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184e8823 | 1 | /* $Cambridge: exim/src/src/lookups/dnsdb.c,v 1.17 2007/01/08 10:50:19 ph10 Exp $ */ |
0756eb3c PH |
2 | |
3 | /************************************************* | |
4 | * Exim - an Internet mail transport agent * | |
5 | *************************************************/ | |
6 | ||
184e8823 | 7 | /* Copyright (c) University of Cambridge 1995 - 2007 */ |
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", | |
e5a9dba6 | 34 | "csa", |
0756eb3c | 35 | "mx", |
ea3bc19b | 36 | "mxh", |
0756eb3c PH |
37 | "ns", |
38 | "ptr", | |
39 | "srv", | |
33397d19 | 40 | "txt", |
8e669ac1 | 41 | "zns" |
33397d19 | 42 | }; |
0756eb3c PH |
43 | |
44 | static int type_values[] = { | |
45 | T_A, | |
46 | #if HAVE_IPV6 | |
47 | T_AAAA, | |
48 | #ifdef SUPPORT_A6 | |
49 | T_A6, | |
50 | #endif | |
51 | #endif | |
52 | T_CNAME, | |
e5a9dba6 | 53 | T_CSA, /* Private type for "Client SMTP Authorization". */ |
0756eb3c | 54 | T_MX, |
ea3bc19b | 55 | T_MXH, /* Private type for "MX hostnames" */ |
0756eb3c PH |
56 | T_NS, |
57 | T_PTR, | |
58 | T_SRV, | |
33397d19 PH |
59 | T_TXT, |
60 | T_ZNS /* Private type for "zone nameservers" */ | |
61 | }; | |
0756eb3c PH |
62 | |
63 | ||
64 | /************************************************* | |
65 | * Open entry point * | |
66 | *************************************************/ | |
67 | ||
68 | /* See local README for interface description. */ | |
69 | ||
70 | void * | |
71 | dnsdb_open(uschar *filename, uschar **errmsg) | |
72 | { | |
73 | filename = filename; /* Keep picky compilers happy */ | |
74 | errmsg = errmsg; /* Ditto */ | |
75 | return (void *)(-1); /* Any non-0 value */ | |
76 | } | |
77 | ||
78 | ||
79 | ||
80 | /************************************************* | |
81 | * Find entry point for dnsdb * | |
82 | *************************************************/ | |
83 | ||
7bb56e1f PH |
84 | /* See local README for interface description. The query in the "keystring" may |
85 | consist of a number of parts. | |
86 | ||
8e669ac1 PH |
87 | (a) If the first significant character is '>' then the next character is the |
88 | separator character that is used when multiple records are found. The default | |
7bb56e1f PH |
89 | separator is newline. |
90 | ||
ff4dbb19 PH |
91 | (b) If the next sequence of characters is 'defer_FOO' followed by a comma, |
92 | the defer behaviour is set to FOO. The possible behaviours are: 'strict', where | |
93 | any defer causes the whole lookup to defer; 'lax', where a defer causes the | |
94 | whole lookup to defer only if none of the DNS queries succeeds; and 'never', | |
95 | where all defers are as if the lookup failed. The default is 'lax'. | |
96 | ||
8e669ac1 PH |
97 | (c) If the next sequence of characters is a sequence of letters and digits |
98 | followed by '=', it is interpreted as the name of the DNS record type. The | |
ff4dbb19 | 99 | default is "TXT". |
7bb56e1f | 100 | |
8e669ac1 PH |
101 | (d) Then there follows list of domain names. This is a generalized Exim list, |
102 | which may start with '<' in order to set a specific separator. The default | |
7bb56e1f | 103 | separator, as always, is colon. */ |
0756eb3c PH |
104 | |
105 | int | |
106 | dnsdb_find(void *handle, uschar *filename, uschar *keystring, int length, | |
107 | uschar **result, uschar **errmsg, BOOL *do_cache) | |
108 | { | |
109 | int rc; | |
110 | int size = 256; | |
111 | int ptr = 0; | |
7bb56e1f | 112 | int sep = 0; |
ff4dbb19 | 113 | int defer_mode = PASS; |
0756eb3c | 114 | int type = T_TXT; |
c38d6da9 | 115 | int failrc = FAIL; |
7bb56e1f | 116 | uschar *outsep = US"\n"; |
e5a9dba6 | 117 | uschar *equals, *domain, *found; |
0756eb3c PH |
118 | uschar buffer[256]; |
119 | ||
120 | /* Because we're the working in the search pool, we try to reclaim as much | |
121 | store as possible later, so we preallocate the result here */ | |
122 | ||
123 | uschar *yield = store_get(size); | |
124 | ||
125 | dns_record *rr; | |
126 | dns_answer dnsa; | |
127 | dns_scan dnss; | |
128 | ||
129 | handle = handle; /* Keep picky compilers happy */ | |
130 | filename = filename; | |
131 | length = length; | |
132 | do_cache = do_cache; | |
133 | ||
7bb56e1f | 134 | /* If the string starts with '>' we change the output separator */ |
0756eb3c | 135 | |
7bb56e1f PH |
136 | while (isspace(*keystring)) keystring++; |
137 | if (*keystring == '>') | |
0756eb3c | 138 | { |
7bb56e1f | 139 | outsep = keystring + 1; |
8e669ac1 | 140 | keystring += 2; |
7bb56e1f | 141 | while (isspace(*keystring)) keystring++; |
8e669ac1 | 142 | } |
7bb56e1f | 143 | |
ff4dbb19 PH |
144 | /* Check for a defer behaviour keyword. */ |
145 | ||
146 | if (strncmpic(keystring, US"defer_", 6) == 0) | |
147 | { | |
148 | keystring += 6; | |
149 | if (strncmpic(keystring, US"strict", 6) == 0) | |
150 | { | |
151 | defer_mode = DEFER; | |
152 | keystring += 6; | |
153 | } | |
154 | else if (strncmpic(keystring, US"lax", 3) == 0) | |
155 | { | |
156 | defer_mode = PASS; | |
157 | keystring += 3; | |
158 | } | |
159 | else if (strncmpic(keystring, US"never", 5) == 0) | |
160 | { | |
161 | defer_mode = OK; | |
162 | keystring += 5; | |
163 | } | |
164 | else | |
165 | { | |
166 | *errmsg = US"unsupported dnsdb defer behaviour"; | |
167 | return DEFER; | |
168 | } | |
169 | while (isspace(*keystring)) keystring++; | |
170 | if (*keystring++ != ',') | |
171 | { | |
172 | *errmsg = US"dnsdb defer behaviour syntax error"; | |
173 | return DEFER; | |
174 | } | |
175 | while (isspace(*keystring)) keystring++; | |
176 | } | |
177 | ||
7bb56e1f PH |
178 | /* If the keystring contains an = this must be preceded by a valid type name. */ |
179 | ||
180 | if ((equals = Ustrchr(keystring, '=')) != NULL) | |
181 | { | |
182 | int i, len; | |
183 | uschar *tend = equals; | |
8e669ac1 PH |
184 | |
185 | while (tend > keystring && isspace(tend[-1])) tend--; | |
186 | len = tend - keystring; | |
187 | ||
0756eb3c PH |
188 | for (i = 0; i < sizeof(type_names)/sizeof(uschar *); i++) |
189 | { | |
190 | if (len == Ustrlen(type_names[i]) && | |
191 | strncmpic(keystring, US type_names[i], len) == 0) | |
192 | { | |
193 | type = type_values[i]; | |
194 | break; | |
195 | } | |
196 | } | |
8e669ac1 | 197 | |
0756eb3c PH |
198 | if (i >= sizeof(type_names)/sizeof(uschar *)) |
199 | { | |
200 | *errmsg = US"unsupported DNS record type"; | |
201 | return DEFER; | |
202 | } | |
8e669ac1 | 203 | |
7bb56e1f PH |
204 | keystring = equals + 1; |
205 | while (isspace(*keystring)) keystring++; | |
0756eb3c | 206 | } |
8e669ac1 | 207 | |
7bb56e1f | 208 | /* Initialize the resolver in case this is the first time it has been used. */ |
0756eb3c PH |
209 | |
210 | dns_init(FALSE, FALSE); | |
0756eb3c | 211 | |
8e669ac1 PH |
212 | /* The remainder of the string must be a list of domains. As long as the lookup |
213 | for at least one of them succeeds, we return success. Failure means that none | |
214 | of them were found. | |
0756eb3c | 215 | |
8e669ac1 PH |
216 | The original implementation did not support a list of domains. Adding the list |
217 | feature is compatible, except in one case: when PTR records are being looked up | |
218 | for a single IPv6 address. Fortunately, we can hack in a compatibility feature | |
219 | here: If the type is PTR and no list separator is specified, and the entire | |
220 | remaining string is valid as an IP address, set an impossible separator so that | |
7bb56e1f | 221 | it is treated as one item. */ |
33397d19 | 222 | |
7bb56e1f | 223 | if (type == T_PTR && keystring[0] != '<' && |
7e66e54d | 224 | string_is_ip_address(keystring, NULL) != 0) |
7bb56e1f | 225 | sep = -1; |
0756eb3c | 226 | |
7bb56e1f | 227 | /* Now scan the list and do a lookup for each item */ |
0756eb3c | 228 | |
8e669ac1 | 229 | while ((domain = string_nextinlist(&keystring, &sep, buffer, sizeof(buffer))) |
7bb56e1f | 230 | != NULL) |
8e669ac1 | 231 | { |
7bb56e1f | 232 | uschar rbuffer[256]; |
e5a9dba6 PH |
233 | int searchtype = (type == T_CSA)? T_SRV : /* record type we want */ |
234 | (type == T_MXH)? T_MX : | |
235 | (type == T_ZNS)? T_NS : type; | |
236 | ||
237 | /* If the type is PTR or CSA, we have to construct the relevant magic lookup | |
238 | key if the original is an IP address (some experimental protocols are using | |
239 | PTR records for different purposes where the key string is a host name, and | |
240 | Exim's extended CSA can be keyed by domains or IP addresses). This code for | |
241 | doing the reversal is now in a separate function. */ | |
242 | ||
243 | if ((type == T_PTR || type == T_CSA) && | |
7e66e54d | 244 | string_is_ip_address(domain, NULL) != 0) |
0756eb3c | 245 | { |
7bb56e1f PH |
246 | dns_build_reverse(domain, rbuffer); |
247 | domain = rbuffer; | |
0756eb3c | 248 | } |
8e669ac1 | 249 | |
7bb56e1f | 250 | DEBUG(D_lookup) debug_printf("dnsdb key: %s\n", domain); |
8e669ac1 | 251 | |
28e6ef29 TF |
252 | /* Do the lookup and sort out the result. There are three special types that |
253 | are handled specially: T_CSA, T_ZNS and T_MXH. The former two are handled in | |
254 | a special lookup function so that the facility could be used from other | |
255 | parts of the Exim code. The latter affects only what happens later on in | |
256 | this function, but for tidiness it is handled in a similar way. If the | |
257 | lookup fails, continue with the next domain. In the case of DEFER, adjust | |
258 | the final "nothing found" result, but carry on to the next domain. */ | |
8e669ac1 | 259 | |
e5a9dba6 PH |
260 | found = domain; |
261 | rc = dns_special_lookup(&dnsa, domain, type, &found); | |
8e669ac1 | 262 | |
7bb56e1f | 263 | if (rc == DNS_NOMATCH || rc == DNS_NODATA) continue; |
c38d6da9 PH |
264 | if (rc != DNS_SUCCEED) |
265 | { | |
ff4dbb19 PH |
266 | if (defer_mode == DEFER) return DEFER; /* always defer */ |
267 | else if (defer_mode == PASS) failrc = DEFER; /* defer only if all do */ | |
268 | continue; /* treat defer as fail */ | |
c38d6da9 | 269 | } |
8e669ac1 | 270 | |
ea3bc19b PH |
271 | /* Search the returned records */ |
272 | ||
7bb56e1f PH |
273 | for (rr = dns_next_rr(&dnsa, &dnss, RESET_ANSWERS); |
274 | rr != NULL; | |
275 | rr = dns_next_rr(&dnsa, &dnss, RESET_NEXT)) | |
0756eb3c | 276 | { |
ea3bc19b | 277 | if (rr->type != searchtype) continue; |
8e669ac1 PH |
278 | |
279 | /* There may be several addresses from an A6 record. Put the configured | |
280 | separator between them, just as for between several records. However, A6 | |
7bb56e1f | 281 | support is not normally configured these days. */ |
8e669ac1 | 282 | |
7bb56e1f PH |
283 | if (type == T_A || |
284 | #ifdef SUPPORT_A6 | |
285 | type == T_A6 || | |
286 | #endif | |
287 | type == T_AAAA) | |
0756eb3c | 288 | { |
7bb56e1f PH |
289 | dns_address *da; |
290 | for (da = dns_address_from_rr(&dnsa, rr); da != NULL; da = da->next) | |
291 | { | |
292 | if (ptr != 0) yield = string_cat(yield, &size, &ptr, outsep, 1); | |
8e669ac1 | 293 | yield = string_cat(yield, &size, &ptr, da->address, |
7bb56e1f PH |
294 | Ustrlen(da->address)); |
295 | } | |
296 | continue; | |
0756eb3c | 297 | } |
8e669ac1 PH |
298 | |
299 | /* Other kinds of record just have one piece of data each, but there may be | |
7bb56e1f | 300 | several of them, of course. */ |
8e669ac1 | 301 | |
7bb56e1f | 302 | if (ptr != 0) yield = string_cat(yield, &size, &ptr, outsep, 1); |
8e669ac1 | 303 | |
7bb56e1f | 304 | if (type == T_TXT) |
0756eb3c | 305 | { |
7bb56e1f PH |
306 | yield = string_cat(yield, &size, &ptr, (uschar *)(rr->data+1), |
307 | (rr->data)[0]); | |
0756eb3c | 308 | } |
e5a9dba6 | 309 | else /* T_CNAME, T_CSA, T_MX, T_MXH, T_NS, T_PTR, T_SRV */ |
0756eb3c | 310 | { |
e5a9dba6 | 311 | int priority, weight, port; |
7bb56e1f PH |
312 | uschar s[264]; |
313 | uschar *p = (uschar *)(rr->data); | |
8e669ac1 | 314 | |
ea3bc19b PH |
315 | if (type == T_MXH) |
316 | { | |
317 | /* mxh ignores the priority number and includes only the hostnames */ | |
e5a9dba6 | 318 | GETSHORT(priority, p); |
ea3bc19b PH |
319 | } |
320 | else if (type == T_MX) | |
7bb56e1f | 321 | { |
e5a9dba6 PH |
322 | GETSHORT(priority, p); |
323 | sprintf(CS s, "%d ", priority); | |
7bb56e1f PH |
324 | yield = string_cat(yield, &size, &ptr, s, Ustrlen(s)); |
325 | } | |
326 | else if (type == T_SRV) | |
327 | { | |
e5a9dba6 | 328 | GETSHORT(priority, p); |
7bb56e1f PH |
329 | GETSHORT(weight, p); |
330 | GETSHORT(port, p); | |
e5a9dba6 | 331 | sprintf(CS s, "%d %d %d ", priority, weight, port); |
7bb56e1f PH |
332 | yield = string_cat(yield, &size, &ptr, s, Ustrlen(s)); |
333 | } | |
e5a9dba6 PH |
334 | else if (type == T_CSA) |
335 | { | |
336 | /* See acl_verify_csa() for more comments about CSA. */ | |
337 | ||
338 | GETSHORT(priority, p); | |
339 | GETSHORT(weight, p); | |
340 | GETSHORT(port, p); | |
341 | ||
342 | if (priority != 1) continue; /* CSA version must be 1 */ | |
343 | ||
344 | /* If the CSA record we found is not the one we asked for, analyse | |
345 | the subdomain assertions in the port field, else analyse the direct | |
346 | authorization status in the weight field. */ | |
347 | ||
348 | if (found != domain) | |
349 | { | |
350 | if (port & 1) *s = 'X'; /* explicit authorization required */ | |
351 | else *s = '?'; /* no subdomain assertions here */ | |
352 | } | |
353 | else | |
354 | { | |
355 | if (weight < 2) *s = 'N'; /* not authorized */ | |
356 | else if (weight == 2) *s = 'Y'; /* authorized */ | |
357 | else if (weight == 3) *s = '?'; /* unauthorizable */ | |
358 | else continue; /* invalid */ | |
359 | } | |
360 | ||
361 | s[1] = ' '; | |
362 | yield = string_cat(yield, &size, &ptr, s, 2); | |
363 | } | |
364 | ||
365 | /* GETSHORT() has advanced the pointer to the target domain. */ | |
8e669ac1 | 366 | |
7bb56e1f PH |
367 | rc = dn_expand(dnsa.answer, dnsa.answer + dnsa.answerlen, p, |
368 | (DN_EXPAND_ARG4_TYPE)(s), sizeof(s)); | |
8e669ac1 | 369 | |
7bb56e1f PH |
370 | /* If an overlong response was received, the data will have been |
371 | truncated and dn_expand may fail. */ | |
8e669ac1 | 372 | |
7bb56e1f PH |
373 | if (rc < 0) |
374 | { | |
375 | log_write(0, LOG_MAIN, "host name alias list truncated: type=%s " | |
376 | "domain=%s", dns_text_type(type), domain); | |
377 | break; | |
378 | } | |
379 | else yield = string_cat(yield, &size, &ptr, s, Ustrlen(s)); | |
0756eb3c | 380 | } |
7bb56e1f PH |
381 | } /* Loop for list of returned records */ |
382 | } /* Loop for list of domains */ | |
383 | ||
384 | /* Reclaim unused memory */ | |
0756eb3c | 385 | |
7bb56e1f PH |
386 | store_reset(yield + ptr + 1); |
387 | ||
8e669ac1 | 388 | /* If ptr == 0 we have not found anything. Otherwise, insert the terminating |
7bb56e1f PH |
389 | zero and return the result. */ |
390 | ||
c38d6da9 | 391 | if (ptr == 0) return failrc; |
0756eb3c | 392 | yield[ptr] = 0; |
0756eb3c | 393 | *result = yield; |
0756eb3c PH |
394 | return OK; |
395 | } | |
396 | ||
397 | /* End of lookups/dnsdb.c */ |