tftp.c revision 5d8f37ad78fc66901af50c762029a501561f3b23 
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
28struct tftp_session {
29    int in_use;
30    unsigned char filename[TFTP_FILENAME_MAX];
31
32    struct in_addr client_ip;
33    u_int16_t client_port;
34
35    int timestamp;
36};
37
38static struct tftp_session tftp_sessions[TFTP_SESSIONS_MAX];
39
40const char *tftp_prefix;
41
42static void tftp_session_update(struct tftp_session *spt)
43{
44    spt->timestamp = curtime;
45    spt->in_use = 1;
46}
47
48static void tftp_session_terminate(struct tftp_session *spt)
49{
50  spt->in_use = 0;
51}
52
53static 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  memcpy(&spt->client_ip, &tp->ip.ip_src, sizeof(spt->client_ip));
74  spt->client_port = tp->udp.uh_sport;
75
76  tftp_session_update(spt);
77
78  return k;
79}
80
81static 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 (!memcmp(&spt->client_ip, &tp->ip.ip_src, sizeof(spt->client_ip))) {
91	if (spt->client_port == tp->udp.uh_sport) {
92	  return k;
93	}
94      }
95    }
96  }
97
98  return -1;
99}
100
101static 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
131static int tftp_send_oack(struct tftp_session *spt,
132                          const char *key, uint32_t value,
133                          struct tftp_t *recv_tp)
134{
135    struct sockaddr_in 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    saddr.sin_addr = recv_tp->ip.ip_dst;
158    saddr.sin_port = recv_tp->udp.uh_dport;
159
160    daddr.sin_addr = spt->client_ip;
161    daddr.sin_port = spt->client_port;
162
163    m->m_len = sizeof(struct tftp_t) - 514 + n -
164        sizeof(struct ip) - sizeof(struct udphdr);
165    udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
166
167    return 0;
168}
169
170
171
172static int tftp_send_error(struct tftp_session *spt,
173			   u_int16_t errorcode, const char *msg,
174			   struct tftp_t *recv_tp)
175{
176  struct sockaddr_in saddr, daddr;
177  struct mbuf *m;
178  struct tftp_t *tp;
179  int nobytes;
180
181  m = m_get();
182
183  if (!m) {
184    return -1;
185  }
186
187  memset(m->m_data, 0, m->m_size);
188
189  m->m_data += IF_MAXLINKHDR;
190  tp = (void *)m->m_data;
191  m->m_data += sizeof(struct udpiphdr);
192
193  tp->tp_op = htons(TFTP_ERROR);
194  tp->x.tp_error.tp_error_code = htons(errorcode);
195  pstrcpy((char *)tp->x.tp_error.tp_msg, sizeof(tp->x.tp_error.tp_msg), msg);
196
197  saddr.sin_addr = recv_tp->ip.ip_dst;
198  saddr.sin_port = recv_tp->udp.uh_dport;
199
200  daddr.sin_addr = spt->client_ip;
201  daddr.sin_port = spt->client_port;
202
203  nobytes = 2;
204
205  m->m_len = sizeof(struct tftp_t) - 514 + 3 + strlen(msg) -
206        sizeof(struct ip) - sizeof(struct udphdr);
207
208  udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
209
210  tftp_session_terminate(spt);
211
212  return 0;
213}
214
215static int tftp_send_data(struct tftp_session *spt,
216			  u_int16_t block_nr,
217			  struct tftp_t *recv_tp)
218{
219  struct sockaddr_in saddr, daddr;
220  struct mbuf *m;
221  struct tftp_t *tp;
222  int nobytes;
223
224  if (block_nr < 1) {
225    return -1;
226  }
227
228  m = m_get();
229
230  if (!m) {
231    return -1;
232  }
233
234  memset(m->m_data, 0, m->m_size);
235
236  m->m_data += IF_MAXLINKHDR;
237  tp = (void *)m->m_data;
238  m->m_data += sizeof(struct udpiphdr);
239
240  tp->tp_op = htons(TFTP_DATA);
241  tp->x.tp_data.tp_block_nr = htons(block_nr);
242
243  saddr.sin_addr = recv_tp->ip.ip_dst;
244  saddr.sin_port = recv_tp->udp.uh_dport;
245
246  daddr.sin_addr = spt->client_ip;
247  daddr.sin_port = spt->client_port;
248
249  nobytes = tftp_read_data(spt, block_nr - 1, tp->x.tp_data.tp_buf, 512);
250
251  if (nobytes < 0) {
252    m_free(m);
253
254    /* send "file not found" error back */
255
256    tftp_send_error(spt, 1, "File not found", tp);
257
258    return -1;
259  }
260
261  m->m_len = sizeof(struct tftp_t) - (512 - nobytes) -
262        sizeof(struct ip) - sizeof(struct udphdr);
263
264  udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
265
266  if (nobytes == 512) {
267    tftp_session_update(spt);
268  }
269  else {
270    tftp_session_terminate(spt);
271  }
272
273  return 0;
274}
275
276static void tftp_handle_rrq(struct tftp_t *tp, int pktlen)
277{
278  struct tftp_session *spt;
279  int s, k, n;
280  u_int8_t *src, *dst;
281
282  s = tftp_session_allocate(tp);
283
284  if (s < 0) {
285    return;
286  }
287
288  spt = &tftp_sessions[s];
289
290  src = tp->x.tp_buf;
291  dst = spt->filename;
292  n = pktlen - ((uint8_t *)&tp->x.tp_buf[0] - (uint8_t *)tp);
293
294  /* get name */
295
296  for (k = 0; k < n; k++) {
297    if (k < TFTP_FILENAME_MAX) {
298      dst[k] = src[k];
299    }
300    else {
301      return;
302    }
303
304    if (src[k] == '\0') {
305      break;
306    }
307  }
308
309  if (k >= n) {
310    return;
311  }
312
313  k++;
314
315  /* check mode */
316  if ((n - k) < 6) {
317    return;
318  }
319
320  if (memcmp(&src[k], "octet\0", 6) != 0) {
321      tftp_send_error(spt, 4, "Unsupported transfer mode", tp);
322      return;
323  }
324
325  k += 6; /* skipping octet */
326
327  /* do sanity checks on the filename */
328
329  if ((spt->filename[0] != '/')
330      || (spt->filename[strlen((char *)spt->filename) - 1] == '/')
331      ||  strstr((char *)spt->filename, "/../")) {
332      tftp_send_error(spt, 2, "Access violation", tp);
333      return;
334  }
335
336  /* only allow exported prefixes */
337
338  if (!tftp_prefix) {
339      tftp_send_error(spt, 2, "Access violation", tp);
340      return;
341  }
342
343  /* check if the file exists */
344
345  if (tftp_read_data(spt, 0, spt->filename, 0) < 0) {
346      tftp_send_error(spt, 1, "File not found", tp);
347      return;
348  }
349
350  if (src[n - 1] != 0) {
351      tftp_send_error(spt, 2, "Access violation", tp);
352      return;
353  }
354
355  while (k < n) {
356      const char *key, *value;
357
358      key = (char *)src + k;
359      k += strlen(key) + 1;
360
361      if (k >= n) {
362	  tftp_send_error(spt, 2, "Access violation", tp);
363	  return;
364      }
365
366      value = (char *)src + k;
367      k += strlen(value) + 1;
368
369      if (strcmp(key, "tsize") == 0) {
370	  int tsize = atoi(value);
371	  struct stat stat_p;
372
373	  if (tsize == 0 && tftp_prefix) {
374	      char buffer[1024];
375	      int len;
376
377	      len = snprintf(buffer, sizeof(buffer), "%s/%s",
378			     tftp_prefix, spt->filename);
379
380	      if (stat(buffer, &stat_p) == 0)
381		  tsize = stat_p.st_size;
382	      else {
383		  tftp_send_error(spt, 1, "File not found", tp);
384		  return;
385	      }
386	  }
387
388	  tftp_send_oack(spt, "tsize", tsize, tp);
389      }
390  }
391
392  tftp_send_data(spt, 1, tp);
393}
394
395static void tftp_handle_ack(struct tftp_t *tp, int pktlen)
396{
397  int s;
398
399  s = tftp_session_find(tp);
400
401  if (s < 0) {
402    return;
403  }
404
405  if (tftp_send_data(&tftp_sessions[s],
406		     ntohs(tp->x.tp_data.tp_block_nr) + 1,
407		     tp) < 0) {
408    return;
409  }
410}
411
412void tftp_input(struct mbuf *m)
413{
414  struct tftp_t *tp = (struct tftp_t *)m->m_data;
415
416  switch(ntohs(tp->tp_op)) {
417  case TFTP_RRQ:
418    tftp_handle_rrq(tp, m->m_len);
419    break;
420
421  case TFTP_ACK:
422    tftp_handle_ack(tp, m->m_len);
423    break;
424  }
425}
426