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 
22 struct 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 
32 static const char wifi_handover_type[] = "application/vnd.wfa.wsc";
33 static const char p2p_handover_type[] = "application/vnd.wfa.p2p";
34 
ndef_parse_record(const u8 * data,u32 size,struct ndef_record * record)35 static 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 		u32 len;
49 
50 		if (size < 6)
51 			return -1;
52 		len = WPA_GET_BE32(pos);
53 		if (len > size - 6 || len > 20000)
54 			return -1;
55 		record->payload_length = len;
56 		pos += sizeof(u32);
57 	}
58 
59 	if (data[0] & FLAG_ID_LENGTH_PRESENT) {
60 		if ((int) size < pos - data + 1)
61 			return -1;
62 		record->id_length = *pos++;
63 	} else
64 		record->id_length = 0;
65 
66 	record->type = record->type_length == 0 ? NULL : pos;
67 	pos += record->type_length;
68 
69 	record->id = record->id_length == 0 ? NULL : pos;
70 	pos += record->id_length;
71 
72 	record->payload = record->payload_length == 0 ? NULL : pos;
73 	pos += record->payload_length;
74 
75 	record->total_length = pos - data;
76 	if (record->total_length > size ||
77 	    record->total_length < record->payload_length)
78 		return -1;
79 	return 0;
80 }
81 
82 
ndef_parse_records(const struct wpabuf * buf,int (* filter)(struct ndef_record *))83 static struct wpabuf * ndef_parse_records(const struct wpabuf *buf,
84 					  int (*filter)(struct ndef_record *))
85 {
86 	struct ndef_record record;
87 	int len = wpabuf_len(buf);
88 	const u8 *data = wpabuf_head(buf);
89 
90 	while (len > 0) {
91 		if (ndef_parse_record(data, len, &record) < 0) {
92 			wpa_printf(MSG_ERROR, "NDEF : Failed to parse");
93 			return NULL;
94 		}
95 		if (filter == NULL || filter(&record))
96 			return wpabuf_alloc_copy(record.payload,
97 						 record.payload_length);
98 		data += record.total_length;
99 		len -= record.total_length;
100 	}
101 	wpa_printf(MSG_ERROR, "NDEF : Record not found");
102 	return NULL;
103 }
104 
105 
ndef_build_record(u8 flags,const void * type,u8 type_length,void * id,u8 id_length,const struct wpabuf * payload)106 static struct wpabuf * ndef_build_record(u8 flags, const void *type,
107 					 u8 type_length, void *id,
108 					 u8 id_length,
109 					 const struct wpabuf *payload)
110 {
111 	struct wpabuf *record;
112 	size_t total_len;
113 	int short_record;
114 	u8 local_flag;
115 	size_t payload_length = wpabuf_len(payload);
116 
117 	short_record = payload_length < 256 ? 1 : 0;
118 
119 	total_len = 2; /* flag + type length */
120 	/* payload length */
121 	total_len += short_record ? sizeof(u8) : sizeof(u32);
122 	if (id_length > 0)
123 		total_len += 1;
124 	total_len += type_length + id_length + payload_length;
125 	record = wpabuf_alloc(total_len);
126 	if (record == NULL) {
127 		wpa_printf(MSG_ERROR, "NDEF : Failed to allocate "
128 			   "record for build");
129 		return NULL;
130 	}
131 
132 	local_flag = flags;
133 	if (id_length > 0)
134 		local_flag |= FLAG_ID_LENGTH_PRESENT;
135 	if (short_record)
136 		local_flag |= FLAG_SHORT_RECORD;
137 	wpabuf_put_u8(record, local_flag);
138 
139 	wpabuf_put_u8(record, type_length);
140 
141 	if (short_record)
142 		wpabuf_put_u8(record, payload_length);
143 	else
144 		wpabuf_put_be32(record, payload_length);
145 
146 	if (id_length > 0)
147 		wpabuf_put_u8(record, id_length);
148 	wpabuf_put_data(record, type, type_length);
149 	wpabuf_put_data(record, id, id_length);
150 	wpabuf_put_buf(record, payload);
151 	return record;
152 }
153 
154 
wifi_filter(struct ndef_record * record)155 static int wifi_filter(struct ndef_record *record)
156 {
157 	if (record->type == NULL ||
158 	    record->type_length != os_strlen(wifi_handover_type))
159 		return 0;
160 	if (os_memcmp(record->type, wifi_handover_type,
161 		      os_strlen(wifi_handover_type)) != 0)
162 		return 0;
163 	return 1;
164 }
165 
166 
ndef_parse_wifi(const struct wpabuf * buf)167 struct wpabuf * ndef_parse_wifi(const struct wpabuf *buf)
168 {
169 	return ndef_parse_records(buf, wifi_filter);
170 }
171 
172 
ndef_build_wifi(const struct wpabuf * buf)173 struct wpabuf * ndef_build_wifi(const struct wpabuf *buf)
174 {
175 	return ndef_build_record(FLAG_MESSAGE_BEGIN | FLAG_MESSAGE_END |
176 				 FLAG_TNF_RFC2046, wifi_handover_type,
177 				 os_strlen(wifi_handover_type), NULL, 0, buf);
178 }
179 
180 
p2p_filter(struct ndef_record * record)181 static int p2p_filter(struct ndef_record *record)
182 {
183 	if (record->type == NULL ||
184 	    record->type_length != os_strlen(p2p_handover_type))
185 		return 0;
186 	if (os_memcmp(record->type, p2p_handover_type,
187 		      os_strlen(p2p_handover_type)) != 0)
188 		return 0;
189 	return 1;
190 }
191 
192 
ndef_parse_p2p(const struct wpabuf * buf)193 struct wpabuf * ndef_parse_p2p(const struct wpabuf *buf)
194 {
195 	return ndef_parse_records(buf, p2p_filter);
196 }
197 
198 
ndef_build_p2p(const struct wpabuf * buf)199 struct wpabuf * ndef_build_p2p(const struct wpabuf *buf)
200 {
201 	return ndef_build_record(FLAG_MESSAGE_BEGIN | FLAG_MESSAGE_END |
202 				 FLAG_TNF_RFC2046, p2p_handover_type,
203 				 os_strlen(p2p_handover_type), NULL, 0, buf);
204 }
205