gnupg/g10/encode.c

/* encode.c - encode data
 * Copyright (C) 1998, 1999, 2000, 2001, 2002 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 "memory.h"
#include "util.h"
#include "main.h"
#include "filter.h"
#include "trustdb.h"
#include "i18n.h"
#include "status.h"

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



/****************
 * Encode FILENAME with only the symmetric cipher.  Take input from
 * stdin if FILENAME is NULL.
 */
int
encode_symmetric( const char *filename )
{
    int compat = 1;
    
    if ( opt.expert )
        compat = 0; /* PGP knows how to handle this mode. */
    return encode_simple( filename, 1, compat );
}

/****************
 * 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, 1 );
}

static void
encode_sesskey( DEK *dek, DEK **ret_dek, byte *enckey )
{
    CIPHER_HANDLE hd;
    DEK *c;
    byte buf[33];

    assert ( dek->keylen < 32 );
    
    c = m_alloc_clear( sizeof *c );
    c->keylen = dek->keylen;
    c->algo = dek->algo;
    make_session_key( c );
    /*log_hexdump( "thekey", c->key, c->keylen );*/

    buf[0] = c->algo;
    memcpy( buf + 1, c->key, c->keylen );
    
    hd = cipher_open( dek->algo, CIPHER_MODE_CFB, 1 );
    cipher_setkey( hd, dek->key, dek->keylen );
    cipher_setiv( hd, NULL, 0 );
    cipher_encrypt( hd, buf, buf, c->keylen + 1 );
    cipher_close( hd );

    memcpy( enckey, buf, c->keylen + 1 );
    memset( buf, 0, sizeof buf ); /* burn key */
    *ret_dek = c;
}

static int
encode_simple( const char *filename, int mode, int compat )
{
    IOBUF inp, out;
    PACKET pkt;
    DEK *dek = NULL;
    PKT_plaintext *pt = NULL;
    STRING2KEY *s2k = NULL;
    byte enckey[33];
    int rc = 0;
    int seskeylen = 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);
    
    if (opt.compress == -1 && is_file_compressed(filename, &rc))
      {
        if (opt.verbose)
          log_info(_("`%s' already compressed\n"), filename);
        do_compress = 0;        
      }
    if (rc)
        return rc;

    /* prepare iobufs */
    if( !(inp = iobuf_open(filename)) ) {
	log_error(_("%s: can't open: %s\n"), filename? filename: "[stdin]",
					strerror(errno) );
	return G10ERR_OPEN_FILE;
    }

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

    /* Due the the fact that we use don't use an IV to encrypt the
       session key we can't use the new mode with RFC1991 because
       it has no S2K salt. RFC1991 always uses simple S2K. */
    if ( opt.rfc1991 && !compat )
        compat = 1;
    
    cfx.dek = NULL;
    if( mode ) {
	s2k = m_alloc_clear( 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, NULL );
	if( !cfx.dek || !cfx.dek->keylen ) {
	    rc = G10ERR_PASSPHRASE;
	    m_free(cfx.dek);
	    m_free(s2k);
	    iobuf_close(inp);
	    log_error(_("error creating passphrase: %s\n"), g10_errstr(rc) );
	    return rc;
	}
        if ( !compat ) {            
            seskeylen = cipher_get_keylen( opt.def_cipher_algo ?
                                           opt.def_cipher_algo:
                                           opt.s2k_cipher_algo ) / 8;
            encode_sesskey( cfx.dek, &dek, enckey );
            m_free( cfx.dek ); cfx.dek = dek;
        }
    }

    if( (rc = open_outfile( filename, opt.armor? 1:0, &out )) ) {
	iobuf_cancel(inp);
	m_free(cfx.dek);
	m_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 = m_alloc_clear( sizeof *enc + seskeylen + 1 );
	enc->version = 4;
	enc->cipher_algo = cfx.dek->algo;
	enc->s2k = *s2k;
        if ( !compat && seskeylen ) {
            enc->seskeylen = seskeylen + 1; /* algo id */
            memcpy( enc->seskey, enckey, seskeylen + 1 );
        }
	pkt.pkttype = PKT_SYMKEY_ENC;
	pkt.pkt.symkey_enc = enc;
	if( (rc = build_packet( out, &pkt )) )
	    log_error("build symkey packet failed: %s\n", g10_errstr(rc) );
	m_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 = m_alloc( sizeof *pt + strlen(s) - 1 );
	    pt->namelen = strlen(s);
	    memcpy(pt->name, s, pt->namelen );
	    m_free(s);
	}
	else { /* no filename */
	    pt = m_alloc( sizeof *pt - 1 );
	    pt->namelen = 0;
	}
    }

    /* Note that PGP 5 has problems decrypting symmetrically encrypted
       data if the file length is in the inner packet. It works when
       only partial length headers are use.  In the past, we always
       used partial body length here, but since PGP 2, PGP 6, and PGP
       7 need the file length, and nobody should be using PGP 5
       nowadays anyway, this is now set to the file length.  Note also
       that this only applies to the RFC-1991 style symmetric
       messages, and not the RFC-2440 style.  PGP 6 and 7 work with
       either partial length or fixed length with the new style
       messages. */

    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;
	cfx.datalen = filesize && !do_compress ? calc_packet_length( &pkt ) : 0;
    }
    else
      {
        cfx.datalen = filesize && !do_compress ? filesize : 0;
        pkt.pkttype = 0;
        pkt.pkt.generic = NULL;
      }

    /* 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", g10_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 = G10ERR_WRITE_FILE;
		log_error("copying input to output failed: %s\n", g10_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 (mode)
            write_status( STATUS_END_ENCRYPTION );
    }
    if (pt)
	pt->buf = NULL;
    free_packet(&pkt);
    m_free(cfx.dek);
    m_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, rc2 = 0;
    u32 filesize;
    cipher_filter_context_t cfx;
    armor_filter_context_t afx;
    compress_filter_context_t zfx;
    text_filter_context_t tfx;
    PK_LIST pk_list,work_list;
    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);

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

    if(opt.pgp2) {
      for(work_list=pk_list; work_list; work_list=work_list->next)
	if(!(is_RSA(work_list->pk->pubkey_algo) &&
	     nbits_from_pk(work_list->pk)<=2048))
	  {
	    log_info(_("you can only encrypt to RSA keys of 2048 bits or "
		       "less in --pgp2 mode\n"));
	    log_info(_("this message may not be usable by PGP 2.x\n"));
	    opt.pgp2=0;
	    break;
	  }
    }

    if (opt.compress == -1 && is_file_compressed(filename, &rc2))
      {
        if (opt.verbose)
          log_info(_("`%s' already compressed\n"), filename);
        do_compress = 0;        
      }
    if (rc2)
      {
        rc = rc2;
        goto leave;
      }
    
    /* prepare iobufs */
    if( !(inp = iobuf_open(filename)) ) {
	log_error(_("can't open %s: %s\n"), filename? filename: "[stdin]",
					strerror(errno) );
	rc = G10ERR_OPEN_FILE;
	goto leave;
    }
    else if( opt.verbose )
	log_info(_("reading from `%s'\n"), filename? filename: "[stdin]");

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

    if( (rc = open_outfile( filename, opt.armor? 1:0, &out )) )
	goto leave;


    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
    /* create a session key */
    cfx.dek = m_alloc_secure_clear (sizeof *cfx.dek);
    if( !opt.def_cipher_algo ) { /* try to get it from the prefs */
	cfx.dek->algo = select_algo_from_prefs( pk_list, PREFTYPE_SYM, NULL );
	/* The only way select_algo_from_prefs can fail here is when
           mixing v3 and v4 keys, as v4 keys have an implicit
           preference entry for 3DES, and the pk_list cannot be empty.
           In this case, use 3DES anyway as it's the safest choice -
           perhaps the v3 key is being used in an OpenPGP
           implementation and we know that the implementation behind
           any v4 key can handle 3DES. */
	if( cfx.dek->algo == -1 ) {
	    cfx.dek->algo = CIPHER_ALGO_3DES;

	    if( opt.pgp2 ) {
	      log_info(_("unable to use the IDEA cipher for all of the keys "
			 "you are encrypting to.\n"));
	      log_info(_("this message may not be usable by PGP 2.x\n"));
	      opt.pgp2=0;
	    }
	}
    }
    else
	cfx.dek->algo = opt.def_cipher_algo;
    cfx.dek->use_mdc = select_mdc_from_pklist (pk_list);

    make_session_key( cfx.dek );
    if( DBG_CIPHER )
	log_hexdump("DEK is: ", cfx.dek->key, cfx.dek->keylen );

    rc = write_pubkey_enc_from_list( pk_list, cfx.dek, out );
    if( rc  )
	goto leave;

    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 = m_alloc( sizeof *pt + strlen(s) - 1 );
	    pt->namelen = strlen(s);
	    memcpy(pt->name, s, pt->namelen );
	    m_free(s);
	}
	else { /* no filename */
	    pt = m_alloc( 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 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 */
    iobuf_push_filter( out, cipher_filter, &cfx );

    /* register the compress filter */
    if( do_compress ) {
	int compr_algo = opt.def_compress_algo;

	if(compr_algo==-1)
	  {
	    if((compr_algo=
		select_algo_from_prefs(pk_list,PREFTYPE_ZIP,NULL))==-1)
	      compr_algo=DEFAULT_COMPRESS_ALGO;
	  }

	/* algo 0 means no compression */
	if( compr_algo )
	  {
	    zfx.algo = compr_algo;
	    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", g10_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 = G10ERR_WRITE_FILE;
		log_error("copying input to output failed: %s\n", g10_errstr(rc) );
		break;
	    }
	memset(copy_buffer, 0, 4096); /* burn buffer */
    }

    /* finish the stuff */
  leave:
    iobuf_close(inp);
    if( rc )
	iobuf_cancel(out);
    else {
	iobuf_close(out); /* fixme: check returncode */
        write_status( STATUS_END_ENCRYPTION );
    }
    if( pt )
	pt->buf = NULL;
    free_packet(&pkt);
    m_free(cfx.dek);
    release_pk_list( pk_list );
    return rc;
}




/****************
 * Filter to do a complete 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 = m_alloc_secure_clear( 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, NULL );
		if( efx->cfx.dek->algo == -1 ) {
                    /* because 3DES is implicitly in the prefs, this can only
                     * happen if we do not have any public keys in the list */
		    efx->cfx.dek->algo = DEFAULT_CIPHER_ALGO;
                }
	    }
	    else
		efx->cfx.dek->algo = opt.def_cipher_algo;

            efx->cfx.dek->use_mdc = select_mdc_from_pklist (efx->pk_list);

	    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 = m_alloc_clear( 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 = pubkey_encrypt( pk->pubkey_algo, enc->data, frame, pk->pkey );
	mpi_free( frame );
	if( rc )
	    log_error("pubkey_encrypt failed: %s\n", g10_errstr(rc) );
	else {
	    if( opt.verbose ) {
		char *ustr = get_user_id_string_native( enc->keyid );
		log_info(_("%s/%s encrypted for: %s\n"),
		    pubkey_algo_to_string(enc->pubkey_algo),
		    cipher_algo_to_string(dek->algo), ustr );
		m_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", g10_errstr(rc));
	}
	free_pubkey_enc(enc);
	if( rc )
	    return rc;
    }
    return 0;
}

void
encode_crypt_files(int nfiles, char **files, STRLIST remusr)
{
  int rc = 0;

  if (opt.outfile)
    {
      log_error(_("--output doesn't work for this command\n"));
      return;        
    }
    
  if (!nfiles)
    {
      char line[2048];
      unsigned int lno = 0;
      while ( fgets(line, DIM(line), stdin) )
        {
          lno++;
          if (!*line || line[strlen(line)-1] != '\n')
            {
              log_error("input line %u too long or missing LF\n", lno);
              return;
            }
          line[strlen(line)-1] = '\0';
          print_file_status(STATUS_FILE_START, line, 2);
          if ( (rc = encode_crypt(line, remusr)) )
            log_error("%s: encryption failed: %s\n",
                      print_fname_stdin(line), g10_errstr(rc) );
          write_status( STATUS_FILE_DONE );
        }
    }
  else
    {
      while (nfiles--)
        {
          print_file_status(STATUS_FILE_START, *files, 2);
          if ( (rc = encode_crypt(*files, remusr)) )
            log_error("%s: encryption failed: %s\n",
                      print_fname_stdin(*files), g10_errstr(rc) );
          write_status( STATUS_FILE_DONE );
          files++;
        }
    }
}