diff options
Diffstat (limited to 'g10/cipher.c')
| -rw-r--r-- | g10/cipher.c | 186 |
1 files changed, 186 insertions, 0 deletions
diff --git a/g10/cipher.c b/g10/cipher.c new file mode 100644 index 0000000..f10ce48 --- /dev/null +++ b/g10/cipher.c @@ -0,0 +1,186 @@ +/* cipher.c - En-/De-ciphering filter + * Copyright (C) 1998-2003, 2006, 2009 Free Software Foundation, Inc. + * Copyright (C) 1998-2003, 2006, 2009, 2017 Werner koch + * + * This file is part of GnuPG. + * + * GnuPG is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 3 of the License, or + * (at your option) any later version. + * + * GnuPG is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, see <https://www.gnu.org/licenses/>. + * SPDX-License-Identifier: GPL-3.0+ + */ + +#include <config.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <errno.h> + +#include "gpg.h" +#include "../common/status.h" +#include "../common/iobuf.h" +#include "../common/util.h" +#include "filter.h" +#include "packet.h" +#include "options.h" +#include "main.h" +#include "../common/i18n.h" +#include "../common/status.h" + + +#define MIN_PARTIAL_SIZE 512 + + +static void +write_header (cipher_filter_context_t *cfx, iobuf_t a) +{ + gcry_error_t err; + PACKET pkt; + PKT_encrypted ed; + byte temp[18]; + unsigned int blocksize; + unsigned int nprefix; + + blocksize = openpgp_cipher_get_algo_blklen (cfx->dek->algo); + if ( blocksize < 8 || blocksize > 16 ) + log_fatal ("unsupported blocksize %u\n", blocksize); + + memset (&ed, 0, sizeof ed); + ed.len = cfx->datalen; + ed.extralen = blocksize + 2; + ed.new_ctb = !ed.len; + if (cfx->dek->use_mdc) + { + ed.mdc_method = DIGEST_ALGO_SHA1; + gcry_md_open (&cfx->mdc_hash, DIGEST_ALGO_SHA1, 0); + if (DBG_HASHING) + gcry_md_debug (cfx->mdc_hash, "creatmdc"); + } + else + { + log_info (_("WARNING: " + "encrypting without integrity protection is dangerous\n")); + log_info (_("Hint: Do not use option %s\n"), "--rfc2440"); + } + + write_status_printf (STATUS_BEGIN_ENCRYPTION, "%d %d", + ed.mdc_method, cfx->dek->algo); + + init_packet (&pkt); + pkt.pkttype = cfx->dek->use_mdc? PKT_ENCRYPTED_MDC : PKT_ENCRYPTED; + pkt.pkt.encrypted = &ed; + if (build_packet( a, &pkt)) + log_bug ("build_packet(ENCR_DATA) failed\n"); + nprefix = blocksize; + gcry_randomize (temp, nprefix, GCRY_STRONG_RANDOM ); + temp[nprefix] = temp[nprefix-2]; + temp[nprefix+1] = temp[nprefix-1]; + print_cipher_algo_note (cfx->dek->algo); + err = openpgp_cipher_open (&cfx->cipher_hd, + cfx->dek->algo, + GCRY_CIPHER_MODE_CFB, + (GCRY_CIPHER_SECURE + | ((cfx->dek->use_mdc || cfx->dek->algo >= 100)? + 0 : GCRY_CIPHER_ENABLE_SYNC))); + if (err) + { + /* We should never get an error here cause we already checked, + * that the algorithm is available. */ + BUG(); + } + + /* log_hexdump ("thekey", cfx->dek->key, cfx->dek->keylen); */ + gcry_cipher_setkey (cfx->cipher_hd, cfx->dek->key, cfx->dek->keylen); + gcry_cipher_setiv (cfx->cipher_hd, NULL, 0); + /* log_hexdump ("prefix", temp, nprefix+2); */ + if (cfx->mdc_hash) /* Hash the "IV". */ + gcry_md_write (cfx->mdc_hash, temp, nprefix+2 ); + gcry_cipher_encrypt (cfx->cipher_hd, temp, nprefix+2, NULL, 0); + gcry_cipher_sync (cfx->cipher_hd); + iobuf_write (a, temp, nprefix+2); + + cfx->short_blklen_warn = (blocksize < 16); + cfx->short_blklen_count = nprefix+2; + + cfx->wrote_header = 1; +} + + +/* + * This filter is used to en/de-cipher data with a symmetric algorithm + */ +int +cipher_filter (void *opaque, int control, iobuf_t a, byte *buf, size_t *ret_len) +{ + cipher_filter_context_t *cfx = opaque; + size_t size = *ret_len; + int rc = 0; + + if (control == IOBUFCTRL_UNDERFLOW) /* decrypt */ + { + rc = -1; /* not yet used */ + } + else if (control == IOBUFCTRL_FLUSH) /* encrypt */ + { + log_assert (a); + if (!cfx->wrote_header) + write_header (cfx, a); + if (cfx->mdc_hash) + gcry_md_write (cfx->mdc_hash, buf, size); + gcry_cipher_encrypt (cfx->cipher_hd, buf, size, NULL, 0); + if (cfx->short_blklen_warn) + { + cfx->short_blklen_count += size; + if (cfx->short_blklen_count > (150 * 1024 * 1024)) + { + log_info ("WARNING: encrypting more than %d MiB with algorithm " + "%s should be avoided\n", 150, + openpgp_cipher_algo_name (cfx->dek->algo)); + cfx->short_blklen_warn = 0; /* Don't show again. */ + } + } + + rc = iobuf_write (a, buf, size); + } + else if (control == IOBUFCTRL_FREE) + { + if (cfx->mdc_hash) + { + byte *hash; + int hashlen = gcry_md_get_algo_dlen (gcry_md_get_algo(cfx->mdc_hash)); + byte temp[22]; + + log_assert (hashlen == 20); + /* We must hash the prefix of the MDC packet here. */ + temp[0] = 0xd3; + temp[1] = 0x14; + gcry_md_putc (cfx->mdc_hash, temp[0]); + gcry_md_putc (cfx->mdc_hash, temp[1]); + + gcry_md_final (cfx->mdc_hash); + hash = gcry_md_read (cfx->mdc_hash, 0); + memcpy(temp+2, hash, 20); + gcry_cipher_encrypt (cfx->cipher_hd, temp, 22, NULL, 0); + gcry_md_close (cfx->mdc_hash); cfx->mdc_hash = NULL; + if (iobuf_write( a, temp, 22)) + log_error ("writing MDC packet failed\n"); + } + + gcry_cipher_close (cfx->cipher_hd); + } + else if (control == IOBUFCTRL_DESC) + { + mem2str (buf, "cipher_filter", *ret_len); + } + + return rc; +} |