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// Copyright 2012 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.
package ssh
// Message authentication support
import (
"crypto/hmac"
"crypto/sha1"
"crypto/sha256"
"hash"
)
type macMode struct {
keySize int
etm bool
new func(key []byte) hash.Hash
}
// truncatingMAC wraps around a hash.Hash and truncates the output digest to
// a given size.
type truncatingMAC struct {
length int
hmac hash.Hash
}
func (t truncatingMAC) Write(data []byte) (int, error) {
return t.hmac.Write(data)
}
func (t truncatingMAC) Sum(in []byte) []byte {
out := t.hmac.Sum(in)
return out[:len(in)+t.length]
}
func (t truncatingMAC) Reset() {
t.hmac.Reset()
}
func (t truncatingMAC) Size() int {
return t.length
}
func (t truncatingMAC) BlockSize() int { return t.hmac.BlockSize() }
var macModes = map[string]*macMode{
"hmac-sha2-256-etm@openssh.com": {32, true, func(key []byte) hash.Hash {
return hmac.New(sha256.New, key)
}},
"hmac-sha2-256": {32, false, func(key []byte) hash.Hash {
return hmac.New(sha256.New, key)
}},
"hmac-sha1": {20, false, func(key []byte) hash.Hash {
return hmac.New(sha1.New, key)
}},
"hmac-sha1-96": {20, false, func(key []byte) hash.Hash {
return truncatingMAC{12, hmac.New(sha1.New, key)}
}},
}