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fix(shielded-pool)!: reject non-canonical and zero commitments and nullifiers #125

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Merged
nol4lej merged 3 commits into from
Aug 8, 2026
Merged

fix(shielded-pool)!: reject non-canonical and zero commitments and nullifiers #125

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8659002
fix(shielded-pool)!: reject non-canonical and zero commitments and nu…
nol4lej Aug 7, 2026
5c9c587
style(shielded-pool): align test comments after the canonical-value r…
nol4lej Aug 7, 2026
a7bc6fb
fix(shielded-pool): use canonical field values in benchmark fixtures
nol4lej Aug 7, 2026
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2 changes: 1 addition & 1 deletion Cargo.lock
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85 changes: 49 additions & 36 deletions frame/evm/precompile/shielded-pool/src/tests.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,19 @@ use crate::{
ShieldedPoolPrecompile,
};

/// A distinct, canonical 32-byte field value for `seed`.
///
/// Commitments and nullifiers are now checked against the BN254 modulus, and a
/// repeated byte at or above 0x30 exceeds it — `p` starts at 0x30. Real values
/// come out of Poseidon and are always canonical, so a filler that is not would
/// exercise a shape the chain never produces.
fn canon(seed: u8) -> [u8; 32] {
let mut b = [0u8; 32];
b[0] = seed;
b[1] = 0xA5;
b
}

// ─── Assertion helpers ───────────────────────────────────────────────────────

fn expect_error(result: Result<fp_evm::PrecompileOutput, PrecompileFailure>) {
Expand Down Expand Up @@ -407,7 +420,7 @@ fn shield_stores_commitment_and_updates_balance() {
fn shield_multiple_commitments_are_all_stored() {
new_test_ext().execute_with(|| {
for (i, byte) in [0x11u8, 0x22, 0x33].iter().enumerate() {
do_shield([*byte; 32], 500);
do_shield(canon(*byte), 500);
assert_eq!(
pallet_shielded_pool::MerkleTreeSize::<Test>::get(),
(i + 1) as u32
Expand All @@ -424,7 +437,7 @@ fn shield_multiple_commitments_are_all_stored() {
fn shield_updates_merkle_root_after_each_insertion() {
new_test_ext().execute_with(|| {
let root_before = current_root();
do_shield([0x42; 32], 1_000);
do_shield(canon(0x42), 1_000);
let root_after = current_root();
assert_ne!(root_before, root_after, "root must change after shield");
});
Expand All @@ -433,7 +446,7 @@ fn shield_updates_merkle_root_after_each_insertion() {
#[test]
fn shield_with_zero_value_rejected() {
new_test_ext().execute_with(|| {
let input = encode_shield(0, [0xAA; 32], &[0x00; 180]);
let input = encode_shield(0, canon(0xAA), &[0x00; 180]);
let mut h = MockHandle::with_value(input, 0);
expect_error(ShieldedPoolPrecompile::<Test>::execute(&mut h));
});
Expand All @@ -454,14 +467,14 @@ fn private_transfer_rejects_truncated_input() {
#[test]
fn private_transfer_rejects_empty_proof() {
new_test_ext().execute_with(|| {
do_shield([0x55; 32], 5_000);
do_shield(canon(0x55), 5_000);
let root = current_root();
// empty proof → MockZkVerifier returns Err
let input = encode_private_transfer(
&[],
root,
&[[0x11; 32], [0x22; 32]],
&[[0x33; 32], [0x44; 32]],
&[canon(0x33), canon(0x44)],
&[vec![0xAA; 180], vec![0xBB; 180]],
0,
0,
Expand All @@ -477,7 +490,7 @@ fn private_transfer_rejects_zero_nullifiers() {
// Calling with an empty nullifier array must be rejected at the precompile
// boundary before touching the pallet.
new_test_ext().execute_with(|| {
do_shield([0x55; 32], 5_000);
do_shield(canon(0x55), 5_000);
let root = current_root();
let input = encode_private_transfer(
&[0x01],
Expand All @@ -498,13 +511,13 @@ fn private_transfer_rejects_zero_nullifiers() {
fn private_transfer_rejects_mismatched_nullifier_commitment_count() {
// 2 nullifiers but 1 commitment — structurally inconsistent.
new_test_ext().execute_with(|| {
do_shield([0x55; 32], 5_000);
do_shield(canon(0x55), 5_000);
let root = current_root();
let input = encode_private_transfer(
&[0x01],
root,
&[[0x11; 32], [0x22; 32]], // 2 nullifiers
&[[0x33; 32]], // 1 commitment
&[canon(0x33)], // 1 commitment
&[vec![0xAA; 180]], // 1 memo
0,
0,
Expand All @@ -519,14 +532,14 @@ fn private_transfer_rejects_mismatched_nullifier_commitment_count() {
fn private_transfer_rejects_mismatched_commitment_memo_count() {
// 2 commitments but 1 memo — structurally inconsistent.
new_test_ext().execute_with(|| {
do_shield([0x55; 32], 5_000);
do_shield(canon(0x55), 5_000);
let root = current_root();
let input = encode_private_transfer(
&[0x01],
root,
&[[0x11; 32], [0x22; 32]], // 2 nullifiers
&[[0x33; 32], [0x44; 32]], // 2 commitments
&[vec![0xAA; 180]], // 1 memo — mismatch
&[[0x11; 32], [0x22; 32]], // 2 nullifiers
&[canon(0x33), canon(0x44)], // 2 commitments
&[vec![0xAA; 180]], // 1 memo — mismatch
0,
0,
1,
Expand All @@ -539,12 +552,12 @@ fn private_transfer_rejects_mismatched_commitment_memo_count() {
#[test]
fn private_transfer_happy_path() {
new_test_ext().execute_with(|| {
do_shield([0x55; 32], 5_000);
do_shield(canon(0x55), 5_000);
let root = current_root();
let nullifier_1 = [0x11; 32];
let nullifier_2 = [0x22; 32];
let commitment_1 = [0x33; 32];
let commitment_2 = [0x44; 32];
let commitment_1 = canon(0x33);
let commitment_2 = canon(0x44);

let input = encode_private_transfer(
&[0x01, 0x02, 0x03],
Expand Down Expand Up @@ -585,9 +598,9 @@ fn private_transfer_happy_path() {
#[test]
fn private_transfer_rejects_double_spend() {
new_test_ext().execute_with(|| {
do_shield([0x55; 32], 5_000);
do_shield(canon(0x55), 5_000);
let root = current_root();
let nullifier = [0xDE; 32];
let nullifier = canon(0xDE);

let input = encode_private_transfer(
&[0x01],
Expand All @@ -611,14 +624,14 @@ fn private_transfer_rejects_double_spend() {
#[test]
fn private_transfer_root_updates_after_outputs() {
new_test_ext().execute_with(|| {
do_shield([0x55; 32], 5_000);
do_shield(canon(0x55), 5_000);
let root_before = current_root();

let input = encode_private_transfer(
&[0x01],
root_before,
&[[0x11; 32], [0x22; 32]],
&[[0x33; 32], [0x44; 32]],
&[canon(0x33), canon(0x44)],
&[vec![0xAA; 180], vec![0xBB; 180]],
0,
0,
Expand Down Expand Up @@ -650,12 +663,12 @@ fn unshield_rejects_truncated_input() {
#[test]
fn unshield_rejects_empty_proof() {
new_test_ext().execute_with(|| {
do_shield([0x55; 32], 5_000);
do_shield(canon(0x55), 5_000);
let root = current_root();
let input = encode_unshield(
&[],
root,
[0x77; 32],
canon(0x77),
0,
100,
recipient_bytes(),
Expand All @@ -672,9 +685,9 @@ fn unshield_rejects_empty_proof() {
#[test]
fn unshield_happy_path() {
new_test_ext().execute_with(|| {
do_shield([0x55; 32], 5_000);
do_shield(canon(0x55), 5_000);
let root = current_root();
let nullifier = [0x77; 32];
let nullifier = canon(0x77);

let input = encode_unshield(
&[0x09, 0x09],
Expand Down Expand Up @@ -707,9 +720,9 @@ fn unshield_happy_path() {
#[test]
fn unshield_rejects_double_spend() {
new_test_ext().execute_with(|| {
do_shield([0x55; 32], 5_000);
do_shield(canon(0x55), 5_000);
let root = current_root();
let nullifier = [0x77; 32];
let nullifier = canon(0x77);

let input = encode_unshield(
&[0x09, 0x09],
Expand All @@ -734,12 +747,12 @@ fn unshield_rejects_double_spend() {
#[test]
fn unshield_full_balance() {
new_test_ext().execute_with(|| {
do_shield([0x55; 32], 1_000);
do_shield(canon(0x55), 1_000);
let root = current_root();
let input = encode_unshield(
&[0x01],
root,
[0x99; 32],
canon(0x99),
0,
1_000,
recipient_bytes(),
Expand All @@ -759,12 +772,12 @@ fn unshield_rejects_zero_recipient() {
// AccountId32 of all zeros is a permanent burn address. The precompile
// must reject it before dispatching to avoid silent token destruction.
new_test_ext().execute_with(|| {
do_shield([0x55; 32], 5_000);
do_shield(canon(0x55), 5_000);
let root = current_root();
let input = encode_unshield(
&[0x09, 0x09],
root,
[0x77; 32],
canon(0x77),
0,
100,
[0u8; 32], // zero AccountId32
Expand All @@ -783,12 +796,12 @@ fn unshield_rejects_zero_amount() {
// amount = 0 is semantically invalid and must be rejected at the precompile
// level before dispatch.
new_test_ext().execute_with(|| {
do_shield([0x55; 32], 5_000);
do_shield(canon(0x55), 5_000);
let root = current_root();
let input = encode_unshield(
&[0x09, 0x09],
root,
[0x77; 32],
canon(0x77),
0,
0, // zero amount
recipient_bytes(),
Expand All @@ -811,14 +824,14 @@ fn unshield_rejects_zero_amount() {
fn full_lifecycle_shield_transfer_unshield() {
new_test_ext().execute_with(|| {
// 1. Shield
do_shield([0xAA; 32], 10_000);
do_shield(canon(0xAA), 10_000);
assert_eq!(pallet_shielded_pool::MerkleTreeSize::<Test>::get(), 1);

// 2. Private transfer
let root_1 = current_root();
let nullifier_in = [0xBB; 32];
let commitment_out_1 = [0xCC; 32];
let commitment_out_2 = [0xDD; 32];
let nullifier_in = canon(0xBB);
let commitment_out_1 = canon(0xCC);
let commitment_out_2 = canon(0xDD);

let pt_input = encode_private_transfer(
&[0x01],
Expand All @@ -836,7 +849,7 @@ fn full_lifecycle_shield_transfer_unshield() {

// 3. Unshield one of the outputs
let root_2 = current_root();
let nullifier_out = [0xEE; 32];
let nullifier_out = canon(0xEE);
let unshield_input = encode_unshield(
&[0x02],
root_2,
Expand Down
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