diff --git a/internal/poly1305/bits_compat.go b/internal/poly1305/bits_compat.go deleted file mode 100644 index d33c8890fc..0000000000 --- a/internal/poly1305/bits_compat.go +++ /dev/null @@ -1,39 +0,0 @@ -// 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. - -//go:build !go1.13 - -package poly1305 - -// Generic fallbacks for the math/bits intrinsics, copied from -// src/math/bits/bits.go. They were added in Go 1.12, but Add64 and Sum64 had -// variable time fallbacks until Go 1.13. - -func bitsAdd64(x, y, carry uint64) (sum, carryOut uint64) { - sum = x + y + carry - carryOut = ((x & y) | ((x | y) &^ sum)) >> 63 - return -} - -func bitsSub64(x, y, borrow uint64) (diff, borrowOut uint64) { - diff = x - y - borrow - borrowOut = ((^x & y) | (^(x ^ y) & diff)) >> 63 - return -} - -func bitsMul64(x, y uint64) (hi, lo uint64) { - const mask32 = 1<<32 - 1 - x0 := x & mask32 - x1 := x >> 32 - y0 := y & mask32 - y1 := y >> 32 - w0 := x0 * y0 - t := x1*y0 + w0>>32 - w1 := t & mask32 - w2 := t >> 32 - w1 += x0 * y1 - hi = x1*y1 + w2 + w1>>32 - lo = x * y - return -} diff --git a/internal/poly1305/bits_go1.13.go b/internal/poly1305/bits_go1.13.go deleted file mode 100644 index 495c1fa697..0000000000 --- a/internal/poly1305/bits_go1.13.go +++ /dev/null @@ -1,21 +0,0 @@ -// 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. - -//go:build go1.13 - -package poly1305 - -import "math/bits" - -func bitsAdd64(x, y, carry uint64) (sum, carryOut uint64) { - return bits.Add64(x, y, carry) -} - -func bitsSub64(x, y, borrow uint64) (diff, borrowOut uint64) { - return bits.Sub64(x, y, borrow) -} - -func bitsMul64(x, y uint64) (hi, lo uint64) { - return bits.Mul64(x, y) -} diff --git a/internal/poly1305/sum_generic.go b/internal/poly1305/sum_generic.go index e041da5ea3..ec2202bd7d 100644 --- a/internal/poly1305/sum_generic.go +++ b/internal/poly1305/sum_generic.go @@ -7,7 +7,10 @@ package poly1305 -import "encoding/binary" +import ( + "encoding/binary" + "math/bits" +) // Poly1305 [RFC 7539] is a relatively simple algorithm: the authentication tag // for a 64 bytes message is approximately @@ -114,13 +117,13 @@ type uint128 struct { } func mul64(a, b uint64) uint128 { - hi, lo := bitsMul64(a, b) + hi, lo := bits.Mul64(a, b) return uint128{lo, hi} } func add128(a, b uint128) uint128 { - lo, c := bitsAdd64(a.lo, b.lo, 0) - hi, c := bitsAdd64(a.hi, b.hi, c) + lo, c := bits.Add64(a.lo, b.lo, 0) + hi, c := bits.Add64(a.hi, b.hi, c) if c != 0 { panic("poly1305: unexpected overflow") } @@ -155,8 +158,8 @@ func updateGeneric(state *macState, msg []byte) { // hide leading zeroes. For full chunks, that's 1 << 128, so we can just // add 1 to the most significant (2¹²⁸) limb, h2. if len(msg) >= TagSize { - h0, c = bitsAdd64(h0, binary.LittleEndian.Uint64(msg[0:8]), 0) - h1, c = bitsAdd64(h1, binary.LittleEndian.Uint64(msg[8:16]), c) + h0, c = bits.Add64(h0, binary.LittleEndian.Uint64(msg[0:8]), 0) + h1, c = bits.Add64(h1, binary.LittleEndian.Uint64(msg[8:16]), c) h2 += c + 1 msg = msg[TagSize:] @@ -165,8 +168,8 @@ func updateGeneric(state *macState, msg []byte) { copy(buf[:], msg) buf[len(msg)] = 1 - h0, c = bitsAdd64(h0, binary.LittleEndian.Uint64(buf[0:8]), 0) - h1, c = bitsAdd64(h1, binary.LittleEndian.Uint64(buf[8:16]), c) + h0, c = bits.Add64(h0, binary.LittleEndian.Uint64(buf[0:8]), 0) + h1, c = bits.Add64(h1, binary.LittleEndian.Uint64(buf[8:16]), c) h2 += c msg = nil @@ -219,9 +222,9 @@ func updateGeneric(state *macState, msg []byte) { m3 := h2r1 t0 := m0.lo - t1, c := bitsAdd64(m1.lo, m0.hi, 0) - t2, c := bitsAdd64(m2.lo, m1.hi, c) - t3, _ := bitsAdd64(m3.lo, m2.hi, c) + t1, c := bits.Add64(m1.lo, m0.hi, 0) + t2, c := bits.Add64(m2.lo, m1.hi, c) + t3, _ := bits.Add64(m3.lo, m2.hi, c) // Now we have the result as 4 64-bit limbs, and we need to reduce it // modulo 2¹³⁰ - 5. The special shape of this Crandall prime lets us do @@ -243,14 +246,14 @@ func updateGeneric(state *macState, msg []byte) { // To add c * 5 to h, we first add cc = c * 4, and then add (cc >> 2) = c. - h0, c = bitsAdd64(h0, cc.lo, 0) - h1, c = bitsAdd64(h1, cc.hi, c) + h0, c = bits.Add64(h0, cc.lo, 0) + h1, c = bits.Add64(h1, cc.hi, c) h2 += c cc = shiftRightBy2(cc) - h0, c = bitsAdd64(h0, cc.lo, 0) - h1, c = bitsAdd64(h1, cc.hi, c) + h0, c = bits.Add64(h0, cc.lo, 0) + h1, c = bits.Add64(h1, cc.hi, c) h2 += c // h2 is at most 3 + 1 + 1 = 5, making the whole of h at most @@ -287,9 +290,9 @@ func finalize(out *[TagSize]byte, h *[3]uint64, s *[2]uint64) { // in constant time, we compute t = h - (2¹³⁰ - 5), and select h as the // result if the subtraction underflows, and t otherwise. - hMinusP0, b := bitsSub64(h0, p0, 0) - hMinusP1, b := bitsSub64(h1, p1, b) - _, b = bitsSub64(h2, p2, b) + hMinusP0, b := bits.Sub64(h0, p0, 0) + hMinusP1, b := bits.Sub64(h1, p1, b) + _, b = bits.Sub64(h2, p2, b) // h = h if h < p else h - p h0 = select64(b, h0, hMinusP0) @@ -301,8 +304,8 @@ func finalize(out *[TagSize]byte, h *[3]uint64, s *[2]uint64) { // // by just doing a wide addition with the 128 low bits of h and discarding // the overflow. - h0, c := bitsAdd64(h0, s[0], 0) - h1, _ = bitsAdd64(h1, s[1], c) + h0, c := bits.Add64(h0, s[0], 0) + h1, _ = bits.Add64(h1, s[1], c) binary.LittleEndian.PutUint64(out[0:8], h0) binary.LittleEndian.PutUint64(out[8:16], h1)