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/* ber.c
*
* Basic Encoding Rules (BER) file reading
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#include "config.h"
#include <errno.h>
#include "wtap-int.h"
#include "file_wrappers.h"
#include <wsutil/buffer.h>
#include "ber.h"
#define BER_CLASS_UNI 0
#define BER_CLASS_APP 1
#define BER_CLASS_CON 2
#define BER_UNI_TAG_SEQ 16 /* SEQUENCE, SEQUENCE OF */
#define BER_UNI_TAG_SET 17 /* SET, SET OF */
static int ber_file_type_subtype = -1;
void register_ber(void);
static gboolean ber_full_file_read(wtap *wth, wtap_rec *rec, Buffer *buf,
int *err, gchar **err_info,
gint64 *data_offset)
{
if (!wtap_full_file_read(wth, rec, buf, err, err_info, data_offset))
return FALSE;
/* Pass the file name. */
rec->rec_header.packet_header.pseudo_header.ber.pathname = wth->pathname;
return TRUE;
}
static gboolean ber_full_file_seek_read(wtap *wth, gint64 seek_off,
wtap_rec *rec, Buffer *buf,
int *err, gchar **err_info)
{
if (!wtap_full_file_seek_read(wth, seek_off, rec, buf, err, err_info))
return FALSE;
/* Pass the file name. */
rec->rec_header.packet_header.pseudo_header.ber.pathname = wth->pathname;
return TRUE;
}
wtap_open_return_val ber_open(wtap *wth, int *err, gchar **err_info)
{
#define BER_BYTES_TO_CHECK 8
guint8 bytes[BER_BYTES_TO_CHECK];
guint8 ber_id;
gint8 ber_class;
gint8 ber_tag;
gboolean ber_pc;
guint8 oct, nlb = 0;
int len = 0;
gint64 file_size;
int offset = 0, i;
if (!wtap_read_bytes(wth->fh, &bytes, BER_BYTES_TO_CHECK, err, err_info)) {
if (*err != WTAP_ERR_SHORT_READ)
return WTAP_OPEN_ERROR;
return WTAP_OPEN_NOT_MINE;
}
ber_id = bytes[offset++];
ber_class = (ber_id>>6) & 0x03;
ber_pc = (ber_id>>5) & 0x01;
ber_tag = ber_id & 0x1F;
/* it must be constructed and either a SET or a SEQUENCE */
/* or a CONTEXT/APPLICATION less than 32 (arbitrary) */
if(!(ber_pc &&
(((ber_class == BER_CLASS_UNI) && ((ber_tag == BER_UNI_TAG_SET) || (ber_tag == BER_UNI_TAG_SEQ))) ||
(((ber_class == BER_CLASS_CON) || (ber_class == BER_CLASS_APP)) && (ber_tag < 32)))))
return WTAP_OPEN_NOT_MINE;
/* now check the length */
oct = bytes[offset++];
if(oct != 0x80) {
/* not indefinite length encoded */
if(!(oct & 0x80))
/* length fits into a single byte */
len = oct;
else {
nlb = oct & 0x7F; /* number of length bytes */
if((nlb > 0) && (nlb <= (BER_BYTES_TO_CHECK - 2))) {
/* not indefinite length and we have read enough bytes to compute the length */
i = nlb;
while(i--) {
oct = bytes[offset++];
len = (len<<8) + oct;
}
}
}
len += (2 + nlb); /* add back Tag and Length bytes */
file_size = wtap_file_size(wth, err);
if(len != file_size) {
return WTAP_OPEN_NOT_MINE; /* not ASN.1 */
}
} else {
/* Indefinite length encoded - assume it is BER */
}
/* seek back to the start of the file */
if (file_seek(wth->fh, 0, SEEK_SET, err) == -1)
return WTAP_OPEN_ERROR;
wth->file_type_subtype = ber_file_type_subtype;
wth->file_encap = WTAP_ENCAP_BER;
wth->snapshot_length = 0;
wth->subtype_read = ber_full_file_read;
wth->subtype_seek_read = ber_full_file_seek_read;
wth->file_tsprec = WTAP_TSPREC_SEC;
return WTAP_OPEN_MINE;
}
static const struct supported_block_type ber_blocks_supported[] = {
/*
* These are file formats that we dissect, so we provide only one
* "packet" with the file's contents, and don't support any
* options.
*/
{ WTAP_BLOCK_PACKET, ONE_BLOCK_SUPPORTED, NO_OPTIONS_SUPPORTED }
};
static const struct file_type_subtype_info ber_info = {
"ASN.1 Basic Encoding Rules", "ber", NULL, NULL,
FALSE, BLOCKS_SUPPORTED(ber_blocks_supported),
NULL, NULL, NULL
};
void register_ber(void)
{
ber_file_type_subtype = wtap_register_file_type_subtype(&ber_info);
/*
* Register name for backwards compatibility with the
* wtap_filetypes table in Lua.
*/
wtap_register_backwards_compatibility_lua_name("BER", ber_file_type_subtype);
}
/*
* Editor modelines - https://www.wireshark.org/tools/modelines.html
*
* Local Variables:
* c-basic-offset: 2
* tab-width: 8
* indent-tabs-mode: nil
* End:
*
* vi: set shiftwidth=2 tabstop=8 expandtab:
* :indentSize=2:tabSize=8:noTabs=true:
*/
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