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core/vm: modexp fix for 7823 #32363

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Merged
merged 2 commits into from
Aug 15, 2025
Merged

core/vm: modexp fix for 7823 #32363

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ae8d4d4
core/vm: fix 7823 in case of base length == 0 and mod length == 0. A…
jwasinger Aug 7, 2025
c8d18bf
core/vm: remove shift
fjl Aug 15, 2025
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19 changes: 12 additions & 7 deletions core/vm/contracts.go
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Original file line number Diff line number Diff line change
Expand Up @@ -500,23 +500,28 @@ func (c *bigModExp) RequiredGas(input []byte) uint64 {

func (c *bigModExp) Run(input []byte) ([]byte, error) {
var (
baseLen = new(big.Int).SetBytes(getData(input, 0, 32)).Uint64()
expLen = new(big.Int).SetBytes(getData(input, 32, 32)).Uint64()
modLen = new(big.Int).SetBytes(getData(input, 64, 32)).Uint64()
baseLenBig = new(big.Int).SetBytes(getData(input, 0, 32))
expLenBig = new(big.Int).SetBytes(getData(input, 32, 32))
modLenBig = new(big.Int).SetBytes(getData(input, 64, 32))
baseLen = baseLenBig.Uint64()
expLen = expLenBig.Uint64()
modLen = modLenBig.Uint64()
inputLenOverflow = max(baseLenBig.BitLen(), expLenBig.BitLen(), modLenBig.BitLen()) > 64
)
if len(input) > 96 {
input = input[96:]
} else {
input = input[:0]
}

// enforce size cap for inputs
if c.eip7823 && (inputLenOverflow || max(baseLen, expLen, modLen) > 1024) {
return nil, errors.New("one or more of base/exponent/modulus length exceeded 1024 bytes")
}
// Handle a special case when both the base and mod length is zero
if baseLen == 0 && modLen == 0 {
return []byte{}, nil
}
// enforce size cap for inputs
if c.eip7823 && max(baseLen, expLen, modLen) > 1024 {
return nil, errors.New("one or more of base/exponent/modulus length exceeded 1024 bytes")
}
// Retrieve the operands and execute the exponentiation
var (
base = new(big.Int).SetBytes(getData(input, 0, baseLen))
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