feat!: disambiguate EVM-semantic and raw caller/self addresses for precompiles (#211)

## Why this should be merged

Provides precompiles with unambiguous access to contextual addresses,
without the consumer needing to understand how they change under
different call types.

## How this works

The `libevm.AddressContext` type, which used to carry 3 addresses, now
provides different versions of `Caller` and `Self`. The EVM-semantic
versions are as defined by the rules of the EVM (and available before
this change). The raw versions are the unmodified caller and self.

## How this was tested

Extension of existing UTs to include raw addresses in addition to
existing, EVM-semantic ones.

Author: ARR4N

core/vm/contracts.libevm.go

@@ -223,9 +223,11 @@ func (args *evmCallArgs) env() *environment {
 	}
 
 	return &environment{
-		evm:      args.evm,
-		self:     contract,
-		callType: args.callType,
+		evm:       args.evm,
+		self:      contract,
+		callType:  args.callType,
+		rawCaller: args.caller.Address(),
+		rawSelf:   args.addr,
 	}
 }
 

core/vm/contracts.libevm_test.go

@@ -120,6 +120,7 @@ type statefulPrecompileOutput struct {
 func (o statefulPrecompileOutput) String() string {
 	var lines []string
 	out := reflect.ValueOf(o)
+FieldLoop:
 	for i, n := 0, out.NumField(); i < n; i++ {
 		name := out.Type().Field(i).Name
 		fld := out.Field(i).Interface()
@@ -129,7 +130,12 @@ func (o statefulPrecompileOutput) String() string {
 		case []byte:
 			verb = "%#x"
 		case *libevm.AddressContext:
-			verb = "%+v"
+			lines = append(
+				lines,
+				fmt.Sprintf("EVMSemantic addresses: %+v", o.Addresses.EVMSemantic),
+				fmt.Sprintf("Raw addresses: %+v", o.Addresses.Raw),
+			)
+			continue FieldLoop
 		case vm.CallType:
 			verb = "%d (%[2]q)"
 		}
@@ -211,6 +217,13 @@ func TestNewStatefulPrecompile(t *testing.T) {
 	state.SetBalance(caller, new(uint256.Int).Not(uint256.NewInt(0)))
 	evm.Origin = eoa
 
+	// By definition, the raw caller and self are the same for every test case,
+	// regardless of the incoming call type.
+	rawAddresses := libevm.CallerAndSelf{
+		Caller: caller,
+		Self:   precompile,
+	}
+
 	tests := []struct {
 		name              string
 		call              func() ([]byte, uint64, error)
@@ -227,9 +240,9 @@ func TestNewStatefulPrecompile(t *testing.T) {
 				return evm.Call(callerContract, precompile, input, gasLimit, transferValue)
 			},
 			wantAddresses: &libevm.AddressContext{
-				Origin: eoa,
-				Caller: caller,
-				Self:   precompile,
+				Origin:      eoa,
+				EVMSemantic: rawAddresses,
+				Raw:         &rawAddresses,
 			},
 			wantReadOnly:      false,
 			wantTransferValue: transferValue,
@@ -242,8 +255,11 @@ func TestNewStatefulPrecompile(t *testing.T) {
 			},
 			wantAddresses: &libevm.AddressContext{
 				Origin: eoa,
-				Caller: caller,
-				Self:   caller,
+				EVMSemantic: libevm.CallerAndSelf{
+					Caller: caller,
+					Self:   caller,
+				},
+				Raw: &rawAddresses,
 			},
 			wantReadOnly:      false,
 			wantTransferValue: transferValue,
@@ -256,8 +272,11 @@ func TestNewStatefulPrecompile(t *testing.T) {
 			},
 			wantAddresses: &libevm.AddressContext{
 				Origin: eoa,
-				Caller: eoa, // inherited from caller
-				Self:   caller,
+				EVMSemantic: libevm.CallerAndSelf{
+					Caller: eoa, // inherited from caller
+					Self:   caller,
+				},
+				Raw: &rawAddresses,
 			},
 			wantReadOnly:      false,
 			wantTransferValue: uint256.NewInt(0),
@@ -269,9 +288,9 @@ func TestNewStatefulPrecompile(t *testing.T) {
 				return evm.StaticCall(callerContract, precompile, input, gasLimit)
 			},
 			wantAddresses: &libevm.AddressContext{
-				Origin: eoa,
-				Caller: caller,
-				Self:   precompile,
+				Origin:      eoa,
+				EVMSemantic: rawAddresses,
+				Raw:         &rawAddresses,
 			},
 			wantReadOnly:      true,
 			wantTransferValue: uint256.NewInt(0),
@@ -527,7 +546,7 @@ func TestCanCreateContract(t *testing.T) {
 	gasUsage := rng.Uint64n(gasLimit)
 
 	makeErr := func(cc *libevm.AddressContext, stateVal common.Hash) error {
-		return fmt.Errorf("Origin: %v Caller: %v Contract: %v State: %v", cc.Origin, cc.Caller, cc.Self, stateVal)
+		return fmt.Errorf("Origin: %v Caller: %v Contract: %v State: %v", cc.Origin, cc.EVMSemantic.Caller, cc.EVMSemantic.Self, stateVal)
 	}
 	hooks := &hookstest.Stub{
 		CanCreateContractFn: func(cc *libevm.AddressContext, gas uint64, s libevm.StateReader) (uint64, error) {
@@ -555,14 +574,34 @@ func TestCanCreateContract(t *testing.T) {
 			create: func(evm *vm.EVM) ([]byte, common.Address, uint64, error) {
 				return evm.Create(vm.AccountRef(caller), code, gasLimit, uint256.NewInt(0))
 			},
-			wantErr: makeErr(&libevm.AddressContext{Origin: origin, Caller: caller, Self: create}, value),
+			wantErr: makeErr(
+				&libevm.AddressContext{
+					Origin: origin,
+					EVMSemantic: libevm.CallerAndSelf{
+						Caller: caller,
+						Self:   create,
+					},
+					// `Raw` is documented as always being nil.
+				},
+				value,
+			),
 		},
 		{
 			name: "Create2",
 			create: func(evm *vm.EVM) ([]byte, common.Address, uint64, error) {
 				return evm.Create2(vm.AccountRef(caller), code, gasLimit, uint256.NewInt(0), new(uint256.Int).SetBytes(salt[:]))
 			},
-			wantErr: makeErr(&libevm.AddressContext{Origin: origin, Caller: caller, Self: create2}, value),
+			wantErr: makeErr(
+				&libevm.AddressContext{
+					Origin: origin,
+					EVMSemantic: libevm.CallerAndSelf{
+						Caller: caller,
+						Self:   create2,
+					},
+					// As above re `Raw` always being nil.
+				},
+				value,
+			),
 		},
 	}
 
@@ -630,7 +669,10 @@ func TestPrecompileMakeCall(t *testing.T) {
 				if bytes.Equal(input, unsafeCallerProxyOptSentinel) {
 					opts = append(opts, vm.WithUNSAFECallerAddressProxying())
 				}
-				// We are ultimately testing env.Call(), hence why this is the SUT.
+				// We are ultimately testing env.Call(), hence why this is the
+				// SUT. If this is ever extended to include DELEGATECALL or
+				// CALLCODE then the expected [libevm.AddressContext.Raw] values
+				// of the tests cases also need to change.
 				return env.Call(dest, precompileCallData, env.Gas(), uint256.NewInt(0), opts...)
 			}),
 			dest: vm.NewStatefulPrecompile(func(env vm.PrecompileEnvironment, input []byte) (ret []byte, err error) {
@@ -663,8 +705,10 @@ func TestPrecompileMakeCall(t *testing.T) {
 			want: statefulPrecompileOutput{
 				Addresses: &libevm.AddressContext{
 					Origin: eoa,
-					Caller: sut,
-					Self:   dest,
+					EVMSemantic: libevm.CallerAndSelf{
+						Caller: sut,
+						Self:   dest,
+					},
 				},
 				Input: precompileCallData,
 			},
@@ -675,8 +719,10 @@ func TestPrecompileMakeCall(t *testing.T) {
 			want: statefulPrecompileOutput{
 				Addresses: &libevm.AddressContext{
 					Origin: eoa,
-					Caller: caller, // overridden by CallOption
-					Self:   dest,
+					EVMSemantic: libevm.CallerAndSelf{
+						Caller: caller, // overridden by CallOption
+						Self:   dest,
+					},
 				},
 				Input: precompileCallData,
 			},
@@ -686,8 +732,10 @@ func TestPrecompileMakeCall(t *testing.T) {
 			want: statefulPrecompileOutput{
 				Addresses: &libevm.AddressContext{
 					Origin: eoa,
-					Caller: caller, // SUT runs as its own caller because of CALLCODE
-					Self:   dest,
+					EVMSemantic: libevm.CallerAndSelf{
+						Caller: caller, // SUT runs as its own caller because of CALLCODE
+						Self:   dest,
+					},
 				},
 				Input: precompileCallData,
 			},
@@ -698,8 +746,10 @@ func TestPrecompileMakeCall(t *testing.T) {
 			want: statefulPrecompileOutput{
 				Addresses: &libevm.AddressContext{
 					Origin: eoa,
-					Caller: caller, // CallOption is a NOOP
-					Self:   dest,
+					EVMSemantic: libevm.CallerAndSelf{
+						Caller: caller, // CallOption is a NOOP
+						Self:   dest,
+					},
 				},
 				Input: precompileCallData,
 			},
@@ -709,8 +759,10 @@ func TestPrecompileMakeCall(t *testing.T) {
 			want: statefulPrecompileOutput{
 				Addresses: &libevm.AddressContext{
 					Origin: eoa,
-					Caller: caller, // as with CALLCODE
-					Self:   dest,
+					EVMSemantic: libevm.CallerAndSelf{
+						Caller: caller, // as with CALLCODE
+						Self:   dest,
+					},
 				},
 				Input: precompileCallData,
 			},
@@ -721,8 +773,10 @@ func TestPrecompileMakeCall(t *testing.T) {
 			want: statefulPrecompileOutput{
 				Addresses: &libevm.AddressContext{
 					Origin: eoa,
-					Caller: caller, // CallOption is a NOOP
-					Self:   dest,
+					EVMSemantic: libevm.CallerAndSelf{
+						Caller: caller, // CallOption is a NOOP
+						Self:   dest,
+					},
 				},
 				Input: precompileCallData,
 			},
@@ -732,8 +786,10 @@ func TestPrecompileMakeCall(t *testing.T) {
 			want: statefulPrecompileOutput{
 				Addresses: &libevm.AddressContext{
 					Origin: eoa,
-					Caller: sut,
-					Self:   dest,
+					EVMSemantic: libevm.CallerAndSelf{
+						Caller: sut,
+						Self:   dest,
+					},
 				},
 				Input: precompileCallData,
 				// This demonstrates that even though the precompile makes a
@@ -749,8 +805,10 @@ func TestPrecompileMakeCall(t *testing.T) {
 			want: statefulPrecompileOutput{
 				Addresses: &libevm.AddressContext{
 					Origin: eoa,
-					Caller: caller, // overridden by CallOption
-					Self:   dest,
+					EVMSemantic: libevm.CallerAndSelf{
+						Caller: caller, // overridden by CallOption
+						Self:   dest,
+					},
 				},
 				Input:    precompileCallData,
 				ReadOnly: true,
@@ -760,6 +818,9 @@ func TestPrecompileMakeCall(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(tt.incomingCallType.String(), func(t *testing.T) {
+			// From the perspective of `dest` after a CALL from `sut`.
+			tt.want.Addresses.Raw = &tt.want.Addresses.EVMSemantic
+
 			t.Logf("calldata = %q", tt.eoaTxCallData)
 			state, evm := ethtest.NewZeroEVM(t)
 			evm.Origin = eoa
@@ -816,26 +877,3 @@ func TestPrecompileCallWithTracer(t *testing.T) {
 	require.NoErrorf(t, json.Unmarshal(gotJSON, &got), "json.Unmarshal(%T.GetResult(), %T)", tracer, &got)
 	require.Equal(t, value, got[contract].Storage[zeroHash], "value loaded with SLOAD")
 }
-
-//nolint:testableexamples // Including output would only make the example more complicated and hide the true intent
-func ExamplePrecompileEnvironment() {
-	// To determine the actual caller of a precompile, as against the effective
-	// caller (under EVM rules, as exposed by `Addresses().Caller`):
-	actualCaller := func(env vm.PrecompileEnvironment) common.Address {
-		if env.IncomingCallType() == vm.DelegateCall {
-			// DelegateCall acts as if it were its own caller.
-			return env.Addresses().Self
-		}
-		// CallCode could return either `Self` or `Caller` as it acts as its
-		// caller but doesn't inherit the caller's caller as DelegateCall does.
-		// Having it handled here is arbitrary from a behavioural perspective
-		// and is done only to simplify the code.
-		//
-		// Call and StaticCall don't affect self/caller semantics in any way.
-		return env.Addresses().Caller
-	}
-
-	// actualCaller would typically be a top-level function. It's only a
-	// variable to include it in this example function.
-	_ = actualCaller
-}

core/vm/environment.libevm.go

@@ -36,6 +36,8 @@ type environment struct {
 	evm      *EVM
 	self     *Contract
 	callType CallType
+
+	rawSelf, rawCaller common.Address
 }
 
 func (e *environment) Gas() uint64            { return e.self.Gas }
@@ -79,8 +81,14 @@ func (e *environment) ReadOnly() bool {
 func (e *environment) Addresses() *libevm.AddressContext {
 	return &libevm.AddressContext{
 		Origin: e.evm.Origin,
-		Caller: e.self.CallerAddress,
-		Self:   e.self.Address(),
+		EVMSemantic: libevm.CallerAndSelf{
+			Caller: e.self.CallerAddress,
+			Self:   e.self.Address(),
+		},
+		Raw: &libevm.CallerAndSelf{
+			Caller: e.rawCaller,
+			Self:   e.rawSelf,
+		},
 	}
 }
 

core/vm/evm.libevm.go

@@ -25,7 +25,15 @@ import (
 // canCreateContract is a convenience wrapper for calling the
 // [params.RulesHooks.CanCreateContract] hook.
 func (evm *EVM) canCreateContract(caller ContractRef, contractToCreate common.Address, gas uint64) (remainingGas uint64, _ error) {
-	addrs := &libevm.AddressContext{Origin: evm.Origin, Caller: caller.Address(), Self: contractToCreate}
+	addrs := &libevm.AddressContext{
+		Origin: evm.Origin,
+		EVMSemantic: libevm.CallerAndSelf{
+			Caller: caller.Address(),
+			Self:   contractToCreate,
+		},
+		// The "raw" caller isn't guaranteed to be known if the caller is a
+		// delegate so the `Raw` field is documented as always being nil.
+	}
 	gas, err := evm.chainRules.Hooks().CanCreateContract(addrs, gas, evm.StateDB)
 
 	// NOTE that this block only performs logging and that all paths propagate
@@ -34,8 +42,8 @@ func (evm *EVM) canCreateContract(caller ContractRef, contractToCreate common.Ad
 		log.Debug(
 			"Contract creation blocked by libevm hook",
 			"origin", addrs.Origin,
-			"caller", addrs.Caller,
-			"contract", addrs.Self,
+			"caller", addrs.EVMSemantic.Caller,
+			"contract", addrs.EVMSemantic.Self,
 			"hooks", log.TypeOf(evm.chainRules.Hooks()),
 			"reason", err,
 		)

libevm/libevm.go

@@ -61,10 +61,30 @@ type StateReader interface {
 // AddressContext carries addresses available to contexts such as calls and
 // contract creation.
 //
-// With respect to contract creation, the Self address MAY be the predicted
-// address of the contract about to be deployed, which may not exist yet.
+// With respect to contract creation, the EVMSemantic.Self address MAY be the
+// predicted address of the contract about to be deployed, which might not exist
+// yet.
 type AddressContext struct {
 	Origin common.Address // equivalent to vm.ORIGIN op code
-	Caller common.Address // equivalent to vm.CALLER op code
-	Self   common.Address // equivalent to vm.ADDRESS op code
+	// EVMSemantic addresses are those defined by the rules of the EVM, based on
+	// the type of call made to a contract; i.e. the addresses pushed to the
+	// stack by the vm.CALLER and vm.SELF op codes, respectively.
+	EVMSemantic CallerAndSelf
+	// Raw addresses are those that would be available to a contract under a
+	// standard CALL; i.e. not interpreted according EVM rules. They are the
+	// "intuitive" addresses such that the `Caller` is the account that called
+	// `Self` even if it did so via DELEGATECALL or CALLCODE (in which cases
+	// `Raw` and `EVMSemantic` would differ).
+	//
+	// Raw MUST NOT be nil when returned to a precompile implementation but MAY
+	// be nil in other situations (e.g. hooks), which MUST document behaviour on
+	// a case-by-case basis.
+	Raw *CallerAndSelf
+}
+
+// CallerAndSelf carries said addresses for use in an [AddressContext], where
+// the definitions of `Caller` and `Self` are defined based on context.
+type CallerAndSelf struct {
+	Caller common.Address
+	Self   common.Address
 }