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// ---------------- [ File: bitcoin-chacha/src/chacha_poly_aead_crypt.rs ]
crate::ix!();
impl ChaCha20Poly1305AEAD {
/// Encrypts/decrypts a packet
///
/// -seqnr_payload, the message sequence number
///
/// -seqnr_aad, the messages AAD sequence number which allows reuse of the AAD keystream
///
/// -aad_pos, position to use in the AAD keystream to encrypt the AAD
///
/// -dest, output buffer, must be of a size equal or larger then CHACHA20_POLY1305_AEAD_AAD_LEN
/// + payload (+ POLY1305_TAG_LEN in encryption) bytes
///
/// -destlen, length of the destination buffer
///
/// -src, the AAD+payload to encrypt or the AAD+payload+MAC to decrypt
///
/// -src_len, the length of the source buffer
///
/// -is_encrypt, set to true if we encrypt (creates and appends the MAC instead of verifying
/// it)
///
#[allow(clippy::too_many_arguments)]
pub fn crypt(
&mut self,
seqnr_payload: u64,
seqnr_aad: u64,
aad_pos: i32,
dest: *mut u8,
dest_len: usize,
src: *const u8,
mut src_len: usize,
is_encrypt: bool,
) -> bool {
debug!(
seqnr_payload,
seqnr_aad,
aad_pos,
src_len,
dest_len,
is_encrypt,
"ChaCha20Poly1305AEAD::crypt"
);
/* ---------- 1. bounds checks ---------- */
let need = CHACHA20_POLY1305_AEAD_AAD_LEN;
if (is_encrypt && (src_len < need || dest_len < src_len + POLY1305_TAGLEN))
|| (!is_encrypt
&& (src_len < need + POLY1305_TAGLEN
|| dest_len < src_len - POLY1305_TAGLEN))
{
return false;
}
unsafe {
let src_slice = core::slice::from_raw_parts(src, src_len);
let dest_slice =
core::slice::from_raw_parts_mut(dest, dest_len);
/* ---------- 2. derive per‑packet Poly1305 key ---------- */
let mut poly_key = [0u8; POLY1305_KEYLEN];
self.chacha_main_mut().setiv(seqnr_payload);
self.chacha_main_mut().seek(0);
self.chacha_main_mut()
.keystream(poly_key.as_mut_ptr(), POLY1305_KEYLEN);
/* ---------- 3. verify tag when decrypting ---------- */
if !is_encrypt {
let tag_offset = src_len - POLY1305_TAGLEN;
let provided_tag_ptr = src.add(tag_offset);
let calc_tag =
compute_poly1305_tag(&poly_key, &src_slice[..tag_offset]);
if timingsafe_bcmp(
calc_tag.as_ptr(),
provided_tag_ptr,
POLY1305_TAGLEN,
) != 0
{
poly_key.zeroize();
return false;
}
// exclude MAC from subsequent processing
src_len -= POLY1305_TAGLEN;
}
/* ---------- 4. AAD keystream cache ---------- */
if *self.cached_aad_seqnr() != seqnr_aad {
*self.cached_aad_seqnr_mut() = seqnr_aad;
// obtain raw pointer before borrowing `chacha_header`
let buf_ptr = self.aad_keystream_buffer_mut().as_mut_ptr();
{
let hdr = self.chacha_header_mut();
hdr.setiv(seqnr_aad);
hdr.seek(0);
hdr.keystream(buf_ptr, CHACHA20_ROUND_OUTPUT);
}
}
/* ---------- 5. crypt AAD (3 bytes) ---------- */
for i in 0..CHACHA20_POLY1305_AEAD_AAD_LEN {
dest_slice[i] =
src_slice[i]
^ self.aad_keystream_buffer()
[(aad_pos as usize) + i];
}
/* ---------- 6. crypt payload ---------- */
self.chacha_main_mut().seek(1);
self.chacha_main_mut().crypt(
src.add(CHACHA20_POLY1305_AEAD_AAD_LEN),
dest.add(CHACHA20_POLY1305_AEAD_AAD_LEN),
src_len - CHACHA20_POLY1305_AEAD_AAD_LEN,
);
/* ---------- 7. append tag when encrypting ---------- */
if is_encrypt {
let tag =
compute_poly1305_tag(&poly_key, &dest_slice[..src_len]);
dest_slice[src_len..src_len + POLY1305_TAGLEN]
.copy_from_slice(tag.as_slice());
}
/* ---------- 8. cleanse key material ---------- */
poly_key.zeroize();
memory_cleanse(
poly_key.as_mut_ptr() as *mut c_void,
poly_key.len(),
);
}
true
}
}
#[cfg(test)]
mod crypt_exhaustive_tests {
use super::*;
const K1: [u8; CHACHA20_POLY1305_AEAD_KEY_LEN] = [0x55; CHACHA20_POLY1305_AEAD_KEY_LEN];
const K2: [u8; CHACHA20_POLY1305_AEAD_KEY_LEN] = [0xAA; CHACHA20_POLY1305_AEAD_KEY_LEN];
fn build_packet(payload: &[u8]) -> Vec<u8> {
let mut v = Vec::with_capacity(3 + payload.len());
v.extend_from_slice(&[(payload.len() as u8), 0, 0]); // 24‑bit length
v.extend_from_slice(payload);
v
}
#[traced_test]
fn roundtrip_various_aad_pos_and_seq() {
let payload = b"PAYLOAD_DATA_1234567890";
let src = build_packet(payload);
for (seq_aad, aad_pos) in &[(0u64, 0i32), (1, 3), (7, 60)] {
// Encrypt
let mut enc = vec![0u8; src.len() + POLY1305_TAGLEN];
let mut aead = ChaCha20Poly1305AEAD::new(
K1.as_ptr(), K1.len(), K2.as_ptr(), K2.len(),
);
assert!(
aead.crypt(
42, // seqnr_payload
*seq_aad, // seqnr_aad
*aad_pos, // aad position
enc.as_mut_ptr(),
enc.len(),
src.as_ptr(),
src.len(),
true, // encrypt
),
"encryption must succeed (seq_aad {}, pos {})",
seq_aad, aad_pos
);
// Decrypt
let mut out = vec![0u8; src.len()];
let mut aead2 = ChaCha20Poly1305AEAD::new(
K1.as_ptr(), K1.len(), K2.as_ptr(), K2.len(),
);
assert!(
aead2.crypt(
42,
*seq_aad,
*aad_pos,
out.as_mut_ptr(),
out.len(),
enc.as_ptr(),
enc.len(),
false, // decrypt
),
"decryption must succeed (seq_aad {}, pos {})",
seq_aad, aad_pos
);
assert_eq!(out, src, "round‑trip mismatch");
}
}
#[traced_test]
fn tampered_tag_detected() {
let src = build_packet(b"1234");
let mut enc = vec![0u8; src.len() + POLY1305_TAGLEN];
let mut aead = ChaCha20Poly1305AEAD::new(K1.as_ptr(), 32, K2.as_ptr(), 32);
assert!(aead.crypt(0, 0, 0, enc.as_mut_ptr(), enc.len(), src.as_ptr(), src.len(), true));
// Flip a bit in the tag
let last = enc.len() - 1;
enc[last] ^= 0x80;
let mut out = vec![0u8; enc.len() - POLY1305_TAGLEN];
let mut aead2 = ChaCha20Poly1305AEAD::new(K1.as_ptr(), 32, K2.as_ptr(), 32);
assert!(
!aead2.crypt(0, 0, 0, out.as_mut_ptr(), out.len(), enc.as_ptr(), enc.len(), false),
"tampered tag must fail authentication"
);
}
#[traced_test]
fn invalid_buffer_lengths_rejected() {
let src = build_packet(b"abcd");
let mut small_dest = vec![0u8; src.len()]; // too small for tag
let mut aead = ChaCha20Poly1305AEAD::new(K1.as_ptr(), 32, K2.as_ptr(), 32);
assert!(
!aead.crypt(
0, 0, 0,
small_dest.as_mut_ptr(),
small_dest.len(),
src.as_ptr(),
src.len(),
true
),
"destination too small must be rejected"
);
// source too short (missing MAC)
let mut dest = vec![0u8; src.len()];
assert!(
!aead.crypt(
0, 0, 0,
dest.as_mut_ptr(),
dest.len(),
src.as_ptr(),
CHACHA20_POLY1305_AEAD_AAD_LEN + 1, // insufficient
false
),
"source lacking MAC must be rejected"
);
}
}