src/slirp/tftp.c

/*
 * tftp.c - a simple, read-only tftp server for qemu
 * 
 * Copyright (c) 2004 Magnus Damm <damm@opensource.se>
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include <slirp.h>

struct tftp_session {
    int in_use;
    char filename[TFTP_FILENAME_MAX];
    
    struct in_addr client_ip;
    u_int16_t client_port;
    
    int timestamp;
};

struct tftp_session tftp_sessions[TFTP_SESSIONS_MAX];

const char *tftp_prefix;

static void tftp_session_update(struct tftp_session *spt)
{
    spt->timestamp = curtime;
    spt->in_use = 1;
}

static void tftp_session_terminate(struct tftp_session *spt)
{
  spt->in_use = 0;
}

static int tftp_session_allocate(struct tftp_t *tp)
{
  struct tftp_session *spt;
  int k;

  for (k = 0; k < TFTP_SESSIONS_MAX; k++) {
    spt = &tftp_sessions[k];

    if (!spt->in_use)
        goto found;

    /* sessions time out after 5 inactive seconds */
    if ((int)(curtime - spt->timestamp) > 5000)
        goto found;
  }

  return -1;

 found:
  memset(spt, 0, sizeof(*spt));
  memcpy(&spt->client_ip, &tp->ip.ip_src, sizeof(spt->client_ip));
  spt->client_port = tp->udp.uh_sport;

  tftp_session_update(spt);

  return k;
}

static int tftp_session_find(struct tftp_t *tp)
{
  struct tftp_session *spt;
  int k;

  for (k = 0; k < TFTP_SESSIONS_MAX; k++) {
    spt = &tftp_sessions[k];

    if (spt->in_use) {
      if (!memcmp(&spt->client_ip, &tp->ip.ip_src, sizeof(spt->client_ip))) {
        if (spt->client_port == tp->udp.uh_sport) {
          return k;
        }
      }
    }
  }

  return -1;
}

static int tftp_read_data(struct tftp_session *spt, u_int16_t block_nr,
                          u_int8_t *buf, int len)
{
  int fd;
  int bytes_read = 0;

  fd = open(spt->filename, O_RDONLY | O_BINARY);

  if (fd < 0) {
    return -1;
  }

  if (len) {
    lseek(fd, block_nr * 512, SEEK_SET);

    bytes_read = read(fd, buf, len);
  }

  close(fd);

  return bytes_read;
}

static int tftp_send_error(struct tftp_session *spt, 
                           u_int16_t errorcode, const char *msg,
                           struct tftp_t *recv_tp)
{
  struct sockaddr_in saddr, daddr;
  struct mbuf *m;
  struct tftp_t *tp;
  int nobytes;

  m = m_get();

  if (!m) {
    return -1;
  }

  memset(m->m_data, 0, m->m_size);

  m->m_data += if_maxlinkhdr;
  tp = (void *)m->m_data;
  m->m_data += sizeof(struct udpiphdr);
  
  tp->tp_op = htons(TFTP_ERROR);
  tp->x.tp_error.tp_error_code = htons(errorcode);
  strncpy((char *)tp->x.tp_error.tp_msg, msg, sizeof(tp->x.tp_error.tp_msg));
  tp->x.tp_error.tp_msg[sizeof(tp->x.tp_error.tp_msg)-1] = 0;

  saddr.sin_addr = recv_tp->ip.ip_dst;
  saddr.sin_port = recv_tp->udp.uh_dport;

  daddr.sin_addr = spt->client_ip;
  daddr.sin_port = spt->client_port;

  nobytes = 2;

  m->m_len = sizeof(struct tftp_t) - 514 + 3 + strlen(msg) - 
        sizeof(struct ip) - sizeof(struct udphdr);

  udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);

  tftp_session_terminate(spt);

  return 0;
}

static int tftp_send_data(struct tftp_session *spt, 
                          u_int16_t block_nr,
                          struct tftp_t *recv_tp)
{
  struct sockaddr_in saddr, daddr;
  struct mbuf *m;
  struct tftp_t *tp;
  int nobytes;

  if (block_nr < 1) {
    return -1;
  }

  m = m_get();

  if (!m) {
    return -1;
  }

  memset(m->m_data, 0, m->m_size);

  m->m_data += if_maxlinkhdr;
  tp = (void *)m->m_data;
  m->m_data += sizeof(struct udpiphdr);
  
  tp->tp_op = htons(TFTP_DATA);
  tp->x.tp_data.tp_block_nr = htons(block_nr);

  saddr.sin_addr = recv_tp->ip.ip_dst;
  saddr.sin_port = recv_tp->udp.uh_dport;

  daddr.sin_addr = spt->client_ip;
  daddr.sin_port = spt->client_port;

  nobytes = tftp_read_data(spt, block_nr - 1, tp->x.tp_data.tp_buf, 512);

  if (nobytes < 0) {
    m_free(m);

    /* send "file not found" error back */

    tftp_send_error(spt, 1, "File not found", tp);

    return -1;
  }

  m->m_len = sizeof(struct tftp_t) - (512 - nobytes) - 
        sizeof(struct ip) - sizeof(struct udphdr);

  udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);

  if (nobytes == 512) {
    tftp_session_update(spt);
  }
  else {
    tftp_session_terminate(spt);
  }

  return 0;
}

static void tftp_handle_rrq(struct tftp_t *tp, int pktlen)
{
  struct tftp_session *spt;
  int s, k, n;
  u_int8_t *src, *dst;

  s = tftp_session_allocate(tp);

  if (s < 0) {
    return;
  }

  spt = &tftp_sessions[s];

  src = tp->x.tp_buf;
  dst = (u_int8_t *)spt->filename;
  n = pktlen - ((uint8_t *)&tp->x.tp_buf[0] - (uint8_t *)tp);

  /* get name */

  for (k = 0; k < n; k++) {
    if (k < TFTP_FILENAME_MAX) {
      dst[k] = src[k];
    }
    else {
      return;
    }
    
    if (src[k] == '\0') {
      break;
    }
  }
      
  if (k >= n) {
    return;
  }
  
  k++;
  
  /* check mode */
  if ((n - k) < 6) {
    return;
  }
  
  if (memcmp(&src[k], "octet\0", 6) != 0) {
      tftp_send_error(spt, 4, "Unsupported transfer mode", tp);
      return;
  }

  /* do sanity checks on the filename */

  if ((spt->filename[0] != '/')
      || (spt->filename[strlen(spt->filename) - 1] == '/')
      ||  strstr(spt->filename, "/../")) {
      tftp_send_error(spt, 2, "Access violation", tp);
      return;
  }

  /* only allow exported prefixes */

  if (!tftp_prefix
      || (strncmp(spt->filename, tftp_prefix, strlen(tftp_prefix)) != 0)) {
      tftp_send_error(spt, 2, "Access violation", tp);
      return;
  }

  /* check if the file exists */
  
  if (tftp_read_data(spt, 0, (u_int8_t *)spt->filename, 0) < 0) {
      tftp_send_error(spt, 1, "File not found", tp);
      return;
  }

  tftp_send_data(spt, 1, tp);
}

static void tftp_handle_ack(struct tftp_t *tp, int pktlen)
{
  int s;

  s = tftp_session_find(tp);

  if (s < 0) {
    return;
  }

  if (tftp_send_data(&tftp_sessions[s], 
                     ntohs(tp->x.tp_data.tp_block_nr) + 1, 
                     tp) < 0) {
    return;
  }
}

void tftp_input(struct mbuf *m)
{
  struct tftp_t *tp = (struct tftp_t *)m->m_data;

  switch(ntohs(tp->tp_op)) {
  case TFTP_RRQ:
    tftp_handle_rrq(tp, m->m_len);
    break;

  case TFTP_ACK:
    tftp_handle_ack(tp, m->m_len);
    break;
  }
}
Revision:	1.3
Committed:	2007-01-24T05:42:23Z (17 years, 3 months ago) by asvitkine
Content type:	text/plain
Branch:	MAIN
CVS Tags:	HEAD
Changes since 1.2:	+2 -1 lines
Log Message:	fix compile warning & potential buffer overflow at the same time
#	Content
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
27	struct tftp_session {
28	int in_use;
29	char filename[TFTP_FILENAME_MAX];
30
31	struct in_addr client_ip;
32	u_int16_t client_port;
33
34	int timestamp;
35	};
36
37	struct tftp_session tftp_sessions[TFTP_SESSIONS_MAX];
38
39	const char *tftp_prefix;
40
41	static void tftp_session_update(struct tftp_session *spt)
42	{
43	spt->timestamp = curtime;
44	spt->in_use = 1;
45	}
46
47	static void tftp_session_terminate(struct tftp_session *spt)
48	{
49	spt->in_use = 0;
50	}
51
52	static int tftp_session_allocate(struct tftp_t *tp)
53	{
54	struct tftp_session *spt;
55	int k;
56
57	for (k = 0; k < TFTP_SESSIONS_MAX; k++) {
58	spt = &tftp_sessions[k];
59
60	if (!spt->in_use)
61	goto found;
62
63	/* sessions time out after 5 inactive seconds */
64	if ((int)(curtime - spt->timestamp) > 5000)
65	goto found;
66	}
67
68	return -1;
69
70	found:
71	memset(spt, 0, sizeof(*spt));
72	memcpy(&spt->client_ip, &tp->ip.ip_src, sizeof(spt->client_ip));
73	spt->client_port = tp->udp.uh_sport;
74
75	tftp_session_update(spt);
76
77	return k;
78	}
79
80	static int tftp_session_find(struct tftp_t *tp)
81	{
82	struct tftp_session *spt;
83	int k;
84
85	for (k = 0; k < TFTP_SESSIONS_MAX; k++) {
86	spt = &tftp_sessions[k];
87
88	if (spt->in_use) {
89	if (!memcmp(&spt->client_ip, &tp->ip.ip_src, sizeof(spt->client_ip))) {
90	if (spt->client_port == tp->udp.uh_sport) {
91	return k;
92	}
93	}
94	}
95	}
96
97	return -1;
98	}
99
100	static int tftp_read_data(struct tftp_session *spt, u_int16_t block_nr,
101	u_int8_t *buf, int len)
102	{
103	int fd;
104	int bytes_read = 0;
105
106	fd = open(spt->filename, O_RDONLY \| O_BINARY);
107
108	if (fd < 0) {
109	return -1;
110	}
111
112	if (len) {
113	lseek(fd, block_nr * 512, SEEK_SET);
114
115	bytes_read = read(fd, buf, len);
116	}
117
118	close(fd);
119
120	return bytes_read;
121	}
122
123	static int tftp_send_error(struct tftp_session *spt,
124	u_int16_t errorcode, const char *msg,
125	struct tftp_t *recv_tp)
126	{
127	struct sockaddr_in saddr, daddr;
128	struct mbuf *m;
129	struct tftp_t *tp;
130	int nobytes;
131
132	m = m_get();
133
134	if (!m) {
135	return -1;
136	}
137
138	memset(m->m_data, 0, m->m_size);
139
140	m->m_data += if_maxlinkhdr;
141	tp = (void *)m->m_data;
142	m->m_data += sizeof(struct udpiphdr);
143
144	tp->tp_op = htons(TFTP_ERROR);
145	tp->x.tp_error.tp_error_code = htons(errorcode);
146	strncpy((char *)tp->x.tp_error.tp_msg, msg, sizeof(tp->x.tp_error.tp_msg));
147	tp->x.tp_error.tp_msg[sizeof(tp->x.tp_error.tp_msg)-1] = 0;
148
149	saddr.sin_addr = recv_tp->ip.ip_dst;
150	saddr.sin_port = recv_tp->udp.uh_dport;
151
152	daddr.sin_addr = spt->client_ip;
153	daddr.sin_port = spt->client_port;
154
155	nobytes = 2;
156
157	m->m_len = sizeof(struct tftp_t) - 514 + 3 + strlen(msg) -
158	sizeof(struct ip) - sizeof(struct udphdr);
159
160	udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
161
162	tftp_session_terminate(spt);
163
164	return 0;
165	}
166
167	static int tftp_send_data(struct tftp_session *spt,
168	u_int16_t block_nr,
169	struct tftp_t *recv_tp)
170	{
171	struct sockaddr_in saddr, daddr;
172	struct mbuf *m;
173	struct tftp_t *tp;
174	int nobytes;
175
176	if (block_nr < 1) {
177	return -1;
178	}
179
180	m = m_get();
181
182	if (!m) {
183	return -1;
184	}
185
186	memset(m->m_data, 0, m->m_size);
187
188	m->m_data += if_maxlinkhdr;
189	tp = (void *)m->m_data;
190	m->m_data += sizeof(struct udpiphdr);
191
192	tp->tp_op = htons(TFTP_DATA);
193	tp->x.tp_data.tp_block_nr = htons(block_nr);
194
195	saddr.sin_addr = recv_tp->ip.ip_dst;
196	saddr.sin_port = recv_tp->udp.uh_dport;
197
198	daddr.sin_addr = spt->client_ip;
199	daddr.sin_port = spt->client_port;
200
201	nobytes = tftp_read_data(spt, block_nr - 1, tp->x.tp_data.tp_buf, 512);
202
203	if (nobytes < 0) {
204	m_free(m);
205
206	/* send "file not found" error back */
207
208	tftp_send_error(spt, 1, "File not found", tp);
209
210	return -1;
211	}
212
213	m->m_len = sizeof(struct tftp_t) - (512 - nobytes) -
214	sizeof(struct ip) - sizeof(struct udphdr);
215
216	udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
217
218	if (nobytes == 512) {
219	tftp_session_update(spt);
220	}
221	else {
222	tftp_session_terminate(spt);
223	}
224
225	return 0;
226	}
227
228	static void tftp_handle_rrq(struct tftp_t *tp, int pktlen)
229	{
230	struct tftp_session *spt;
231	int s, k, n;
232	u_int8_t src, dst;
233
234	s = tftp_session_allocate(tp);
235
236	if (s < 0) {
237	return;
238	}
239
240	spt = &tftp_sessions[s];
241
242	src = tp->x.tp_buf;
243	dst = (u_int8_t *)spt->filename;
244	n = pktlen - ((uint8_t )&tp->x.tp_buf[0] - (uint8_t )tp);
245
246	/* get name */
247
248	for (k = 0; k < n; k++) {
249	if (k < TFTP_FILENAME_MAX) {
250	dst[k] = src[k];
251	}
252	else {
253	return;
254	}
255
256	if (src[k] == '\0') {
257	break;
258	}
259	}
260
261	if (k >= n) {
262	return;
263	}
264
265	k++;
266
267	/* check mode */
268	if ((n - k) < 6) {
269	return;
270	}
271
272	if (memcmp(&src[k], "octet\0", 6) != 0) {
273	tftp_send_error(spt, 4, "Unsupported transfer mode", tp);
274	return;
275	}
276
277	/* do sanity checks on the filename */
278
279	if ((spt->filename[0] != '/')
280	\|\| (spt->filename[strlen(spt->filename) - 1] == '/')
281	\|\| strstr(spt->filename, "/../")) {
282	tftp_send_error(spt, 2, "Access violation", tp);
283	return;
284	}
285
286	/* only allow exported prefixes */
287
288	if (!tftp_prefix
289	\|\| (strncmp(spt->filename, tftp_prefix, strlen(tftp_prefix)) != 0)) {
290	tftp_send_error(spt, 2, "Access violation", tp);
291	return;
292	}
293
294	/* check if the file exists */
295
296	if (tftp_read_data(spt, 0, (u_int8_t *)spt->filename, 0) < 0) {
297	tftp_send_error(spt, 1, "File not found", tp);
298	return;
299	}
300
301	tftp_send_data(spt, 1, tp);
302	}
303
304	static void tftp_handle_ack(struct tftp_t *tp, int pktlen)
305	{
306	int s;
307
308	s = tftp_session_find(tp);
309
310	if (s < 0) {
311	return;
312	}
313
314	if (tftp_send_data(&tftp_sessions[s],
315	ntohs(tp->x.tp_data.tp_block_nr) + 1,
316	tp) < 0) {
317	return;
318	}
319	}
320
321	void tftp_input(struct mbuf *m)
322	{
323	struct tftp_t tp = (struct tftp_t )m->m_data;
324
325	switch(ntohs(tp->tp_op)) {
326	case TFTP_RRQ:
327	tftp_handle_rrq(tp, m->m_len);
328	break;
329
330	case TFTP_ACK:
331	tftp_handle_ack(tp, m->m_len);
332	break;
333	}
334	}