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1 | #include <stdio.h> |
2 | #include <stdlib.h> |
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3 | #include <assert.h> |
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4 | #include <time.h> |
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5 | |
6 | #include "putty.h" |
7 | #include "ssh.h" |
8 | |
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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) ( \ |
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16 | (cp)[0] = (char)(value), \ |
17 | (cp)[1] = (char)((value) >> 8), \ |
18 | (cp)[2] = (char)((value) >> 16), \ |
19 | (cp)[3] = (char)((value) >> 24) ) |
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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) ( \ |
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26 | (cp)[0] = (char)(value), \ |
27 | (cp)[1] = (char)((value) >> 8) ) |
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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) ( \ |
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36 | (cp)[0] = (char)((value) >> 24), \ |
37 | (cp)[1] = (char)((value) >> 16), \ |
38 | (cp)[2] = (char)((value) >> 8), \ |
39 | (cp)[3] = (char)(value) ) |
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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) ( \ |
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46 | (cp)[0] = (char)((value) >> 8), \ |
47 | (cp)[1] = (char)(value) ) |
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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 | |
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55 | const char *const x11_authnames[] = { |
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56 | "", "MIT-MAGIC-COOKIE-1", "XDM-AUTHORIZATION-1" |
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57 | }; |
58 | |
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59 | struct X11Auth { |
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60 | unsigned char fakedata[64], realdata[64]; |
61 | int fakeproto, realproto; |
62 | int fakelen, reallen; |
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63 | }; |
64 | |
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65 | struct X11Private { |
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66 | const struct plug_function_table *fn; |
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67 | /* the above variable absolutely *must* be the first in this structure */ |
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68 | unsigned char firstpkt[12]; /* first X data packet */ |
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69 | struct X11Auth *auth; |
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70 | char *auth_protocol; |
71 | unsigned char *auth_data; |
72 | int data_read, auth_plen, auth_psize, auth_dlen, auth_dsize; |
73 | int verified; |
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74 | int throttled, throttle_override; |
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75 | unsigned long peer_ip; |
76 | int peer_port; |
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77 | void *c; /* data used by ssh.c */ |
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78 | Socket s; |
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79 | }; |
80 | |
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81 | void *x11_invent_auth(char *proto, int protomaxlen, |
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82 | char *data, int datamaxlen, int proto_id) |
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83 | { |
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84 | struct X11Auth *auth = smalloc(sizeof(struct X11Auth)); |
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85 | char ourdata[64]; |
86 | int i; |
87 | |
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88 | if (proto_id == X11_MIT) { |
89 | auth->fakeproto = X11_MIT; |
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90 | |
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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 | } else { |
96 | assert(proto_id == X11_XDM); |
97 | auth->fakeproto = X11_XDM; |
98 | |
99 | /* XDM-AUTHORIZATION-1. Cookie size is 16 bytes; byte 8 is zero. */ |
100 | auth->fakelen = 16; |
101 | for (i = 0; i < 16; i++) |
102 | auth->fakedata[i] = (i == 8 ? 0 : random_byte()); |
103 | } |
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104 | |
105 | /* Now format for the recipient. */ |
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106 | strncpy(proto, x11_authnames[auth->fakeproto], protomaxlen); |
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107 | ourdata[0] = '\0'; |
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108 | for (i = 0; i < auth->fakelen; i++) |
109 | sprintf(ourdata + strlen(ourdata), "%02x", auth->fakedata[i]); |
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110 | strncpy(data, ourdata, datamaxlen); |
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111 | |
112 | return auth; |
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113 | } |
114 | |
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115 | /* |
116 | * Fetch the real auth data for a given display string, and store |
117 | * it in an X11Auth structure. Returns NULL on success, or an error |
118 | * string. |
119 | */ |
120 | void x11_get_real_auth(void *authv, char *display) |
121 | { |
122 | struct X11Auth *auth = (struct X11Auth *)authv; |
123 | |
124 | auth->realproto = X11_NO_AUTH; /* in case next call does nothing */ |
125 | |
126 | auth->reallen = sizeof(auth->realdata); |
127 | platform_get_x11_auth(display, &auth->realproto, |
128 | auth->realdata, &auth->reallen); |
129 | } |
130 | |
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131 | static char *x11_verify(unsigned long peer_ip, int peer_port, |
132 | struct X11Auth *auth, char *proto, |
133 | unsigned char *data, int dlen) |
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134 | { |
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135 | if (strcmp(proto, x11_authnames[auth->fakeproto]) != 0) |
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136 | return "wrong authentication protocol attempted"; |
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137 | if (auth->fakeproto == X11_MIT) { |
138 | if (dlen != auth->fakelen) |
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139 | return "MIT-MAGIC-COOKIE-1 data was wrong length"; |
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140 | if (memcmp(auth->fakedata, data, dlen) != 0) |
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141 | return "MIT-MAGIC-COOKIE-1 data did not match"; |
142 | } |
143 | if (auth->fakeproto == X11_XDM) { |
144 | unsigned long t; |
145 | time_t tim; |
146 | int i; |
147 | |
148 | if (dlen != 24) |
149 | return "XDM-AUTHORIZATION-1 data was wrong length"; |
150 | if (peer_port == -1) |
151 | return "cannot do XDM-AUTHORIZATION-1 without remote address data"; |
152 | des_decrypt_xdmauth(auth->fakedata+9, data, 24); |
153 | if (memcmp(auth->fakedata, data, 8) != 0) |
154 | return "XDM-AUTHORIZATION-1 data failed check"; /* cookie wrong */ |
155 | if (GET_32BIT_MSB_FIRST(data+8) != peer_ip) |
156 | return "XDM-AUTHORIZATION-1 data failed check"; /* IP wrong */ |
157 | if ((int)GET_16BIT_MSB_FIRST(data+12) != peer_port) |
158 | return "XDM-AUTHORIZATION-1 data failed check"; /* port wrong */ |
159 | t = GET_32BIT_MSB_FIRST(data+14); |
160 | for (i = 18; i < 24; i++) |
161 | if (data[i] != 0) /* zero padding wrong */ |
162 | return "XDM-AUTHORIZATION-1 data failed check"; |
163 | tim = time(NULL); |
164 | if (abs(t - tim) > 20*60) /* 20 minute clock skew should be OK */ |
165 | return "XDM-AUTHORIZATION-1 time stamp was too far out"; |
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166 | } |
167 | /* implement other protocols here if ever required */ |
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168 | return NULL; |
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169 | } |
170 | |
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171 | static int x11_closing(Plug plug, char *error_msg, int error_code, |
172 | int calling_back) |
173 | { |
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174 | struct X11Private *pr = (struct X11Private *) plug; |
175 | |
176 | /* |
177 | * We have no way to communicate down the forwarded connection, |
178 | * so if an error occurred on the socket, we just ignore it |
179 | * and treat it like a proper close. |
180 | */ |
181 | sshfwd_close(pr->c); |
182 | x11_close(pr->s); |
183 | return 1; |
184 | } |
185 | |
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186 | static int x11_receive(Plug plug, int urgent, char *data, int len) |
187 | { |
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188 | struct X11Private *pr = (struct X11Private *) plug; |
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189 | |
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190 | if (sshfwd_write(pr->c, data, len) > 0) { |
191 | pr->throttled = 1; |
192 | sk_set_frozen(pr->s, 1); |
193 | } |
194 | |
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195 | return 1; |
196 | } |
197 | |
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198 | static void x11_sent(Plug plug, int bufsize) |
199 | { |
200 | struct X11Private *pr = (struct X11Private *) plug; |
201 | |
202 | sshfwd_unthrottle(pr->c, bufsize); |
203 | } |
204 | |
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205 | /* |
421d6835 |
206 | * When setting up X forwarding, we should send the screen number |
207 | * from the specified local display. This function extracts it from |
208 | * the display string. |
209 | */ |
210 | int x11_get_screen_number(char *display) |
211 | { |
212 | int n; |
213 | |
214 | n = strcspn(display, ":"); |
215 | if (!display[n]) |
216 | return 0; |
217 | n = strcspn(display, "."); |
218 | if (!display[n]) |
219 | return 0; |
220 | return atoi(display + n + 1); |
221 | } |
222 | |
223 | /* |
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224 | * Called to set up the raw connection. |
225 | * |
226 | * Returns an error message, or NULL on success. |
227 | * also, fills the SocketsStructure |
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228 | */ |
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229 | char *x11_init(Socket * s, char *display, void *c, void *auth, |
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230 | const char *peeraddr, int peerport, const Config *cfg) |
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231 | { |
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232 | static const struct plug_function_table fn_table = { |
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233 | x11_closing, |
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234 | x11_receive, |
235 | x11_sent, |
236 | NULL |
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237 | }; |
238 | |
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239 | SockAddr addr; |
240 | int port; |
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241 | char *err, *dummy_realhost; |
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242 | char host[128]; |
243 | int n, displaynum; |
244 | struct X11Private *pr; |
245 | |
246 | /* |
247 | * Split up display name into host and display-number parts. |
248 | */ |
249 | n = strcspn(display, ":"); |
250 | if (display[n]) |
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251 | displaynum = atoi(display + n + 1); |
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252 | else |
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253 | displaynum = 0; /* sensible default */ |
254 | if (n > sizeof(host) - 1) |
255 | n = sizeof(host) - 1; |
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256 | if (n > 0) { |
257 | strncpy(host, display, n); |
258 | host[n] = '\0'; |
259 | } else { |
260 | /* |
261 | * Local display numbers, particularly on Unix, often omit |
262 | * the display part completely. |
263 | */ |
264 | strcpy(host, "localhost"); |
265 | } |
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266 | |
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267 | port = 6000 + displaynum; |
268 | |
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269 | /* |
270 | * Try to find host. |
271 | */ |
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272 | addr = name_lookup(host, port, &dummy_realhost, cfg); |
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273 | if ((err = sk_addr_error(addr)) != NULL) |
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274 | return err; |
275 | |
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276 | /* |
277 | * Open socket. |
278 | */ |
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279 | pr = (struct X11Private *) smalloc(sizeof(struct X11Private)); |
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280 | pr->fn = &fn_table; |
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281 | pr->auth_protocol = NULL; |
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282 | pr->auth = (struct X11Auth *)auth; |
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283 | pr->verified = 0; |
284 | pr->data_read = 0; |
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285 | pr->throttled = pr->throttle_override = 0; |
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286 | pr->c = c; |
287 | |
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288 | pr->s = *s = new_connection(addr, dummy_realhost, port, |
289 | 0, 1, 0, (Plug) pr, cfg); |
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290 | if ((err = sk_socket_error(*s)) != NULL) { |
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291 | sfree(pr); |
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292 | return err; |
293 | } |
294 | |
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295 | /* |
296 | * See if we can make sense of the peer address we were given. |
297 | */ |
298 | { |
299 | int i[4]; |
300 | if (peeraddr && |
301 | 4 == sscanf(peeraddr, "%d.%d.%d.%d", i+0, i+1, i+2, i+3)) { |
302 | pr->peer_ip = (i[0] << 24) | (i[1] << 16) | (i[2] << 8) | i[3]; |
303 | pr->peer_port = peerport; |
304 | } else { |
305 | pr->peer_ip = 0; |
306 | pr->peer_port = -1; |
307 | } |
308 | } |
309 | |
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310 | sk_set_private_ptr(*s, pr); |
311 | sk_addr_free(addr); |
312 | return NULL; |
313 | } |
314 | |
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315 | void x11_close(Socket s) |
316 | { |
317 | struct X11Private *pr; |
d74d141c |
318 | if (!s) |
319 | return; |
320 | pr = (struct X11Private *) sk_get_private_ptr(s); |
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321 | if (pr->auth_protocol) { |
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322 | sfree(pr->auth_protocol); |
323 | sfree(pr->auth_data); |
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324 | } |
325 | |
326 | sfree(pr); |
327 | |
328 | sk_close(s); |
329 | } |
330 | |
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331 | void x11_unthrottle(Socket s) |
332 | { |
333 | struct X11Private *pr; |
334 | if (!s) |
335 | return; |
336 | pr = (struct X11Private *) sk_get_private_ptr(s); |
337 | |
338 | pr->throttled = 0; |
339 | sk_set_frozen(s, pr->throttled || pr->throttle_override); |
340 | } |
341 | |
342 | void x11_override_throttle(Socket s, int enable) |
343 | { |
344 | struct X11Private *pr; |
345 | if (!s) |
346 | return; |
347 | pr = (struct X11Private *) sk_get_private_ptr(s); |
348 | |
349 | pr->throttle_override = enable; |
350 | sk_set_frozen(s, pr->throttled || pr->throttle_override); |
351 | } |
352 | |
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353 | /* |
354 | * Called to send data down the raw connection. |
355 | */ |
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356 | int x11_send(Socket s, char *data, int len) |
32874aea |
357 | { |
358 | struct X11Private *pr = (struct X11Private *) sk_get_private_ptr(s); |
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359 | |
360 | if (s == NULL) |
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361 | return 0; |
9c964e85 |
362 | |
363 | /* |
364 | * Read the first packet. |
365 | */ |
366 | while (len > 0 && pr->data_read < 12) |
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367 | pr->firstpkt[pr->data_read++] = (unsigned char) (len--, *data++); |
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368 | if (pr->data_read < 12) |
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369 | return 0; |
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370 | |
371 | /* |
372 | * If we have not allocated the auth_protocol and auth_data |
373 | * strings, do so now. |
374 | */ |
375 | if (!pr->auth_protocol) { |
32874aea |
376 | pr->auth_plen = GET_16BIT(pr->firstpkt[0], pr->firstpkt + 6); |
377 | pr->auth_dlen = GET_16BIT(pr->firstpkt[0], pr->firstpkt + 8); |
378 | pr->auth_psize = (pr->auth_plen + 3) & ~3; |
379 | pr->auth_dsize = (pr->auth_dlen + 3) & ~3; |
380 | /* Leave room for a terminating zero, to make our lives easier. */ |
381 | pr->auth_protocol = (char *) smalloc(pr->auth_psize + 1); |
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382 | pr->auth_data = (unsigned char *) smalloc(pr->auth_dsize); |
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383 | } |
384 | |
385 | /* |
386 | * Read the auth_protocol and auth_data strings. |
387 | */ |
388 | while (len > 0 && pr->data_read < 12 + pr->auth_psize) |
32874aea |
389 | pr->auth_protocol[pr->data_read++ - 12] = (len--, *data++); |
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390 | while (len > 0 && pr->data_read < 12 + pr->auth_psize + pr->auth_dsize) |
32874aea |
391 | pr->auth_data[pr->data_read++ - 12 - |
392 | pr->auth_psize] = (unsigned char) (len--, *data++); |
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393 | if (pr->data_read < 12 + pr->auth_psize + pr->auth_dsize) |
5471d09a |
394 | return 0; |
9c964e85 |
395 | |
396 | /* |
397 | * If we haven't verified the authentication, do so now. |
398 | */ |
399 | if (!pr->verified) { |
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400 | char *err; |
32874aea |
401 | |
402 | pr->auth_protocol[pr->auth_plen] = '\0'; /* ASCIZ */ |
b3ebaa28 |
403 | err = x11_verify(pr->peer_ip, pr->peer_port, |
404 | pr->auth, pr->auth_protocol, |
302121de |
405 | pr->auth_data, pr->auth_dlen); |
32874aea |
406 | |
407 | /* |
408 | * If authentication failed, construct and send an error |
409 | * packet, then terminate the connection. |
410 | */ |
b3ebaa28 |
411 | if (err) { |
412 | char *message; |
413 | int msglen, msgsize; |
414 | unsigned char *reply; |
415 | |
416 | message = dupprintf("PuTTY X11 proxy: %s", err); |
417 | msglen = strlen(message); |
418 | reply = smalloc(8 + msglen+1 + 4); /* include zero byte */ |
419 | msgsize = (msglen + 3) & ~3; |
32874aea |
420 | reply[0] = 0; /* failure */ |
421 | reply[1] = msglen; /* length of reason string */ |
422 | memcpy(reply + 2, pr->firstpkt + 2, 4); /* major/minor proto vsn */ |
75105663 |
423 | PUT_16BIT(pr->firstpkt[0], reply + 6, msgsize >> 2);/* data len */ |
32874aea |
424 | memset(reply + 8, 0, msgsize); |
425 | memcpy(reply + 8, message, msglen); |
f28e6b7c |
426 | sshfwd_write(pr->c, (char *)reply, 8 + msgsize); |
32874aea |
427 | sshfwd_close(pr->c); |
428 | x11_close(s); |
b3ebaa28 |
429 | sfree(reply); |
430 | sfree(message); |
5471d09a |
431 | return 0; |
32874aea |
432 | } |
433 | |
434 | /* |
435 | * Now we know we're going to accept the connection. Strip |
e0e7dff8 |
436 | * the fake auth data, and optionally put real auth data in |
437 | * instead. |
32874aea |
438 | */ |
e0e7dff8 |
439 | { |
440 | char realauthdata[64]; |
441 | int realauthlen = 0; |
442 | int authstrlen = strlen(x11_authnames[pr->auth->realproto]); |
2f92b717 |
443 | unsigned long ip; |
444 | int port; |
e0e7dff8 |
445 | static const char zeroes[4] = { 0,0,0,0 }; |
446 | |
447 | if (pr->auth->realproto == X11_MIT) { |
448 | assert(pr->auth->reallen <= lenof(realauthdata)); |
449 | realauthlen = pr->auth->reallen; |
450 | memcpy(realauthdata, pr->auth->realdata, realauthlen); |
2f92b717 |
451 | } else if (pr->auth->realproto == X11_XDM && |
452 | pr->auth->reallen == 16 && |
453 | sk_getxdmdata(s, &ip, &port)) { |
454 | time_t t; |
455 | realauthlen = 24; |
456 | memset(realauthdata, 0, 24); |
457 | memcpy(realauthdata, pr->auth->realdata, 8); |
458 | PUT_32BIT_MSB_FIRST(realauthdata+8, ip); |
459 | PUT_16BIT_MSB_FIRST(realauthdata+12, port); |
460 | t = time(NULL); |
461 | PUT_32BIT_MSB_FIRST(realauthdata+14, t); |
6e7f5aee |
462 | des_encrypt_xdmauth(pr->auth->realdata+9, |
463 | (unsigned char *)realauthdata, 24); |
2f92b717 |
464 | } |
e0e7dff8 |
465 | /* implement other auth methods here if required */ |
466 | |
467 | PUT_16BIT(pr->firstpkt[0], pr->firstpkt + 6, authstrlen); |
468 | PUT_16BIT(pr->firstpkt[0], pr->firstpkt + 8, realauthlen); |
469 | |
470 | sk_write(s, (char *)pr->firstpkt, 12); |
471 | |
472 | if (authstrlen) { |
473 | sk_write(s, x11_authnames[pr->auth->realproto], authstrlen); |
474 | sk_write(s, zeroes, 3 & (-authstrlen)); |
475 | } |
476 | if (realauthlen) { |
477 | sk_write(s, realauthdata, realauthlen); |
478 | sk_write(s, zeroes, 3 & (-realauthlen)); |
479 | } |
480 | } |
32874aea |
481 | pr->verified = 1; |
9c964e85 |
482 | } |
483 | |
484 | /* |
485 | * After initialisation, just copy data simply. |
486 | */ |
487 | |
5471d09a |
488 | return sk_write(s, data, len); |
9c964e85 |
489 | } |