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author | 2021-08-12 21:03:24 +0200 | |
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committer | 2021-08-12 21:03:24 +0200 | |
commit | 98263a7de64269898a2f81207e38943b5c8e8653 (patch) | |
tree | 743c90f109a6c5d27832d1dcef2388d939f0f77a /vendor/golang.org/x/crypto/curve25519/curve25519.go | |
parent | Text duplication fix (#137) (diff) | |
download | gotosocial-98263a7de64269898a2f81207e38943b5c8e8653.tar.xz |
Grand test fixup (#138)
* start fixing up tests
* fix up tests + automate with drone
* fiddle with linting
* messing about with drone.yml
* some more fiddling
* hmmm
* add cache
* add vendor directory
* verbose
* ci updates
* update some little things
* update sig
Diffstat (limited to 'vendor/golang.org/x/crypto/curve25519/curve25519.go')
-rw-r--r-- | vendor/golang.org/x/crypto/curve25519/curve25519.go | 145 |
1 files changed, 145 insertions, 0 deletions
diff --git a/vendor/golang.org/x/crypto/curve25519/curve25519.go b/vendor/golang.org/x/crypto/curve25519/curve25519.go new file mode 100644 index 000000000..cda3fdd35 --- /dev/null +++ b/vendor/golang.org/x/crypto/curve25519/curve25519.go @@ -0,0 +1,145 @@ +// 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. + +// Package curve25519 provides an implementation of the X25519 function, which +// performs scalar multiplication on the elliptic curve known as Curve25519. +// See RFC 7748. +package curve25519 // import "golang.org/x/crypto/curve25519" + +import ( + "crypto/subtle" + "fmt" + + "golang.org/x/crypto/curve25519/internal/field" +) + +// ScalarMult sets dst to the product scalar * point. +// +// Deprecated: when provided a low-order point, ScalarMult will set dst to all +// zeroes, irrespective of the scalar. Instead, use the X25519 function, which +// will return an error. +func ScalarMult(dst, scalar, point *[32]byte) { + var e [32]byte + + copy(e[:], scalar[:]) + e[0] &= 248 + e[31] &= 127 + e[31] |= 64 + + 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) + + 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) + + z3.Mult32(&tmp1, 121666) + x3.Square(&x3) + tmp0.Add(&tmp0, &z3) + z3.Multiply(&x1, &z2) + z2.Multiply(&tmp1, &tmp0) + } + + x2.Swap(&x3, swap) + z2.Swap(&z3, swap) + + z2.Invert(&z2) + x2.Multiply(&x2, &z2) + copy(dst[:], x2.Bytes()) +} + +// ScalarBaseMult sets dst to the product scalar * base where base is the +// standard generator. +// +// It is recommended to use the X25519 function with Basepoint instead, as +// copying into fixed size arrays can lead to unexpected bugs. +func ScalarBaseMult(dst, scalar *[32]byte) { + ScalarMult(dst, scalar, &basePoint) +} + +const ( + // ScalarSize is the size of the scalar input to X25519. + ScalarSize = 32 + // PointSize is the size of the point input to X25519. + PointSize = 32 +) + +// Basepoint is the canonical Curve25519 generator. +var Basepoint []byte + +var basePoint = [32]byte{9, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0} + +func init() { Basepoint = basePoint[:] } + +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") + } +} + +// X25519 returns the result of the scalar multiplication (scalar * point), +// according to RFC 7748, Section 5. scalar, point and the return value are +// slices of 32 bytes. +// +// scalar can be generated at random, for example with crypto/rand. point should +// be either Basepoint or the output of another X25519 call. +// +// If point is Basepoint (but not if it's a different slice with the same +// contents) a precomputed implementation might be used for performance. +func X25519(scalar, point []byte) ([]byte, error) { + // Outline the body of function, to let the allocation be inlined in the + // caller, and possibly avoid escaping to the heap. + var dst [32]byte + return x25519(&dst, scalar, point) +} + +func x25519(dst *[32]byte, scalar, point []byte) ([]byte, error) { + var in [32]byte + if l := len(scalar); l != 32 { + return nil, fmt.Errorf("bad scalar length: %d, expected %d", l, 32) + } + if l := len(point); l != 32 { + return nil, fmt.Errorf("bad point length: %d, expected %d", l, 32) + } + copy(in[:], scalar) + if &point[0] == &Basepoint[0] { + checkBasepoint() + ScalarBaseMult(dst, &in) + } else { + var base, zero [32]byte + copy(base[:], point) + ScalarMult(dst, &in, &base) + if subtle.ConstantTimeCompare(dst[:], zero[:]) == 1 { + return nil, fmt.Errorf("bad input point: low order point") + } + } + return dst[:], nil +} |