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![Werner Koch](/assets/img/avatar_default.png)
* g10/gpg.c: Tuen options --force-mdc, --no-force-mdc, --disable-mdc and --no-disable-mdc into NOPs. * g10/encrypt.c (use_mdc): Simplify. MDC is now almost always used. (use_aead): Ignore MDC options. Print warning for missing MDC feature flags. * g10/pkclist.c (warn_missing_mdc_from_pklist): Rename to ... (warn_missing_aead_from_pklist): this and adjust. -- The MDC is now always used except with --rfc2440 which will lead to a a big fat warning. Signed-off-by: Werner Koch <wk@gnupg.org>
188 lines
5.7 KiB
C
188 lines
5.7 KiB
C
/* cipher-cfb.c - Enciphering filter for the old CFB mode.
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* Copyright (C) 1998-2003, 2006, 2009 Free Software Foundation, Inc.
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* Copyright (C) 1998-2003, 2006, 2009, 2017 Werner koch
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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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* SPDX-License-Identifier: GPL-3.0+
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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 <errno.h>
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#include "gpg.h"
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#include "../common/status.h"
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#include "../common/iobuf.h"
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#include "../common/util.h"
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#include "filter.h"
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#include "packet.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 "../common/status.h"
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#define MIN_PARTIAL_SIZE 512
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static void
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write_header (cipher_filter_context_t *cfx, iobuf_t a)
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{
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gcry_error_t err;
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PACKET pkt;
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PKT_encrypted ed;
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byte temp[18];
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unsigned int blocksize;
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unsigned int nprefix;
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blocksize = openpgp_cipher_get_algo_blklen (cfx->dek->algo);
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if ( blocksize < 8 || blocksize > 16 )
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log_fatal ("unsupported blocksize %u\n", blocksize);
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memset (&ed, 0, sizeof ed);
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ed.len = cfx->datalen;
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ed.extralen = blocksize + 2;
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ed.new_ctb = !ed.len;
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if (cfx->dek->use_mdc)
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{
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ed.mdc_method = DIGEST_ALGO_SHA1;
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gcry_md_open (&cfx->mdc_hash, DIGEST_ALGO_SHA1, 0);
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if (DBG_HASHING)
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gcry_md_debug (cfx->mdc_hash, "creatmdc");
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}
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else
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{
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log_info (_("WARNING: "
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"encrypting without integrity protection is dangerous\n"));
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log_info (_("Hint: Do not use option %s\n"), "--rfc2440");
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}
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write_status_printf (STATUS_BEGIN_ENCRYPTION, "%d %d",
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ed.mdc_method, cfx->dek->algo);
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init_packet (&pkt);
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pkt.pkttype = cfx->dek->use_mdc? PKT_ENCRYPTED_MDC : PKT_ENCRYPTED;
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pkt.pkt.encrypted = &ed;
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if (build_packet( a, &pkt))
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log_bug ("build_packet(ENCR_DATA) failed\n");
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nprefix = blocksize;
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gcry_randomize (temp, nprefix, GCRY_STRONG_RANDOM );
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temp[nprefix] = temp[nprefix-2];
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temp[nprefix+1] = temp[nprefix-1];
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print_cipher_algo_note (cfx->dek->algo);
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err = openpgp_cipher_open (&cfx->cipher_hd,
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cfx->dek->algo,
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GCRY_CIPHER_MODE_CFB,
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(GCRY_CIPHER_SECURE
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| ((cfx->dek->use_mdc || cfx->dek->algo >= 100)?
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0 : GCRY_CIPHER_ENABLE_SYNC)));
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if (err)
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{
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/* We should never get an error here cause we already checked,
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* that the algorithm is available. */
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BUG();
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}
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/* log_hexdump ("thekey", cfx->dek->key, cfx->dek->keylen); */
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gcry_cipher_setkey (cfx->cipher_hd, cfx->dek->key, cfx->dek->keylen);
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gcry_cipher_setiv (cfx->cipher_hd, NULL, 0);
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/* log_hexdump ("prefix", temp, nprefix+2); */
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if (cfx->mdc_hash) /* Hash the "IV". */
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gcry_md_write (cfx->mdc_hash, temp, nprefix+2 );
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gcry_cipher_encrypt (cfx->cipher_hd, temp, nprefix+2, NULL, 0);
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gcry_cipher_sync (cfx->cipher_hd);
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iobuf_write (a, temp, nprefix+2);
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cfx->short_blklen_warn = (blocksize < 16);
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cfx->short_blklen_count = nprefix+2;
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cfx->wrote_header = 1;
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}
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/*
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* This filter is used to en/de-cipher data with a symmetric algorithm
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*/
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int
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cipher_filter_cfb (void *opaque, int control,
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iobuf_t a, byte *buf, size_t *ret_len)
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{
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cipher_filter_context_t *cfx = opaque;
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size_t size = *ret_len;
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int rc = 0;
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if (control == IOBUFCTRL_UNDERFLOW) /* decrypt */
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{
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rc = -1; /* not yet used */
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}
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else if (control == IOBUFCTRL_FLUSH) /* encrypt */
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{
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log_assert (a);
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if (!cfx->wrote_header)
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write_header (cfx, a);
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if (cfx->mdc_hash)
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gcry_md_write (cfx->mdc_hash, buf, size);
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gcry_cipher_encrypt (cfx->cipher_hd, buf, size, NULL, 0);
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if (cfx->short_blklen_warn)
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{
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cfx->short_blklen_count += size;
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if (cfx->short_blklen_count > (150 * 1024 * 1024))
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{
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log_info ("WARNING: encrypting more than %d MiB with algorithm "
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"%s should be avoided\n", 150,
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openpgp_cipher_algo_name (cfx->dek->algo));
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cfx->short_blklen_warn = 0; /* Don't show again. */
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}
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}
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rc = iobuf_write (a, buf, size);
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}
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else if (control == IOBUFCTRL_FREE)
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{
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if (cfx->mdc_hash)
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{
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byte *hash;
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int hashlen = gcry_md_get_algo_dlen (gcry_md_get_algo(cfx->mdc_hash));
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byte temp[22];
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log_assert (hashlen == 20);
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/* We must hash the prefix of the MDC packet here. */
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temp[0] = 0xd3;
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temp[1] = 0x14;
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gcry_md_putc (cfx->mdc_hash, temp[0]);
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gcry_md_putc (cfx->mdc_hash, temp[1]);
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gcry_md_final (cfx->mdc_hash);
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hash = gcry_md_read (cfx->mdc_hash, 0);
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memcpy(temp+2, hash, 20);
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gcry_cipher_encrypt (cfx->cipher_hd, temp, 22, NULL, 0);
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gcry_md_close (cfx->mdc_hash); cfx->mdc_hash = NULL;
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if (iobuf_write( a, temp, 22))
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log_error ("writing MDC packet failed\n");
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}
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gcry_cipher_close (cfx->cipher_hd);
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}
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else if (control == IOBUFCTRL_DESC)
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{
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mem2str (buf, "cipher_filter_cfb", *ret_len);
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}
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return rc;
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}
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