| /* Copyright (C) 2004-2018 Free Software Foundation, Inc. |
| This file is part of the GNU C Library. |
| Contributed by Ulrich Drepper <drepper@redhat.com>, 2004. |
| |
| The GNU C Library is free software; you can redistribute it and/or |
| modify it under the terms of the GNU Lesser General Public |
| License as published by the Free Software Foundation; either |
| version 2.1 of the License, or (at your option) any later version. |
| |
| The GNU C Library is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| Lesser General Public License for more details. |
| |
| You should have received a copy of the GNU Lesser General Public |
| License along with the GNU C Library; if not, see |
| <http://www.gnu.org/licenses/>. */ |
| |
| #include <errno.h> |
| #include <netdb.h> |
| #include <resolv.h> |
| #include <stdlib.h> |
| #include <stdint.h> |
| #include <arpa/nameser.h> |
| #include <nsswitch.h> |
| #include <resolv/resolv_context.h> |
| #include <resolv/resolv-internal.h> |
| |
| #if PACKETSZ > 65536 |
| # define MAXPACKET PACKETSZ |
| #else |
| # define MAXPACKET 65536 |
| #endif |
| |
| |
| /* We need this time later. */ |
| typedef union querybuf |
| { |
| HEADER hdr; |
| unsigned char buf[MAXPACKET]; |
| } querybuf; |
| |
| |
| static const short int qtypes[] = { ns_t_a, ns_t_aaaa }; |
| #define nqtypes (sizeof (qtypes) / sizeof (qtypes[0])) |
| |
| |
| enum nss_status |
| _nss_dns_getcanonname_r (const char *name, char *buffer, size_t buflen, |
| char **result,int *errnop, int *h_errnop) |
| { |
| /* Just an alibi buffer, res_nquery will allocate a real buffer for |
| us. */ |
| unsigned char buf[20]; |
| union |
| { |
| querybuf *buf; |
| unsigned char *ptr; |
| } ansp = { .ptr = buf }; |
| enum nss_status status = NSS_STATUS_UNAVAIL; |
| |
| struct resolv_context *ctx = __resolv_context_get (); |
| if (ctx == NULL) |
| { |
| *errnop = errno; |
| *h_errnop = NETDB_INTERNAL; |
| return NSS_STATUS_UNAVAIL; |
| } |
| |
| for (int i = 0; i < nqtypes; ++i) |
| { |
| int r = __res_context_query (ctx, name, ns_c_in, qtypes[i], |
| buf, sizeof (buf), &ansp.ptr, NULL, NULL, |
| NULL, NULL); |
| if (r > 0) |
| { |
| /* We need to decode the response. Just one question record. |
| And if we got no answers we bail out, too. */ |
| if (ansp.buf->hdr.qdcount != htons (1)) |
| continue; |
| |
| /* Number of answers. */ |
| unsigned int ancount = ntohs (ansp.buf->hdr.ancount); |
| |
| /* Beginning and end of the buffer with query, answer, and the |
| rest. */ |
| unsigned char *ptr = &ansp.buf->buf[sizeof (HEADER)]; |
| unsigned char *endptr = ansp.ptr + r; |
| |
| /* Skip over the query. This is the name, type, and class. */ |
| int s = __dn_skipname (ptr, endptr); |
| if (s < 0) |
| { |
| unavail: |
| status = NSS_STATUS_UNAVAIL; |
| break; |
| } |
| |
| /* Skip over the name and the two 16-bit values containing type |
| and class. */ |
| ptr += s + 2 * sizeof (uint16_t); |
| |
| while (ancount-- > 0) |
| { |
| /* Now the reply. First again the name from the query, |
| then type, class, TTL, and the length of the RDATA. |
| We remember the name start. */ |
| unsigned char *namestart = ptr; |
| s = __dn_skipname (ptr, endptr); |
| if (s < 0) |
| goto unavail; |
| |
| ptr += s; |
| |
| /* Check that there are enough bytes for the RR |
| metadata. */ |
| if (endptr - ptr < 10) |
| goto unavail; |
| |
| /* Check whether type and class match. */ |
| uint_fast16_t type; |
| NS_GET16 (type, ptr); |
| if (type == qtypes[i]) |
| { |
| /* We found the record. */ |
| s = __dn_expand (ansp.buf->buf, endptr, namestart, |
| buffer, buflen); |
| if (s < 0) |
| { |
| if (errno != EMSGSIZE) |
| goto unavail; |
| |
| /* The buffer is too small. */ |
| *errnop = ERANGE; |
| status = NSS_STATUS_TRYAGAIN; |
| h_errno = NETDB_INTERNAL; |
| } |
| else |
| { |
| /* Success. */ |
| *result = buffer; |
| status = NSS_STATUS_SUCCESS; |
| } |
| |
| goto out; |
| } |
| |
| if (type != ns_t_cname) |
| goto unavail; |
| |
| if (__ns_get16 (ptr) != ns_c_in) |
| goto unavail; |
| |
| /* Also skip over class and TTL. */ |
| ptr += sizeof (uint16_t) + sizeof (uint32_t); |
| |
| /* Skip over RDATA length and RDATA itself. */ |
| uint16_t rdatalen = __ns_get16 (ptr); |
| ptr += sizeof (uint16_t); |
| /* Not enough room for RDATA. */ |
| if (endptr - ptr < rdatalen) |
| goto unavail; |
| ptr += rdatalen; |
| } |
| } |
| |
| /* Restore original buffer before retry. */ |
| if (ansp.ptr != buf) |
| { |
| free (ansp.ptr); |
| ansp.ptr = buf; |
| } |
| } |
| |
| out: |
| *h_errnop = h_errno; |
| |
| if (ansp.ptr != buf) |
| free (ansp.ptr); |
| __resolv_context_put (ctx); |
| return status; |
| } |