src/wps/ndef.c

   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 char wifi_handover_type[] = "application/vnd.wfa.wsc";
  33
  34 static 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
  76 static 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
  99 static 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
 148 static 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
 159 struct wpabuf * ndef_parse_wifi(const struct wpabuf *buf)
 160 {
 161         return ndef_parse_records(buf, wifi_filter);
 162 }
 163
 164
 165 struct 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 }