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