/************************************************* * fakens - A Fake Nameserver Program * *************************************************/ /* This program exists to support the testing of DNS handling code in Exim. It avoids the need to install special zones in a real nameserver. When Exim is running in its (new) test harness, DNS lookups are first passed to this program instead of to the real resolver. (With a few exceptions - see the discussion in the test suite's README file.) The program is also passed the name of the Exim spool directory; it expects to find its "zone files" in dnszones relative to exim config_main_directory. Note that there is little checking in this program. The fake zone files are assumed to be syntactically valid. The zones that are handled are found by scanning the dnszones directory. A file whose name is of the form db.ip4.x is a zone file for .x.in-addr.arpa; a file whose name is of the form db.ip6.x is a zone file for .x.ip6.arpa; a file of the form db.anything.else is a zone file for .anything.else. A file of the form qualify.x.y specifies the domain that is used to qualify single-component names, except for the name "dontqualify". The arguments to the program are: the name of the Exim spool directory the domain name that is being sought the DNS record type that is being sought The output from the program is written to stdout. It is supposed to be in exactly the same format as a traditional namserver response (see RFC 1035) so that Exim can process it as normal. At present, no compression is used. Error messages are written to stderr. The return codes from the program are zero for success, and otherwise the values that are set in h_errno after a failing call to the normal resolver: 1 HOST_NOT_FOUND host not found (authoritative) 2 TRY_AGAIN server failure 3 NO_RECOVERY non-recoverable error 4 NO_DATA valid name, no data of requested type In a real nameserver, TRY_AGAIN is also used for a non-authoritative not found, but it is not used for that here. There is also one extra return code: 5 PASS_ON requests Exim to call res_search() This is used for zones that fakens does not recognize. It is also used if a line in the zone file contains exactly this: PASS ON NOT FOUND and the domain is not found. It converts the the result to PASS_ON instead of HOST_NOT_FOUND. Any DNS record line in a zone file can be prefixed with "DELAY=" and a number of milliseconds (followed by one space). Any DNS record line in a zone file can be prefixed with "DNSSEC "; if all the records found by a lookup are marked as such then the response will have the "AD" bit set. Any DNS record line in a zone file can be prefixed with "AA " if all the records found by a lookup are marked as such then the response will have the "AA" bit set. */ #include #include #include #include #include #include #include #include #include #include #include #include #define FALSE 0 #define TRUE 1 #define PASS_ON 5 typedef int BOOL; typedef unsigned char uschar; #define CS (char *) #define CCS (const char *) #define US (unsigned char *) #define Ustrcat(s,t) strcat(CS(s),CCS(t)) #define Ustrchr(s,n) US strchr(CCS(s),n) #define Ustrcmp(s,t) strcmp(CCS(s),CCS(t)) #define Ustrcpy(s,t) strcpy(CS(s),CCS(t)) #define Ustrlen(s) (int)strlen(CCS(s)) #define Ustrncmp(s,t,n) strncmp(CCS(s),CCS(t),n) #define Ustrncpy(s,t,n) strncpy(CS(s),CCS(t),n) typedef struct zoneitem { uschar *zone; uschar *zonefile; } zoneitem; typedef struct tlist { uschar *name; int value; } tlist; /* On some (older?) operating systems, the standard ns_t_xxx definitions are not available, and only the older T_xxx ones exist in nameser.h. If ns_t_a is not defined, assume we are in this state. A really old system might not even know about AAAA and SRV at all. */ #ifndef ns_t_a # define ns_t_a T_A # define ns_t_ns T_NS # define ns_t_cname T_CNAME # define ns_t_soa T_SOA # define ns_t_ptr T_PTR # define ns_t_mx T_MX # define ns_t_txt T_TXT # define ns_t_aaaa T_AAAA # define ns_t_srv T_SRV # define ns_t_tlsa T_TLSA # ifndef T_AAAA # define T_AAAA 28 # endif # ifndef T_SRV # define T_SRV 33 # endif # ifndef T_TLSA # define T_TLSA 52 # endif #endif static tlist type_list[] = { { US"A", ns_t_a }, { US"NS", ns_t_ns }, { US"CNAME", ns_t_cname }, { US"SOA", ns_t_soa }, { US"PTR", ns_t_ptr }, { US"MX", ns_t_mx }, { US"TXT", ns_t_txt }, { US"AAAA", ns_t_aaaa }, { US"SRV", ns_t_srv }, { US"TLSA", ns_t_tlsa }, { NULL, 0 } }; /************************************************* * Get memory and sprintf into it * *************************************************/ /* This is used when building a table of zones and their files. Arguments: format a format string ... arguments Returns: pointer to formatted string */ static uschar * fcopystring(uschar *format, ...) { uschar *yield; char buffer[256]; va_list ap; va_start(ap, format); vsprintf(buffer, CS format, ap); va_end(ap); yield = (uschar *)malloc(Ustrlen(buffer) + 1); Ustrcpy(yield, buffer); return yield; } /************************************************* * Pack name into memory * *************************************************/ /* This function packs a domain name into memory according to DNS rules. At present, it doesn't do any compression. Arguments: name the name pk where to put it Returns: the updated value of pk */ static uschar * packname(uschar *name, uschar *pk) { while (*name != 0) { uschar *p = name; while (*p != 0 && *p != '.') p++; *pk++ = (p - name); memmove(pk, name, p - name); pk += p - name; name = (*p == 0)? p : p + 1; } *pk++ = 0; return pk; } uschar * bytefield(uschar ** pp, uschar * pk) { unsigned value = 0; uschar * p = *pp; while (isdigit(*p)) value = value*10 + *p++ - '0'; while (isspace(*p)) p++; *pp = p; *pk++ = value & 255; return pk; } uschar * shortfield(uschar ** pp, uschar * pk) { unsigned value = 0; uschar * p = *pp; while (isdigit(*p)) value = value*10 + *p++ - '0'; while (isspace(*p)) p++; *pp = p; *pk++ = (value >> 8) & 255; *pk++ = value & 255; return pk; } uschar * longfield(uschar ** pp, uschar * pk) { unsigned long value = 0; uschar * p = *pp; while (isdigit(*p)) value = value*10 + *p++ - '0'; while (isspace(*p)) p++; *pp = p; *pk++ = (value >> 24) & 255; *pk++ = (value >> 16) & 255; *pk++ = (value >> 8) & 255; *pk++ = value & 255; return pk; } /*************************************************/ static void milliwait(struct itimerval *itval) { sigset_t sigmask; sigset_t old_sigmask; if (itval->it_value.tv_usec < 100 && itval->it_value.tv_sec == 0) return; (void)sigemptyset(&sigmask); /* Empty mask */ (void)sigaddset(&sigmask, SIGALRM); /* Add SIGALRM */ (void)sigprocmask(SIG_BLOCK, &sigmask, &old_sigmask); /* Block SIGALRM */ (void)setitimer(ITIMER_REAL, itval, NULL); /* Start timer */ (void)sigfillset(&sigmask); /* All signals */ (void)sigdelset(&sigmask, SIGALRM); /* Remove SIGALRM */ (void)sigsuspend(&sigmask); /* Until SIGALRM */ (void)sigprocmask(SIG_SETMASK, &old_sigmask, NULL); /* Restore mask */ } static void millisleep(int msec) { struct itimerval itval; itval.it_interval.tv_sec = 0; itval.it_interval.tv_usec = 0; itval.it_value.tv_sec = msec/1000; itval.it_value.tv_usec = (msec % 1000) * 1000; milliwait(&itval); } /************************************************* * Scan file for RRs * *************************************************/ /* This function scans an open "zone file" for appropriate records, and adds any that are found to the output buffer. Arguments: f the input FILE zone the current zone name domain the domain we are looking for qtype the type of RR we want qtypelen the length of qtype pkptr points to the output buffer pointer; this is updated countptr points to the record count; this is updated dnssec points to the AD flag indicator; this is updated aa points to the AA flag indicator; this is updated Returns: 0 on success, else HOST_NOT_FOUND or NO_DATA or NO_RECOVERY or PASS_ON - the latter if a "PASS ON NOT FOUND" line is seen */ static int find_records(FILE *f, uschar *zone, uschar *domain, uschar *qtype, int qtypelen, uschar **pkptr, int *countptr, BOOL * dnssec, BOOL * aa) { int yield = HOST_NOT_FOUND; int domainlen = Ustrlen(domain); BOOL pass_on_not_found = FALSE; tlist *typeptr; uschar *pk = *pkptr; uschar buffer[256]; uschar rrdomain[256]; uschar RRdomain[256]; /* Decode the required type */ for (typeptr = type_list; typeptr->name != NULL; typeptr++) { if (Ustrcmp(typeptr->name, qtype) == 0) break; } if (typeptr->name == NULL) { fprintf(stderr, "fakens: unknown record type %s\n", qtype); return NO_RECOVERY; } rrdomain[0] = 0; /* No previous domain */ (void)fseek(f, 0, SEEK_SET); /* Start again at the beginning */ if (dnssec) *dnssec = TRUE; /* cancelled by first nonsecure rec found */ if (aa) *aa = TRUE; /* cancelled by first non-aa rec found */ /* Scan for RRs */ while (fgets(CS buffer, sizeof(buffer), f) != NULL) { uschar *rdlptr; uschar *p, *ep, *pp; BOOL found_cname = FALSE; int i, value; int tvalue = typeptr->value; int qtlen = qtypelen; BOOL rr_sec = FALSE; BOOL rr_aa = FALSE; int delay = 0; p = buffer; while (isspace(*p)) p++; if (*p == 0 || *p == ';') continue; if (Ustrncmp(p, US"PASS ON NOT FOUND", 17) == 0) { pass_on_not_found = TRUE; continue; } ep = buffer + Ustrlen(buffer); while (isspace(ep[-1])) ep--; *ep = 0; p = buffer; for (;;) { if (Ustrncmp(p, US"DNSSEC ", 7) == 0) /* tagged as secure */ { rr_sec = TRUE; p += 7; } else if (Ustrncmp(p, US"AA ", 3) == 0) /* tagged as authoritive */ { rr_aa = TRUE; p += 3; } else if (Ustrncmp(p, US"DELAY=", 6) == 0) /* delay before response */ { for (p += 6; *p >= '0' && *p <= '9'; p++) delay = delay*10 + *p - '0'; if (isspace(*p)) p++; } else break; } if (!isspace(*p)) /* new domain name */ { uschar *pp = rrdomain; uschar *PP = RRdomain; while (!isspace(*p)) { *pp++ = tolower(*p); *PP++ = *p++; } if (pp[-1] != '.') { Ustrcpy(pp, zone); Ustrcpy(PP, zone); } else { pp[-1] = 0; PP[-1] = 0; } } /* else use previous line's domain name */ /* Compare domain names; first check for a wildcard */ if (rrdomain[0] == '*') { int restlen = Ustrlen(rrdomain) - 1; if (domainlen > restlen && Ustrcmp(domain + domainlen - restlen, rrdomain + 1) != 0) continue; } /* Not a wildcard RR */ else if (Ustrcmp(domain, rrdomain) != 0) continue; /* The domain matches */ if (yield == HOST_NOT_FOUND) yield = NO_DATA; /* Compare RR types; a CNAME record is always returned */ while (isspace(*p)) p++; if (Ustrncmp(p, "CNAME", 5) == 0) { tvalue = ns_t_cname; qtlen = 5; found_cname = TRUE; } else if (Ustrncmp(p, qtype, qtypelen) != 0 || !isspace(p[qtypelen])) continue; /* Found a relevant record */ if (delay) millisleep(delay); if (dnssec && !rr_sec) *dnssec = FALSE; /* cancel AD return */ if (aa && !rr_aa) *aa = FALSE; /* cancel AA return */ yield = 0; *countptr = *countptr + 1; p += qtlen; while (isspace(*p)) p++; /* For a wildcard record, use the search name; otherwise use the record's name in its original case because it might contain upper case letters. */ pk = packname((rrdomain[0] == '*')? domain : RRdomain, pk); *pk++ = (tvalue >> 8) & 255; *pk++ = (tvalue) & 255; *pk++ = 0; *pk++ = 1; /* class = IN */ pk += 4; /* TTL field; don't care */ rdlptr = pk; /* remember rdlength field */ pk += 2; /* The rest of the data depends on the type */ switch (tvalue) { case ns_t_soa: p = strtok(p, " "); ep = p + strlen(p); if (ep[-1] != '.') sprintf(CS ep, "%s.", zone); pk = packname(p, pk); /* primary ns */ p = strtok(NULL, " "); pk = packname(p , pk); /* responsible mailbox */ *(p += strlen(p)) = ' '; while (isspace(*p)) p++; pk = longfield(&p, pk); /* serial */ pk = longfield(&p, pk); /* refresh */ pk = longfield(&p, pk); /* retry */ pk = longfield(&p, pk); /* expire */ pk = longfield(&p, pk); /* minimum */ break; case ns_t_a: for (i = 0; i < 4; i++) { value = 0; while (isdigit(*p)) value = value*10 + *p++ - '0'; *pk++ = value; p++; } break; /* The only occurrence of a double colon is for ::1 */ case ns_t_aaaa: if (Ustrcmp(p, "::1") == 0) { memset(pk, 0, 15); pk += 15; *pk++ = 1; } else for (i = 0; i < 8; i++) { value = 0; while (isxdigit(*p)) { value = value * 16 + toupper(*p) - (isdigit(*p)? '0' : '7'); p++; } *pk++ = (value >> 8) & 255; *pk++ = value & 255; p++; } break; case ns_t_mx: pk = shortfield(&p, pk); if (ep[-1] != '.') sprintf(CS ep, "%s.", zone); pk = packname(p, pk); break; case ns_t_txt: pp = pk++; if (*p == '"') p++; /* Should always be the case */ while (*p != 0 && *p != '"') *pk++ = *p++; *pp = pk - pp - 1; break; case ns_t_tlsa: pk = bytefield(&p, pk); /* usage */ pk = bytefield(&p, pk); /* selector */ pk = bytefield(&p, pk); /* match type */ while (isxdigit(*p)) { value = toupper(*p) - (isdigit(*p) ? '0' : '7') << 4; if (isxdigit(*++p)) { value |= toupper(*p) - (isdigit(*p) ? '0' : '7'); p++; } *pk++ = value & 255; } break; case ns_t_srv: for (i = 0; i < 3; i++) { value = 0; while (isdigit(*p)) value = value*10 + *p++ - '0'; while (isspace(*p)) p++; *pk++ = (value >> 8) & 255; *pk++ = value & 255; } /* Fall through */ case ns_t_cname: case ns_t_ns: case ns_t_ptr: if (ep[-1] != '.') sprintf(CS ep, "%s.", zone); pk = packname(p, pk); break; } /* Fill in the length, and we are done with this RR */ rdlptr[0] = ((pk - rdlptr - 2) >> 8) & 255; rdlptr[1] = (pk -rdlptr - 2) & 255; } *pkptr = pk; return (yield == HOST_NOT_FOUND && pass_on_not_found)? PASS_ON : yield; } static void alarmfn(int sig) { } /************************************************* * Special-purpose domains * *************************************************/ static int special_manyhome(uschar * packet, uschar * domain) { uschar *pk = packet + 12; uschar *rdlptr; int i, j; memset(packet, 0, 12); for (i = 104; i <= 111; i++) for (j = 0; j <= 255; j++) { pk = packname(domain, pk); *pk++ = (ns_t_a >> 8) & 255; *pk++ = (ns_t_a) & 255; *pk++ = 0; *pk++ = 1; /* class = IN */ pk += 4; /* TTL field; don't care */ rdlptr = pk; /* remember rdlength field */ pk += 2; *pk++ = 10; *pk++ = 250; *pk++ = i; *pk++ = j; rdlptr[0] = ((pk - rdlptr - 2) >> 8) & 255; rdlptr[1] = (pk - rdlptr - 2) & 255; } packet[6] = (2048 >> 8) & 255; packet[7] = 2048 & 255; packet[10] = 0; packet[11] = 0; (void)fwrite(packet, 1, pk - packet, stdout); return 0; } static int special_again(uschar * packet, uschar * domain) { int delay = atoi(CCS domain); /* digits at the start of the name */ if (delay > 0) sleep(delay); return TRY_AGAIN; } /************************************************* * Entry point and main program * *************************************************/ int main(int argc, char **argv) { FILE *f; DIR *d; int domlen, qtypelen; int yield, count; int i; int zonecount = 0; struct dirent *de; zoneitem zones[32]; uschar *qualify = NULL; uschar *p, *zone; uschar *zonefile = NULL; uschar domain[256]; uschar buffer[256]; uschar qtype[12]; uschar packet[2048 * 32 + 32]; HEADER *header = (HEADER *)packet; uschar *pk = packet; BOOL dnssec; BOOL aa; signal(SIGALRM, alarmfn); if (argc != 4) { fprintf(stderr, "fakens: expected 3 arguments, received %d\n", argc-1); return NO_RECOVERY; } /* Find the zones */ (void)sprintf(CS buffer, "%s/dnszones", argv[1]); d = opendir(CCS buffer); if (d == NULL) { fprintf(stderr, "fakens: failed to opendir %s: %s\n", buffer, strerror(errno)); return NO_RECOVERY; } while ((de = readdir(d)) != NULL) { uschar *name = US de->d_name; if (Ustrncmp(name, "qualify.", 8) == 0) { qualify = fcopystring(US "%s", name + 7); continue; } if (Ustrncmp(name, "db.", 3) != 0) continue; if (Ustrncmp(name + 3, "ip4.", 4) == 0) zones[zonecount].zone = fcopystring(US "%s.in-addr.arpa", name + 6); else if (Ustrncmp(name + 3, "ip6.", 4) == 0) zones[zonecount].zone = fcopystring(US "%s.ip6.arpa", name + 6); else zones[zonecount].zone = fcopystring(US "%s", name + 2); zones[zonecount++].zonefile = fcopystring(US "%s", name); } (void)closedir(d); /* Get the RR type and upper case it, and check that we recognize it. */ Ustrncpy(qtype, argv[3], sizeof(qtype)); qtypelen = Ustrlen(qtype); for (p = qtype; *p != 0; p++) *p = toupper(*p); /* Find the domain, lower case it, deal with any specials, check that it is in a zone that we handle, and set up the zone file name. The zone names in the table all start with a dot. */ domlen = Ustrlen(argv[2]); if (argv[2][domlen-1] == '.') domlen--; Ustrncpy(domain, argv[2], domlen); domain[domlen] = 0; for (i = 0; i < domlen; i++) domain[i] = tolower(domain[i]); if (Ustrcmp(domain, "manyhome.test.ex") == 0 && Ustrcmp(qtype, "A") == 0) return special_manyhome(packet, domain); else if (domlen >= 14 && Ustrcmp(domain + domlen - 14, "test.again.dns") == 0) return special_again(packet, domain); else if (domlen >= 13 && Ustrcmp(domain + domlen - 13, "test.fail.dns") == 0) return NO_RECOVERY; if (Ustrchr(domain, '.') == NULL && qualify != NULL && Ustrcmp(domain, "dontqualify") != 0) { Ustrcat(domain, qualify); domlen += Ustrlen(qualify); } for (i = 0; i < zonecount; i++) { int zlen; zone = zones[i].zone; zlen = Ustrlen(zone); if (Ustrcmp(domain, zone+1) == 0 || (domlen >= zlen && Ustrcmp(domain + domlen - zlen, zone) == 0)) { zonefile = zones[i].zonefile; break; } } if (zonefile == NULL) { fprintf(stderr, "fakens: query not in faked zone: domain is: %s\n", domain); return PASS_ON; } (void)sprintf(CS buffer, "%s/dnszones/%s", argv[1], zonefile); /* Initialize the start of the response packet. We don't have to fake up everything, because we know that Exim will look only at the answer and additional section parts. */ memset(packet, 0, 12); pk += 12; /* Open the zone file. */ f = fopen(CS buffer, "r"); if (f == NULL) { fprintf(stderr, "fakens: failed to open %s: %s\n", buffer, strerror(errno)); return NO_RECOVERY; } /* Find the records we want, and add them to the result. */ count = 0; yield = find_records(f, zone, domain, qtype, qtypelen, &pk, &count, &dnssec, &aa); if (yield == NO_RECOVERY) goto END_OFF; header->ancount = htons(count); /* If the AA bit should be set (as indicated by the AA prefix in the zone file), we are expected to return some records in the authortive section. Bind9: If there is data in the answer section, the authoritive section contains the NS records, otherwise it contains the SOA record. Currently we mimic this behaviour for the first case (there is some answer record). */ if (aa) find_records(f, zone, zone[0] == '.' ? zone+1 : zone, US"NS", 2, &pk, &count, NULL, NULL); header->nscount = htons(count - ntohs(header->ancount)); /* There is no need to return any additional records because Exim no longer (from release 4.61) makes any use of them. */ header->arcount = 0; if (dnssec) header->ad = 1; if (aa) header->aa = 1; /* Close the zone file, write the result, and return. */ END_OFF: (void)fclose(f); (void)fwrite(packet, 1, pk - packet, stdout); return yield; } /* vi: aw ai sw=2 sts=2 ts=8 et */ /* End of fakens.c */