| 1 | /* $Cambridge: exim/test/src/fakens.c,v 1.3 2006/11/07 14:13:19 ph10 Exp $ */ |
| 2 | |
| 3 | /************************************************* |
| 4 | * fakens - A Fake Nameserver Program * |
| 5 | *************************************************/ |
| 6 | |
| 7 | /* This program exists to support the testing of DNS handling code in Exim. It |
| 8 | avoids the need to install special zones in a real nameserver. When Exim is |
| 9 | running in its (new) test harness, DNS lookups are first passed to this program |
| 10 | instead of to the real resolver. (With a few exceptions - see the discussion in |
| 11 | the test suite's README file.) The program is also passed the name of the Exim |
| 12 | spool directory; it expects to find its "zone files" in ../dnszones relative to |
| 13 | that directory. Note that there is little checking in this program. The fake |
| 14 | zone files are assumed to be syntactically valid. |
| 15 | |
| 16 | The zones that are handled are found by scanning the dnszones directory. A file |
| 17 | whose name is of the form db.ip4.x is a zone file for .x.in-addr.arpa; a file |
| 18 | whose name is of the form db.ip6.x is a zone file for .x.ip6.arpa; a file of |
| 19 | the form db.anything.else is a zone file for .anything.else. A file of the form |
| 20 | qualify.x.y specifies the domain that is used to qualify single-component |
| 21 | names, except for the name "dontqualify". |
| 22 | |
| 23 | The arguments to the program are: |
| 24 | |
| 25 | the name of the Exim spool directory |
| 26 | the domain name that is being sought |
| 27 | the DNS record type that is being sought |
| 28 | |
| 29 | The output from the program is written to stdout. It is supposed to be in |
| 30 | exactly the same format as a traditional namserver response (see RFC 1035) so |
| 31 | that Exim can process it as normal. At present, no compression is used. |
| 32 | Error messages are written to stderr. |
| 33 | |
| 34 | The return codes from the program are zero for success, and otherwise the |
| 35 | values that are set in h_errno after a failing call to the normal resolver: |
| 36 | |
| 37 | 1 HOST_NOT_FOUND host not found (authoritative) |
| 38 | 2 TRY_AGAIN server failure |
| 39 | 3 NO_RECOVERY non-recoverable error |
| 40 | 4 NO_DATA valid name, no data of requested type |
| 41 | |
| 42 | In a real nameserver, TRY_AGAIN is also used for a non-authoritative not found, |
| 43 | but it is not used for that here. There is also one extra return code: |
| 44 | |
| 45 | 5 PASS_ON requests Exim to call res_search() |
| 46 | |
| 47 | This is used for zones that fakens does not recognize. It is also used if a |
| 48 | line in the zone file contains exactly this: |
| 49 | |
| 50 | PASS ON NOT FOUND |
| 51 | |
| 52 | and the domain is not found. It converts the the result to PASS_ON instead of |
| 53 | HOST_NOT_FOUND. */ |
| 54 | |
| 55 | #include <ctype.h> |
| 56 | #include <stdarg.h> |
| 57 | #include <stdio.h> |
| 58 | #include <string.h> |
| 59 | #include <netdb.h> |
| 60 | #include <errno.h> |
| 61 | #include <arpa/nameser.h> |
| 62 | #include <sys/types.h> |
| 63 | #include <dirent.h> |
| 64 | |
| 65 | #define FALSE 0 |
| 66 | #define TRUE 1 |
| 67 | #define PASS_ON 5 |
| 68 | |
| 69 | typedef int BOOL; |
| 70 | typedef unsigned char uschar; |
| 71 | |
| 72 | #define CS (char *) |
| 73 | #define CCS (const char *) |
| 74 | #define US (unsigned char *) |
| 75 | |
| 76 | #define Ustrcat(s,t) strcat(CS(s),CCS(t)) |
| 77 | #define Ustrchr(s,n) US strchr(CCS(s),n) |
| 78 | #define Ustrcmp(s,t) strcmp(CCS(s),CCS(t)) |
| 79 | #define Ustrcpy(s,t) strcpy(CS(s),CCS(t)) |
| 80 | #define Ustrlen(s) (int)strlen(CCS(s)) |
| 81 | #define Ustrncmp(s,t,n) strncmp(CCS(s),CCS(t),n) |
| 82 | #define Ustrncpy(s,t,n) strncpy(CS(s),CCS(t),n) |
| 83 | |
| 84 | typedef struct zoneitem { |
| 85 | uschar *zone; |
| 86 | uschar *zonefile; |
| 87 | } zoneitem; |
| 88 | |
| 89 | typedef struct tlist { |
| 90 | uschar *name; |
| 91 | int value; |
| 92 | } tlist; |
| 93 | |
| 94 | /* On some (older?) operating systems, the standard ns_t_xxx definitions are |
| 95 | not available, and only the older T_xxx ones exist in nameser.h. If ns_t_a is |
| 96 | not defined, assume we are in this state. A really old system might not even |
| 97 | know about AAAA and SRV at all. */ |
| 98 | |
| 99 | #ifndef ns_t_a |
| 100 | #define ns_t_a T_A |
| 101 | #define ns_t_ns T_NS |
| 102 | #define ns_t_cname T_CNAME |
| 103 | #define ns_t_soa T_SOA |
| 104 | #define ns_t_ptr T_PTR |
| 105 | #define ns_t_mx T_MX |
| 106 | #define ns_t_txt T_TXT |
| 107 | #define ns_t_aaaa T_AAAA |
| 108 | #define ns_t_srv T_SRV |
| 109 | #ifndef T_AAAA |
| 110 | #define T_AAAA 28 |
| 111 | #endif |
| 112 | #ifndef T_SRV |
| 113 | #define T_SRV 33 |
| 114 | #endif |
| 115 | #endif |
| 116 | |
| 117 | static tlist type_list[] = { |
| 118 | { US"A", ns_t_a }, |
| 119 | { US"NS", ns_t_ns }, |
| 120 | { US"CNAME", ns_t_cname }, |
| 121 | /* { US"SOA", ns_t_soa }, Not currently in use */ |
| 122 | { US"PTR", ns_t_ptr }, |
| 123 | { US"MX", ns_t_mx }, |
| 124 | { US"TXT", ns_t_txt }, |
| 125 | { US"AAAA", ns_t_aaaa }, |
| 126 | { US"SRV", ns_t_srv }, |
| 127 | { NULL, 0 } |
| 128 | }; |
| 129 | |
| 130 | |
| 131 | |
| 132 | /************************************************* |
| 133 | * Get memory and sprintf into it * |
| 134 | *************************************************/ |
| 135 | |
| 136 | /* This is used when building a table of zones and their files. |
| 137 | |
| 138 | Arguments: |
| 139 | format a format string |
| 140 | ... arguments |
| 141 | |
| 142 | Returns: pointer to formatted string |
| 143 | */ |
| 144 | |
| 145 | static uschar * |
| 146 | fcopystring(uschar *format, ...) |
| 147 | { |
| 148 | uschar *yield; |
| 149 | char buffer[256]; |
| 150 | va_list ap; |
| 151 | va_start(ap, format); |
| 152 | vsprintf(buffer, format, ap); |
| 153 | va_end(ap); |
| 154 | yield = (uschar *)malloc(Ustrlen(buffer) + 1); |
| 155 | Ustrcpy(yield, buffer); |
| 156 | return yield; |
| 157 | } |
| 158 | |
| 159 | |
| 160 | /************************************************* |
| 161 | * Pack name into memory * |
| 162 | *************************************************/ |
| 163 | |
| 164 | /* This function packs a domain name into memory according to DNS rules. At |
| 165 | present, it doesn't do any compression. |
| 166 | |
| 167 | Arguments: |
| 168 | name the name |
| 169 | pk where to put it |
| 170 | |
| 171 | Returns: the updated value of pk |
| 172 | */ |
| 173 | |
| 174 | static uschar * |
| 175 | packname(uschar *name, uschar *pk) |
| 176 | { |
| 177 | while (*name != 0) |
| 178 | { |
| 179 | uschar *p = name; |
| 180 | while (*p != 0 && *p != '.') p++; |
| 181 | *pk++ = (p - name); |
| 182 | memmove(pk, name, p - name); |
| 183 | pk += p - name; |
| 184 | name = (*p == 0)? p : p + 1; |
| 185 | } |
| 186 | *pk++ = 0; |
| 187 | return pk; |
| 188 | } |
| 189 | |
| 190 | |
| 191 | |
| 192 | /************************************************* |
| 193 | * Scan file for RRs * |
| 194 | *************************************************/ |
| 195 | |
| 196 | /* This function scans an open "zone file" for appropriate records, and adds |
| 197 | any that are found to the output buffer. |
| 198 | |
| 199 | Arguments: |
| 200 | f the input FILE |
| 201 | zone the current zone name |
| 202 | domain the domain we are looking for |
| 203 | qtype the type of RR we want |
| 204 | qtypelen the length of qtype |
| 205 | pkptr points to the output buffer pointer; this is updated |
| 206 | countptr points to the record count; this is updated |
| 207 | |
| 208 | Returns: 0 on success, else HOST_NOT_FOUND or NO_DATA or NO_RECOVERY or |
| 209 | PASS_ON - the latter if a "PASS ON NOT FOUND" line is seen |
| 210 | */ |
| 211 | |
| 212 | static int |
| 213 | find_records(FILE *f, uschar *zone, uschar *domain, uschar *qtype, |
| 214 | int qtypelen, uschar **pkptr, int *countptr) |
| 215 | { |
| 216 | int yield = HOST_NOT_FOUND; |
| 217 | int domainlen = Ustrlen(domain); |
| 218 | BOOL pass_on_not_found = FALSE; |
| 219 | tlist *typeptr; |
| 220 | uschar *pk = *pkptr; |
| 221 | uschar buffer[256]; |
| 222 | uschar rrdomain[256]; |
| 223 | uschar RRdomain[256]; |
| 224 | |
| 225 | /* Decode the required type */ |
| 226 | |
| 227 | for (typeptr = type_list; typeptr->name != NULL; typeptr++) |
| 228 | { if (Ustrcmp(typeptr->name, qtype) == 0) break; } |
| 229 | if (typeptr->name == NULL) |
| 230 | { |
| 231 | fprintf(stderr, "fakens: unknown record type %s\n", qtype); |
| 232 | return NO_RECOVERY; |
| 233 | } |
| 234 | |
| 235 | rrdomain[0] = 0; /* No previous domain */ |
| 236 | (void)fseek(f, 0, SEEK_SET); /* Start again at the beginning */ |
| 237 | |
| 238 | /* Scan for RRs */ |
| 239 | |
| 240 | while (fgets(CS buffer, sizeof(buffer), f) != NULL) |
| 241 | { |
| 242 | uschar *rdlptr; |
| 243 | uschar *p, *ep, *pp; |
| 244 | BOOL found_cname = FALSE; |
| 245 | int i, plen, value; |
| 246 | int tvalue = typeptr->value; |
| 247 | int qtlen = qtypelen; |
| 248 | |
| 249 | p = buffer; |
| 250 | while (isspace(*p)) p++; |
| 251 | if (*p == 0 || *p == ';') continue; |
| 252 | |
| 253 | if (Ustrncmp(p, "PASS ON NOT FOUND", 17) == 0) |
| 254 | { |
| 255 | pass_on_not_found = TRUE; |
| 256 | continue; |
| 257 | } |
| 258 | |
| 259 | ep = buffer + Ustrlen(buffer); |
| 260 | while (isspace(ep[-1])) ep--; |
| 261 | *ep = 0; |
| 262 | |
| 263 | p = buffer; |
| 264 | if (!isspace(*p)) |
| 265 | { |
| 266 | uschar *pp = rrdomain; |
| 267 | uschar *PP = RRdomain; |
| 268 | while (!isspace(*p)) |
| 269 | { |
| 270 | *pp++ = tolower(*p); |
| 271 | *PP++ = *p++; |
| 272 | } |
| 273 | if (pp[-1] != '.') |
| 274 | { |
| 275 | Ustrcpy(pp, zone); |
| 276 | Ustrcpy(PP, zone); |
| 277 | } |
| 278 | else |
| 279 | { |
| 280 | pp[-1] = 0; |
| 281 | PP[-1] = 0; |
| 282 | } |
| 283 | } |
| 284 | |
| 285 | /* Compare domain names; first check for a wildcard */ |
| 286 | |
| 287 | if (rrdomain[0] == '*') |
| 288 | { |
| 289 | int restlen = Ustrlen(rrdomain) - 1; |
| 290 | if (domainlen > restlen && |
| 291 | Ustrcmp(domain + domainlen - restlen, rrdomain + 1) != 0) continue; |
| 292 | } |
| 293 | |
| 294 | /* Not a wildcard RR */ |
| 295 | |
| 296 | else if (Ustrcmp(domain, rrdomain) != 0) continue; |
| 297 | |
| 298 | /* The domain matches */ |
| 299 | |
| 300 | if (yield == HOST_NOT_FOUND) yield = NO_DATA; |
| 301 | |
| 302 | /* Compare RR types; a CNAME record is always returned */ |
| 303 | |
| 304 | while (isspace(*p)) p++; |
| 305 | |
| 306 | if (Ustrncmp(p, "CNAME", 5) == 0) |
| 307 | { |
| 308 | tvalue = ns_t_cname; |
| 309 | qtlen = 5; |
| 310 | found_cname = TRUE; |
| 311 | } |
| 312 | else if (Ustrncmp(p, qtype, qtypelen) != 0 || !isspace(p[qtypelen])) continue; |
| 313 | |
| 314 | /* Found a relevant record */ |
| 315 | |
| 316 | yield = 0; |
| 317 | *countptr = *countptr + 1; |
| 318 | |
| 319 | p += qtlen; |
| 320 | while (isspace(*p)) p++; |
| 321 | |
| 322 | /* For a wildcard record, use the search name; otherwise use the record's |
| 323 | name in its original case because it might contain upper case letters. */ |
| 324 | |
| 325 | pk = packname((rrdomain[0] == '*')? domain : RRdomain, pk); |
| 326 | *pk++ = (tvalue >> 8) & 255; |
| 327 | *pk++ = (tvalue) & 255; |
| 328 | *pk++ = 0; |
| 329 | *pk++ = 1; /* class = IN */ |
| 330 | |
| 331 | pk += 4; /* TTL field; don't care */ |
| 332 | |
| 333 | rdlptr = pk; /* remember rdlength field */ |
| 334 | pk += 2; |
| 335 | |
| 336 | /* The rest of the data depends on the type */ |
| 337 | |
| 338 | switch (tvalue) |
| 339 | { |
| 340 | case ns_t_soa: /* Not currently used */ |
| 341 | break; |
| 342 | |
| 343 | case ns_t_a: |
| 344 | for (i = 0; i < 4; i++) |
| 345 | { |
| 346 | value = 0; |
| 347 | while (isdigit(*p)) value = value*10 + *p++ - '0'; |
| 348 | *pk++ = value; |
| 349 | p++; |
| 350 | } |
| 351 | break; |
| 352 | |
| 353 | /* The only occurrence of a double colon is for ::1 */ |
| 354 | case ns_t_aaaa: |
| 355 | if (Ustrcmp(p, "::1") == 0) |
| 356 | { |
| 357 | memset(pk, 0, 15); |
| 358 | pk += 15; |
| 359 | *pk++ = 1; |
| 360 | } |
| 361 | else for (i = 0; i < 8; i++) |
| 362 | { |
| 363 | value = 0; |
| 364 | while (isxdigit(*p)) |
| 365 | { |
| 366 | value = value * 16 + toupper(*p) - (isdigit(*p)? '0' : '7'); |
| 367 | p++; |
| 368 | } |
| 369 | *pk++ = (value >> 8) & 255; |
| 370 | *pk++ = value & 255; |
| 371 | p++; |
| 372 | } |
| 373 | break; |
| 374 | |
| 375 | case ns_t_mx: |
| 376 | value = 0; |
| 377 | while (isdigit(*p)) value = value*10 + *p++ - '0'; |
| 378 | while (isspace(*p)) p++; |
| 379 | *pk++ = (value >> 8) & 255; |
| 380 | *pk++ = value & 255; |
| 381 | if (ep[-1] != '.') sprintf(ep, "%s.", zone); |
| 382 | pk = packname(p, pk); |
| 383 | plen = Ustrlen(p); |
| 384 | break; |
| 385 | |
| 386 | case ns_t_txt: |
| 387 | pp = pk++; |
| 388 | if (*p == '"') p++; /* Should always be the case */ |
| 389 | while (*p != 0 && *p != '"') *pk++ = *p++; |
| 390 | *pp = pk - pp - 1; |
| 391 | break; |
| 392 | |
| 393 | case ns_t_srv: |
| 394 | for (i = 0; i < 3; i++) |
| 395 | { |
| 396 | value = 0; |
| 397 | while (isdigit(*p)) value = value*10 + *p++ - '0'; |
| 398 | while (isspace(*p)) p++; |
| 399 | *pk++ = (value >> 8) & 255; |
| 400 | *pk++ = value & 255; |
| 401 | } |
| 402 | |
| 403 | /* Fall through */ |
| 404 | |
| 405 | case ns_t_cname: |
| 406 | case ns_t_ns: |
| 407 | case ns_t_ptr: |
| 408 | if (ep[-1] != '.') sprintf(ep, "%s.", zone); |
| 409 | pk = packname(p, pk); |
| 410 | plen = Ustrlen(p); |
| 411 | break; |
| 412 | } |
| 413 | |
| 414 | /* Fill in the length, and we are done with this RR */ |
| 415 | |
| 416 | rdlptr[0] = ((pk - rdlptr - 2) >> 8) & 255; |
| 417 | rdlptr[1] = (pk -rdlptr - 2) & 255; |
| 418 | } |
| 419 | |
| 420 | *pkptr = pk; |
| 421 | return (yield == HOST_NOT_FOUND && pass_on_not_found)? PASS_ON : yield; |
| 422 | } |
| 423 | |
| 424 | |
| 425 | |
| 426 | /************************************************* |
| 427 | * Entry point and main program * |
| 428 | *************************************************/ |
| 429 | |
| 430 | int |
| 431 | main(int argc, char **argv) |
| 432 | { |
| 433 | FILE *f; |
| 434 | DIR *d; |
| 435 | int domlen, qtypelen; |
| 436 | int yield, count; |
| 437 | int i; |
| 438 | int zonecount = 0; |
| 439 | struct dirent *de; |
| 440 | zoneitem zones[32]; |
| 441 | uschar *qualify = NULL; |
| 442 | uschar *p, *zone; |
| 443 | uschar *zonefile = NULL; |
| 444 | uschar domain[256]; |
| 445 | uschar buffer[256]; |
| 446 | uschar qtype[12]; |
| 447 | uschar packet[512]; |
| 448 | uschar *pk = packet; |
| 449 | |
| 450 | if (argc != 4) |
| 451 | { |
| 452 | fprintf(stderr, "fakens: expected 3 arguments, received %d\n", argc-1); |
| 453 | return NO_RECOVERY; |
| 454 | } |
| 455 | |
| 456 | /* Find the zones */ |
| 457 | |
| 458 | (void)sprintf(buffer, "%s/../dnszones", argv[1]); |
| 459 | |
| 460 | d = opendir(CCS buffer); |
| 461 | if (d == NULL) |
| 462 | { |
| 463 | fprintf(stderr, "fakens: failed to opendir %s: %s\n", buffer, |
| 464 | strerror(errno)); |
| 465 | return NO_RECOVERY; |
| 466 | } |
| 467 | |
| 468 | while ((de = readdir(d)) != NULL) |
| 469 | { |
| 470 | uschar *name = de->d_name; |
| 471 | if (Ustrncmp(name, "qualify.", 8) == 0) |
| 472 | { |
| 473 | qualify = fcopystring("%s", name + 7); |
| 474 | continue; |
| 475 | } |
| 476 | if (Ustrncmp(name, "db.", 3) != 0) continue; |
| 477 | if (Ustrncmp(name + 3, "ip4.", 4) == 0) |
| 478 | zones[zonecount].zone = fcopystring("%s.in-addr.arpa", name + 6); |
| 479 | else if (Ustrncmp(name + 3, "ip6.", 4) == 0) |
| 480 | zones[zonecount].zone = fcopystring("%s.ip6.arpa", name + 6); |
| 481 | else |
| 482 | zones[zonecount].zone = fcopystring("%s", name + 2); |
| 483 | zones[zonecount++].zonefile = fcopystring("%s", name); |
| 484 | } |
| 485 | (void)closedir(d); |
| 486 | |
| 487 | /* Get the RR type and upper case it, and check that we recognize it. */ |
| 488 | |
| 489 | Ustrncpy(qtype, argv[3], sizeof(qtype)); |
| 490 | qtypelen = Ustrlen(qtype); |
| 491 | for (p = qtype; *p != 0; p++) *p = toupper(*p); |
| 492 | |
| 493 | /* Find the domain, lower case it, check that it is in a zone that we handle, |
| 494 | and set up the zone file name. The zone names in the table all start with a |
| 495 | dot. */ |
| 496 | |
| 497 | domlen = Ustrlen(argv[2]); |
| 498 | if (argv[2][domlen-1] == '.') domlen--; |
| 499 | Ustrncpy(domain, argv[2], domlen); |
| 500 | domain[domlen] = 0; |
| 501 | for (i = 0; i < domlen; i++) domain[i] = tolower(domain[i]); |
| 502 | |
| 503 | if (Ustrchr(domain, '.') == NULL && qualify != NULL && |
| 504 | Ustrcmp(domain, "dontqualify") != 0) |
| 505 | { |
| 506 | Ustrcat(domain, qualify); |
| 507 | domlen += Ustrlen(qualify); |
| 508 | } |
| 509 | |
| 510 | for (i = 0; i < zonecount; i++) |
| 511 | { |
| 512 | int zlen; |
| 513 | zone = zones[i].zone; |
| 514 | zlen = Ustrlen(zone); |
| 515 | if (Ustrcmp(domain, zone+1) == 0 || (domlen >= zlen && |
| 516 | Ustrcmp(domain + domlen - zlen, zone) == 0)) |
| 517 | { |
| 518 | zonefile = zones[i].zonefile; |
| 519 | break; |
| 520 | } |
| 521 | } |
| 522 | |
| 523 | if (zonefile == NULL) |
| 524 | { |
| 525 | fprintf(stderr, "fakens: query not in faked zone: domain is: %s\n", domain); |
| 526 | return PASS_ON; |
| 527 | } |
| 528 | |
| 529 | (void)sprintf(buffer, "%s/../dnszones/%s", argv[1], zonefile); |
| 530 | |
| 531 | /* Initialize the start of the response packet. We don't have to fake up |
| 532 | everything, because we know that Exim will look only at the answer and |
| 533 | additional section parts. */ |
| 534 | |
| 535 | memset(packet, 0, 12); |
| 536 | pk += 12; |
| 537 | |
| 538 | /* Open the zone file. */ |
| 539 | |
| 540 | f = fopen(buffer, "r"); |
| 541 | if (f == NULL) |
| 542 | { |
| 543 | fprintf(stderr, "fakens: failed to open %s: %s\n", buffer, strerror(errno)); |
| 544 | return NO_RECOVERY; |
| 545 | } |
| 546 | |
| 547 | /* Find the records we want, and add them to the result. */ |
| 548 | |
| 549 | count = 0; |
| 550 | yield = find_records(f, zone, domain, qtype, qtypelen, &pk, &count); |
| 551 | if (yield == NO_RECOVERY) goto END_OFF; |
| 552 | |
| 553 | packet[6] = (count >> 8) & 255; |
| 554 | packet[7] = count & 255; |
| 555 | |
| 556 | /* There is no need to return any additional records because Exim no longer |
| 557 | (from release 4.61) makes any use of them. */ |
| 558 | |
| 559 | packet[10] = 0; |
| 560 | packet[11] = 0; |
| 561 | |
| 562 | /* Close the zone file, write the result, and return. */ |
| 563 | |
| 564 | END_OFF: |
| 565 | (void)fclose(f); |
| 566 | (void)fwrite(packet, 1, pk - packet, stdout); |
| 567 | return yield; |
| 568 | } |
| 569 | |
| 570 | /* End of fakens.c */ |