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2fc27c8696
* common/dns-cert.c (get_dns_cert): Make r_key optional. * common/pka.c: Rewrite for the new hash based lookup. * common/t-pka.c: New. * configure.ac: Remove option --disable-dns-pka. (USE_DNS_PKA): Remove ac_define. * g10/getkey.c (parse_auto_key_locate): Always include PKA. -- Note that although PKA is now always build, it will only work if support for looking up via DNS has not been disabled. The new PKA only works with the IPGP DNS certtype and shall be used only to retrieve the fingerprint and optional the key for the first time. Due to the security problems with DNSSEC the former assumption to validate the key using DNSSEC is not anymore justified. Instead an additional layer (e.g. Trust-On-First-Use) needs to be implemented to track change to the key. Having a solid way of getting a key matching a mail address is however a must have. More work needs to go into a redefinition of the --verify-options pka-lookups and pka-trust-increase. The auto-key-locate mechanism should also be able to continue key fetching with another methods once the fingerprint has been retrieved with PKA. Signed-off-by: Werner Koch <wk@gnupg.org>
369 lines
11 KiB
C
369 lines
11 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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* This file is free software; you can redistribute it and/or modify
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* it under the terms of either
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*
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* - the GNU Lesser General Public License as published by the Free
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* Software Foundation; either version 3 of the License, or (at
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* your option) any later version.
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*
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* or
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*
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* - the GNU General Public License as published by the Free
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* Software Foundation; either version 2 of the License, or (at
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* your option) any later version.
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*
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* or both in parallel, as here.
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*
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* This file 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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# ifdef HAVE_WINSOCK2_H
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# include <winsock2.h>
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# endif
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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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#endif
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#include "util.h"
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#include "host2net.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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/* Returns 0 on success or an error code. If a PGP CERT record was
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found, a new estream with that key will be returned at R_KEY and
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the other return parameters are set to NULL/0. If an IPGP CERT
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record was found the fingerprint is stored as an allocated block at
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R_FPR and its length at R_FPRLEN; an URL is is allocated as a
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string and returned at R_URL. If WANT_CERTTYPE is 0 this function
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returns the first CERT found with a supported type; it is expected
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that only one CERT record is used. If WANT_CERTTYPE is one of the
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supported certtypes only records wih this certtype are considered
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and the first found is returned. R_KEY is optional. */
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gpg_error_t
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get_dns_cert (const char *name, int want_certtype,
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estream_t *r_key,
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unsigned char **r_fpr, size_t *r_fprlen, char **r_url)
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{
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#ifdef USE_DNS_CERT
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#ifdef USE_ADNS
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gpg_error_t err;
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adns_state state;
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adns_answer *answer = NULL;
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unsigned int ctype;
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int count;
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if (r_key)
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*r_key = NULL;
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*r_fpr = NULL;
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*r_fprlen = 0;
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*r_url = NULL;
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if (adns_init (&state, adns_if_noerrprint, NULL))
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{
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err = gpg_err_make (default_errsource, gpg_err_code_from_syserror ());
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log_error ("error initializing adns: %s\n", strerror (errno));
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return err;
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}
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if (adns_synchronous (state, name, (adns_r_unknown | my_adns_r_cert),
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adns_qf_quoteok_query, &answer))
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{
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err = gpg_err_make (default_errsource, gpg_err_code_from_syserror ());
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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 err;
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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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err = gpg_err_make (default_errsource, GPG_ERR_NOT_FOUND);
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goto leave;
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}
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err = gpg_err_make (default_errsource, GPG_ERR_NOT_FOUND);
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for (count = 0; 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 = buf16_to_uint (data);
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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 (want_certtype && want_certtype != ctype)
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; /* Not of the requested certtype. */
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else if (ctype == DNS_CERTTYPE_PGP && datalen >= 11 && r_key)
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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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*r_key = es_fopenmem_init (0, "rwb", data, datalen);
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if (!*r_key)
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err = gpg_err_make (default_errsource,
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gpg_err_code_from_syserror ());
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else
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err = 0;
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goto leave;
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}
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else if (ctype == DNS_CERTTYPE_IPGP && datalen && datalen < 1023
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&& datalen >= data[0] + 1 && r_fpr && r_fprlen && r_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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*r_fprlen = data[0];
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if (*r_fprlen)
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{
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*r_fpr = xtrymalloc (*r_fprlen);
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if (!*r_fpr)
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{
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err = gpg_err_make (default_errsource,
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gpg_err_code_from_syserror ());
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goto leave;
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}
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memcpy (*r_fpr, data + 1, *r_fprlen);
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}
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else
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*r_fpr = NULL;
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if (datalen > *r_fprlen + 1)
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{
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*r_url = xtrymalloc (datalen - (*r_fprlen + 1) + 1);
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if (!*r_url)
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{
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err = gpg_err_make (default_errsource,
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gpg_err_code_from_syserror ());
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xfree (*r_fpr);
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*r_fpr = NULL;
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goto leave;
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}
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memcpy (*r_url,
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data + (*r_fprlen + 1), datalen - (*r_fprlen + 1));
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(*r_url)[datalen - (*r_fprlen + 1)] = '\0';
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}
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else
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*r_url = NULL;
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err = 0;
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goto leave;
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}
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}
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leave:
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adns_free (answer);
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adns_finish (state);
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return err;
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#else /*!USE_ADNS*/
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gpg_error_t err;
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unsigned char *answer;
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int r;
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u16 count;
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if (r_key)
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*r_key = NULL;
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*r_fpr = NULL;
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*r_fprlen = 0;
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*r_url = NULL;
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/* Allocate a 64k buffer which is the limit for an DNS response. */
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answer = xtrymalloc (65536);
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if (!answer)
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return gpg_err_make (default_errsource, gpg_err_code_from_syserror ());
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err = gpg_err_make (default_errsource, GPG_ERR_NOT_FOUND);
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r = res_query (name, C_IN, T_CERT, answer, 65536);
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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 <= 65536
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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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{
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err = gpg_err_make (default_errsource, GPG_ERR_INV_OBJ);
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goto leave;
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}
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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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{
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err = gpg_err_make (default_errsource, GPG_ERR_INV_OBJ);
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goto leave;
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}
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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 = buf16_to_u16 (pt);
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pt += 2;
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class = buf16_to_u16 (pt);
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pt += 2;
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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 = buf16_to_u16 (pt);
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pt += 2;
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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 = buf16_to_u16 (pt);
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pt += 2;
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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 (want_certtype && want_certtype != ctype)
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; /* Not of the requested certtype. */
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else if (ctype == DNS_CERTTYPE_PGP && dlen && r_key)
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{
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/* PGP type */
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*r_key = es_fopenmem_init (0, "rwb", pt, dlen);
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if (!*r_key)
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err = gpg_err_make (default_errsource,
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gpg_err_code_from_syserror ());
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else
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err = 0;
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goto leave;
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}
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else if (ctype == DNS_CERTTYPE_IPGP
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&& dlen && dlen < 1023 && dlen >= pt[0] + 1)
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{
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/* IPGP type */
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*r_fprlen = pt[0];
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if (*r_fprlen)
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{
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*r_fpr = xtrymalloc (*r_fprlen);
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if (!*r_fpr)
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{
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err = gpg_err_make (default_errsource,
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gpg_err_code_from_syserror ());
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goto leave;
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}
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memcpy (*r_fpr, &pt[1], *r_fprlen);
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}
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else
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*r_fpr = NULL;
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if (dlen > *r_fprlen + 1)
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{
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*r_url = xtrymalloc (dlen - (*r_fprlen + 1) + 1);
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if (!*r_fpr)
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{
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err = gpg_err_make (default_errsource,
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gpg_err_code_from_syserror ());
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xfree (*r_fpr);
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*r_fpr = NULL;
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goto leave;
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}
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memcpy (*r_url, &pt[*r_fprlen + 1], dlen - (*r_fprlen + 1));
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(*r_url)[dlen - (*r_fprlen + 1)] = '\0';
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}
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else
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*r_url = NULL;
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err = 0;
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goto leave;
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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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leave:
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xfree (answer);
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return err;
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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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if (r_key)
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*r_key = NULL;
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*r_fpr = NULL;
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*r_fprlen = 0;
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*r_url = NULL;
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return gpg_err_make (default_errsource, GPG_ERR_NOT_SUPPORTED);
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#endif
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}
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