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hash.go
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hash.go
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// Copyright 2017 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 algorithm
import (
"crypto"
"fmt"
"hash"
)
// Hash is an official hash function algorithm. See RFC 4880, section 9.4.
type Hash interface {
// Id returns the algorithm ID, as a byte, of Hash.
Id() uint8
// Available reports whether the given hash function is linked into the binary.
Available() bool
// HashFunc simply returns the value of h so that Hash implements SignerOpts.
HashFunc() crypto.Hash
// New returns a new hash.Hash calculating the given hash function. New
// panics if the hash function is not linked into the binary.
New() hash.Hash
// Size returns the length, in bytes, of a digest resulting from the given
// hash function. It doesn't require that the hash function in question be
// linked into the program.
Size() int
// String is the name of the hash function corresponding to the given
// OpenPGP hash id.
String() string
}
// The following vars mirror the crypto/Hash supported hash functions.
var (
SHA1 Hash = cryptoHash{2, crypto.SHA1}
SHA256 Hash = cryptoHash{8, crypto.SHA256}
SHA384 Hash = cryptoHash{9, crypto.SHA384}
SHA512 Hash = cryptoHash{10, crypto.SHA512}
SHA224 Hash = cryptoHash{11, crypto.SHA224}
SHA3_256 Hash = cryptoHash{12, crypto.SHA3_256}
SHA3_512 Hash = cryptoHash{14, crypto.SHA3_512}
)
// HashById represents the different hash functions specified for OpenPGP. See
// http://www.iana.org/assignments/pgp-parameters/pgp-parameters.xhtml#pgp-parameters-14
var (
HashById = map[uint8]Hash{
SHA256.Id(): SHA256,
SHA384.Id(): SHA384,
SHA512.Id(): SHA512,
SHA224.Id(): SHA224,
SHA3_256.Id(): SHA3_256,
SHA3_512.Id(): SHA3_512,
}
)
// cryptoHash contains pairs relating OpenPGP's hash identifier with
// Go's crypto.Hash type. See RFC 4880, section 9.4.
type cryptoHash struct {
id uint8
crypto.Hash
}
// Id returns the algorithm ID, as a byte, of cryptoHash.
func (h cryptoHash) Id() uint8 {
return h.id
}
var hashNames = map[uint8]string{
SHA256.Id(): "SHA256",
SHA384.Id(): "SHA384",
SHA512.Id(): "SHA512",
SHA224.Id(): "SHA224",
SHA3_256.Id(): "SHA3-256",
SHA3_512.Id(): "SHA3-512",
}
func (h cryptoHash) String() string {
s, ok := hashNames[h.id]
if !ok {
panic(fmt.Sprintf("Unsupported hash function %d", h.id))
}
return s
}
// HashIdToHash returns a crypto.Hash which corresponds to the given OpenPGP
// hash id.
func HashIdToHash(id byte) (h crypto.Hash, ok bool) {
if hash, ok := HashById[id]; ok {
return hash.HashFunc(), true
}
return 0, false
}
// HashIdToHashWithSha1 returns a crypto.Hash which corresponds to the given OpenPGP
// hash id, allowing sha1.
func HashIdToHashWithSha1(id byte) (h crypto.Hash, ok bool) {
if hash, ok := HashById[id]; ok {
return hash.HashFunc(), true
}
if id == SHA1.Id() {
return SHA1.HashFunc(), true
}
return 0, false
}
// HashIdToString returns the name of the hash function corresponding to the
// given OpenPGP hash id.
func HashIdToString(id byte) (name string, ok bool) {
if hash, ok := HashById[id]; ok {
return hash.String(), true
}
return "", false
}
// HashToHashId returns an OpenPGP hash id which corresponds the given Hash.
func HashToHashId(h crypto.Hash) (id byte, ok bool) {
for id, hash := range HashById {
if hash.HashFunc() == h {
return id, true
}
}
return 0, false
}
// HashToHashIdWithSha1 returns an OpenPGP hash id which corresponds the given Hash,
// allowing instances of SHA1
func HashToHashIdWithSha1(h crypto.Hash) (id byte, ok bool) {
for id, hash := range HashById {
if hash.HashFunc() == h {
return id, true
}
}
if h == SHA1.HashFunc() {
return SHA1.Id(), true
}
return 0, false
}