diff --git a/core/vm/contracts.go b/core/vm/contracts.go index 9210f5486c57..1314c2438658 100644 --- a/core/vm/contracts.go +++ b/core/vm/contracts.go @@ -29,8 +29,7 @@ import ( "github.com/ethereum/go-ethereum/crypto/bls12381" "github.com/ethereum/go-ethereum/crypto/bn256" "github.com/ethereum/go-ethereum/params" - - //lint:ignore SA1019 Needed for precompile + big2 "github.com/holiman/big" "golang.org/x/crypto/ripemd160" ) @@ -266,9 +265,10 @@ var ( // modexpMultComplexity implements bigModexp multComplexity formula, as defined in EIP-198 // // def mult_complexity(x): -// if x <= 64: return x ** 2 -// elif x <= 1024: return x ** 2 // 4 + 96 * x - 3072 -// else: return x ** 2 // 16 + 480 * x - 199680 +// +// if x <= 64: return x ** 2 +// elif x <= 1024: return x ** 2 // 4 + 96 * x - 3072 +// else: return x ** 2 // 16 + 480 * x - 199680 // // where is x is max(length_of_MODULUS, length_of_BASE) func modexpMultComplexity(x *big.Int) *big.Int { @@ -379,15 +379,22 @@ func (c *bigModExp) Run(input []byte) ([]byte, error) { } // Retrieve the operands and execute the exponentiation var ( - base = new(big.Int).SetBytes(getData(input, 0, baseLen)) - exp = new(big.Int).SetBytes(getData(input, baseLen, expLen)) - mod = new(big.Int).SetBytes(getData(input, baseLen+expLen, modLen)) + base = new(big2.Int).SetBytes(getData(input, 0, baseLen)) + exp = new(big2.Int).SetBytes(getData(input, baseLen, expLen)) + mod = new(big2.Int).SetBytes(getData(input, baseLen+expLen, modLen)) + v []byte ) - if mod.BitLen() == 0 { + switch { + case mod.BitLen() == 0: // Modulo 0 is undefined, return zero return common.LeftPadBytes([]byte{}, int(modLen)), nil + case base.BitLen() == 1: // a bit length of 1 means it's 1 (or -1). + //If base == 1, then we can just return base % mod (if mod >= 1, which it is) + v = base.Mod(base, mod).Bytes() + default: + v = base.Exp(base, exp, mod).Bytes() } - return common.LeftPadBytes(base.Exp(base, exp, mod).Bytes(), int(modLen)), nil + return common.LeftPadBytes(v, int(modLen)), nil } // newCurvePoint unmarshals a binary blob into a bn256 elliptic curve point,