/* SSSD Async resolver - SRV records parsing Authors: Jakub Hrozek <jhrozek@redhat.com> Copyright (C) Red Hat, Inc 2009 This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version. This program 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 General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>. */ /* * This code is based on other c-ares parsing licensed as follows: * Copyright 1998 by the Massachusetts Institute of Technology. * * Permission to use, copy, modify, and distribute this * software and its documentation for any purpose and without * fee is hereby granted, provided that the above copyright * notice appear in all copies and that both that copyright * notice and this permission notice appear in supporting * documentation, and that the name of M.I.T. not be used in * advertising or publicity pertaining to distribution of the * software without specific, written prior permission. * M.I.T. makes no representations about the suitability of * this software for any purpose. It is provided "as is" * without express or implied warranty. */ #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> #include <netdb.h> #include <arpa/nameser.h> #include <stdlib.h> #include <string.h> #include "ares.h" /* this drags in some private macros c-ares uses */ #include "ares_dns.h" #include "ares_data.h" #include "ares_parse_srv_reply.h" int _ares_parse_srv_reply (const unsigned char *abuf, int alen, struct ares_srv_reply **srv_out) { unsigned int qdcount, ancount, i; const unsigned char *aptr, *vptr; int status, rr_type, rr_class, rr_len; long len; char *hostname = NULL, *rr_name = NULL; struct ares_srv_reply *srv_head = NULL; struct ares_srv_reply *srv_last = NULL; struct ares_srv_reply *srv_curr; /* Set *srv_out to NULL for all failure cases. */ *srv_out = NULL; /* Give up if abuf doesn't have room for a header. */ if (alen < HFIXEDSZ) return ARES_EBADRESP; /* Fetch the question and answer count from the header. */ qdcount = DNS_HEADER_QDCOUNT (abuf); ancount = DNS_HEADER_ANCOUNT (abuf); if (qdcount != 1) return ARES_EBADRESP; if (ancount == 0) return ARES_ENODATA; /* Expand the name from the question, and skip past the question. */ aptr = abuf + HFIXEDSZ; status = ares_expand_name (aptr, abuf, alen, &hostname, &len); if (status != ARES_SUCCESS) return status; if (aptr + len + QFIXEDSZ > abuf + alen) { free (hostname); return ARES_EBADRESP; } aptr += len + QFIXEDSZ; /* Examine each answer resource record (RR) in turn. */ for (i = 0; i < (int) ancount; i++) { /* Decode the RR up to the data field. */ status = ares_expand_name (aptr, abuf, alen, &rr_name, &len); if (status != ARES_SUCCESS) { break; } aptr += len; if (aptr + RRFIXEDSZ > abuf + alen) { status = ARES_EBADRESP; break; } rr_type = DNS_RR_TYPE (aptr); rr_class = DNS_RR_CLASS (aptr); rr_len = DNS_RR_LEN (aptr); aptr += RRFIXEDSZ; /* Check if we are really looking at a SRV record */ if (rr_class == C_IN && rr_type == T_SRV) { /* parse the SRV record itself */ if (rr_len < 6) { status = ARES_EBADRESP; break; } /* Allocate storage for this SRV answer appending it to the list */ srv_curr = _ares_malloc_data(ARES_DATATYPE_SRV_REPLY); if (!srv_curr) { status = ARES_ENOMEM; break; } if (srv_last) { srv_last->next = srv_curr; } else { srv_head = srv_curr; } srv_last = srv_curr; vptr = aptr; srv_curr->priority = ntohs (*((const unsigned short *)vptr)); vptr += sizeof(const unsigned short); srv_curr->weight = ntohs (*((const unsigned short *)vptr)); vptr += sizeof(const unsigned short); srv_curr->port = ntohs (*((const unsigned short *)vptr)); vptr += sizeof(const unsigned short); status = ares_expand_name (vptr, abuf, alen, &srv_curr->host, &len); if (status != ARES_SUCCESS) break; } /* Don't lose memory in the next iteration */ free(rr_name); rr_name = NULL; /* Move on to the next record */ aptr += rr_len; } if (hostname) free (hostname); if (rr_name) free (rr_name); /* clean up on error */ if (status != ARES_SUCCESS) { if (srv_head) _ares_free_data (srv_head); return status; } /* everything looks fine, return the data */ *srv_out = srv_head; return ARES_SUCCESS; }