Struct webauthn_authenticator_rs::nfc::Atr

pub struct Atr {
    pub protocols: HashSet<u8>,
    pub t1: Vec<u8>,
    pub storage_card: bool,
    pub card_issuers_data: Option<Vec<u8>>,
    pub command_chaining: Option<bool>,
    pub extended_lc: Option<bool>,
}

Available on crate feature nfc only.

ISO/IEC 7816-3 Answer-to-Reset and 7816-4 Historical Bytes parser.

This intentionally incomplete, and only supports a subset of the standards needed for compatibility with FIDO tokens.

References:

• “Answer-to-Reset”, ISO/IEC 7816-3:2005 §8.2
• “Historical bytes”, ISO/IEC 7816-4:2006 §8.1.1
• “ATR, Contactless Smart Cards”, PC/SC Specification Part 3, §3.1.3.2.3.1
• “ATR, Contactless Storage Cards”, PC/SC Specification Part 3, §3.1.3.2.3.2

Other resources:

• pyscard ATR decoder
• Ludovic Rousseau’s series about ATR bytes
• Wikipedia: Answer to reset

Fields

protocols: HashSet<u8>

Supported protocols (T=), specified in ISO/IEC 7816-3:2006 §8.2.3.

t1: Vec<u8>

Historical bytes (T₁ .. T_k), as specified in ISO/IEC 7816-4:2005 §8.1.1.

storage_card: bool

If true, this is a contactless storage card per [PC/SC Specification][pcsc-spec] Part 3, §3.1.3.2.3.2, and Part 3 Supplemental Document.

Further clarification is available in the historical bytes (Self::t1), but is beyond the scope of this module.

FIDO tokens should always return false.

card_issuers_data: Option<Vec<u8>>

Card issuer’s data (ISO/IEC 7816-4:2005 §8.1.1.2.5). The structure of this value is defined by the card issuer. This sometimes contains a printable string identifying the card issuer (see Self::card_issuers_data_str()).

command_chaining: Option<bool>

Whether the card supports command chaining (ISO/IEC 7816-4:2005 §5.1.1.1). This allows sending commands longer than 255 bytes using only short form L_c.

If this value is set to None, the card did not provide a “card capabilities” value (ISO/IEC 7816-4:2005 §8.1.1.2.7).

extended_lc: Option<bool>

Whether the card supports extended (3 byte) L_c and L_e fields (ISO/IEC 7816-4:2005 §5.1) – which allows N_c (command data length) and N_e (maximum expected response length) values from 257 to 65536 bytes.

If this value is set to None, the card did not provide a “card capabilities” value (§8.1.1.2.7), and therefore does not support extended fields (§5.1).

FIDO v2.0 requires all NFC devices support short and extended length encoding.

See: ISO7816LengthForm

Implementations

impl Atr

pub fn card_issuers_data_str(&self) -> Option<&str>

Converts Self::card_issuers_data to a UTF-8 encoded string.

Returns None if Self::card_issuers_data is missing, or if it contains invalid UTF-8.

Trait Implementations

impl Clone for Atr

fn clone(&self) -> Atr

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Atr

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl PartialEq for Atr

fn eq(&self, other: &Atr) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl TryFrom<&[u8]> for Atr

fn try_from(atr: &[u8]) -> Result<Self, Self::Error>

Attempts to parse an ATR from a &[u8].

type Error = WebauthnCError

The type returned in the event of a conversion error.

impl Eq for Atr

impl StructuralEq for Atr

impl StructuralPartialEq for Atr