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Zeroize output buffers at the start of all _out functions (part of #16) #18

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Merged
hubot merged 2 commits into from
Jun 10, 2026
Merged

Zeroize output buffers at the start of all _out functions (part of #16) #18

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ef214a6
출력 버퍼 zeroize 추가
Quant-TheodoreFelix Jun 9, 2026
c642ef6
리뷰 반영
Quant-TheodoreFelix Jun 10, 2026
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2 changes: 2 additions & 0 deletions crypto/base64/src/lib.rs
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Expand Up @@ -193,6 +193,8 @@ impl Base64Encoder {
assert!(inref.len() >= 3);
assert!(out.len() >= 4);

out.fill(0);

out[0] = Self::ct_bin_to_b64(inref[0] >> 2);
out[1] = Self::ct_bin_to_b64(((inref[0] & 0x03) << 4) | inref[1] >> 4);
out[2] = Self::ct_bin_to_b64(((inref[1] & 0x0F) << 2) | inref[2] >> 6);
Expand Down
4 changes: 4 additions & 0 deletions crypto/factory/src/hash_factory.rs
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Expand Up @@ -129,6 +129,8 @@ impl Hash for HashFactory {
}

fn hash_out(self, data: &[u8], output: &mut [u8]) -> usize {
output.fill(0);

match self {
Self::SHA224(h) => h.hash_out(data, output),
Self::SHA256(h) => h.hash_out(data, output),
Expand Down Expand Up @@ -168,6 +170,8 @@ impl Hash for HashFactory {
}

fn do_final_out(self, output: &mut [u8]) -> usize {
output.fill(0);

match self {
Self::SHA224(h) => h.do_final_out(output),
Self::SHA256(h) => h.do_final_out(output),
Expand Down
4 changes: 4 additions & 0 deletions crypto/factory/src/mac_factory.rs
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Expand Up @@ -175,6 +175,8 @@ impl MAC for MACFactory {
}

fn mac_out(self, data: &[u8], out: &mut [u8]) -> Result<usize, MACError> {
out.fill(0);

match self {
Self::HMAC_SHA224(h) => h.mac_out(data, out),
Self::HMAC_SHA256(h) => h.mac_out(data, out),
Expand Down Expand Up @@ -227,6 +229,8 @@ impl MAC for MACFactory {
}

fn do_final_out(self, mut out: &mut [u8]) -> Result<usize, MACError> {
out.fill(0);

match self {
Self::HMAC_SHA224(h) => h.do_final_out(&mut out),
Self::HMAC_SHA256(h) => h.do_final_out(&mut out),
Expand Down
2 changes: 2 additions & 0 deletions crypto/factory/src/rng_factory.rs
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Expand Up @@ -108,6 +108,8 @@ impl RNG for RNGFactory {
}

fn next_bytes_out(&mut self, out: &mut [u8]) -> Result<usize, RNGError> {
out.fill(0);

match self {
Self::HashDRBG_SHA256(rng) => {rng.next_bytes_out(out) },
Self::HashDRBG_SHA512(rng) => { rng.next_bytes_out(out) },
Expand Down
6 changes: 6 additions & 0 deletions crypto/factory/src/xof_factory.rs
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Expand Up @@ -86,6 +86,8 @@ impl XOF for XOFFactory {
}

fn hash_xof_out(self, data: &[u8], output: &mut [u8]) -> usize {
output.fill(0);

match self {
Self::SHAKE128(h) => h.hash_xof_out(data, output),
Self::SHAKE256(h) => h.hash_xof_out(data, output),
Expand Down Expand Up @@ -118,6 +120,8 @@ impl XOF for XOFFactory {
}

fn squeeze_out(&mut self, output: &mut [u8]) -> usize {
output.fill(0);

match self {
Self::SHAKE128(h) => h.squeeze_out(output),
Self::SHAKE256(h) => h.squeeze_out(output),
Expand All @@ -136,6 +140,8 @@ impl XOF for XOFFactory {
num_bits: usize,
output: &mut u8,
) -> Result<(), HashError> {
*output = 0;

match self {
Self::SHAKE128(h) => h.squeeze_partial_byte_final_out(num_bits, output),
Self::SHAKE256(h) => h.squeeze_partial_byte_final_out(num_bits, output),
Expand Down
4 changes: 4 additions & 0 deletions crypto/hex/src/lib.rs
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Expand Up @@ -47,6 +47,8 @@ pub fn encode_out<T: AsRef<[u8]>>(input: T, out: &mut [u8]) -> Result<usize, Hex
return Err(HexError::InsufficientOutputBufferSize);
}

out.fill(0);

for i in 0..inref.len() {
out[2 * i] = ct_word_to_hex(inref[i] >> 4);
out[2 * i + 1] = ct_word_to_hex(inref[i] & 0x0F);
Expand Down Expand Up @@ -90,6 +92,8 @@ pub fn decode_out<T: AsRef<[u8]>>(input: T, out: &mut [u8]) -> Result<usize, Hex
return Err(HexError::InsufficientOutputBufferSize);
}

out.fill(0);

let mut b = 0u8;
let mut b_i = 0u8;
let mut out_i = 0_usize;
Expand Down
6 changes: 6 additions & 0 deletions crypto/hmac/src/lib.rs
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Expand Up @@ -330,6 +330,8 @@ impl<HASH: Hash + Default> HMAC<HASH> {
));
}

out.fill(0);

// Per RFC 2104 Section 2, save our inner digest to calculate our
// outer digest. Note that we can't (necessarily) reuse out as a
// scratch pad here: if we're truncating the output but not
Expand Down Expand Up @@ -378,6 +380,8 @@ impl<HASH: Hash + Default> MAC for HMAC<HASH> {
}

fn mac_out(mut self, data: &[u8], mut out: &mut [u8]) -> Result<usize, MACError> {
out.fill(0);

self.do_update(data);
self.do_final_out(&mut out)
}
Expand All @@ -398,6 +402,8 @@ impl<HASH: Hash + Default> MAC for HMAC<HASH> {
}

fn do_final_out(self, mut out: &mut [u8]) -> Result<usize, MACError> {
out.fill(0);

self.do_final_internal_out(&mut out)
}

Expand Down
2 changes: 2 additions & 0 deletions crypto/mldsa/src/aux_functions.rs
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Expand Up @@ -397,6 +397,8 @@ pub(crate) fn sig_encode<
h: &Vector<k>,
output: &mut [u8; SIG_LEN],
) -> usize {
output.fill(0);

let mut pos = 0;

output[..LAMBDA_over_4].copy_from_slice(c_tilde);
Expand Down
12 changes: 12 additions & 0 deletions crypto/mldsa/src/hash_mldsa.rs
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Expand Up @@ -478,6 +478,8 @@ impl<
ctx: Option<&[u8]>,
output: &mut [u8; SIG_LEN],
) -> Result<usize, SignatureError> {
output.fill(0);

let mut ph_m = [0u8; PH_LEN];
_ = HASH::default().hash_out(msg, &mut ph_m);
Self::sign_ph_with_expanded_key_out(sk, &ph_m, ctx, output)
Expand All @@ -500,6 +502,8 @@ impl<
ctx: Option<&[u8]>,
output: &mut [u8; SIG_LEN],
) -> Result<usize, SignatureError> {
output.fill(0);

let mut rnd: [u8; MLDSA_RND_LEN] = [0u8; MLDSA_RND_LEN];
HashDRBG_SHA512::new_from_os().next_bytes_out(&mut rnd)?;
Self::sign_ph_deterministic_out(&sk.sk, Some(&sk.A_hat), ctx, ph, rnd, output)
Expand Down Expand Up @@ -556,6 +560,8 @@ impl<
return Err(SignatureError::LengthError("ctx value is longer than 255 bytes"));
}

output.fill(0);

// Algorithm 7
// 6: 𝜇 ← H(BytesToBits(𝑡𝑟)||𝑀', 64)
let mu = {
Expand Down Expand Up @@ -860,6 +866,8 @@ impl<
ctx: Option<&[u8]>,
output: &mut [u8; SIG_LEN],
) -> Result<usize, SignatureError> {
output.fill(0);

let mut ph_m = [0u8; PH_LEN];
_ = HASH::default().hash_out(msg, &mut ph_m);
Self::sign_ph_out(sk, &ph_m, ctx, output)
Expand Down Expand Up @@ -898,6 +906,8 @@ impl<
));
}

output.fill(0);

if self.sk.is_some() {
if self.signer_rnd.is_none() {
Self::sign_ph_out(&self.sk.unwrap(), &ph, Some(&self.ctx[..self.ctx_len]), output)
Expand Down Expand Up @@ -1045,6 +1055,8 @@ impl<
ctx: Option<&[u8]>,
output: &mut [u8; SIG_LEN],
) -> Result<usize, SignatureError> {
output.fill(0);

let mut rnd: [u8; MLDSA_RND_LEN] = [0u8; MLDSA_RND_LEN];
HashDRBG_SHA512::new_from_os().next_bytes_out(&mut rnd)?;
Self::sign_ph_deterministic_out(sk, None, ctx, ph, rnd, output)
Expand Down
14 changes: 14 additions & 0 deletions crypto/mldsa/src/mldsa.rs
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Expand Up @@ -845,6 +845,8 @@ impl<
rnd: [u8; 32],
output: &mut [u8; SIG_LEN],
) -> Result<usize, SignatureError> {
output.fill(0);

// 1: (𝜌, 𝐾, 𝑡𝑟, 𝐬1, 𝐬2, 𝐭0) ← skDecode(𝑠𝑘)
// 2: 𝐬1̂_hat ← NTT(𝐬1)
// 3: 𝐬2̂_hat ← NTT(𝐬2)
Expand Down Expand Up @@ -1134,6 +1136,8 @@ impl<
ctx: Option<&[u8]>,
out: &mut [u8; SIG_LEN],
) -> Result<usize, SignatureError> {
out.fill(0);

let mu = MuBuilder::compute_mu(&sk.tr(), msg, ctx)?;
Self::sign_mu_out(&sk.sk, Some(&sk.A_hat), &mu, out)
}
Expand All @@ -1154,6 +1158,8 @@ impl<
mu: &[u8; 64],
output: &mut [u8; SIG_LEN],
) -> Result<usize, SignatureError> {
output.fill(0);

let mut rnd: [u8; MLDSA_RND_LEN] = [0u8; MLDSA_RND_LEN];
HashDRBG_SHA512::new_from_os().next_bytes_out(&mut rnd)?;

Expand All @@ -1175,6 +1181,8 @@ impl<
mu: &[u8; 64],
out: &mut [u8; SIG_LEN],
) -> Result<usize, SignatureError> {
out.fill(0);

Self::sign_mu_out(&sk.sk, A_hat, mu, out)
}

Expand All @@ -1196,6 +1204,8 @@ impl<
rnd: [u8; 32],
output: &mut [u8; SIG_LEN],
) -> Result<usize, SignatureError> {
output.fill(0);

match A_hat {
Some(A_hat) => Self::sign_internal(sk, A_hat, mu, rnd, output),
None => Self::sign_internal(sk, &sk.A_hat(), mu, rnd, output),
Expand Down Expand Up @@ -1930,6 +1940,8 @@ impl<
ctx: Option<&[u8]>,
output: &mut [u8; SIG_LEN],
) -> Result<usize, SignatureError> {
output.fill(0);

let mu = MuBuilder::compute_mu(&sk.tr(), msg, ctx)?;
let bytes_written = Self::sign_mu_out(sk, None, &mu, output)?;

Expand Down Expand Up @@ -1966,6 +1978,8 @@ impl<
));
}

output.fill(0);

if self.sk.is_some() {
if self.signer_rnd.is_none() {
Self::sign_mu_out(&self.sk.unwrap(), None, &mu, output)
Expand Down
10 changes: 10 additions & 0 deletions crypto/mldsa/src/mldsa_keys.rs
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Expand Up @@ -203,6 +203,8 @@ impl<const k: usize, const l: usize, const PK_LEN: usize> SignaturePublicKey<PK_
}

fn encode_out(&self, out: &mut [u8; PK_LEN]) -> usize {
out.fill(0);

self.pk_encode_out(out)
}

Expand Down Expand Up @@ -279,6 +281,8 @@ impl<
}

fn encode_out(&self, out: &mut [u8; PK_LEN]) -> usize {
out.fill(0);

self.pk.encode_out(out)
}

Expand Down Expand Up @@ -431,6 +435,8 @@ impl<const k: usize, const l: usize, const eta: usize, const SK_LEN: usize, cons
/// coefficients in [−𝜂, 𝜂], 𝐭0 ∈ 𝑅𝑘 with coefficients in [−2𝑑−1 + 1, 2𝑑−1].
/// Output: Private key 𝑠𝑘 ∈ 𝔹32+32+64+32⋅((𝑘+ℓ)⋅bitlen (2𝜂)+𝑑𝑘).
fn sk_encode_out(&self, out: &mut [u8; SK_LEN]) -> usize {
out.fill(0);

// counter of progress along the output buffer
let mut off: usize = 0;

Expand Down Expand Up @@ -720,6 +726,8 @@ impl<const k: usize, const l: usize, const eta: usize, const SK_LEN: usize, cons
}

fn encode_out(&self, out: &mut [u8; SK_LEN]) -> usize {
out.fill(0);

self.sk_encode_out(out)
}

Expand Down Expand Up @@ -976,6 +984,8 @@ impl<
}

fn encode_out(&self, out: &mut [u8; SK_LEN]) -> usize {
out.fill(0);

self.sk.encode_out(out)
}

Expand Down
2 changes: 2 additions & 0 deletions crypto/mldsa_lowmemory/src/aux_functions.rs
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Expand Up @@ -167,6 +167,8 @@ pub(crate) fn bitpack_gamma1<const POLY_Z_PACKED_LEN: usize, const GAMMA1: i32>(
z: &Polynomial,
out: &mut [u8; POLY_Z_PACKED_LEN],
) {
out.fill(0);

let mut t: [u32; 4] = [0; 4];
match GAMMA1 {
MLDSA44_GAMMA1 => {
Expand Down
8 changes: 8 additions & 0 deletions crypto/mldsa_lowmemory/src/hash_mldsa.rs
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Expand Up @@ -590,6 +590,8 @@ impl<
return Err(SignatureError::LengthError("ctx value is longer than 255 bytes"));
}

output.fill(0);

// Algorithm 7
// 6: 𝜇 ← H(BytesToBits(𝑡𝑟)||𝑀', 64)
let mut h = H::new();
Expand Down Expand Up @@ -809,6 +811,8 @@ impl<
ctx: Option<&[u8]>,
output: &mut [u8; SIG_LEN],
) -> Result<usize, SignatureError> {
output.fill(0);

let mut ph_m = [0u8; PH_LEN];
_ = HASH::default().hash_out(msg, &mut ph_m);
Self::sign_ph_out(sk, &ph_m, ctx, output)
Expand Down Expand Up @@ -847,6 +851,8 @@ impl<
));
}

output.fill(0);

if self.sk.is_some() {
if self.signer_rnd.is_none() {
Self::sign_ph_out(
Expand Down Expand Up @@ -1024,6 +1030,8 @@ impl<
ctx: Option<&[u8]>,
output: &mut [u8; SIG_LEN],
) -> Result<usize, SignatureError> {
output.fill(0);

let mut rnd: [u8; MLDSA_RND_LEN] = [0u8; MLDSA_RND_LEN];
HashDRBG_SHA512::new_from_os().next_bytes_out(&mut rnd)?;
Self::sign_ph_deterministic_out(sk, ctx, ph, rnd, output)
Expand Down
8 changes: 8 additions & 0 deletions crypto/mldsa_lowmemory/src/mldsa.rs
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Expand Up @@ -949,6 +949,8 @@ impl<
mu: &[u8; 64],
output: &mut [u8; SIG_LEN],
) -> Result<usize, SignatureError> {
output.fill(0);

let mut rnd: [u8; MLDSA_RND_LEN] = [0u8; MLDSA_RND_LEN];
HashDRBG_SHA512::new_from_os().next_bytes_out(&mut rnd)?;

Expand Down Expand Up @@ -1181,6 +1183,8 @@ impl<
rnd: [u8; 32],
output: &mut [u8; SIG_LEN],
) -> Result<usize, SignatureError> {
output.fill(0);

SK::from_keymaterial(&seed)?;
Self::sign_mu_deterministic_out(&SK::from_keymaterial(&seed)?, mu, rnd, output)
}
Expand Down Expand Up @@ -1586,6 +1590,8 @@ impl<
ctx: Option<&[u8]>,
output: &mut [u8; SIG_LEN],
) -> Result<usize, SignatureError> {
output.fill(0);

let mu = MuBuilder::compute_mu(&sk.tr(), msg, ctx)?;
let bytes_written = Self::sign_mu_out(sk, &mu, output)?;

Expand Down Expand Up @@ -1622,6 +1628,8 @@ impl<
));
}

output.fill(0);

if self.sk.is_some() {
if self.signer_rnd.is_none() {
Self::sign_mu_out(&self.sk.unwrap(), &mu, output)
Expand Down
2 changes: 2 additions & 0 deletions crypto/mldsa_lowmemory/src/mldsa_keys.rs
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Expand Up @@ -183,6 +183,8 @@ impl<const k: usize, const T1_PACKED_LEN: usize, const PK_LEN: usize> SignatureP
fn encode_out(&self, out: &mut [u8; PK_LEN]) -> usize {
debug_assert_eq!(out.len(), PK_LEN);

out.fill(0);

out[..32].copy_from_slice(&self.rho);
out[32..].copy_from_slice(&self.t1_packed);

Expand Down
2 changes: 2 additions & 0 deletions crypto/mlkem/src/matrix.rs
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Expand Up @@ -171,6 +171,8 @@ impl<const k: usize> Vector<k>
// let mut s = self.clone();
// s.conditional_sub_q();

out.fill(0);

@ounsworth ounsworth Jun 10, 2026

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This one should be removed -- this is not a public function, and this will have a performance impact on the mlkem algorithm.


let mut idx = 0;
match du {
10 => { // MLKEM512 and MLKEM 768
Expand Down
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