58 lines
1.3 KiB
Go
58 lines
1.3 KiB
Go
// Copyright 2012 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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package ssh
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// Message authentication support
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import (
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"crypto/hmac"
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"crypto/sha1"
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"hash"
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)
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type macMode struct {
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keySize int
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new func(key []byte) hash.Hash
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}
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// truncatingMAC wraps around a hash.Hash and truncates the output digest to
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// a given size.
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type truncatingMAC struct {
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length int
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hmac hash.Hash
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}
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func (t truncatingMAC) Write(data []byte) (int, error) {
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return t.hmac.Write(data)
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}
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func (t truncatingMAC) Sum(in []byte) []byte {
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out := t.hmac.Sum(in)
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return out[:len(in)+t.length]
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}
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func (t truncatingMAC) Reset() {
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t.hmac.Reset()
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}
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func (t truncatingMAC) Size() int {
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return t.length
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}
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func (t truncatingMAC) BlockSize() int { return t.hmac.BlockSize() }
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// Specifies a default set of MAC algorithms and a preference order.
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// This is based on RFC 4253, section 6.4, with the removal of the
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// hmac-md5 variants as they have reached the end of their useful life.
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var DefaultMACOrder = []string{"hmac-sha1", "hmac-sha1-96"}
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var macModes = map[string]*macMode{
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"hmac-sha1": {20, func(key []byte) hash.Hash {
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return hmac.New(sha1.New, key)
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}},
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"hmac-sha1-96": {20, func(key []byte) hash.Hash {
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return truncatingMAC{12, hmac.New(sha1.New, key)}
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}},
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}
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