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306 lines
8.2 KiB
C
306 lines
8.2 KiB
C
/* dns-cert.c - DNS CERT code (rfc-4398)
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* Copyright (C) 2005, 2006, 2009 Free Software Foundation, Inc.
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*
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* This file is part of GNUPG.
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*
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* GNUPG is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3 of the License, or
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* (at your option) any later version.
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*
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* GNUPG is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see <http://www.gnu.org/licenses/>.
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*/
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#include <config.h>
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#include <sys/types.h>
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#ifdef USE_DNS_CERT
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# ifdef HAVE_W32_SYSTEM
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# include <windows.h>
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# else
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# include <netinet/in.h>
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# include <arpa/nameser.h>
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# include <resolv.h>
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# endif
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# include <string.h>
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#endif
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#ifdef USE_ADNS
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# include <adns.h>
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# ifndef HAVE_ADNS_FREE
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# define adns_free free
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# endif
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#endif
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#include "util.h"
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#include "iobuf.h"
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#include "dns-cert.h"
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/* Not every installation has gotten around to supporting CERTs
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yet... */
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#ifndef T_CERT
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#define T_CERT 37
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#endif
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/* ADNS has no support for CERT yet. */
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#define my_adns_r_cert 37
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/* Certificate types according to RFC-4398. */
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#define CERTTYPE_PKIX 1 /* X.509 as per PKIX. */
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#define CERTTYPE_SPKI 2 /* SPKI certificate. */
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#define CERTTYPE_PGP 3 /* OpenPGP packet. */
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#define CERTTYPE_IPKIX 4 /* The URL of an X.509 data object. */
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#define CERTTYPE_ISPKI 5 /* The URL of an SPKI certificate. */
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#define CERTTYPE_IPGP 6 /* The fingerprint and URL of an OpenPGP packet.*/
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#define CERTTYPE_ACPKIX 7 /* Attribute Certificate. */
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#define CERTTYPE_IACPKIX 8 /* The URL of an Attribute Certificate. */
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#define CERTTYPE_URI 253 /* URI private. */
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#define CERTTYPE_OID 254 /* OID private. */
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/* Returns -1 on error, 0 for no answer, 1 for PGP provided and 2 for
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IPGP provided. Note that this function returns the first CERT
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found with a supported type; it is expected that only one CERT
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record is used. */
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int
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get_dns_cert (const char *name, size_t max_size, IOBUF * iobuf,
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unsigned char **fpr, size_t * fpr_len, char **url)
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{
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#ifdef USE_DNS_CERT
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#ifdef USE_ADNS
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adns_state state;
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adns_answer *answer = NULL;
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int rc;
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unsigned int ctype;
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int count;
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rc = adns_init (&state, adns_if_noerrprint, NULL);
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if (rc)
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{
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log_error ("error initializing adns: %s\n", strerror (errno));
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return -1;
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}
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rc = adns_synchronous (state, name, (adns_r_unknown | my_adns_r_cert),
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adns_qf_quoteok_query, &answer);
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if (rc)
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{
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/* log_error ("DNS query failed: %s\n", strerror (errno)); */
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adns_finish (state);
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return -1;
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}
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if (answer->status != adns_s_ok)
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{
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/* log_error ("DNS query returned an error: %s (%s)\n", */
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/* adns_strerror (answer->status), */
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/* adns_errabbrev (answer->status)); */
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adns_free (answer);
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adns_finish (state);
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return 0;
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}
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for (rc = 0, count = 0; !rc && count < answer->nrrs; count++)
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{
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int datalen = answer->rrs.byteblock[count].len;
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const unsigned char *data = answer->rrs.byteblock[count].data;
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if (datalen < 5)
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continue; /* Truncated CERT record - skip. */
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ctype = ((data[0] << 8) | data[1]);
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/* (key tag and algorithm fields are not required.) */
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data += 5;
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datalen -= 5;
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if (ctype == CERTTYPE_PGP && datalen >= 11)
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{
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/* CERT type is PGP. Gpg checks for a minimum length of 11,
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thus we do the same. */
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*iobuf = iobuf_temp_with_content ((char *)data, datalen);
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rc = 1;
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}
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else if (ctype == CERTTYPE_IPGP && datalen && datalen < 1023
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&& datalen >= data[0] + 1 && fpr && fpr_len && url)
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{
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/* CERT type is IPGP. We made sure that the data is
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plausible and that the caller requested this
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information. */
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*fpr_len = data[0];
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if (*fpr_len)
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{
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*fpr = xmalloc (*fpr_len);
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memcpy (*fpr, data + 1, *fpr_len);
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}
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else
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*fpr = NULL;
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if (datalen > *fpr_len + 1)
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{
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*url = xmalloc (datalen - (*fpr_len + 1) + 1);
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memcpy (*url, data + (*fpr_len + 1), datalen - (*fpr_len + 1));
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(*url)[datalen - (*fpr_len + 1)] = '\0';
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}
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else
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*url = NULL;
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rc = 2;
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}
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}
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adns_free (answer);
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adns_finish (state);
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return rc;
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#else /*!USE_ADNS*/
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unsigned char *answer;
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int ret = -1;
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int r;
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u16 count;
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if (fpr)
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*fpr = NULL;
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if (url)
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*url = NULL;
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answer = xmalloc (max_size);
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r = res_query (name, C_IN, T_CERT, answer, max_size);
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/* Not too big, not too small, no errors and at least 1 answer. */
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if (r >= sizeof (HEADER) && r <= max_size
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&& (((HEADER *) answer)->rcode) == NOERROR
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&& (count = ntohs (((HEADER *) answer)->ancount)))
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{
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int rc;
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unsigned char *pt, *emsg;
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emsg = &answer[r];
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pt = &answer[sizeof (HEADER)];
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/* Skip over the query */
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rc = dn_skipname (pt, emsg);
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if (rc == -1)
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goto fail;
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pt += rc + QFIXEDSZ;
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/* There are several possible response types for a CERT request.
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We're interested in the PGP (a key) and IPGP (a URI) types.
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Skip all others. TODO: A key is better than a URI since
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we've gone through all this bother to fetch it, so favor that
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if we have both PGP and IPGP? */
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while (count-- > 0 && pt < emsg)
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{
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u16 type, class, dlen, ctype;
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rc = dn_skipname (pt, emsg); /* the name we just queried for */
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if (rc == -1)
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break;
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pt += rc;
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/* Truncated message? 15 bytes takes us to the point where
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we start looking at the ctype. */
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if ((emsg - pt) < 15)
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break;
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type = *pt++ << 8;
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type |= *pt++;
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class = *pt++ << 8;
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class |= *pt++;
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/* We asked for IN and got something else !? */
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if (class != C_IN)
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break;
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/* ttl */
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pt += 4;
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/* data length */
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dlen = *pt++ << 8;
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dlen |= *pt++;
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/* We asked for CERT and got something else - might be a
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CNAME, so loop around again. */
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if (type != T_CERT)
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{
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pt += dlen;
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continue;
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}
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/* The CERT type */
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ctype = *pt++ << 8;
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ctype |= *pt++;
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/* Skip the CERT key tag and algo which we don't need. */
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pt += 3;
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dlen -= 5;
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/* 15 bytes takes us to here */
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if (ctype == CERTTYPE_PGP && iobuf && dlen)
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{
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/* PGP type */
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*iobuf = iobuf_temp_with_content ((char *) pt, dlen);
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ret = 1;
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break;
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}
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else if (ctype == CERTTYPE_IPGP
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&& dlen && dlen < 1023 && dlen >= pt[0] + 1
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&& fpr && fpr_len && url)
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{
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/* IPGP type */
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*fpr_len = pt[0];
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if (*fpr_len)
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{
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*fpr = xmalloc (*fpr_len);
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memcpy (*fpr, &pt[1], *fpr_len);
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}
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else
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*fpr = NULL;
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if (dlen > *fpr_len + 1)
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{
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*url = xmalloc (dlen - (*fpr_len + 1) + 1);
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memcpy (*url, &pt[*fpr_len + 1], dlen - (*fpr_len + 1));
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(*url)[dlen - (*fpr_len + 1)] = '\0';
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}
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else
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*url = NULL;
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ret = 2;
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break;
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}
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/* Neither type matches, so go around to the next answer. */
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pt += dlen;
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}
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}
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fail:
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xfree (answer);
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return ret;
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#endif /*!USE_ADNS */
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#else /* !USE_DNS_CERT */
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(void)name;
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(void)max_size;
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(void)iobuf;
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(void)fpr;
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(void)fpr_len;
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(void)url;
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return -1;
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#endif
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}
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