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 #define GET_32BIT_LSB_FIRST(cp) \
   9   (((unsigned long)(unsigned char)(cp)[0]) | \
  10   ((unsigned long)(unsigned char)(cp)[1] << 8) | \
  11   ((unsigned long)(unsigned char)(cp)[2] << 16) | \
  12   ((unsigned long)(unsigned char)(cp)[3] << 24))
  13
  14 #define PUT_32BIT_LSB_FIRST(cp, value) ( \
  15   (cp)[0] = (value), \
  16   (cp)[1] = (value) >> 8, \
  17   (cp)[2] = (value) >> 16, \
  18   (cp)[3] = (value) >> 24 )
  19
  20 #define GET_16BIT_LSB_FIRST(cp) \
  21   (((unsigned long)(unsigned char)(cp)[0]) | \
  22   ((unsigned long)(unsigned char)(cp)[1] << 8))
  23
  24 #define PUT_16BIT_LSB_FIRST(cp, value) ( \
  25   (cp)[0] = (value), \
  26   (cp)[1] = (value) >> 8 )
  27
  28 #define GET_32BIT_MSB_FIRST(cp) \
  29   (((unsigned long)(unsigned char)(cp)[0] << 24) | \
  30   ((unsigned long)(unsigned char)(cp)[1] << 16) | \
  31   ((unsigned long)(unsigned char)(cp)[2] << 8) | \
  32   ((unsigned long)(unsigned char)(cp)[3]))
  33
  34 #define PUT_32BIT_MSB_FIRST(cp, value) ( \
  35   (cp)[0] = (value) >> 24, \
  36   (cp)[1] = (value) >> 16, \
  37   (cp)[2] = (value) >> 8, \
  38   (cp)[3] = (value) )
  39
  40 #define GET_16BIT_MSB_FIRST(cp) \
  41   (((unsigned long)(unsigned char)(cp)[0] << 8) | \
  42   ((unsigned long)(unsigned char)(cp)[1]))
  43
  44 #define PUT_16BIT_MSB_FIRST(cp, value) ( \
  45   (cp)[0] = (value) >> 8, \
  46   (cp)[1] = (value) )
  47
  48 #define GET_16BIT(endian, cp) \
  49   (endian=='B' ? GET_16BIT_MSB_FIRST(cp) : GET_16BIT_LSB_FIRST(cp))
  50
  51 #define PUT_16BIT(endian, cp, val) \
  52   (endian=='B' ? PUT_16BIT_MSB_FIRST(cp, val) : PUT_16BIT_LSB_FIRST(cp, val))
  53
  54 struct X11Auth {
  55     unsigned char data[64];
  56     int len;
  57 };
  58
  59 struct X11Private {
  60     const struct plug_function_table *fn;
  61     /* the above variable absolutely *must* be the first in this structure */
  62     unsigned char firstpkt[12];        /* first X data packet */
  63     struct X11Auth *auth;
  64     char *auth_protocol;
  65     unsigned char *auth_data;
  66     int data_read, auth_plen, auth_psize, auth_dlen, auth_dsize;
  67     int verified;
  68     int throttled, throttle_override;
  69     void *c;                           /* data used by ssh.c */
  70     Socket s;
  71 };
  72
  73 void x11_close(Socket s);
  74
  75 void *x11_invent_auth(char *proto, int protomaxlen,
  76                      char *data, int datamaxlen)
  77 {
  78     struct X11Auth *auth = smalloc(sizeof(struct X11Auth));
  79     char ourdata[64];
  80     int i;
  81
  82     /* MIT-MAGIC-COOKIE-1. Cookie size is 128 bits (16 bytes). */
  83     auth->len = 16;
  84     for (i = 0; i < 16; i++)
  85         auth->data[i] = random_byte();
  86
  87     /* Now format for the recipient. */
  88     strncpy(proto, "MIT-MAGIC-COOKIE-1", protomaxlen);
  89     ourdata[0] = '\0';
  90     for (i = 0; i < auth->len; i++)
  91         sprintf(ourdata + strlen(ourdata), "%02x", auth->data[i]);
  92     strncpy(data, ourdata, datamaxlen);
  93
  94     return auth;
  95 }
  96
  97 static int x11_verify(struct X11Auth *auth,
  98                       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 != auth->len)
 103         return 0;                      /* cookie was wrong length */
 104     if (memcmp(auth->data, 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, void *auth)
 150 {
 151     static const 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->auth = (struct X11Auth *)auth;
 194     pr->verified = 0;
 195     pr->data_read = 0;
 196     pr->throttled = pr->throttle_override = 0;
 197     pr->c = c;
 198
 199     pr->s = *s = new_connection(addr, dummy_realhost, port, 0, 1, 0, (Plug) pr);
 200     if ((err = sk_socket_error(*s))) {
 201         sfree(pr);
 202         return err;
 203     }
 204
 205     sk_set_private_ptr(*s, pr);
 206     sk_addr_free(addr);
 207     return NULL;
 208 }
 209
 210 void x11_close(Socket s)
 211 {
 212     struct X11Private *pr;
 213     if (!s)
 214         return;
 215     pr = (struct X11Private *) sk_get_private_ptr(s);
 216     if (pr->auth_protocol) {
 217         sfree(pr->auth_protocol);
 218         sfree(pr->auth_data);
 219     }
 220
 221     sfree(pr);
 222
 223     sk_close(s);
 224 }
 225
 226 void x11_unthrottle(Socket s)
 227 {
 228     struct X11Private *pr;
 229     if (!s)
 230         return;
 231     pr = (struct X11Private *) sk_get_private_ptr(s);
 232
 233     pr->throttled = 0;
 234     sk_set_frozen(s, pr->throttled || pr->throttle_override);
 235 }
 236
 237 void x11_override_throttle(Socket s, int enable)
 238 {
 239     struct X11Private *pr;
 240     if (!s)
 241         return;
 242     pr = (struct X11Private *) sk_get_private_ptr(s);
 243
 244     pr->throttle_override = enable;
 245     sk_set_frozen(s, pr->throttled || pr->throttle_override);
 246 }
 247
 248 /*
 249  * Called to send data down the raw connection.
 250  */
 251 int x11_send(Socket s, char *data, int len)
 252 {
 253     struct X11Private *pr = (struct X11Private *) sk_get_private_ptr(s);
 254
 255     if (s == NULL)
 256         return 0;
 257
 258     /*
 259      * Read the first packet.
 260      */
 261     while (len > 0 && pr->data_read < 12)
 262         pr->firstpkt[pr->data_read++] = (unsigned char) (len--, *data++);
 263     if (pr->data_read < 12)
 264         return 0;
 265
 266     /*
 267      * If we have not allocated the auth_protocol and auth_data
 268      * strings, do so now.
 269      */
 270     if (!pr->auth_protocol) {
 271         pr->auth_plen = GET_16BIT(pr->firstpkt[0], pr->firstpkt + 6);
 272         pr->auth_dlen = GET_16BIT(pr->firstpkt[0], pr->firstpkt + 8);
 273         pr->auth_psize = (pr->auth_plen + 3) & ~3;
 274         pr->auth_dsize = (pr->auth_dlen + 3) & ~3;
 275         /* Leave room for a terminating zero, to make our lives easier. */
 276         pr->auth_protocol = (char *) smalloc(pr->auth_psize + 1);
 277         pr->auth_data = (char *) smalloc(pr->auth_dsize);
 278     }
 279
 280     /*
 281      * Read the auth_protocol and auth_data strings.
 282      */
 283     while (len > 0 && pr->data_read < 12 + pr->auth_psize)
 284         pr->auth_protocol[pr->data_read++ - 12] = (len--, *data++);
 285     while (len > 0 && pr->data_read < 12 + pr->auth_psize + pr->auth_dsize)
 286         pr->auth_data[pr->data_read++ - 12 -
 287                       pr->auth_psize] = (unsigned char) (len--, *data++);
 288     if (pr->data_read < 12 + pr->auth_psize + pr->auth_dsize)
 289         return 0;
 290
 291     /*
 292      * If we haven't verified the authentication, do so now.
 293      */
 294     if (!pr->verified) {
 295         int ret;
 296
 297         pr->auth_protocol[pr->auth_plen] = '\0';        /* ASCIZ */
 298         ret = x11_verify(pr->auth, pr->auth_protocol,
 299                          pr->auth_data, pr->auth_dlen);
 300
 301         /*
 302          * If authentication failed, construct and send an error
 303          * packet, then terminate the connection.
 304          */
 305         if (!ret) {
 306             char message[] = "Authentication failed at PuTTY X11 proxy";
 307             unsigned char reply[8 + sizeof(message) + 4];
 308             int msglen = sizeof(message) - 1;   /* skip zero byte */
 309             int msgsize = (msglen + 3) & ~3;
 310             reply[0] = 0;              /* failure */
 311             reply[1] = msglen;         /* length of reason string */
 312             memcpy(reply + 2, pr->firstpkt + 2, 4);     /* major/minor proto vsn */
 313             PUT_16BIT(pr->firstpkt[0], reply + 6, msgsize >> 2);/* data len */
 314             memset(reply + 8, 0, msgsize);
 315             memcpy(reply + 8, message, msglen);
 316             sshfwd_write(pr->c, reply, 8 + msgsize);
 317             sshfwd_close(pr->c);
 318             x11_close(s);
 319             return 0;
 320         }
 321
 322         /*
 323          * Now we know we're going to accept the connection. Strip
 324          * the auth data. (TODO: if we ever work out how, we should
 325          * replace some real auth data in here.)
 326          */
 327         PUT_16BIT(pr->firstpkt[0], pr->firstpkt + 6, 0);        /* auth proto */
 328         PUT_16BIT(pr->firstpkt[0], pr->firstpkt + 8, 0);        /* auth data */
 329         sk_write(s, pr->firstpkt, 12);
 330         pr->verified = 1;
 331     }
 332
 333     /*
 334      * After initialisation, just copy data simply.
 335      */
 336
 337     return sk_write(s, data, len);
 338 }