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 struct X11Private {
  62     struct plug_function_table *fn;
  63     /* the above variable absolutely *must* be the first in this structure */
  64     unsigned char firstpkt[12];        /* first X data packet */
  65     char *auth_protocol;
  66     unsigned char *auth_data;
  67     int data_read, auth_plen, auth_psize, auth_dlen, auth_dsize;
  68     int verified;
  69     int throttled, throttle_override;
  70     void *c;                           /* data used by ssh.c */
  71     Socket s;
  72 };
  73
  74 void x11_close(Socket s);
  75
  76 static unsigned char x11_authdata[64];
  77 static int x11_authdatalen;
  78
  79 void x11_invent_auth(char *proto, int protomaxlen,
  80                      char *data, int datamaxlen)
  81 {
  82     char ourdata[64];
  83     int i;
  84
  85     /* MIT-MAGIC-COOKIE-1. Cookie size is 128 bits (16 bytes). */
  86     x11_authdatalen = 16;
  87     for (i = 0; i < 16; i++)
  88         x11_authdata[i] = random_byte();
  89
  90     /* Now format for the recipient. */
  91     strncpy(proto, "MIT-MAGIC-COOKIE-1", protomaxlen);
  92     ourdata[0] = '\0';
  93     for (i = 0; i < x11_authdatalen; i++)
  94         sprintf(ourdata + strlen(ourdata), "%02x", x11_authdata[i]);
  95     strncpy(data, ourdata, datamaxlen);
  96 }
  97
  98 static int x11_verify(char *proto, unsigned char *data, int dlen)
  99 {
 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,
 110                        int calling_back)
 111 {
 112     struct X11Private *pr = (struct X11Private *) plug;
 113
 114     /*
 115      * We have no way to communicate down the forwarded connection,
 116      * so if an error occurred on the socket, we just ignore it
 117      * and treat it like a proper close.
 118      */
 119     sshfwd_close(pr->c);
 120     x11_close(pr->s);
 121     return 1;
 122 }
 123
 124 static int x11_receive(Plug plug, int urgent, char *data, int len)
 125 {
 126     struct X11Private *pr = (struct X11Private *) plug;
 127
 128     if (sshfwd_write(pr->c, data, len) > 0) {
 129         pr->throttled = 1;
 130         sk_set_frozen(pr->s, 1);
 131     }
 132
 133     return 1;
 134 }
 135
 136 static void x11_sent(Plug plug, int bufsize)
 137 {
 138     struct X11Private *pr = (struct X11Private *) plug;
 139
 140     sshfwd_unthrottle(pr->c, bufsize);
 141 }
 142
 143 /*
 144  * Called to set up the raw connection.
 145  *
 146  * Returns an error message, or NULL on success.
 147  * also, fills the SocketsStructure
 148  */
 149 char *x11_init(Socket * s, char *display, void *c)
 150 {
 151     static struct plug_function_table fn_table = {
 152         x11_closing,
 153         x11_receive,
 154         x11_sent,
 155         NULL
 156     };
 157
 158     SockAddr addr;
 159     int port;
 160     char *err, *dummy_realhost;
 161     char host[128];
 162     int n, displaynum;
 163     struct X11Private *pr;
 164
 165     /*
 166      * Split up display name into host and display-number parts.
 167      */
 168     n = strcspn(display, ":");
 169     if (display[n])
 170         displaynum = atoi(display + n + 1);
 171     else
 172         displaynum = 0;                /* sensible default */
 173     if (n > sizeof(host) - 1)
 174         n = sizeof(host) - 1;
 175     strncpy(host, display, n);
 176     host[n] = '\0';
 177
 178     /*
 179      * Try to find host.
 180      */
 181     addr = sk_namelookup(host, &dummy_realhost);
 182     if ((err = sk_addr_error(addr)))
 183         return err;
 184
 185     port = 6000 + displaynum;
 186
 187     /*
 188      * Open socket.
 189      */
 190     pr = (struct X11Private *) smalloc(sizeof(struct X11Private));
 191     pr->fn = &fn_table;
 192     pr->auth_protocol = NULL;
 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 = sk_new(addr, 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_protocol, pr->auth_data, pr->auth_dlen);
 298
 299         /*
 300          * If authentication failed, construct and send an error
 301          * packet, then terminate the connection.
 302          */
 303         if (!ret) {
 304             char message[] = "Authentication failed at PuTTY X11 proxy";
 305             unsigned char reply[8 + sizeof(message) + 4];
 306             int msglen = sizeof(message) - 1;   /* skip zero byte */
 307             int msgsize = (msglen + 3) & ~3;
 308             reply[0] = 0;              /* failure */
 309             reply[1] = msglen;         /* length of reason string */
 310             memcpy(reply + 2, pr->firstpkt + 2, 4);     /* major/minor proto vsn */
 311             PUT_16BIT(pr->firstpkt[0], reply + 6, msgsize >> 2);/* data len */
 312             memset(reply + 8, 0, msgsize);
 313             memcpy(reply + 8, message, msglen);
 314             sshfwd_write(pr->c, reply, 8 + msgsize);
 315             sshfwd_close(pr->c);
 316             x11_close(s);
 317             return 0;
 318         }
 319
 320         /*
 321          * Now we know we're going to accept the connection. Strip
 322          * the auth data. (TODO: if we ever work out how, we should
 323          * replace some real auth data in here.)
 324          */
 325         PUT_16BIT(pr->firstpkt[0], pr->firstpkt + 6, 0);        /* auth proto */
 326         PUT_16BIT(pr->firstpkt[0], pr->firstpkt + 8, 0);        /* auth data */
 327         sk_write(s, pr->firstpkt, 12);
 328         pr->verified = 1;
 329     }
 330
 331     /*
 332      * After initialisation, just copy data simply.
 333      */
 334
 335     return sk_write(s, data, len);
 336 }