/* SSSD Async resolver - TXT records parsing Authors: Jakub Hrozek 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 . */ /* * 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 #include #include #include #include #include #include #include "ares.h" /* this drags in some private macros c-ares uses */ #include "ares_dns.h" #include "ares_parse_txt_reply.h" int _ares_parse_txt_reply(const unsigned char* abuf, int alen, struct txt_reply **txt_out, int *ntxtreply) { unsigned int qdcount, ancount; const unsigned char *aptr; int status, i, rr_type, rr_class, rr_len; long len; char *hostname = NULL, *rr_name = NULL; struct txt_reply *txt = NULL; if (txt_out) *txt_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; /* Allocate txt_reply array; ancount gives an upper bound */ txt = malloc ((ancount) * sizeof (struct txt_reply)); if (!txt) { free (hostname); return ARES_ENOMEM; } /* 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 TXT record */ if (rr_class == C_IN && rr_type == T_TXT) { /* Grab the TXT payload */ txt[i].length = rr_len; txt[i].txt = malloc(sizeof(unsigned char) * rr_len); if (txt[i].txt == NULL) { status = ARES_ENOMEM; break; } memcpy((void *) txt[i].txt, aptr+1, sizeof(unsigned char) * rr_len); /* Move on to the next record */ aptr += rr_len; } /* Don't lose memory in the next iteration */ free(rr_name); rr_name = NULL; } free(hostname); free(rr_name); /* clean up on error */ if (status != ARES_SUCCESS) { free (txt); return status; } /* everything looks fine, return the data */ *txt_out = txt; *ntxtreply = ancount; return 0; }