/* cipher.c - En-/De-ciphering filter * Copyright (C) 1998, 1999, 2000, 2001, 2003, * 2006 Free Software Foundation, Inc. * * 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 . */ #include #include #include #include #include #include #include "gpg.h" #include "errors.h" #include "iobuf.h" #include "util.h" #include "filter.h" #include "packet.h" #include "options.h" #include "main.h" #include "status.h" #define MIN_PARTIAL_SIZE 512 static void write_header( cipher_filter_context_t *cfx, IOBUF a ) { gcry_error_t err; PACKET pkt; PKT_encrypted ed; byte temp[18]; unsigned int blocksize; unsigned int nprefix; blocksize = gcry_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 && !RFC1991; 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_start_debug (cfx->mdc_hash, "creatmdc"); } { char buf[20]; sprintf (buf, "%d %d", ed.mdc_method, cfx->dek->algo); write_status_text (STATUS_BEGIN_ENCRYPTION, buf); } 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 = gcry_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->header=1; } /**************** * This filter is used to en/de-cipher data with a conventional algorithm */ int cipher_filter( void *opaque, int control, IOBUF a, byte *buf, size_t *ret_len) { size_t size = *ret_len; cipher_filter_context_t *cfx = opaque; int rc=0; if( control == IOBUFCTRL_UNDERFLOW ) { /* decrypt */ rc = -1; /* not yet used */ } else if( control == IOBUFCTRL_FLUSH ) { /* encrypt */ assert(a); if( !cfx->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); 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]; 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 ) { *(char**)buf = "cipher_filter"; } return rc; }