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// Copyright 2020 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package subtle provides common methods needed in subtle implementations.
package subtle
import (
"crypto/elliptic"
"crypto/sha1"
"crypto/sha256"
"crypto/sha512"
"encoding/hex"
"errors"
"hash"
"math/big"
)
var errNilHashFunc = errors.New("nil hash function")
// hashDigestSize maps hash algorithms to their digest size in bytes.
var hashDigestSize = map[string]uint32{
"SHA1": uint32(20),
"SHA224": uint32(28),
"SHA256": uint32(32),
"SHA384": uint32(48),
"SHA512": uint32(64),
}
// GetHashDigestSize returns the digest size of the specified hash algorithm.
func GetHashDigestSize(hash string) (uint32, error) {
digestSize, ok := hashDigestSize[hash]
if !ok {
return 0, errors.New("invalid hash algorithm")
}
return digestSize, nil
}
// TODO(ckl): Perhaps return an explicit error instead of ""/nil for the
// following functions.
// ConvertHashName converts different forms of a hash name to the
// hash name that tink recognizes.
func ConvertHashName(name string) string {
switch name {
case "SHA-224":
return "SHA224"
case "SHA-256":
return "SHA256"
case "SHA-384":
return "SHA384"
case "SHA-512":
return "SHA512"
case "SHA-1":
return "SHA1"
default:
return ""
}
}
// ConvertCurveName converts different forms of a curve name to the
// name that tink recognizes.
func ConvertCurveName(name string) string {
switch name {
case "secp256r1", "P-256":
return "NIST_P256"
case "secp384r1", "P-384":
return "NIST_P384"
case "secp521r1", "P-521":
return "NIST_P521"
default:
return ""
}
}
// GetHashFunc returns the corresponding hash function of the given hash name.
func GetHashFunc(hash string) func() hash.Hash {
switch hash {
case "SHA1":
return sha1.New
case "SHA224":
return sha256.New224
case "SHA256":
return sha256.New
case "SHA384":
return sha512.New384
case "SHA512":
return sha512.New
default:
return nil
}
}
// GetCurve returns the curve object that corresponds to the given curve type.
// It returns null if the curve type is not supported.
func GetCurve(curve string) elliptic.Curve {
switch curve {
case "NIST_P256":
return elliptic.P256()
case "NIST_P384":
return elliptic.P384()
case "NIST_P521":
return elliptic.P521()
default:
return nil
}
}
// ComputeHash calculates a hash of the given data using the given hash function.
func ComputeHash(hashFunc func() hash.Hash, data []byte) ([]byte, error) {
if hashFunc == nil {
return nil, errNilHashFunc
}
h := hashFunc()
h.Write(data)
return h.Sum(nil), nil
}
// NewBigIntFromHex returns a big integer from a hex string.
func NewBigIntFromHex(s string) (*big.Int, error) {
if len(s)%2 == 1 {
s = "0" + s
}
b, err := hex.DecodeString(s)
if err != nil {
return nil, err
}
ret := new(big.Int).SetBytes(b)
return ret, nil
}
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