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fix(host-contracts): add domain separator and prev block hash to handle hashing #2014

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mergify merged 3 commits into from
Mar 6, 2026
Merged

fix(host-contracts): add domain separator and prev block hash to handle hashing #2014

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d9f7394
fix(host-contracts): add missing domain separator when hashing to con…
antoniupop Feb 20, 2026
1d6490b
fix(host-contracts): update rust bindings
antoniupop Feb 20, 2026
268c959
feat(host-contracts): add previous block hash to the hashes used to g…
antoniupop Feb 26, 2026
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20 changes: 12 additions & 8 deletions host-contracts/contracts/FHEVMExecutor.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -140,6 +140,10 @@ contract FHEVMExecutor is UUPSUpgradeableEmptyProxy, FHEEvents, ACLOwnable {
/// identical between `initializeFromEmptyProxy` and the `reinitializeVX` method
uint64 private constant REINITIALIZER_VERSION = 3;

/// Domain separator for hashing when building an output handle for a FHE computation
bytes8 private constant COMPUTATION_DOMAIN_SEPARATOR = "FHE_comp";
bytes8 private constant SEED_DOMAIN_SEPARATOR = "FHE_seed";

/// keccak256(abi.encode(uint256(keccak256("fhevm.storage.FHEVMExecutor")) - 1)) & ~bytes32(uint256(0xff))
bytes32 private constant FHEVMExecutorStorageLocation =
0x4613e1771f6b755d243e536fb5a23c5b15e2826575fee921e8fe7a22a760c800;
Expand Down Expand Up @@ -671,7 +675,7 @@ contract FHEVMExecutor is UUPSUpgradeableEmptyProxy, FHEEvents, ACLOwnable {

/// @dev It must not cast to same type.
if (typeCt == toType) revert InvalidType();
result = keccak256(abi.encodePacked(Operators.cast, ct, toType, acl, block.chainid));
result = keccak256(abi.encodePacked(COMPUTATION_DOMAIN_SEPARATOR, Operators.cast, ct, toType, acl, block.chainid, blockhash(block.number - 1), block.timestamp));
result = _appendMetadataToPrehandle(result, toType);
hcuLimit.checkHCUForCast(toType, ct, result, msg.sender);
acl.allowTransient(result, msg.sender);
Expand All @@ -695,7 +699,7 @@ contract FHEVMExecutor is UUPSUpgradeableEmptyProxy, FHEEvents, ACLOwnable {
(1 << uint8(FheType.Uint256));

if ((1 << uint8(toType)) & supportedTypes == 0) revert UnsupportedType();
result = keccak256(abi.encodePacked(Operators.trivialEncrypt, pt, toType, acl, block.chainid));
result = keccak256(abi.encodePacked(COMPUTATION_DOMAIN_SEPARATOR, Operators.trivialEncrypt, pt, toType, acl, block.chainid, blockhash(block.number - 1), block.timestamp));
result = _appendMetadataToPrehandle(result, toType);
hcuLimit.checkHCUForTrivialEncrypt(toType, result, msg.sender);
acl.allowTransient(result, msg.sender);
Expand Down Expand Up @@ -812,7 +816,7 @@ contract FHEVMExecutor is UUPSUpgradeableEmptyProxy, FHEEvents, ACLOwnable {

function _unaryOp(Operators op, bytes32 ct) internal virtual returns (bytes32 result) {
if (!acl.isAllowed(ct, msg.sender)) revert ACLNotAllowed(ct, msg.sender);
result = keccak256(abi.encodePacked(op, ct, acl, block.chainid));
result = keccak256(abi.encodePacked(COMPUTATION_DOMAIN_SEPARATOR, op, ct, acl, block.chainid, blockhash(block.number - 1), block.timestamp));
FheType typeCt = _typeOf(ct);
result = _appendMetadataToPrehandle(result, typeCt);
acl.allowTransient(result, msg.sender);
Expand All @@ -836,7 +840,7 @@ contract FHEVMExecutor is UUPSUpgradeableEmptyProxy, FHEEvents, ACLOwnable {
FheType lhsType = _typeOf(lhs);
if (lhsType != rhsType) revert IncompatibleTypes();
}
result = keccak256(abi.encodePacked(op, lhs, rhs, scalar, acl, block.chainid));
result = keccak256(abi.encodePacked(COMPUTATION_DOMAIN_SEPARATOR, op, lhs, rhs, scalar, acl, block.chainid, blockhash(block.number - 1), block.timestamp));
result = _appendMetadataToPrehandle(result, resultType);
acl.allowTransient(result, msg.sender);
}
Expand All @@ -859,15 +863,15 @@ contract FHEVMExecutor is UUPSUpgradeableEmptyProxy, FHEEvents, ACLOwnable {
if (lhsType != FheType.Bool) revert UnsupportedType();
if (middleType != rhsType) revert IncompatibleTypes();

result = keccak256(abi.encodePacked(op, lhs, middle, rhs, acl, block.chainid));
result = keccak256(abi.encodePacked(COMPUTATION_DOMAIN_SEPARATOR, op, lhs, middle, rhs, acl, block.chainid, blockhash(block.number - 1), block.timestamp));
result = _appendMetadataToPrehandle(result, middleType);
acl.allowTransient(result, msg.sender);
}

function _generateSeed() internal virtual returns (bytes16 seed) {
FHEVMExecutorStorage storage $ = _getFHEVMExecutorStorage();
seed = bytes16(
keccak256(abi.encodePacked($.counterRand, acl, block.chainid, blockhash(block.number - 1), block.timestamp))
keccak256(abi.encodePacked(SEED_DOMAIN_SEPARATOR, $.counterRand, acl, block.chainid, blockhash(block.number - 1), block.timestamp))
);
$.counterRand++;
}
Expand All @@ -883,7 +887,7 @@ contract FHEVMExecutor is UUPSUpgradeableEmptyProxy, FHEEvents, ACLOwnable {

/// @dev Unsupported erandom type.
if ((1 << uint8(randType)) & supportedTypes == 0) revert UnsupportedType();
result = keccak256(abi.encodePacked(Operators.fheRand, randType, seed));
result = keccak256(abi.encodePacked(COMPUTATION_DOMAIN_SEPARATOR, Operators.fheRand, randType, seed));
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result = _appendMetadataToPrehandle(result, randType);
hcuLimit.checkHCUForFheRand(randType, result, msg.sender);
acl.allowTransient(result, msg.sender);
Expand All @@ -904,7 +908,7 @@ contract FHEVMExecutor is UUPSUpgradeableEmptyProxy, FHEEvents, ACLOwnable {
if ((1 << uint8(randType)) & supportedTypes == 0) revert UnsupportedType();
if (!_isPowerOfTwo(upperBound)) revert NotPowerOfTwo();
_checkBelowMaxBound(upperBound, randType);
result = keccak256(abi.encodePacked(Operators.fheRandBounded, upperBound, randType, seed));
result = keccak256(abi.encodePacked(COMPUTATION_DOMAIN_SEPARATOR, Operators.fheRandBounded, upperBound, randType, seed));
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result = _appendMetadataToPrehandle(result, randType);
hcuLimit.checkHCUForFheRandBounded(randType, result, msg.sender);
acl.allowTransient(result, msg.sender);
Expand Down
8 changes: 4 additions & 4 deletions host-contracts/rust_bindings/src/fhevm_executor.rs
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22 changes: 12 additions & 10 deletions host-contracts/test/fhevmExecutor/fhevmExecutor.t.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -213,6 +213,8 @@ contract FHEVMExecutorTest is SupportedTypesConstants, Test {
uint256 internal randomCounterForMockHandle;

uint8 internal constant HANDLE_VERSION = 0;
bytes8 internal constant COMPUTATION_DOMAIN_SEPARATOR = "FHE_comp";
bytes8 internal constant SEED_DOMAIN_SEPARATOR = "FHE_seed";
address internal constant owner = address(456);

MockACL internal acl;
Expand Down Expand Up @@ -312,7 +314,7 @@ contract FHEVMExecutorTest is SupportedTypesConstants, Test {
bytes32 handle,
FheType resultType
) internal view returns (bytes32 result) {
result = keccak256(abi.encodePacked(op, handle, acl, block.chainid));
result = keccak256(abi.encodePacked(COMPUTATION_DOMAIN_SEPARATOR, op, handle, acl, block.chainid, blockhash(block.number - 1), block.timestamp));
result = _appendMetadataToPrehandle(resultType, result, block.chainid, HANDLE_VERSION);
}

Expand All @@ -324,7 +326,7 @@ contract FHEVMExecutorTest is SupportedTypesConstants, Test {
FheType resultType
) internal view returns (bytes32 result) {
scalar = scalar & 0x01;
result = keccak256(abi.encodePacked(op, lhs, rhs, scalar, acl, block.chainid));
result = keccak256(abi.encodePacked(COMPUTATION_DOMAIN_SEPARATOR, op, lhs, rhs, scalar, acl, block.chainid, blockhash(block.number - 1), block.timestamp));
result = _appendMetadataToPrehandle(resultType, result, block.chainid, HANDLE_VERSION);
}

Expand All @@ -336,7 +338,7 @@ contract FHEVMExecutorTest is SupportedTypesConstants, Test {
FheType resultType
) internal view returns (bytes32 result) {
scalar = scalar & 0x01;
result = keccak256(abi.encodePacked(op, lhs, rhs, scalar, acl, block.chainid));
result = keccak256(abi.encodePacked(COMPUTATION_DOMAIN_SEPARATOR, op, lhs, rhs, scalar, acl, block.chainid, blockhash(block.number - 1), block.timestamp));
result = _appendMetadataToPrehandle(resultType, result, block.chainid, HANDLE_VERSION);
}

Expand All @@ -347,7 +349,7 @@ contract FHEVMExecutorTest is SupportedTypesConstants, Test {
bytes32 rhs,
FheType middleFheType
) internal view returns (bytes32 result) {
result = keccak256(abi.encodePacked(op, lhs, middle, rhs, acl, block.chainid));
result = keccak256(abi.encodePacked(COMPUTATION_DOMAIN_SEPARATOR, op, lhs, middle, rhs, acl, block.chainid, blockhash(block.number - 1), block.timestamp));
result = _appendMetadataToPrehandle(middleFheType, result, block.chainid, HANDLE_VERSION);
}

Expand Down Expand Up @@ -1044,12 +1046,12 @@ contract FHEVMExecutorTest is SupportedTypesConstants, Test {
/// @dev The first argument is the counterRand, which should be 0 for the first call.
bytes16 expectedSeed = bytes16(
keccak256(
abi.encodePacked(uint256(i), acl, block.chainid, blockhash(block.number - 1), block.timestamp)
abi.encodePacked(SEED_DOMAIN_SEPARATOR, uint256(i), acl, block.chainid, blockhash(block.number - 1), block.timestamp)
)
);

bytes32 expectedResult = keccak256(
abi.encodePacked(FHEVMExecutor.Operators.fheRand, FheType(fheType), expectedSeed)
abi.encodePacked(COMPUTATION_DOMAIN_SEPARATOR, FHEVMExecutor.Operators.fheRand, FheType(fheType), expectedSeed)
);

expectedResult = _appendMetadataToPrehandle(
Expand Down Expand Up @@ -1086,12 +1088,12 @@ contract FHEVMExecutorTest is SupportedTypesConstants, Test {
/// @dev The first argument is the counterRand, which should be 0 for the first call.
bytes16 expectedSeed = bytes16(
keccak256(
abi.encodePacked(uint256(i), acl, block.chainid, blockhash(block.number - 1), block.timestamp)
abi.encodePacked(SEED_DOMAIN_SEPARATOR, uint256(i), acl, block.chainid, blockhash(block.number - 1), block.timestamp)
)
);

bytes32 expectedResult = keccak256(
abi.encodePacked(FHEVMExecutor.Operators.fheRandBounded, upperBound, FheType(fheType), expectedSeed)
abi.encodePacked(COMPUTATION_DOMAIN_SEPARATOR, FHEVMExecutor.Operators.fheRandBounded, upperBound, FheType(fheType), expectedSeed)
);

expectedResult = _appendMetadataToPrehandle(
Expand All @@ -1116,7 +1118,7 @@ contract FHEVMExecutorTest is SupportedTypesConstants, Test {
address sender = address(123);

bytes32 expectedResult = keccak256(
abi.encodePacked(FHEVMExecutor.Operators.trivialEncrypt, pt, FheType(fheType), acl, block.chainid)
abi.encodePacked(COMPUTATION_DOMAIN_SEPARATOR, FHEVMExecutor.Operators.trivialEncrypt, pt, FheType(fheType), acl, block.chainid, blockhash(block.number - 1), block.timestamp)
);
expectedResult = _appendMetadataToPrehandle(FheType(fheType), expectedResult, block.chainid, HANDLE_VERSION);

Expand All @@ -1142,7 +1144,7 @@ contract FHEVMExecutorTest is SupportedTypesConstants, Test {
_approveHandleInACL(handle, sender);

bytes32 expectedResult = keccak256(
abi.encodePacked(FHEVMExecutor.Operators.cast, handle, FheType(fheOutputType), acl, block.chainid)
abi.encodePacked(COMPUTATION_DOMAIN_SEPARATOR, FHEVMExecutor.Operators.cast, handle, FheType(fheOutputType), acl, block.chainid, blockhash(block.number - 1), block.timestamp)
);

expectedResult = _appendMetadataToPrehandle(
Expand Down
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