Source file src/golang.org/x/crypto/ssh/mac.go

Documentation: golang.org/x/crypto/ssh

     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  	"crypto/sha256"
    13  	"crypto/sha512"
    14  	"hash"
    15  )
    16  
    17  type macMode struct {
    18  	keySize int
    19  	etm     bool
    20  	new     func(key []byte) hash.Hash
    21  }
    22  
    23  // truncatingMAC wraps around a hash.Hash and truncates the output digest to
    24  // a given size.
    25  type truncatingMAC struct {
    26  	length int
    27  	hmac   hash.Hash
    28  }
    29  
    30  func (t truncatingMAC) Write(data []byte) (int, error) {
    31  	return t.hmac.Write(data)
    32  }
    33  
    34  func (t truncatingMAC) Sum(in []byte) []byte {
    35  	out := t.hmac.Sum(in)
    36  	return out[:len(in)+t.length]
    37  }
    38  
    39  func (t truncatingMAC) Reset() {
    40  	t.hmac.Reset()
    41  }
    42  
    43  func (t truncatingMAC) Size() int {
    44  	return t.length
    45  }
    46  
    47  func (t truncatingMAC) BlockSize() int { return t.hmac.BlockSize() }
    48  
    49  var macModes = map[string]*macMode{
    50  	"hmac-sha2-512-etm@openssh.com": {64, true, func(key []byte) hash.Hash {
    51  		return hmac.New(sha512.New, key)
    52  	}},
    53  	"hmac-sha2-256-etm@openssh.com": {32, true, func(key []byte) hash.Hash {
    54  		return hmac.New(sha256.New, key)
    55  	}},
    56  	"hmac-sha2-512": {64, false, func(key []byte) hash.Hash {
    57  		return hmac.New(sha512.New, key)
    58  	}},
    59  	"hmac-sha2-256": {32, false, func(key []byte) hash.Hash {
    60  		return hmac.New(sha256.New, key)
    61  	}},
    62  	"hmac-sha1": {20, false, func(key []byte) hash.Hash {
    63  		return hmac.New(sha1.New, key)
    64  	}},
    65  	"hmac-sha1-96": {20, false, func(key []byte) hash.Hash {
    66  		return truncatingMAC{12, hmac.New(sha1.New, key)}
    67  	}},
    68  }
    69  

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