/usr/share/gocode/src/github.com/jacobsa/crypto/cmac/hash.go is in golang-github-jacobsa-crypto-dev 0.0~git20161111.0.293ce0c-3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 | // Copyright 2012 Aaron Jacobs. All Rights Reserved.
// Author: aaronjjacobs@gmail.com (Aaron Jacobs)
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package cmac
import (
"crypto/aes"
"crypto/cipher"
"fmt"
"hash"
"unsafe"
"github.com/jacobsa/crypto/common"
)
type cmacHash struct {
// An AES cipher configured with the original key.
ciph cipher.Block
// Generated sub-keys.
k1 []byte
k2 []byte
// Data that has been seen by Write but not yet incorporated into x, due to
// us not being sure if it is the final block or not.
//
// INVARIANT: len(data) <= blockSize
data []byte
// The current value of X, as defined in the AES-CMAC algorithm in RFC 4493.
// Initially this is a 128-bit zero, and it is updated with the current block
// when we're sure it's not the last one.
x []byte
}
func (h *cmacHash) Write(p []byte) (n int, err error) {
n = len(p)
// First step: consume enough data to expand h.data to a full block, if
// possible.
{
toConsume := blockSize - len(h.data)
if toConsume > len(p) {
toConsume = len(p)
}
h.data = append(h.data, p[:toConsume]...)
p = p[toConsume:]
}
// If there's no data left in p, it means h.data might not be a full block.
// Even if it is, we're not sure it's the final block, which we must treat
// specially. So we must stop here.
if len(p) == 0 {
return
}
// h.data is a full block and is not the last; process it.
h.writeBlocks(h.data)
h.data = h.data[:0]
// Consume any further full blocks in p that we're sure aren't the last. Note
// that we're sure that len(p) is greater than zero here.
blocksToProcess := (len(p) - 1) / blockSize
bytesToProcess := blocksToProcess * blockSize
h.writeBlocks(p[:bytesToProcess])
p = p[bytesToProcess:]
// Store the rest for later.
h.data = append(h.data, p...)
return
}
// Process block-aligned data that we're sure does not contain the final block.
//
// REQUIRES: len(p) % blockSize == 0
func (h *cmacHash) writeBlocks(p []byte) {
y := make([]byte, blockSize)
for off := 0; off < len(p); off += blockSize {
block := p[off : off+blockSize]
xorBlock(
unsafe.Pointer(&y[0]),
unsafe.Pointer(&h.x[0]),
unsafe.Pointer(&block[0]))
h.ciph.Encrypt(h.x, y)
}
return
}
func (h *cmacHash) Sum(b []byte) []byte {
dataLen := len(h.data)
// We should have at most one block left.
if dataLen > blockSize {
panic(fmt.Sprintf("Unexpected data: %x", h.data))
}
// Calculate M_last.
mLast := make([]byte, blockSize)
if dataLen == blockSize {
common.Xor(mLast, h.data, h.k1)
} else {
// TODO(jacobsa): Accept a destination buffer in common.PadBlock and
// simplify this code.
common.Xor(mLast, common.PadBlock(h.data), h.k2)
}
y := make([]byte, blockSize)
common.Xor(y, mLast, h.x)
result := make([]byte, blockSize)
h.ciph.Encrypt(result, y)
b = append(b, result...)
return b
}
func (h *cmacHash) Reset() {
h.data = h.data[:0]
h.x = make([]byte, blockSize)
}
func (h *cmacHash) Size() int {
return h.ciph.BlockSize()
}
func (h *cmacHash) BlockSize() int {
return h.ciph.BlockSize()
}
// New returns an AES-CMAC hash using the supplied key. The key must be 16, 24,
// or 32 bytes long.
func New(key []byte) (hash.Hash, error) {
switch len(key) {
case 16, 24, 32:
default:
return nil, fmt.Errorf("AES-CMAC requires a 16-, 24-, or 32-byte key.")
}
// Create a cipher.
ciph, err := aes.NewCipher(key)
if err != nil {
return nil, fmt.Errorf("aes.NewCipher: %v", err)
}
// Set up the hash object.
h := &cmacHash{ciph: ciph}
h.k1, h.k2 = generateSubkeys(ciph)
h.Reset()
return h, nil
}
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