/* 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_module.h"
#include "file_wrappers.h"

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

#include <wsutil/strtoi.h>
#include <libxml/tree.h>
#include <libxml/parser.h>
#include <libxml/xpath.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>

 */

typedef struct dct3trace_file_info {
	GByteArray* buffer;		// holds current chunk of file
	int64_t start_offset;		// where in the file the start of the buffer points
} dct3trace_file_info_t;

/* We expect to find all the info we need to tell if this file is ours
 * within this many bytes. Must include the beginTime attribute.
 */
#define MAGIC_BUF_SIZE 512

 /* String constants sought in the XML data.
  * Written as strings instead of lists of chars for readability.
  * Use the CLEN() macro to get the length of the constant without counting
  * the null byte at the end.
  */
#define CLEN(x) (sizeof(x)-1)

/* Magic text to check */
static const unsigned char c_xml_magic[] = "<?xml";
static const char dct3trace_magic_line2[] = "<dump>";
static const char dct3trace_magic_record_start[]  = "<l1 ";
static const char dct3trace_magic_record_end[]  = "</l1>";

#define RINGBUFFER_START_SIZE INT_MAX
#define RINGBUFFER_CHUNK_SIZE 1024

#define MAX_PACKET_LEN 23

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(const char* name, xmlChar* str, int* val, int* err, char** err_info)
{
	if (str != NULL) {
		if (!ws_strtoi32((const char*)str, NULL, 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", name, *val);
				else
					*err_info = ws_strdup_printf("dct3trace: %s value is too large, maximum is %d", name, *val);
			}
			else
				*err_info = ws_strdup_printf("dct3trace: %s value \"%s\" not a number", name, str);
			return false;
		}
	}

	return true;
}

static bool
dct3trace_get_packet(wtap* wth, wtap_rec* rec, const char* text, size_t len, int* err, char** err_info)
{
	xmlDocPtr           doc;
	xmlNodePtr root_element;
	bool status = true;
	uint8_t databuf[MAX_PACKET_LEN], * bufp;
	int local_len = 0;
	bool have_data = false;

	doc = xmlParseMemory(text, (int)len);
	if (doc == NULL) {
		return false;
	}

	root_element = xmlDocGetRootElement(doc);
	if (root_element == NULL) {
		ws_debug("empty xml doc");
		status = false;
		goto end;
	}

	//Sanity check
	if (xmlStrcmp(root_element->name, (const xmlChar*)"l1") != 0) {
		*err = WTAP_ERR_BAD_FILE;
		*err_info = ws_strdup("dct3trace: Did not start with \"<l1\"");
		status = false;
		goto end;
	}

	/* Walk the attributes of the l1 tag */
	bufp = &databuf[0];
	for (xmlAttrPtr attr = root_element->properties; attr; attr = attr->next) {
		int channel = 0, tmp = 0;
		if (xmlStrcmp(attr->name, (const xmlChar*)"direction") == 0) {
			xmlChar* str = xmlNodeListGetString(root_element->doc, attr->children, 1);
			if (str != NULL) {
				rec->rec_header.packet_header.pseudo_header.gsm_um.uplink = !strstr((const char*)str, "down");
				xmlFree(str);
			}
		}
		else if (xmlStrcmp(attr->name, (const xmlChar*)"logicalchannel") == 0) {
			xmlChar* str = xmlNodeListGetString(root_element->doc, attr->children, 1);
			status = xml_get_int("logicalchannel", str, &channel, err, err_info);
			xmlFree(str);
			if (!status)
				goto end;

			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;
			}
		}
		else if (xmlStrcmp(attr->name, (const xmlChar*)"data") == 0) {
			have_data = true; /* Found data */
			xmlChar* str = xmlNodeListGetString(root_element->doc, attr->children, 1);
			local_len = hex2bin(bufp, &databuf[MAX_PACKET_LEN], (char*)str);
			xmlFree(str);
			if (local_len == -1)
			{
				*err = WTAP_ERR_BAD_FILE;
				*err_info = ws_strdup_printf("dct3trace: record length %d too long", rec->rec_header.packet_header.caplen);
				status = false;
				goto end;
			}

		}
		else if (!rec->rec_header.packet_header.pseudo_header.gsm_um.uplink) {
			/* Parse downlink only fields */

			if (xmlStrcmp(attr->name, (const xmlChar*)"physicalchannel") == 0) {
				xmlChar* str = xmlNodeListGetString(root_element->doc, attr->children, 1);
				status = xml_get_int("physicalchannel", str, &tmp, err, err_info);
				xmlFree(str);
				if (!status)
					goto end;

				rec->rec_header.packet_header.pseudo_header.gsm_um.arfcn = tmp;
			}
			else if (xmlStrcmp(attr->name, (const xmlChar*)"sequence") == 0) {
				xmlChar* str = xmlNodeListGetString(root_element->doc, attr->children, 1);
				status = xml_get_int("sequence", str, &tmp, err, err_info);
				xmlFree(str);
				if (!status)
					goto end;

				rec->rec_header.packet_header.pseudo_header.gsm_um.tdma_frame = tmp;
			}
			else if (xmlStrcmp(attr->name, (const xmlChar*)"bsic") == 0) {
				xmlChar* str = xmlNodeListGetString(root_element->doc, attr->children, 1);
				status = xml_get_int("bsic", str, &tmp, err, err_info);
				xmlFree(str);
				if (!status)
					goto end;

				rec->rec_header.packet_header.pseudo_header.gsm_um.bsic = tmp;
			}
			else if (xmlStrcmp(attr->name, (const xmlChar*)"error") == 0) {
				xmlChar* str = xmlNodeListGetString(root_element->doc, attr->children, 1);
				status = xml_get_int("error", str, &tmp, err, err_info);
				xmlFree(str);
				if (!status)
					goto end;

				rec->rec_header.packet_header.pseudo_header.gsm_um.error = tmp;
			}
			else if (xmlStrcmp(attr->name, (const xmlChar*)"timeshift") == 0) {
				xmlChar* str = xmlNodeListGetString(root_element->doc, attr->children, 1);
				status = xml_get_int("timeshift", str, &tmp, err, err_info);
				xmlFree(str);
				if (!status)
					goto end;

				rec->rec_header.packet_header.pseudo_header.gsm_um.timeshift = tmp;
			}
		}
	}

	if (!have_data)
	{
		for (xmlNodePtr cur = root_element->children; cur != NULL; cur = cur->next) {
			/* Get data from l2 tag */
			if ((cur->type == XML_ELEMENT_NODE) && (xmlStrcmp(cur->name, (const xmlChar*)"l2") == 0)) {
				for (xmlAttrPtr attr = cur->properties; attr; attr = attr->next) {

					/* 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 ...> */
					if (xmlStrcmp(attr->name, (const xmlChar*)"data") == 0) {
						int data_len;

						have_data = true; /* Found data */

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

						xmlChar* str = xmlNodeListGetString(cur->doc, attr->children, 1);
						data_len = hex2bin(bufp, &databuf[MAX_PACKET_LEN], (char*)str);
						xmlFree(str);
						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);
							status = false;
							goto end;
						}
						local_len += data_len;

						/* Add LAPDm length byte */
						*(bufp - 1) = data_len << 2 | 0x1;
					}
				}
				/* There should be only a single "l2" child element
				 * within a "l1" element, so break. (This keeps us
				 * from writing to bufp a seconds time.) */
				break;
			}
		}
	}

	if (have_data) {
		/* We've got a full packet! */
		wtap_setup_packet_rec(rec, wth->file_encap);
		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 = local_len;
		rec->rec_header.packet_header.len = local_len;

		/* Append data to the packet buffer */
		ws_buffer_append(&rec->data, databuf, rec->rec_header.packet_header.caplen);
	}
	else {
		/* If not got any data return error */
		*err = WTAP_ERR_BAD_FILE;
		*err_info = g_strdup("dct3trace: record without data");
		status = false;
	}

end:
	xmlFreeDoc(doc);
	return status;
}

/* Read from fh and store into buffer, until buffer contains needle.
 * Returns location of needle once found, or NULL if it's never found
 * (due to either EOF or read error).
 */
static uint8_t*
read_until(GByteArray* buffer, const unsigned char* needle, FILE_T fh, int* err, char** err_info)
{
	uint8_t read_buffer[RINGBUFFER_CHUNK_SIZE];
	uint8_t* found_it;
	int bytes_read = 0;

	while (NULL == (found_it = (uint8_t*)g_strstr_len((const char*)buffer->data, buffer->len, (const char*)needle))) {
		bytes_read = file_read(read_buffer, RINGBUFFER_CHUNK_SIZE, fh);
		if (bytes_read < 0) {
			*err = file_error(fh, err_info);
			break;
		}
		if (bytes_read == 0) {
			break;
		}
		g_byte_array_append(buffer, read_buffer, bytes_read);
	}
	return found_it;
}

/* Find the next packet and parse it; called from wtap_read(). */
static bool dct3trace_read(wtap *wth, wtap_rec *rec,
    int *err, char **err_info, int64_t *data_offset)
{
	dct3trace_file_info_t* file_info = (dct3trace_file_info_t*)wth->priv;
	uint8_t* buf_start;
	uint8_t* msg_start, * msg_end;
	unsigned msg_offset = 0;
	size_t msg_len = 0;
	bool status = false;

	/* Make sure we have a start and end of message in our buffer -- end first */
	msg_end = read_until(file_info->buffer, (const uint8_t*)dct3trace_magic_record_end, wth->fh, err, err_info);
	if (msg_end == NULL) {
		goto end;
	}

	buf_start = file_info->buffer->data;
	/* Now search backwards for the message start
	 * (doing it this way should skip over any empty "<msg ... />" tags we have)
	 */
	msg_start = (uint8_t*)g_strrstr_len((const char*)buf_start, (unsigned)(msg_end - buf_start), dct3trace_magic_record_start);
	if (msg_start == NULL || msg_start > msg_end) {
		*err_info = ws_strdup_printf("dct3trace: Found \"%s\" without matching \"%s\"", dct3trace_magic_record_end, dct3trace_magic_record_start);
		*err = WTAP_ERR_BAD_FILE;
		goto end;
	}

	/* We know we have a message, what's its offset from the buffer start? */
	msg_offset = (unsigned)(msg_start - buf_start);
	msg_end += CLEN(dct3trace_magic_record_end);
	msg_len = (unsigned)(msg_end - msg_start);

	/* Tell Wireshark to put us at the start of the "<msg" for seek_read later */
	*data_offset = file_info->start_offset + msg_offset;

	/* pass all of <l1....</l1> to dct3trace_get_packet() */
	status = dct3trace_get_packet(wth, rec, (const char*)msg_start, msg_len, err, err_info);

	/* Finally, shift our buffer to the end of this message to get ready for the next one.
	 * Re-use msg_len to get the length of the data we're done with.
	 */
	msg_len = msg_end - file_info->buffer->data;
	while (G_UNLIKELY(msg_len > UINT_MAX)) {
		g_byte_array_remove_range(file_info->buffer, 0, UINT_MAX);
		msg_len -= UINT_MAX;
	}
	g_byte_array_remove_range(file_info->buffer, 0, (unsigned)msg_len);
	file_info->start_offset += msg_len;

end:
	if (status == false) {
		/* There's no more to read. Empty out the buffer */
		g_byte_array_set_size(file_info->buffer, 0);
	}

	return status;
}


/* Used to read packets in random-access fashion */
static bool dct3trace_seek_read(wtap *wth, int64_t seek_off,
	wtap_rec *rec, int *err, char **err_info)
{
	dct3trace_file_info_t* file_info = (dct3trace_file_info_t*)wth->priv;
	bool status = false;
	uint8_t* msg_end;
	unsigned msg_len = 0;

	/* We stored the offset of the "<msg" for this packet */
	if (file_seek(wth->random_fh, seek_off, SEEK_SET, err) == -1)
		return false;

	msg_end = read_until(file_info->buffer, (const uint8_t*)dct3trace_magic_record_end, wth->random_fh, err, err_info);
	if (msg_end == NULL) {
		return false;
	}
	msg_end += CLEN(dct3trace_magic_record_end);
	msg_len = (unsigned)(msg_end - file_info->buffer->data);

	status = dct3trace_get_packet(wth, rec, (const char*)file_info->buffer->data, msg_len, err, err_info);
	g_byte_array_set_size(file_info->buffer, 0);
	return status;
}

/* Clean up any memory we allocated for dealing with this file.
 * Set as the subtype_close function in the file_open function below.
 * (wiretap frees wth->priv itself)
 */
static void
dct3trace_close(wtap* wth)
{
	dct3trace_file_info_t* file_info = (dct3trace_file_info_t*)wth->priv;

	if (file_info != NULL && file_info->buffer != NULL) {
		g_byte_array_free(file_info->buffer, true);
		file_info->buffer = NULL;
	}
}

wtap_open_return_val dct3trace_open(wtap* wth, int* err, char** err_info)
{
	char magic_buf[MAGIC_BUF_SIZE + 1];
	int bytes_read;
	const char* curr_pos;
	dct3trace_file_info_t* file_info;
	int64_t start_offset;

	start_offset = file_tell(wth->fh); // Most likely 0 but doesn't hurt to check
	bytes_read = file_read(magic_buf, MAGIC_BUF_SIZE, wth->fh);

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

	if (memcmp(magic_buf, c_xml_magic, CLEN(c_xml_magic)) != 0) {
		return WTAP_OPEN_NOT_MINE;
	}

	curr_pos = g_strstr_len(magic_buf, bytes_read, dct3trace_magic_line2);
	if (!curr_pos) {
		return WTAP_OPEN_NOT_MINE;
	}
	curr_pos += CLEN(dct3trace_magic_line2);

	/* Ok it's our file. From here we'll need to free memory */
	file_info = g_new0(dct3trace_file_info_t, 1);
	file_info->start_offset = start_offset + (curr_pos - magic_buf);
	file_info->buffer = g_byte_array_sized_new(RINGBUFFER_START_SIZE);
	g_byte_array_append(file_info->buffer, (const uint8_t*)curr_pos, (unsigned)(bytes_read - (curr_pos - magic_buf)));

	wth->file_type_subtype = dct3trace_file_type_subtype;
	wth->file_encap = WTAP_ENCAP_GSM_UM;
	wth->file_tsprec = WTAP_TSPREC_SEC;
	wth->subtype_read = dct3trace_read;
	wth->subtype_seek_read = dct3trace_seek_read;
	wth->subtype_close = dct3trace_close;
	wth->snapshot_length = 0;/* not known */
	wth->priv = (void*)file_info;

	/*
	 * 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 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:
 */
