github.com/technosophos/deis@v1.7.1-0.20150915173815-f9005256004b/Godeps/_workspace/src/golang.org/x/crypto/ssh/mac.go (about)

     1  // Copyright 2012 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  package ssh
     6  
     7  // Message authentication support
     8  
     9  import (
    10  	"crypto/hmac"
    11  	"crypto/sha1"
    12  	"hash"
    13  )
    14  
    15  type macMode struct {
    16  	keySize int
    17  	new     func(key []byte) hash.Hash
    18  }
    19  
    20  // truncatingMAC wraps around a hash.Hash and truncates the output digest to
    21  // a given size.
    22  type truncatingMAC struct {
    23  	length int
    24  	hmac   hash.Hash
    25  }
    26  
    27  func (t truncatingMAC) Write(data []byte) (int, error) {
    28  	return t.hmac.Write(data)
    29  }
    30  
    31  func (t truncatingMAC) Sum(in []byte) []byte {
    32  	out := t.hmac.Sum(in)
    33  	return out[:len(in)+t.length]
    34  }
    35  
    36  func (t truncatingMAC) Reset() {
    37  	t.hmac.Reset()
    38  }
    39  
    40  func (t truncatingMAC) Size() int {
    41  	return t.length
    42  }
    43  
    44  func (t truncatingMAC) BlockSize() int { return t.hmac.BlockSize() }
    45  
    46  var macModes = map[string]*macMode{
    47  	"hmac-sha1": {20, func(key []byte) hash.Hash {
    48  		return hmac.New(sha1.New, key)
    49  	}},
    50  	"hmac-sha1-96": {20, func(key []byte) hash.Hash {
    51  		return truncatingMAC{12, hmac.New(sha1.New, key)}
    52  	}},
    53  }