ndef.c

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/*
 * NDEF(NFC Data Exchange Format) routines for Wi-Fi Protected Setup
 *   Reference is "NFCForum-TS-NDEF_1.0 2006-07-24".
 * Copyright (c) 2009, Masashi Honma <honma@ictec.co.jp>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Alternatively, this software may be distributed under the terms of BSD
 * license.
 *
 * See README and COPYING for more details.
 */

#include "includes.h"
#include "common.h"
#include "wps/wps.h"
#include "wps/wps_i.h"

#define FLAG_MESSAGE_BEGIN (1 << 7)
#define FLAG_MESSAGE_END (1 << 6)
#define FLAG_CHUNK (1 << 5)
#define FLAG_SHORT_RECORD (1 << 4)
#define FLAG_ID_LENGTH_PRESENT (1 << 3)
#define FLAG_TNF_RFC2046 (0x02)

struct ndef_record {
        u8 *type;
        u8 *id;
        u8 *payload;
        u8 type_length;
        u8 id_length;
        u32 payload_length;
        u32 total_length;
};

static char wifi_handover_type[] = "application/vnd.wfa.wsc";

static int ndef_parse_record(u8 *data, u32 size, struct ndef_record *record)
{
        u8 *pos = data + 1;

        if (size < 2)
                return -1;
        record->type_length = *pos++;
        if (data[0] & FLAG_SHORT_RECORD) {
                if (size < 3)
                        return -1;
                record->payload_length = *pos++;
        } else {
                if (size < 6)
                        return -1;
                record->payload_length = ntohl(*(u32 *)pos);
                pos += sizeof(u32);
        }

        if (data[0] & FLAG_ID_LENGTH_PRESENT) {
                if ((int) size < pos - data + 1)
                        return -1;
                record->id_length = *pos++;
        } else
                record->id_length = 0;

        record->type = record->type_length == 0 ? NULL : pos;
        pos += record->type_length;

        record->id = record->id_length == 0 ? NULL : pos;
        pos += record->id_length;

        record->payload = record->payload_length == 0 ? NULL : pos;
        pos += record->payload_length;

        record->total_length = pos - data;
        if (record->total_length > size)
                return -1;
        return 0;
}


static struct wpabuf * ndef_parse_records(struct wpabuf *buf,
                                          int (*filter)(struct ndef_record *))
{
        struct ndef_record record;
        int len = wpabuf_len(buf);
        u8 *data = wpabuf_mhead(buf);

        while (len > 0) {
                if (ndef_parse_record(data, len, &record) < 0) {
                        wpa_printf(MSG_ERROR, "NDEF : Failed to parse");
                        return NULL;
                }
                if (filter == NULL || filter(&record))
                        return wpabuf_alloc_copy(record.payload,
                                                 record.payload_length);
                data += record.total_length;
                len -= record.total_length;
        }
        wpa_printf(MSG_ERROR, "NDEF : Record not found");
        return NULL;
}


static struct wpabuf * ndef_build_record(u8 flags, void *type,
                                         u8 type_length, void *id,
                                         u8 id_length, void *payload,
                                         u32 payload_length)
{
        struct wpabuf *record;
        size_t total_len;
        int short_record;
        u8 local_flag;

        short_record = payload_length < 256 ? 1 : 0;

        total_len = 2; /* flag + type length */
        /* payload length */
        total_len += short_record ? sizeof(u8) : sizeof(u32);
        if (id_length > 0)
                total_len += 1;
        total_len += type_length + id_length + payload_length;
        record = wpabuf_alloc(total_len);
        if (record == NULL) {
                wpa_printf(MSG_ERROR, "NDEF : Failed to allocate "
                           "record for build");
                return NULL;
        }

        local_flag = flags;
        if (id_length > 0)
                local_flag |= FLAG_ID_LENGTH_PRESENT;
        if (short_record)
                local_flag |= FLAG_SHORT_RECORD;
        wpabuf_put_u8(record, local_flag);

        wpabuf_put_u8(record, type_length);

        if (short_record)
                wpabuf_put_u8(record, payload_length);
        else
                wpabuf_put_be32(record, payload_length);

        if (id_length > 0)
                wpabuf_put_u8(record, id_length);
        wpabuf_put_data(record, type, type_length);
        wpabuf_put_data(record, id, id_length);
        wpabuf_put_data(record, payload, payload_length);
        return record;
}


static int wifi_filter(struct ndef_record *record)
{
        if (record->type_length != os_strlen(wifi_handover_type))
                return 0;
        if (os_memcmp(record->type, wifi_handover_type,
                      os_strlen(wifi_handover_type)) != 0)
                return 0;
        return 1;
}


struct wpabuf * ndef_parse_wifi(struct wpabuf *buf)
{
        return ndef_parse_records(buf, wifi_filter);
}


struct wpabuf * ndef_build_wifi(struct wpabuf *buf)
{
        return ndef_build_record(FLAG_MESSAGE_BEGIN | FLAG_MESSAGE_END |
                                 FLAG_TNF_RFC2046, wifi_handover_type,
                                 os_strlen(wifi_handover_type), NULL, 0,
                                 wpabuf_mhead(buf), wpabuf_len(buf));
}