aboutsummaryrefslogtreecommitdiffstats
path: root/openbsc/src/gsm_04_80.c
blob: 8271274f18ddc0fe7b07d50a64c28b8623fd45cb (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
/* GSM Mobile Radio Interface Layer 3 messages on the A-bis interface
 * 3GPP TS 04.08 version 7.21.0 Release 1998 / ETSI TS 100 940 V7.21.0 */

/* (C) 2008-2009 by Harald Welte <laforge@gnumonks.org>
 * (C) 2008, 2009 by Holger Hans Peter Freyther <zecke@selfish.org>
 * (C) 2009 by Mike Haben <michael.haben@btinternet.com>
 *
 * All Rights Reserved
 *
 * 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 <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>

#include <osmocore/msgb.h>
#include <osmocore/tlv.h>
#include <openbsc/debug.h>
#include <openbsc/gsm_data.h>
#include <osmocore/gsm_utils.h>
#include <openbsc/gsm_04_08.h>
#include <openbsc/gsm_04_80.h>

/* Forward declarations */
static int parse_ussd(u_int8_t *ussd, struct ussd_request *req);
static int parse_ussd_info_elements(u_int8_t *ussd_ie,
					struct ussd_request *req);
static int parse_facility_ie(u_int8_t *facility_ie, u_int8_t length,
					struct ussd_request *req);
static int parse_ss_invoke(u_int8_t *invoke_data, u_int8_t length,
					struct ussd_request *req);
static int parse_process_uss_req(u_int8_t *uss_req_data, u_int8_t length,
					struct ussd_request *req);

static inline unsigned char *msgb_wrap_with_TL(struct msgb *msgb, u_int8_t tag)
{
	msgb->data -= 2;
	msgb->data[0] = tag;
	msgb->data[1] = msgb->len;
	msgb->len += 2;
	return msgb->data;
}

static inline unsigned char *msgb_push_TLV1(struct msgb *msgb, u_int8_t tag,
					    u_int8_t value)
{
	msgb->data -= 3;
	msgb->len += 3;
	msgb->data[0] = tag;
	msgb->data[1] = 1;
	msgb->data[2] = value;
	return msgb->data;
}


/* Decode a mobile-originated USSD-request message */
int gsm0480_decode_ussd_request(const struct msgb *msg, struct ussd_request *req)
{
	int rc = 0;
	u_int8_t *parse_ptr = msgb_l3(msg);

	if ((*parse_ptr & 0x0F) == GSM48_PDISC_NC_SS) {
		req->transaction_id = *parse_ptr & 0x70;
		rc = parse_ussd(parse_ptr+1, req);
	}

	if (!rc)
		DEBUGP(DMM, "Error occurred while parsing received USSD!\n");

	return rc;
}

static int parse_ussd(u_int8_t *ussd, struct ussd_request *req)
{
	int rc = 1;
	u_int8_t msg_type = ussd[0] & 0xBF;  /* message-type - section 3.4 */

	switch (msg_type) {
	case GSM0480_MTYPE_RELEASE_COMPLETE:
		DEBUGP(DMM, "USS Release Complete\n");
		/* could also parse out the optional Cause/Facility data */
		req->text[0] = 0xFF;
		break;
	case GSM0480_MTYPE_REGISTER:
	case GSM0480_MTYPE_FACILITY:
		rc &= parse_ussd_info_elements(ussd+1, req);
		break;
	default:
		fprintf(stderr, "Unknown GSM 04.80 message-type field 0x%02x\n",
			ussd[0]);
		rc = 0;
		break;
	}

	return rc;
}

static int parse_ussd_info_elements(u_int8_t *ussd_ie, struct ussd_request *req)
{
	int rc;
	/* Information Element Identifier - table 3.2 & GSM 04.08 section 10.5 */
	u_int8_t iei = ussd_ie[0];
	u_int8_t iei_length = ussd_ie[1];

	switch (iei) {
	case GSM48_IE_CAUSE:
		break;
	case GSM0480_IE_FACILITY:
		rc = parse_facility_ie(ussd_ie+2, iei_length, req);
		break;
	case GSM0480_IE_SS_VERSION:
		break;
	default:
		fprintf(stderr, "Unhandled GSM 04.08 or 04.80 IEI 0x%02x\n",
			iei);
		rc = 0;
		break;
	}

	return rc;
}

static int parse_facility_ie(u_int8_t *facility_ie, u_int8_t length,
						struct ussd_request *req)
{
	int rc = 1;
	u_int8_t offset = 0;

	do {
		/* Component Type tag - table 3.7 */
		u_int8_t component_type = facility_ie[offset];
		u_int8_t component_length = facility_ie[offset+1];

		switch (component_type) {
		case GSM0480_CTYPE_INVOKE:
			rc &= parse_ss_invoke(facility_ie+2,
						component_length,
						req);
			break;
		case GSM0480_CTYPE_RETURN_RESULT:
			break;
		case GSM0480_CTYPE_RETURN_ERROR:
			break;
		case GSM0480_CTYPE_REJECT:
			break;
		default:
			fprintf(stderr, "Unknown GSM 04.80 Facility "
				"Component Type 0x%02x\n", component_type);
			rc = 0;
			break;
		}
		offset += (component_length+2);
	} while (offset < length);

	return rc;
}

/* Parse an Invoke component - see table 3.3 */
static int parse_ss_invoke(u_int8_t *invoke_data, u_int8_t length,
						struct ussd_request *req)
{
	int rc = 1;
	u_int8_t offset;

	/* mandatory part */
	if (invoke_data[0] != GSM0480_COMPIDTAG_INVOKE_ID) {
		fprintf(stderr, "Unexpected GSM 04.80 Component-ID tag "
			"0x%02x (expecting Invoke ID tag)\n", invoke_data[0]);
	}

	offset = invoke_data[1] + 2;
	req->invoke_id = invoke_data[2];

	/* optional part */
	if (invoke_data[offset] == GSM0480_COMPIDTAG_LINKED_ID)
		offset += invoke_data[offset+1] + 2;  /* skip over it */

	/* mandatory part */
	if (invoke_data[offset] == GSM0480_OPERATION_CODE) {
		u_int8_t operation_code = invoke_data[offset+2];
		switch (operation_code) {
		case GSM0480_OP_CODE_PROCESS_USS_REQ:
			rc = parse_process_uss_req(invoke_data + offset + 3,
						   length - offset - 3,
						   req);
			break;
		default:
			fprintf(stderr, "GSM 04.80 operation code 0x%02x "
				"is not yet handled\n", operation_code);
			rc = 0;
			break;
		}
	} else {
		fprintf(stderr, "Unexpected GSM 04.80 Component-ID tag 0x%02x "
			"(expecting Operation Code tag)\n",
			invoke_data[0]);
		rc = 0;
	}

	return rc;
}

/* Parse the parameters of a Process UnstructuredSS Request */
static int parse_process_uss_req(u_int8_t *uss_req_data, u_int8_t length,
					struct ussd_request *req)
{
	int rc = 0;
	int num_chars;
	u_int8_t dcs;

	if (uss_req_data[0] == GSM_0480_SEQUENCE_TAG) {
		if (uss_req_data[2] == ASN1_OCTET_STRING_TAG) {
			dcs = uss_req_data[4];
			if ((dcs == 0x0F) &&
			    (uss_req_data[5] == ASN1_OCTET_STRING_TAG)) {
				num_chars = (uss_req_data[6] * 8) / 7;
				/* Prevent a mobile-originated buffer-overrun! */
				if (num_chars > MAX_LEN_USSD_STRING)
					num_chars = MAX_LEN_USSD_STRING;
				gsm_7bit_decode(req->text,
						&(uss_req_data[7]), num_chars);
				/* append null-terminator */
				req->text[num_chars+1] = 0;  
				rc = 1;
			}
		}
	}
	return rc;
}

/* Send response to a mobile-originated ProcessUnstructuredSS-Request */
int gsm0480_send_ussd_response(const struct msgb *in_msg, const char *response_text,
						const struct ussd_request *req)
{
	struct msgb *msg = gsm48_msgb_alloc();
	struct gsm48_hdr *gh;
	u_int8_t *ptr8;
	int response_len;

	response_len = (strlen(response_text) * 7) / 8;
	if (((strlen(response_text) * 7) % 8) != 0)
		response_len += 1;

	msg->bts_link = in_msg->bts_link;
	msg->lchan = in_msg->lchan;

	/* First put the payload text into the message */
	ptr8 = msgb_put(msg, response_len);
	gsm_7bit_encode(ptr8, response_text);

	/* Then wrap it as an Octet String */
	msgb_wrap_with_TL(msg, ASN1_OCTET_STRING_TAG);

	/* Pre-pend the DCS octet string */
	msgb_push_TLV1(msg, ASN1_OCTET_STRING_TAG, 0x0F);

	/* Then wrap these as a Sequence */
	msgb_wrap_with_TL(msg, GSM_0480_SEQUENCE_TAG);

	/* Pre-pend the operation code */
	msgb_push_TLV1(msg, GSM0480_OPERATION_CODE,
			GSM0480_OP_CODE_PROCESS_USS_REQ);

	/* Wrap the operation code and IA5 string as a sequence */
	msgb_wrap_with_TL(msg, GSM_0480_SEQUENCE_TAG);

	/* Pre-pend the invoke ID */
	msgb_push_TLV1(msg, GSM0480_COMPIDTAG_INVOKE_ID, req->invoke_id);

	/* Wrap this up as a Return Result component */
	msgb_wrap_with_TL(msg, GSM0480_CTYPE_RETURN_RESULT);

	/* Wrap the component in a Facility message */
	msgb_wrap_with_TL(msg, GSM0480_IE_FACILITY);

	/* And finally pre-pend the L3 header */
	gh = (struct gsm48_hdr *) msgb_push(msg, sizeof(*gh));
	gh->proto_discr = GSM48_PDISC_NC_SS | req->transaction_id
					| (1<<7);  /* TI direction = 1 */
	gh->msg_type = GSM0480_MTYPE_RELEASE_COMPLETE;

	return gsm48_sendmsg(msg, NULL);
}

int gsm0480_send_ussd_reject(const struct msgb *in_msg,
				const struct ussd_request *req)
{
	struct msgb *msg = gsm48_msgb_alloc();
	struct gsm48_hdr *gh;

	msg->bts_link = in_msg->bts_link;
	msg->lchan = in_msg->lchan;

	/* First insert the problem code */
	msgb_push_TLV1(msg, GSM_0480_PROBLEM_CODE_TAG_GENERAL,
			GSM_0480_GEN_PROB_CODE_UNRECOGNISED);

	/* Before it insert the invoke ID */
	msgb_push_TLV1(msg, GSM0480_COMPIDTAG_INVOKE_ID, req->invoke_id);

	/* Wrap this up as a Reject component */
	msgb_wrap_with_TL(msg, GSM0480_CTYPE_REJECT);

	/* Wrap the component in a Facility message */
	msgb_wrap_with_TL(msg, GSM0480_IE_FACILITY);

	/* And finally pre-pend the L3 header */
	gh = (struct gsm48_hdr *) msgb_push(msg, sizeof(*gh));
	gh->proto_discr = GSM48_PDISC_NC_SS;
	gh->proto_discr |= req->transaction_id | (1<<7);  /* TI direction = 1 */
	gh->msg_type = GSM0480_MTYPE_RELEASE_COMPLETE;

	return gsm48_sendmsg(msg, NULL);
}