From 950a034895b8a483eb6c0c97e16a2cbf03350815 Mon Sep 17 00:00:00 2001 From: Daniel Stenberg Date: Thu, 29 Oct 2009 08:59:40 +0000 Subject: Jakub Hrozek added ares_parse_txt_reply() for TXT parsing --- ares/ares_parse_txt_reply.c | 176 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 176 insertions(+) create mode 100644 ares/ares_parse_txt_reply.c (limited to 'ares/ares_parse_txt_reply.c') diff --git a/ares/ares_parse_txt_reply.c b/ares/ares_parse_txt_reply.c new file mode 100644 index 000000000..c99ee72e2 --- /dev/null +++ b/ares/ares_parse_txt_reply.c @@ -0,0 +1,176 @@ +/* Copyright (C) 2009 Jakub Hrozek +* +* 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 "setup.h" + +#if defined(WIN32) && !defined(WATT32) +#include "nameser.h" +#else +#include +#include +#include +#include +#include +#ifdef HAVE_ARPA_NAMESER_COMPAT_H +#include +#endif +#endif + +#include +#include +#include "ares.h" +#include "ares_dns.h" +#include "ares_private.h" + +int +ares_parse_txt_reply (const unsigned char *abuf, int alen, + struct ares_txt_reply **txt_out, int *ntxtreply) +{ + unsigned char substr_len = 0; + unsigned char str_len = 0; + unsigned int qdcount, ancount; + const unsigned char *aptr; + const unsigned char *strptr; + int status, i, rr_type, rr_class, rr_len; + long len; + char *hostname = NULL, *rr_name = NULL; + struct ares_txt_reply *txt = NULL; + + *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 ares_txt_reply array; ancount gives an upper bound */ + txt = malloc ((ancount) * sizeof (struct ares_txt_reply)); + if (!txt) + { + free (hostname); + return ARES_ENOMEM; + } + /* Zero out so we can safely free txt.txt even if NULL */ + memset(txt, 0, ancount * sizeof (struct ares_txt_reply)); + + /* 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) + { + /* + * There may be multiple substrings in a single TXT record. Each + * substring may be up to 255 characters in length, with a + * "length byte" indicating the size of the substring payload. + * RDATA contains both the length-bytes and payloads of all + * substrings contained therein. + */ + + /* Realloc would be expensive, compute the total length */ + txt[i].length = 0; + strptr = aptr; + while (strptr < (aptr + rr_len)) + { + memcpy ((void *) &substr_len, strptr, sizeof (unsigned char)); + txt[i].length += substr_len; + strptr += substr_len + 1; + } + + /* Including null byte */ + txt[i].txt = malloc (sizeof (unsigned char) * (txt[i].length + 1)); + if (txt[i].txt == NULL) + { + status = ARES_ENOMEM; + break; + } + + /* Step through the list of substrings, concatenating them */ + substr_len = 0; + str_len = 0; + strptr = aptr; + while (strptr < (aptr + rr_len)) + { + memcpy ((void *) &substr_len, strptr, sizeof (unsigned char)); + strptr++; + memcpy ((void *) txt[i].txt + str_len, strptr, + sizeof (unsigned char) * substr_len); + str_len += substr_len; + strptr += substr_len; + } + /* Make sure we NULL-terminate */ + txt[i].txt[txt[i].length] = '\0'; + + /* 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) + { + ares_free_txt_reply(txt, ancount); + return status; + } + + /* everything looks fine, return the data */ + *txt_out = txt; + *ntxtreply = ancount; + return 0; +} -- cgit v1.2.3