src/nss-myhostname/nss-myhostname.c

   1 /***
   2   This file is part of systemd.
   3
   4   Copyright 2008-2011 Lennart Poettering
   5
   6   systemd is free software; you can redistribute it and/or modify it
   7   under the terms of the GNU Lesser General Public License as published by
   8   the Free Software Foundation; either version 2.1 of the License, or
   9   (at your option) any later version.
  10
  11   systemd is distributed in the hope that it will be useful, but
  12   WITHOUT ANY WARRANTY; without even the implied warranty of
  13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14   Lesser General Public License for more details.
  15
  16   You should have received a copy of the GNU Lesser General Public License
  17   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  18 ***/
  19
  20 #include <errno.h>
  21 #include <net/if.h>
  22 #include <netdb.h>
  23 #include <nss.h>
  24 #include <stdlib.h>
  25 #include <string.h>
  26
  27 #include "alloc-util.h"
  28 #include "hostname-util.h"
  29 #include "local-addresses.h"
  30 #include "macro.h"
  31 #include "nss-util.h"
  32 #include "signal-util.h"
  33 #include "string-util.h"
  34 #include "util.h"
  35
  36 /* We use 127.0.0.2 as IPv4 address. This has the advantage over
  37  * 127.0.0.1 that it can be translated back to the local hostname. For
  38  * IPv6 we use ::1 which unfortunately will not translate back to the
  39  * hostname but instead something like "localhost" or so. */
  40
  41 #define LOCALADDRESS_IPV4 (htobe32(0x7F000002))
  42 #define LOCALADDRESS_IPV6 &in6addr_loopback
  43
  44 NSS_GETHOSTBYNAME_PROTOTYPES(myhostname);
  45 NSS_GETHOSTBYADDR_PROTOTYPES(myhostname);
  46
  47 enum nss_status _nss_myhostname_gethostbyname4_r(
  48                 const char *name,
  49                 struct gaih_addrtuple **pat,
  50                 char *buffer, size_t buflen,
  51                 int *errnop, int *h_errnop,
  52                 int32_t *ttlp) {
  53
  54         struct gaih_addrtuple *r_tuple, *r_tuple_prev = NULL;
  55         _cleanup_free_ struct local_address *addresses = NULL;
  56         _cleanup_free_ char *hn = NULL;
  57         const char *canonical = NULL;
  58         int n_addresses = 0;
  59         uint32_t local_address_ipv4;
  60         struct local_address *a;
  61         size_t l, idx, ms;
  62         char *r_name;
  63         unsigned n;
  64
  65         BLOCK_SIGNALS(NSS_SIGNALS_BLOCK);
  66
  67         assert(name);
  68         assert(pat);
  69         assert(buffer);
  70         assert(errnop);
  71         assert(h_errnop);
  72
  73         if (is_localhost(name)) {
  74                 /* We respond to 'localhost', so that /etc/hosts
  75                  * is optional */
  76
  77                 canonical = "localhost";
  78                 local_address_ipv4 = htobe32(INADDR_LOOPBACK);
  79
  80         } else if (is_gateway_hostname(name)) {
  81
  82                 n_addresses = local_gateways(NULL, 0, AF_UNSPEC, &addresses);
  83                 if (n_addresses <= 0) {
  84                         *errnop = ENOENT;
  85                         *h_errnop = HOST_NOT_FOUND;
  86                         return NSS_STATUS_NOTFOUND;
  87                 }
  88
  89                 canonical = "gateway";
  90
  91         } else {
  92                 hn = gethostname_malloc();
  93                 if (!hn) {
  94                         *errnop = ENOMEM;
  95                         *h_errnop = NO_RECOVERY;
  96                         return NSS_STATUS_TRYAGAIN;
  97                 }
  98
  99                 /* We respond to our local host name, our hostname suffixed with a single dot. */
 100                 if (!streq(name, hn) && !streq_ptr(startswith(name, hn), ".")) {
 101                         *errnop = ENOENT;
 102                         *h_errnop = HOST_NOT_FOUND;
 103                         return NSS_STATUS_NOTFOUND;
 104                 }
 105
 106                 n_addresses = local_addresses(NULL, 0, AF_UNSPEC, &addresses);
 107                 if (n_addresses < 0)
 108                         n_addresses = 0;
 109
 110                 canonical = hn;
 111                 local_address_ipv4 = LOCALADDRESS_IPV4;
 112         }
 113
 114         l = strlen(canonical);
 115         ms = ALIGN(l+1) + ALIGN(sizeof(struct gaih_addrtuple)) * (n_addresses > 0 ? n_addresses : 2);
 116         if (buflen < ms) {
 117                 *errnop = ENOMEM;
 118                 *h_errnop = NO_RECOVERY;
 119                 return NSS_STATUS_TRYAGAIN;
 120         }
 121
 122         /* First, fill in hostname */
 123         r_name = buffer;
 124         memcpy(r_name, canonical, l+1);
 125         idx = ALIGN(l+1);
 126
 127         assert(n_addresses >= 0);
 128         if (n_addresses == 0) {
 129                 /* Second, fill in IPv6 tuple */
 130                 r_tuple = (struct gaih_addrtuple*) (buffer + idx);
 131                 r_tuple->next = r_tuple_prev;
 132                 r_tuple->name = r_name;
 133                 r_tuple->family = AF_INET6;
 134                 memcpy(r_tuple->addr, LOCALADDRESS_IPV6, 16);
 135                 r_tuple->scopeid = 0;
 136
 137                 idx += ALIGN(sizeof(struct gaih_addrtuple));
 138                 r_tuple_prev = r_tuple;
 139
 140                 /* Third, fill in IPv4 tuple */
 141                 r_tuple = (struct gaih_addrtuple*) (buffer + idx);
 142                 r_tuple->next = r_tuple_prev;
 143                 r_tuple->name = r_name;
 144                 r_tuple->family = AF_INET;
 145                 *(uint32_t*) r_tuple->addr = local_address_ipv4;
 146                 r_tuple->scopeid = 0;
 147
 148                 idx += ALIGN(sizeof(struct gaih_addrtuple));
 149                 r_tuple_prev = r_tuple;
 150         }
 151
 152         /* Fourth, fill actual addresses in, but in backwards order */
 153         for (a = addresses + n_addresses - 1, n = 0; (int) n < n_addresses; n++, a--) {
 154                 r_tuple = (struct gaih_addrtuple*) (buffer + idx);
 155                 r_tuple->next = r_tuple_prev;
 156                 r_tuple->name = r_name;
 157                 r_tuple->family = a->family;
 158                 r_tuple->scopeid = a->family == AF_INET6 && IN6_IS_ADDR_LINKLOCAL(&a->address.in6) ? a->ifindex : 0;
 159                 memcpy(r_tuple->addr, &a->address, 16);
 160
 161                 idx += ALIGN(sizeof(struct gaih_addrtuple));
 162                 r_tuple_prev = r_tuple;
 163         }
 164
 165         /* Verify the size matches */
 166         assert(idx == ms);
 167
 168         /* Nscd expects us to store the first record in **pat. */
 169         if (*pat)
 170                 **pat = *r_tuple_prev;
 171         else
 172                 *pat = r_tuple_prev;
 173
 174         if (ttlp)
 175                 *ttlp = 0;
 176
 177         /* Explicitly reset all error variables */
 178         *errnop = 0;
 179         *h_errnop = NETDB_SUCCESS;
 180         h_errno = 0;
 181
 182         return NSS_STATUS_SUCCESS;
 183 }
 184
 185 static enum nss_status fill_in_hostent(
 186                 const char *canonical, const char *additional,
 187                 int af,
 188                 struct local_address *addresses, unsigned n_addresses,
 189                 uint32_t local_address_ipv4,
 190                 struct hostent *result,
 191                 char *buffer, size_t buflen,
 192                 int *errnop, int *h_errnop,
 193                 int32_t *ttlp,
 194                 char **canonp) {
 195
 196         size_t l_canonical, l_additional, idx, ms, alen;
 197         char *r_addr, *r_name, *r_aliases, *r_alias = NULL, *r_addr_list;
 198         struct local_address *a;
 199         unsigned n, c;
 200
 201         assert(canonical);
 202         assert(result);
 203         assert(buffer);
 204         assert(errnop);
 205         assert(h_errnop);
 206
 207         alen = FAMILY_ADDRESS_SIZE(af);
 208
 209         for (a = addresses, n = 0, c = 0; n < n_addresses; a++, n++)
 210                 if (af == a->family)
 211                         c++;
 212
 213         l_canonical = strlen(canonical);
 214         l_additional = additional ? strlen(additional) : 0;
 215         ms = ALIGN(l_canonical+1)+
 216                 (additional ? ALIGN(l_additional+1) : 0) +
 217                 sizeof(char*) +
 218                 (additional ? sizeof(char*) : 0) +
 219                 (c > 0 ? c : 1) * ALIGN(alen) +
 220                 (c > 0 ? c+1 : 2) * sizeof(char*);
 221
 222         if (buflen < ms) {
 223                 *errnop = ENOMEM;
 224                 *h_errnop = NO_RECOVERY;
 225                 return NSS_STATUS_TRYAGAIN;
 226         }
 227
 228         /* First, fill in hostnames */
 229         r_name = buffer;
 230         memcpy(r_name, canonical, l_canonical+1);
 231         idx = ALIGN(l_canonical+1);
 232
 233         if (additional) {
 234                 r_alias = buffer + idx;
 235                 memcpy(r_alias, additional, l_additional+1);
 236                 idx += ALIGN(l_additional+1);
 237         }
 238
 239         /* Second, create aliases array */
 240         r_aliases = buffer + idx;
 241         if (additional) {
 242                 ((char**) r_aliases)[0] = r_alias;
 243                 ((char**) r_aliases)[1] = NULL;
 244                 idx += 2*sizeof(char*);
 245         } else {
 246                 ((char**) r_aliases)[0] = NULL;
 247                 idx += sizeof(char*);
 248         }
 249
 250         /* Third, add addresses */
 251         r_addr = buffer + idx;
 252         if (c > 0) {
 253                 unsigned i = 0;
 254
 255                 for (a = addresses, n = 0; n < n_addresses; a++, n++) {
 256                         if (af != a->family)
 257                                 continue;
 258
 259                         memcpy(r_addr + i*ALIGN(alen), &a->address, alen);
 260                         i++;
 261                 }
 262
 263                 assert(i == c);
 264                 idx += c*ALIGN(alen);
 265         } else {
 266                 if (af == AF_INET)
 267                         *(uint32_t*) r_addr = local_address_ipv4;
 268                 else
 269                         memcpy(r_addr, LOCALADDRESS_IPV6, 16);
 270
 271                 idx += ALIGN(alen);
 272         }
 273
 274         /* Fourth, add address pointer array */
 275         r_addr_list = buffer + idx;
 276         if (c > 0) {
 277                 unsigned i;
 278
 279                 for (i = 0; i < c; i++)
 280                         ((char**) r_addr_list)[i] = r_addr + i*ALIGN(alen);
 281
 282                 ((char**) r_addr_list)[i] = NULL;
 283                 idx += (c+1) * sizeof(char*);
 284
 285         } else {
 286                 ((char**) r_addr_list)[0] = r_addr;
 287                 ((char**) r_addr_list)[1] = NULL;
 288                 idx += 2 * sizeof(char*);
 289         }
 290
 291         /* Verify the size matches */
 292         assert(idx == ms);
 293
 294         result->h_name = r_name;
 295         result->h_aliases = (char**) r_aliases;
 296         result->h_addrtype = af;
 297         result->h_length = alen;
 298         result->h_addr_list = (char**) r_addr_list;
 299
 300         if (ttlp)
 301                 *ttlp = 0;
 302
 303         if (canonp)
 304                 *canonp = r_name;
 305
 306         /* Explicitly reset all error variables */
 307         *errnop = 0;
 308         *h_errnop = NETDB_SUCCESS;
 309         h_errno = 0;
 310
 311         return NSS_STATUS_SUCCESS;
 312 }
 313
 314 enum nss_status _nss_myhostname_gethostbyname3_r(
 315                 const char *name,
 316                 int af,
 317                 struct hostent *host,
 318                 char *buffer, size_t buflen,
 319                 int *errnop, int *h_errnop,
 320                 int32_t *ttlp,
 321                 char **canonp) {
 322
 323         _cleanup_free_ struct local_address *addresses = NULL;
 324         const char *canonical, *additional = NULL;
 325         _cleanup_free_ char *hn = NULL;
 326         uint32_t local_address_ipv4 = 0;
 327         int n_addresses = 0;
 328
 329         BLOCK_SIGNALS(NSS_SIGNALS_BLOCK);
 330
 331         assert(name);
 332         assert(host);
 333         assert(buffer);
 334         assert(errnop);
 335         assert(h_errnop);
 336
 337         if (af == AF_UNSPEC)
 338                 af = AF_INET;
 339
 340         if (af != AF_INET && af != AF_INET6) {
 341                 *errnop = EAFNOSUPPORT;
 342                 *h_errnop = NO_DATA;
 343                 return NSS_STATUS_UNAVAIL;
 344         }
 345
 346         if (is_localhost(name)) {
 347                 canonical = "localhost";
 348                 local_address_ipv4 = htobe32(INADDR_LOOPBACK);
 349
 350         } else if (is_gateway_hostname(name)) {
 351
 352                 n_addresses = local_gateways(NULL, 0, af, &addresses);
 353                 if (n_addresses <= 0) {
 354                         *errnop = ENOENT;
 355                         *h_errnop = HOST_NOT_FOUND;
 356                         return NSS_STATUS_NOTFOUND;
 357                 }
 358
 359                 canonical = "gateway";
 360
 361         } else {
 362                 hn = gethostname_malloc();
 363                 if (!hn) {
 364                         *errnop = ENOMEM;
 365                         *h_errnop = NO_RECOVERY;
 366                         return NSS_STATUS_TRYAGAIN;
 367                 }
 368
 369                 if (!streq(name, hn) && !streq_ptr(startswith(name, hn), ".")) {
 370                         *errnop = ENOENT;
 371                         *h_errnop = HOST_NOT_FOUND;
 372                         return NSS_STATUS_NOTFOUND;
 373                 }
 374
 375                 n_addresses = local_addresses(NULL, 0, af, &addresses);
 376                 if (n_addresses < 0)
 377                         n_addresses = 0;
 378
 379                 canonical = hn;
 380                 additional = n_addresses <= 0 && af == AF_INET6 ? "localhost" : NULL;
 381                 local_address_ipv4 = LOCALADDRESS_IPV4;
 382         }
 383
 384         return fill_in_hostent(
 385                         canonical, additional,
 386                         af,
 387                         addresses, n_addresses,
 388                         local_address_ipv4,
 389                         host,
 390                         buffer, buflen,
 391                         errnop, h_errnop,
 392                         ttlp,
 393                         canonp);
 394 }
 395
 396 enum nss_status _nss_myhostname_gethostbyaddr2_r(
 397                 const void* addr, socklen_t len,
 398                 int af,
 399                 struct hostent *host,
 400                 char *buffer, size_t buflen,
 401                 int *errnop, int *h_errnop,
 402                 int32_t *ttlp) {
 403
 404         const char *canonical = NULL, *additional = NULL;
 405         uint32_t local_address_ipv4 = LOCALADDRESS_IPV4;
 406         _cleanup_free_ struct local_address *addresses = NULL;
 407         _cleanup_free_ char *hn = NULL;
 408         int n_addresses = 0;
 409         struct local_address *a;
 410         bool additional_from_hostname = false;
 411         unsigned n;
 412
 413         BLOCK_SIGNALS(NSS_SIGNALS_BLOCK);
 414
 415         assert(addr);
 416         assert(host);
 417         assert(buffer);
 418         assert(errnop);
 419         assert(h_errnop);
 420
 421         if (!IN_SET(af, AF_INET, AF_INET6)) {
 422                 *errnop = EAFNOSUPPORT;
 423                 *h_errnop = NO_DATA;
 424                 return NSS_STATUS_UNAVAIL;
 425         }
 426
 427         if (len != FAMILY_ADDRESS_SIZE(af)) {
 428                 *errnop = EINVAL;
 429                 *h_errnop = NO_RECOVERY;
 430                 return NSS_STATUS_UNAVAIL;
 431         }
 432
 433         if (af == AF_INET) {
 434                 if ((*(uint32_t*) addr) == LOCALADDRESS_IPV4)
 435                         goto found;
 436
 437                 if ((*(uint32_t*) addr) == htobe32(INADDR_LOOPBACK)) {
 438                         canonical = "localhost";
 439                         local_address_ipv4 = htobe32(INADDR_LOOPBACK);
 440                         goto found;
 441                 }
 442
 443         } else {
 444                 assert(af == AF_INET6);
 445
 446                 if (memcmp(addr, LOCALADDRESS_IPV6, 16) == 0) {
 447                         canonical = "localhost";
 448                         additional_from_hostname = true;
 449                         goto found;
 450                 }
 451         }
 452
 453         n_addresses = local_addresses(NULL, 0, AF_UNSPEC, &addresses);
 454         for (a = addresses, n = 0; (int) n < n_addresses; n++, a++) {
 455                 if (af != a->family)
 456                         continue;
 457
 458                 if (memcmp(addr, &a->address, FAMILY_ADDRESS_SIZE(af)) == 0)
 459                         goto found;
 460         }
 461
 462         addresses = mfree(addresses);
 463
 464         n_addresses = local_gateways(NULL, 0, AF_UNSPEC, &addresses);
 465         for (a = addresses, n = 0; (int) n < n_addresses; n++, a++) {
 466                 if (af != a->family)
 467                         continue;
 468
 469                 if (memcmp(addr, &a->address, FAMILY_ADDRESS_SIZE(af)) == 0) {
 470                         canonical = "gateway";
 471                         goto found;
 472                 }
 473         }
 474
 475         *errnop = ENOENT;
 476         *h_errnop = HOST_NOT_FOUND;
 477         return NSS_STATUS_NOTFOUND;
 478
 479 found:
 480         if (!canonical || additional_from_hostname) {
 481                 hn = gethostname_malloc();
 482                 if (!hn) {
 483                         *errnop = ENOMEM;
 484                         *h_errnop = NO_RECOVERY;
 485                         return NSS_STATUS_TRYAGAIN;
 486                 }
 487
 488                 if (!canonical)
 489                         canonical = hn;
 490                 else
 491                         additional = hn;
 492         }
 493
 494         return fill_in_hostent(
 495                         canonical, additional,
 496                         af,
 497                         addresses, n_addresses,
 498                         local_address_ipv4,
 499                         host,
 500                         buffer, buflen,
 501                         errnop, h_errnop,
 502                         ttlp,
 503                         NULL);
 504 }
 505
 506 NSS_GETHOSTBYNAME_FALLBACKS(myhostname);
 507 NSS_GETHOSTBYADDR_FALLBACKS(myhostname);