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crypto/tls: drop macFunction abstraction

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Since we dropped SSLv3, there is only one MAC scheme, and it doesn't
need any state beyond a keyed HMAC, so we can replace the macFunction
with the hash.Hash it wraps.

Pointed out by mtp@.

Change-Id: I5545be0e6ccb34a3055fad7f6cb5f628ff748e9f
Reviewed-on: https://go-review.googlesource.com/c/go/+/251859
Run-TryBot: Filippo Valsorda <filippo@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Roland Shoemaker <roland@golang.org>
Trust: Roland Shoemaker <roland@golang.org>
Trust: Filippo Valsorda <filippo@golang.org>
This commit is contained in:
Filippo Valsorda 2020-08-31 17:09:57 -04:00
parent 3b66a0b37e
commit 74ff83e750
4 changed files with 45 additions and 66 deletions
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51
cipher_suites.go
View file

@ -160,7 +160,7 @@ type cipherSuite struct {
// flags is a bitmask of the suite* values, above.
flags int
cipher func(key, iv []byte, isRead bool) interface{}
mac func(version uint16, macKey []byte) macFunction
mac func(key []byte) hash.Hash
aead func(key, fixedNonce []byte) aead
}
@ -247,24 +247,15 @@ func cipherAES(key, iv []byte, isRead bool) interface{} {
return cipher.NewCBCEncrypter(block, iv)
}
// macSHA1 returns a macFunction for the given protocol version.
func macSHA1(version uint16, key []byte) macFunction {
return tls10MAC{h: hmac.New(newConstantTimeHash(sha1.New), key)}
// macSHA1 returns a SHA-1 based constant time MAC.
func macSHA1(key []byte) hash.Hash {
return hmac.New(newConstantTimeHash(sha1.New), key)
}
// macSHA256 returns a SHA-256 based MAC. These are only supported in TLS 1.2
// so the given version is ignored.
func macSHA256(version uint16, key []byte) macFunction {
return tls10MAC{h: hmac.New(sha256.New, key)}
}
type macFunction interface {
// Size returns the length of the MAC.
Size() int
// MAC appends the MAC of (seq, header, data) to out. The extra data is fed
// into the MAC after obtaining the result to normalize timing. The result
// is only valid until the next invocation of MAC as the buffer is reused.
MAC(seq, header, data, extra []byte) []byte
// macSHA256 returns a SHA-256 based MAC. This is only supported in TLS 1.2 and
// is currently only used in disabled-by-default cipher suites.
func macSHA256(key []byte) hash.Hash {
return hmac.New(sha256.New, key)
}
type aead interface {
@ -412,26 +403,14 @@ func newConstantTimeHash(h func() hash.Hash) func() hash.Hash {
}
// tls10MAC implements the TLS 1.0 MAC function. RFC 2246, Section 6.2.3.
type tls10MAC struct {
h hash.Hash
buf []byte
}
func (s tls10MAC) Size() int {
return s.h.Size()
}
// MAC is guaranteed to take constant time, as long as
// len(seq)+len(header)+len(data)+len(extra) is constant. extra is not fed into
// the MAC, but is only provided to make the timing profile constant.
func (s tls10MAC) MAC(seq, header, data, extra []byte) []byte {
s.h.Reset()
s.h.Write(seq)
s.h.Write(header)
s.h.Write(data)
res := s.h.Sum(s.buf[:0])
func tls10MAC(h hash.Hash, out, seq, header, data, extra []byte) []byte {
h.Reset()
h.Write(seq)
h.Write(header)
h.Write(data)
res := h.Sum(out)
if extra != nil {
s.h.Write(extra)
h.Write(extra)
}
return res
}