nfc_step_up.c File Reference

NFC step-up messaging: compact-key CBOR encoder/decoder for Aliro DeviceRequest and SessionData (ISO 18013-5). More...

#include "nfc_step_up.h"
#include "tlv.h"
#include <string.h>

Include dependency graph for nfc_step_up.c:

Data Structures
struct	writer
	Buffered writer for composing CBOR/TLV payloads: tracks current write position and capacity. More...

Functions
static int	put (struct writer *w, const void *data, size_t length)
	Append bytes to a writer buffer.
static int	cbor_head (struct writer *w, uint8_t major, size_t value)
	Encode a CBOR head (major type + argument value) into the writer buffer.
static int	cbor_bytes (struct writer *w, uint8_t major, const uint8_t *data, size_t length)
	Encode a CBOR byte string (major type 2 or 3) or text string: emit the head (type + length) then the payload bytes.
static int	text (struct writer *w, const char *value)
	Encode a UTF-8 text string as CBOR major type 3: emit the head and the string bytes.
static int	cbor_read_head (const uint8_t *data, size_t length, size_t *offset, uint8_t major, size_t *value)
	Parse a CBOR major type and initial value from an encoded stream.
int	woz_aliro_unwrap_session_data (const uint8_t *session_data, size_t session_data_length, const uint8_t **ciphertext, size_t *ciphertext_length)
	Unwrap an ISO 18013-5 SessionData envelope (CBOR map with "data" key) to extract the encrypted ciphertext.
int	woz_aliro_unwrap_do53 (const uint8_t *encoded, size_t encoded_length, const uint8_t **message, size_t *message_length)
	Unwrap an Aliro DO'53 TLV-encoded message: extract the value of a tag-0x53 object from an encoded buffer.
int	woz_aliro_build_get_response_command (size_t expected_length, uint8_t *output, size_t output_capacity, size_t *output_length)
	Build an ISO 7816 GET RESPONSE command APDU for retrieving data from a previous response chain.

Detailed Description

NFC step-up messaging: compact-key CBOR encoder/decoder for Aliro DeviceRequest and SessionData (ISO 18013-5).

Core: put appends to writer buffer; cbor_head / cbor_bytes / text build encoded items; cbor_read_head parses with validation (non-minimal representation rejected); build_device_request constructs DeviceRequest (compact keys); wrap_session_data / unwrap_session_data encode/decode SessionData; wrap_do53 / unwrap_do53 TLV-wrap messages; build_envelope_command / build_get_response_command and collect_response chain ISO APDU commands.

Function Documentation

cbor_bytes()

static int cbor_bytes ( struct writer *  w, uint8_t  major, const uint8_t *  data, size_t  length  )

static

Encode a CBOR byte string (major type 2 or 3) or text string: emit the head (type + length) then the payload bytes.

Return WOZ_ALIRO_STEP_UP_OK on success, WOZ_ALIRO_STEP_UP_BUFFER_TOO_SMALL if appending would overflow.

cbor_head()

static int cbor_head ( struct writer *  w, uint8_t  major, size_t  value  )

static

Encode a CBOR head (major type + argument value) into the writer buffer.

Values <24 fit in 1 byte; 24–255 in 2 bytes; 256–65535 in 3 bytes; 65536–2^32−1 in 5 bytes; larger in 9 bytes. Return WOZ_ALIRO_STEP_UP_OK on success, WOZ_ALIRO_STEP_UP_BUFFER_TOO_SMALL if appending would overflow.

cbor_read_head()

static int cbor_read_head ( const uint8_t *  data, size_t  length, size_t *  offset, uint8_t  major, size_t *  value  )

static

Parse a CBOR major type and initial value from an encoded stream.

Major type is encoded in the top 3 bits of the first byte; additional info determines whether the value follows. Validates encoding: rejects non-minimal representations (e.g., a 1-byte value encoded with 2 bytes) and returns WOZ_ALIRO_STEP_UP_INVALID_DATA if the major type or additional-info field does not match expectations.

put()

static int put ( struct writer *  w, const void *  data, size_t  length  )

static

Append bytes to a writer buffer.

Returns WOZ_ALIRO_STEP_UP_OK on success, WOZ_ALIRO_STEP_UP_BUFFER_TOO_SMALL if appending would exceed capacity. Length-zero writes are allowed and do not alter the buffer.

text()

static int text ( struct writer *  w, const char *  value  )

static

Encode a UTF-8 text string as CBOR major type 3: emit the head and the string bytes.

Return WOZ_ALIRO_STEP_UP_OK on success, WOZ_ALIRO_STEP_UP_BUFFER_TOO_SMALL if appending would overflow.

woz_aliro_build_get_response_command()

int woz_aliro_build_get_response_command	(	size_t	expected_length,
		uint8_t *	output,
		size_t	output_capacity,
		size_t *	output_length
	)

Build an ISO 7816 GET RESPONSE command APDU for retrieving data from a previous response chain.

For lengths <= 256 bytes, outputs a 5-byte APDU; for lengths > 256, outputs a 7-byte extended-length APDU. Output capacity must be >= 5 or >= 7 bytes respectively. Expected length must be 1–65536.

woz_aliro_unwrap_do53()

int woz_aliro_unwrap_do53	(	const uint8_t *	encoded,
		size_t	encoded_length,
		const uint8_t **	message,
		size_t *	message_length
	)

Unwrap an Aliro DO'53 TLV-encoded message: extract the value of a tag-0x53 object from an encoded buffer.

Returns a pointer into the input buffer for the message payload and its length; the pointer is valid only as long as the input buffer is valid.

woz_aliro_unwrap_session_data()

int woz_aliro_unwrap_session_data	(	const uint8_t *	session_data,
		size_t	session_data_length,
		const uint8_t **	ciphertext,
		size_t *	ciphertext_length
	)

Unwrap an ISO 18013-5 SessionData envelope (CBOR map with "data" key) to extract the encrypted ciphertext.

Validate that SessionData is a map with exactly one entry and return a pointer into the input buffer for the ciphertext bytes and their length. Return 0 on success, WOZ_ALIRO_STEP_UP_INVALID_DATA on format error or invalid argument.