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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>
109 lines
2.8 KiB
C
109 lines
2.8 KiB
C
/* pka.c - DNS Public Key Association RR access
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* Copyright (C) 2005, 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 <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "util.h"
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#include "mbox-util.h"
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#include "dns-cert.h"
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#include "pka.h"
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/* For the given email ADDRESS lookup the PKA information in the DNS.
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On success the fingerprint is stored at FPRBUF and the URI will be
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returned in an allocated buffer. Note that the URI might be a zero
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length string as this information is optional. Caller must xfree
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the returned string. FPRBUFLEN gives the size of the expected
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fingerprint (usually 20).
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On error NULL is returned and the FPRBUF is not defined. */
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char *
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get_pka_info (const char *address, void *fprbuf, size_t fprbuflen)
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{
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char *result = NULL;
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char *mbox;
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char *domain; /* Points to mbox. */
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char hashbuf[20];
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char *hash = NULL;
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char *name = NULL;
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unsigned char *fpr = NULL;
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size_t fpr_len;
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char *url = NULL;
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gpg_error_t err;
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mbox = mailbox_from_userid (address);
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if (!mbox)
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goto leave;
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domain = strchr (mbox, '@');
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if (!domain)
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goto leave;
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*domain++ = 0;
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gcry_md_hash_buffer (GCRY_MD_SHA1, hashbuf, mbox, strlen (mbox));
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hash = zb32_encode (hashbuf, 8*20);
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if (!hash)
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goto leave;
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name = strconcat (hash, "._pka.", domain, NULL);
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if (!name)
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goto leave;
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if (get_dns_cert (name, DNS_CERTTYPE_IPGP, NULL, &fpr, &fpr_len, &url))
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goto leave;
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if (!fpr)
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goto leave;
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/* Return the fingerprint. */
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if (fpr_len != fprbuflen)
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{
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/* fprintf (stderr, "get_dns_cert failed: fprlen (%zu/%zu)\n", */
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/* fpr_len, fprbuflen); */
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goto leave;
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}
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memcpy (fprbuf, fpr, fpr_len);
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/* We return the URL or an empty string. */
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if (!url)
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url = xtrycalloc (1, 1);
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result = url;
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url = NULL;
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leave:
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xfree (fpr);
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xfree (url);
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xfree (name);
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xfree (hash);
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xfree (mbox);
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return result;
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}
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