github.com/Psiphon-Labs/psiphon-tunnel-core@v2.0.28+incompatible/psiphon/common/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  	"crypto/sha256"
    13  	"hash"
    14  )
    15  
    16  type macMode struct {
    17  	keySize int
    18  	etm     bool
    19  	new     func(key []byte) hash.Hash
    20  }
    21  
    22  // truncatingMAC wraps around a hash.Hash and truncates the output digest to
    23  // a given size.
    24  type truncatingMAC struct {
    25  	length int
    26  	hmac   hash.Hash
    27  }
    28  
    29  func (t truncatingMAC) Write(data []byte) (int, error) {
    30  	return t.hmac.Write(data)
    31  }
    32  
    33  func (t truncatingMAC) Sum(in []byte) []byte {
    34  	out := t.hmac.Sum(in)
    35  	return out[:len(in)+t.length]
    36  }
    37  
    38  func (t truncatingMAC) Reset() {
    39  	t.hmac.Reset()
    40  }
    41  
    42  func (t truncatingMAC) Size() int {
    43  	return t.length
    44  }
    45  
    46  func (t truncatingMAC) BlockSize() int { return t.hmac.BlockSize() }
    47  
    48  var macModes = map[string]*macMode{
    49  	"hmac-sha2-256-etm@openssh.com": {32, true, func(key []byte) hash.Hash {
    50  		return hmac.New(sha256.New, key)
    51  	}},
    52  	"hmac-sha2-256": {32, false, func(key []byte) hash.Hash {
    53  		return hmac.New(sha256.New, key)
    54  	}},
    55  	"hmac-sha1": {20, false, func(key []byte) hash.Hash {
    56  		return hmac.New(sha1.New, key)
    57  	}},
    58  	"hmac-sha1-96": {20, false, func(key []byte) hash.Hash {
    59  		return truncatingMAC{12, hmac.New(sha1.New, key)}
    60  	}},
    61  }