VeraCrypt Rescue Disk for MBR legacy boot mode on USB Stick

• Download the required files from the official SourceForge repository of VeraCrypt: https://sourceforge.net/projects/veracrypt/files/Contributions/VeraCryptUsbRescueDisk.zip
• Insert a USB drive.
• Format the USB drive with FAT16 oder FAT32:
  • Launch usb_format.exe as an administrator (right click "Run as Administrator").
  • Select your USB drive in the Device list.
  • Choose FAT as filesystem and check "Quick Format". Click Start.
• Create a bootloader which can start up an iso image:
  • Launch grubinst_gui.exe.
  • Check "Disk" and then select your USB drive in the list.
  • Click the "Refresh" button in front of "Part List" and then choose "Whole disk (MBR)".
  • Leave all other options unchanged and then click "Install".
  • You should see an console window that reads "The MBR/BS has been successfully installed. Press <ENTER> to continue ..."
  • Close the tool.
• Copy the file "grldr" to your USB drive at the root (e.g. if the drive letter is I:, you should have I:\grldr). This file loads Grub4Dos.
• Copy the file "menu.lst" to your USB drive at the root (e.g. if the drive letter is I:, you should have I:\menu.lst). This file configures the shown menu and its options.
• Copy the rescue disk file "VeraCrypt Rescue Disk.iso" to the USB drive at the root and rename it "veracrypt.iso". Another possibility is to change the link in the "menu.lst" file.

/*
  zip_close.c -- close zip archive and update changes
  Copyright (C) 1999-2016 Dieter Baron and Thomas Klausner

  This file is part of libzip, a library to manipulate ZIP archives.
  The authors can be contacted at <libzip@nih.at>

  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions
  are met:
  1. Redistributions of source code must retain the above copyright
     notice, this list of conditions and the following disclaimer.
  2. Redistributions in binary form must reproduce the above copyright
     notice, this list of conditions and the following disclaimer in
     the documentation and/or other materials provided with the
     distribution.
  3. The names of the authors may not be used to endorse or promote
     products derived from this software without specific prior
     written permission.
 
  THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS
  OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
  DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
  GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
  IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
  OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
  IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/


#include "zipint.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifdef HAVE_STRINGS_H
#include <strings.h>
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <sys/types.h>
#include <sys/stat.h>
#ifdef _WIN32
#include <io.h>
#include <fcntl.h>
#endif


/* max deflate size increase: size + ceil(size/16k)*5+6 */
#define MAX_DEFLATE_SIZE_32	4293656963u

static int add_data(zip_t *, zip_source_t *, zip_dirent_t *);
static int copy_data(zip_t *, zip_uint64_t);
static int copy_source(zip_t *, zip_source_t *);
static int write_cdir(zip_t *, const zip_filelist_t *, zip_uint64_t);


ZIP_EXTERN int
zip_close(zip_t *za)
{
    zip_uint64_t i, j, survivors;
    zip_int64_t off;
    int error;
    zip_filelist_t *filelist;
    int changed;

    if (za == NULL)
	return -1;

    changed = _zip_changed(za, &survivors);

    /* don't create zip files with no entries */
    if (survivors == 0) {
	if ((za->open_flags & ZIP_TRUNCATE) || changed) {
	    if (zip_source_remove(za->src) < 0) {
		_zip_error_set_from_source(&za->error, za->src);
		return -1;
	    }
	}
	zip_discard(za);
	return 0;
    }	       

    if (!changed) {
	zip_discard(za);
	return 0;
    }

    if (survivors > za->nentry) {
        zip_error_set(&za->error, ZIP_ER_INTERNAL, 0);
        return -1;
    }
    
    if ((filelist=(zip_filelist_t *)malloc(sizeof(filelist[0])*(size_t)survivors)) == NULL)
	return -1;

    /* create list of files with index into original archive  */
    for (i=j=0; i<za->nentry; i++) {
	if (za->entry[i].deleted)
	    continue;

        if (j >= survivors) {
            free(filelist);
            zip_error_set(&za->error, ZIP_ER_INTERNAL, 0);
            return -1;
        }
        
	filelist[j].idx = i;
	j++;
    }
    if (j < survivors) {
        free(filelist);
        zip_error_set(&za->error, ZIP_ER_INTERNAL, 0);
        return -1;
    }

    if (zip_source_begin_write(za->src) < 0) {
	_zip_error_set_from_source(&za->error, za->src);
	free(filelist);
	return -1;
    }
    
    error = 0;
    for (j=0; j<survivors; j++) {
	int new_data;
	zip_entry_t *entry;
	zip_dirent_t *de;

	if (za->progress_callback) {
	    za->progress_callback((double)j/survivors);
	}

	i = filelist[j].idx;
	entry = za->entry+i;

	new_data = (ZIP_ENTRY_DATA_CHANGED(entry) || ZIP_ENTRY_CHANGED(entry, ZIP_DIRENT_COMP_METHOD) || ZIP_ENTRY_CHANGED(entry, ZIP_DIRENT_ENCRYPTION_METHOD));

	/* create new local directory entry */
	if (entry->changes == NULL) {
	    if ((entry->changes=_zip_dirent_clone(entry->orig)) == NULL) {
                zip_error_set(&za->error, ZIP_ER_MEMORY, 0);
                error = 1;
                break;
	    }
	}
	de = entry->changes;

	if (_zip_read_local_ef(za, i) < 0) {
	    error = 1;
	    break;
	}

        if ((off = zip_source_tell_write(za->src)) < 0) {
            error = 1;
            break;
        }
        de->offset = (zip_uint64_t)off;

	if (new_data) {
	    zip_source_t *zs;

	    zs = NULL;
	    if (!ZIP_ENTRY_DATA_CHANGED(entry)) {
		if ((zs=_zip_source_zip_new(za, za, i, ZIP_FL_UNCHANGED, 0, 0, NULL)) == NULL) {
		    error = 1;
		    break;
		}
	    }

	    /* add_data writes dirent */
	    if (add_data(za, zs ? zs : entry->source, de) < 0) {
		error = 1;
		if (zs)
		    zip_source_free(zs);
		break;
	    }
	    if (zs)
		zip_source_free(zs);
	}
	else {
	    zip_uint64_t offset;

	    /* when copying data, all sizes are known -> no data descriptor needed */
	    de->bitflags &= (zip_uint16_t)~ZIP_GPBF_DATA_DESCRIPTOR;
	    if (_zip_dirent_write(za, de, ZIP_FL_LOCAL) < 0) {
		error = 1;
		break;
	    }
	    if ((offset=_zip_file_get_offset(za, i, &za->error)) == 0) {
		error = 1;
		break;
	    }
	    if (zip_source_seek(za->src, (zip_int64_t)offset, SEEK_SET) < 0) {
		_zip_error_set_from_source(&za->error, za->src);
		error = 1;
		break;
	    }
	    if (copy_data(za, de->comp_size) < 0) {
		error = 1;
		break;
	    }
	}
    }

    if (!error) {
	if (write_cdir(za, filelist, survivors) < 0)
	    error = 1;
    }

    free(filelist);

    if (!error) {
	if (zip_source_commit_write(za->src) != 0) {
	    _zip_error_set_from_source(&za->error, za->src);
	    error = 1;
	}
    }

    if (error) {
	zip_source_rollback_write(za->src);
	return -1;
    }

    if (za->progress_callback) {
	za->progress_callback(1);
    }

    zip_discard(za);
    
    return 0;
}


static int
add_data(zip_t *za, zip_source_t *src, zip_dirent_t *de)
{
    zip_int64_t offstart, offdata, offend;
    struct zip_stat st;
    zip_source_t *src_final, *src_tmp;
    int ret;
    int is_zip64;
    zip_flags_t flags;
    bool needs_recompress, needs_decompress, needs_crc, needs_compress, needs_reencrypt, needs_decrypt, needs_encrypt;
    
    if (zip_source_stat(src, &st) < 0) {
	_zip_error_set_from_source(&za->error, src);
	return -1;
    }

    if ((st.valid & ZIP_STAT_COMP_METHOD) == 0) {
	st.valid |= ZIP_STAT_COMP_METHOD;
	st.comp_method = ZIP_CM_STORE;
    }

    if (ZIP_CM_IS_DEFAULT(de->comp_method) && st.comp_method != ZIP_CM_STORE)
	de->comp_method = st.comp_method;
    else if (de->comp_method == ZIP_CM_STORE && (st.valid & ZIP_STAT_SIZE)) {
	st.valid |= ZIP_STAT_COMP_SIZE;
	st.comp_size = st.size;
    }
    else {
	/* we'll recompress */
	st.valid &= ~ZIP_STAT_COMP_SIZE;
    }

    if ((st.valid & ZIP_STAT_ENCRYPTION_METHOD) == 0) {
	st.valid |= ZIP_STAT_ENCRYPTION_METHOD;
	st.encryption_method = ZIP_EM_NONE;
    }

    flags = ZIP_EF_LOCAL;

    if ((st.valid & ZIP_STAT_SIZE) == 0)
	flags |= ZIP_FL_FORCE_ZIP64;
    else {
	de->uncomp_size = st.size;
	
	if ((st.valid & ZIP_STAT_COMP_SIZE) == 0) {
	    if (( ((de->comp_method == ZIP_CM_DEFLATE || ZIP_CM_IS_DEFAULT(de->comp_method)) && st.size > MAX_DEFLATE_SIZE_32)
		  || (de->comp_method != ZIP_CM_STORE && de->comp_method != ZIP_CM_DEFLATE && !ZIP_CM_IS_DEFAULT(de->comp_method))))
		flags |= ZIP_FL_FORCE_ZIP64;
	}
	else
	    de->comp_size = st.comp_size;
    }

    if ((offstart = zip_source_tell_write(za->src)) < 0) {
        return -1;
    }

    /* as long as we don't support non-seekable output, clear data descriptor bit */
    de->bitflags &= (zip_uint16_t)~ZIP_GPBF_DATA_DESCRIPTOR;
    if ((is_zip64=_zip_dirent_write(za, de, flags)) < 0)
	return -1;

    needs_recompress = !((st.comp_method == de->comp_method) || (ZIP_CM_IS_DEFAULT(de->comp_method) && st.comp_method == ZIP_CM_DEFLATE));
    needs_decompress = needs_recompress && (st.comp_method != ZIP_CM_STORE);
    needs_crc = (st.comp_method == ZIP_CM_STORE) || needs_decompress;
    needs_compress = needs_recompress && (de->comp_method != ZIP_CM_STORE);

    needs_reencrypt = needs_recompress || (de->changed & ZIP_DIRENT_PASSWORD) || (de->encryption_method != st.encryption_method);
    needs_decrypt = needs_reencrypt && (st.encryption_method != ZIP_EM_NONE);
    needs_encrypt = needs_reencrypt && (de->encryption_method != ZIP_EM_NONE);

    src_final = src;
    zip_source_keep(src_final);

    if (needs_decrypt) {
	zip_encryption_implementation impl;
	
	if ((impl = _zip_get_encryption_implementation(st.encryption_method, ZIP_CODEC_DECODE)) == NULL) {
	    zip_error_set(&za->error, ZIP_ER_ENCRNOTSUPP, 0);
	    zip_source_free(src_final);
	    return -1;
	}
	if ((src_tmp = impl(za, src_final, st.encryption_method, ZIP_CODEC_DECODE, za->default_password)) == NULL) {
	    /* error set by impl */
	    zip_source_free(src_final);
	    return -1;
	}

	zip_source_free(src_final);
	src_final = src_tmp;
    }
    
    if (needs_decompress) {
	zip_compression_implementation comp_impl;
	
	if ((comp_impl = _zip_get_compression_implementation(st.comp_method, ZIP_CODEC_DECODE)) == NULL) {
	    zip_error_set(&za->error, ZIP_ER_COMPNOTSUPP, 0);
	    zip_source_free(src_final);
	    return -1;
	}
	if ((src_tmp = comp_impl(za, src_final, st.comp_method, ZIP_CODEC_DECODE)) == NULL) {
	    /* error set by comp_impl */
	    zip_source_free(src_final);
	    return -1;
	}

	zip_source_free(src_final);
	src_final = src_tmp;
    }

    if (needs_crc) {
	if ((src_tmp = zip_source_crc(za, src_final, 0)) == NULL) {
	    zip_source_free(src_final);
	    return -1;
	}

	zip_source_free(src_final);
	src_final = src_tmp;
    }

    if (needs_compress) {
	zip_compression_implementation comp_impl;

	if ((comp_impl = _zip_get_compression_implementation(de->comp_method, ZIP_CODEC_ENCODE)) == NULL) {
	    zip_error_set(&za->error, ZIP_ER_COMPNOTSUPP, 0);
	    zip_source_free(src_final);
	    return -1;
	}
	if ((src_tmp = comp_impl(za, src_final, de->comp_method, ZIP_CODEC_ENCODE)) == NULL) {
	    zip_source_free(src_final);
	    return -1;
	}
	
	zip_source_free(src_final);
	src_final = src_tmp;
    }

    
    if (needs_encrypt) {
	zip_encryption_implementation impl;
	const char *password = NULL;

	if (de->password) {
	    password = de->password;
	} else if (za->default_password) {
	    password = za->default_password;
	}
	
	if ((impl = _zip_get_encryption_implementation(de->encryption_method, ZIP_CODEC_ENCODE)) == NULL) {
	    zip_error_set(&za->error, ZIP_ER_ENCRNOTSUPP, 0);
	    zip_source_free(src_final);
	    return -1;
	}
	if ((src_tmp = impl(za, src_final, de->encryption_method, ZIP_CODEC_ENCODE, password)) == NULL) {
	    /* error set by impl */
	    zip_source_free(src_final);
	    return -1;
	}

	zip_source_free(src_final);
	src_final = src_tmp;
    }


    if ((offdata = zip_source_tell_write(za->src)) < 0) {
        return -1;
    }

    ret = copy_source(za, src_final);
	
    if (zip_source_stat(src_final, &st) < 0) {
	ret = -1;
    }

    zip_source_free(src_final);

    if (ret < 0) {
	return -1;
    }

    if ((offend = zip_source_tell_write(za->src)) < 0) {
        return -1;
    }

    if (zip_source_seek_write(za->src, offstart, SEEK_SET) < 0) {
	_zip_error_set_from_source(&za->error, za->src);
	return -1;
    }

    if ((st.valid & (ZIP_STAT_COMP_METHOD|ZIP_STAT_CRC|ZIP_STAT_SIZE)) != (ZIP_STAT_COMP_METHOD|ZIP_STAT_CRC|ZIP_STAT_SIZE)) {
	zip_error_set(&za->error, ZIP_ER_INTERNAL, 0);
	return -1;
    }

    if ((de->changed & ZIP_DIRENT_LAST_MOD) == 0) {
        if (st.valid & ZIP_STAT_MTIME)
            de->last_mod = st.mtime;
        else
            time(&de->last_mod);
    }
    de->comp_method = st.comp_method;
    de->crc = st.crc;
    de->uncomp_size = st.size;
    de->comp_size = (zip_uint64_t)(offend - offdata);

    if ((ret=_zip_dirent_write(za, de, flags)) < 0)
	return -1;
 
    if (is_zip64 != ret) {
	/* Zip64 mismatch between preliminary file header written before data and final file header written afterwards */
	zip_error_set(&za->error, ZIP_ER_INTERNAL, 0);
	return -1;
    }

   
    if (zip_source_seek_write(za->src, offend, SEEK_SET) < 0) {
	_zip_error_set_from_source(&za->error, za->src);
	return -1;
    }

    return 0;
}


static int
copy_data(zip_t *za, zip_uint64_t len)
{
    zip_uint8_t buf[BUFSIZE];
    size_t n;

    while (len > 0) {
	n = len > sizeof(buf) ? sizeof(buf) : len;
	if (_zip_read(za->src, buf, n, &za->error) < 0) {
	    return -1;
	}

	if (_zip_write(za, buf, n) < 0) {
	    return -1;
	}
	
	len -= n;
    }

    return 0;
}


static int
copy_source(zip_t *za, zip_source_t *src)
{
    zip_uint8_t buf[BUFSIZE];
    zip_int64_t n;
    int ret;

    if (zip_source_open(src) < 0) {
	_zip_error_set_from_source(&za->error, src);
	return -1;
    }

    ret = 0;
    while ((n=zip_source_read(src, buf, sizeof(buf))) > 0) {
	if (_zip_write(za, buf, (zip_uint64_t)n) < 0) {
	    ret = -1;
	    break;
	}
    }
    
    if (n < 0) {
	_zip_error_set_from_source(&za->error, src);
	ret = -1;
    }

    zip_source_close(src);
    
    return ret;
}


static int
write_cdir(zip_t *za, const zip_filelist_t *filelist, zip_uint64_t survivors)
{
    zip_int64_t cd_start, end, size;
    
    if ((cd_start = zip_source_tell_write(za->src)) < 0) {
        return -1;
    }

    if ((size=_zip_cdir_write(za, filelist, survivors)) < 0) {
	return -1;
    }
    
    if ((end = zip_source_tell_write(za->src)) < 0) {
        return -1;
    }

    return 0;
}


int
_zip_changed(const zip_t *za, zip_uint64_t *survivorsp)
{
    int changed;
    zip_uint64_t i, survivors;

    changed = 0;
    survivors = 0;

    if (za->comment_changed || za->ch_flags != za->flags)
	changed = 1;

    for (i=0; i<za->nentry; i++) {
	if (za->entry[i].deleted || za->entry[i].source || (za->entry[i].changes && za->entry[i].changes->changed != 0))
	    changed = 1;
	if (!za->entry[i].deleted)
	    survivors++;
    }

    if (survivorsp)
	*survivorsp = survivors;

    return changed;
}