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// Copyright 2016 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.
// +build go1.7,amd64,!gccgo,!appengine
package chacha20poly1305
import "encoding/binary"
//go:noescape
func chacha20Poly1305Open(dst []byte, key []uint32, src, ad []byte) bool
//go:noescape
func chacha20Poly1305Seal(dst []byte, key []uint32, src, ad []byte)
// cpuid is implemented in chacha20poly1305_amd64.s.
func cpuid(eaxArg, ecxArg uint32) (eax, ebx, ecx, edx uint32)
// xgetbv with ecx = 0 is implemented in chacha20poly1305_amd64.s.
func xgetbv() (eax, edx uint32)
var (
useASM bool
useAVX2 bool
)
func init() {
detectCPUFeatures()
}
// detectCPUFeatures is used to detect if cpu instructions
// used by the functions implemented in assembler in
// chacha20poly1305_amd64.s are supported.
func detectCPUFeatures() {
maxID, _, _, _ := cpuid(0, 0)
if maxID < 1 {
return
}
_, _, ecx1, _ := cpuid(1, 0)
haveSSSE3 := isSet(9, ecx1)
useASM = haveSSSE3
haveOSXSAVE := isSet(27, ecx1)
osSupportsAVX := false
// For XGETBV, OSXSAVE bit is required and sufficient.
if haveOSXSAVE {
eax, _ := xgetbv()
// Check if XMM and YMM registers have OS support.
osSupportsAVX = isSet(1, eax) && isSet(2, eax)
}
haveAVX := isSet(28, ecx1) && osSupportsAVX
if maxID < 7 {
return
}
_, ebx7, _, _ := cpuid(7, 0)
haveAVX2 := isSet(5, ebx7) && haveAVX
haveBMI2 := isSet(8, ebx7)
useAVX2 = haveAVX2 && haveBMI2
}
// isSet checks if bit at bitpos is set in value.
func isSet(bitpos uint, value uint32) bool {
return value&(1<<bitpos) != 0
}
// setupState writes a ChaCha20 input matrix to state. See
// https://tools.ietf.org/html/rfc7539#section-2.3.
func setupState(state *[16]uint32, key *[32]byte, nonce []byte) {
state[0] = 0x61707865
state[1] = 0x3320646e
state[2] = 0x79622d32
state[3] = 0x6b206574
state[4] = binary.LittleEndian.Uint32(key[:4])
state[5] = binary.LittleEndian.Uint32(key[4:8])
state[6] = binary.LittleEndian.Uint32(key[8:12])
state[7] = binary.LittleEndian.Uint32(key[12:16])
state[8] = binary.LittleEndian.Uint32(key[16:20])
state[9] = binary.LittleEndian.Uint32(key[20:24])
state[10] = binary.LittleEndian.Uint32(key[24:28])
state[11] = binary.LittleEndian.Uint32(key[28:32])
state[12] = 0
state[13] = binary.LittleEndian.Uint32(nonce[:4])
state[14] = binary.LittleEndian.Uint32(nonce[4:8])
state[15] = binary.LittleEndian.Uint32(nonce[8:12])
}
func (c *chacha20poly1305) seal(dst, nonce, plaintext, additionalData []byte) []byte {
if !useASM {
return c.sealGeneric(dst, nonce, plaintext, additionalData)
}
var state [16]uint32
setupState(&state, &c.key, nonce)
ret, out := sliceForAppend(dst, len(plaintext)+16)
chacha20Poly1305Seal(out[:], state[:], plaintext, additionalData)
return ret
}
func (c *chacha20poly1305) open(dst, nonce, ciphertext, additionalData []byte) ([]byte, error) {
if !useASM {
return c.openGeneric(dst, nonce, ciphertext, additionalData)
}
var state [16]uint32
setupState(&state, &c.key, nonce)
ciphertext = ciphertext[:len(ciphertext)-16]
ret, out := sliceForAppend(dst, len(ciphertext))
if !chacha20Poly1305Open(out, state[:], ciphertext, additionalData) {
for i := range out {
out[i] = 0
}
return nil, errOpen
}
return ret, nil
}
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