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![NIIBE Yutaka](/assets/img/avatar_default.png)
* g10/ecdh.c (build_kdf_params): Use the first 20 octets. * g10/pkglue.c (pk_encrypt): Remove length check to 20. * g10/pubkey-enc.c (get_it): Likewise. Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>
504 lines
14 KiB
C
504 lines
14 KiB
C
/* pubkey-enc.c - Process a public key encoded packet.
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* Copyright (C) 1998, 1999, 2000, 2001, 2002, 2006, 2009,
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* 2010 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 <https://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 "gpg.h"
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#include "../common/util.h"
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#include "packet.h"
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#include "keydb.h"
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#include "trustdb.h"
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#include "../common/status.h"
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#include "options.h"
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#include "main.h"
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#include "../common/i18n.h"
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#include "pkglue.h"
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#include "call-agent.h"
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#include "../common/host2net.h"
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#include "../common/compliance.h"
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static gpg_error_t get_it (ctrl_t ctrl, struct pubkey_enc_list *k,
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DEK *dek, PKT_public_key *sk, u32 *keyid);
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/* Check that the given algo is mentioned in one of the valid user-ids. */
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static int
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is_algo_in_prefs (kbnode_t keyblock, preftype_t type, int algo)
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{
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kbnode_t k;
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for (k = keyblock; k; k = k->next)
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{
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if (k->pkt->pkttype == PKT_USER_ID)
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{
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PKT_user_id *uid = k->pkt->pkt.user_id;
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prefitem_t *prefs = uid->prefs;
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if (uid->created && prefs && !uid->flags.revoked && !uid->flags.expired)
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{
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for (; prefs->type; prefs++)
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if (prefs->type == type && prefs->value == algo)
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return 1;
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}
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}
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}
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return 0;
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}
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/*
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* Get the session key from a pubkey enc packet and return it in DEK,
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* which should have been allocated in secure memory by the caller.
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*/
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gpg_error_t
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get_session_key (ctrl_t ctrl, struct pubkey_enc_list *list, DEK *dek)
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{
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PKT_public_key *sk = NULL;
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gpg_error_t err;
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void *enum_context = NULL;
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u32 keyid[2];
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int search_for_secret_keys = 1;
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struct pubkey_enc_list *k;
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if (DBG_CLOCK)
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log_clock ("get_session_key enter");
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while (search_for_secret_keys)
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{
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sk = xmalloc_clear (sizeof *sk);
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err = enum_secret_keys (ctrl, &enum_context, sk);
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if (err)
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break;
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/* Check compliance. */
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if (! gnupg_pk_is_allowed (opt.compliance, PK_USE_DECRYPTION,
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sk->pubkey_algo, 0,
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sk->pkey, nbits_from_pk (sk), NULL))
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{
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log_info (_("key %s is not suitable for decryption"
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" in %s mode\n"),
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keystr_from_pk (sk),
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gnupg_compliance_option_string (opt.compliance));
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continue;
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}
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/* FIXME: The list needs to be sorted so that we try the keys in
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* an appropriate order. For example:
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* - On-disk keys w/o protection
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* - On-disk keys with a cached passphrase
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* - On-card keys of an active card
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* - On-disk keys with protection
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* - On-card keys from cards which are not plugged it. Here a
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* cancel-all button should stop asking for other cards.
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* Without any anonymous keys the sorting can be skipped.
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*/
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for (k = list; k; k = k->next)
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{
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if (!(k->pubkey_algo == PUBKEY_ALGO_ELGAMAL_E
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|| k->pubkey_algo == PUBKEY_ALGO_ECDH
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|| k->pubkey_algo == PUBKEY_ALGO_RSA
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|| k->pubkey_algo == PUBKEY_ALGO_RSA_E
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|| k->pubkey_algo == PUBKEY_ALGO_ELGAMAL))
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continue;
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if (openpgp_pk_test_algo2 (k->pubkey_algo, PUBKEY_USAGE_ENC))
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continue;
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if (sk->pubkey_algo != k->pubkey_algo)
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continue;
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keyid_from_pk (sk, keyid);
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if (!k->keyid[0] && !k->keyid[1])
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{
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if (opt.skip_hidden_recipients)
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continue;
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if (!opt.quiet)
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log_info (_("anonymous recipient; trying secret key %s ...\n"),
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keystr (keyid));
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}
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else if (opt.try_all_secrets
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|| (k->keyid[0] == keyid[0] && k->keyid[1] == keyid[1]))
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{
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if (!opt.quiet && !(sk->pubkey_usage & PUBKEY_USAGE_ENC))
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log_info (_("used key is not marked for encryption use.\n"));
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}
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else
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continue;
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err = get_it (ctrl, k, dek, sk, keyid);
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k->result = err;
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if (!err)
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{
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if (!opt.quiet && !k->keyid[0] && !k->keyid[1])
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{
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log_info (_("okay, we are the anonymous recipient.\n"));
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if (!(sk->pubkey_usage & PUBKEY_USAGE_ENC))
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log_info (_("used key is not marked for encryption use.\n")
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);
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}
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search_for_secret_keys = 0;
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break;
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}
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else if (gpg_err_code (err) == GPG_ERR_FULLY_CANCELED)
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{
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search_for_secret_keys = 0;
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break; /* Don't try any more secret keys. */
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}
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}
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}
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enum_secret_keys (ctrl, &enum_context, NULL); /* free context */
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if (gpg_err_code (err) == GPG_ERR_EOF)
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{
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err = gpg_error (GPG_ERR_NO_SECKEY);
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/* Return the last specific error, if any. */
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for (k = list; k; k = k->next)
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if (k->result != -1)
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err = k->result;
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}
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if (DBG_CLOCK)
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log_clock ("get_session_key leave");
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return err;
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}
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static gpg_error_t
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get_it (ctrl_t ctrl,
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struct pubkey_enc_list *enc, DEK *dek, PKT_public_key *sk, u32 *keyid)
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{
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gpg_error_t err;
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byte *frame = NULL;
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unsigned int n;
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size_t nframe;
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u16 csum, csum2;
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int padding;
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gcry_sexp_t s_data;
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char *desc;
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char *keygrip;
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byte fp[MAX_FINGERPRINT_LEN];
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if (DBG_CLOCK)
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log_clock ("decryption start");
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/* Get the keygrip. */
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err = hexkeygrip_from_pk (sk, &keygrip);
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if (err)
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goto leave;
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/* Convert the data to an S-expression. */
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if (sk->pubkey_algo == PUBKEY_ALGO_ELGAMAL
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|| sk->pubkey_algo == PUBKEY_ALGO_ELGAMAL_E)
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{
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if (!enc->data[0] || !enc->data[1])
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err = gpg_error (GPG_ERR_BAD_MPI);
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else
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err = gcry_sexp_build (&s_data, NULL, "(enc-val(elg(a%m)(b%m)))",
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enc->data[0], enc->data[1]);
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}
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else if (sk->pubkey_algo == PUBKEY_ALGO_RSA
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|| sk->pubkey_algo == PUBKEY_ALGO_RSA_E)
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{
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if (!enc->data[0])
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err = gpg_error (GPG_ERR_BAD_MPI);
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else
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err = gcry_sexp_build (&s_data, NULL, "(enc-val(rsa(a%m)))",
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enc->data[0]);
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}
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else if (sk->pubkey_algo == PUBKEY_ALGO_ECDH)
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{
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if (!enc->data[0] || !enc->data[1])
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err = gpg_error (GPG_ERR_BAD_MPI);
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else
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err = gcry_sexp_build (&s_data, NULL, "(enc-val(ecdh(s%m)(e%m)))",
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enc->data[1], enc->data[0]);
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}
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else
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err = gpg_error (GPG_ERR_BUG);
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if (err)
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goto leave;
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if (sk->pubkey_algo == PUBKEY_ALGO_ECDH)
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fingerprint_from_pk (sk, fp, NULL);
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/* Decrypt. */
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desc = gpg_format_keydesc (ctrl, sk, FORMAT_KEYDESC_NORMAL, 1);
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err = agent_pkdecrypt (NULL, keygrip,
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desc, sk->keyid, sk->main_keyid, sk->pubkey_algo,
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s_data, &frame, &nframe, &padding);
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xfree (desc);
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gcry_sexp_release (s_data);
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if (err)
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goto leave;
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/* Now get the DEK (data encryption key) from the frame
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*
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* Old versions encode the DEK in this format (msb is left):
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*
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* 0 1 DEK(16 bytes) CSUM(2 bytes) 0 RND(n bytes) 2
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*
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* Later versions encode the DEK like this:
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*
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* 0 2 RND(n bytes) 0 A DEK(k bytes) CSUM(2 bytes)
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*
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* (mpi_get_buffer already removed the leading zero).
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*
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* RND are non-zero randow bytes.
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* A is the cipher algorithm
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* DEK is the encryption key (session key) with length k
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* CSUM
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*/
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if (DBG_CRYPTO)
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log_printhex (frame, nframe, "DEK frame:");
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n = 0;
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if (sk->pubkey_algo == PUBKEY_ALGO_ECDH)
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{
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gcry_mpi_t decoded;
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/* At the beginning the frame are the bytes of shared point MPI. */
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err = pk_ecdh_decrypt (&decoded, fp, enc->data[1]/*encr data as an MPI*/,
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frame, nframe, sk->pkey);
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if(err)
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goto leave;
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xfree (frame);
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err = gcry_mpi_aprint (GCRYMPI_FMT_USG, &frame, &nframe, decoded);
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mpi_release (decoded);
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if (err)
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goto leave;
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/* Now the frame are the bytes decrypted but padded session key. */
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if (!nframe || nframe <= 8
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|| frame[nframe-1] > nframe)
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{
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err = gpg_error (GPG_ERR_WRONG_SECKEY);
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goto leave;
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}
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nframe -= frame[nframe-1]; /* Remove padding. */
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log_assert (!n); /* (used just below) */
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}
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else
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{
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if (padding)
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{
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if (n + 7 > nframe)
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{
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err = gpg_error (GPG_ERR_WRONG_SECKEY);
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goto leave;
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}
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/* FIXME: Actually the leading zero is required but due to
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* the way we encode the output in libgcrypt as an MPI we
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* are not able to encode that leading zero. However, when
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* using a Smartcard we are doing it the right way and
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* therefore we have to skip the zero. This should be fixed
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* in gpg-agent of course. */
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if (!frame[n])
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n++;
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if (frame[n] == 1 && frame[nframe - 1] == 2)
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{
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log_info (_("old encoding of the DEK is not supported\n"));
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err = gpg_error (GPG_ERR_CIPHER_ALGO);
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goto leave;
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}
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if (frame[n] != 2) /* Something went wrong. */
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{
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err = gpg_error (GPG_ERR_WRONG_SECKEY);
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goto leave;
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}
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for (n++; n < nframe && frame[n]; n++) /* Skip the random bytes. */
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;
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n++; /* Skip the zero byte. */
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}
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}
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if (n + 4 > nframe)
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{
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err = gpg_error (GPG_ERR_WRONG_SECKEY);
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goto leave;
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}
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dek->keylen = nframe - (n + 1) - 2;
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dek->algo = frame[n++];
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err = openpgp_cipher_test_algo (dek->algo);
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if (err)
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{
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if (!opt.quiet && gpg_err_code (err) == GPG_ERR_CIPHER_ALGO)
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{
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log_info (_("cipher algorithm %d%s is unknown or disabled\n"),
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dek->algo,
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dek->algo == CIPHER_ALGO_IDEA ? " (IDEA)" : "");
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}
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dek->algo = 0;
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goto leave;
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}
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if (dek->keylen != openpgp_cipher_get_algo_keylen (dek->algo))
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{
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err = gpg_error (GPG_ERR_WRONG_SECKEY);
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goto leave;
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}
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/* Copy the key to DEK and compare the checksum. */
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csum = buf16_to_u16 (frame+nframe-2);
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memcpy (dek->key, frame + n, dek->keylen);
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for (csum2 = 0, n = 0; n < dek->keylen; n++)
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csum2 += dek->key[n];
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if (csum != csum2)
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{
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err = gpg_error (GPG_ERR_WRONG_SECKEY);
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goto leave;
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}
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if (DBG_CLOCK)
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log_clock ("decryption ready");
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if (DBG_CRYPTO)
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log_printhex (dek->key, dek->keylen, "DEK is:");
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/* Check that the algo is in the preferences and whether it has
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* expired. Also print a status line with the key's fingerprint. */
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{
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PKT_public_key *pk = NULL;
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PKT_public_key *mainpk = NULL;
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KBNODE pkb = get_pubkeyblock (ctrl, keyid);
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if (!pkb)
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{
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err = -1;
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log_error ("oops: public key not found for preference check\n");
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}
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else if (pkb->pkt->pkt.public_key->selfsigversion > 3
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&& dek->algo != CIPHER_ALGO_3DES
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&& !opt.quiet
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&& !is_algo_in_prefs (pkb, PREFTYPE_SYM, dek->algo))
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log_info (_("WARNING: cipher algorithm %s not found in recipient"
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" preferences\n"), openpgp_cipher_algo_name (dek->algo));
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if (!err)
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{
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kbnode_t k;
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int first = 1;
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for (k = pkb; k; k = k->next)
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{
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if (k->pkt->pkttype == PKT_PUBLIC_KEY
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|| k->pkt->pkttype == PKT_PUBLIC_SUBKEY)
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{
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u32 aki[2];
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if (first)
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{
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first = 0;
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mainpk = k->pkt->pkt.public_key;
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}
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keyid_from_pk (k->pkt->pkt.public_key, aki);
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if (aki[0] == keyid[0] && aki[1] == keyid[1])
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{
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pk = k->pkt->pkt.public_key;
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break;
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}
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}
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}
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if (!pk)
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BUG ();
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if (pk->expiredate && pk->expiredate <= make_timestamp ())
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{
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log_info (_("Note: secret key %s expired at %s\n"),
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keystr (keyid), asctimestamp (pk->expiredate));
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}
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}
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if (pk && pk->flags.revoked)
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{
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log_info (_("Note: key has been revoked"));
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log_printf ("\n");
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show_revocation_reason (ctrl, pk, 1);
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}
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if (is_status_enabled () && pk && mainpk)
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{
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char pkhex[MAX_FINGERPRINT_LEN*2+1];
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char mainpkhex[MAX_FINGERPRINT_LEN*2+1];
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hexfingerprint (pk, pkhex, sizeof pkhex);
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hexfingerprint (mainpk, mainpkhex, sizeof mainpkhex);
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/* Note that we do not want to create a trustdb just for
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* getting the ownertrust: If there is no trustdb there can't
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* be ulitmately trusted key anyway and thus the ownertrust
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* value is irrelevant. */
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write_status_printf (STATUS_DECRYPTION_KEY, "%s %s %c",
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pkhex, mainpkhex,
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get_ownertrust_info (ctrl, mainpk, 1));
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}
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release_kbnode (pkb);
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err = 0;
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}
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leave:
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xfree (frame);
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xfree (keygrip);
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return err;
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}
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/*
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* Get the session key from the given string.
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* String is supposed to be formatted as this:
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* <algo-id>:<even-number-of-hex-digits>
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*/
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gpg_error_t
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get_override_session_key (DEK *dek, const char *string)
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{
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const char *s;
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int i;
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if (!string)
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return GPG_ERR_BAD_KEY;
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dek->algo = atoi (string);
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if (dek->algo < 1)
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return GPG_ERR_BAD_KEY;
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if (!(s = strchr (string, ':')))
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return GPG_ERR_BAD_KEY;
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s++;
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for (i = 0; i < DIM (dek->key) && *s; i++, s += 2)
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{
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int c = hextobyte (s);
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if (c == -1)
|
|
return GPG_ERR_BAD_KEY;
|
|
dek->key[i] = c;
|
|
}
|
|
if (*s)
|
|
return GPG_ERR_BAD_KEY;
|
|
dek->keylen = i;
|
|
return 0;
|
|
}
|