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 (!len) {
 110         /* Connection has closed. */
 111         sshfwd_close(pr->c);
 112         x11_close(s);
 113         return 1;
 114     }
 115     sshfwd_write(pr->c, data, len);
 116     return 1;
 117 }
 118
 119 /*
 120  * Called to set up the raw connection.
 121  *
 122  * Returns an error message, or NULL on success.
 123  * also, fills the SocketsStructure
 124  */
 125 char *x11_init (Socket *s, char *display, void *c) {
 126     SockAddr addr;
 127     int port;
 128     char *err, *dummy_realhost;
 129     char host[128];
 130     int n, displaynum;
 131     struct X11Private *pr;
 132
 133     /*
 134      * Split up display name into host and display-number parts.
 135      */
 136     n = strcspn(display, ":");
 137     if (display[n])
 138         displaynum = atoi(display+n+1);
 139     else
 140         displaynum = 0;                /* sensible default */
 141     if (n > sizeof(host)-1)
 142         n = sizeof(host)-1;
 143     strncpy(host, display, n);
 144     host[n] = '\0';
 145
 146     /*
 147      * Try to find host.
 148      */
 149     addr = sk_namelookup(host, &dummy_realhost);
 150     if ( (err = sk_addr_error(addr)) )
 151         return err;
 152
 153     port = 6000 + displaynum;
 154
 155     /*
 156      * Open socket.
 157      */
 158     *s = sk_new(addr, port, 0, x11_receive);
 159     if ( (err = sk_socket_error(*s)) )
 160         return err;
 161
 162     pr = (struct X11Private *)smalloc(sizeof(struct X11Private));
 163     pr->auth_protocol = NULL;
 164     pr->verified = 0;
 165     pr->data_read = 0;
 166     pr->c = c;
 167
 168     sk_set_private_ptr(*s, pr);
 169     sk_addr_free(addr);
 170     return NULL;
 171 }
 172
 173 void x11_close (Socket s) {
 174     struct X11Private *pr = (struct X11Private *)sk_get_private_ptr(s);
 175
 176     if (pr->auth_protocol) {
 177         sfree(pr->auth_protocol);
 178         sfree(pr->auth_data);
 179     }
 180
 181     sfree(pr);
 182
 183     sk_close(s);
 184 }
 185
 186 /*
 187  * Called to send data down the raw connection.
 188  */
 189 void x11_send (Socket s, char *data, int len) {
 190     struct X11Private *pr = (struct X11Private *)sk_get_private_ptr(s);
 191
 192     if (s == NULL)
 193         return;
 194
 195     /*
 196      * Read the first packet.
 197      */
 198     while (len > 0 && pr->data_read < 12)
 199         pr->firstpkt[pr->data_read++] = (unsigned char)(len--, *data++);
 200     if (pr->data_read < 12)
 201         return;
 202
 203     /*
 204      * If we have not allocated the auth_protocol and auth_data
 205      * strings, do so now.
 206      */
 207     if (!pr->auth_protocol) {
 208         pr->auth_plen = GET_16BIT(pr->firstpkt[0], pr->firstpkt+6);
 209         pr->auth_dlen = GET_16BIT(pr->firstpkt[0], pr->firstpkt+8);
 210         pr->auth_psize = (pr->auth_plen + 3) &~ 3;
 211         pr->auth_dsize = (pr->auth_dlen + 3) &~ 3;
 212         /* Leave room for a terminating zero, to make our lives easier. */
 213         pr->auth_protocol = (char *)smalloc(pr->auth_psize+1);
 214         pr->auth_data = (char *)smalloc(pr->auth_dsize);
 215     }
 216
 217     /*
 218      * Read the auth_protocol and auth_data strings.
 219      */
 220     while (len > 0 && pr->data_read < 12 + pr->auth_psize)
 221         pr->auth_protocol[pr->data_read++ - 12] = (len--, *data++);
 222     while (len > 0 && pr->data_read < 12 + pr->auth_psize + pr->auth_dsize)
 223         pr->auth_data[pr->data_read++ - 12 -
 224                       pr->auth_psize] = (unsigned char)(len--, *data++);
 225     if (pr->data_read < 12 + pr->auth_psize + pr->auth_dsize)
 226         return;
 227
 228     /*
 229      * If we haven't verified the authentication, do so now.
 230      */
 231     if (!pr->verified) {
 232         int ret;
 233
 234         pr->auth_protocol[pr->auth_plen] = '\0';   /* ASCIZ */
 235         ret = x11_verify(pr->auth_protocol, pr->auth_data, pr->auth_dlen);
 236
 237         /*
 238          * If authentication failed, construct and send an error
 239          * packet, then terminate the connection.
 240          */
 241         if (!ret) {
 242             char message[] = "Authentication failed at PuTTY X11 proxy";
 243             unsigned char reply[8 + sizeof(message) + 4];
 244             int msglen = sizeof(message)-1;   /* skip zero byte */
 245             int msgsize = (msglen+3) &~ 3;
 246             reply[0] = 0;              /* failure */
 247             reply[1] = msglen;         /* length of reason string */
 248             memcpy(reply+2, pr->firstpkt+2, 4);   /* major/minor proto vsn */
 249             PUT_16BIT(pr->firstpkt[0], reply+6, msglen >> 2);   /* data len */
 250             memset(reply+8, 0, msgsize);
 251             memcpy(reply+8, message, msglen);
 252             sshfwd_write(pr->c, reply, 8+msgsize);
 253             sshfwd_close(pr->c);
 254             x11_close(s);
 255             return;
 256         }
 257
 258         /*
 259          * Now we know we're going to accept the connection. Strip
 260          * the auth data. (TODO: if we ever work out how, we should
 261          * replace some real auth data in here.)
 262          */
 263         PUT_16BIT(pr->firstpkt[0], pr->firstpkt+6, 0);   /* auth proto */
 264         PUT_16BIT(pr->firstpkt[0], pr->firstpkt+8, 0);   /* auth data */
 265         sk_write(s, pr->firstpkt, 12);
 266         pr->verified = 1;
 267     }
 268
 269     /*
 270      * After initialisation, just copy data simply.
 271      */
 272
 273     sk_write(s, data, len);
 274 }