wireshark/wiretap/mime_file.c

/* mime_file.c
 *
 * MIME file format decoder for the Wiretap library.
 *
 * This is for use with Wireshark dissectors that handle file
 * formats (e.g., because they handle a particular MIME media type).
 * It breaks the file into chunks of at most WTAP_MAX_PACKET_SIZE,
 * each of which is reported as a packet, so that files larger than
 * WTAP_MAX_PACKET_SIZE can be handled by reassembly.
 *
 * The "MIME file" dissector does the reassembly, and hands the result
 * off to heuristic dissectors to try to identify the file's contents.
 *
 * Wiretap Library
 * This program 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 to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#include "config.h"

#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

#include "wtap-int.h"
#include "file_wrappers.h"
#include "buffer.h"
#include "mime_file.h"

typedef struct {
	const guint8 *magic;
	guint magic_len;
} mime_files_t;

/*
 * Written by Marton Nemeth <nm127@freemail.hu>
 * Copyright 2009 Marton Nemeth
 * The JPEG and JFIF specification can be found at:
 *
 * http://www.jpeg.org/public/jfif.pdf
 * http://www.w3.org/Graphics/JPEG/itu-t81.pdf
 */
static const guint8 jpeg_jfif_magic[] = { 0xFF, 0xD8, /* SOF */
					  0xFF        /* start of the next marker */
					};

/* <?xml */
static const guint8 xml_magic[]    = { '<', '?', 'x', 'm', 'l' };
static const guint8 png_magic[]    = { 0x89, 'P', 'N', 'G', '\r', '\n', 0x1A, '\n' };
static const guint8 gif87a_magic[] = { 'G', 'I', 'F', '8', '7', 'a'};
static const guint8 gif89a_magic[] = { 'G', 'I', 'F', '8', '9', 'a'};
static const guint8 elf_magic[]    = { 0x7F, 'E', 'L', 'F'};

static const mime_files_t magic_files[] = {
	{ jpeg_jfif_magic, sizeof(jpeg_jfif_magic) },
	{ xml_magic, sizeof(xml_magic) },
	{ png_magic, sizeof(png_magic) },
	{ gif87a_magic, sizeof(gif87a_magic) },
	{ gif89a_magic, sizeof(gif89a_magic) },
	{ elf_magic, sizeof(elf_magic) }
};

#define	N_MAGIC_TYPES	(sizeof(magic_files) / sizeof(magic_files[0]))

/*
 * Impose a not-too-large limit on the maximum file size, to avoid eating
 * up 99% of the (address space, swap partition, disk space for swap/page
 * files); if we were to return smaller chunks and let the dissector do
 * reassembly, it would *still* have to allocate a buffer the size of
 * the file, so it's not as if we'd neve try to allocate a buffer the
 * size of the file.
 *
 * For now, go for 16MB.
 */
#define MAX_FILE_SIZE	(16*1024*1024)

static gboolean
mime_read_file(wtap *wth, FILE_T fh, struct wtap_pkthdr *phdr,
    Buffer *buf, int *err, gchar **err_info)
{
	gint64 file_size;
	int packet_size;

	if ((file_size = wtap_file_size(wth, err)) == -1)
		return FALSE;

	if (file_size > MAX_FILE_SIZE) {
		/*
		 * Don't blow up trying to allocate space for an
		 * immensely-large file.
		 */
		*err = WTAP_ERR_BAD_FILE;
		*err_info = g_strdup_printf("mime_file: File has %" G_GINT64_MODIFIER "d-byte packet, bigger than maximum of %u",
				file_size, MAX_FILE_SIZE);
		return FALSE;
	}
	packet_size = (int)file_size;

	phdr->rec_type = REC_TYPE_PACKET;
	phdr->presence_flags = 0; /* yes, we have no bananas^Wtime stamp */

	phdr->caplen = packet_size;
	phdr->len = packet_size;

	phdr->ts.secs = 0;
	phdr->ts.nsecs = 0;

	return wtap_read_packet_bytes(fh, buf, packet_size, err, err_info);
}

static gboolean
mime_read(wtap *wth, int *err, gchar **err_info, gint64 *data_offset)
{
	gint64 offset;

	*err = 0;

	offset = file_tell(wth->fh);

	/* there is only ever one packet */
	if (offset != 0)
		return FALSE;

	*data_offset = offset;

	return mime_read_file(wth, wth->fh, &wth->phdr, wth->frame_buffer, err, err_info);
}

static gboolean
mime_seek_read(wtap *wth, gint64 seek_off, struct wtap_pkthdr *phdr, Buffer *buf, int *err, gchar **err_info)
{
	/* there is only one packet */
	if (seek_off > 0) {
		*err = 0;
		return FALSE;
	}

	if (file_seek(wth->random_fh, seek_off, SEEK_SET, err) == -1)
		return FALSE;

	return mime_read_file(wth, wth->random_fh, phdr, buf, err, err_info);
}

int
mime_file_open(wtap *wth, int *err, gchar **err_info)
{
	char magic_buf[128]; /* increase buffer size when needed */
	int bytes_read;
	gboolean found_file;
	/* guint file_ok; */
	guint i;

	guint read_bytes = 0;

	for (i = 0; i < N_MAGIC_TYPES; i++)
		read_bytes = MAX(read_bytes, magic_files[i].magic_len);

	read_bytes = (guint)MIN(read_bytes, sizeof(magic_buf));
	bytes_read = file_read(magic_buf, read_bytes, wth->fh);

	if (bytes_read < 0) {
		*err = file_error(wth->fh, err_info);
		return -1;
	}
	if (bytes_read == 0)
		return 0;

	found_file = FALSE;
	for (i = 0; i < N_MAGIC_TYPES; i++) {
		if ((guint) bytes_read >= magic_files[i].magic_len && !memcmp(magic_buf, magic_files[i].magic, MIN(magic_files[i].magic_len, (guint) bytes_read))) {
			if (!found_file) {
				found_file = TRUE;
				/* file_ok = i; */
			} else
				return 0;	/* many files matched, bad file */
		}
	}

	if (!found_file)
		return 0;

	if (file_seek(wth->fh, 0, SEEK_SET, err) == -1)
		return -1;

	wth->file_type_subtype = WTAP_FILE_TYPE_SUBTYPE_MIME;
	wth->file_encap = WTAP_ENCAP_MIME;
	wth->tsprecision = WTAP_FILE_TSPREC_SEC;
	wth->subtype_read = mime_read;
	wth->subtype_seek_read = mime_seek_read;
	wth->snapshot_length = 0;

	return 1;
}