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https://github.com/ethereum/go-ethereum.git
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common/math, tests/fuzzers: use big.Int clone (#26006)
This commit is contained in:
Daniel Liu
parent
c87b7c3135
commit
abebda601c
6 changed files with 107 additions and 90 deletions
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@ -1,82 +0,0 @@
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// Copyright 2020 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package math
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import (
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"math/big"
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"math/bits"
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"github.com/XinFinOrg/XDPoSChain/common"
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)
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// FastExp is semantically equivalent to x.Exp(x,y, m), but is faster for even
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// modulus.
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func FastExp(x, y, m *big.Int) *big.Int {
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// Split m = m1 × m2 where m1 = 2ⁿ
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n := m.TrailingZeroBits()
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m1 := new(big.Int).Lsh(common.Big1, n)
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mask := new(big.Int).Sub(m1, common.Big1)
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m2 := new(big.Int).Rsh(m, n)
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// We want z = x**y mod m.
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// z1 = x**y mod m1 = (x**y mod m) mod m1 = z mod m1
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// z2 = x**y mod m2 = (x**y mod m) mod m2 = z mod m2
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z1 := fastExpPow2(x, y, mask)
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z2 := new(big.Int).Exp(x, y, m2)
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// Reconstruct z from z1, z2 using CRT, using algorithm from paper,
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// which uses only a single modInverse.
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// p = (z1 - z2) * m2⁻¹ (mod m1)
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// z = z2 + p * m2
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z := new(big.Int).Set(z2)
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// Compute (z1 - z2) mod m1 [m1 == 2**n] into z1.
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z1 = z1.And(z1, mask)
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z2 = z2.And(z2, mask)
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z1 = z1.Sub(z1, z2)
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if z1.Sign() < 0 {
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z1 = z1.Add(z1, m1)
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}
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// Reuse z2 for p = z1 * m2inv.
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m2inv := new(big.Int).ModInverse(m2, m1)
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z2 = z2.Mul(z1, m2inv)
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z2 = z2.And(z2, mask)
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// Reuse z1 for m2 * p.
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z = z.Add(z, z1.Mul(z2, m2))
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z = z.Rem(z, m)
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return z
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}
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func fastExpPow2(x, y *big.Int, mask *big.Int) *big.Int {
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z := big.NewInt(1)
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if y.Sign() == 0 {
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return z
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}
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p := new(big.Int).Set(x)
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p = p.And(p, mask)
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if p.Cmp(z) <= 0 { // p <= 1
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return p
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}
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if y.Cmp(mask) > 0 {
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y = new(big.Int).And(y, mask)
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}
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t := new(big.Int)
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for _, b := range y.Bits() {
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for i := 0; i < bits.UintSize; i++ {
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if b&1 != 0 {
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z, t = t.Mul(z, p), z
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z = z.And(z, mask)
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}
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p, t = t.Mul(p, p), p
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p = p.And(p, mask)
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b >>= 1
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}
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}
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return z
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}
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53
common/math/modexp_test.go
Normal file
53
common/math/modexp_test.go
Normal file
File diff suppressed because one or more lines are too long
1
go.mod
1
go.mod
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@ -61,6 +61,7 @@ require (
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github.com/google/go-cmp v0.6.0 // indirect
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github.com/google/pprof v0.0.0-20230207041349-798e818bf904 // indirect
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github.com/google/uuid v1.3.0 // indirect
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github.com/holiman/big v0.0.0-20221017200358-a027dc42d04e // indirect
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github.com/kr/pretty v0.3.1 // indirect
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github.com/kr/text v0.2.0 // indirect
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github.com/maruel/panicparse v0.0.0-20160720141634-ad661195ed0e // indirect
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2
go.sum
2
go.sum
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@ -141,6 +141,8 @@ github.com/graph-gophers/graphql-go v0.0.0-20191115155744-f33e81362277/go.mod h1
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github.com/hashicorp/golang-lru v0.0.0-20160813221303-0a025b7e63ad/go.mod h1:/m3WP610KZHVQ1SGc6re/UDhFvYD7pJ4Ao+sR/qLZy8=
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github.com/hashicorp/golang-lru v0.5.3 h1:YPkqC67at8FYaadspW/6uE0COsBxS2656RLEr8Bppgk=
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github.com/hashicorp/golang-lru v0.5.3/go.mod h1:iADmTwqILo4mZ8BN3D2Q6+9jd8WM5uGBxy+E8yxSoD4=
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github.com/holiman/big v0.0.0-20221017200358-a027dc42d04e h1:pIYdhNkDh+YENVNi3gto8n9hAmRxKxoar0iE6BLucjw=
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github.com/holiman/big v0.0.0-20221017200358-a027dc42d04e/go.mod h1:j9cQbcqHQujT0oKJ38PylVfqohClLr3CvDC+Qcg+lhU=
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github.com/holiman/uint256 v1.2.3 h1:K8UWO1HUJpRMXBxbmaY1Y8IAMZC/RsKB+ArEnnK4l5o=
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github.com/holiman/uint256 v1.2.3/go.mod h1:SC8Ryt4n+UBbPbIBKaG9zbbDlp4jOru9xFZmPzLUTxw=
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github.com/holiman/uint256 v1.2.4 h1:jUc4Nk8fm9jZabQuqr2JzednajVmBpC+oiTiXZJEApU=
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40
tests/fuzzers/modexp/debug/main.go
Normal file
40
tests/fuzzers/modexp/debug/main.go
Normal file
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@ -0,0 +1,40 @@
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// Copyright 2020 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package main
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import (
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"fmt"
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"os"
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"github.com/XinFinOrg/XDPoSChain/tests/fuzzers/modexp"
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)
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func main() {
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if len(os.Args) != 2 {
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fmt.Fprintf(os.Stderr, "Usage: debug <file>\n")
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fmt.Fprintf(os.Stderr, "Example\n")
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fmt.Fprintf(os.Stderr, " $ debug ../crashers/4bbef6857c733a87ecf6fd8b9e7238f65eb9862a\n")
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os.Exit(1)
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}
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crasher := os.Args[1]
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data, err := os.ReadFile(crasher)
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if err != nil {
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fmt.Fprintf(os.Stderr, "error loading crasher %v: %v", crasher, err)
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os.Exit(1)
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}
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modexp.Fuzz(data)
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}
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@ -21,8 +21,8 @@ import (
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"math/big"
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"github.com/XinFinOrg/XDPoSChain/common"
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"github.com/XinFinOrg/XDPoSChain/common/math"
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"github.com/XinFinOrg/XDPoSChain/core/vm"
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big2 "github.com/holiman/big"
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)
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// The function must return
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@ -55,18 +55,21 @@ func Fuzz(input []byte) int {
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input = input[96:]
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// Retrieve the operands and execute the exponentiation
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var (
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base = new(big.Int).SetBytes(getData(input, 0, baseLen))
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exp = new(big.Int).SetBytes(getData(input, baseLen, expLen))
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mod = new(big.Int).SetBytes(getData(input, baseLen+expLen, modLen))
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base = new(big.Int).SetBytes(getData(input, 0, baseLen))
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exp = new(big.Int).SetBytes(getData(input, baseLen, expLen))
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mod = new(big.Int).SetBytes(getData(input, baseLen+expLen, modLen))
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base2 = new(big2.Int).SetBytes(getData(input, 0, baseLen))
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exp2 = new(big2.Int).SetBytes(getData(input, baseLen, expLen))
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mod2 = new(big2.Int).SetBytes(getData(input, baseLen+expLen, modLen))
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)
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if mod.BitLen() == 0 {
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// Modulo 0 is undefined, return zero
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return -1
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}
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var a = math.FastExp(new(big.Int).Set(base), new(big.Int).Set(exp), new(big.Int).Set(mod))
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var b = base.Exp(base, exp, mod)
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if a.Cmp(b) != 0 {
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panic(fmt.Sprintf("Inequality %x != %x", a, b))
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var a = new(big2.Int).Exp(base2, exp2, mod2).String()
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var b = new(big.Int).Exp(base, exp, mod).String()
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if a != b {
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panic(fmt.Sprintf("Inequality %#x ^ %#x mod %#x \n have %s\n want %s", base, exp, mod, a, b))
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}
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return 1
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}
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