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use crate::errors::Error;
use alloc::vec::Vec;
use core::convert::TryInto;
/// Encode `n` to little-endian bytes. The MSB is cleared.
pub fn le64(n: u64) -> [u8; core::mem::size_of::<u64>()] {
let mut out = [0u8; core::mem::size_of::<u64>()];
let mut n_tmp = n;
out[0] = (n_tmp & 255) as u8;
n_tmp >>= 8;
out[1] = (n_tmp & 255) as u8;
n_tmp >>= 8;
out[2] = (n_tmp & 255) as u8;
n_tmp >>= 8;
out[3] = (n_tmp & 255) as u8;
n_tmp >>= 8;
out[4] = (n_tmp & 255) as u8;
n_tmp >>= 8;
out[5] = (n_tmp & 255) as u8;
n_tmp >>= 8;
out[6] = (n_tmp & 255) as u8;
n_tmp >>= 8;
n_tmp &= 127; // Clear the MSB for interoperability
out[7] = (n_tmp & 255) as u8;
out
}
/// Pre-Authentication Encoding. See [specification](https://github.com/paragonie/paseto/blob/master/docs/01-Protocol-Versions/Common.md#pae-definition).
pub fn pae(pieces: &[&[u8]]) -> Result<Vec<u8>, Error> {
let mut out: Vec<u8> = Vec::with_capacity(64);
out.extend_from_slice(&le64(pieces.len().try_into()?));
for elem in pieces.iter() {
out.extend_from_slice(&le64(elem.len().try_into()?));
out.extend_from_slice(elem);
}
Ok(out)
}
#[cfg(test)]
mod unit_tests {
use super::*;
#[test]
fn test_le64() {
assert_eq!(vec![0, 0, 0, 0, 0, 0, 0, 0], le64(0));
assert_eq!(vec![10, 0, 0, 0, 0, 0, 0, 0], le64(10));
}
#[test]
fn test_pae() {
// Source: https://github.com/paragonie/paseto/blob/master/tests/UtilTest.php
assert_eq!("0000000000000000", hex::encode(pae(&[]).unwrap()));
assert_eq!(
"01000000000000000000000000000000",
hex::encode(pae(&[b""]).unwrap())
);
assert_eq!(
"020000000000000000000000000000000000000000000000",
hex::encode(pae(&[b"", b""]).unwrap())
);
assert_eq!(
"0100000000000000070000000000000050617261676f6e",
hex::encode(pae(&[b"Paragon"]).unwrap())
);
assert_eq!(
"0200000000000000070000000000000050617261676f6e0a00000000000000496e6974696174697665",
hex::encode(pae(&[b"Paragon", b"Initiative",]).unwrap())
);
assert_eq!(
"0100000000000000190000000000000050617261676f6e0a00000000000000496e6974696174697665",
hex::encode(pae(&[b"Paragon\n\0\0\0\0\0\0\0Initiative"]).unwrap())
);
}
}
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