arbitrum: Outsource keccak implementation for wasm

crypto/keccak.go

@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU Lesser General Public License
 // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
 
-//go:build !ziren
+//go:build !ziren && !wasm
 
 package crypto
 

crypto/keccak_wasm.go

@@ -0,0 +1,55 @@
+// Copyright 2025, Offchain Labs, Inc.
+// For license information, see https://github.com/OffchainLabs/nitro/blob/master/LICENSE.md
+
+//go:build wasm && !ziren
+
+package crypto
+
+import (
+	"unsafe"
+
+	"github.com/ethereum/go-ethereum/common"
+	"golang.org/x/crypto/sha3"
+)
+
+// NewKeccakState creates a new KeccakState
+func NewKeccakState() KeccakState {
+	return sha3.NewLegacyKeccak256().(KeccakState)
+}
+
+// Keccak256 calculates and returns the Keccak256 hash of the input data.
+func Keccak256(data ...[]byte) []byte {
+	b := make([]byte, 32)
+	keccak256Digest(b, data...)
+	return b
+}
+
+// Keccak256Hash calculates and returns the Keccak256 hash of the input data,
+// converting it to an internal Hash data structure.
+func Keccak256Hash(data ...[]byte) (h common.Hash) {
+	keccak256Digest(h[:], data...)
+	return h
+}
+
+func keccak256Digest(out []byte, data ...[]byte) {
+	if len(out) != 32 {
+		panic("output buffer must be 32 bytes")
+	}
+
+	flattenedInput := make([]byte, 0)
+	for _, b := range data {
+		flattenedInput = append(flattenedInput, b...)
+	}
+
+	var inputPtr unsafe.Pointer
+	if len(flattenedInput) > 0 {
+		inputPtr = unsafe.Pointer(&flattenedInput[0])
+	} else {
+		inputPtr = unsafe.Pointer(nil)
+	}
+
+	outsourcedKeccak(inputPtr, uint32(len(flattenedInput)), unsafe.Pointer(&out[0]))
+}
+
+//go:wasmimport arbkeccak keccak256
+func outsourcedKeccak(inBuf unsafe.Pointer, inLen uint32, outBuf unsafe.Pointer)

crypto/keccak_ziren.go

@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU Lesser General Public License
 // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
 
-//go:build ziren
+//go:build ziren && !wasm
 
 package crypto