path: root/wiretap/dct3trace.c

/* dct3trace.c
 * Routines for reading signalling traces generated by Gammu (www.gammu.org)
 * from Nokia DCT3 phones in Netmonitor mode.
 *
 * gammu --nokiadebug nhm5_587.txt v18-19
 *
 * Duncan Salerno <duncan.salerno@googlemail.com>
 *
 * Wiretap Library
 * Copyright (c) 1998 by Gilbert Ramirez <gram@alumni.rice.edu>
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 */

#include "config.h"
#include "dct3trace.h"
#include "wtap-int.h"
#include "file_wrappers.h"

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

#include <wsutil/strtoi.h>

/*
   Example downlink data:

<?xml version="1.0"?>
<dump>
<l1 direction="down" logicalchannel="96" physicalchannel="19" sequence="268116" error="0" timeshift="2992" bsic="22" data="31063F100DD0297A53E1020103C802398E0B2B2B2B2B2B" >
<l2 data="063F100DD0297A53E1020103" rest="C802398E0B2B2B2B2B2B" >
</l2>
</l1>
</dump>

   Example uplink data (no raw L1):

<?xml version="1.0"?>
<dump>
<l1 direction="up" logicalchannel="112" >
<l2 type="U" subtype="Unknown" p="0" data="061500400000000000000000000000000000" >
</l2>
</l1>
</dump>

 */


/* Magic text to check */
static const char dct3trace_magic_line1[] = "<?xml version=\"1.0\"?>";
static const char dct3trace_magic_line2[] = "<dump>";
static const char dct3trace_magic_record_start[]  = "<l1 ";
static const char dct3trace_magic_record_end[]  = "</l1>";
static const char dct3trace_magic_l2_start[]  = "<l2 ";
#if 0 /* Not used ?? */
static const char dct3trace_magic_l2_end[]  = "</l2>";
#endif
static const char dct3trace_magic_end[]  = "</dump>";

#define MAX_PACKET_LEN 23

static bool dct3trace_read(wtap *wth, wtap_rec *rec,
	Buffer *buf, int *err, char **err_info, int64_t *data_offset);
static bool dct3trace_seek_read(wtap *wth, int64_t seek_off,
	wtap_rec *rec, Buffer *buf, int *err, char **err_info);

static int dct3trace_file_type_subtype = -1;

void register_dct3trace(void);

/*
 * Following 3 functions taken from gsmdecode-0.7bis, with permission:
 *
 *   https://web.archive.org/web/20091218112927/http://wiki.thc.org/gsm
 */

static int
hc2b(unsigned char hex)
{
	hex = g_ascii_tolower(hex);
	if ((hex >= '0') && (hex <= '9'))
		return hex - '0';
	if ((hex >= 'a') && (hex <= 'f'))
		return hex - 'a' + 10;
	return -1;
}

static int
hex2bin(uint8_t *out, uint8_t *out_end, char *in)
{
	uint8_t *out_start = out;
	int is_low = 0;
	int c;

	while (*in != '\0')
	{
		c = hc2b(*(unsigned char *)in);
		if (c < 0)
		{
			in++;
			continue;
		}
		if (out == out_end)
		{
			/* Too much data */
			return -1;
		}
		if (is_low == 0)
		{
			*out = c << 4;
			is_low = 1;
		} else {
			*out |= (c & 0x0f);
			is_low = 0;
			out++;
		}
		in++;
	}

	return (int)(out - out_start);
}

static bool
xml_get_int(int *val, const char *str, const char *pattern, int *err, char **err_info)
{
	const char *ptr, *endptr;
	char *start, *end;
	char buf[32];

	ptr = strstr(str, pattern);
	if (ptr == NULL) {
		*err = WTAP_ERR_BAD_FILE;
		*err_info = ws_strdup_printf("dct3trace: %s not found", pattern);
		return false;
	}
	/*
	 * XXX - should we just skip past the pattern and check for ="?
	 */
	start = strchr(ptr, '"');
	if (start == NULL) {
		*err = WTAP_ERR_BAD_FILE;
		*err_info = ws_strdup_printf("dct3trace: opening quote for %s not found", pattern);
		return false;
	}
	start++;
	/*
	 * XXX - should we just use ws_strtoi32() and check whether
	 * the character following the number is a "?
	 */
	end = strchr(start, '"');
	if (end == NULL) {
		*err = WTAP_ERR_BAD_FILE;
		*err_info = ws_strdup_printf("dct3trace: closing quote for %s not found", pattern);
		return false;
	}
	if (end - start > 31) {
		*err = WTAP_ERR_BAD_FILE;
		*err_info = ws_strdup_printf("dct3trace: %s value is too long", pattern);
		return false;
	}

	memcpy(buf, start, end - start);
	buf[end - start] = '\0';
	/*
	 * XXX - should we allow negative numbers in all cases?  Or are
	 * there cases where the number is unsigned?
	 */
	if (!ws_strtoi32(buf, &endptr, val)) {
		*err = WTAP_ERR_BAD_FILE;
		if (errno == ERANGE) {
			if (*val < 0)
				*err_info = ws_strdup_printf("dct3trace: %s value is too small, minimum is %d", pattern, *val);
			else
				*err_info = ws_strdup_printf("dct3trace: %s value is too large, maximum is %d", pattern, *val);
		} else
			*err_info = ws_strdup_printf("dct3trace: %s value \"%s\" not a number", pattern, buf);
		return false;
	}
	if (*endptr != '\0') {
		*err = WTAP_ERR_BAD_FILE;
		*err_info = ws_strdup_printf("dct3trace: %s value \"%s\" not a number", pattern, buf);
		return false;
	}
	return true;
}


wtap_open_return_val dct3trace_open(wtap *wth, int *err, char **err_info)
{
	char line1[64], line2[64];

	/* Look for Gammu DCT3 trace header */
	if (file_gets(line1, sizeof(line1), wth->fh) == NULL ||
		file_gets(line2, sizeof(line2), wth->fh) == NULL)
	{
		*err = file_error(wth->fh, err_info);
		if (*err != 0 && *err != WTAP_ERR_SHORT_READ)
			return WTAP_OPEN_ERROR;
		return WTAP_OPEN_NOT_MINE;
	}

	/* Don't compare line endings */
	if( strncmp(dct3trace_magic_line1, line1, strlen(dct3trace_magic_line1)) != 0 ||
		strncmp(dct3trace_magic_line2, line2, strlen(dct3trace_magic_line2)) != 0)
	{
		return WTAP_OPEN_NOT_MINE;
	}

	wth->file_encap = WTAP_ENCAP_GSM_UM;
	wth->file_type_subtype = dct3trace_file_type_subtype;
	wth->snapshot_length = 0; /* not known */
	wth->subtype_read = dct3trace_read;
	wth->subtype_seek_read = dct3trace_seek_read;
	wth->file_tsprec = WTAP_TSPREC_SEC;

	/*
	 * Add an IDB; we don't know how many interfaces were
	 * involved, so we just say one interface, about which
	 * we only know the link-layer type, snapshot length,
	 * and time stamp resolution.
	 */
	wtap_add_generated_idb(wth);

	return WTAP_OPEN_MINE;
}


static bool dct3trace_get_packet(FILE_T fh, wtap_rec *rec,
	Buffer *buf, int *err, char **err_info)
{
	char line[1024];
	uint8_t databuf[MAX_PACKET_LEN], *bufp;
	bool have_data = false;
	int len = 0;

	bufp = &databuf[0];
	while (file_gets(line, sizeof(line), fh) != NULL)
	{
		if( memcmp(dct3trace_magic_end, line, strlen(dct3trace_magic_end)) == 0 )
		{
			/* Return on end of file </dump> */
			*err = 0;
			return false;
		}
		else if( memcmp(dct3trace_magic_record_end, line, strlen(dct3trace_magic_record_end)) == 0 )
		{
			/* Return on end of record </l1> */
			if( have_data )
			{
				/* We've got a full packet! */
				rec->rec_type = REC_TYPE_PACKET;
				rec->block = wtap_block_create(WTAP_BLOCK_PACKET);
				rec->presence_flags = 0; /* no time stamp, no separate "on the wire" length */
				rec->ts.secs = 0;
				rec->ts.nsecs = 0;
				rec->rec_header.packet_header.caplen = len;
				rec->rec_header.packet_header.len = len;

				*err = 0;

				/* Make sure we have enough room for the packet */
				ws_buffer_assure_space(buf, rec->rec_header.packet_header.caplen);
				memcpy( ws_buffer_start_ptr(buf), databuf, rec->rec_header.packet_header.caplen );

				return true;
			}
			else
			{
				/* If not got any data return error */
				*err = WTAP_ERR_BAD_FILE;
				*err_info = g_strdup("dct3trace: record without data");
				return false;
			}
		}
		else if( memcmp(dct3trace_magic_record_start, line, strlen(dct3trace_magic_record_start)) == 0 )
		{
			/* Parse L1 header <l1 ...>*/
			int channel, tmp;
			char *ptr;

			rec->rec_header.packet_header.pseudo_header.gsm_um.uplink = !strstr(line, "direction=\"down\"");
			if (!xml_get_int(&channel, line, "logicalchannel", err, err_info))
				return false;

			/* Parse downlink only fields */
			if( !rec->rec_header.packet_header.pseudo_header.gsm_um.uplink )
			{
				if (!xml_get_int(&tmp, line, "physicalchannel", err, err_info))
					return false;
				rec->rec_header.packet_header.pseudo_header.gsm_um.arfcn = tmp;
				if (!xml_get_int(&tmp, line, "sequence", err, err_info))
					return false;
				rec->rec_header.packet_header.pseudo_header.gsm_um.tdma_frame = tmp;
				if (!xml_get_int(&tmp, line, "bsic", err, err_info))
					return false;
				rec->rec_header.packet_header.pseudo_header.gsm_um.bsic = tmp;
				if (!xml_get_int(&tmp, line, "error", err, err_info))
					return false;
				rec->rec_header.packet_header.pseudo_header.gsm_um.error = tmp;
				if (!xml_get_int(&tmp, line, "timeshift", err, err_info))
					return false;
				rec->rec_header.packet_header.pseudo_header.gsm_um.timeshift = tmp;
			}

			switch( channel )
			{
				case 128: rec->rec_header.packet_header.pseudo_header.gsm_um.channel = GSM_UM_CHANNEL_SDCCH; break;
				case 112: rec->rec_header.packet_header.pseudo_header.gsm_um.channel = GSM_UM_CHANNEL_SACCH; break;
				case 176: rec->rec_header.packet_header.pseudo_header.gsm_um.channel = GSM_UM_CHANNEL_FACCH; break;
				case 96: rec->rec_header.packet_header.pseudo_header.gsm_um.channel = GSM_UM_CHANNEL_CCCH; break;
				case 80: rec->rec_header.packet_header.pseudo_header.gsm_um.channel = GSM_UM_CHANNEL_BCCH; break;
				default: rec->rec_header.packet_header.pseudo_header.gsm_um.channel = GSM_UM_CHANNEL_UNKNOWN; break;
			}

			/* Read data (if have it) into databuf */
			ptr = strstr(line, "data=\"");
			if( ptr )
			{
				have_data = true; /* If has data... */
				len = hex2bin(bufp, &databuf[MAX_PACKET_LEN], ptr+6);
				if (len == -1)
				{
					*err = WTAP_ERR_BAD_FILE;
					*err_info = ws_strdup_printf("dct3trace: record length %d too long", rec->rec_header.packet_header.caplen);
					return false;
				}
			}
		}
		else if( !have_data && memcmp(dct3trace_magic_l2_start, line, strlen(dct3trace_magic_l2_start)) == 0 )
		{
			/* For uplink packets we might not get the raw L1, so have to recreate it from the L2 */
			/* Parse L2 header if didn't get data from L1 <l2 ...> */
			int data_len;
			char *ptr = strstr(line, "data=\"");

			if( !ptr )
			{
				continue;
			}

			have_data = true;

			/*
			 * We know we have no data already, so we know
			 * we have enough room for the header.
			 */
			if( rec->rec_header.packet_header.pseudo_header.gsm_um.channel == GSM_UM_CHANNEL_SACCH || rec->rec_header.packet_header.pseudo_header.gsm_um.channel == GSM_UM_CHANNEL_FACCH || rec->rec_header.packet_header.pseudo_header.gsm_um.channel == GSM_UM_CHANNEL_SDCCH )
			{
				/* Add LAPDm B header */
				memset(bufp, 0x1, 2);
				len = 3;
			}
			else
			{
				/* Add LAPDm Bbis header */
				len = 1;
			}
			bufp += len;

			data_len = hex2bin(bufp, &databuf[MAX_PACKET_LEN], ptr+6);
			if (data_len == -1)
			{
				*err = WTAP_ERR_BAD_FILE;
				*err_info = ws_strdup_printf("dct3trace: record length %d too long", rec->rec_header.packet_header.caplen);
				return false;
			}
			len += data_len;

			/* Add LAPDm length byte */
			*(bufp - 1) = data_len << 2 | 0x1;
		}
	}

	*err = file_error(fh, err_info);
	if (*err == 0)
	{
		*err = WTAP_ERR_SHORT_READ;
	}
	return false;
}


/* Find the next packet and parse it; called from wtap_read(). */
static bool dct3trace_read(wtap *wth, wtap_rec *rec, Buffer *buf,
    int *err, char **err_info, int64_t *data_offset)
{
	*data_offset = file_tell(wth->fh);

	return dct3trace_get_packet(wth->fh, rec, buf, err, err_info);
}


/* Used to read packets in random-access fashion */
static bool dct3trace_seek_read(wtap *wth, int64_t seek_off,
	wtap_rec *rec, Buffer *buf, int *err, char **err_info)
{
	if (file_seek(wth->random_fh, seek_off, SEEK_SET, err) == -1)
	{
		return false;
	}

	return dct3trace_get_packet(wth->random_fh, rec, buf, err, err_info);
}

static const struct supported_block_type dct3trace_blocks_supported[] = {
	/*
	 * We support packet blocks, with no comments or other options.
	 */
	{ WTAP_BLOCK_PACKET, MULTIPLE_BLOCKS_SUPPORTED, NO_OPTIONS_SUPPORTED }
};

static const struct file_type_subtype_info dct3trace_info = {
	"Gammu DCT3 trace", "dct3trace", "xml", NULL,
	false, BLOCKS_SUPPORTED(dct3trace_blocks_supported),
	NULL, NULL, NULL
};

void register_dct3trace(void)
{
	dct3trace_file_type_subtype = wtap_register_file_type_subtype(&dct3trace_info);

	/*
	 * Register name for backwards compatibility with the
	 * wtap_filetypes table in Lua.
	 */
	wtap_register_backwards_compatibility_lua_name("DCT3TRACE",
	    dct3trace_file_type_subtype);
}

/*
 * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
 *
 * Local variables:
 * c-basic-offset: 8
 * tab-width: 8
 * indent-tabs-mode: t
 * End:
 *
 * vi: set shiftwidth=8 tabstop=8 noexpandtab:
 * :indentSize=8:tabSize=8:noTabs=false:
 */