libgo/go/golang_org/x/crypto/chacha20poly1305/chacha20poly1305_amd64.go

   1 // Copyright 2016 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 // +build go1.7,amd64,!gccgo,!appengine
   6
   7 package chacha20poly1305
   8
   9 import "encoding/binary"
  10
  11 //go:noescape
  12 func chacha20Poly1305Open(dst []byte, key []uint32, src, ad []byte) bool
  13
  14 //go:noescape
  15 func chacha20Poly1305Seal(dst []byte, key []uint32, src, ad []byte)
  16
  17 // cpuid is implemented in chacha20poly1305_amd64.s.
  18 func cpuid(eaxArg, ecxArg uint32) (eax, ebx, ecx, edx uint32)
  19
  20 // xgetbv with ecx = 0 is implemented in chacha20poly1305_amd64.s.
  21 func xgetbv() (eax, edx uint32)
  22
  23 var (
  24         useASM  bool
  25         useAVX2 bool
  26 )
  27
  28 func init() {
  29         detectCpuFeatures()
  30 }
  31
  32 // detectCpuFeatures is used to detect if cpu instructions
  33 // used by the functions implemented in assembler in
  34 // chacha20poly1305_amd64.s are supported.
  35 func detectCpuFeatures() {
  36         maxId, _, _, _ := cpuid(0, 0)
  37         if maxId < 1 {
  38                 return
  39         }
  40
  41         _, _, ecx1, _ := cpuid(1, 0)
  42
  43         haveSSSE3 := isSet(9, ecx1)
  44         useASM = haveSSSE3
  45
  46         haveOSXSAVE := isSet(27, ecx1)
  47
  48         osSupportsAVX := false
  49         // For XGETBV, OSXSAVE bit is required and sufficient.
  50         if haveOSXSAVE {
  51                 eax, _ := xgetbv()
  52                 // Check if XMM and YMM registers have OS support.
  53                 osSupportsAVX = isSet(1, eax) && isSet(2, eax)
  54         }
  55         haveAVX := isSet(28, ecx1) && osSupportsAVX
  56
  57         if maxId < 7 {
  58                 return
  59         }
  60
  61         _, ebx7, _, _ := cpuid(7, 0)
  62         haveAVX2 := isSet(5, ebx7) && haveAVX
  63         haveBMI2 := isSet(8, ebx7)
  64
  65         useAVX2 = haveAVX2 && haveBMI2
  66 }
  67
  68 // isSet checks if bit at bitpos is set in value.
  69 func isSet(bitpos uint, value uint32) bool {
  70         return value&(1<<bitpos) != 0
  71 }
  72
  73 // setupState writes a ChaCha20 input matrix to state. See
  74 // https://tools.ietf.org/html/rfc7539#section-2.3.
  75 func setupState(state *[16]uint32, key *[32]byte, nonce []byte) {
  76         state[0] = 0x61707865
  77         state[1] = 0x3320646e
  78         state[2] = 0x79622d32
  79         state[3] = 0x6b206574
  80
  81         state[4] = binary.LittleEndian.Uint32(key[:4])
  82         state[5] = binary.LittleEndian.Uint32(key[4:8])
  83         state[6] = binary.LittleEndian.Uint32(key[8:12])
  84         state[7] = binary.LittleEndian.Uint32(key[12:16])
  85         state[8] = binary.LittleEndian.Uint32(key[16:20])
  86         state[9] = binary.LittleEndian.Uint32(key[20:24])
  87         state[10] = binary.LittleEndian.Uint32(key[24:28])
  88         state[11] = binary.LittleEndian.Uint32(key[28:32])
  89
  90         state[12] = 0
  91         state[13] = binary.LittleEndian.Uint32(nonce[:4])
  92         state[14] = binary.LittleEndian.Uint32(nonce[4:8])
  93         state[15] = binary.LittleEndian.Uint32(nonce[8:12])
  94 }
  95
  96 func (c *chacha20poly1305) seal(dst, nonce, plaintext, additionalData []byte) []byte {
  97         if !useASM {
  98                 return c.sealGeneric(dst, nonce, plaintext, additionalData)
  99         }
 100
 101         var state [16]uint32
 102         setupState(&state, &c.key, nonce)
 103
 104         ret, out := sliceForAppend(dst, len(plaintext)+16)
 105         chacha20Poly1305Seal(out[:], state[:], plaintext, additionalData)
 106         return ret
 107 }
 108
 109 func (c *chacha20poly1305) open(dst, nonce, ciphertext, additionalData []byte) ([]byte, error) {
 110         if !useASM {
 111                 return c.openGeneric(dst, nonce, ciphertext, additionalData)
 112         }
 113
 114         var state [16]uint32
 115         setupState(&state, &c.key, nonce)
 116
 117         ciphertext = ciphertext[:len(ciphertext)-16]
 118         ret, out := sliceForAppend(dst, len(ciphertext))
 119         if !chacha20Poly1305Open(out, state[:], ciphertext, additionalData) {
 120                 for i := range out {
 121                         out[i] = 0
 122                 }
 123                 return nil, errOpen
 124         }
 125
 126         return ret, nil
 127 }