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fix(aes-gcm): reject empty nonces #885

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43 changes: 35 additions & 8 deletions aes-gcm/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -90,9 +90,7 @@ pub use aes;
use aead::{TagPosition, inout::InOutBuf};

use cipher::{
BlockCipherEncrypt, BlockSizeUser, InnerIvInit, StreamCipherCore,
array::{Array, ArraySize},
consts::U16,
BlockCipherEncrypt, BlockSizeUser, InnerIvInit, StreamCipherCore, array::Array, consts::U16,
};
use core::{fmt, marker::PhantomData};
use ghash::{GHash, universal_hash::UniversalHash};
Expand All @@ -115,6 +113,12 @@ pub type Nonce<NonceSize> = Array<u8, NonceSize>;
/// AES-GCM tags.
pub type Tag<TagSize = U16> = Array<u8, TagSize>;

/// Trait implemented for valid nonce sizes, i.e. non-zero sizes as required
/// by NIST SP 800-38D Section 5.2.1.1.
pub trait NonceSize: private::SealedNonceSize {}

impl<T: private::SealedNonceSize> NonceSize for T {}

/// Trait implemented for valid tag sizes, i.e.
/// [`U12`][consts::U12], [`U13`][consts::U13], [`U14`][consts::U14],
/// [`U15`][consts::U15] and [`U16`][consts::U16].
Expand All @@ -125,7 +129,16 @@ pub trait TagSize: private::SealedTagSize {}
impl<T: private::SealedTagSize> TagSize for T {}

mod private {
use cipher::{array::ArraySize, consts, typenum::Unsigned};
use cipher::{
array::ArraySize,
consts,
typenum::{NonZero, Unsigned},
};

// Sealed traits stop other crates from implementing any traits that use it.
pub trait SealedNonceSize: ArraySize + Unsigned {}

impl<T> SealedNonceSize for T where T: ArraySize + Unsigned + NonZero {}

// Sealed traits stop other crates from implementing any traits that use it.
pub trait SealedTagSize: ArraySize + Unsigned {}
Expand Down Expand Up @@ -167,7 +180,7 @@ type Ctr32BE<Aes> = ctr::CtrCore<Aes, ctr::flavors::Ctr32BE>;
/// Doing so runs the risk of unintended cryptographic properties!
///
/// The `NonceSize` generic parameter can be used to instantiate AES-GCM with other
/// nonce sizes, however it's recommended to use it with `typenum::U12`,
/// non-zero nonce sizes, however it's recommended to use it with `typenum::U12`,
/// the default of 96-bits.
///
/// The `TagSize` generic parameter can be used to instantiate AES-GCM with other
Expand All @@ -176,6 +189,14 @@ type Ctr32BE<Aes> = ctr::CtrCore<Aes, ctr::flavors::Ctr32BE>;
///
/// If in doubt, use the built-in [`Aes128Gcm`] and [`Aes256Gcm`] type aliases.
///
/// Compilation will fail if the nonce size is zero:
///
/// ```rust,compile_fail
/// # use aes_gcm::{AesGcm, aead::{KeyInit, consts::U0}, aes::Aes128};
/// # let key = [42; 16].into();
/// let cipher = AesGcm::<Aes128, U0>::new(&key);
/// ```
///
/// # ⚠️ WARNING: Hazmat!
///
/// When using short authentication tags, namely 32-bit tags with `typenum::U4` or
Expand All @@ -186,6 +207,7 @@ type Ctr32BE<Aes> = ctr::CtrCore<Aes, ctr::flavors::Ctr32BE>;
#[derive(Clone)]
pub struct AesGcm<Aes, NonceSize, TagSize = U16>
where
NonceSize: crate::NonceSize,
TagSize: crate::TagSize,
{
/// Encryption cipher.
Expand All @@ -204,6 +226,7 @@ where
impl<Aes, NonceSize, TagSize> KeySizeUser for AesGcm<Aes, NonceSize, TagSize>
where
Aes: KeySizeUser,
NonceSize: crate::NonceSize,
TagSize: crate::TagSize,
{
type KeySize = Aes::KeySize;
Expand All @@ -212,6 +235,7 @@ where
impl<Aes, NonceSize, TagSize> KeyInit for AesGcm<Aes, NonceSize, TagSize>
where
Aes: BlockSizeUser<BlockSize = U16> + BlockCipherEncrypt + KeyInit,
NonceSize: crate::NonceSize,
TagSize: crate::TagSize,
{
fn new(key: &Key<Self>) -> Self {
Expand All @@ -222,6 +246,7 @@ where
impl<Aes, NonceSize, TagSize> From<Aes> for AesGcm<Aes, NonceSize, TagSize>
where
Aes: BlockSizeUser<BlockSize = U16> + BlockCipherEncrypt,
NonceSize: crate::NonceSize,
TagSize: crate::TagSize,
{
fn from(cipher: Aes) -> Self {
Expand All @@ -244,7 +269,7 @@ where

impl<Aes, NonceSize, TagSize> AeadCore for AesGcm<Aes, NonceSize, TagSize>
where
NonceSize: ArraySize,
NonceSize: crate::NonceSize,
TagSize: crate::TagSize,
{
type NonceSize = NonceSize;
Expand All @@ -255,7 +280,7 @@ where
impl<Aes, NonceSize, TagSize> AeadInOut for AesGcm<Aes, NonceSize, TagSize>
where
Aes: BlockSizeUser<BlockSize = U16> + BlockCipherEncrypt,
NonceSize: ArraySize,
NonceSize: crate::NonceSize,
TagSize: crate::TagSize,
{
fn encrypt_inout_detached(
Expand Down Expand Up @@ -310,7 +335,7 @@ where
impl<Aes, NonceSize, TagSize> AesGcm<Aes, NonceSize, TagSize>
where
Aes: BlockSizeUser<BlockSize = U16> + BlockCipherEncrypt,
NonceSize: ArraySize,
NonceSize: crate::NonceSize,
TagSize: crate::TagSize,
{
/// Initialize counter mode.
Expand Down Expand Up @@ -370,6 +395,7 @@ where

impl<Aes, NonceSize, TagSize> fmt::Debug for AesGcm<Aes, NonceSize, TagSize>
where
NonceSize: crate::NonceSize,
TagSize: crate::TagSize,
{
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
Expand All @@ -384,6 +410,7 @@ where
impl<Aes, NonceSize, TagSize> zeroize::ZeroizeOnDrop for AesGcm<Aes, NonceSize, TagSize>
where
Aes: zeroize::ZeroizeOnDrop,
NonceSize: self::NonceSize,
TagSize: self::TagSize,
{
}