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crypto/ed25519/internal/edwards25519: sync with filippo.io/edwards25519

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Import the following commits (and minor comment fixes):

    * 17a0e59 - field: fix heap escape in SqrtRatio <Filippo Valsorda>
    * edec5b9 - field: fix SqrtRatio when arguments and receiver alias <Filippo Valsorda>
    * 26ce6fc - edwards25519: expand the SetUniformBytes docs <Filippo Valsorda>
    * c1c1311 - edwards25519: make Scalar and field.Element setters return errors <Filippo Valsorda>

Change-Id: I102eb04818a2bed43467f3eda6fd4c46b09878fe
Reviewed-on: https://go-review.googlesource.com/c/go/+/373077
Trust: Filippo Valsorda <filippo@golang.org>
Run-TryBot: Filippo Valsorda <filippo@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Katie Hockman <katie@golang.org>
Trust: Katie Hockman <katie@golang.org>
Run-TryBot: Katie Hockman <katie@golang.org>
This commit is contained in:
Filippo Valsorda 2022-01-05 08:55:55 -05:00
parent 81767e23c2
commit 27ec2bf0dd
8 changed files with 90 additions and 48 deletions
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25
src/crypto/ed25519/ed25519.go
View File

@ -126,7 +126,10 @@ func newKeyFromSeed(privateKey, seed []byte) {
}
h := sha512.Sum512(seed)
s := edwards25519.NewScalar().SetBytesWithClamping(h[:32])
s, err := edwards25519.NewScalar().SetBytesWithClamping(h[:32])
if err != nil {
panic("ed25519: internal error: setting scalar failed")
}
A := (&edwards25519.Point{}).ScalarBaseMult(s)
publicKey := A.Bytes()
@ -152,7 +155,10 @@ func sign(signature, privateKey, message []byte) {
seed, publicKey := privateKey[:SeedSize], privateKey[SeedSize:]
h := sha512.Sum512(seed)
s := edwards25519.NewScalar().SetBytesWithClamping(h[:32])
s, err := edwards25519.NewScalar().SetBytesWithClamping(h[:32])
if err != nil {
panic("ed25519: internal error: setting scalar failed")
}
prefix := h[32:]
mh := sha512.New()
@ -160,7 +166,10 @@ func sign(signature, privateKey, message []byte) {
mh.Write(message)
messageDigest := make([]byte, 0, sha512.Size)
messageDigest = mh.Sum(messageDigest)
r := edwards25519.NewScalar().SetUniformBytes(messageDigest)
r, err := edwards25519.NewScalar().SetUniformBytes(messageDigest)
if err != nil {
panic("ed25519: internal error: setting scalar failed")
}
R := (&edwards25519.Point{}).ScalarBaseMult(r)
@ -170,7 +179,10 @@ func sign(signature, privateKey, message []byte) {
kh.Write(message)
hramDigest := make([]byte, 0, sha512.Size)
hramDigest = kh.Sum(hramDigest)
k := edwards25519.NewScalar().SetUniformBytes(hramDigest)
k, err := edwards25519.NewScalar().SetUniformBytes(hramDigest)
if err != nil {
panic("ed25519: internal error: setting scalar failed")
}
S := edwards25519.NewScalar().MultiplyAdd(k, s, r)
@ -200,7 +212,10 @@ func Verify(publicKey PublicKey, message, sig []byte) bool {
kh.Write(message)
hramDigest := make([]byte, 0, sha512.Size)
hramDigest = kh.Sum(hramDigest)
k := edwards25519.NewScalar().SetUniformBytes(hramDigest)
k, err := edwards25519.NewScalar().SetUniformBytes(hramDigest)
if err != nil {
panic("ed25519: internal error: setting scalar failed")
}
S, err := edwards25519.NewScalar().SetCanonicalBytes(sig[32:])
if err != nil {

6
src/crypto/ed25519/internal/edwards25519/edwards25519.go
View File

@ -151,10 +151,10 @@ func (v *Point) SetBytes(x []byte) (*Point, error) {
// at https://hdevalence.ca/blog/2020-10-04-its-25519am, specifically the
// "Canonical A, R" section.
if len(x) != 32 {
y, err := new(field.Element).SetBytes(x)
if err != nil {
return nil, errors.New("edwards25519: invalid point encoding length")
}
y := new(field.Element).SetBytes(x)
// -x² + y² = 1 + dx²y²
// x² + dx²y² = x²(dy² + 1) = y² - 1
@ -224,7 +224,7 @@ func (v *Point) fromP2(p *projP2) *Point {
}
// d is a constant in the curve equation.
var d = new(field.Element).SetBytes([]byte{
var d, _ = new(field.Element).SetBytes([]byte{
0xa3, 0x78, 0x59, 0x13, 0xca, 0x4d, 0xeb, 0x75,
0xab, 0xd8, 0x41, 0x41, 0x4d, 0x0a, 0x70, 0x00,
0x98, 0xe8, 0x79, 0x77, 0x79, 0x40, 0xc7, 0x8c,

40
src/crypto/ed25519/internal/edwards25519/field/fe.go
View File

@ -8,6 +8,7 @@ package field
import (
"crypto/subtle"
"encoding/binary"
"errors"
"math/bits"
)
@ -186,14 +187,17 @@ func (v *Element) Set(a *Element) *Element {
return v
}
// SetBytes sets v to x, which must be a 32-byte little-endian encoding.
// SetBytes sets v to x, where x is a 32-byte little-endian encoding. If x is
// not of the right length, SetBytes returns nil and an error, and the
// receiver is unchanged.
//
// Consistent with RFC 7748, the most significant bit (the high bit of the
// last byte) is ignored, and non-canonical values (2^255-19 through 2^255-1)
// are accepted. Note that this is laxer than specified by RFC 8032.
func (v *Element) SetBytes(x []byte) *Element {
// are accepted. Note that this is laxer than specified by RFC 8032, but
// consistent with most Ed25519 implementations.
func (v *Element) SetBytes(x []byte) (*Element, error) {
if len(x) != 32 {
panic("edwards25519: invalid field element input size")
return nil, errors.New("edwards25519: invalid field element input size")
}
// Bits 0:51 (bytes 0:8, bits 0:64, shift 0, mask 51).
@ -208,12 +212,12 @@ func (v *Element) SetBytes(x []byte) *Element {
// Bits 153:204 (bytes 19:27, bits 152:216, shift 1, mask 51).
v.l3 = binary.LittleEndian.Uint64(x[19:27]) >> 1
v.l3 &= maskLow51Bits
// Bits 204:251 (bytes 24:32, bits 192:256, shift 12, mask 51).
// Bits 204:255 (bytes 24:32, bits 192:256, shift 12, mask 51).
// Note: not bytes 25:33, shift 4, to avoid overread.
v.l4 = binary.LittleEndian.Uint64(x[24:32]) >> 12
v.l4 &= maskLow51Bits
return v
return v, nil
}
// Bytes returns the canonical 32-byte little-endian encoding of v.
@ -391,26 +395,26 @@ var sqrtM1 = &Element{1718705420411056, 234908883556509,
// If u/v is square, SqrtRatio returns r and 1. If u/v is not square, SqrtRatio
// sets r according to Section 4.3 of draft-irtf-cfrg-ristretto255-decaf448-00,
// and returns r and 0.
func (r *Element) SqrtRatio(u, v *Element) (rr *Element, wasSquare int) {
var a, b Element
func (r *Element) SqrtRatio(u, v *Element) (R *Element, wasSquare int) {
t0 := new(Element)
// r = (u * v3) * (u * v7)^((p-5)/8)
v2 := a.Square(v)
uv3 := b.Multiply(u, b.Multiply(v2, v))
uv7 := a.Multiply(uv3, a.Square(v2))
r.Multiply(uv3, r.Pow22523(uv7))
v2 := new(Element).Square(v)
uv3 := new(Element).Multiply(u, t0.Multiply(v2, v))
uv7 := new(Element).Multiply(uv3, t0.Square(v2))
rr := new(Element).Multiply(uv3, t0.Pow22523(uv7))
check := a.Multiply(v, a.Square(r)) // check = v * r^2
check := new(Element).Multiply(v, t0.Square(rr)) // check = v * r^2
uNeg := b.Negate(u)
uNeg := new(Element).Negate(u)
correctSignSqrt := check.Equal(u)
flippedSignSqrt := check.Equal(uNeg)
flippedSignSqrtI := check.Equal(uNeg.Multiply(uNeg, sqrtM1))
flippedSignSqrtI := check.Equal(t0.Multiply(uNeg, sqrtM1))
rPrime := b.Multiply(r, sqrtM1) // r_prime = SQRT_M1 * r
rPrime := new(Element).Multiply(rr, sqrtM1) // r_prime = SQRT_M1 * r
// r = CT_SELECT(r_prime IF flipped_sign_sqrt | flipped_sign_sqrt_i ELSE r)
r.Select(rPrime, r, flippedSignSqrt|flippedSignSqrtI)
rr.Select(rPrime, rr, flippedSignSqrt|flippedSignSqrtI)
r.Absolute(r) // Choose the nonnegative square root.
r.Absolute(rr) // Choose the nonnegative square root.
return r, correctSignSqrt | flippedSignSqrt
}

18
src/crypto/ed25519/internal/edwards25519/field/fe_alias_test.go
View File

@ -96,19 +96,33 @@ func TestAliasing(t *testing.T) {
{name: "Negate", oneArgF: (*Element).Negate},
{name: "Set", oneArgF: (*Element).Set},
{name: "Square", oneArgF: (*Element).Square},
{name: "Pow22523", oneArgF: (*Element).Pow22523},
{
name: "Mult32",
oneArgF: func(v, x *Element) *Element {
return v.Mult32(x, 0xffffffff)
},
},
{name: "Multiply", twoArgsF: (*Element).Multiply},
{name: "Add", twoArgsF: (*Element).Add},
{name: "Subtract", twoArgsF: (*Element).Subtract},
{
name: "SqrtRatio",
twoArgsF: func(v, x, y *Element) *Element {
r, _ := v.SqrtRatio(x, y)
return r
},
},
{
name: "Select0",
twoArgsF: func(v, x, y *Element) *Element {
return (*Element).Select(v, x, y, 0)
return v.Select(x, y, 0)
},
},
{
name: "Select1",
twoArgsF: func(v, x, y *Element) *Element {
return (*Element).Select(v, x, y, 1)
return v.Select(x, y, 1)
},
},
} {

2
src/crypto/ed25519/internal/edwards25519/field/fe_generic.go
View File

@ -254,6 +254,8 @@ func (v *Element) carryPropagateGeneric() *Element {
c3 := v.l3 >> 51
c4 := v.l4 >> 51
// c4 is at most 64 - 51 = 13 bits, so c4*19 is at most 18 bits, and
// the final l0 will be at most 52 bits. Similarly for the rest.
v.l0 = v.l0&maskLow51Bits + c4*19
v.l1 = v.l1&maskLow51Bits + c0
v.l2 = v.l2&maskLow51Bits + c1

16
src/crypto/ed25519/internal/edwards25519/field/fe_test.go
View File

@ -192,7 +192,8 @@ func TestSetBytesRoundTrip(t *testing.T) {
for _, tt := range tests {
b := tt.fe.Bytes()
if !bytes.Equal(b, tt.b) || new(Element).SetBytes(tt.b).Equal(&tt.fe) != 1 {
fe, _ := new(Element).SetBytes(tt.b)
if !bytes.Equal(b, tt.b) || fe.Equal(&tt.fe) != 1 {
t.Errorf("Failed fixed roundtrip: %v", tt)
}
}
@ -217,8 +218,8 @@ func TestBytesBigEquivalence(t *testing.T) {
return false
}
buf := make([]byte, 32) // pad with zeroes
copy(buf, swapEndianness(fe1.toBig().Bytes()))
buf := make([]byte, 32)
buf = swapEndianness(fe1.toBig().FillBytes(buf))
return bytes.Equal(fe.Bytes(), buf) && isInBounds(&fe) && isInBounds(&fe1)
}
@ -244,7 +245,8 @@ func (v *Element) fromBig(n *big.Int) *Element {
}
}
return v.SetBytes(buf[:32])
v.SetBytes(buf[:32])
return v
}
func (v *Element) fromDecimal(s string) *Element {
@ -471,9 +473,9 @@ func TestSqrtRatio(t *testing.T) {
}
for i, tt := range tests {
u := new(Element).SetBytes(decodeHex(tt.u))
v := new(Element).SetBytes(decodeHex(tt.v))
want := new(Element).SetBytes(decodeHex(tt.r))
u, _ := new(Element).SetBytes(decodeHex(tt.u))
v, _ := new(Element).SetBytes(decodeHex(tt.v))
want, _ := new(Element).SetBytes(decodeHex(tt.r))
got, wasSquare := new(Element).SqrtRatio(u, v)
if got.Equal(want) == 0 || wasSquare != tt.wasSquare {
t.Errorf("%d: got (%v, %v), want (%v, %v)", i, got, wasSquare, want, tt.wasSquare)

25
src/crypto/ed25519/internal/edwards25519/scalar.go
View File

@ -22,7 +22,7 @@ import (
// The zero value is a valid zero element.
type Scalar struct {
// s is the Scalar value in little-endian. The value is always reduced
// between operations.
// modulo l between operations.
s [32]byte
}
@ -79,16 +79,20 @@ func (s *Scalar) Set(x *Scalar) *Scalar {
return s
}
// SetUniformBytes sets s to an uniformly distributed value given 64 uniformly
// distributed random bytes.
func (s *Scalar) SetUniformBytes(x []byte) *Scalar {
// SetUniformBytes sets s = x mod l, where x is a 64-byte little-endian integer.
// If x is not of the right length, SetUniformBytes returns nil and an error,
// and the receiver is unchanged.
//
// SetUniformBytes can be used to set s to an uniformly distributed value given
// 64 uniformly distributed random bytes.
func (s *Scalar) SetUniformBytes(x []byte) (*Scalar, error) {
if len(x) != 64 {
panic("edwards25519: invalid SetUniformBytes input length")
return nil, errors.New("edwards25519: invalid SetUniformBytes input length")
}
var wideBytes [64]byte
copy(wideBytes[:], x[:])
scReduce(&s.s, &wideBytes)
return s
return s, nil
}
// SetCanonicalBytes sets s = x, where x is a 32-byte little-endian encoding of
@ -122,7 +126,8 @@ func isReduced(s *Scalar) bool {
// SetBytesWithClamping applies the buffer pruning described in RFC 8032,
// Section 5.1.5 (also known as clamping) and sets s to the result. The input
// must be 32 bytes, and it is not modified.
// must be 32 bytes, and it is not modified. If x is not of the right length,
// SetBytesWithClamping returns nil and an error, and the receiver is unchanged.
//
// Note that since Scalar values are always reduced modulo the prime order of
// the curve, the resulting value will not preserve any of the cofactor-clearing
@ -130,13 +135,13 @@ func isReduced(s *Scalar) bool {
// expected as long as it is applied to points on the prime order subgroup, like
// in Ed25519. In fact, it is lost to history why RFC 8032 adopted the
// irrelevant RFC 7748 clamping, but it is now required for compatibility.
func (s *Scalar) SetBytesWithClamping(x []byte) *Scalar {
func (s *Scalar) SetBytesWithClamping(x []byte) (*Scalar, error) {
// The description above omits the purpose of the high bits of the clamping
// for brevity, but those are also lost to reductions, and are also
// irrelevant to edwards25519 as they protect against a specific
// implementation bug that was once observed in a generic Montgomery ladder.
if len(x) != 32 {
panic("edwards25519: invalid SetBytesWithClamping input length")
return nil, errors.New("edwards25519: invalid SetBytesWithClamping input length")
}
var wideBytes [64]byte
copy(wideBytes[:], x[:])
@ -144,7 +149,7 @@ func (s *Scalar) SetBytesWithClamping(x []byte) *Scalar {
wideBytes[31] &= 63
wideBytes[31] |= 64
scReduce(&s.s, &wideBytes)
return s
return s, nil
}
// Bytes returns the canonical 32-byte little-endian encoding of s.

6
src/crypto/ed25519/internal/edwards25519/scalar_test.go
View File

@ -113,7 +113,7 @@ func TestScalarSetBytesWithClamping(t *testing.T) {
// Generated with libsodium.js 1.0.18 crypto_scalarmult_ed25519_base.
random := "633d368491364dc9cd4c1bf891b1d59460face1644813240a313e61f2c88216e"
s := new(Scalar).SetBytesWithClamping(decodeHex(random))
s, _ := new(Scalar).SetBytesWithClamping(decodeHex(random))
p := new(Point).ScalarBaseMult(s)
want := "1d87a9026fd0126a5736fe1628c95dd419172b5b618457e041c9c861b2494a94"
if got := hex.EncodeToString(p.Bytes()); got != want {
@ -121,7 +121,7 @@ func TestScalarSetBytesWithClamping(t *testing.T) {
}
zero := "0000000000000000000000000000000000000000000000000000000000000000"
s = new(Scalar).SetBytesWithClamping(decodeHex(zero))
s, _ = new(Scalar).SetBytesWithClamping(decodeHex(zero))
p = new(Point).ScalarBaseMult(s)
want = "693e47972caf527c7883ad1b39822f026f47db2ab0e1919955b8993aa04411d1"
if got := hex.EncodeToString(p.Bytes()); got != want {
@ -129,7 +129,7 @@ func TestScalarSetBytesWithClamping(t *testing.T) {
}
one := "ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"
s = new(Scalar).SetBytesWithClamping(decodeHex(one))
s, _ = new(Scalar).SetBytesWithClamping(decodeHex(one))
p = new(Point).ScalarBaseMult(s)
want = "12e9a68b73fd5aacdbcaf3e88c46fea6ebedb1aa84eed1842f07f8edab65e3a7"
if got := hex.EncodeToString(p.Bytes()); got != want {