214 lines
7.0 KiB
C
214 lines
7.0 KiB
C
/*
|
|
* Text detection based on ascmagic.c from the file(1) utility.
|
|
*
|
|
* Portions Copyright (C) 2013-2022 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
|
|
* Portions Copyright (C) 2008-2013 Sourcefire, Inc.
|
|
*
|
|
* Copyright (c) Ian F. Darwin 1986-1995.
|
|
* Software written by Ian F. Darwin and others;
|
|
* maintained 1995-present by Christos Zoulas and others.
|
|
*
|
|
* 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 immediately at the beginning of the file, without modification,
|
|
* 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.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``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 AUTHOR OR CONTRIBUTORS 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.
|
|
*/
|
|
|
|
#if HAVE_CONFIG_H
|
|
#include "clamav-config.h"
|
|
#endif
|
|
|
|
#include <stdio.h>
|
|
#include <string.h>
|
|
#include <memory.h>
|
|
#include <ctype.h>
|
|
#include <stdlib.h>
|
|
#ifdef HAVE_UNISTD_H
|
|
#include <unistd.h>
|
|
#endif
|
|
|
|
#include "clamav.h"
|
|
#include "filetypes.h"
|
|
#include "textdet.h"
|
|
#include "others.h"
|
|
|
|
#define F 0 /* character never appears in text */
|
|
#define T 1 /* character appears in plain ASCII text */
|
|
#define I 2 /* character appears in ISO-8859 text */
|
|
#define X 3 /* character appears in non-ISO extended ASCII (Mac, IBM PC) */
|
|
|
|
// clang-format off
|
|
static char text_chars[256] = {
|
|
/* BEL BS HT LF FF CR */
|
|
F, F, F, F, F, F, F, T, T, T, T, F, T, T, F, F, /* 0x0X */
|
|
/* ESC */
|
|
F, F, F, F, F, F, F, F, F, F, F, T, F, F, F, F, /* 0x1X */
|
|
T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, /* 0x2X */
|
|
T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, /* 0x3X */
|
|
T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, /* 0x4X */
|
|
T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, /* 0x5X */
|
|
T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, /* 0x6X */
|
|
T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, F, /* 0x7X */
|
|
/* NEL */
|
|
X, X, X, X, X, T, X, X, X, X, X, X, X, X, X, X, /* 0x8X */
|
|
X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, /* 0x9X */
|
|
I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, /* 0xaX */
|
|
I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, /* 0xbX */
|
|
I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, /* 0xcX */
|
|
I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, /* 0xdX */
|
|
I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, /* 0xeX */
|
|
I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I /* 0xfX */
|
|
};
|
|
// clang-format on
|
|
|
|
static int td_isascii(const unsigned char *buf, unsigned int len)
|
|
{
|
|
unsigned int i;
|
|
|
|
/* Validate that the data all falls within the bounds of
|
|
* plain ASCII, ISO-8859 text, and non-ISO extended ASCII (Mac, IBM PC)
|
|
*/
|
|
for (i = 0; i < len; i++)
|
|
if (text_chars[buf[i]] == F)
|
|
return 0;
|
|
|
|
return 1;
|
|
}
|
|
|
|
static int td_isutf8(const unsigned char *buf, unsigned int len)
|
|
{
|
|
unsigned int i, j, gotone = 0;
|
|
|
|
for (i = 0; i < len; i++) {
|
|
if ((buf[i] & 0x80) == 0) { /* 0xxxxxxx is plain ASCII */
|
|
/*
|
|
* Even if the whole file is valid UTF-8 sequences,
|
|
* still reject it if it uses weird control characters.
|
|
*/
|
|
if (text_chars[buf[i]] != T)
|
|
return 0;
|
|
|
|
} else if ((buf[i] & 0x40) == 0) { /* 10xxxxxx never 1st byte */
|
|
return 0;
|
|
} else { /* 11xxxxxx begins UTF-8 */
|
|
unsigned int following;
|
|
|
|
if ((buf[i] & 0x20) == 0) { /* 110xxxxx */
|
|
/* c = buf[i] & 0x1f; */
|
|
following = 1;
|
|
} else if ((buf[i] & 0x10) == 0) { /* 1110xxxx */
|
|
/* c = buf[i] & 0x0f; */
|
|
following = 2;
|
|
} else if ((buf[i] & 0x08) == 0) { /* 11110xxx */
|
|
/* c = buf[i] & 0x07; */
|
|
following = 3;
|
|
} else if ((buf[i] & 0x04) == 0) { /* 111110xx */
|
|
/* c = buf[i] & 0x03; */
|
|
following = 4;
|
|
} else if ((buf[i] & 0x02) == 0) { /* 1111110x */
|
|
/* c = buf[i] & 0x01; */
|
|
following = 5;
|
|
} else {
|
|
return 0;
|
|
}
|
|
|
|
for (j = 0; j < following; j++) {
|
|
if (++i >= len)
|
|
return gotone;
|
|
|
|
if ((buf[i] & 0x80) == 0 || (buf[i] & 0x40))
|
|
return 0;
|
|
|
|
/* c = (c << 6) + (buf[i] & 0x3f); */
|
|
}
|
|
|
|
gotone = 1;
|
|
}
|
|
}
|
|
|
|
return gotone;
|
|
}
|
|
|
|
static int td_isutf16(const unsigned char *buf, unsigned int len)
|
|
{
|
|
unsigned int be = 1, nobom = 0, i, c, bad = 0, high = 0;
|
|
|
|
if (len < 2)
|
|
return 0;
|
|
|
|
if (buf[0] == 0xff && buf[1] == 0xfe)
|
|
be = 0;
|
|
else if (buf[0] == 0xfe && buf[1] == 0xff)
|
|
be = 1;
|
|
else
|
|
nobom = 1;
|
|
|
|
for (i = 2; i + 1 < len; i += 2) {
|
|
if (be)
|
|
c = buf[i + 1] + 256 * buf[i];
|
|
else
|
|
c = buf[i] + 256 * buf[i + 1];
|
|
|
|
if (c == 0xfffe)
|
|
return 0;
|
|
|
|
if (c < 128 && text_chars[c] != T) {
|
|
if (nobom)
|
|
return 0;
|
|
else
|
|
bad++;
|
|
} else if (c >= 128) {
|
|
high++;
|
|
}
|
|
}
|
|
|
|
// if (nobom && high >= len / 4)
|
|
// return 0;
|
|
|
|
if (!nobom && bad >= len / 2)
|
|
return 0;
|
|
|
|
return 1 + be;
|
|
}
|
|
|
|
cli_file_t cli_texttype(const unsigned char *buf, unsigned int len)
|
|
{
|
|
int ret;
|
|
|
|
/*
|
|
* @TODO: Add UTF8/16/32 BOM Detection to improve text type accuracy.
|
|
* Significant regression testing would be needed to ensure that re-typing
|
|
* files does not impact efficacy.
|
|
*/
|
|
if (td_isascii(buf, len)) {
|
|
cli_dbgmsg("Recognized ASCII text\n");
|
|
return CL_TYPE_TEXT_ASCII;
|
|
} else if (td_isutf8(buf, len)) {
|
|
cli_dbgmsg("Recognized UTF-8 character data\n");
|
|
return CL_TYPE_TEXT_UTF8;
|
|
} else if ((ret = td_isutf16(buf, len))) {
|
|
cli_dbgmsg("Recognized %s character data\n", (ret == 1) ? "UTF-16LE" : "UTF-16BE");
|
|
return (ret == 1) ? CL_TYPE_TEXT_UTF16LE : CL_TYPE_TEXT_UTF16BE;
|
|
} else {
|
|
cli_dbgmsg("Recognized binary data\n");
|
|
return CL_TYPE_BINARY_DATA;
|
|
}
|
|
}
|