Node / public / precursor-lxmfchat.git / files / xous-core / services / root-keys / src / bcrypt.rs

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// this code is based on https://github.com/Keats/rust-bcrypt

// the original crate is not used directly because the base64 wrappers cause the crate

// to be incompatible with a no-std environment. We are storing binary data directly

// in our use case.

// Cost constants

#[allow(dead_code)]

const MIN_COST: u32 = 4;

#[allow(dead_code)]

const MAX_COST: u32 = 31;

use blowfish::Blowfish;

fn setup(cost: u32, salt: &[u8], key: &[u8]) -> Blowfish {

assert!(cost < 32);

let mut state = Blowfish::bc_init_state();

state.salted_expand_key(salt, key);

for _ in 0..1u32 << cost {

state.bc_expand_key(key);

state.bc_expand_key(salt);

}

state

}

pub fn bcrypt(cost: u32, salt: &[u8], pw: &str, output: &mut [u8]) {

assert!(salt.len() == 16);

assert!(output.len() == 24);

let pw_len = if pw.len() > 72 {

log::warn!("password of length {} is truncated to 72 bytes [reason: bcrypt limitation]", pw.len());

72

} else {

pw.len() + 1

};

let mut plaintext_copy: [u8; 73] = [0; 73];

for (src, dst) in pw.bytes().zip(plaintext_copy.iter_mut()) {

*dst = src;

}

plaintext_copy[72] = 0; // always null terminate

// this function takes the plaintext key and uses it to prime a ~4k region of stack with an s-box

// that's used for the round function. The upstream Rust crypto crate does not wipe the sbox after use.

// however, it seems non-trivial to reverse the original password from the s-boxes.

let state = setup(cost, salt, &plaintext_copy[..pw_len]);

// erase the plaintext copy as soon as we're done with it

// an unsafe method is used because the compiler will correctly reason that plaintext_copy goes out of

// scope and these writes are never read, and therefore they may be optimized out.

let pt_ptr = plaintext_copy.as_mut_ptr();

for i in 0..plaintext_copy.len() {

unsafe {

pt_ptr.add(i).write_volatile(core::mem::zeroed());

}

}

core::sync::atomic::compiler_fence(core::sync::atomic::Ordering::SeqCst);

// OrpheanBeholderScryDoubt

#[allow(clippy::unreadable_literal)]

let mut ctext = [0x4f727068, 0x65616e42, 0x65686f6c, 0x64657253, 0x63727944, 0x6f756274];

for i in 0..3 {

let i: usize = i * 2;

for _ in 0..64 {

let lr = state.bc_encrypt([ctext[i], ctext[i + 1]]);

ctext[i] = lr[0];

ctext[i + 1] = lr[1];

}

let buf = ctext[i].to_be_bytes();

output[i * 4..][..4].copy_from_slice(&buf);

let buf = ctext[i + 1].to_be_bytes();

output[(i + 1) * 4..][..4].copy_from_slice(&buf);

}

}