crypto, tests/fuzzers: add gnark bn254 precompile methods for fuzzing (#30585)
Makes the gnark precompile methods more amenable to fuzzing
This commit is contained in:
kevaundray
Martin HS
parent
d7434facba
commit
cba2e77fe2
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@ -0,0 +1,51 @@
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package bn256
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import (
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"math/big"
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"github.com/consensys/gnark-crypto/ecc/bn254"
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)
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// G1 is the affine representation of a G1 group element.
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//
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// Since this code is used for precompiles, using Jacobian
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// points are not beneficial because there are no intermediate
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// points to allow us to save on inversions.
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//
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// Note: We also use this struct so that we can conform to the existing API
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// that the precompiles want.
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type G1 struct {
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inner bn254.G1Affine
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}
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// Add adds `a` and `b` together, storing the result in `g`
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func (g *G1) Add(a, b *G1) {
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g.inner.Add(&a.inner, &b.inner)
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}
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// ScalarMult computes the scalar multiplication between `a` and
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// `scalar`, storing the result in `g`
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func (g *G1) ScalarMult(a *G1, scalar *big.Int) {
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g.inner.ScalarMultiplication(&a.inner, scalar)
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}
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// Unmarshal deserializes `buf` into `g`
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//
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// Note: whether the deserialization is of a compressed
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// or an uncompressed point, is encoded in the bytes.
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//
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// For our purpose, the point will always be serialized
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// as uncompressed, ie 64 bytes.
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//
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// This method also checks whether the point is on the
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// curve and in the prime order subgroup.
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func (g *G1) Unmarshal(buf []byte) (int, error) {
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return g.inner.SetBytes(buf)
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}
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// Marshal serializes the point into a byte slice.
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//
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// Note: The point is serialized as uncompressed.
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func (p *G1) Marshal() []byte {
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return p.inner.Marshal()
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}
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@ -0,0 +1,38 @@
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package bn256
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import (
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"github.com/consensys/gnark-crypto/ecc/bn254"
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)
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// G2 is the affine representation of a G2 group element.
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//
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// Since this code is used for precompiles, using Jacobian
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// points are not beneficial because there are no intermediate
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// points and G2 in particular is only used for the pairing input.
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//
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// Note: We also use this struct so that we can conform to the existing API
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// that the precompiles want.
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type G2 struct {
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inner bn254.G2Affine
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}
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// Unmarshal deserializes `buf` into `g`
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//
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// Note: whether the deserialization is of a compressed
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// or an uncompressed point, is encoded in the bytes.
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//
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// For our purpose, the point will always be serialized
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// as uncompressed, ie 128 bytes.
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//
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// This method also checks whether the point is on the
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// curve and in the prime order subgroup.
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func (g *G2) Unmarshal(buf []byte) (int, error) {
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return g.inner.SetBytes(buf)
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}
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// Marshal serializes the point into a byte slice.
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//
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// Note: The point is serialized as uncompressed.
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func (g *G2) Marshal() []byte {
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return g.inner.Marshal()
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}
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@ -0,0 +1,65 @@
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package bn256
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import (
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"fmt"
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"math/big"
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"github.com/consensys/gnark-crypto/ecc/bn254"
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)
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// GT is the affine representation of a GT field element.
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//
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// Note: GT is not explicitly used in mainline code.
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// It is needed for fuzzing.
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type GT struct {
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inner bn254.GT
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}
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// Pair compute the optimal Ate pairing between a G1 and
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// G2 element.
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//
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// Note: This method is not explicitly used in mainline code.
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// It is needed for fuzzing. It should also be noted,
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// that the output of this function may not match other
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func Pair(a_ *G1, b_ *G2) *GT {
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a := a_.inner
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b := b_.inner
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pairingOutput, err := bn254.Pair([]bn254.G1Affine{a}, []bn254.G2Affine{b})
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if err != nil {
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// Since this method is only called during fuzzing, it is okay to panic here.
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// We do not return an error to match the interface of the other bn256 libraries.
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panic(fmt.Sprintf("gnark/bn254 encountered error: %v", err))
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}
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return >{
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inner: pairingOutput,
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}
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}
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// Unmarshal deserializes `buf` into `g`
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//
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// Note: This method is not explicitly used in mainline code.
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// It is needed for fuzzing.
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func (g *GT) Unmarshal(buf []byte) error {
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return g.inner.SetBytes(buf)
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}
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// Marshal serializes the point into a byte slice.
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//
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// Note: This method is not explicitly used in mainline code.
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// It is needed for fuzzing.
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func (g *GT) Marshal() []byte {
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bytes := g.inner.Bytes()
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return bytes[:]
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}
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// Exp raises `base` to the power of `exponent`
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//
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// Note: This method is not explicitly used in mainline code.
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// It is needed for fuzzing.
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func (g *GT) Exp(base GT, exponent *big.Int) *GT {
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g.inner.Exp(base.inner, exponent)
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return g
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}
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@ -0,0 +1,73 @@
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package bn256
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import (
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"github.com/consensys/gnark-crypto/ecc/bn254"
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)
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// Computes the following relation: ∏ᵢ e(Pᵢ, Qᵢ) =? 1
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//
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// To explain why gnark returns a (bool, error):
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//
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// - If the function `e` does not return a result then internally
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// an error is returned.
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// - If `e` returns a result, then error will be nil,
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// but if this value is not `1` then the boolean value will be false
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//
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// We therefore check for an error, and return false if its non-nil and
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// then return the value of the boolean if not.
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func PairingCheck(a_ []*G1, b_ []*G2) bool {
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a := getInnerG1s(a_)
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b := getInnerG2s(b_)
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// Assume that len(a) == len(b)
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//
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// The pairing function will return
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// false, if this is not the case.
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size := len(a)
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// Check if input is empty -- gnark will
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// return false on an empty input, however
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// the ossified behavior is to return true
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// on an empty input, so we add this if statement.
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if size == 0 {
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return true
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}
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ok, err := bn254.PairingCheck(a, b)
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if err != nil {
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return false
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}
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return ok
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}
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// getInnerG1s gets the inner gnark G1 elements.
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//
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// These methods are used for two reasons:
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//
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// - We use a new type `G1`, so we need to convert from
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// []*G1 to []*bn254.G1Affine
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// - The gnark API accepts slices of values and not slices of
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// pointers to values, so we need to return []bn254.G1Affine
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// instead of []*bn254.G1Affine.
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func getInnerG1s(pointerSlice []*G1) []bn254.G1Affine {
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gnarkValues := make([]bn254.G1Affine, 0, len(pointerSlice))
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for _, ptr := range pointerSlice {
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if ptr != nil {
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gnarkValues = append(gnarkValues, ptr.inner)
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}
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}
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return gnarkValues
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}
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// getInnerG2s gets the inner gnark G2 elements.
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//
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// The rationale for this method is the same as `getInnerG1s`.
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func getInnerG2s(pointerSlice []*G2) []bn254.G2Affine {
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gnarkValues := make([]bn254.G2Affine, 0, len(pointerSlice))
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for _, ptr := range pointerSlice {
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if ptr != nil {
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gnarkValues = append(gnarkValues, ptr.inner)
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}
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}
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return gnarkValues
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}
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@ -22,12 +22,12 @@ import (
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"io"
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"math/big"
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"github.com/consensys/gnark-crypto/ecc/bn254"
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cloudflare "github.com/ethereum/go-ethereum/crypto/bn256/cloudflare"
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gnark "github.com/ethereum/go-ethereum/crypto/bn256/gnark"
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google "github.com/ethereum/go-ethereum/crypto/bn256/google"
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)
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func getG1Points(input io.Reader) (*cloudflare.G1, *google.G1, *bn254.G1Affine) {
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func getG1Points(input io.Reader) (*cloudflare.G1, *google.G1, *gnark.G1) {
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_, xc, err := cloudflare.RandomG1(input)
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if err != nil {
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// insufficient input
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@ -37,14 +37,14 @@ func getG1Points(input io.Reader) (*cloudflare.G1, *google.G1, *bn254.G1Affine)
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if _, err := xg.Unmarshal(xc.Marshal()); err != nil {
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panic(fmt.Sprintf("Could not marshal cloudflare -> google: %v", err))
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}
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xs := new(bn254.G1Affine)
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if err := xs.Unmarshal(xc.Marshal()); err != nil {
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xs := new(gnark.G1)
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if _, err := xs.Unmarshal(xc.Marshal()); err != nil {
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panic(fmt.Sprintf("Could not marshal cloudflare -> gnark: %v", err))
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}
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return xc, xg, xs
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}
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func getG2Points(input io.Reader) (*cloudflare.G2, *google.G2, *bn254.G2Affine) {
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func getG2Points(input io.Reader) (*cloudflare.G2, *google.G2, *gnark.G2) {
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_, xc, err := cloudflare.RandomG2(input)
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if err != nil {
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// insufficient input
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@ -54,14 +54,14 @@ func getG2Points(input io.Reader) (*cloudflare.G2, *google.G2, *bn254.G2Affine)
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if _, err := xg.Unmarshal(xc.Marshal()); err != nil {
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panic(fmt.Sprintf("Could not marshal cloudflare -> google: %v", err))
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}
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xs := new(bn254.G2Affine)
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if err := xs.Unmarshal(xc.Marshal()); err != nil {
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xs := new(gnark.G2)
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if _, err := xs.Unmarshal(xc.Marshal()); err != nil {
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panic(fmt.Sprintf("Could not marshal cloudflare -> gnark: %v", err))
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}
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return xc, xg, xs
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}
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// fuzzAdd fuzzez bn256 addition between the Google and Cloudflare libraries.
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// fuzzAdd fuzzes bn256 addition between the Google, Cloudflare and Gnark libraries.
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func fuzzAdd(data []byte) int {
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input := bytes.NewReader(data)
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xc, xg, xs := getG1Points(input)
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@ -72,7 +72,7 @@ func fuzzAdd(data []byte) int {
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if yc == nil {
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return 0
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}
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// Ensure both libs can parse the second curve point
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// Ensure libs can parse the second curve point
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// Add the two points and ensure they result in the same output
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rc := new(cloudflare.G1)
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rc.Add(xc, yc)
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@ -80,9 +80,8 @@ func fuzzAdd(data []byte) int {
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rg := new(google.G1)
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rg.Add(xg, yg)
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tmpX := new(bn254.G1Jac).FromAffine(xs)
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tmpY := new(bn254.G1Jac).FromAffine(ys)
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rs := new(bn254.G1Affine).FromJacobian(tmpX.AddAssign(tmpY))
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rs := new(gnark.G1)
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rs.Add(xs, ys)
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if !bytes.Equal(rc.Marshal(), rg.Marshal()) {
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panic("add mismatch: cloudflare/google")
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@ -94,8 +93,8 @@ func fuzzAdd(data []byte) int {
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return 1
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}
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// fuzzMul fuzzez bn256 scalar multiplication between the Google and Cloudflare
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// libraries.
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// fuzzMul fuzzes bn256 scalar multiplication between the Google, Cloudflare
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// and Gnark libraries.
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func fuzzMul(data []byte) int {
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input := bytes.NewReader(data)
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pc, pg, ps := getG1Points(input)
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@ -122,15 +121,13 @@ func fuzzMul(data []byte) int {
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rg := new(google.G1)
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rg.ScalarMult(pg, new(big.Int).SetBytes(buf))
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rs := new(bn254.G1Jac)
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psJac := new(bn254.G1Jac).FromAffine(ps)
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rs.ScalarMultiplication(psJac, new(big.Int).SetBytes(buf))
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rsAffine := new(bn254.G1Affine).FromJacobian(rs)
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rs := new(gnark.G1)
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rs.ScalarMult(ps, new(big.Int).SetBytes(buf))
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if !bytes.Equal(rc.Marshal(), rg.Marshal()) {
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panic("scalar mul mismatch: cloudflare/google")
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}
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if !bytes.Equal(rc.Marshal(), rsAffine.Marshal()) {
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if !bytes.Equal(rc.Marshal(), rs.Marshal()) {
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panic("scalar mul mismatch: cloudflare/gnark")
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}
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return 1
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@ -150,17 +147,26 @@ func fuzzPair(data []byte) int {
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// Pair the two points and ensure they result in the same output
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clPair := cloudflare.Pair(pc, tc).Marshal()
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gPair := google.Pair(pg, tg).Marshal()
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sPair := gnark.Pair(ps, ts).Marshal()
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if !bytes.Equal(clPair, gPair) {
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panic("pairing mismatch: cloudflare/google")
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}
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cPair, err := bn254.Pair([]bn254.G1Affine{*ps}, []bn254.G2Affine{*ts})
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if err != nil {
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panic(fmt.Sprintf("gnark/bn254 encountered error: %v", err))
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normalizedClPair := normalizeGTToGnark(clPair).Marshal()
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if !bytes.Equal(normalizedClPair, sPair) {
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panic("pairing mismatch: cloudflare/gnark")
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}
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// gnark uses a different pairing algorithm which might produce
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// different but also correct outputs, we need to scale the output by s
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return 1
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}
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// normalizeGTToGnark scales a Cloudflare/Google GT element by `s`
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// so that it can be compared with a gnark GT point.
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//
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// For the definition of `s` see 3.5 in https://eprint.iacr.org/2015/192.pdf
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func normalizeGTToGnark(cloudflareOrGoogleGT []byte) *gnark.GT {
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// Compute s = 2*u(6*u^2 + 3*u + 1)
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u, _ := new(big.Int).SetString("0x44e992b44a6909f1", 0)
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u_exp2 := new(big.Int).Exp(u, big.NewInt(2), nil) // u^2
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u_6_exp2 := new(big.Int).Mul(big.NewInt(6), u_exp2) // 6*u^2
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@ -170,14 +176,12 @@ func fuzzPair(data []byte) int {
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u_2 := new(big.Int).Mul(big.NewInt(2), u) // 2*u
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s := u_2.Mul(u_2, inner) // 2*u(6*u^2 + 3*u + 1)
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gRes := new(bn254.GT)
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if err := gRes.SetBytes(clPair); err != nil {
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// Scale the Cloudflare/Google GT element by `s`
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gRes := new(gnark.GT)
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if err := gRes.Unmarshal(cloudflareOrGoogleGT); err != nil {
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panic(err)
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}
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gRes = gRes.Exp(*gRes, s)
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if !bytes.Equal(cPair.Marshal(), gRes.Marshal()) {
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panic("pairing mismatch: cloudflare/gnark")
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}
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return 1
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return gRes
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}
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