/* cipher-cfb.c - Enciphering filter for the old CFB mode. * 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 . * SPDX-License-Identifier: GPL-3.0+ */ #include #include #include #include #include #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/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"); } 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_cfb (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_cfb", *ret_len); } return rc; }