_16BIT(pr->firstpkt[0], reply + 6, msgsize >> 2);/* data len */
 313             memset(reply + 8, 0, msgsize);
 314             memcpy(reply + 8, message, msglen);
 315             sshfwd_write(pr->c, reply, 8 + msgsize);
 316             sshfwd_close(pr->c);
 317             x11_close(s);
 318             return 0;
 319         }
 320
 321         /*
 322          * Now we know we're going to accept the connection. Strip
 323          * the auth data. (TODO: if we ever work out how, we should
 324          * replace some real auth data in here.)
 325          */
 326         PUT_16BIT(pr->firstpkt[0], pr->firstpkt + 6, 0);        /* auth proto */
 327         PUT_16BIT(pr->firstpkt[0], pr->firstpkt + 8, 0);        /* auth data */
 328         sk_write(s, pr->firstpkt, 12);
 329         pr->verified = 1;
 330     }
 331
 332     /*
 333      * After initialisation, just copy data simply.
 334      */
 335
 336     return sk_write(s, data, len);
 337 }