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1.1 root 1: /*
2: * tftp.c - a simple, read-only tftp server for qemu
3: *
4: * Copyright (c) 2004 Magnus Damm <[email protected]>
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: }
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