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//! This module provides tools and utilities for handling SIMPLE-TLV data as
//! defined in [ISO7816-4][iso7816-4].
//!
//!
//!
//!
//! [iso7816-4]: https://www.iso.org/standard/54550.html
//!
use alloc::vec::Vec;
use core::convert::TryFrom;
use untrusted::{Input, Reader};
use crate::{Result, TlvError};
/// Tag for SIMPLE-TLV data as defined in [ISO7816-4].
/// > The tag field consists of a single byte encoding a tag number from 1 to 254.
/// > The values '00' and 'FF' are invalid for tag fields.
///
/// Tags can be generated using the [`TryFrom`][TryFrom] trait
/// from u8 or hex [str][str].
///
/// [TryFrom]: https://doc.rust-lang.org/std/convert/trait.TryFrom.html
/// [str]:https://doc.rust-lang.org/std/str/
///
/// # Example
/// ```rust
/// use std::convert::TryFrom;
/// use iso7816_tlv::simple::Tag;
/// # use iso7816_tlv::TlvError;
/// # fn main() -> Result<(), TlvError> {
///
/// // get tag from u8 or &str
/// assert!(Tag::try_from("80").is_ok());
/// assert!(Tag::try_from(8u8).is_ok());
/// assert!(Tag::try_from(0x80).is_ok());
/// assert!(Tag::try_from(127).is_ok());
///
/// assert!(Tag::try_from("er").is_err());
/// assert!(Tag::try_from("00").is_err());
/// assert!(Tag::try_from("ff").is_err());
///
/// // get tag as u8
/// let tag = Tag::try_from("80")?;
/// let _tag_as_u8: u8 = tag.into();
/// let _tag_as_u8 = Into::<u8>::into(tag);
/// # Ok(())
/// # }
/// #
/// ```
#[derive(PartialEq, Debug, Clone, Copy)]
pub struct Tag(u8);
impl Tag {
/// Tries to convert a `u8` into a `Tag`. This is equivalent to the
/// [`TryFrom`] impl for `u8`, except that this fn is const and can be used
/// in some contexts that `TryFrom` cannot be used in, for example for
/// defining constants:
///
/// ```
/// use iso7816_tlv::simple::Tag;
///
/// const SOME_TAG_CONSTANT: Tag = match Tag::try_from_u8(0x42) {
/// Ok(tag) => tag,
/// Err(e) => panic!(),
/// };
/// ```
///
/// # Errors
/// This method returns `Err(TlvError::InvalidInput)` if `v` is not a legal
/// tag (e.g., if v is `0x00` or `0xFF`).
pub const fn try_from_u8(v: u8) -> Result<Self> {
match v {
0x00 | 0xFF => Err(TlvError::InvalidInput),
_ => Ok(Self(v)),
}
}
}
/// Value for SIMPLE-TLV data as defined in [ISO7816-4].
/// > The value field consists of N consecutive bytes.
/// > N may be zero.
/// > In this case there is no value field.
///
/// In this case Value is an empty vector
pub type Value = Vec<u8>;
/// SIMPLE-TLV data object representation.
/// > Each SIMPLE-TLV data object shall consist of two or three consecutive fields:
/// > a mandatory tag field, a mandatory length field and a conditional value field
#[derive(PartialEq, Debug, Clone)]
pub struct Tlv {
tag: Tag,
value: Value,
}
// From impl may fail, not the converse
#[allow(clippy::from_over_into)]
impl Into<u8> for Tag {
fn into(self) -> u8 {
self.0
}
}
impl TryFrom<u8> for Tag {
type Error = TlvError;
fn try_from(v: u8) -> Result<Self> {
Self::try_from_u8(v)
}
}
impl TryFrom<&str> for Tag {
type Error = TlvError;
fn try_from(v: &str) -> Result<Self> {
let x = u8::from_str_radix(v, 16)?;
Self::try_from(x)
}
}
impl Tlv {
/// Create a SIMPLE-TLV data object from valid tag and value.
/// A value has a maximum size of `65_535` bytes.
///
/// # Errors
/// Fails with `TlvError::InvalidLength` if value is longer than `65_535` bytes.
pub fn new(tag: Tag, value: Value) -> Result<Self> {
if value.len() > 65_536 {
Err(TlvError::InvalidLength)
} else {
Ok(Self { tag, value })
}
}
/// Get SIMPLE-TLV tag.
#[must_use]
pub fn tag(&self) -> Tag {
self.tag
}
/// Get SIMPLE-TLV value length
#[must_use]
pub fn length(&self) -> usize {
self.value.len()
}
/// Get SIMPLE-TLV value
#[must_use]
pub fn value(&self) -> &[u8] {
self.value.as_slice()
}
/// serializes self into a byte vector.
#[allow(clippy::cast_possible_truncation)]
#[must_use]
pub fn to_vec(&self) -> Vec<u8> {
let mut ret = vec![self.tag.0];
let len = self.value.len();
if len >= 255 {
ret.push(0xFF);
ret.push((len >> 8) as u8);
}
ret.push(len as u8);
ret.extend(&self.value);
ret
}
fn read_len(r: &mut Reader) -> Result<usize> {
let mut ret: usize = 0;
let x = r.read_byte()?;
if x == 0xFF {
for _ in 0..2 {
let x = r.read_byte()?;
ret = ret << 8 | usize::from(x);
}
} else {
ret = usize::from(x);
}
Ok(ret)
}
fn read(r: &mut Reader) -> Result<Self> {
let tag = Tag::try_from(r.read_byte()?)?;
let len = Self::read_len(r)?;
let content = r.read_bytes(len)?;
Ok(Self {
tag,
value: content.as_slice_less_safe().to_vec(),
})
}
/// Parses a byte array into a SIMPLE-TLV structure.
/// This also returns the unprocessed data.
/// # Example (parse mulitple tlv in input)
/// ```rust
/// use iso7816_tlv::simple::Tlv;
/// use hex_literal::hex;
///
/// let in_data = hex!(
/// "03 01 01"
/// "04 01 04"
/// "07 07 85 66 C9 6A 14 49 04"
/// "01 08 57 5F 93 6E 01 00 00 00"
/// "09 01 00");
/// let mut buf: &[u8] = &in_data;
/// let mut parsed_manual = Vec::new();
/// while !buf.is_empty() {
/// let (r, remaining) = Tlv::parse(buf);
/// buf = remaining;
/// if r.map(|res| parsed_manual.push(res)).is_err() {
/// break;
/// }
/// }
/// ```
pub fn parse(input: &[u8]) -> (Result<Self>, &[u8]) {
let mut r = Reader::new(Input::from(input));
(
Self::read(&mut r),
r.read_bytes_to_end().as_slice_less_safe(),
)
}
/// Parses a byte array into a vector of SIMPLE-TLV.
/// # Note
/// Errors are discarded and parsing stops at first error
/// Prefer using the [`parse()`](Self::parse()) method and iterate over returned processed data.
#[must_use]
pub fn parse_all(input: &[u8]) -> Vec<Self> {
let mut ret = Vec::new();
let mut r = Reader::new(Input::from(input));
while !r.at_end() {
if Self::read(&mut r).map(|elem| ret.push(elem)).is_err() {
break;
}
}
ret
}
/// Parses a byte array into a SIMPLE-TLV structure.
/// Input must exactly match a SIMPLE-TLV object.
/// # Errors
/// Fails with `TlvError::InvalidInput` if input does not match a SIMPLE-TLV object.
pub fn from_bytes(input: &[u8]) -> Result<Self> {
let (r, n) = Self::parse(input);
if n.is_empty() {
r
} else {
Err(TlvError::InvalidInput)
}
}
}
#[cfg(test)]
mod tests {
use super::*;
use core::convert::TryFrom;
use rand_core::{RngCore, SeedableRng};
#[test]
fn tag_import() -> Result<()> {
assert!(Tag::try_from("80").is_ok());
assert!(Tag::try_from(8_u8).is_ok());
assert_eq!(0x8_u8, Tag::try_from(8_u8)?.into());
assert!(Tag::try_from(0x80).is_ok());
assert_eq!(0x80_u8, Tag::try_from(0x80_u8)?.into());
assert!(Tag::try_from(127).is_ok());
assert_eq!(127_u8, Tag::try_from(127_u8)?.into());
assert!(Tag::try_from("er").is_err());
assert!(Tag::try_from("00").is_err());
assert!(Tag::try_from("ff").is_err());
Ok(())
}
#[test]
fn parse_1() -> Result<()> {
let in_data = [
0x84_u8, 0x01, 0x2C, 0x97, 0x00, 0x84, 0x01, 0x24, 0x9E, 0x01, 0x42,
];
let (r, in_data) = Tlv::parse(&in_data);
assert_eq!(8, in_data.len());
assert!(r.is_ok());
let t = r?;
assert_eq!(0x84_u8, t.tag().into());
assert_eq!(1, t.length());
assert_eq!(&[0x2C], t.value());
let (r, in_data) = Tlv::parse(in_data);
assert_eq!(6, in_data.len());
assert!(r.is_ok());
let t = r?;
assert_eq!(0x97_u8, t.tag().into());
assert_eq!(0, t.length());
let (r, in_data) = Tlv::parse(in_data);
assert_eq!(3, in_data.len());
assert!(r.is_ok());
let t = r?;
assert_eq!(0x84_u8, t.tag().into());
assert_eq!(1, t.length());
assert_eq!(&[0x24], t.value());
let (r, in_data) = Tlv::parse(in_data);
assert_eq!(0, in_data.len());
assert!(r.is_ok());
let t = r?;
assert_eq!(0x9E_u8, t.tag().into());
assert_eq!(1, t.length());
assert_eq!(&[0x42], t.value());
Ok(())
}
#[test]
fn parse_multiple() {
let in_data = hex!(
"03 01 01"
"04 01 04"
"07 07 85 66 C9 6A 14 49 04"
"01 08 57 5F 93 6E 01 00 00 00"
"09 01 00"
);
let mut buf: &[u8] = &in_data;
let mut parsed_manual = Vec::new();
while !buf.is_empty() {
let (r, remaining) = Tlv::parse(buf);
buf = remaining;
let pushed = r.map(|res| parsed_manual.push(res));
if pushed.is_err() {
break;
}
}
let parsed_at_once = Tlv::parse_all(&in_data);
assert_eq!(parsed_manual, parsed_at_once);
}
#[test]
#[allow(clippy::cast_possible_truncation)]
fn serialize_parse() -> Result<()> {
let mut rng = rand_xorshift::XorShiftRng::seed_from_u64(10);
for r in 1_u8..0xFF {
let v_len = rng.next_u32() % 0xFFFF;
let v: Value = (0..v_len).map(|_| rng.next_u32() as u8).collect();
let tlv = Tlv::new(Tag::try_from(r)?, v.clone())?;
let ser = tlv.to_vec();
let tlv_2 = Tlv::from_bytes(&ser)?;
assert_eq!(tlv, tlv_2);
assert_eq!(r, tlv.tag().into());
assert_eq!(v, tlv.value());
}
Ok(())
}
}