| 1 | #include <stdio.h> |
| 2 | #include <stdlib.h> |
| 3 | #include <assert.h> |
| 4 | #include <time.h> |
| 5 | |
| 6 | #include "putty.h" |
| 7 | #include "ssh.h" |
| 8 | |
| 9 | #define GET_32BIT_LSB_FIRST(cp) \ |
| 10 | (((unsigned long)(unsigned char)(cp)[0]) | \ |
| 11 | ((unsigned long)(unsigned char)(cp)[1] << 8) | \ |
| 12 | ((unsigned long)(unsigned char)(cp)[2] << 16) | \ |
| 13 | ((unsigned long)(unsigned char)(cp)[3] << 24)) |
| 14 | |
| 15 | #define PUT_32BIT_LSB_FIRST(cp, value) ( \ |
| 16 | (cp)[0] = (value), \ |
| 17 | (cp)[1] = (value) >> 8, \ |
| 18 | (cp)[2] = (value) >> 16, \ |
| 19 | (cp)[3] = (value) >> 24 ) |
| 20 | |
| 21 | #define GET_16BIT_LSB_FIRST(cp) \ |
| 22 | (((unsigned long)(unsigned char)(cp)[0]) | \ |
| 23 | ((unsigned long)(unsigned char)(cp)[1] << 8)) |
| 24 | |
| 25 | #define PUT_16BIT_LSB_FIRST(cp, value) ( \ |
| 26 | (cp)[0] = (value), \ |
| 27 | (cp)[1] = (value) >> 8 ) |
| 28 | |
| 29 | #define GET_32BIT_MSB_FIRST(cp) \ |
| 30 | (((unsigned long)(unsigned char)(cp)[0] << 24) | \ |
| 31 | ((unsigned long)(unsigned char)(cp)[1] << 16) | \ |
| 32 | ((unsigned long)(unsigned char)(cp)[2] << 8) | \ |
| 33 | ((unsigned long)(unsigned char)(cp)[3])) |
| 34 | |
| 35 | #define PUT_32BIT_MSB_FIRST(cp, value) ( \ |
| 36 | (cp)[0] = (value) >> 24, \ |
| 37 | (cp)[1] = (value) >> 16, \ |
| 38 | (cp)[2] = (value) >> 8, \ |
| 39 | (cp)[3] = (value) ) |
| 40 | |
| 41 | #define GET_16BIT_MSB_FIRST(cp) \ |
| 42 | (((unsigned long)(unsigned char)(cp)[0] << 8) | \ |
| 43 | ((unsigned long)(unsigned char)(cp)[1])) |
| 44 | |
| 45 | #define PUT_16BIT_MSB_FIRST(cp, value) ( \ |
| 46 | (cp)[0] = (value) >> 8, \ |
| 47 | (cp)[1] = (value) ) |
| 48 | |
| 49 | #define GET_16BIT(endian, cp) \ |
| 50 | (endian=='B' ? GET_16BIT_MSB_FIRST(cp) : GET_16BIT_LSB_FIRST(cp)) |
| 51 | |
| 52 | #define PUT_16BIT(endian, cp, val) \ |
| 53 | (endian=='B' ? PUT_16BIT_MSB_FIRST(cp, val) : PUT_16BIT_LSB_FIRST(cp, val)) |
| 54 | |
| 55 | const char *const x11_authnames[] = { |
| 56 | "", "MIT-MAGIC-COOKIE-1", "XDM-AUTHORIZATION-1" |
| 57 | }; |
| 58 | |
| 59 | struct X11Auth { |
| 60 | unsigned char fakedata[64], realdata[64]; |
| 61 | int fakeproto, realproto; |
| 62 | int fakelen, reallen; |
| 63 | }; |
| 64 | |
| 65 | extern void platform_get_x11_auth(char *display, int *proto, |
| 66 | unsigned char *data, int *datalen); |
| 67 | |
| 68 | struct X11Private { |
| 69 | const struct plug_function_table *fn; |
| 70 | /* the above variable absolutely *must* be the first in this structure */ |
| 71 | unsigned char firstpkt[12]; /* first X data packet */ |
| 72 | struct X11Auth *auth; |
| 73 | char *auth_protocol; |
| 74 | unsigned char *auth_data; |
| 75 | int data_read, auth_plen, auth_psize, auth_dlen, auth_dsize; |
| 76 | int verified; |
| 77 | int throttled, throttle_override; |
| 78 | void *c; /* data used by ssh.c */ |
| 79 | Socket s; |
| 80 | }; |
| 81 | |
| 82 | void *x11_invent_auth(char *proto, int protomaxlen, |
| 83 | char *data, int datamaxlen) |
| 84 | { |
| 85 | struct X11Auth *auth = smalloc(sizeof(struct X11Auth)); |
| 86 | char ourdata[64]; |
| 87 | int i; |
| 88 | |
| 89 | auth->fakeproto = X11_MIT; |
| 90 | |
| 91 | /* MIT-MAGIC-COOKIE-1. Cookie size is 128 bits (16 bytes). */ |
| 92 | auth->fakelen = 16; |
| 93 | for (i = 0; i < 16; i++) |
| 94 | auth->fakedata[i] = random_byte(); |
| 95 | |
| 96 | /* Now format for the recipient. */ |
| 97 | strncpy(proto, x11_authnames[auth->fakeproto], protomaxlen); |
| 98 | ourdata[0] = '\0'; |
| 99 | for (i = 0; i < auth->fakelen; i++) |
| 100 | sprintf(ourdata + strlen(ourdata), "%02x", auth->fakedata[i]); |
| 101 | strncpy(data, ourdata, datamaxlen); |
| 102 | |
| 103 | return auth; |
| 104 | } |
| 105 | |
| 106 | /* |
| 107 | * Fetch the real auth data for a given display string, and store |
| 108 | * it in an X11Auth structure. Returns NULL on success, or an error |
| 109 | * string. |
| 110 | */ |
| 111 | void x11_get_real_auth(void *authv, char *display) |
| 112 | { |
| 113 | struct X11Auth *auth = (struct X11Auth *)authv; |
| 114 | |
| 115 | auth->realproto = X11_NO_AUTH; /* in case next call does nothing */ |
| 116 | |
| 117 | auth->reallen = sizeof(auth->realdata); |
| 118 | platform_get_x11_auth(display, &auth->realproto, |
| 119 | auth->realdata, &auth->reallen); |
| 120 | } |
| 121 | |
| 122 | static int x11_verify(struct X11Auth *auth, |
| 123 | char *proto, unsigned char *data, int dlen) |
| 124 | { |
| 125 | if (strcmp(proto, x11_authnames[auth->fakeproto]) != 0) |
| 126 | return 0; /* wrong protocol attempted */ |
| 127 | if (auth->fakeproto == X11_MIT) { |
| 128 | if (dlen != auth->fakelen) |
| 129 | return 0; /* cookie was wrong length */ |
| 130 | if (memcmp(auth->fakedata, data, dlen) != 0) |
| 131 | return 0; /* cookie was wrong cookie! */ |
| 132 | } |
| 133 | /* implement other protocols here if ever required */ |
| 134 | return 1; |
| 135 | } |
| 136 | |
| 137 | static int x11_closing(Plug plug, char *error_msg, int error_code, |
| 138 | int calling_back) |
| 139 | { |
| 140 | struct X11Private *pr = (struct X11Private *) plug; |
| 141 | |
| 142 | /* |
| 143 | * We have no way to communicate down the forwarded connection, |
| 144 | * so if an error occurred on the socket, we just ignore it |
| 145 | * and treat it like a proper close. |
| 146 | */ |
| 147 | sshfwd_close(pr->c); |
| 148 | x11_close(pr->s); |
| 149 | return 1; |
| 150 | } |
| 151 | |
| 152 | static int x11_receive(Plug plug, int urgent, char *data, int len) |
| 153 | { |
| 154 | struct X11Private *pr = (struct X11Private *) plug; |
| 155 | |
| 156 | if (sshfwd_write(pr->c, data, len) > 0) { |
| 157 | pr->throttled = 1; |
| 158 | sk_set_frozen(pr->s, 1); |
| 159 | } |
| 160 | |
| 161 | return 1; |
| 162 | } |
| 163 | |
| 164 | static void x11_sent(Plug plug, int bufsize) |
| 165 | { |
| 166 | struct X11Private *pr = (struct X11Private *) plug; |
| 167 | |
| 168 | sshfwd_unthrottle(pr->c, bufsize); |
| 169 | } |
| 170 | |
| 171 | /* |
| 172 | * When setting up X forwarding, we should send the screen number |
| 173 | * from the specified local display. This function extracts it from |
| 174 | * the display string. |
| 175 | */ |
| 176 | int x11_get_screen_number(char *display) |
| 177 | { |
| 178 | int n; |
| 179 | |
| 180 | n = strcspn(display, ":"); |
| 181 | if (!display[n]) |
| 182 | return 0; |
| 183 | n = strcspn(display, "."); |
| 184 | if (!display[n]) |
| 185 | return 0; |
| 186 | return atoi(display + n + 1); |
| 187 | } |
| 188 | |
| 189 | /* |
| 190 | * Called to set up the raw connection. |
| 191 | * |
| 192 | * Returns an error message, or NULL on success. |
| 193 | * also, fills the SocketsStructure |
| 194 | */ |
| 195 | char *x11_init(Socket * s, char *display, void *c, void *auth) |
| 196 | { |
| 197 | static const struct plug_function_table fn_table = { |
| 198 | x11_closing, |
| 199 | x11_receive, |
| 200 | x11_sent, |
| 201 | NULL |
| 202 | }; |
| 203 | |
| 204 | SockAddr addr; |
| 205 | int port; |
| 206 | char *err, *dummy_realhost; |
| 207 | char host[128]; |
| 208 | int n, displaynum; |
| 209 | struct X11Private *pr; |
| 210 | |
| 211 | /* |
| 212 | * Split up display name into host and display-number parts. |
| 213 | */ |
| 214 | n = strcspn(display, ":"); |
| 215 | if (display[n]) |
| 216 | displaynum = atoi(display + n + 1); |
| 217 | else |
| 218 | displaynum = 0; /* sensible default */ |
| 219 | if (n > sizeof(host) - 1) |
| 220 | n = sizeof(host) - 1; |
| 221 | if (n > 0) { |
| 222 | strncpy(host, display, n); |
| 223 | host[n] = '\0'; |
| 224 | } else { |
| 225 | /* |
| 226 | * Local display numbers, particularly on Unix, often omit |
| 227 | * the display part completely. |
| 228 | */ |
| 229 | strcpy(host, "localhost"); |
| 230 | } |
| 231 | |
| 232 | port = 6000 + displaynum; |
| 233 | |
| 234 | /* |
| 235 | * Try to find host. |
| 236 | */ |
| 237 | addr = name_lookup(host, port, &dummy_realhost); |
| 238 | if ((err = sk_addr_error(addr)) != NULL) |
| 239 | return err; |
| 240 | |
| 241 | /* |
| 242 | * Open socket. |
| 243 | */ |
| 244 | pr = (struct X11Private *) smalloc(sizeof(struct X11Private)); |
| 245 | pr->fn = &fn_table; |
| 246 | pr->auth_protocol = NULL; |
| 247 | pr->auth = (struct X11Auth *)auth; |
| 248 | pr->verified = 0; |
| 249 | pr->data_read = 0; |
| 250 | pr->throttled = pr->throttle_override = 0; |
| 251 | pr->c = c; |
| 252 | |
| 253 | pr->s = *s = new_connection(addr, dummy_realhost, port, 0, 1, 0, (Plug) pr); |
| 254 | if ((err = sk_socket_error(*s)) != NULL) { |
| 255 | sfree(pr); |
| 256 | return err; |
| 257 | } |
| 258 | |
| 259 | sk_set_private_ptr(*s, pr); |
| 260 | sk_addr_free(addr); |
| 261 | return NULL; |
| 262 | } |
| 263 | |
| 264 | void x11_close(Socket s) |
| 265 | { |
| 266 | struct X11Private *pr; |
| 267 | if (!s) |
| 268 | return; |
| 269 | pr = (struct X11Private *) sk_get_private_ptr(s); |
| 270 | if (pr->auth_protocol) { |
| 271 | sfree(pr->auth_protocol); |
| 272 | sfree(pr->auth_data); |
| 273 | } |
| 274 | |
| 275 | sfree(pr); |
| 276 | |
| 277 | sk_close(s); |
| 278 | } |
| 279 | |
| 280 | void x11_unthrottle(Socket s) |
| 281 | { |
| 282 | struct X11Private *pr; |
| 283 | if (!s) |
| 284 | return; |
| 285 | pr = (struct X11Private *) sk_get_private_ptr(s); |
| 286 | |
| 287 | pr->throttled = 0; |
| 288 | sk_set_frozen(s, pr->throttled || pr->throttle_override); |
| 289 | } |
| 290 | |
| 291 | void x11_override_throttle(Socket s, int enable) |
| 292 | { |
| 293 | struct X11Private *pr; |
| 294 | if (!s) |
| 295 | return; |
| 296 | pr = (struct X11Private *) sk_get_private_ptr(s); |
| 297 | |
| 298 | pr->throttle_override = enable; |
| 299 | sk_set_frozen(s, pr->throttled || pr->throttle_override); |
| 300 | } |
| 301 | |
| 302 | /* |
| 303 | * Called to send data down the raw connection. |
| 304 | */ |
| 305 | int x11_send(Socket s, char *data, int len) |
| 306 | { |
| 307 | struct X11Private *pr = (struct X11Private *) sk_get_private_ptr(s); |
| 308 | |
| 309 | if (s == NULL) |
| 310 | return 0; |
| 311 | |
| 312 | /* |
| 313 | * Read the first packet. |
| 314 | */ |
| 315 | while (len > 0 && pr->data_read < 12) |
| 316 | pr->firstpkt[pr->data_read++] = (unsigned char) (len--, *data++); |
| 317 | if (pr->data_read < 12) |
| 318 | return 0; |
| 319 | |
| 320 | /* |
| 321 | * If we have not allocated the auth_protocol and auth_data |
| 322 | * strings, do so now. |
| 323 | */ |
| 324 | if (!pr->auth_protocol) { |
| 325 | pr->auth_plen = GET_16BIT(pr->firstpkt[0], pr->firstpkt + 6); |
| 326 | pr->auth_dlen = GET_16BIT(pr->firstpkt[0], pr->firstpkt + 8); |
| 327 | pr->auth_psize = (pr->auth_plen + 3) & ~3; |
| 328 | pr->auth_dsize = (pr->auth_dlen + 3) & ~3; |
| 329 | /* Leave room for a terminating zero, to make our lives easier. */ |
| 330 | pr->auth_protocol = (char *) smalloc(pr->auth_psize + 1); |
| 331 | pr->auth_data = (unsigned char *) smalloc(pr->auth_dsize); |
| 332 | } |
| 333 | |
| 334 | /* |
| 335 | * Read the auth_protocol and auth_data strings. |
| 336 | */ |
| 337 | while (len > 0 && pr->data_read < 12 + pr->auth_psize) |
| 338 | pr->auth_protocol[pr->data_read++ - 12] = (len--, *data++); |
| 339 | while (len > 0 && pr->data_read < 12 + pr->auth_psize + pr->auth_dsize) |
| 340 | pr->auth_data[pr->data_read++ - 12 - |
| 341 | pr->auth_psize] = (unsigned char) (len--, *data++); |
| 342 | if (pr->data_read < 12 + pr->auth_psize + pr->auth_dsize) |
| 343 | return 0; |
| 344 | |
| 345 | /* |
| 346 | * If we haven't verified the authentication, do so now. |
| 347 | */ |
| 348 | if (!pr->verified) { |
| 349 | int ret; |
| 350 | |
| 351 | pr->auth_protocol[pr->auth_plen] = '\0'; /* ASCIZ */ |
| 352 | ret = x11_verify(pr->auth, pr->auth_protocol, |
| 353 | pr->auth_data, pr->auth_dlen); |
| 354 | |
| 355 | /* |
| 356 | * If authentication failed, construct and send an error |
| 357 | * packet, then terminate the connection. |
| 358 | */ |
| 359 | if (!ret) { |
| 360 | char message[] = "Authentication failed at PuTTY X11 proxy"; |
| 361 | unsigned char reply[8 + sizeof(message) + 4]; |
| 362 | int msglen = sizeof(message) - 1; /* skip zero byte */ |
| 363 | int msgsize = (msglen + 3) & ~3; |
| 364 | reply[0] = 0; /* failure */ |
| 365 | reply[1] = msglen; /* length of reason string */ |
| 366 | memcpy(reply + 2, pr->firstpkt + 2, 4); /* major/minor proto vsn */ |
| 367 | PUT_16BIT(pr->firstpkt[0], reply + 6, msgsize >> 2);/* data len */ |
| 368 | memset(reply + 8, 0, msgsize); |
| 369 | memcpy(reply + 8, message, msglen); |
| 370 | sshfwd_write(pr->c, (char *)reply, 8 + msgsize); |
| 371 | sshfwd_close(pr->c); |
| 372 | x11_close(s); |
| 373 | return 0; |
| 374 | } |
| 375 | |
| 376 | /* |
| 377 | * Now we know we're going to accept the connection. Strip |
| 378 | * the fake auth data, and optionally put real auth data in |
| 379 | * instead. |
| 380 | */ |
| 381 | { |
| 382 | char realauthdata[64]; |
| 383 | int realauthlen = 0; |
| 384 | int authstrlen = strlen(x11_authnames[pr->auth->realproto]); |
| 385 | unsigned long ip; |
| 386 | int port; |
| 387 | static const char zeroes[4] = { 0,0,0,0 }; |
| 388 | |
| 389 | if (pr->auth->realproto == X11_MIT) { |
| 390 | assert(pr->auth->reallen <= lenof(realauthdata)); |
| 391 | realauthlen = pr->auth->reallen; |
| 392 | memcpy(realauthdata, pr->auth->realdata, realauthlen); |
| 393 | } else if (pr->auth->realproto == X11_XDM && |
| 394 | pr->auth->reallen == 16 && |
| 395 | sk_getxdmdata(s, &ip, &port)) { |
| 396 | time_t t; |
| 397 | realauthlen = 24; |
| 398 | memset(realauthdata, 0, 24); |
| 399 | memcpy(realauthdata, pr->auth->realdata, 8); |
| 400 | PUT_32BIT_MSB_FIRST(realauthdata+8, ip); |
| 401 | PUT_16BIT_MSB_FIRST(realauthdata+12, port); |
| 402 | t = time(NULL); |
| 403 | PUT_32BIT_MSB_FIRST(realauthdata+14, t); |
| 404 | des_encrypt_xdmauth(pr->auth->realdata+9, realauthdata, 24); |
| 405 | } |
| 406 | /* implement other auth methods here if required */ |
| 407 | |
| 408 | PUT_16BIT(pr->firstpkt[0], pr->firstpkt + 6, authstrlen); |
| 409 | PUT_16BIT(pr->firstpkt[0], pr->firstpkt + 8, realauthlen); |
| 410 | |
| 411 | sk_write(s, (char *)pr->firstpkt, 12); |
| 412 | |
| 413 | if (authstrlen) { |
| 414 | sk_write(s, x11_authnames[pr->auth->realproto], authstrlen); |
| 415 | sk_write(s, zeroes, 3 & (-authstrlen)); |
| 416 | } |
| 417 | if (realauthlen) { |
| 418 | sk_write(s, realauthdata, realauthlen); |
| 419 | sk_write(s, zeroes, 3 & (-realauthlen)); |
| 420 | } |
| 421 | } |
| 422 | pr->verified = 1; |
| 423 | } |
| 424 | |
| 425 | /* |
| 426 | * After initialisation, just copy data simply. |
| 427 | */ |
| 428 | |
| 429 | return sk_write(s, data, len); |
| 430 | } |