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, 4 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
#	User	Rev	Content
1	gbeauche	1.1	/*
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	cebix	1.2	char filename[TFTP_FILENAME_MAX];
30	gbeauche	1.1
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	asvitkine	1.3	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	gbeauche	1.1
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	cebix	1.2	dst = (u_int8_t *)spt->filename;
244	gbeauche	1.1	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	cebix	1.2	if (tftp_read_data(spt, 0, (u_int8_t *)spt->filename, 0) < 0) {
297	gbeauche	1.1	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			}