111 lines
3.4 KiB
C
111 lines
3.4 KiB
C
// Minimal NDEF parser: finds the first record in a raw tag dump and accepts
|
|
// only a short text record, whose text becomes the node's "name,diameter"
|
|
// identity string.
|
|
|
|
#include "ndef.h"
|
|
// Everything read here comes off an NFC tag that anyone can write, so every
|
|
// length taken from the buffer is bounds-checked before it is used.
|
|
#define NDEF_NEED(n) \
|
|
{ \
|
|
if ((addr + (uint16_t)(n)) > buf_len) { \
|
|
NDEF_MSG.success = NDEF_ERR_TRUNCATED; \
|
|
return NDEF_MSG; \
|
|
} \
|
|
}
|
|
|
|
ndef_message readNDEFText(unsigned char* buf, uint8_t buf_len)
|
|
{
|
|
uint16_t addr = 0;
|
|
NDEF_MSG.success = 0;
|
|
NDEF_MSG.payload_len = 0;
|
|
NDEF_MSG.payload[0] = '\0';
|
|
|
|
NDEF_NEED(2);
|
|
if (buf[0] != NDEF_TLV) {
|
|
NDEF_MSG.success = 1;
|
|
return NDEF_MSG;
|
|
}
|
|
|
|
if (buf[1] == 0xFF) {
|
|
NDEF_MSG.success = 2;
|
|
return NDEF_MSG;
|
|
};
|
|
|
|
// int len_field = buf[1];
|
|
addr = 2;
|
|
|
|
NDEF_NEED(3);
|
|
// bool is_short_record = (buf[addr] & NDEF_SHORT_RECORD) == NDEF_SHORT_RECORD;
|
|
bool has_id_length = (buf[addr] & NDEF_ID_LEN) == NDEF_ID_LEN;
|
|
uint8_t tnf = buf[addr] & 0x7;
|
|
addr += 1; // 3
|
|
|
|
uint8_t type_length = buf[addr];
|
|
addr += 1; // 4
|
|
|
|
uint8_t payload_length = buf[addr];
|
|
addr += 1; // 5
|
|
|
|
uint8_t id_length = 0;
|
|
if (has_id_length) {
|
|
NDEF_NEED(1);
|
|
id_length = buf[addr];
|
|
addr += 1;
|
|
}
|
|
|
|
// Only the first type byte is ever inspected, so skip the rest rather than
|
|
// copying them into a tag-sized VLA.
|
|
NDEF_NEED(type_length);
|
|
uint8_t type_value_0 = (type_length > 0) ? buf[addr] : 0;
|
|
addr += type_length;
|
|
|
|
if (type_value_0 != NDEF_TEXT_RECORD) {
|
|
NDEF_MSG.success = 11;
|
|
return NDEF_MSG;
|
|
};
|
|
if (tnf != TNF_KNOWN) {
|
|
NDEF_MSG.success = 12;
|
|
return NDEF_MSG;
|
|
};
|
|
|
|
if (has_id_length && (id_length > 0)) {
|
|
NDEF_NEED(id_length);
|
|
addr += id_length;
|
|
}
|
|
|
|
NDEF_NEED(1);
|
|
uint8_t lang_str_len = buf[addr];
|
|
|
|
// payload_length covers the language-length byte plus the language code
|
|
// plus the text. Subtracting without this check wraps a uint8_t to ~250.
|
|
if (payload_length < ((uint16_t)lang_str_len + 1)) {
|
|
NDEF_MSG.success = NDEF_ERR_BAD_LENGTH;
|
|
return NDEF_MSG;
|
|
}
|
|
payload_length -= lang_str_len; // Language string
|
|
payload_length -= 1; // The byte that says how long the language string is
|
|
|
|
NDEF_NEED((uint16_t)lang_str_len + 1);
|
|
addr += lang_str_len;
|
|
addr += 1;
|
|
|
|
// Leave room for the terminator the UART print and strchr() both rely on.
|
|
if (payload_length > (sizeof(NDEF_MSG.payload) - 1)) {
|
|
payload_length = sizeof(NDEF_MSG.payload) - 1;
|
|
}
|
|
NDEF_NEED(payload_length);
|
|
|
|
for (uint8_t i = 0; i < (payload_length); i++) {
|
|
NDEF_MSG.payload[i] = buf[addr];
|
|
addr += 1;
|
|
}
|
|
NDEF_MSG.payload[payload_length] = '\0';
|
|
NDEF_MSG.payload_len = payload_length;
|
|
|
|
#if DO_UART
|
|
uart_sendString(NDEF_MSG.payload); // Runtime string, so not LOG()
|
|
#endif
|
|
LOG("\n");
|
|
|
|
return NDEF_MSG;
|
|
}; |