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c988f1f4 | 1 | /* $Cambridge: exim/src/src/lookups/dnsdb.c,v 1.8 2005/01/04 10:00:44 ph10 Exp $ */ |
0756eb3c PH |
2 | |
3 | /************************************************* | |
4 | * Exim - an Internet mail transport agent * | |
5 | *************************************************/ | |
6 | ||
c988f1f4 | 7 | /* Copyright (c) University of Cambridge 1995 - 2005 */ |
0756eb3c PH |
8 | /* See the file NOTICE for conditions of use and distribution. */ |
9 | ||
10 | #include "../exim.h" | |
11 | #include "lf_functions.h" | |
12 | #include "dnsdb.h" | |
13 | ||
14 | ||
15 | ||
16 | /* Ancient systems (e.g. SunOS4) don't appear to have T_TXT defined in their | |
17 | header files. */ | |
18 | ||
19 | #ifndef T_TXT | |
20 | #define T_TXT 16 | |
21 | #endif | |
22 | ||
23 | /* Table of recognized DNS record types and their integer values. */ | |
24 | ||
25 | static char *type_names[] = { | |
26 | "a", | |
27 | #if HAVE_IPV6 | |
28 | "aaaa", | |
29 | #ifdef SUPPORT_A6 | |
30 | "a6", | |
31 | #endif | |
32 | #endif | |
33 | "cname", | |
34 | "mx", | |
ea3bc19b | 35 | "mxh", |
0756eb3c PH |
36 | "ns", |
37 | "ptr", | |
38 | "srv", | |
33397d19 PH |
39 | "txt", |
40 | "zns" | |
41 | }; | |
0756eb3c PH |
42 | |
43 | static int type_values[] = { | |
44 | T_A, | |
45 | #if HAVE_IPV6 | |
46 | T_AAAA, | |
47 | #ifdef SUPPORT_A6 | |
48 | T_A6, | |
49 | #endif | |
50 | #endif | |
51 | T_CNAME, | |
52 | T_MX, | |
ea3bc19b | 53 | T_MXH, /* Private type for "MX hostnames" */ |
0756eb3c PH |
54 | T_NS, |
55 | T_PTR, | |
56 | T_SRV, | |
33397d19 PH |
57 | T_TXT, |
58 | T_ZNS /* Private type for "zone nameservers" */ | |
59 | }; | |
0756eb3c PH |
60 | |
61 | ||
62 | /************************************************* | |
63 | * Open entry point * | |
64 | *************************************************/ | |
65 | ||
66 | /* See local README for interface description. */ | |
67 | ||
68 | void * | |
69 | dnsdb_open(uschar *filename, uschar **errmsg) | |
70 | { | |
71 | filename = filename; /* Keep picky compilers happy */ | |
72 | errmsg = errmsg; /* Ditto */ | |
73 | return (void *)(-1); /* Any non-0 value */ | |
74 | } | |
75 | ||
76 | ||
77 | ||
78 | /************************************************* | |
79 | * Find entry point for dnsdb * | |
80 | *************************************************/ | |
81 | ||
7bb56e1f PH |
82 | /* See local README for interface description. The query in the "keystring" may |
83 | consist of a number of parts. | |
84 | ||
85 | (a) If the first significant character is '>' then the next character is the | |
86 | separator character that is used when multiple records are found. The default | |
87 | separator is newline. | |
88 | ||
ff4dbb19 PH |
89 | (b) If the next sequence of characters is 'defer_FOO' followed by a comma, |
90 | the defer behaviour is set to FOO. The possible behaviours are: 'strict', where | |
91 | any defer causes the whole lookup to defer; 'lax', where a defer causes the | |
92 | whole lookup to defer only if none of the DNS queries succeeds; and 'never', | |
93 | where all defers are as if the lookup failed. The default is 'lax'. | |
94 | ||
95 | (c) If the next sequence of characters is a sequence of letters and digits | |
7bb56e1f | 96 | followed by '=', it is interpreted as the name of the DNS record type. The |
ff4dbb19 | 97 | default is "TXT". |
7bb56e1f | 98 | |
ff4dbb19 | 99 | (d) Then there follows list of domain names. This is a generalized Exim list, |
7bb56e1f PH |
100 | which may start with '<' in order to set a specific separator. The default |
101 | separator, as always, is colon. */ | |
0756eb3c PH |
102 | |
103 | int | |
104 | dnsdb_find(void *handle, uschar *filename, uschar *keystring, int length, | |
105 | uschar **result, uschar **errmsg, BOOL *do_cache) | |
106 | { | |
107 | int rc; | |
108 | int size = 256; | |
109 | int ptr = 0; | |
7bb56e1f | 110 | int sep = 0; |
ff4dbb19 | 111 | int defer_mode = PASS; |
0756eb3c | 112 | int type = T_TXT; |
c38d6da9 | 113 | int failrc = FAIL; |
7bb56e1f PH |
114 | uschar *outsep = US"\n"; |
115 | uschar *equals, *domain; | |
0756eb3c PH |
116 | uschar buffer[256]; |
117 | ||
118 | /* Because we're the working in the search pool, we try to reclaim as much | |
119 | store as possible later, so we preallocate the result here */ | |
120 | ||
121 | uschar *yield = store_get(size); | |
122 | ||
123 | dns_record *rr; | |
124 | dns_answer dnsa; | |
125 | dns_scan dnss; | |
126 | ||
127 | handle = handle; /* Keep picky compilers happy */ | |
128 | filename = filename; | |
129 | length = length; | |
130 | do_cache = do_cache; | |
131 | ||
7bb56e1f | 132 | /* If the string starts with '>' we change the output separator */ |
0756eb3c | 133 | |
7bb56e1f PH |
134 | while (isspace(*keystring)) keystring++; |
135 | if (*keystring == '>') | |
0756eb3c | 136 | { |
7bb56e1f PH |
137 | outsep = keystring + 1; |
138 | keystring += 2; | |
139 | while (isspace(*keystring)) keystring++; | |
140 | } | |
141 | ||
ff4dbb19 PH |
142 | /* Check for a defer behaviour keyword. */ |
143 | ||
144 | if (strncmpic(keystring, US"defer_", 6) == 0) | |
145 | { | |
146 | keystring += 6; | |
147 | if (strncmpic(keystring, US"strict", 6) == 0) | |
148 | { | |
149 | defer_mode = DEFER; | |
150 | keystring += 6; | |
151 | } | |
152 | else if (strncmpic(keystring, US"lax", 3) == 0) | |
153 | { | |
154 | defer_mode = PASS; | |
155 | keystring += 3; | |
156 | } | |
157 | else if (strncmpic(keystring, US"never", 5) == 0) | |
158 | { | |
159 | defer_mode = OK; | |
160 | keystring += 5; | |
161 | } | |
162 | else | |
163 | { | |
164 | *errmsg = US"unsupported dnsdb defer behaviour"; | |
165 | return DEFER; | |
166 | } | |
167 | while (isspace(*keystring)) keystring++; | |
168 | if (*keystring++ != ',') | |
169 | { | |
170 | *errmsg = US"dnsdb defer behaviour syntax error"; | |
171 | return DEFER; | |
172 | } | |
173 | while (isspace(*keystring)) keystring++; | |
174 | } | |
175 | ||
7bb56e1f PH |
176 | /* If the keystring contains an = this must be preceded by a valid type name. */ |
177 | ||
178 | if ((equals = Ustrchr(keystring, '=')) != NULL) | |
179 | { | |
180 | int i, len; | |
181 | uschar *tend = equals; | |
182 | ||
183 | while (tend > keystring && isspace(tend[-1])) tend--; | |
184 | len = tend - keystring; | |
185 | ||
0756eb3c PH |
186 | for (i = 0; i < sizeof(type_names)/sizeof(uschar *); i++) |
187 | { | |
188 | if (len == Ustrlen(type_names[i]) && | |
189 | strncmpic(keystring, US type_names[i], len) == 0) | |
190 | { | |
191 | type = type_values[i]; | |
192 | break; | |
193 | } | |
194 | } | |
7bb56e1f | 195 | |
0756eb3c PH |
196 | if (i >= sizeof(type_names)/sizeof(uschar *)) |
197 | { | |
198 | *errmsg = US"unsupported DNS record type"; | |
199 | return DEFER; | |
200 | } | |
7bb56e1f PH |
201 | |
202 | keystring = equals + 1; | |
203 | while (isspace(*keystring)) keystring++; | |
0756eb3c | 204 | } |
7bb56e1f PH |
205 | |
206 | /* Initialize the resolver in case this is the first time it has been used. */ | |
0756eb3c PH |
207 | |
208 | dns_init(FALSE, FALSE); | |
0756eb3c | 209 | |
7bb56e1f PH |
210 | /* The remainder of the string must be a list of domains. As long as the lookup |
211 | for at least one of them succeeds, we return success. Failure means that none | |
212 | of them were found. | |
0756eb3c | 213 | |
7bb56e1f PH |
214 | The original implementation did not support a list of domains. Adding the list |
215 | feature is compatible, except in one case: when PTR records are being looked up | |
216 | for a single IPv6 address. Fortunately, we can hack in a compatibility feature | |
217 | here: If the type is PTR and no list separator is specified, and the entire | |
218 | remaining string is valid as an IP address, set an impossible separator so that | |
219 | it is treated as one item. */ | |
33397d19 | 220 | |
7bb56e1f PH |
221 | if (type == T_PTR && keystring[0] != '<' && |
222 | string_is_ip_address(keystring, NULL) > 0) | |
223 | sep = -1; | |
0756eb3c | 224 | |
7bb56e1f | 225 | /* Now scan the list and do a lookup for each item */ |
0756eb3c | 226 | |
7bb56e1f PH |
227 | while ((domain = string_nextinlist(&keystring, &sep, buffer, sizeof(buffer))) |
228 | != NULL) | |
229 | { | |
230 | uschar rbuffer[256]; | |
ea3bc19b PH |
231 | int searchtype = (type == T_ZNS)? T_NS : /* record type we want */ |
232 | (type == T_MXH)? T_MX : type; | |
0756eb3c | 233 | |
7102e136 PH |
234 | /* If the type is PTR, we have to construct the relevant magic lookup key if |
235 | the original is an IP address (some experimental protocols are using PTR | |
236 | records for different purposes where the key string is a host name). This | |
237 | code for doing the reversal is now in a separate function. */ | |
7bb56e1f | 238 | |
7102e136 | 239 | if (type == T_PTR && string_is_ip_address(domain, NULL)) |
0756eb3c | 240 | { |
7bb56e1f PH |
241 | dns_build_reverse(domain, rbuffer); |
242 | domain = rbuffer; | |
0756eb3c | 243 | } |
7bb56e1f PH |
244 | |
245 | DEBUG(D_lookup) debug_printf("dnsdb key: %s\n", domain); | |
246 | ||
ea3bc19b PH |
247 | /* Do the lookup and sort out the result. There are two special types that |
248 | are handled specially: T_ZNS and T_MXH. The former is handled in a special | |
249 | lookup function so that the facility could be used from other parts of the | |
250 | Exim code. The latter affects only what happens later on in this function, | |
251 | but for tidiness it is handled in a similar way. If the lookup fails, | |
c38d6da9 PH |
252 | continue with the next domain. In the case of DEFER, adjust the final |
253 | "nothing found" result, but carry on to the next domain. */ | |
7bb56e1f PH |
254 | |
255 | rc = dns_special_lookup(&dnsa, domain, type, NULL); | |
256 | ||
257 | if (rc == DNS_NOMATCH || rc == DNS_NODATA) continue; | |
c38d6da9 PH |
258 | if (rc != DNS_SUCCEED) |
259 | { | |
ff4dbb19 PH |
260 | if (defer_mode == DEFER) return DEFER; /* always defer */ |
261 | else if (defer_mode == PASS) failrc = DEFER; /* defer only if all do */ | |
262 | continue; /* treat defer as fail */ | |
c38d6da9 | 263 | } |
7bb56e1f | 264 | |
ea3bc19b PH |
265 | /* Search the returned records */ |
266 | ||
7bb56e1f PH |
267 | for (rr = dns_next_rr(&dnsa, &dnss, RESET_ANSWERS); |
268 | rr != NULL; | |
269 | rr = dns_next_rr(&dnsa, &dnss, RESET_NEXT)) | |
0756eb3c | 270 | { |
ea3bc19b | 271 | if (rr->type != searchtype) continue; |
7bb56e1f PH |
272 | |
273 | /* There may be several addresses from an A6 record. Put the configured | |
274 | separator between them, just as for between several records. However, A6 | |
275 | support is not normally configured these days. */ | |
276 | ||
277 | if (type == T_A || | |
278 | #ifdef SUPPORT_A6 | |
279 | type == T_A6 || | |
280 | #endif | |
281 | type == T_AAAA) | |
0756eb3c | 282 | { |
7bb56e1f PH |
283 | dns_address *da; |
284 | for (da = dns_address_from_rr(&dnsa, rr); da != NULL; da = da->next) | |
285 | { | |
286 | if (ptr != 0) yield = string_cat(yield, &size, &ptr, outsep, 1); | |
287 | yield = string_cat(yield, &size, &ptr, da->address, | |
288 | Ustrlen(da->address)); | |
289 | } | |
290 | continue; | |
0756eb3c | 291 | } |
7bb56e1f PH |
292 | |
293 | /* Other kinds of record just have one piece of data each, but there may be | |
294 | several of them, of course. */ | |
295 | ||
296 | if (ptr != 0) yield = string_cat(yield, &size, &ptr, outsep, 1); | |
297 | ||
298 | if (type == T_TXT) | |
0756eb3c | 299 | { |
7bb56e1f PH |
300 | yield = string_cat(yield, &size, &ptr, (uschar *)(rr->data+1), |
301 | (rr->data)[0]); | |
0756eb3c | 302 | } |
ea3bc19b | 303 | else /* T_CNAME, T_MX, T_MXH, T_NS, T_SRV, T_PTR */ |
0756eb3c | 304 | { |
ea3bc19b | 305 | int num; |
7bb56e1f PH |
306 | uschar s[264]; |
307 | uschar *p = (uschar *)(rr->data); | |
ea3bc19b PH |
308 | |
309 | if (type == T_MXH) | |
310 | { | |
311 | /* mxh ignores the priority number and includes only the hostnames */ | |
312 | GETSHORT(num, p); /* pointer is advanced */ | |
313 | } | |
314 | else if (type == T_MX) | |
7bb56e1f | 315 | { |
7bb56e1f PH |
316 | GETSHORT(num, p); /* pointer is advanced */ |
317 | sprintf(CS s, "%d ", num); | |
318 | yield = string_cat(yield, &size, &ptr, s, Ustrlen(s)); | |
319 | } | |
320 | else if (type == T_SRV) | |
321 | { | |
ea3bc19b | 322 | int weight, port; |
7bb56e1f PH |
323 | GETSHORT(num, p); /* pointer is advanced */ |
324 | GETSHORT(weight, p); | |
325 | GETSHORT(port, p); | |
326 | sprintf(CS s, "%d %d %d ", num, weight, port); | |
327 | yield = string_cat(yield, &size, &ptr, s, Ustrlen(s)); | |
328 | } | |
ea3bc19b | 329 | |
7bb56e1f PH |
330 | rc = dn_expand(dnsa.answer, dnsa.answer + dnsa.answerlen, p, |
331 | (DN_EXPAND_ARG4_TYPE)(s), sizeof(s)); | |
332 | ||
333 | /* If an overlong response was received, the data will have been | |
334 | truncated and dn_expand may fail. */ | |
335 | ||
336 | if (rc < 0) | |
337 | { | |
338 | log_write(0, LOG_MAIN, "host name alias list truncated: type=%s " | |
339 | "domain=%s", dns_text_type(type), domain); | |
340 | break; | |
341 | } | |
342 | else yield = string_cat(yield, &size, &ptr, s, Ustrlen(s)); | |
0756eb3c | 343 | } |
7bb56e1f PH |
344 | } /* Loop for list of returned records */ |
345 | } /* Loop for list of domains */ | |
346 | ||
347 | /* Reclaim unused memory */ | |
0756eb3c | 348 | |
7bb56e1f PH |
349 | store_reset(yield + ptr + 1); |
350 | ||
351 | /* If ptr == 0 we have not found anything. Otherwise, insert the terminating | |
352 | zero and return the result. */ | |
353 | ||
c38d6da9 | 354 | if (ptr == 0) return failrc; |
0756eb3c | 355 | yield[ptr] = 0; |
0756eb3c | 356 | *result = yield; |
0756eb3c PH |
357 | return OK; |
358 | } | |
359 | ||
360 | /* End of lookups/dnsdb.c */ |