Stricter input legth checking in precompiles getValidator/fractionMulExps/transfer (#2038)

* fractionMulExp: stricter input length check

See #615

* transfer: stricter input length checking

See #615

* getValidator: stricter input length checking

See #615

* Only change precompile checks after GFork

Author: karlb

core/vm/contracts.go

@@ -698,7 +698,7 @@ func (c *transfer) Run(input []byte, caller common.Address, evm *EVM) ([]byte, e
 	//   to:    32 bytes representing the address of the recipient
 	//   value: 32 bytes, a 256 bit integer representing the amount of Celo Gold to transfer
 	// 3 arguments x 32 bytes each = 96 bytes total input
-	if len(input) < 96 {
+	if (evm.chainRules.IsGFork && len(input) != 96) || len(input) <= 96 {
 		return nil, ErrInputLength
 	}
 
@@ -781,7 +781,7 @@ func (c *fractionMulExp) Run(input []byte, caller common.Address, evm *EVM) ([]b
 	//   decimals:     32 bytes, 256 bit integer, places of precision
 	//
 	// 6 args x 32 bytes each = 192 bytes total input length
-	if len(input) < 192 {
+	if (evm.chainRules.IsGFork && len(input) != 192) || len(input) < 192 {
 		return nil, ErrInputLength
 	}
 
@@ -1015,7 +1015,7 @@ func (c *getValidator) Run(input []byte, caller common.Address, evm *EVM) ([]byt
 	// input is comprised of two arguments:
 	//   index: 32 byte integer representing the index of the validator to get
 	//   blockNumber: 32 byte integer representing the block number to access
-	if len(input) < 64 {
+	if (evm.chainRules.IsGFork && len(input) != 64) || len(input) < 64 {
 		return nil, ErrInputLength
 	}
 

core/vm/contracts_test.go

@@ -499,7 +499,14 @@ func BenchmarkPrecompiledEd25519Verify(b *testing.B) { benchJSON("ed25519Verify"
 
 // Tests sample inputs for fractionMulExp
 // NOTE: This currently only verifies that inputs of invalid length are rejected
-func TestPrecompiledFractionMulExp(t *testing.T) { testJSON("fractionMulExp", "fc", t) }
+func TestPrecompiledFractionMulExp(t *testing.T) {
+	// Post GFork behaviour
+	mockEVM.chainRules.IsGFork = true
+	testJSON("fractionMulExp", "fc", t)
+	// Pre GFork behaviour
+	mockEVM.chainRules.IsGFork = false
+	testJSON("fractionMulExpOld", "fc", t)
+}
 
 // Tests sample inputs for proofOfPossession
 // NOTE: This currently only verifies that inputs of invalid length are rejected

core/vm/testdata/precompiles/fractionMulExp.json

@@ -6,13 +6,14 @@
 	},
 	{
 		"Input": "0000000000000000000000000000000000000000000000000000000000000001000000000000000000000000000000000000000000000000000000000000001200000000000000000000000000000000000000000000000000000000000000150000000000000000000000000000000000000000000000000000000000000f100000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000000400000000",
-		"Expected": "00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000002710",
-		"Name": "input_too_long"
+		"Expected": "invalid input length",
+		"Name": "input_too_long",
+		"ErrorExpected": true
 	},
 	{
 		"Input":         "",
 		"Expected":      "invalid input length",
 		"Name":          "empty_input",
 		"ErrorExpected": true
 	}
-]
+]

core/vm/testdata/precompiles/fractionMulExpOld.json

@@ -0,0 +1,7 @@
+[
+	{
+		"Input": "0000000000000000000000000000000000000000000000000000000000000001000000000000000000000000000000000000000000000000000000000000001200000000000000000000000000000000000000000000000000000000000000150000000000000000000000000000000000000000000000000000000000000f100000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000000400000000",
+		"Expected": "00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000002710",
+		"Name": "input_too_long"
+	}
+]