ring/aead/chacha20_poly1305.rs
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// Copyright 2015-2016 Brian Smith.
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHORS DISCLAIM ALL WARRANTIES
// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
use super::{
chacha::{self, Counter, Iv},
poly1305, Aad, Nonce, Tag,
};
use crate::{
aead, cpu, error,
polyfill::{self, ArrayFlatten},
};
use core::ops::RangeFrom;
/// ChaCha20-Poly1305 as described in [RFC 8439].
///
/// The keys are 256 bits long and the nonces are 96 bits long.
///
/// [RFC 8439]: https://tools.ietf.org/html/rfc8439
pub static CHACHA20_POLY1305: aead::Algorithm = aead::Algorithm {
key_len: chacha::KEY_LEN,
init: chacha20_poly1305_init,
seal: chacha20_poly1305_seal,
open: chacha20_poly1305_open,
id: aead::AlgorithmID::CHACHA20_POLY1305,
max_input_len: super::max_input_len(64, 1),
};
/// Copies |key| into |ctx_buf|.
fn chacha20_poly1305_init(
key: &[u8],
cpu_features: cpu::Features,
) -> Result<aead::KeyInner, error::Unspecified> {
let key: [u8; chacha::KEY_LEN] = key.try_into()?;
Ok(aead::KeyInner::ChaCha20Poly1305(chacha::Key::new(
key,
cpu_features,
)))
}
fn chacha20_poly1305_seal(
key: &aead::KeyInner,
nonce: Nonce,
aad: Aad<&[u8]>,
in_out: &mut [u8],
) -> Tag {
let chacha20_key = match key {
aead::KeyInner::ChaCha20Poly1305(key) => key,
_ => unreachable!(),
};
#[cfg(any(target_arch = "aarch64", target_arch = "x86_64"))]
{
if cpu::intel::SSE41.available(chacha20_key.cpu_features())
|| cpu::arm::NEON.available(chacha20_key.cpu_features())
{
// XXX: BoringSSL uses `alignas(16)` on `key` instead of on the
// structure, but Rust can't do that yet; see
// https://github.com/rust-lang/rust/issues/73557.
//
// Keep in sync with the anonymous struct of BoringSSL's
// `chacha20_poly1305_seal_data`.
#[repr(align(16), C)]
#[derive(Clone, Copy)]
struct seal_data_in {
key: [u32; chacha::KEY_LEN / 4],
counter: u32,
nonce: [u8; super::NONCE_LEN],
extra_ciphertext: *const u8,
extra_ciphertext_len: usize,
}
let mut data = InOut {
input: seal_data_in {
key: *chacha20_key.words_less_safe(),
counter: 0,
nonce: *nonce.as_ref(),
extra_ciphertext: core::ptr::null(),
extra_ciphertext_len: 0,
},
};
// Encrypts `plaintext_len` bytes from `plaintext` and writes them to `out_ciphertext`.
prefixed_extern! {
fn chacha20_poly1305_seal(
out_ciphertext: *mut u8,
plaintext: *const u8,
plaintext_len: usize,
ad: *const u8,
ad_len: usize,
data: &mut InOut<seal_data_in>,
);
}
let out = unsafe {
chacha20_poly1305_seal(
in_out.as_mut_ptr(),
in_out.as_ptr(),
in_out.len(),
aad.as_ref().as_ptr(),
aad.as_ref().len(),
&mut data,
);
&data.out
};
return Tag(out.tag);
}
}
let mut counter = Counter::zero(nonce);
let mut auth = {
let key = derive_poly1305_key(chacha20_key, counter.increment());
poly1305::Context::from_key(key)
};
poly1305_update_padded_16(&mut auth, aad.as_ref());
chacha20_key.encrypt_in_place(counter, in_out);
poly1305_update_padded_16(&mut auth, in_out);
finish(auth, aad.as_ref().len(), in_out.len())
}
fn chacha20_poly1305_open(
key: &aead::KeyInner,
nonce: Nonce,
aad: Aad<&[u8]>,
in_out: &mut [u8],
src: RangeFrom<usize>,
) -> Tag {
let chacha20_key = match key {
aead::KeyInner::ChaCha20Poly1305(key) => key,
_ => unreachable!(),
};
#[cfg(any(target_arch = "aarch64", target_arch = "x86_64"))]
{
if cpu::intel::SSE41.available(chacha20_key.cpu_features())
|| cpu::arm::NEON.available(chacha20_key.cpu_features())
{
// XXX: BoringSSL uses `alignas(16)` on `key` instead of on the
// structure, but Rust can't do that yet; see
// https://github.com/rust-lang/rust/issues/73557.
//
// Keep in sync with the anonymous struct of BoringSSL's
// `chacha20_poly1305_open_data`.
#[derive(Copy, Clone)]
#[repr(align(16), C)]
struct open_data_in {
key: [u32; chacha::KEY_LEN / 4],
counter: u32,
nonce: [u8; super::NONCE_LEN],
}
let mut data = InOut {
input: open_data_in {
key: *chacha20_key.words_less_safe(),
counter: 0,
nonce: *nonce.as_ref(),
},
};
// Decrypts `plaintext_len` bytes from `ciphertext` and writes them to `out_plaintext`.
prefixed_extern! {
fn chacha20_poly1305_open(
out_plaintext: *mut u8,
ciphertext: *const u8,
plaintext_len: usize,
ad: *const u8,
ad_len: usize,
data: &mut InOut<open_data_in>,
);
}
let out = unsafe {
chacha20_poly1305_open(
in_out.as_mut_ptr(),
in_out.as_ptr().add(src.start),
in_out.len() - src.start,
aad.as_ref().as_ptr(),
aad.as_ref().len(),
&mut data,
);
&data.out
};
return Tag(out.tag);
}
}
let mut counter = Counter::zero(nonce);
let mut auth = {
let key = derive_poly1305_key(chacha20_key, counter.increment());
poly1305::Context::from_key(key)
};
poly1305_update_padded_16(&mut auth, aad.as_ref());
poly1305_update_padded_16(&mut auth, &in_out[src.clone()]);
chacha20_key.encrypt_within(counter, in_out, src.clone());
finish(auth, aad.as_ref().len(), in_out[src].len())
}
fn finish(mut auth: poly1305::Context, aad_len: usize, in_out_len: usize) -> Tag {
let block: [[u8; 8]; 2] = [aad_len, in_out_len]
.map(polyfill::u64_from_usize)
.map(u64::to_le_bytes);
auth.update(&block.array_flatten());
auth.finish()
}
pub type Key = chacha::Key;
// Keep in sync with BoringSSL's `chacha20_poly1305_open_data` and
// `chacha20_poly1305_seal_data`.
#[repr(C)]
#[cfg(any(target_arch = "aarch64", target_arch = "x86_64"))]
union InOut<T>
where
T: Copy,
{
input: T,
out: Out,
}
// It isn't obvious whether the assembly code works for tags that aren't
// 16-byte aligned. In practice it will always be 16-byte aligned because it
// is embedded in a union where the other member of the union is 16-byte
// aligned.
#[cfg(any(target_arch = "aarch64", target_arch = "x86_64"))]
#[derive(Clone, Copy)]
#[repr(align(16), C)]
struct Out {
tag: [u8; super::TAG_LEN],
}
#[inline]
fn poly1305_update_padded_16(ctx: &mut poly1305::Context, input: &[u8]) {
if !input.is_empty() {
ctx.update(input);
let remainder_len = input.len() % poly1305::BLOCK_LEN;
if remainder_len != 0 {
const ZEROES: [u8; poly1305::BLOCK_LEN] = [0; poly1305::BLOCK_LEN];
ctx.update(&ZEROES[..(poly1305::BLOCK_LEN - remainder_len)])
}
}
}
// Also used by chacha20_poly1305_openssh.
pub(super) fn derive_poly1305_key(chacha_key: &chacha::Key, iv: Iv) -> poly1305::Key {
let mut key_bytes = [0u8; poly1305::KEY_LEN];
chacha_key.encrypt_iv_xor_in_place(iv, &mut key_bytes);
poly1305::Key::new(key_bytes, chacha_key.cpu_features())
}
#[cfg(test)]
mod tests {
#[test]
fn max_input_len_test() {
// https://tools.ietf.org/html/rfc8439#section-2.8
assert_eq!(super::CHACHA20_POLY1305.max_input_len, 274_877_906_880u64);
}
}