gnupg/g10/encode.c

/* encode.c - encode data
 *	Copyright (C) 1998, 1999, 2000 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 2 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, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
 */

#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <assert.h>

#include "options.h"
#include "packet.h"
#include "errors.h"
#include "iobuf.h"
#include "keydb.h"
#include <gcrypt.h>
#include "util.h"
#include "main.h"
#include "filter.h"
#include "trustdb.h"
#include "i18n.h"


static int encode_simple( const char *filename, int mode );
static int write_pubkey_enc_from_list( PK_LIST pk_list, DEK *dek, IOBUF out );


/****************
 * Emulate our old PK interface here - sometime in the future we might
 * change the internal design to directly fit to libgcrypt.
 */
static int
pk_encrypt( int algo, MPI *resarr, MPI data, MPI *pkey )
{
    GCRY_SEXP s_ciph, s_data, s_pkey;
    int rc;

    /* make a sexp from pkey */
    if( algo == GCRY_PK_ELG || algo == GCRY_PK_ELG_E ) {
	rc = gcry_sexp_build ( &s_pkey, NULL,
			      "(public-key(elg(p%m)(g%m)(y%m)))",
				  pkey[0], pkey[1], pkey[2] );
    }
    else
	return GPGERR_PUBKEY_ALGO;

    if ( rc )
	BUG ();

    /* put the data into a simple list */
    if ( gcry_sexp_build( &s_data, NULL, "%m", data ) )
	BUG ();

    /* pass it to libgcrypt */
    rc = gcry_pk_encrypt( &s_ciph, s_data, s_pkey );
    gcry_sexp_release( s_data );
    gcry_sexp_release( s_pkey );

    if( rc )
	;
    else { /* add better error handling or make gnupg use S-Exp directly */
	GCRY_SEXP list = gcry_sexp_find_token( s_ciph, "a" , 0 );
	assert( list );
	resarr[0] = gcry_sexp_nth_mpi( list, 1, 0 );
	assert( resarr[0] );
	gcry_sexp_release ( list );

	list = gcry_sexp_find_token( s_ciph, "b" , 0 );
	assert( list );
	resarr[1] = gcry_sexp_nth_mpi( list, 1, 0 );
	assert( resarr[1] );
	gcry_sexp_release ( list );
    }

    gcry_sexp_release( s_ciph );
    return rc;
}


/****************
 * Encode FILENAME with only the symmetric cipher.  Take input from
 * stdin if FILENAME is NULL.
 */
int
encode_symmetric( const char *filename )
{
    return encode_simple( filename, 1 );
}

/****************
 * Encode FILENAME as a literal data packet only. Take input from
 * stdin if FILENAME is NULL.
 */
int
encode_store( const char *filename )
{
    return encode_simple( filename, 0 );
}



static int
encode_simple( const char *filename, int mode )
{
    IOBUF inp, out;
    PACKET pkt;
    PKT_plaintext *pt = NULL;
    STRING2KEY *s2k = NULL;
    int rc = 0;
    u32 filesize;
    cipher_filter_context_t cfx;
    armor_filter_context_t afx;
    compress_filter_context_t zfx;
    text_filter_context_t tfx;
    int do_compress = opt.compress && !opt.rfc1991;

    memset( &cfx, 0, sizeof cfx);
    memset( &afx, 0, sizeof afx);
    memset( &zfx, 0, sizeof zfx);
    memset( &tfx, 0, sizeof tfx);
    init_packet(&pkt);

    /* prepare iobufs */
    if( !(inp = iobuf_open(filename)) ) {
	log_error(_("%s: can't open: %s\n"), filename? filename: "[stdin]",
					strerror(errno) );
	return GPGERR_OPEN_FILE;
    }

    if( opt.textmode )
	iobuf_push_filter( inp, text_filter, &tfx );

    cfx.dek = NULL;
    if( mode ) {
	s2k = gcry_xcalloc( 1, sizeof *s2k );
	s2k->mode = opt.rfc1991? 0:opt.s2k_mode;
	s2k->hash_algo = opt.def_digest_algo ? opt.def_digest_algo
					     : opt.s2k_digest_algo;
	cfx.dek = passphrase_to_dek( NULL, 0,
		       opt.def_cipher_algo ? opt.def_cipher_algo
					   : opt.s2k_cipher_algo , s2k, 2 );
	if( !cfx.dek || !cfx.dek->keylen ) {
	    rc = GPGERR_PASSPHRASE;
	    gcry_free(cfx.dek);
	    gcry_free(s2k);
	    iobuf_close(inp);
	    log_error(_("error creating passphrase: %s\n"), gpg_errstr(rc) );
	    return rc;
	}
    }

    if( (rc = open_outfile( filename, opt.armor? 1:0, &out )) ) {
	iobuf_cancel(inp);
	gcry_free(cfx.dek);
	gcry_free(s2k);
	return rc;
    }

    if( opt.armor )
	iobuf_push_filter( out, armor_filter, &afx );
  #ifdef ENABLE_COMMENT_PACKETS
    else {
	write_comment( out, "#created by GNUPG v" VERSION " ("
					    PRINTABLE_OS_NAME ")");
	if( opt.comment_string )
	    write_comment( out, opt.comment_string );
    }
  #endif
    if( s2k && !opt.rfc1991 ) {
	PKT_symkey_enc *enc = gcry_xcalloc( 1, sizeof *enc );
	enc->version = 4;
	enc->cipher_algo = cfx.dek->algo;
	enc->s2k = *s2k;
	pkt.pkttype = PKT_SYMKEY_ENC;
	pkt.pkt.symkey_enc = enc;
	if( (rc = build_packet( out, &pkt )) )
	    log_error("build symkey packet failed: %s\n", gpg_errstr(rc) );
	gcry_free(enc);
    }

    if (!opt.no_literal) {
	/* setup the inner packet */
	if( filename || opt.set_filename ) {
	    char *s = make_basename( opt.set_filename ? opt.set_filename
						      : filename );
	    pt = gcry_xmalloc( sizeof *pt + strlen(s) - 1 );
	    pt->namelen = strlen(s);
	    memcpy(pt->name, s, pt->namelen );
	    gcry_free(s);
	}
	else { /* no filename */
	    pt = gcry_xmalloc( sizeof *pt - 1 );
	    pt->namelen = 0;
	}
    }

    /* pgp5 has problems to decrypt symmetrically encrypted data from
     * GnuPG if the filelength is in the inner packet.	It works
     * when only partial length headers are use.  Until we have
     * tracked this problem down. We use this temporary fix
     * (fixme: remove the && !mode )
     */
    if( filename && !opt.textmode && !mode ) {
	if( !(filesize = iobuf_get_filelength(inp)) )
	    log_info(_("%s: WARNING: empty file\n"), filename );
        /* we can't yet encode the length of very large files,
         * so we switch to partial length encoding in this case */
        if ( filesize >= IOBUF_FILELENGTH_LIMIT )
            filesize = 0;
    }
    else
	filesize = opt.set_filesize ? opt.set_filesize : 0; /* stdin */

    if (!opt.no_literal) {
	pt->timestamp = make_timestamp();
	pt->mode = opt.textmode? 't' : 'b';
	pt->len = filesize;
	pt->new_ctb = !pt->len && !opt.rfc1991;
	pt->buf = inp;
	pkt.pkttype = PKT_PLAINTEXT;
	pkt.pkt.plaintext = pt;
	cfx.datalen = filesize && !do_compress ? calc_packet_length( &pkt ) : 0;
    }
    else
	cfx.datalen = filesize && !do_compress ? filesize : 0;

    /* register the cipher filter */
    if( mode )
	iobuf_push_filter( out, cipher_filter, &cfx );
    /* register the compress filter */
    if( do_compress )
	iobuf_push_filter( out, compress_filter, &zfx );

    /* do the work */
    if (!opt.no_literal) {
	if( (rc = build_packet( out, &pkt )) )
	    log_error("build_packet failed: %s\n", gpg_errstr(rc) );
    }
    else {
	/* user requested not to create a literal packet,
	 * so we copy the plain data */
	byte copy_buffer[4096];
	int  bytes_copied;
	while ((bytes_copied = iobuf_read(inp, copy_buffer, 4096)) != -1)
	    if (iobuf_write(out, copy_buffer, bytes_copied) == -1) {
		rc = GPGERR_WRITE_FILE;
		log_error("copying input to output failed: %s\n", gpg_errstr(rc) );
		break;
	    }
	memset(copy_buffer, 0, 4096); /* burn buffer */
    }

    /* finish the stuff */
    iobuf_close(inp);
    if (rc)
	iobuf_cancel(out);
    else
	iobuf_close(out); /* fixme: check returncode */
    if (pt)
	pt->buf = NULL;
    free_packet(&pkt);
    gcry_free(cfx.dek);
    gcry_free(s2k);
    return rc;
}

/****************
 * Encrypt the file with the given userids (or ask if none
 * is supplied).
 */
int
encode_crypt( const char *filename, STRLIST remusr )
{
    IOBUF inp = NULL, out = NULL;
    PACKET pkt;
    PKT_plaintext *pt = NULL;
    int rc = 0;
    u32 filesize;
    armor_filter_context_t afx;
    compress_filter_context_t zfx;
    text_filter_context_t tfx;
    encrypt_filter_context_t efx;
    PK_LIST pk_list;
    int do_compress = opt.compress && !opt.rfc1991;

    memset( &afx, 0, sizeof afx);
    memset( &zfx, 0, sizeof zfx);
    memset( &tfx, 0, sizeof tfx);
    memset( &efx, 0, sizeof efx);
    init_packet(&pkt);

    if( (rc=build_pk_list( remusr, &pk_list, GCRY_PK_USAGE_ENCR)) )
	return rc;

    /* prepare iobufs */
    if( !(inp = iobuf_open(filename)) ) {
	log_error(_("can't open %s: %s\n"), filename? filename: "[stdin]",
					strerror(errno) );
	rc = GPGERR_OPEN_FILE;
	goto leave;
    }
    else if( opt.verbose )
	log_info(_("reading from `%s'\n"), filename? filename: "[stdin]");

    /* If the user selected textmode, push the text filter onto the input */
    if( opt.textmode )
	iobuf_push_filter( inp, text_filter, &tfx );

    /* Now we can create the outputfile */
    if( (rc = open_outfile( filename, opt.armor? 1:0, &out )) )
	goto leave;

    /* The first thing we have to push on the output stream
     * is the armor filter */
    if( opt.armor )
	iobuf_push_filter( out, armor_filter, &afx );

    /* Prepare the plaintext packet */
    {
        if (!opt.no_literal) {
            if( filename || opt.set_filename ) {
                char *s = make_basename( opt.set_filename ?
                                         opt.set_filename : filename );
                pt = gcry_xmalloc( sizeof *pt + strlen(s) - 1 );
                pt->namelen = strlen(s);
                memcpy(pt->name, s, pt->namelen );
                gcry_free(s);
            }
            else { /* no filename */
                pt = gcry_xmalloc( sizeof *pt - 1 );
                pt->namelen = 0;
            }
        }
        
        if( filename && !opt.textmode ) {
            if( !(filesize = iobuf_get_filelength(inp)) )
                log_info(_("%s: WARNING: empty file\n"), filename );
            /* we can't yet encode the length of very large files,
             * so we switch to partial lengthn encoding in this case */
            if ( filesize >= IOBUF_FILELENGTH_LIMIT )
                filesize = 0;
        }
        else
            filesize = opt.set_filesize ? opt.set_filesize : 0; /* stdin */
        
        if (!opt.no_literal) {
            pt->timestamp = make_timestamp();
            pt->mode = opt.textmode ? 't' : 'b';
            pt->len = filesize;
            pt->new_ctb = !pt->len && !opt.rfc1991;
            pt->buf = inp;
            pkt.pkttype = PKT_PLAINTEXT;
            pkt.pkt.plaintext = pt;
            efx.cfx.datalen = filesize && !do_compress?
                calc_packet_length( &pkt ) : 0;
        }
        else
            efx.cfx.datalen = filesize && !do_compress ? filesize : 0;
    }  /* end preparation of plaintext packet */
        
    /* push in the actual encryption filter */
    efx.pk_list = pk_list;
    iobuf_push_filter( out, encrypt_filter, &efx ); 

    /* register the compress filter (so that it is done before encryption) */
    if( do_compress ) {
	int compr_algo = select_algo_from_prefs( pk_list, PREFTYPE_COMPR );
	if( !compr_algo )
	    ; /* don't use compression */
	else {
	    if( compr_algo == 1 )
		zfx.algo = 1; /* default is 2 */
	    iobuf_push_filter( out, compress_filter, &zfx );
	}
    }

    /* do the work */
    if (!opt.no_literal) {
	if( (rc = build_packet( out, &pkt )) )
	    log_error("build_packet failed: %s\n", gpg_errstr(rc) );
    }
    else {
	/* user requested not to create a literal packet,
         * so we copy the plain data */
	byte copy_buffer[4096];
	int  bytes_copied;
	while ((bytes_copied = iobuf_read(inp, copy_buffer, 4096)) != -1)
	    if (iobuf_write(out, copy_buffer, bytes_copied) == -1) {
		rc = GPGERR_WRITE_FILE;
		log_error("copying input to output failed: %s\n", gpg_errstr(rc) );
		break;
	    }
	memset(copy_buffer, 0, DIM(copy_buffer)); /* burn buffer */
    }

    /* finish the stuff */
  leave:
    iobuf_close(inp);
    if( rc )
	iobuf_cancel(out);
    else
	iobuf_close(out); /* fixme: check returncode */
    if( pt )
	pt->buf = NULL;
    free_packet(&pkt);
    gcry_free(efx.cfx.dek); /* Hmmm, why does the encrypt filter does not 
                             * take care about this? */
    release_pk_list( pk_list );
    return rc;
}




/****************
 * Filter to handle the entire public key encryption.
 */
int
encrypt_filter( void *opaque, int control,
	       IOBUF a, byte *buf, size_t *ret_len)
{
    size_t size = *ret_len;
    encrypt_filter_context_t *efx = opaque;
    int rc=0;

    if( control == IOBUFCTRL_UNDERFLOW ) { /* decrypt */
	BUG(); /* not used */
    }
    else if( control == IOBUFCTRL_FLUSH ) { /* encrypt */
	if( !efx->header_okay ) {
	    efx->cfx.dek = gcry_xmalloc_secure( sizeof *efx->cfx.dek );

	    if( !opt.def_cipher_algo  ) { /* try to get it from the prefs */
		efx->cfx.dek->algo =
			  select_algo_from_prefs( efx->pk_list, PREFTYPE_SYM );
		if( efx->cfx.dek->algo == -1 )
		    efx->cfx.dek->algo = DEFAULT_CIPHER_ALGO;
	    }
	    else
		efx->cfx.dek->algo = opt.def_cipher_algo;
	    make_session_key( efx->cfx.dek );
	    if( DBG_CIPHER )
		log_hexdump("DEK is: ",
			     efx->cfx.dek->key, efx->cfx.dek->keylen );

	    rc = write_pubkey_enc_from_list( efx->pk_list, efx->cfx.dek, a );
	    if( rc )
		return rc;

	    iobuf_push_filter( a, cipher_filter, &efx->cfx );

	    efx->header_okay = 1;
	}
	rc = iobuf_write( a, buf, size );

    }
    else if( control == IOBUFCTRL_FREE ) {
    }
    else if( control == IOBUFCTRL_DESC ) {
	*(char**)buf = "encrypt_filter";
    }
    return rc;
}


/****************
 * Write pubkey-enc packets from the list of PKs to OUT.
 */
static int
write_pubkey_enc_from_list( PK_LIST pk_list, DEK *dek, IOBUF out )
{
    PACKET pkt;
    PKT_public_key *pk;
    PKT_pubkey_enc  *enc;
    int rc;

    for( ; pk_list; pk_list = pk_list->next ) {
	MPI frame;

	pk = pk_list->pk;

	print_pubkey_algo_note( pk->pubkey_algo );
	enc = gcry_xcalloc( 1, sizeof *enc );
	enc->pubkey_algo = pk->pubkey_algo;
	keyid_from_pk( pk, enc->keyid );
	enc->throw_keyid = opt.throw_keyid;

	/* Okay, what's going on: We have the session key somewhere in
	 * the structure DEK and want to encode this session key in
	 * an integer value of n bits.	pubkey_nbits gives us the
	 * number of bits we have to use.  We then encode the session
	 * key in some way and we get it back in the big intger value
	 * FRAME.  Then we use FRAME, the public key PK->PKEY and the
	 * algorithm number PK->PUBKEY_ALGO and pass it to pubkey_encrypt
	 * which returns the encrypted value in the array ENC->DATA.
	 * This array has a size which depends on the used algorithm
	 * (e.g. 2 for ElGamal).  We don't need frame anymore because we
	 * have everything now in enc->data which is the passed to
	 * build_packet()
	 */
	frame = encode_session_key( dek, pubkey_nbits( pk->pubkey_algo,
							  pk->pkey ) );
	rc = pk_encrypt( pk->pubkey_algo, enc->data, frame, pk->pkey );
	mpi_release( frame );
	if( rc )
	    log_error("pubkey_encrypt failed: %s\n", gpg_errstr(rc) );
	else {
	    if( opt.verbose ) {
		char *ustr = get_user_id_string_native( enc->keyid );
		log_info(_("%s/%s encrypted for: %s\n"),
		    gcry_pk_algo_name(enc->pubkey_algo),
		    gcry_cipher_algo_name(dek->algo), ustr );
		gcry_free(ustr);
	    }
	    /* and write it */
	    init_packet(&pkt);
	    pkt.pkttype = PKT_PUBKEY_ENC;
	    pkt.pkt.pubkey_enc = enc;
	    rc = build_packet( out, &pkt );
	    if( rc )
	       log_error("build_packet(pubkey_enc) failed: %s\n", gpg_errstr(rc));
	}
	free_pubkey_enc(enc);
	if( rc )
	    return rc;
    }
    return 0;
}