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 X11Private {
  55     struct plug_function_table *fn;
  56     /* the above variable absolutely *must* be the first in this structure */
  57     unsigned char firstpkt[12];        /* first X data packet */
  58     char *auth_protocol;
  59     unsigned char *auth_data;
  60     int data_read, auth_plen, auth_psize, auth_dlen, auth_dsize;
  61     int verified;
  62     int throttled, throttle_override;
  63     void *c;                           /* data used by ssh.c */
  64     Socket s;
  65 };
  66
  67 void x11_close(Socket s);
  68
  69 static unsigned char x11_authdata[64];
  70 static int x11_authdatalen;
  71
  72 void x11_invent_auth(char *proto, int protomaxlen,
  73                      char *data, int datamaxlen)
  74 {
  75     char ourdata[64];
  76     int i;
  77
  78     /* MIT-MAGIC-COOKIE-1. Cookie size is 128 bits (16 bytes). */
  79     x11_authdatalen = 16;
  80     for (i = 0; i < 16; i++)
  81         x11_authdata[i] = random_byte();
  82
  83     /* Now format for the recipient. */
  84     strncpy(proto, "MIT-MAGIC-COOKIE-1", protomaxlen);
  85     ourdata[0] = '\0';
  86     for (i = 0; i < x11_authdatalen; i++)
  87         sprintf(ourdata + strlen(ourdata), "%02x", x11_authdata[i]);
  88     strncpy(data, ourdata, datamaxlen);
  89 }
  90
  91 static int x11_verify(char *proto, unsigned char *data, int dlen)
  92 {
  93     if (strcmp(proto, "MIT-MAGIC-COOKIE-1") != 0)
  94         return 0;                      /* wrong protocol attempted */
  95     if (dlen != x11_authdatalen)
  96         return 0;                      /* cookie was wrong length */
  97     if (memcmp(x11_authdata, data, dlen) != 0)
  98         return 0;                      /* cookie was wrong cookie! */
  99     return 1;
 100 }
 101
 102 static int x11_closing(Plug plug, char *error_msg, int error_code,
 103                        int calling_back)
 104 {
 105     struct X11Private *pr = (struct X11Private *) plug;
 106
 107     /*
 108      * We have no way to communicate down the forwarded connection,
 109      * so if an error occurred on the socket, we just ignore it
 110      * and treat it like a proper close.
 111      */
 112     sshfwd_close(pr->c);
 113     x11_close(pr->s);
 114     return 1;
 115 }
 116
 117 static int x11_receive(Plug plug, int urgent, char *data, int len)
 118 {
 119     struct X11Private *pr = (struct X11Private *) plug;
 120
 121     if (sshfwd_write(pr->c, data, len) > 0) {
 122         pr->throttled = 1;
 123         sk_set_frozen(pr->s, 1);
 124     }
 125
 126     return 1;
 127 }
 128
 129 static void x11_sent(Plug plug, int bufsize)
 130 {
 131     struct X11Private *pr = (struct X11Private *) plug;
 132
 133     sshfwd_unthrottle(pr->c, bufsize);
 134 }
 135
 136 /*
 137  * Called to set up the raw connection.
 138  *
 139  * Returns an error message, or NULL on success.
 140  * also, fills the SocketsStructure
 141  */
 142 char *x11_init(Socket * s, char *display, void *c)
 143 {
 144     static struct plug_function_table fn_table = {
 145         x11_closing,
 146         x11_receive,
 147         x11_sent,
 148         NULL
 149     };
 150
 151     SockAddr addr;
 152     int port;
 153     char *err, *dummy_realhost;
 154     char host[128];
 155     int n, displaynum;
 156     struct X11Private *pr;
 157
 158     /*
 159      * Split up display name into host and display-number parts.
 160      */
 161     n = strcspn(display, ":");
 162     if (display[n])
 163         displaynum = atoi(display + n + 1);
 164     else
 165         displaynum = 0;                /* sensible default */
 166     if (n > sizeof(host) - 1)
 167         n = sizeof(host) - 1;
 168     strncpy(host, display, n);
 169     host[n] = '\0';
 170
 171     /*
 172      * Try to find host.
 173      */
 174     addr = sk_namelookup(host, &dummy_realhost);
 175     if ((err = sk_addr_error(addr)))
 176         return err;
 177
 178     port = 6000 + displaynum;
 179
 180     /*
 181      * Open socket.
 182      */
 183     pr = (struct X11Private *) smalloc(sizeof(struct X11Private));
 184     pr->fn = &fn_table;
 185     pr->auth_protocol = NULL;
 186     pr->verified = 0;
 187     pr->data_read = 0;
 188     pr->throttled = pr->throttle_override = 0;
 189     pr->c = c;
 190
 191     pr->s = *s = sk_new(addr, port, 0, 1, 0, (Plug) pr);
 192     if ((err = sk_socket_error(*s))) {
 193         sfree(pr);
 194         return err;
 195     }
 196
 197     sk_set_private_ptr(*s, pr);
 198     sk_addr_free(addr);
 199     return NULL;
 200 }
 201
 202 void x11_close(Socket s)
 203 {
 204     struct X11Private *pr;
 205     if (!s)
 206         return;
 207     pr = (struct X11Private *) sk_get_private_ptr(s);
 208     if (pr->auth_protocol) {
 209         sfree(pr->auth_protocol);
 210         sfree(pr->auth_data);
 211     }
 212
 213     sfree(pr);
 214
 215     sk_close(s);
 216 }
 217
 218 void x11_unthrottle(Socket s)
 219 {
 220     struct X11Private *pr;
 221     if (!s)
 222         return;
 223     pr = (struct X11Private *) sk_get_private_ptr(s);
 224
 225     pr->throttled = 0;
 226     sk_set_frozen(s, pr->throttled || pr->throttle_override);
 227 }
 228
 229 void x11_override_throttle(Socket s, int enable)
 230 {
 231     struct X11Private *pr;
 232     if (!s)
 233         return;
 234     pr = (struct X11Private *) sk_get_private_ptr(s);
 235
 236     pr->throttle_override = enable;
 237     sk_set_frozen(s, pr->throttled || pr->throttle_override);
 238 }
 239
 240 /*
 241  * Called to send data down the raw connection.
 242  */
 243 int x11_send(Socket s, char *data, int len)
 244 {
 245     struct X11Private *pr = (struct X11Private *) sk_get_private_ptr(s);
 246
 247     if (s == NULL)
 248         return 0;
 249
 250     /*
 251      * Read the first packet.
 252      */
 253     while (len > 0 && pr->data_read < 12)
 254         pr->firstpkt[pr->data_read++] = (unsigned char) (len--, *data++);
 255     if (pr->data_read < 12)
 256         return 0;
 257
 258     /*
 259      * If we have not allocated the auth_protocol and auth_data
 260      * strings, do so now.
 261      */
 262     if (!pr->auth_protocol) {
 263         pr->auth_plen = GET_16BIT(pr->firstpkt[0], pr->firstpkt + 6);
 264         pr->auth_dlen = GET_16BIT(pr->firstpkt[0], pr->firstpkt + 8);
 265         pr->auth_psize = (pr->auth_plen + 3) & ~3;
 266         pr->auth_dsize = (pr->auth_dlen + 3) & ~3;
 267         /* Leave room for a terminating zero, to make our lives easier. */
 268         pr->auth_protocol = (char *) smalloc(pr->auth_psize + 1);
 269         pr->auth_data = (char *) smalloc(pr->auth_dsize);
 270     }
 271
 272     /*
 273      * Read the auth_protocol and auth_data strings.
 274      */
 275     while (len > 0 && pr->data_read < 12 + pr->auth_psize)
 276         pr->auth_protocol[pr->data_read++ - 12] = (len--, *data++);
 277     while (len > 0 && pr->data_read < 12 + pr->auth_psize + pr->auth_dsize)
 278         pr->auth_data[pr->data_read++ - 12 -
 279                       pr->auth_psize] = (unsigned char) (len--, *data++);
 280     if (pr->data_read < 12 + pr->auth_psize + pr->auth_dsize)
 281         return 0;
 282
 283     /*
 284      * If we haven't verified the authentication, do so now.
 285      */
 286     if (!pr->verified) {
 287         int ret;
 288
 289         pr->auth_protocol[pr->auth_plen] = '\0';        /* ASCIZ */
 290         ret = x11_verify(pr->auth_protocol, pr->auth_data, pr->auth_dlen);
 291
 292         /*
 293          * If authentication failed, construct and send an error
 294          * packet, then terminate the connection.
 295          */
 296         if (!ret) {
 297             char message[] = "Authentication failed at PuTTY X11 proxy";
 298             unsigned char reply[8 + sizeof(message) + 4];
 299             int msglen = sizeof(message) - 1;   /* skip zero byte */
 300             int msgsize = (msglen + 3) & ~3;
 301             reply[0] = 0;              /* failure */
 302             reply[1] = msglen;         /* length of reason string */
 303             memcpy(reply + 2, pr->firstpkt + 2, 4);     /* major/minor proto vsn */
 304             PUT_16BIT(pr->firstpkt[0], reply + 6, msgsize >> 2);/* data len */
 305             memset(reply + 8, 0, msgsize);
 306             memcpy(reply + 8, message, msglen);
 307             sshfwd_write(pr->c, reply, 8 + msgsize);
 308             sshfwd_close(pr->c);
 309             x11_close(s);
 310             return 0;
 311         }
 312
 313         /*
 314          * Now we know we're going to accept the connection. Strip
 315          * the auth data. (TODO: if we ever work out how, we should
 316          * replace some real auth data in here.)
 317          */
 318         PUT_16BIT(pr->firstpkt[0], pr->firstpkt + 6, 0);        /* auth proto */
 319         PUT_16BIT(pr->firstpkt[0], pr->firstpkt + 8, 0);        /* auth data */
 320         sk_write(s, pr->firstpkt, 12);
 321         pr->verified = 1;
 322     }
 323
 324     /*
 325      * After initialisation, just copy data simply.
 326      */
 327
 328     return sk_write(s, data, len);
 329 }