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|
//! Implementation of AEAD using pure Rust cryptographic libraries.
use std::cmp;
use std::cmp::Ordering;
use cipher::{BlockCipher, BlockEncrypt, BlockSizeUser, KeyInit, Unsigned};
use cipher::consts::{U12, U16};
use eax::online::{Eax, Encrypt, Decrypt};
use generic_array::GenericArray;
use crate::{Error, Result};
use crate::crypto::aead::{Aead, CipherOp};
use crate::crypto::mem::secure_cmp;
use crate::seal;
use crate::types::{AEADAlgorithm, SymmetricAlgorithm};
use super::GenericArrayExt;
/// Disables authentication checks.
///
/// This is DANGEROUS, and is only useful for debugging problems with
/// malformed AEAD-encrypted messages.
const DANGER_DISABLE_AUTHENTICATION: bool = false;
type TagLen = U16;
impl<Cipher> Aead for Eax<Cipher, Encrypt, TagLen>
where
Cipher: BlockCipher<BlockSize = U16> + BlockEncrypt + Clone + KeyInit,
{
fn digest_size(&self) -> usize {
TagLen::USIZE
}
fn encrypt_seal(&mut self, dst: &mut [u8], src: &[u8]) -> Result<()> {
debug_assert_eq!(dst.len(), src.len() + self.digest_size());
let len = cmp::min(dst.len(), src.len());
dst[..len].copy_from_slice(&src[..len]);
Self::encrypt(self, &mut dst[..len]);
let tag = self.tag_clone();
dst[src.len()..].copy_from_slice(&tag[..]);
Ok(())
}
fn decrypt_verify(&mut self, _dst: &mut [u8], _src: &[u8]) -> Result<()> {
panic!("AEAD decryption called in the encryption context")
}
}
impl<Cipher> Aead for Eax<Cipher, Decrypt, TagLen>
where
Cipher: BlockCipher<BlockSize = U16> + BlockEncrypt + Clone + KeyInit,
{
fn digest_size(&self) -> usize {
TagLen::USIZE
}
fn encrypt_seal(&mut self, _dst: &mut [u8], _src: &[u8]) -> Result<()> {
panic!("AEAD encryption called in the decryption context")
}
fn decrypt_verify(&mut self, dst: &mut [u8], src: &[u8]) -> Result<()> {
debug_assert_eq!(dst.len() + self.digest_size(), src.len());
// Split src into ciphertext and digest.
let l = self.digest_size();
let digest = &src[src.len().saturating_sub(l)..];
let src = &src[..src.len().saturating_sub(l)];
let len = core::cmp::min(dst.len(), src.len());
dst[..len].copy_from_slice(&src[..len]);
self.decrypt_unauthenticated_hazmat(&mut dst[..len]);
let chunk_digest = self.tag_clone();
if secure_cmp(&chunk_digest[..], digest)
!= Ordering::Equal && ! DANGER_DISABLE_AUTHENTICATION
{
return Err(Error::ManipulatedMessage.into());
}
Ok(())
}
}
impl<Cipher, Op> seal::Sealed for Eax<Cipher, Op, TagLen>
where
Cipher: BlockCipher<BlockSize = U16> + BlockEncrypt + Clone + KeyInit,
Op: eax::online::CipherOp,
{}
struct Gcm<Cipher: BlockCipher + BlockSizeUser<BlockSize = U16> + BlockEncrypt> {
cipher: aes_gcm::AesGcm<Cipher, U12>,
nonce: GenericArray<u8, U12>,
aad: Vec<u8>,
}
impl<Cipher> Aead for Gcm<Cipher>
where
Cipher: BlockCipher + BlockSizeUser<BlockSize = U16> + BlockEncrypt,
{
fn digest_size(&self) -> usize {
TagLen::USIZE
}
fn encrypt_seal(&mut self, dst: &mut [u8], src: &[u8]) -> Result<()> {
debug_assert_eq!(dst.len(), src.len() + self.digest_size());
use aes_gcm::AeadInPlace;
let len = cmp::min(dst.len(), src.len());
dst[..len].copy_from_slice(&src[..len]);
let tag =
self.cipher.encrypt_in_place_detached(&self.nonce, &self.aad,
&mut dst[..len])?;
debug_assert_eq!(dst[len..].len(), tag.len());
let tag_len = cmp::min(dst[len..].len(), tag.len());
dst[len..len + tag_len].copy_from_slice(&tag[..tag_len]);
Ok(())
}
fn decrypt_verify(&mut self, dst: &mut [u8], src: &[u8]) -> Result<()> {
debug_assert_eq!(dst.len() + self.digest_size(), src.len());
use aes_gcm::AeadInPlace;
// Split src into ciphertext and digest.
let len = src.len().saturating_sub(self.digest_size());
let digest = &src[len..];
let src = &src[..len];
debug_assert_eq!(dst.len(), src.len());
let len = core::cmp::min(dst.len(), src.len());
dst[..len].copy_from_slice(&src[..len]);
self.cipher.decrypt_in_place_detached(&self.nonce, &self.aad, dst,
digest.try_into()?)?;
Ok(())
}
}
impl<'a, Cipher> seal::Sealed for Gcm<Cipher>
where
Cipher: BlockCipher + BlockSizeUser<BlockSize = U16> + BlockEncrypt,
{}
impl AEADAlgorithm {
pub(crate) fn context(
&self,
sym_algo: SymmetricAlgorithm,
key: &[u8],
aad: &[u8],
nonce: &[u8],
op: CipherOp,
) -> Result<Box<dyn Aead>> {
match self {
AEADAlgorithm::EAX => match sym_algo {
SymmetricAlgorithm::AES128 => match op {
CipherOp::Encrypt =>
|
