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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/fips140"
"crypto/hmac"
"crypto/sha1"
"crypto/sha256"
"crypto/sha512"
"hash"
"slices"
)
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() }
// macModes defines the supported MACs. MACs not included are not supported
// and will not be negotiated, even if explicitly configured. When FIPS mode is
// enabled, only FIPS-approved algorithms are included.
var macModes = map[string]*macMode{}
func init() {
macModes[HMACSHA512ETM] = &macMode{64, true, func(key []byte) hash.Hash {
return hmac.New(sha512.New, key)
}}
macModes[HMACSHA256ETM] = &macMode{32, true, func(key []byte) hash.Hash {
return hmac.New(sha256.New, key)
}}
macModes[HMACSHA512] = &macMode{64, false, func(key []byte) hash.Hash {
return hmac.New(sha512.New, key)
}}
macModes[HMACSHA256] = &macMode{32, false, func(key []byte) hash.Hash {
return hmac.New(sha256.New, key)
}}
if fips140.Enabled() {
defaultMACs = slices.DeleteFunc(defaultMACs, func(algo string) bool {
_, ok := macModes[algo]
return !ok
})
return
}
macModes[HMACSHA1] = &macMode{20, false, func(key []byte) hash.Hash {
return hmac.New(sha1.New, key)
}}
macModes[InsecureHMACSHA196] = &macMode{20, false, func(key []byte) hash.Hash {
return truncatingMAC{12, hmac.New(sha1.New, key)}
}}
}
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