ndef.c revision 04949598a23f501be6eec21697465fd46a28840a 
1/*
2 * NDEF(NFC Data Exchange Format) routines for Wi-Fi Protected Setup
3 *   Reference is "NFCForum-TS-NDEF_1.0 2006-07-24".
4 * Copyright (c) 2009-2012, Masashi Honma <masashi.honma@gmail.com>
5 *
6 * This software may be distributed under the terms of the BSD license.
7 * See README for more details.
8 */
9
10#include "includes.h"
11#include "common.h"
12#include "wps/wps.h"
13#include "wps/wps_i.h"
14
15#define FLAG_MESSAGE_BEGIN (1 << 7)
16#define FLAG_MESSAGE_END (1 << 6)
17#define FLAG_CHUNK (1 << 5)
18#define FLAG_SHORT_RECORD (1 << 4)
19#define FLAG_ID_LENGTH_PRESENT (1 << 3)
20#define FLAG_TNF_RFC2046 (0x02)
21
22struct ndef_record {
23	const u8 *type;
24	const u8 *id;
25	const u8 *payload;
26	u8 type_length;
27	u8 id_length;
28	u32 payload_length;
29	u32 total_length;
30};
31
32static char wifi_handover_type[] = "application/vnd.wfa.wsc";
33
34static int ndef_parse_record(const u8 *data, u32 size,
35			     struct ndef_record *record)
36{
37	const u8 *pos = data + 1;
38
39	if (size < 2)
40		return -1;
41	record->type_length = *pos++;
42	if (data[0] & FLAG_SHORT_RECORD) {
43		if (size < 3)
44			return -1;
45		record->payload_length = *pos++;
46	} else {
47		if (size < 6)
48			return -1;
49		record->payload_length = ntohl(*(u32 *)pos);
50		pos += sizeof(u32);
51	}
52
53	if (data[0] & FLAG_ID_LENGTH_PRESENT) {
54		if ((int) size < pos - data + 1)
55			return -1;
56		record->id_length = *pos++;
57	} else
58		record->id_length = 0;
59
60	record->type = record->type_length == 0 ? NULL : pos;
61	pos += record->type_length;
62
63	record->id = record->id_length == 0 ? NULL : pos;
64	pos += record->id_length;
65
66	record->payload = record->payload_length == 0 ? NULL : pos;
67	pos += record->payload_length;
68
69	record->total_length = pos - data;
70	if (record->total_length > size)
71		return -1;
72	return 0;
73}
74
75
76static struct wpabuf * ndef_parse_records(const struct wpabuf *buf,
77					  int (*filter)(struct ndef_record *))
78{
79	struct ndef_record record;
80	int len = wpabuf_len(buf);
81	const u8 *data = wpabuf_head(buf);
82
83	while (len > 0) {
84		if (ndef_parse_record(data, len, &record) < 0) {
85			wpa_printf(MSG_ERROR, "NDEF : Failed to parse");
86			return NULL;
87		}
88		if (filter == NULL || filter(&record))
89			return wpabuf_alloc_copy(record.payload,
90						 record.payload_length);
91		data += record.total_length;
92		len -= record.total_length;
93	}
94	wpa_printf(MSG_ERROR, "NDEF : Record not found");
95	return NULL;
96}
97
98
99static struct wpabuf * ndef_build_record(u8 flags, void *type,
100					 u8 type_length, void *id,
101					 u8 id_length,
102					 const struct wpabuf *payload)
103{
104	struct wpabuf *record;
105	size_t total_len;
106	int short_record;
107	u8 local_flag;
108	size_t payload_length = wpabuf_len(payload);
109
110	short_record = payload_length < 256 ? 1 : 0;
111
112	total_len = 2; /* flag + type length */
113	/* payload length */
114	total_len += short_record ? sizeof(u8) : sizeof(u32);
115	if (id_length > 0)
116		total_len += 1;
117	total_len += type_length + id_length + payload_length;
118	record = wpabuf_alloc(total_len);
119	if (record == NULL) {
120		wpa_printf(MSG_ERROR, "NDEF : Failed to allocate "
121			   "record for build");
122		return NULL;
123	}
124
125	local_flag = flags;
126	if (id_length > 0)
127		local_flag |= FLAG_ID_LENGTH_PRESENT;
128	if (short_record)
129		local_flag |= FLAG_SHORT_RECORD;
130	wpabuf_put_u8(record, local_flag);
131
132	wpabuf_put_u8(record, type_length);
133
134	if (short_record)
135		wpabuf_put_u8(record, payload_length);
136	else
137		wpabuf_put_be32(record, payload_length);
138
139	if (id_length > 0)
140		wpabuf_put_u8(record, id_length);
141	wpabuf_put_data(record, type, type_length);
142	wpabuf_put_data(record, id, id_length);
143	wpabuf_put_buf(record, payload);
144	return record;
145}
146
147
148static int wifi_filter(struct ndef_record *record)
149{
150	if (record->type_length != os_strlen(wifi_handover_type))
151		return 0;
152	if (os_memcmp(record->type, wifi_handover_type,
153		      os_strlen(wifi_handover_type)) != 0)
154		return 0;
155	return 1;
156}
157
158
159struct wpabuf * ndef_parse_wifi(const struct wpabuf *buf)
160{
161	return ndef_parse_records(buf, wifi_filter);
162}
163
164
165struct wpabuf * ndef_build_wifi(const struct wpabuf *buf)
166{
167	return ndef_build_record(FLAG_MESSAGE_BEGIN | FLAG_MESSAGE_END |
168				 FLAG_TNF_RFC2046, wifi_handover_type,
169				 os_strlen(wifi_handover_type), NULL, 0, buf);
170}
171