ndef.c revision 214501 
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, Masashi Honma <honma@ictec.co.jp>
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
9 *
10 * Alternatively, this software may be distributed under the terms of BSD
11 * license.
12 *
13 * See README and COPYING for more details.
14 */
15
16#include "includes.h"
17#include "common.h"
18#include "wps/wps.h"
19#include "wps/wps_i.h"
20
21#define FLAG_MESSAGE_BEGIN (1 << 7)
22#define FLAG_MESSAGE_END (1 << 6)
23#define FLAG_CHUNK (1 << 5)
24#define FLAG_SHORT_RECORD (1 << 4)
25#define FLAG_ID_LENGTH_PRESENT (1 << 3)
26#define FLAG_TNF_RFC2046 (0x02)
27
28struct ndef_record {
29	u8 *type;
30	u8 *id;
31	u8 *payload;
32	u8 type_length;
33	u8 id_length;
34	u32 payload_length;
35	u32 total_length;
36};
37
38static char wifi_handover_type[] = "application/vnd.wfa.wsc";
39
40static int ndef_parse_record(u8 *data, u32 size, struct ndef_record *record)
41{
42	u8 *pos = data + 1;
43
44	if (size < 2)
45		return -1;
46	record->type_length = *pos++;
47	if (data[0] & FLAG_SHORT_RECORD) {
48		if (size < 3)
49			return -1;
50		record->payload_length = *pos++;
51	} else {
52		if (size < 6)
53			return -1;
54		record->payload_length = ntohl(*(u32 *)pos);
55		pos += sizeof(u32);
56	}
57
58	if (data[0] & FLAG_ID_LENGTH_PRESENT) {
59		if ((int) size < pos - data + 1)
60			return -1;
61		record->id_length = *pos++;
62	} else
63		record->id_length = 0;
64
65	record->type = record->type_length == 0 ? NULL : pos;
66	pos += record->type_length;
67
68	record->id = record->id_length == 0 ? NULL : pos;
69	pos += record->id_length;
70
71	record->payload = record->payload_length == 0 ? NULL : pos;
72	pos += record->payload_length;
73
74	record->total_length = pos - data;
75	if (record->total_length > size)
76		return -1;
77	return 0;
78}
79
80
81static struct wpabuf * ndef_parse_records(struct wpabuf *buf,
82					  int (*filter)(struct ndef_record *))
83{
84	struct ndef_record record;
85	int len = wpabuf_len(buf);
86	u8 *data = wpabuf_mhead(buf);
87
88	while (len > 0) {
89		if (ndef_parse_record(data, len, &record) < 0) {
90			wpa_printf(MSG_ERROR, "NDEF : Failed to parse");
91			return NULL;
92		}
93		if (filter == NULL || filter(&record))
94			return wpabuf_alloc_copy(record.payload,
95						 record.payload_length);
96		data += record.total_length;
97		len -= record.total_length;
98	}
99	wpa_printf(MSG_ERROR, "NDEF : Record not found");
100	return NULL;
101}
102
103
104static struct wpabuf * ndef_build_record(u8 flags, void *type,
105					 u8 type_length, void *id,
106					 u8 id_length, void *payload,
107					 u32 payload_length)
108{
109	struct wpabuf *record;
110	size_t total_len;
111	int short_record;
112	u8 local_flag;
113
114	short_record = payload_length < 256 ? 1 : 0;
115
116	total_len = 2; /* flag + type length */
117	/* payload length */
118	total_len += short_record ? sizeof(u8) : sizeof(u32);
119	if (id_length > 0)
120		total_len += 1;
121	total_len += type_length + id_length + payload_length;
122	record = wpabuf_alloc(total_len);
123	if (record == NULL) {
124		wpa_printf(MSG_ERROR, "NDEF : Failed to allocate "
125			   "record for build");
126		return NULL;
127	}
128
129	local_flag = flags;
130	if (id_length > 0)
131		local_flag |= FLAG_ID_LENGTH_PRESENT;
132	if (short_record)
133		local_flag |= FLAG_SHORT_RECORD;
134	wpabuf_put_u8(record, local_flag);
135
136	wpabuf_put_u8(record, type_length);
137
138	if (short_record)
139		wpabuf_put_u8(record, payload_length);
140	else
141		wpabuf_put_be32(record, payload_length);
142
143	if (id_length > 0)
144		wpabuf_put_u8(record, id_length);
145	wpabuf_put_data(record, type, type_length);
146	wpabuf_put_data(record, id, id_length);
147	wpabuf_put_data(record, payload, payload_length);
148	return record;
149}
150
151
152static int wifi_filter(struct ndef_record *record)
153{
154	if (record->type_length != os_strlen(wifi_handover_type))
155		return 0;
156	if (os_memcmp(record->type, wifi_handover_type,
157		      os_strlen(wifi_handover_type)) != 0)
158		return 0;
159	return 1;
160}
161
162
163struct wpabuf * ndef_parse_wifi(struct wpabuf *buf)
164{
165	return ndef_parse_records(buf, wifi_filter);
166}
167
168
169struct wpabuf * ndef_build_wifi(struct wpabuf *buf)
170{
171	return ndef_build_record(FLAG_MESSAGE_BEGIN | FLAG_MESSAGE_END |
172				 FLAG_TNF_RFC2046, wifi_handover_type,
173				 os_strlen(wifi_handover_type), NULL, 0,
174				 wpabuf_mhead(buf), wpabuf_len(buf));
175}
176