Merge pull request #4 from OffchainLabs/eof-machinery

Include EOF Machinery To Differentiate Stylus Programs from EVM Bytecode
streamingfast · Jan 18, 2023 · c4fc7d6 · c4fc7d6
2 parents 1c0be5f + ea29f9c
commit c4fc7d6
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Showing 3 changed files with 47 additions and 1 deletion.
diff --git a/core/state/statedb_arbitrum.go b/core/state/statedb_arbitrum.go
@@ -24,7 +24,9 @@ import (
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/core/vm"
 	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/log"
 )
 
 func (s *StateDB) Deterministic() bool {
@@ -78,9 +80,15 @@ func (s *StateDB) RecordProgram(program common.Address, version uint32) {
 		if _, ok := s.userWasms[call]; ok {
 			return
 		}
+		rawCode := s.GetCode(program)
+		compressedWasm, err := vm.StripStylusPrefix(rawCode)
+		if err != nil {
+			log.Error("Could not strip stylus program prefix from raw code: %v", err)
+			return
+		}
 		s.userWasms[call] = &UserWasm{
 			NoncanonicalHash: s.NoncanonicalProgramHash(program, version),
-			CompressedWasm:   s.GetCode(program),
+			CompressedWasm:   compressedWasm,
 		}
 	}
 }

diff --git a/core/vm/evm.go b/core/vm/evm.go
@@ -499,6 +499,11 @@ func (evm *EVM) create(caller ContractRef, codeAndHash *codeAndHash, gas uint64,
 	// Reject code starting with 0xEF if EIP-3541 is enabled.
 	if err == nil && len(ret) >= 1 && ret[0] == 0xEF && evm.chainRules.IsLondon {
 		err = ErrInvalidCode
+		// Arbitrum: We do not reject Stylus programs and instead store them in the DB
+		// alongside normal EVM bytecode.
+		if evm.chainRules.IsArbitrum && IsStylusProgram(ret) {
+			err = nil
+		}
 	}
 
 	// if the contract creation ran successfully and no errors were returned

diff --git a/core/vm/evm_arbitrum.go b/core/vm/evm_arbitrum.go
@@ -17,12 +17,27 @@
 package vm
 
 import (
+	"errors"
 	"math/big"
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/types"
 )
 
+var (
+	// Defines prefix bytes for Stylus WASM program bytecode
+	// when deployed on-chain via a user-initiated transaction.
+	// These byte prefixes are meant to conflict with the L1 contract EOF
+	// validation rules so they can be sufficiently differentiated from EVM bytecode.
+	// This allows us to store WASM programs as code in the stateDB side-by-side
+	// with EVM contracts, but match against these prefix bytes when loading code
+	// to execute the WASMs through Stylus rather than the EVM.
+	stylusEOFMagic         = byte(0xEF)
+	stylusEOFMagicSuffix   = byte(0x00)
+	stylusEOFVersion       = byte(0x00)
+	stylusEOFSectionHeader = byte(0x00)
+)
+
 // Depth returns the current depth
 func (evm *EVM) Depth() int {
 	return evm.depth
@@ -93,3 +108,21 @@ func (p DefaultTxProcessor) GasPriceOp(evm *EVM) *big.Int {
 }
 
 func (p DefaultTxProcessor) FillReceiptInfo(*types.Receipt) {}
+
+// IsStylusProgram checks if a specified bytecode is a user-submitted WASM program.
+// Stylus differentiates WASMs from EVM bytecode via the prefix 0xEF000000 which will safely fail
+// to pass through EVM-bytecode EOF validation rules.
+func IsStylusProgram(b []byte) bool {
+	if len(b) < 4 {
+		return false
+	}
+	return b[0] == stylusEOFMagic && b[1] == stylusEOFMagicSuffix && b[2] == stylusEOFVersion && b[3] == stylusEOFSectionHeader
+}
+
+// StripStylusPrefix if the specified input is a stylus program.
+func StripStylusPrefix(b []byte) ([]byte, error) {
+	if !IsStylusProgram(b) {
+		return nil, errors.New("specified bytecode is not a Stylus program")
+	}
+	return b[4:], nil
+}