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curve25519: use crypto/ecdh on Go 1.20
For golang/go#52221 Change-Id: I27e867d4cc89cd52c8d510f0dbab4e89b7cd4763 Reviewed-on: https://go-review.googlesource.com/c/crypto/+/451115 Auto-Submit: Filippo Valsorda <[email protected]> Reviewed-by: Cherry Mui <[email protected]> TryBot-Result: Gopher Robot <[email protected]> Run-TryBot: Filippo Valsorda <[email protected]> Reviewed-by: Roland Shoemaker <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,105 @@ | ||
| // Copyright 2019 The Go Authors. All rights reserved. | ||
| // Use of this source code is governed by a BSD-style | ||
| // license that can be found in the LICENSE file. | ||
|
|
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| //go:build !go1.20 | ||
|
|
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| package curve25519 | ||
|
|
||
| import ( | ||
| "crypto/subtle" | ||
| "errors" | ||
| "strconv" | ||
|
|
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| "golang.org/x/crypto/curve25519/internal/field" | ||
| ) | ||
|
|
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| func scalarMult(dst, scalar, point *[32]byte) { | ||
| var e [32]byte | ||
|
|
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| copy(e[:], scalar[:]) | ||
| e[0] &= 248 | ||
| e[31] &= 127 | ||
| e[31] |= 64 | ||
|
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| var x1, x2, z2, x3, z3, tmp0, tmp1 field.Element | ||
| x1.SetBytes(point[:]) | ||
| x2.One() | ||
| x3.Set(&x1) | ||
| z3.One() | ||
|
|
||
| swap := 0 | ||
| for pos := 254; pos >= 0; pos-- { | ||
| b := e[pos/8] >> uint(pos&7) | ||
| b &= 1 | ||
| swap ^= int(b) | ||
| x2.Swap(&x3, swap) | ||
| z2.Swap(&z3, swap) | ||
| swap = int(b) | ||
|
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| tmp0.Subtract(&x3, &z3) | ||
| tmp1.Subtract(&x2, &z2) | ||
| x2.Add(&x2, &z2) | ||
| z2.Add(&x3, &z3) | ||
| z3.Multiply(&tmp0, &x2) | ||
| z2.Multiply(&z2, &tmp1) | ||
| tmp0.Square(&tmp1) | ||
| tmp1.Square(&x2) | ||
| x3.Add(&z3, &z2) | ||
| z2.Subtract(&z3, &z2) | ||
| x2.Multiply(&tmp1, &tmp0) | ||
| tmp1.Subtract(&tmp1, &tmp0) | ||
| z2.Square(&z2) | ||
|
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| z3.Mult32(&tmp1, 121666) | ||
| x3.Square(&x3) | ||
| tmp0.Add(&tmp0, &z3) | ||
| z3.Multiply(&x1, &z2) | ||
| z2.Multiply(&tmp1, &tmp0) | ||
| } | ||
|
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||
| x2.Swap(&x3, swap) | ||
| z2.Swap(&z3, swap) | ||
|
|
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| z2.Invert(&z2) | ||
| x2.Multiply(&x2, &z2) | ||
| copy(dst[:], x2.Bytes()) | ||
| } | ||
|
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| func scalarBaseMult(dst, scalar *[32]byte) { | ||
| checkBasepoint() | ||
| scalarMult(dst, scalar, &basePoint) | ||
| } | ||
|
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| func x25519(dst *[32]byte, scalar, point []byte) ([]byte, error) { | ||
| var in [32]byte | ||
| if l := len(scalar); l != 32 { | ||
| return nil, errors.New("bad scalar length: " + strconv.Itoa(l) + ", expected 32") | ||
| } | ||
| if l := len(point); l != 32 { | ||
| return nil, errors.New("bad point length: " + strconv.Itoa(l) + ", expected 32") | ||
| } | ||
| copy(in[:], scalar) | ||
| if &point[0] == &Basepoint[0] { | ||
| scalarBaseMult(dst, &in) | ||
| } else { | ||
| var base, zero [32]byte | ||
| copy(base[:], point) | ||
| scalarMult(dst, &in, &base) | ||
| if subtle.ConstantTimeCompare(dst[:], zero[:]) == 1 { | ||
| return nil, errors.New("bad input point: low order point") | ||
| } | ||
| } | ||
| return dst[:], nil | ||
| } | ||
|
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| func checkBasepoint() { | ||
| if subtle.ConstantTimeCompare(Basepoint, []byte{ | ||
| 0x09, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, | ||
| 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, | ||
| 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, | ||
| 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, | ||
| }) != 1 { | ||
| panic("curve25519: global Basepoint value was modified") | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,46 @@ | ||
| // Copyright 2022 The Go Authors. All rights reserved. | ||
| // Use of this source code is governed by a BSD-style | ||
| // license that can be found in the LICENSE file. | ||
|
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| //go:build go1.20 | ||
|
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| package curve25519 | ||
|
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| import "crypto/ecdh" | ||
|
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| func x25519(dst *[32]byte, scalar, point []byte) ([]byte, error) { | ||
| curve := ecdh.X25519() | ||
| pub, err := curve.NewPublicKey(point) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| priv, err := curve.NewPrivateKey(scalar) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| out, err := priv.ECDH(pub) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| copy(dst[:], out) | ||
| return dst[:], nil | ||
| } | ||
|
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| func scalarMult(dst, scalar, point *[32]byte) { | ||
| if _, err := x25519(dst, scalar[:], point[:]); err != nil { | ||
| // The only error condition for x25519 when the inputs are 32 bytes long | ||
| // is if the output would have been the all-zero value. | ||
| for i := range dst { | ||
| dst[i] = 0 | ||
| } | ||
| } | ||
| } | ||
|
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| func scalarBaseMult(dst, scalar *[32]byte) { | ||
| curve := ecdh.X25519() | ||
| priv, err := curve.NewPrivateKey(scalar[:]) | ||
| if err != nil { | ||
| panic("curve25519: internal error: scalarBaseMult was not 32 bytes") | ||
| } | ||
| copy(dst[:], priv.PublicKey().Bytes()) | ||
| } |
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