ndef.c revision 7d5c8f257a74ac0d12828962a492e8b84ef83923 
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
14#define FLAG_MESSAGE_BEGIN (1 << 7)
15#define FLAG_MESSAGE_END (1 << 6)
16#define FLAG_CHUNK (1 << 5)
17#define FLAG_SHORT_RECORD (1 << 4)
18#define FLAG_ID_LENGTH_PRESENT (1 << 3)
19#define FLAG_TNF_NFC_FORUM (0x01)
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";
33static char p2p_handover_type[] = "application/vnd.wfa.p2p";
34
35static int ndef_parse_record(const u8 *data, u32 size,
36			     struct ndef_record *record)
37{
38	const u8 *pos = data + 1;
39
40	if (size < 2)
41		return -1;
42	record->type_length = *pos++;
43	if (data[0] & FLAG_SHORT_RECORD) {
44		if (size < 3)
45			return -1;
46		record->payload_length = *pos++;
47	} else {
48		if (size < 6)
49			return -1;
50		record->payload_length = ntohl(*(u32 *)pos);
51		pos += sizeof(u32);
52	}
53
54	if (data[0] & FLAG_ID_LENGTH_PRESENT) {
55		if ((int) size < pos - data + 1)
56			return -1;
57		record->id_length = *pos++;
58	} else
59		record->id_length = 0;
60
61	record->type = record->type_length == 0 ? NULL : pos;
62	pos += record->type_length;
63
64	record->id = record->id_length == 0 ? NULL : pos;
65	pos += record->id_length;
66
67	record->payload = record->payload_length == 0 ? NULL : pos;
68	pos += record->payload_length;
69
70	record->total_length = pos - data;
71	if (record->total_length > size)
72		return -1;
73	return 0;
74}
75
76
77static struct wpabuf * ndef_parse_records(const struct wpabuf *buf,
78					  int (*filter)(struct ndef_record *))
79{
80	struct ndef_record record;
81	int len = wpabuf_len(buf);
82	const u8 *data = wpabuf_head(buf);
83
84	while (len > 0) {
85		if (ndef_parse_record(data, len, &record) < 0) {
86			wpa_printf(MSG_ERROR, "NDEF : Failed to parse");
87			return NULL;
88		}
89		if (filter == NULL || filter(&record))
90			return wpabuf_alloc_copy(record.payload,
91						 record.payload_length);
92		data += record.total_length;
93		len -= record.total_length;
94	}
95	wpa_printf(MSG_ERROR, "NDEF : Record not found");
96	return NULL;
97}
98
99
100static struct wpabuf * ndef_build_record(u8 flags, void *type,
101					 u8 type_length, void *id,
102					 u8 id_length,
103					 const struct wpabuf *payload)
104{
105	struct wpabuf *record;
106	size_t total_len;
107	int short_record;
108	u8 local_flag;
109	size_t payload_length = wpabuf_len(payload);
110
111	short_record = payload_length < 256 ? 1 : 0;
112
113	total_len = 2; /* flag + type length */
114	/* payload length */
115	total_len += short_record ? sizeof(u8) : sizeof(u32);
116	if (id_length > 0)
117		total_len += 1;
118	total_len += type_length + id_length + payload_length;
119	record = wpabuf_alloc(total_len);
120	if (record == NULL) {
121		wpa_printf(MSG_ERROR, "NDEF : Failed to allocate "
122			   "record for build");
123		return NULL;
124	}
125
126	local_flag = flags;
127	if (id_length > 0)
128		local_flag |= FLAG_ID_LENGTH_PRESENT;
129	if (short_record)
130		local_flag |= FLAG_SHORT_RECORD;
131	wpabuf_put_u8(record, local_flag);
132
133	wpabuf_put_u8(record, type_length);
134
135	if (short_record)
136		wpabuf_put_u8(record, payload_length);
137	else
138		wpabuf_put_be32(record, payload_length);
139
140	if (id_length > 0)
141		wpabuf_put_u8(record, id_length);
142	wpabuf_put_data(record, type, type_length);
143	wpabuf_put_data(record, id, id_length);
144	wpabuf_put_buf(record, payload);
145	return record;
146}
147
148
149static int wifi_filter(struct ndef_record *record)
150{
151	if (record->type == NULL ||
152	    record->type_length != os_strlen(wifi_handover_type))
153		return 0;
154	if (os_memcmp(record->type, wifi_handover_type,
155		      os_strlen(wifi_handover_type)) != 0)
156		return 0;
157	return 1;
158}
159
160
161struct wpabuf * ndef_parse_wifi(const struct wpabuf *buf)
162{
163	return ndef_parse_records(buf, wifi_filter);
164}
165
166
167struct wpabuf * ndef_build_wifi(const struct wpabuf *buf)
168{
169	return ndef_build_record(FLAG_MESSAGE_BEGIN | FLAG_MESSAGE_END |
170				 FLAG_TNF_RFC2046, wifi_handover_type,
171				 os_strlen(wifi_handover_type), NULL, 0, buf);
172}
173
174
175static int p2p_filter(struct ndef_record *record)
176{
177	if (record->type == NULL ||
178	    record->type_length != os_strlen(p2p_handover_type))
179		return 0;
180	if (os_memcmp(record->type, p2p_handover_type,
181		      os_strlen(p2p_handover_type)) != 0)
182		return 0;
183	return 1;
184}
185
186
187struct wpabuf * ndef_parse_p2p(const struct wpabuf *buf)
188{
189	return ndef_parse_records(buf, p2p_filter);
190}
191
192
193struct wpabuf * ndef_build_p2p(const struct wpabuf *buf)
194{
195	return ndef_build_record(FLAG_MESSAGE_BEGIN | FLAG_MESSAGE_END |
196				 FLAG_TNF_RFC2046, p2p_handover_type,
197				 os_strlen(p2p_handover_type), NULL, 0, buf);
198}
199