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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::Iv,
poly1305, Aad, Block, Direction, Nonce, Tag, BLOCK_LEN,
};
use crate::{aead, cpu, endian::*, error, polyfill};
use core::convert::TryInto;
/// ChaCha20-Poly1305 as described in [RFC 7539].
///
/// The keys are 256 bits long and the nonces are 96 bits long.
///
/// [RFC 7539]: https://tools.ietf.org/html/rfc7539
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],
_todo: cpu::Features,
) -> Result<aead::KeyInner, error::Unspecified> {
let key: [u8; chacha::KEY_LEN] = key.try_into()?;
Ok(aead::KeyInner::ChaCha20Poly1305(chacha::Key::from(key)))
}
fn chacha20_poly1305_seal(
key: &aead::KeyInner,
nonce: Nonce,
aad: Aad<&[u8]>,
in_out: &mut [u8],
cpu_features: cpu::Features,
) -> Tag {
let key = match key {
aead::KeyInner::ChaCha20Poly1305(key) => key,
_ => unreachable!(),
};
#[cfg(target_arch = "x86_64")]
{
if cpu::intel::SSE41.available(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: [u8; chacha::KEY_LEN],
counter: u32,
nonce: [u8; super::NONCE_LEN],
extra_ciphertext: *const u8,
extra_ciphertext_len: usize,
}
let mut data = InOut {
input: seal_data_in {
key: *key.words_less_safe().as_byte_array(),
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`.
extern "C" {
fn GFp_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 {
GFp_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);
}
}
aead(key, nonce, aad, in_out, Direction::Sealing, cpu_features)
}
fn chacha20_poly1305_open(
key: &aead::KeyInner,
nonce: Nonce,
aad: Aad<&[u8]>,
in_prefix_len: usize,
in_out: &mut [u8],
cpu_features: cpu::Features,
) -> Tag {
let key = match key {
aead::KeyInner::ChaCha20Poly1305(key) => key,
_ => unreachable!(),
};
#[cfg(target_arch = "x86_64")]
{
if cpu::intel::SSE41.available(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: [u8; chacha::KEY_LEN],
counter: u32,
nonce: [u8; super::NONCE_LEN],
}
let mut data = InOut {
input: open_data_in {
key: *key.words_less_safe().as_byte_array(),
counter: 0,
nonce: *nonce.as_ref(),
},
};
// Decrypts `plaintext_len` bytes from `ciphertext` and writes them to `out_plaintext`.
extern "C" {
fn GFp_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 {
GFp_chacha20_poly1305_open(
in_out.as_mut_ptr(),
in_out.as_ptr().add(in_prefix_len),
in_out.len() - in_prefix_len,
aad.as_ref().as_ptr(),
aad.as_ref().len(),
&mut data,
);
&data.out
};
return Tag(out.tag);
}
}
aead(
key,
nonce,
aad,
in_out,
Direction::Opening { in_prefix_len },
cpu_features,
)
}
pub type Key = chacha::Key;
// Keep in sync with BoringSSL's `chacha20_poly1305_open_data` and
// `chacha20_poly1305_seal_data`.
#[repr(C)]
#[cfg(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(target_arch = "x86_64")]
#[derive(Clone, Copy)]
#[repr(align(16), C)]
struct Out {
tag: [u8; super::TAG_LEN],
}
#[inline(always)] // Statically eliminate branches on `direction`.
fn aead(
chacha20_key: &Key,
nonce: Nonce,
Aad(aad): Aad<&[u8]>,
in_out: &mut [u8],
direction: Direction,
cpu_features: cpu::Features,
) -> Tag {
let mut counter = Counter::zero(nonce);
let mut ctx = {
let key = derive_poly1305_key(chacha20_key, counter.increment(), cpu_features);
poly1305::Context::from_key(key)
};
poly1305_update_padded_16(&mut ctx, aad);
let in_out_len = match direction {
Direction::Opening { in_prefix_len } => {
poly1305_update_padded_16(&mut ctx, &in_out[in_prefix_len..]);
chacha20_key.encrypt_overlapping(counter, in_out, in_prefix_len);
in_out.len() - in_prefix_len
}
Direction::Sealing => {
chacha20_key.encrypt_in_place(counter, in_out);
poly1305_update_padded_16(&mut ctx, in_out);
in_out.len()
}
};
ctx.update(
Block::from_u64_le(
LittleEndian::from(polyfill::u64_from_usize(aad.len())),
LittleEndian::from(polyfill::u64_from_usize(in_out_len)),
)
.as_ref(),
);
ctx.finish()
}
#[inline]
fn poly1305_update_padded_16(ctx: &mut poly1305::Context, input: &[u8]) {
let remainder_len = input.len() % BLOCK_LEN;
let whole_len = input.len() - remainder_len;
if whole_len > 0 {
ctx.update(&input[..whole_len]);
}
if remainder_len > 0 {
let mut block = Block::zero();
block.overwrite_part_at(0, &input[whole_len..]);
ctx.update(block.as_ref())
}
}
// Also used by chacha20_poly1305_openssh.
pub(super) fn derive_poly1305_key(
chacha_key: &chacha::Key,
iv: Iv,
cpu_features: cpu::Features,
) -> poly1305::Key {
let mut key_bytes = [0u8; 2 * BLOCK_LEN];
chacha_key.encrypt_iv_xor_blocks_in_place(iv, &mut key_bytes);
poly1305::Key::new(key_bytes, cpu_features)
}
#[cfg(test)]
mod tests {
#[test]
fn max_input_len_test() {
// Errata 4858 at https://www.rfc-editor.org/errata_search.php?rfc=7539.
assert_eq!(super::CHACHA20_POLY1305.max_input_len, 274_877_906_880u64);
}
}