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 "qemu-common.h" // for pstrcpy
27
28 struct tftp_session {
29 int in_use;
30 unsigned char filename[TFTP_FILENAME_MAX];
31
32 uint32_t client_ip;
33 uint16_t client_port;
34
35 int timestamp;
36 };
37
38 static struct tftp_session tftp_sessions[TFTP_SESSIONS_MAX];
39
40 const char *tftp_prefix;
41
tftp_session_update(struct tftp_session * spt)42 static void tftp_session_update(struct tftp_session *spt)
43 {
44 spt->timestamp = curtime;
45 spt->in_use = 1;
46 }
47
tftp_session_terminate(struct tftp_session * spt)48 static void tftp_session_terminate(struct tftp_session *spt)
49 {
50 spt->in_use = 0;
51 }
52
tftp_session_allocate(struct tftp_t * tp)53 static int tftp_session_allocate(struct tftp_t *tp)
54 {
55 struct tftp_session *spt;
56 int k;
57
58 for (k = 0; k < TFTP_SESSIONS_MAX; k++) {
59 spt = &tftp_sessions[k];
60
61 if (!spt->in_use)
62 goto found;
63
64 /* sessions time out after 5 inactive seconds */
65 if ((int)(curtime - spt->timestamp) > 5000)
66 goto found;
67 }
68
69 return -1;
70
71 found:
72 memset(spt, 0, sizeof(*spt));
73 spt->client_ip = ip_geth(tp->ip.ip_src);
74 spt->client_port = port_geth(tp->udp.uh_sport);
75
76 tftp_session_update(spt);
77
78 return k;
79 }
80
tftp_session_find(struct tftp_t * tp)81 static int tftp_session_find(struct tftp_t *tp)
82 {
83 struct tftp_session *spt;
84 int k;
85
86 for (k = 0; k < TFTP_SESSIONS_MAX; k++) {
87 spt = &tftp_sessions[k];
88
89 if (spt->in_use) {
90 if (spt->client_ip == ip_geth(tp->ip.ip_src)) {
91 if (spt->client_port == port_geth(tp->udp.uh_sport)) {
92 return k;
93 }
94 }
95 }
96 }
97
98 return -1;
99 }
100
tftp_read_data(struct tftp_session * spt,u_int16_t block_nr,u_int8_t * buf,int len)101 static int tftp_read_data(struct tftp_session *spt, u_int16_t block_nr,
102 u_int8_t *buf, int len)
103 {
104 int fd;
105 int bytes_read = 0;
106 char buffer[1024];
107 int n;
108
109 n = snprintf(buffer, sizeof(buffer), "%s/%s",
110 tftp_prefix, spt->filename);
111 if (n >= sizeof(buffer))
112 return -1;
113
114 fd = open(buffer, O_RDONLY | O_BINARY);
115
116 if (fd < 0) {
117 return -1;
118 }
119
120 if (len) {
121 lseek(fd, block_nr * 512, SEEK_SET);
122
123 bytes_read = read(fd, buf, len);
124 }
125
126 close(fd);
127
128 return bytes_read;
129 }
130
tftp_send_oack(struct tftp_session * spt,const char * key,uint32_t value,struct tftp_t * recv_tp)131 static int tftp_send_oack(struct tftp_session *spt,
132 const char *key, uint32_t value,
133 struct tftp_t *recv_tp)
134 {
135 SockAddress saddr, daddr;
136 struct mbuf *m;
137 struct tftp_t *tp;
138 int n = 0;
139
140 m = m_get();
141
142 if (!m)
143 return -1;
144
145 memset(m->m_data, 0, m->m_size);
146
147 m->m_data += IF_MAXLINKHDR;
148 tp = (void *)m->m_data;
149 m->m_data += sizeof(struct udpiphdr);
150
151 tp->tp_op = htons(TFTP_OACK);
152 n += snprintf((char *)tp->x.tp_buf + n, sizeof(tp->x.tp_buf) - n, "%s",
153 key) + 1;
154 n += snprintf((char *)tp->x.tp_buf + n, sizeof(tp->x.tp_buf) - n, "%u",
155 value) + 1;
156
157 sock_address_init_inet( &saddr,
158 ip_geth(recv_tp->ip.ip_dst),
159 port_geth(recv_tp->udp.uh_dport) );
160
161 sock_address_init_inet( &daddr,
162 spt->client_ip,
163 spt->client_port );
164
165 m->m_len = sizeof(struct tftp_t) - 514 + n -
166 sizeof(struct ip) - sizeof(struct udphdr);
167 udp_output2_(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
168
169 return 0;
170 }
171
172
173
tftp_send_error(struct tftp_session * spt,u_int16_t errorcode,const char * msg,struct tftp_t * recv_tp)174 static int tftp_send_error(struct tftp_session *spt,
175 u_int16_t errorcode, const char *msg,
176 struct tftp_t *recv_tp)
177 {
178 SockAddress saddr, daddr;
179 struct mbuf *m;
180 struct tftp_t *tp;
181 int nobytes;
182
183 m = m_get();
184
185 if (!m) {
186 return -1;
187 }
188
189 memset(m->m_data, 0, m->m_size);
190
191 m->m_data += IF_MAXLINKHDR;
192 tp = (void *)m->m_data;
193 m->m_data += sizeof(struct udpiphdr);
194
195 tp->tp_op = htons(TFTP_ERROR);
196 tp->x.tp_error.tp_error_code = htons(errorcode);
197 pstrcpy((char *)tp->x.tp_error.tp_msg, sizeof(tp->x.tp_error.tp_msg), msg);
198
199 sock_address_init_inet( &saddr,
200 ip_geth(recv_tp->ip.ip_dst),
201 port_geth(recv_tp->udp.uh_dport) );
202
203 sock_address_init_inet( &daddr,
204 spt->client_ip,
205 spt->client_port );
206
207 nobytes = 2;
208
209 m->m_len = sizeof(struct tftp_t) - 514 + 3 + strlen(msg) -
210 sizeof(struct ip) - sizeof(struct udphdr);
211
212 udp_output2_(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
213
214 tftp_session_terminate(spt);
215
216 return 0;
217 }
218
tftp_send_data(struct tftp_session * spt,u_int16_t block_nr,struct tftp_t * recv_tp)219 static int tftp_send_data(struct tftp_session *spt,
220 u_int16_t block_nr,
221 struct tftp_t *recv_tp)
222 {
223 SockAddress saddr, daddr;
224 struct mbuf *m;
225 struct tftp_t *tp;
226 int nobytes;
227
228 if (block_nr < 1) {
229 return -1;
230 }
231
232 m = m_get();
233
234 if (!m) {
235 return -1;
236 }
237
238 memset(m->m_data, 0, m->m_size);
239
240 m->m_data += IF_MAXLINKHDR;
241 tp = (void *)m->m_data;
242 m->m_data += sizeof(struct udpiphdr);
243
244 tp->tp_op = htons(TFTP_DATA);
245 tp->x.tp_data.tp_block_nr = htons(block_nr);
246
247 sock_address_init_inet( &saddr,
248 ip_geth(recv_tp->ip.ip_dst),
249 port_geth(recv_tp->udp.uh_dport) );
250
251 sock_address_init_inet( &daddr,
252 spt->client_ip,
253 spt->client_port );
254
255 nobytes = tftp_read_data(spt, block_nr - 1, tp->x.tp_data.tp_buf, 512);
256
257 if (nobytes < 0) {
258 m_free(m);
259
260 /* send "file not found" error back */
261
262 tftp_send_error(spt, 1, "File not found", tp);
263
264 return -1;
265 }
266
267 m->m_len = sizeof(struct tftp_t) - (512 - nobytes) -
268 sizeof(struct ip) - sizeof(struct udphdr);
269
270 udp_output2_(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
271
272 if (nobytes == 512) {
273 tftp_session_update(spt);
274 }
275 else {
276 tftp_session_terminate(spt);
277 }
278
279 return 0;
280 }
281
tftp_handle_rrq(struct tftp_t * tp,int pktlen)282 static void tftp_handle_rrq(struct tftp_t *tp, int pktlen)
283 {
284 struct tftp_session *spt;
285 int s, k, n;
286 u_int8_t *src, *dst;
287
288 s = tftp_session_allocate(tp);
289
290 if (s < 0) {
291 return;
292 }
293
294 spt = &tftp_sessions[s];
295
296 src = tp->x.tp_buf;
297 dst = spt->filename;
298 n = pktlen - ((uint8_t *)&tp->x.tp_buf[0] - (uint8_t *)tp);
299
300 /* get name */
301
302 for (k = 0; k < n; k++) {
303 if (k < TFTP_FILENAME_MAX) {
304 dst[k] = src[k];
305 }
306 else {
307 return;
308 }
309
310 if (src[k] == '\0') {
311 break;
312 }
313 }
314
315 if (k >= n) {
316 return;
317 }
318
319 k++;
320
321 /* check mode */
322 if ((n - k) < 6) {
323 return;
324 }
325
326 if (memcmp(&src[k], "octet\0", 6) != 0) {
327 tftp_send_error(spt, 4, "Unsupported transfer mode", tp);
328 return;
329 }
330
331 k += 6; /* skipping octet */
332
333 /* do sanity checks on the filename */
334
335 if ((spt->filename[0] != '/')
336 || (spt->filename[strlen((char *)spt->filename) - 1] == '/')
337 || strstr((char *)spt->filename, "/../")) {
338 tftp_send_error(spt, 2, "Access violation", tp);
339 return;
340 }
341
342 /* only allow exported prefixes */
343
344 if (!tftp_prefix) {
345 tftp_send_error(spt, 2, "Access violation", tp);
346 return;
347 }
348
349 /* check if the file exists */
350
351 if (tftp_read_data(spt, 0, spt->filename, 0) < 0) {
352 tftp_send_error(spt, 1, "File not found", tp);
353 return;
354 }
355
356 if (src[n - 1] != 0) {
357 tftp_send_error(spt, 2, "Access violation", tp);
358 return;
359 }
360
361 while (k < n) {
362 const char *key, *value;
363
364 key = (char *)src + k;
365 k += strlen(key) + 1;
366
367 if (k >= n) {
368 tftp_send_error(spt, 2, "Access violation", tp);
369 return;
370 }
371
372 value = (char *)src + k;
373 k += strlen(value) + 1;
374
375 if (strcmp(key, "tsize") == 0) {
376 int tsize = atoi(value);
377 struct stat stat_p;
378
379 if (tsize == 0 && tftp_prefix) {
380 char buffer[1024];
381 int len;
382
383 len = snprintf(buffer, sizeof(buffer), "%s/%s",
384 tftp_prefix, spt->filename);
385
386 if (stat(buffer, &stat_p) == 0)
387 tsize = stat_p.st_size;
388 else {
389 tftp_send_error(spt, 1, "File not found", tp);
390 return;
391 }
392 }
393
394 tftp_send_oack(spt, "tsize", tsize, tp);
395 }
396 }
397
398 tftp_send_data(spt, 1, tp);
399 }
400
tftp_handle_ack(struct tftp_t * tp,int pktlen)401 static void tftp_handle_ack(struct tftp_t *tp, int pktlen)
402 {
403 int s;
404
405 s = tftp_session_find(tp);
406
407 if (s < 0) {
408 return;
409 }
410
411 if (tftp_send_data(&tftp_sessions[s],
412 ntohs(tp->x.tp_data.tp_block_nr) + 1,
413 tp) < 0) {
414 return;
415 }
416 }
417
tftp_input(struct mbuf * m)418 void tftp_input(struct mbuf *m)
419 {
420 struct tftp_t *tp = (struct tftp_t *)m->m_data;
421
422 switch(ntohs(tp->tp_op)) {
423 case TFTP_RRQ:
424 tftp_handle_rrq(tp, m->m_len);
425 break;
426
427 case TFTP_ACK:
428 tftp_handle_ack(tp, m->m_len);
429 break;
430 }
431 }
432