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