eth, les, geth: implement cli-configurable global gas cap for RPC calls (#19401)

* eth, les, geth: implement cli-configurable global gas cap for RPC calls

* graphql, ethapi: place gas cap in DoCall

* ethapi: reformat log message

2 files changed, 15 insertions, 6 deletions

diff --git a/internal/ethapi/api.go b/internal/ethapi/api.go
index e5a8124b1..ccd918be2 100644
--- a/internal/ethapi/api.go
+++ b/internal/ethapi/api.go
@@ -674,7 +674,7 @@ type CallArgs struct {
 	Data     *hexutil.Bytes  `json:"data"`
 }
 
-func DoCall(ctx context.Context, b Backend, args CallArgs, blockNr rpc.BlockNumber, vmCfg vm.Config, timeout time.Duration) ([]byte, uint64, bool, error) {
+func DoCall(ctx context.Context, b Backend, args CallArgs, blockNr rpc.BlockNumber, vmCfg vm.Config, timeout time.Duration, globalGasCap *big.Int) ([]byte, uint64, bool, error) {
 	defer func(start time.Time) { log.Debug("Executing EVM call finished", "runtime", time.Since(start)) }(time.Now())
 
 	state, header, err := b.StateAndHeaderByNumber(ctx, blockNr)
@@ -697,6 +697,10 @@ func DoCall(ctx context.Context, b Backend, args CallArgs, blockNr rpc.BlockNumb
 	if args.Gas != nil {
 		gas = uint64(*args.Gas)
 	}
+	if globalGasCap != nil && globalGasCap.Uint64() < gas {
+		log.Warn("Caller gas above allowance, capping", "requested", gas, "cap", globalGasCap)
+		gas = globalGasCap.Uint64()
+	}
 	gasPrice := new(big.Int).SetUint64(defaultGasPrice)
 	if args.GasPrice != nil {
 		gasPrice = args.GasPrice.ToInt()
@@ -752,11 +756,11 @@ func DoCall(ctx context.Context, b Backend, args CallArgs, blockNr rpc.BlockNumb
 // Call executes the given transaction on the state for the given block number.
 // It doesn't make and changes in the state/blockchain and is useful to execute and retrieve values.
 func (s *PublicBlockChainAPI) Call(ctx context.Context, args CallArgs, blockNr rpc.BlockNumber) (hexutil.Bytes, error) {
-	result, _, _, err := DoCall(ctx, s.b, args, blockNr, vm.Config{}, 5*time.Second)
+	result, _, _, err := DoCall(ctx, s.b, args, blockNr, vm.Config{}, 5*time.Second, s.b.RPCGasCap())
 	return (hexutil.Bytes)(result), err
 }
 
-func DoEstimateGas(ctx context.Context, b Backend, args CallArgs, blockNr rpc.BlockNumber) (hexutil.Uint64, error) {
+func DoEstimateGas(ctx context.Context, b Backend, args CallArgs, blockNr rpc.BlockNumber, gasCap *big.Int) (hexutil.Uint64, error) {
 	// Binary search the gas requirement, as it may be higher than the amount used
 	var (
 		lo  uint64 = params.TxGas - 1
@@ -773,13 +777,17 @@ func DoEstimateGas(ctx context.Context, b Backend, args CallArgs, blockNr rpc.Bl
 		}
 		hi = block.GasLimit()
 	}
+	if gasCap != nil && hi > gasCap.Uint64() {
+		log.Warn("Caller gas above allowance, capping", "requested", hi, "cap", gasCap)
+		hi = gasCap.Uint64()
+	}
 	cap = hi
 
 	// Create a helper to check if a gas allowance results in an executable transaction
 	executable := func(gas uint64) bool {
 		args.Gas = (*hexutil.Uint64)(&gas)
 
-		_, _, failed, err := DoCall(ctx, b, args, rpc.PendingBlockNumber, vm.Config{}, 0)
+		_, _, failed, err := DoCall(ctx, b, args, rpc.PendingBlockNumber, vm.Config{}, 0, gasCap)
 		if err != nil || failed {
 			return false
 		}
@@ -797,7 +805,7 @@ func DoEstimateGas(ctx context.Context, b Backend, args CallArgs, blockNr rpc.Bl
 	// Reject the transaction as invalid if it still fails at the highest allowance
 	if hi == cap {
 		if !executable(hi) {
-			return 0, fmt.Errorf("gas required exceeds allowance or always failing transaction")
+			return 0, fmt.Errorf("gas required exceeds allowance (%d) or always failing transaction", cap)
 		}
 	}
 	return hexutil.Uint64(hi), nil
@@ -806,7 +814,7 @@ func DoEstimateGas(ctx context.Context, b Backend, args CallArgs, blockNr rpc.Bl
 // EstimateGas returns an estimate of the amount of gas needed to execute the
 // given transaction against the current pending block.
 func (s *PublicBlockChainAPI) EstimateGas(ctx context.Context, args CallArgs) (hexutil.Uint64, error) {
-	return DoEstimateGas(ctx, s.b, args, rpc.PendingBlockNumber)
+	return DoEstimateGas(ctx, s.b, args, rpc.PendingBlockNumber, s.b.RPCGasCap())
 }
 
 // ExecutionResult groups all structured logs emitted by the EVM
diff --git a/internal/ethapi/backend.go b/internal/ethapi/backend.go
index e88207f87..0c6c7eace 100644
--- a/internal/ethapi/backend.go
+++ b/internal/ethapi/backend.go
@@ -45,6 +45,7 @@ type Backend interface {
 	EventMux() *event.TypeMux
 	AccountManager() *accounts.Manager
 	ExtRPCEnabled() bool
+	RPCGasCap() *big.Int // global gas cap for eth_call over rpc: DoS protection
 
 	// BlockChain API
 	SetHead(number uint64)