Annotation of /trunk/mkinitrd-magellan/busybox/networking/dnsd.c
Parent Directory | Revision Log
Revision 816 -
(hide annotations)
(download)
Fri Apr 24 18:33:46 2009 UTC (15 years, 1 month ago) by niro
File MIME type: text/plain
File size: 9893 byte(s)
Fri Apr 24 18:33:46 2009 UTC (15 years, 1 month ago) by niro
File MIME type: text/plain
File size: 9893 byte(s)
-updated to busybox-1.13.4
1 | niro | 532 | /* vi: set sw=4 ts=4: */ |
2 | /* | ||
3 | * Mini DNS server implementation for busybox | ||
4 | * | ||
5 | * Copyright (C) 2005 Roberto A. Foglietta (me@roberto.foglietta.name) | ||
6 | * Copyright (C) 2005 Odd Arild Olsen (oao at fibula dot no) | ||
7 | * Copyright (C) 2003 Paul Sheer | ||
8 | * | ||
9 | * Licensed under GPLv2 or later, see file LICENSE in this tarball for details. | ||
10 | * | ||
11 | * Odd Arild Olsen started out with the sheerdns [1] of Paul Sheer and rewrote | ||
12 | * it into a shape which I believe is both easier to understand and maintain. | ||
13 | * I also reused the input buffer for output and removed services he did not | ||
14 | * need. [1] http://threading.2038bug.com/sheerdns/ | ||
15 | * | ||
16 | * Some bugfix and minor changes was applied by Roberto A. Foglietta who made | ||
17 | * the first porting of oao' scdns to busybox also. | ||
18 | */ | ||
19 | |||
20 | niro | 816 | #include "libbb.h" |
21 | #include <syslog.h> | ||
22 | niro | 532 | |
23 | //#define DEBUG 1 | ||
24 | #define DEBUG 0 | ||
25 | |||
26 | enum { | ||
27 | MAX_HOST_LEN = 16, // longest host name allowed is 15 | ||
28 | IP_STRING_LEN = 18, // .xxx.xxx.xxx.xxx\0 | ||
29 | |||
30 | //must be strlen('.in-addr.arpa') larger than IP_STRING_LEN | ||
31 | MAX_NAME_LEN = (IP_STRING_LEN + 13), | ||
32 | |||
33 | /* Cannot get bigger packets than 512 per RFC1035 | ||
34 | In practice this can be set considerably smaller: | ||
35 | Length of response packet is header (12B) + 2*type(4B) + 2*class(4B) + | ||
36 | ttl(4B) + rlen(2B) + r (MAX_NAME_LEN =21B) + | ||
37 | 2*querystring (2 MAX_NAME_LEN= 42B), all together 90 Byte | ||
38 | */ | ||
39 | niro | 816 | MAX_PACK_LEN = 512, |
40 | niro | 532 | |
41 | DEFAULT_TTL = 30, // increase this when not testing? | ||
42 | |||
43 | REQ_A = 1, | ||
44 | REQ_PTR = 12 | ||
45 | }; | ||
46 | |||
47 | struct dns_head { // the message from client and first part of response mag | ||
48 | uint16_t id; | ||
49 | uint16_t flags; | ||
50 | uint16_t nquer; // accepts 0 | ||
51 | uint16_t nansw; // 1 in response | ||
52 | uint16_t nauth; // 0 | ||
53 | uint16_t nadd; // 0 | ||
54 | }; | ||
55 | struct dns_prop { | ||
56 | uint16_t type; | ||
57 | uint16_t class; | ||
58 | }; | ||
59 | struct dns_entry { // element of known name, ip address and reversed ip address | ||
60 | struct dns_entry *next; | ||
61 | char ip[IP_STRING_LEN]; // dotted decimal IP | ||
62 | char rip[IP_STRING_LEN]; // length decimal reversed IP | ||
63 | char name[MAX_HOST_LEN]; | ||
64 | }; | ||
65 | |||
66 | niro | 816 | static struct dns_entry *dnsentry; |
67 | niro | 532 | static uint32_t ttl = DEFAULT_TTL; |
68 | |||
69 | niro | 816 | static const char *fileconf = "/etc/dnsd.conf"; |
70 | |||
71 | // Must match getopt32 call | ||
72 | #define OPT_daemon (option_mask32 & 0x10) | ||
73 | #define OPT_verbose (option_mask32 & 0x20) | ||
74 | |||
75 | |||
76 | niro | 532 | /* |
77 | * Convert host name from C-string to dns length/string. | ||
78 | */ | ||
79 | static void convname(char *a, uint8_t *q) | ||
80 | { | ||
81 | int i = (q[0] == '.') ? 0 : 1; | ||
82 | for (; i < MAX_HOST_LEN-1 && *q; i++, q++) | ||
83 | a[i] = tolower(*q); | ||
84 | a[0] = i - 1; | ||
85 | a[i] = 0; | ||
86 | } | ||
87 | |||
88 | /* | ||
89 | * Insert length of substrings instead of dots | ||
90 | */ | ||
91 | static void undot(uint8_t * rip) | ||
92 | { | ||
93 | int i = 0, s = 0; | ||
94 | while (rip[i]) | ||
95 | i++; | ||
96 | for (--i; i >= 0; i--) { | ||
97 | if (rip[i] == '.') { | ||
98 | rip[i] = s; | ||
99 | s = 0; | ||
100 | } else s++; | ||
101 | } | ||
102 | } | ||
103 | |||
104 | /* | ||
105 | * Read hostname/IP records from file | ||
106 | */ | ||
107 | static void dnsentryinit(void) | ||
108 | { | ||
109 | niro | 816 | char *token[2]; |
110 | parser_t *parser; | ||
111 | niro | 532 | struct dns_entry *m, *prev; |
112 | niro | 816 | |
113 | niro | 532 | prev = dnsentry = NULL; |
114 | niro | 816 | parser = config_open(fileconf); |
115 | while (config_read(parser, token, 2, 2, "# \t", PARSE_NORMAL)) { | ||
116 | unsigned a, b, c, d; | ||
117 | /* | ||
118 | * Assumes all host names are lower case only | ||
119 | * Hostnames with more than one label are not handled correctly. | ||
120 | * Presently the dot is copied into name without | ||
121 | * converting to a length/string substring for that label. | ||
122 | */ | ||
123 | // if (!token[1] || sscanf(token[1], ".%u.%u.%u.%u"+1, &a, &b, &c, &d) != 4) | ||
124 | if (sscanf(token[1], ".%u.%u.%u.%u"+1, &a, &b, &c, &d) != 4) | ||
125 | continue; | ||
126 | niro | 532 | |
127 | niro | 816 | m = xzalloc(sizeof(*m)); |
128 | /*m->next = NULL;*/ | ||
129 | sprintf(m->ip, ".%u.%u.%u.%u"+1, a, b, c, d); | ||
130 | sprintf(m->rip, ".%u.%u.%u.%u", d, c, b, a); | ||
131 | undot((uint8_t*)m->rip); | ||
132 | convname(m->name, (uint8_t*)token[0]); | ||
133 | niro | 532 | |
134 | niro | 816 | if (OPT_verbose) |
135 | fprintf(stderr, "\tname:%s, ip:%s\n", &(m->name[1]), m->ip); | ||
136 | niro | 532 | |
137 | if (prev == NULL) | ||
138 | dnsentry = m; | ||
139 | else | ||
140 | prev->next = m; | ||
141 | prev = m; | ||
142 | } | ||
143 | niro | 816 | config_close(parser); |
144 | niro | 532 | } |
145 | |||
146 | /* | ||
147 | * Look query up in dns records and return answer if found | ||
148 | * qs is the query string, first byte the string length | ||
149 | */ | ||
150 | static int table_lookup(uint16_t type, uint8_t * as, uint8_t * qs) | ||
151 | { | ||
152 | int i; | ||
153 | niro | 816 | struct dns_entry *d = dnsentry; |
154 | niro | 532 | |
155 | do { | ||
156 | #if DEBUG | ||
157 | char *p,*q; | ||
158 | q = (char *)&(qs[1]); | ||
159 | p = &(d->name[1]); | ||
160 | fprintf(stderr, "\n%s: %d/%d p:%s q:%s %d", | ||
161 | __FUNCTION__, (int)strlen(p), (int)(d->name[0]), | ||
162 | p, q, (int)strlen(q)); | ||
163 | #endif | ||
164 | if (type == REQ_A) { /* search by host name */ | ||
165 | for (i = 1; i <= (int)(d->name[0]); i++) | ||
166 | if (tolower(qs[i]) != d->name[i]) | ||
167 | break; | ||
168 | niro | 816 | if (i > (int)(d->name[0]) || |
169 | (d->name[0] == 1 && d->name[1] == '*')) { | ||
170 | niro | 532 | strcpy((char *)as, d->ip); |
171 | #if DEBUG | ||
172 | niro | 816 | fprintf(stderr, " OK as:%s\n", as); |
173 | niro | 532 | #endif |
174 | niro | 816 | return 0; |
175 | niro | 532 | } |
176 | niro | 816 | } else if (type == REQ_PTR) { /* search by IP-address */ |
177 | if ((d->name[0] != 1 || d->name[1] != '*') && | ||
178 | !strncmp((char*)&d->rip[1], (char*)&qs[1], strlen(d->rip)-1)) { | ||
179 | niro | 532 | strcpy((char *)as, d->name); |
180 | return 0; | ||
181 | } | ||
182 | } | ||
183 | d = d->next; | ||
184 | } while (d); | ||
185 | return -1; | ||
186 | } | ||
187 | |||
188 | /* | ||
189 | * Decode message and generate answer | ||
190 | */ | ||
191 | niro | 816 | static int process_packet(uint8_t *buf) |
192 | niro | 532 | { |
193 | niro | 816 | uint8_t answstr[MAX_NAME_LEN + 1]; |
194 | niro | 532 | struct dns_head *head; |
195 | struct dns_prop *qprop; | ||
196 | niro | 816 | uint8_t *from, *answb; |
197 | uint16_t outr_rlen; | ||
198 | uint16_t outr_flags; | ||
199 | niro | 532 | uint16_t flags; |
200 | niro | 816 | int lookup_result, type, packet_len; |
201 | int querystr_len; | ||
202 | niro | 532 | |
203 | answstr[0] = '\0'; | ||
204 | |||
205 | head = (struct dns_head *)buf; | ||
206 | niro | 816 | if (head->nquer == 0) { |
207 | bb_error_msg("no queries"); | ||
208 | return -1; | ||
209 | } | ||
210 | niro | 532 | |
211 | niro | 816 | if (head->flags & 0x8000) { |
212 | bb_error_msg("ignoring response packet"); | ||
213 | return -1; | ||
214 | } | ||
215 | niro | 532 | |
216 | from = (void *)&head[1]; // start of query string | ||
217 | niro | 816 | //FIXME: strlen of untrusted data??! |
218 | querystr_len = strlen((char *)from) + 1 + sizeof(struct dns_prop); | ||
219 | answb = from + querystr_len; // where to append answer block | ||
220 | niro | 532 | |
221 | niro | 816 | outr_rlen = 0; |
222 | outr_flags = 0; | ||
223 | niro | 532 | |
224 | qprop = (struct dns_prop *)(answb - 4); | ||
225 | type = ntohs(qprop->type); | ||
226 | |||
227 | // only let REQ_A and REQ_PTR pass | ||
228 | if (!(type == REQ_A || type == REQ_PTR)) { | ||
229 | goto empty_packet; /* we can't handle the query type */ | ||
230 | } | ||
231 | |||
232 | if (ntohs(qprop->class) != 1 /* class INET */ ) { | ||
233 | niro | 816 | outr_flags = 4; /* not supported */ |
234 | niro | 532 | goto empty_packet; |
235 | } | ||
236 | /* we only support standard queries */ | ||
237 | |||
238 | if ((ntohs(head->flags) & 0x7800) != 0) | ||
239 | goto empty_packet; | ||
240 | |||
241 | // We have a standard query | ||
242 | bb_info_msg("%s", (char *)from); | ||
243 | niro | 816 | lookup_result = table_lookup(type, answstr, from); |
244 | niro | 532 | if (lookup_result != 0) { |
245 | niro | 816 | outr_flags = 3 | 0x0400; // name do not exist and auth |
246 | niro | 532 | goto empty_packet; |
247 | } | ||
248 | if (type == REQ_A) { // return an address | ||
249 | niro | 816 | struct in_addr a; // NB! its "struct { unsigned __long__ s_addr; }" |
250 | uint32_t v32; | ||
251 | if (!inet_aton((char*)answstr, &a)) { //dotted dec to long conv | ||
252 | outr_flags = 1; /* Frmt err */ | ||
253 | niro | 532 | goto empty_packet; |
254 | } | ||
255 | niro | 816 | v32 = a.s_addr; /* in case long != int */ |
256 | memcpy(answstr, &v32, 4); | ||
257 | outr_rlen = 4; // uint32_t IP | ||
258 | } else | ||
259 | outr_rlen = strlen((char *)answstr) + 1; // a host name | ||
260 | outr_flags |= 0x0400; /* authority-bit */ | ||
261 | niro | 532 | // we have an answer |
262 | head->nansw = htons(1); | ||
263 | |||
264 | // copy query block to answer block | ||
265 | niro | 816 | memcpy(answb, from, querystr_len); |
266 | answb += querystr_len; | ||
267 | niro | 532 | |
268 | // and append answer rr | ||
269 | niro | 816 | // FIXME: unaligned accesses?? |
270 | *(uint32_t *) answb = htonl(ttl); | ||
271 | answb += 4; | ||
272 | *(uint16_t *) answb = htons(outr_rlen); | ||
273 | answb += 2; | ||
274 | memcpy(answb, answstr, outr_rlen); | ||
275 | answb += outr_rlen; | ||
276 | niro | 532 | |
277 | empty_packet: | ||
278 | |||
279 | flags = ntohs(head->flags); | ||
280 | // clear rcode and RA, set responsebit and our new flags | ||
281 | niro | 816 | flags |= (outr_flags & 0xff80) | 0x8000; |
282 | niro | 532 | head->flags = htons(flags); |
283 | niro | 816 | head->nauth = head->nadd = 0; |
284 | niro | 532 | head->nquer = htons(1); |
285 | |||
286 | niro | 816 | packet_len = answb - buf; |
287 | niro | 532 | return packet_len; |
288 | } | ||
289 | |||
290 | /* | ||
291 | * Exit on signal | ||
292 | */ | ||
293 | niro | 816 | static void interrupt(int sig) |
294 | niro | 532 | { |
295 | niro | 816 | /* unlink("/var/run/dnsd.lock"); */ |
296 | niro | 532 | bb_error_msg("interrupt, exiting\n"); |
297 | niro | 816 | kill_myself_with_sig(sig); |
298 | niro | 532 | } |
299 | |||
300 | niro | 816 | int dnsd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; |
301 | int dnsd_main(int argc UNUSED_PARAM, char **argv) | ||
302 | niro | 532 | { |
303 | niro | 816 | const char *listen_interface = "0.0.0.0"; |
304 | niro | 532 | char *sttl, *sport; |
305 | niro | 816 | len_and_sockaddr *lsa, *from, *to; |
306 | unsigned lsa_size; | ||
307 | niro | 532 | int udps; |
308 | uint16_t port = 53; | ||
309 | niro | 816 | /* Paranoid sizing: querystring x2 + ttl + outr_rlen + answstr */ |
310 | /* I'd rather see process_packet() fixed instead... */ | ||
311 | uint8_t buf[MAX_PACK_LEN * 2 + 4 + 2 + (MAX_NAME_LEN+1)]; | ||
312 | niro | 532 | |
313 | niro | 816 | getopt32(argv, "i:c:t:p:dv", &listen_interface, &fileconf, &sttl, &sport); |
314 | niro | 532 | //if (option_mask32 & 0x1) // -i |
315 | //if (option_mask32 & 0x2) // -c | ||
316 | if (option_mask32 & 0x4) // -t | ||
317 | ttl = xatou_range(sttl, 1, 0xffffffff); | ||
318 | if (option_mask32 & 0x8) // -p | ||
319 | niro | 816 | port = xatou_range(sport, 1, 0xffff); |
320 | niro | 532 | |
321 | if (OPT_verbose) { | ||
322 | bb_info_msg("listen_interface: %s", listen_interface); | ||
323 | bb_info_msg("ttl: %d, port: %d", ttl, port); | ||
324 | bb_info_msg("fileconf: %s", fileconf); | ||
325 | } | ||
326 | |||
327 | if (OPT_daemon) { | ||
328 | niro | 816 | bb_daemonize_or_rexec(DAEMON_CLOSE_EXTRA_FDS, argv); |
329 | openlog(applet_name, LOG_PID, LOG_DAEMON); | ||
330 | niro | 532 | logmode = LOGMODE_SYSLOG; |
331 | } | ||
332 | |||
333 | dnsentryinit(); | ||
334 | |||
335 | signal(SIGINT, interrupt); | ||
336 | niro | 816 | bb_signals(0 |
337 | /* why? + (1 << SIGPIPE) */ | ||
338 | + (1 << SIGHUP) | ||
339 | niro | 532 | #ifdef SIGTSTP |
340 | niro | 816 | + (1 << SIGTSTP) |
341 | niro | 532 | #endif |
342 | #ifdef SIGURG | ||
343 | niro | 816 | + (1 << SIGURG) |
344 | niro | 532 | #endif |
345 | niro | 816 | , SIG_IGN); |
346 | niro | 532 | |
347 | niro | 816 | lsa = xdotted2sockaddr(listen_interface, port); |
348 | udps = xsocket(lsa->u.sa.sa_family, SOCK_DGRAM, 0); | ||
349 | xbind(udps, &lsa->u.sa, lsa->len); | ||
350 | socket_want_pktinfo(udps); /* needed for recv_from_to to work */ | ||
351 | lsa_size = LSA_LEN_SIZE + lsa->len; | ||
352 | from = xzalloc(lsa_size); | ||
353 | to = xzalloc(lsa_size); | ||
354 | |||
355 | niro | 532 | bb_info_msg("Accepting UDP packets on %s", |
356 | niro | 816 | xmalloc_sockaddr2dotted(&lsa->u.sa)); |
357 | niro | 532 | |
358 | while (1) { | ||
359 | int r; | ||
360 | niro | 816 | /* Try to get *DEST* address (to which of our addresses |
361 | * this query was directed), and reply from the same address. | ||
362 | * Or else we can exhibit usual UDP ugliness: | ||
363 | * [ip1.multihomed.ip2] <= query to ip1 <= peer | ||
364 | * [ip1.multihomed.ip2] => reply from ip2 => peer (confused) */ | ||
365 | memcpy(to, lsa, lsa_size); | ||
366 | r = recv_from_to(udps, buf, MAX_PACK_LEN + 1, 0, &from->u.sa, &to->u.sa, lsa->len); | ||
367 | if (r < 12 || r > MAX_PACK_LEN) { | ||
368 | bb_error_msg("invalid packet size"); | ||
369 | continue; | ||
370 | niro | 532 | } |
371 | niro | 816 | if (OPT_verbose) |
372 | bb_info_msg("Got UDP packet"); | ||
373 | buf[r] = '\0'; /* paranoia */ | ||
374 | r = process_packet(buf); | ||
375 | if (r <= 0) | ||
376 | continue; | ||
377 | send_to_from(udps, buf, r, 0, &from->u.sa, &to->u.sa, lsa->len); | ||
378 | niro | 532 | } |
379 | niro | 816 | return 0; |
380 | niro | 532 | } |