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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: unsigned 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: strcpy(tp->x.tp_error.tp_msg, msg);
147:
148: saddr.sin_addr = recv_tp->ip.ip_dst;
149: saddr.sin_port = recv_tp->udp.uh_dport;
150:
151: daddr.sin_addr = spt->client_ip;
152: daddr.sin_port = spt->client_port;
153:
154: nobytes = 2;
155:
156: m->m_len = sizeof(struct tftp_t) - 514 + 3 + strlen(msg) -
157: sizeof(struct ip) - sizeof(struct udphdr);
158:
159: udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
160:
161: tftp_session_terminate(spt);
162:
163: return 0;
164: }
165:
166: static int tftp_send_data(struct tftp_session *spt,
167: u_int16_t block_nr,
168: struct tftp_t *recv_tp)
169: {
170: struct sockaddr_in saddr, daddr;
171: struct mbuf *m;
172: struct tftp_t *tp;
173: int nobytes;
174:
175: if (block_nr < 1) {
176: return -1;
177: }
178:
179: m = m_get();
180:
181: if (!m) {
182: return -1;
183: }
184:
185: memset(m->m_data, 0, m->m_size);
186:
187: m->m_data += if_maxlinkhdr;
188: tp = (void *)m->m_data;
189: m->m_data += sizeof(struct udpiphdr);
190:
191: tp->tp_op = htons(TFTP_DATA);
192: tp->x.tp_data.tp_block_nr = htons(block_nr);
193:
194: saddr.sin_addr = recv_tp->ip.ip_dst;
195: saddr.sin_port = recv_tp->udp.uh_dport;
196:
197: daddr.sin_addr = spt->client_ip;
198: daddr.sin_port = spt->client_port;
199:
200: nobytes = tftp_read_data(spt, block_nr - 1, tp->x.tp_data.tp_buf, 512);
201:
202: if (nobytes < 0) {
203: m_free(m);
204:
205: /* send "file not found" error back */
206:
207: tftp_send_error(spt, 1, "File not found", tp);
208:
209: return -1;
210: }
211:
212: m->m_len = sizeof(struct tftp_t) - (512 - nobytes) -
213: sizeof(struct ip) - sizeof(struct udphdr);
214:
215: udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
216:
217: if (nobytes == 512) {
218: tftp_session_update(spt);
219: }
220: else {
221: tftp_session_terminate(spt);
222: }
223:
224: return 0;
225: }
226:
227: static void tftp_handle_rrq(struct tftp_t *tp, int pktlen)
228: {
229: struct tftp_session *spt;
230: int s, k, n;
231: u_int8_t *src, *dst;
232:
233: s = tftp_session_allocate(tp);
234:
235: if (s < 0) {
236: return;
237: }
238:
239: spt = &tftp_sessions[s];
240:
241: src = tp->x.tp_buf;
242: dst = spt->filename;
243: n = pktlen - ((uint8_t *)&tp->x.tp_buf[0] - (uint8_t *)tp);
244:
245: /* get name */
246:
247: for (k = 0; k < n; k++) {
248: if (k < TFTP_FILENAME_MAX) {
249: dst[k] = src[k];
250: }
251: else {
252: return;
253: }
254:
255: if (src[k] == '\0') {
256: break;
257: }
258: }
259:
260: if (k >= n) {
261: return;
262: }
263:
264: k++;
265:
266: /* check mode */
267: if ((n - k) < 6) {
268: return;
269: }
270:
271: if (memcmp(&src[k], "octet\0", 6) != 0) {
272: tftp_send_error(spt, 4, "Unsupported transfer mode", tp);
273: return;
274: }
275:
276: /* do sanity checks on the filename */
277:
278: if ((spt->filename[0] != '/')
279: || (spt->filename[strlen(spt->filename) - 1] == '/')
280: || strstr(spt->filename, "/../")) {
281: tftp_send_error(spt, 2, "Access violation", tp);
282: return;
283: }
284:
285: /* only allow exported prefixes */
286:
287: if (!tftp_prefix
288: || (strncmp(spt->filename, tftp_prefix, strlen(tftp_prefix)) != 0)) {
289: tftp_send_error(spt, 2, "Access violation", tp);
290: return;
291: }
292:
293: /* check if the file exists */
294:
295: if (tftp_read_data(spt, 0, spt->filename, 0) < 0) {
296: tftp_send_error(spt, 1, "File not found", tp);
297: return;
298: }
299:
300: tftp_send_data(spt, 1, tp);
301: }
302:
303: static void tftp_handle_ack(struct tftp_t *tp, int pktlen)
304: {
305: int s;
306:
307: s = tftp_session_find(tp);
308:
309: if (s < 0) {
310: return;
311: }
312:
313: if (tftp_send_data(&tftp_sessions[s],
314: ntohs(tp->x.tp_data.tp_block_nr) + 1,
315: tp) < 0) {
316: return;
317: }
318: }
319:
320: void tftp_input(struct mbuf *m)
321: {
322: struct tftp_t *tp = (struct tftp_t *)m->m_data;
323:
324: switch(ntohs(tp->tp_op)) {
325: case TFTP_RRQ:
326: tftp_handle_rrq(tp, m->m_len);
327: break;
328:
329: case TFTP_ACK:
330: tftp_handle_ack(tp, m->m_len);
331: break;
332: }
333: }
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