1 /*************************************************
2 * fakens - A Fake Nameserver Program *
3 *************************************************/
5 /* This program exists to support the testing of DNS handling code in Exim. It
6 avoids the need to install special zones in a real nameserver. When Exim is
7 running in its (new) test harness, DNS lookups are first passed to this program
8 instead of to the real resolver. (With a few exceptions - see the discussion in
9 the test suite's README file.) The program is also passed the name of the Exim
10 spool directory; it expects to find its "zone files" in dnszones relative to
11 exim config_main_directory. Note that there is little checking in this program. The fake
12 zone files are assumed to be syntactically valid.
14 The zones that are handled are found by scanning the dnszones directory. A file
15 whose name is of the form db.ip4.x is a zone file for .x.in-addr.arpa; a file
16 whose name is of the form db.ip6.x is a zone file for .x.ip6.arpa; a file of
17 the form db.anything.else is a zone file for .anything.else. A file of the form
18 qualify.x.y specifies the domain that is used to qualify single-component
19 names, except for the name "dontqualify".
21 The arguments to the program are:
23 the name of the Exim spool directory
24 the domain name that is being sought
25 the DNS record type that is being sought
27 The output from the program is written to stdout. It is supposed to be in
28 exactly the same format as a traditional namserver response (see RFC 1035) so
29 that Exim can process it as normal. At present, no compression is used.
30 Error messages are written to stderr.
32 The return codes from the program are zero for success, and otherwise the
33 values that are set in h_errno after a failing call to the normal resolver:
35 1 HOST_NOT_FOUND host not found (authoritative)
36 2 TRY_AGAIN server failure
37 3 NO_RECOVERY non-recoverable error
38 4 NO_DATA valid name, no data of requested type
40 In a real nameserver, TRY_AGAIN is also used for a non-authoritative not found,
41 but it is not used for that here. There is also one extra return code:
43 5 PASS_ON requests Exim to call res_search()
45 This is used for zones that fakens does not recognize. It is also used if a
46 line in the zone file contains exactly this:
50 and the domain is not found. It converts the the result to PASS_ON instead of
53 Any DNS record line in a zone file can be prefixed with "DELAY=" and
54 a number of milliseconds (followed by one space).
56 Any DNS record line in a zone file can be prefixed with "DNSSEC ";
57 if all the records found by a lookup are marked
58 as such then the response will have the "AD" bit set.
60 Any DNS record line in a zone file can be prefixed with "AA "
61 if all the records found by a lookup are marked
62 as such then the response will have the "AA" bit set.
64 Any DNS record line in a zone file can be prefixed with "TTL=" and
65 a number of seconds (followed by one space).
77 #include <arpa/nameser.h>
78 #include <arpa/inet.h>
79 #include <sys/types.h>
89 typedef unsigned char uschar;
92 #define CCS (const char *)
93 #define US (unsigned char *)
95 #define Ustrcat(s,t) strcat(CS(s),CCS(t))
96 #define Ustrchr(s,n) US strchr(CCS(s),n)
97 #define Ustrcmp(s,t) strcmp(CCS(s),CCS(t))
98 #define Ustrcpy(s,t) strcpy(CS(s),CCS(t))
99 #define Ustrlen(s) (int)strlen(CCS(s))
100 #define Ustrncmp(s,t,n) strncmp(CCS(s),CCS(t),n)
101 #define Ustrncpy(s,t,n) strncpy(CS(s),CCS(t),n)
102 #define Ustrtok(s,t) strtok(CS(s),CCS(t))
104 typedef struct zoneitem {
109 typedef struct tlist {
114 #define DEFAULT_TTL 3600U
116 /* On some (older?) operating systems, the standard ns_t_xxx definitions are
117 not available, and only the older T_xxx ones exist in nameser.h. If ns_t_a is
118 not defined, assume we are in this state. A really old system might not even
119 know about AAAA and SRV at all. */
123 # define ns_t_ns T_NS
124 # define ns_t_cname T_CNAME
125 # define ns_t_soa T_SOA
126 # define ns_t_ptr T_PTR
127 # define ns_t_mx T_MX
128 # define ns_t_txt T_TXT
129 # define ns_t_aaaa T_AAAA
130 # define ns_t_srv T_SRV
131 # define ns_t_tlsa T_TLSA
143 static tlist type_list[] = {
146 { US"CNAME", ns_t_cname },
147 { US"SOA", ns_t_soa },
148 { US"PTR", ns_t_ptr },
150 { US"TXT", ns_t_txt },
151 { US"AAAA", ns_t_aaaa },
152 { US"SRV", ns_t_srv },
153 { US"TLSA", ns_t_tlsa },
159 /*************************************************
160 * Get memory and sprintf into it *
161 *************************************************/
163 /* This is used when building a table of zones and their files.
166 format a format string
169 Returns: pointer to formatted string
173 fcopystring(uschar *format, ...)
178 va_start(ap, format);
179 vsprintf(buffer, CS format, ap);
181 yield = (uschar *)malloc(Ustrlen(buffer) + 1);
182 Ustrcpy(yield, buffer);
187 /*************************************************
188 * Pack name into memory *
189 *************************************************/
191 /* This function packs a domain name into memory according to DNS rules. At
192 present, it doesn't do any compression.
198 Returns: the updated value of pk
202 packname(uschar *name, uschar *pk)
207 while (*p != 0 && *p != '.') p++;
209 memmove(pk, name, p - name);
211 name = (*p == 0)? p : p + 1;
218 bytefield(uschar ** pp, uschar * pk)
223 while (isdigit(*p)) value = value*10 + *p++ - '0';
224 while (isspace(*p)) p++;
231 shortfield(uschar ** pp, uschar * pk)
236 while (isdigit(*p)) value = value*10 + *p++ - '0';
237 while (isspace(*p)) p++;
239 *pk++ = (value >> 8) & 255;
245 longfield(uschar ** pp, uschar * pk)
247 unsigned long value = 0;
250 while (isdigit(*p)) value = value*10 + *p++ - '0';
251 while (isspace(*p)) p++;
253 *pk++ = (value >> 24) & 255;
254 *pk++ = (value >> 16) & 255;
255 *pk++ = (value >> 8) & 255;
262 /*************************************************/
265 milliwait(struct itimerval *itval)
268 sigset_t old_sigmask;
270 if (itval->it_value.tv_usec < 100 && itval->it_value.tv_sec == 0)
272 (void)sigemptyset(&sigmask); /* Empty mask */
273 (void)sigaddset(&sigmask, SIGALRM); /* Add SIGALRM */
274 (void)sigprocmask(SIG_BLOCK, &sigmask, &old_sigmask); /* Block SIGALRM */
275 (void)setitimer(ITIMER_REAL, itval, NULL); /* Start timer */
276 (void)sigfillset(&sigmask); /* All signals */
277 (void)sigdelset(&sigmask, SIGALRM); /* Remove SIGALRM */
278 (void)sigsuspend(&sigmask); /* Until SIGALRM */
279 (void)sigprocmask(SIG_SETMASK, &old_sigmask, NULL); /* Restore mask */
285 struct itimerval itval;
286 itval.it_interval.tv_sec = 0;
287 itval.it_interval.tv_usec = 0;
288 itval.it_value.tv_sec = msec/1000;
289 itval.it_value.tv_usec = (msec % 1000) * 1000;
294 /*************************************************
295 * Scan file for RRs *
296 *************************************************/
298 /* This function scans an open "zone file" for appropriate records, and adds
299 any that are found to the output buffer.
303 zone the current zone name
304 domain the domain we are looking for
305 qtype the type of RR we want
306 qtypelen the length of qtype
307 pkptr points to the output buffer pointer; this is updated
308 countptr points to the record count; this is updated
309 dnssec points to the AD flag indicator; this is updated
310 aa points to the AA flag indicator; this is updated
312 Returns: 0 on success, else HOST_NOT_FOUND or NO_DATA or NO_RECOVERY or
313 PASS_ON - the latter if a "PASS ON NOT FOUND" line is seen
317 find_records(FILE *f, uschar *zone, uschar *domain, uschar *qtype,
318 int qtypelen, uschar **pkptr, int *countptr, BOOL * dnssec, BOOL * aa)
320 int yield = HOST_NOT_FOUND;
321 int domainlen = Ustrlen(domain);
322 BOOL pass_on_not_found = FALSE;
326 uschar rrdomain[256];
327 uschar RRdomain[256];
330 /* Decode the required type */
331 for (typeptr = type_list; typeptr->name != NULL; typeptr++)
332 { if (Ustrcmp(typeptr->name, qtype) == 0) break; }
333 if (typeptr->name == NULL)
335 fprintf(stderr, "fakens: unknown record type %s\n", qtype);
339 rrdomain[0] = 0; /* No previous domain */
340 (void)fseek(f, 0, SEEK_SET); /* Start again at the beginning */
342 if (dnssec) *dnssec = TRUE; /* cancelled by first nonsecure rec found */
343 if (aa) *aa = TRUE; /* cancelled by first non-aa rec found */
347 while (fgets(CS buffer, sizeof(buffer), f) != NULL)
351 BOOL found_cname = FALSE;
353 int tvalue = typeptr->value;
354 int qtlen = qtypelen;
358 uint ttl = DEFAULT_TTL;
361 while (isspace(*p)) p++;
362 if (*p == 0 || *p == ';') continue;
364 if (Ustrncmp(p, US"PASS ON NOT FOUND", 17) == 0)
366 pass_on_not_found = TRUE;
370 ep = buffer + Ustrlen(buffer);
371 while (isspace(ep[-1])) ep--;
377 if (Ustrncmp(p, US"DNSSEC ", 7) == 0) /* tagged as secure */
382 else if (Ustrncmp(p, US"AA ", 3) == 0) /* tagged as authoritive */
387 else if (Ustrncmp(p, US"DELAY=", 6) == 0) /* delay before response */
389 for (p += 6; *p >= '0' && *p <= '9'; p++) delay = delay*10 + *p - '0';
390 if (isspace(*p)) p++;
392 else if (Ustrncmp(p, US"TTL=", 4) == 0) /* TTL for record */
395 for (p += 4; *p >= '0' && *p <= '9'; p++) ttl = ttl*10 + *p - '0';
396 if (isspace(*p)) p++;
402 if (!isspace(*p)) /* new domain name */
404 uschar *pp = rrdomain;
405 uschar *PP = RRdomain;
421 } /* else use previous line's domain name */
423 /* Compare domain names; first check for a wildcard */
425 if (rrdomain[0] == '*')
427 int restlen = Ustrlen(rrdomain) - 1;
428 if (domainlen > restlen &&
429 Ustrcmp(domain + domainlen - restlen, rrdomain + 1) != 0) continue;
432 /* Not a wildcard RR */
434 else if (Ustrcmp(domain, rrdomain) != 0) continue;
436 /* The domain matches */
438 if (yield == HOST_NOT_FOUND) yield = NO_DATA;
440 /* Compare RR types; a CNAME record is always returned */
442 while (isspace(*p)) p++;
444 if (Ustrncmp(p, "CNAME", 5) == 0)
450 else if (Ustrncmp(p, qtype, qtypelen) != 0 || !isspace(p[qtypelen])) continue;
452 /* Found a relevant record */
456 if (dnssec && !rr_sec)
457 *dnssec = FALSE; /* cancel AD return */
460 *aa = FALSE; /* cancel AA return */
463 *countptr = *countptr + 1;
466 while (isspace(*p)) p++;
468 /* For a wildcard record, use the search name; otherwise use the record's
469 name in its original case because it might contain upper case letters. */
471 pk = packname((rrdomain[0] == '*')? domain : RRdomain, pk);
472 *pk++ = (tvalue >> 8) & 255;
473 *pk++ = (tvalue) & 255;
475 *pk++ = 1; /* class = IN */
477 *pk++ = (ttl >>24) & 255;
478 *pk++ = (ttl >>16) & 255;
479 *pk++ = (ttl >> 8) & 255;
482 rdlptr = pk; /* remember rdlength field */
485 /* The rest of the data depends on the type */
492 if (ep[-1] != '.') sprintf(CS ep, "%s.", zone);
493 pk = packname(p, pk); /* primary ns */
494 p = Ustrtok(NULL, " ");
495 pk = packname(p , pk); /* responsible mailbox */
496 *(p += strlen(p)) = ' ';
497 while (isspace(*p)) p++;
498 pk = longfield(&p, pk); /* serial */
499 pk = longfield(&p, pk); /* refresh */
500 pk = longfield(&p, pk); /* retry */
501 pk = longfield(&p, pk); /* expire */
502 pk = longfield(&p, pk); /* minimum */
506 inet_pton(AF_INET, p, pk); /* FIXME: error checking */
511 inet_pton(AF_INET6, p, pk); /* FIXME: error checking */
516 pk = shortfield(&p, pk);
517 if (ep[-1] != '.') sprintf(CS ep, "%s.", zone);
518 pk = packname(p, pk);
523 if (*p == '"') p++; /* Should always be the case */
524 while (*p != 0 && *p != '"') *pk++ = *p++;
529 pk = bytefield(&p, pk); /* usage */
530 pk = bytefield(&p, pk); /* selector */
531 pk = bytefield(&p, pk); /* match type */
534 value = toupper(*p) - (isdigit(*p) ? '0' : '7') << 4;
537 value |= toupper(*p) - (isdigit(*p) ? '0' : '7');
546 for (i = 0; i < 3; i++)
549 while (isdigit(*p)) value = value*10 + *p++ - '0';
550 while (isspace(*p)) p++;
551 *pk++ = (value >> 8) & 255;
560 if (ep[-1] != '.') sprintf(CS ep, "%s.", zone);
561 pk = packname(p, pk);
565 /* Fill in the length, and we are done with this RR */
567 rdlptr[0] = ((pk - rdlptr - 2) >> 8) & 255;
568 rdlptr[1] = (pk -rdlptr - 2) & 255;
572 return (yield == HOST_NOT_FOUND && pass_on_not_found)? PASS_ON : yield;
582 /*************************************************
583 * Special-purpose domains *
584 *************************************************/
587 special_manyhome(uschar * packet, uschar * domain)
589 uschar *pk = packet + 12;
593 memset(packet, 0, 12);
595 for (i = 104; i <= 111; i++) for (j = 0; j <= 255; j++)
597 pk = packname(domain, pk);
598 *pk++ = (ns_t_a >> 8) & 255;
599 *pk++ = (ns_t_a) & 255;
601 *pk++ = 1; /* class = IN */
602 pk += 4; /* TTL field; don't care */
603 rdlptr = pk; /* remember rdlength field */
606 *pk++ = 10; *pk++ = 250; *pk++ = i; *pk++ = j;
608 rdlptr[0] = ((pk - rdlptr - 2) >> 8) & 255;
609 rdlptr[1] = (pk - rdlptr - 2) & 255;
612 packet[6] = (2048 >> 8) & 255;
613 packet[7] = 2048 & 255;
617 (void)fwrite(packet, 1, pk - packet, stdout);
622 special_again(uschar * packet, uschar * domain)
624 int delay = atoi(CCS domain); /* digits at the start of the name */
625 if (delay > 0) sleep(delay);
630 /*************************************************
631 * Entry point and main program *
632 *************************************************/
635 main(int argc, char **argv)
639 int domlen, qtypelen;
645 uschar *qualify = NULL;
647 uschar *zonefile = NULL;
651 uschar packet[2048 * 32 + 32];
652 HEADER *header = (HEADER *)packet;
657 signal(SIGALRM, alarmfn);
661 fprintf(stderr, "fakens: expected 3 arguments, received %d\n", argc-1);
667 (void)sprintf(CS buffer, "%s/dnszones", argv[1]);
669 d = opendir(CCS buffer);
672 fprintf(stderr, "fakens: failed to opendir %s: %s\n", buffer,
677 while ((de = readdir(d)) != NULL)
679 uschar *name = US de->d_name;
680 if (Ustrncmp(name, "qualify.", 8) == 0)
682 qualify = fcopystring(US "%s", name + 7);
685 if (Ustrncmp(name, "db.", 3) != 0) continue;
686 if (Ustrncmp(name + 3, "ip4.", 4) == 0)
687 zones[zonecount].zone = fcopystring(US "%s.in-addr.arpa", name + 6);
688 else if (Ustrncmp(name + 3, "ip6.", 4) == 0)
689 zones[zonecount].zone = fcopystring(US "%s.ip6.arpa", name + 6);
691 zones[zonecount].zone = fcopystring(US "%s", name + 2);
692 zones[zonecount++].zonefile = fcopystring(US "%s", name);
696 /* Get the RR type and upper case it, and check that we recognize it. */
698 Ustrncpy(qtype, argv[3], sizeof(qtype));
699 qtypelen = Ustrlen(qtype);
700 for (p = qtype; *p != 0; p++) *p = toupper(*p);
702 /* Find the domain, lower case it, deal with any specials,
703 check that it is in a zone that we handle,
704 and set up the zone file name. The zone names in the table all start with a
707 domlen = Ustrlen(argv[2]);
708 if (argv[2][domlen-1] == '.') domlen--;
709 Ustrncpy(domain, argv[2], domlen);
711 for (i = 0; i < domlen; i++) domain[i] = tolower(domain[i]);
713 if (Ustrcmp(domain, "manyhome.test.ex") == 0 && Ustrcmp(qtype, "A") == 0)
714 return special_manyhome(packet, domain);
715 else if (domlen >= 14 && Ustrcmp(domain + domlen - 14, "test.again.dns") == 0)
716 return special_again(packet, domain);
717 else if (domlen >= 13 && Ustrcmp(domain + domlen - 13, "test.fail.dns") == 0)
721 if (Ustrchr(domain, '.') == NULL && qualify != NULL &&
722 Ustrcmp(domain, "dontqualify") != 0)
724 Ustrcat(domain, qualify);
725 domlen += Ustrlen(qualify);
728 for (i = 0; i < zonecount; i++)
731 zone = zones[i].zone;
732 zlen = Ustrlen(zone);
733 if (Ustrcmp(domain, zone+1) == 0 || (domlen >= zlen &&
734 Ustrcmp(domain + domlen - zlen, zone) == 0))
736 zonefile = zones[i].zonefile;
741 if (zonefile == NULL)
743 fprintf(stderr, "fakens: query not in faked zone: domain is: %s\n", domain);
747 (void)sprintf(CS buffer, "%s/dnszones/%s", argv[1], zonefile);
749 /* Initialize the start of the response packet. We don't have to fake up
750 everything, because we know that Exim will look only at the answer and
751 additional section parts. */
753 memset(packet, 0, 12);
756 /* Open the zone file. */
758 f = fopen(CS buffer, "r");
761 fprintf(stderr, "fakens: failed to open %s: %s\n", buffer, strerror(errno));
765 /* Find the records we want, and add them to the result. */
768 yield = find_records(f, zone, domain, qtype, qtypelen, &pk, &count, &dnssec, &aa);
769 if (yield == NO_RECOVERY) goto END_OFF;
770 header->ancount = htons(count);
772 /* If the AA bit should be set (as indicated by the AA prefix in the zone file),
773 we are expected to return some records in the authortive section. Bind9: If
774 there is data in the answer section, the authoritive section contains the NS
775 records, otherwise it contains the SOA record. Currently we mimic this
776 behaviour for the first case (there is some answer record).
780 find_records(f, zone, zone[0] == '.' ? zone+1 : zone, US"NS", 2, &pk, &count, NULL, NULL);
781 header->nscount = htons(count - ntohs(header->ancount));
783 /* There is no need to return any additional records because Exim no longer
784 (from release 4.61) makes any use of them. */
793 /* Close the zone file, write the result, and return. */
797 (void)fwrite(packet, 1, pk - packet, stdout);
801 /* vi: aw ai sw=2 sts=2 ts=8 et
803 /* End of fakens.c */