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75 lines
2 KiB
Go
75 lines
2 KiB
Go
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//go:build gofuzz
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// +build gofuzz
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// How to run the fuzzer:
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// $ go get -u github.com/dvyukov/go-fuzz/go-fuzz
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// $ go get -u github.com/dvyukov/go-fuzz/go-fuzz-build
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// $ go-fuzz-build -libfuzzer -func FuzzReduction -o lib.a
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// $ clang -fsanitize=fuzzer lib.a -o fu.exe
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// $ ./fu.exe
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package fp448
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import (
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"encoding/binary"
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"fmt"
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"math/big"
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"github.com/cloudflare/circl/internal/conv"
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)
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// FuzzReduction is a fuzzer target for red64 function, which reduces t
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// (112 bits) to a number t' (56 bits) congruent modulo p448.
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func FuzzReduction(data []byte) int {
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if len(data) != 2*Size {
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return -1
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}
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var got, want Elt
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var lo, hi [7]uint64
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a := data[:Size]
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b := data[Size:]
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lo[0] = binary.LittleEndian.Uint64(a[0*8 : 1*8])
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lo[1] = binary.LittleEndian.Uint64(a[1*8 : 2*8])
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lo[2] = binary.LittleEndian.Uint64(a[2*8 : 3*8])
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lo[3] = binary.LittleEndian.Uint64(a[3*8 : 4*8])
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lo[4] = binary.LittleEndian.Uint64(a[4*8 : 5*8])
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lo[5] = binary.LittleEndian.Uint64(a[5*8 : 6*8])
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lo[6] = binary.LittleEndian.Uint64(a[6*8 : 7*8])
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hi[0] = binary.LittleEndian.Uint64(b[0*8 : 1*8])
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hi[1] = binary.LittleEndian.Uint64(b[1*8 : 2*8])
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hi[2] = binary.LittleEndian.Uint64(b[2*8 : 3*8])
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hi[3] = binary.LittleEndian.Uint64(b[3*8 : 4*8])
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hi[4] = binary.LittleEndian.Uint64(b[4*8 : 5*8])
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hi[5] = binary.LittleEndian.Uint64(b[5*8 : 6*8])
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hi[6] = binary.LittleEndian.Uint64(b[6*8 : 7*8])
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red64(&got, &lo, &hi)
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t := conv.BytesLe2BigInt(data[:2*Size])
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two448 := big.NewInt(1)
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two448.Lsh(two448, 448) // 2^448
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mask448 := big.NewInt(1)
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mask448.Sub(two448, mask448) // 2^448-1
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two224plus1 := big.NewInt(1)
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two224plus1.Lsh(two224plus1, 224)
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two224plus1.Add(two224plus1, big.NewInt(1)) // 2^224+1
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var loBig, hiBig big.Int
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for t.Cmp(two448) >= 0 {
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loBig.And(t, mask448)
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hiBig.Rsh(t, 448)
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t.Mul(&hiBig, two224plus1)
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t.Add(t, &loBig)
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}
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conv.BigInt2BytesLe(want[:], t)
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if got != want {
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fmt.Printf("in: %v\n", conv.BytesLe2BigInt(data[:2*Size]))
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fmt.Printf("got: %v\n", got)
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fmt.Printf("want: %v\n", want)
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panic("error found")
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}
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return 1
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}
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