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/*
File: file_gif.c
Copyright (C) 1998-2007 Christophe GRENIER <grenier@cgsecurity.org>
This software 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.
This program 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 the Free Software Foundation, Inc., 51
Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#if !defined(SINGLE_FORMAT) || defined(SINGLE_FORMAT_gif)
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#ifdef HAVE_STRING_H
#include <string.h>
#endif
#include <stdio.h>
#include "types.h"
#include "filegen.h"
#include "log.h"
/*@ requires valid_register_header_check(file_stat); */
static void register_header_check_gif(file_stat_t *file_stat);
static data_check_t data_check_gif2(const unsigned char *buffer, const unsigned int buffer_size, file_recovery_t *file_recovery);
const file_hint_t file_hint_gif= {
.extension="gif",
.description="Graphic Interchange Format",
.max_filesize=PHOTOREC_MAX_FILE_SIZE,
.recover=1,
.enable_by_default=1,
.register_header_check=®ister_header_check_gif
};
/*@
@ requires file_recovery->file_check == &file_check_gif;
@ requires valid_file_check_param(file_recovery);
@ ensures valid_file_check_result(file_recovery);
@ assigns *file_recovery->handle, errno, file_recovery->file_size;
@ assigns Frama_C_entropy_source;
@*/
static void file_check_gif(file_recovery_t *file_recovery)
{
const char gif_footer[2]= {0x00, 0x3b};
char buffer[2];
/* file_recovery->calculated_file_size is always >= */
if(file_recovery->calculated_file_size < 2 ||
file_recovery->calculated_file_size >= 0x8000000000000000 ||
my_fseek(file_recovery->handle, file_recovery->calculated_file_size-2, SEEK_SET)<0 ||
fread(buffer, 2, 1, file_recovery->handle)!=1)
{
file_recovery->file_size=0;
return;
}
#ifdef __FRAMAC__
Frama_C_make_unknown(&buffer, sizeof(buffer));
#endif
if(memcmp(buffer, gif_footer, sizeof(gif_footer))!=0)
{
file_recovery->file_size=0;
return;
}
file_recovery->file_size=file_recovery->calculated_file_size;
}
/*@
@ requires file_recovery->data_check==&data_check_gif;
@ requires valid_data_check_param(buffer, buffer_size, file_recovery);
@ ensures valid_data_check_result(\result, file_recovery);
@ ensures file_recovery->data_check == &data_check_gif || file_recovery->data_check == &data_check_gif2;
@ assigns file_recovery->calculated_file_size, file_recovery->data_check;
@*/
static data_check_t data_check_gif(const unsigned char *buffer, const unsigned int buffer_size, file_recovery_t *file_recovery)
{
/*@ assert file_recovery->calculated_file_size <= PHOTOREC_MAX_FILE_SIZE; */
/*@ assert file_recovery->file_size <= PHOTOREC_MAX_FILE_SIZE; */
if(file_recovery->calculated_file_size + buffer_size/2 >= file_recovery->file_size &&
file_recovery->calculated_file_size + 1 < file_recovery->file_size + buffer_size/2)
{
const unsigned int i=file_recovery->calculated_file_size + buffer_size/2 - file_recovery->file_size;
/*@ assert 0 <= i < buffer_size - 1; */
#ifdef DEBUG_GIF
log_info("data_check_gif calculated_file_size=0x%llx: 0x%02x\n",
(long long unsigned)file_recovery->calculated_file_size, buffer[i]);
#endif
switch(buffer[i])
{
case 0x21:
/* Plain Text Extension 21 01 ... */
/* Graphic Control Extension 21 f9 04 XX XX XX XX 00 */
/* Comment Extension 21 fe ... */
/* Application Extension 21 ff */
file_recovery->calculated_file_size+=2;
if(file_recovery->calculated_file_size >= PHOTOREC_MAX_FILE_SIZE)
return DC_STOP;
/*@ assert file_recovery->calculated_file_size < PHOTOREC_MAX_FILE_SIZE; */
file_recovery->data_check=&data_check_gif2;
return data_check_gif2(buffer, buffer_size, file_recovery);
case 0x2c:
if(i + 20 < buffer_size)
{
unsigned int j=10+1;
/* 1 Image Descriptor id=0x2c
* 4: NW corner
* 4: width, heigth,
* 1: is a local color table present ? */
if(((buffer[i+9]>>7)&0x1)>0)
{
/* local color table */
j+=3<<((buffer[i+9]&7)+1);
}
file_recovery->calculated_file_size+=j;
/* 1: Start of image - LZW minimum code size */
/* Table Based Image Data */
if(file_recovery->calculated_file_size >= PHOTOREC_MAX_FILE_SIZE)
return DC_STOP;
file_recovery->data_check=&data_check_gif2;
return data_check_gif2(buffer, buffer_size, file_recovery);
}
return DC_CONTINUE;
case 0x3b:
/* Trailer */
file_recovery->calculated_file_size++;
return DC_STOP;
default:
return DC_ERROR;
}
}
return DC_CONTINUE;
}
/*@
@ requires file_recovery->data_check==&data_check_gif2;
@ requires valid_data_check_param(buffer, buffer_size, file_recovery);
@ ensures valid_data_check_result(\result, file_recovery);
@ ensures file_recovery->data_check == &data_check_gif || file_recovery->data_check == &data_check_gif2;
@ assigns file_recovery->calculated_file_size, file_recovery->data_check;
@*/
static data_check_t data_check_gif2(const unsigned char *buffer, const unsigned int buffer_size, file_recovery_t *file_recovery)
{
/*@ assert file_recovery->calculated_file_size <= PHOTOREC_MAX_FILE_SIZE; */
/*@ assert file_recovery->file_size <= PHOTOREC_MAX_FILE_SIZE; */
/*@
@ loop invariant file_recovery->data_check == &data_check_gif || file_recovery->data_check == &data_check_gif2;
@ loop assigns file_recovery->calculated_file_size, file_recovery->data_check;
@ loop variant file_recovery->file_size + buffer_size/2 - (file_recovery->calculated_file_size + 1);
@*/
while(file_recovery->calculated_file_size + buffer_size/2 >= file_recovery->file_size &&
file_recovery->calculated_file_size + 1 < file_recovery->file_size + buffer_size/2)
{
const unsigned int i=file_recovery->calculated_file_size + buffer_size/2 - file_recovery->file_size;
/*@ assert file_recovery->data_check==&data_check_gif2; */
/*@ assert 0 <= i < buffer_size - 1; */
#ifdef DEBUG_GIF
log_info("data_check_gif2 calculated_file_size=0x%llx\n",
(long long unsigned)file_recovery->calculated_file_size);
#endif
file_recovery->calculated_file_size+=(uint64_t)1+buffer[i];
if(file_recovery->calculated_file_size >= PHOTOREC_MAX_FILE_SIZE)
return DC_STOP;
/*@ assert file_recovery->calculated_file_size < PHOTOREC_MAX_FILE_SIZE; */
if(buffer[i]==0)
{
file_recovery->data_check=&data_check_gif;
return data_check_gif(buffer, buffer_size, file_recovery);
}
/*@ assert file_recovery->data_check==&data_check_gif2; */
}
/*@ assert file_recovery->data_check==&data_check_gif2; */
return DC_CONTINUE;
}
/*@
@ requires buffer_size >= 6+7+(3<<8)+1;
@ requires separation: \separated(&file_hint_gif, buffer+(..), file_recovery, file_recovery_new);
@ requires valid_header_check_param(buffer, buffer_size, safe_header_only, file_recovery, file_recovery_new);
@ terminates \true;
@ ensures valid_header_check_result(\result, file_recovery_new);
@ ensures (\result == 1) ==> file_recovery_new->file_size == 0;
@ ensures (\result == 1) ==> (file_recovery_new->extension == file_hint_gif.extension);
@ ensures (\result == 1) ==> (file_recovery_new->time == 0);
@ ensures (\result == 1 && file_recovery_new->blocksize>=2) ==> (file_recovery_new->calculated_file_size >= 6+7);
@ ensures (\result == 1 && file_recovery_new->blocksize>=2) ==> (file_recovery_new->data_check == &data_check_gif);
@ ensures (\result == 1 && file_recovery_new->blocksize>=2) ==> (file_recovery_new->file_check == &file_check_gif);
@ assigns *file_recovery_new;
@*/
static int header_check_gif(const unsigned char *buffer, const unsigned int buffer_size, const unsigned int safe_header_only, const file_recovery_t *file_recovery, file_recovery_t *file_recovery_new)
{
uint64_t offset;
offset=6; /* Header */
offset+=7; /* Logical Screen Descriptor */
if((buffer[10]>>7)&0x1)
{
/* Global Color Table */
offset+=3<<((buffer[10]&7)+1);
}
if(offset < buffer_size && buffer[offset]!=0x21 && buffer[offset]!=0x2c)
return 0;
reset_file_recovery(file_recovery_new);
file_recovery_new->extension=file_hint_gif.extension;
file_recovery_new->min_filesize=42;
if(file_recovery_new->blocksize < 2)
return 1;
file_recovery_new->calculated_file_size=offset;
file_recovery_new->file_check=&file_check_gif;
file_recovery_new->data_check=&data_check_gif;
return 1;
}
static void register_header_check_gif(file_stat_t *file_stat)
{
static const unsigned char gif_header[6]= { 'G','I','F','8','7','a'};
static const unsigned char gif_header2[6]= { 'G','I','F','8','9','a'};
register_header_check(0, gif_header,sizeof(gif_header), &header_check_gif, file_stat);
#ifndef DISABLED_FOR_FRAMAC
register_header_check(0, gif_header2,sizeof(gif_header2), &header_check_gif, file_stat);
#endif
}
#endif
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