1 /*
2 * tftp.c - a simple, read-only tftp server for qemu
3 *
4 * Copyright (c) 2004 Magnus Damm <damm@opensource.se>
5 *
6 * Permission is hereby granted, free of charge, to any person obtaining a copy
7 * of this software and associated documentation files (the "Software"), to deal
8 * in the Software without restriction, including without limitation the rights
9 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
10 * copies of the Software, and to permit persons to whom the Software is
11 * furnished to do so, subject to the following conditions:
12 *
13 * The above copyright notice and this permission notice shall be included in
14 * all copies or substantial portions of the Software.
15 *
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
19 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
21 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
22 * THE SOFTWARE.
23 */
24
25 #include <slirp.h>
26 #include <fcntl.h>
27 #include <sys/stat.h>
28
29 struct tftp_session {
30 int in_use;
31 unsigned char filename[TFTP_FILENAME_MAX];
32
33 uint32_t client_ip;
34 uint16_t client_port;
35
36 int timestamp;
37 };
38
39 struct tftp_session tftp_sessions[TFTP_SESSIONS_MAX];
40
41 const char *tftp_prefix;
42
tftp_session_update(struct tftp_session * spt)43 static void tftp_session_update(struct tftp_session *spt)
44 {
45 spt->timestamp = curtime;
46 spt->in_use = 1;
47 }
48
tftp_session_terminate(struct tftp_session * spt)49 static void tftp_session_terminate(struct tftp_session *spt)
50 {
51 spt->in_use = 0;
52 }
53
tftp_session_allocate(struct tftp_t * tp)54 static int tftp_session_allocate(struct tftp_t *tp)
55 {
56 struct tftp_session *spt;
57 int k;
58
59 for (k = 0; k < TFTP_SESSIONS_MAX; k++) {
60 spt = &tftp_sessions[k];
61
62 if (!spt->in_use)
63 goto found;
64
65 /* sessions time out after 5 inactive seconds */
66 if ((int)(curtime - spt->timestamp) > 5000)
67 goto found;
68 }
69
70 return -1;
71
72 found:
73 memset(spt, 0, sizeof(*spt));
74 spt->client_ip = ip_geth(tp->ip.ip_src);
75 spt->client_port = port_geth(tp->udp.uh_sport);
76
77 tftp_session_update(spt);
78
79 return k;
80 }
81
tftp_session_find(struct tftp_t * tp)82 static int tftp_session_find(struct tftp_t *tp)
83 {
84 struct tftp_session *spt;
85 int k;
86
87 for (k = 0; k < TFTP_SESSIONS_MAX; k++) {
88 spt = &tftp_sessions[k];
89
90 if (spt->in_use) {
91 if (spt->client_ip == ip_geth(tp->ip.ip_src)) {
92 if (spt->client_port == port_geth(tp->udp.uh_sport)) {
93 return k;
94 }
95 }
96 }
97 }
98
99 return -1;
100 }
101
tftp_read_data(struct tftp_session * spt,u_int16_t block_nr,u_int8_t * buf,int len)102 static int tftp_read_data(struct tftp_session *spt, u_int16_t block_nr,
103 u_int8_t *buf, int len)
104 {
105 int fd;
106 int bytes_read = 0;
107 char buffer[1024];
108 int n;
109
110 n = snprintf(buffer, sizeof(buffer), "%s/%s",
111 tftp_prefix, spt->filename);
112 if (n >= sizeof(buffer))
113 return -1;
114
115 fd = open(buffer, O_RDONLY | O_BINARY);
116
117 if (fd < 0) {
118 return -1;
119 }
120
121 if (len) {
122 lseek(fd, block_nr * 512, SEEK_SET);
123
124 bytes_read = read(fd, buf, len);
125 }
126
127 close(fd);
128
129 return bytes_read;
130 }
131
tftp_send_oack(struct tftp_session * spt,const char * key,uint32_t value,struct tftp_t * recv_tp)132 static int tftp_send_oack(struct tftp_session *spt,
133 const char *key, uint32_t value,
134 struct tftp_t *recv_tp)
135 {
136 SockAddress saddr, daddr;
137 MBuf m;
138 struct tftp_t *tp;
139 int n = 0;
140
141 m = mbuf_alloc();
142
143 if (!m)
144 return -1;
145
146 memset(m->m_data, 0, m->m_size);
147
148 m->m_data += if_maxlinkhdr;
149 tp = (void *)m->m_data;
150 m->m_data += sizeof(struct udpiphdr);
151
152 tp->tp_op = htons(TFTP_OACK);
153 n += sprintf((char*)tp->x.tp_buf + n, "%s", key) + 1;
154 n += sprintf((char*)tp->x.tp_buf + n, "%u", value) + 1;
155
156 sock_address_init_inet( &saddr,
157 ip_geth(recv_tp->ip.ip_dst),
158 port_geth(recv_tp->udp.uh_dport) );
159
160 sock_address_init_inet( &daddr,
161 spt->client_ip,
162 spt->client_port );
163
164 m->m_len = sizeof(struct tftp_t) - 514 + n -
165 sizeof(struct ip) - sizeof(struct udphdr);
166 udp_output2_(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
167
168 return 0;
169 }
170
171
172
tftp_send_error(struct tftp_session * spt,u_int16_t errorcode,const char * msg,struct tftp_t * recv_tp)173 static int tftp_send_error(struct tftp_session *spt,
174 u_int16_t errorcode, const char *msg,
175 struct tftp_t *recv_tp)
176 {
177 SockAddress saddr, daddr;
178 MBuf m;
179 struct tftp_t *tp;
180 int nobytes;
181
182 m = mbuf_alloc();
183
184 if (!m) {
185 return -1;
186 }
187
188 memset(m->m_data, 0, m->m_size);
189
190 m->m_data += if_maxlinkhdr;
191 tp = (void *)m->m_data;
192 m->m_data += sizeof(struct udpiphdr);
193
194 tp->tp_op = htons(TFTP_ERROR);
195 tp->x.tp_error.tp_error_code = htons(errorcode);
196 strcpy((char*)tp->x.tp_error.tp_msg, msg);
197
198 sock_address_init_inet( &saddr,
199 ip_geth(recv_tp->ip.ip_dst),
200 port_geth(recv_tp->udp.uh_dport) );
201
202 sock_address_init_inet( &daddr,
203 spt->client_ip,
204 spt->client_port );
205
206 nobytes = 2;
207
208 m->m_len = sizeof(struct tftp_t) - 514 + 3 + strlen(msg) -
209 sizeof(struct ip) - sizeof(struct udphdr);
210
211 udp_output2_(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
212
213 tftp_session_terminate(spt);
214
215 return 0;
216 }
217
tftp_send_data(struct tftp_session * spt,u_int16_t block_nr,struct tftp_t * recv_tp)218 static int tftp_send_data(struct tftp_session *spt,
219 u_int16_t block_nr,
220 struct tftp_t *recv_tp)
221 {
222 SockAddress saddr, daddr;
223 MBuf m;
224 struct tftp_t *tp;
225 int nobytes;
226
227 if (block_nr < 1) {
228 return -1;
229 }
230
231 m = mbuf_alloc();
232
233 if (!m) {
234 return -1;
235 }
236
237 memset(m->m_data, 0, m->m_size);
238
239 m->m_data += if_maxlinkhdr;
240 tp = (void *)m->m_data;
241 m->m_data += sizeof(struct udpiphdr);
242
243 tp->tp_op = htons(TFTP_DATA);
244 tp->x.tp_data.tp_block_nr = htons(block_nr);
245
246 sock_address_init_inet( &saddr,
247 ip_geth(recv_tp->ip.ip_dst),
248 port_geth(recv_tp->udp.uh_dport) );
249
250 sock_address_init_inet( &daddr,
251 spt->client_ip,
252 spt->client_port );
253
254 nobytes = tftp_read_data(spt, block_nr - 1, tp->x.tp_data.tp_buf, 512);
255
256 if (nobytes < 0) {
257 mbuf_free(m);
258
259 /* send "file not found" error back */
260
261 tftp_send_error(spt, 1, "File not found", tp);
262
263 return -1;
264 }
265
266 m->m_len = sizeof(struct tftp_t) - (512 - nobytes) -
267 sizeof(struct ip) - sizeof(struct udphdr);
268
269 udp_output2_(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
270
271 if (nobytes == 512) {
272 tftp_session_update(spt);
273 }
274 else {
275 tftp_session_terminate(spt);
276 }
277
278 return 0;
279 }
280
tftp_handle_rrq(struct tftp_t * tp,int pktlen)281 static void tftp_handle_rrq(struct tftp_t *tp, int pktlen)
282 {
283 struct tftp_session *spt;
284 int s, k, n;
285 u_int8_t *src, *dst;
286
287 s = tftp_session_allocate(tp);
288
289 if (s < 0) {
290 return;
291 }
292
293 spt = &tftp_sessions[s];
294
295 src = tp->x.tp_buf;
296 dst = spt->filename;
297 n = pktlen - ((uint8_t *)&tp->x.tp_buf[0] - (uint8_t *)tp);
298
299 /* get name */
300
301 for (k = 0; k < n; k++) {
302 if (k < TFTP_FILENAME_MAX) {
303 dst[k] = src[k];
304 }
305 else {
306 return;
307 }
308
309 if (src[k] == '\0') {
310 break;
311 }
312 }
313
314 if (k >= n) {
315 return;
316 }
317
318 k++;
319
320 /* check mode */
321 if ((n - k) < 6) {
322 return;
323 }
324
325 if (memcmp(&src[k], "octet\0", 6) != 0) {
326 tftp_send_error(spt, 4, "Unsupported transfer mode", tp);
327 return;
328 }
329
330 k += 6; /* skipping octet */
331
332 /* do sanity checks on the filename */
333
334 if ((spt->filename[0] != '/')
335 || (spt->filename[strlen((const char*)spt->filename) - 1] == '/')
336 || strstr((const char*)spt->filename, "/../")) {
337 tftp_send_error(spt, 2, "Access violation", tp);
338 return;
339 }
340
341 /* only allow exported prefixes */
342
343 if (!tftp_prefix) {
344 tftp_send_error(spt, 2, "Access violation", tp);
345 return;
346 }
347
348 /* check if the file exists */
349
350 if (tftp_read_data(spt, 0, spt->filename, 0) < 0) {
351 tftp_send_error(spt, 1, "File not found", tp);
352 return;
353 }
354
355 if (src[n - 1] != 0) {
356 tftp_send_error(spt, 2, "Access violation", tp);
357 return;
358 }
359
360 while (k < n) {
361 const char *key, *value;
362
363 key = (const char*)src + k;
364 k += strlen(key) + 1;
365
366 if (k >= n) {
367 tftp_send_error(spt, 2, "Access violation", tp);
368 return;
369 }
370
371 value = (const char*)src + k;
372 k += strlen(value) + 1;
373
374 if (strcmp(key, "tsize") == 0) {
375 int tsize = atoi(value);
376 struct stat stat_p;
377
378 if (tsize == 0 && tftp_prefix) {
379 char buffer[1024];
380 int len;
381
382 len = snprintf(buffer, sizeof(buffer), "%s/%s",
383 tftp_prefix, spt->filename);
384
385 if (stat(buffer, &stat_p) == 0)
386 tsize = stat_p.st_size;
387 else {
388 tftp_send_error(spt, 1, "File not found", tp);
389 return;
390 }
391 }
392
393 tftp_send_oack(spt, "tsize", tsize, tp);
394 }
395 }
396
397 tftp_send_data(spt, 1, tp);
398 }
399
tftp_handle_ack(struct tftp_t * tp,int pktlen)400 static void tftp_handle_ack(struct tftp_t *tp, int pktlen)
401 {
402 int s;
403
404 s = tftp_session_find(tp);
405
406 if (s < 0) {
407 return;
408 }
409
410 if (tftp_send_data(&tftp_sessions[s],
411 ntohs(tp->x.tp_data.tp_block_nr) + 1,
412 tp) < 0) {
413 return;
414 }
415 }
416
tftp_input(MBuf m)417 void tftp_input(MBuf m)
418 {
419 struct tftp_t *tp = (struct tftp_t *)m->m_data;
420
421 switch(ntohs(tp->tp_op)) {
422 case TFTP_RRQ:
423 tftp_handle_rrq(tp, m->m_len);
424 break;
425
426 case TFTP_ACK:
427 tftp_handle_ack(tp, m->m_len);
428 break;
429 }
430 }
431