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