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hash.go
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hash.go
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/*
Copyright 2019 The Kubernetes Authors.
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 hashing
import (
"bytes"
"crypto/md5"
"crypto/sha1"
"crypto/sha256"
"encoding/hex"
"fmt"
"hash"
"io"
"os"
"strings"
"k8s.io/klog/v2"
"k8s.io/kops/pkg/try"
)
type HashAlgorithm string
const (
HashAlgorithmSHA256 HashAlgorithm = "sha256"
HashAlgorithmSHA1 HashAlgorithm = "sha1"
HashAlgorithmMD5 HashAlgorithm = "md5"
)
type Hash struct {
Algorithm HashAlgorithm
HashValue []byte
}
func (h *Hash) String() string {
return string(h.Algorithm) + ":" + h.Hex()
}
func (h *Hash) Hex() string {
return hex.EncodeToString(h.HashValue)
}
func (ha HashAlgorithm) NewHasher() hash.Hash {
switch ha {
case HashAlgorithmMD5:
return md5.New()
case HashAlgorithmSHA1:
return sha1.New()
case HashAlgorithmSHA256:
return sha256.New()
}
klog.Exitf("Unknown hash algorithm: %v", ha)
return nil
}
func (ha HashAlgorithm) FromString(s string) (*Hash, error) {
l := -1
switch ha {
case HashAlgorithmMD5:
l = 32
case HashAlgorithmSHA1:
l = 40
case HashAlgorithmSHA256:
l = 64
default:
return nil, fmt.Errorf("unknown hash algorithm: %q", ha)
}
if len(s) != l {
return nil, fmt.Errorf("invalid %q hash - unexpected length %d", ha, len(s))
}
hashValue, err := hex.DecodeString(s)
if err != nil {
return nil, fmt.Errorf("invalid hash %q - not hex", s)
}
return &Hash{Algorithm: ha, HashValue: hashValue}, nil
}
func FromString(s string) (*Hash, error) {
for _, ha := range []HashAlgorithm{HashAlgorithmMD5, HashAlgorithmSHA1, HashAlgorithmSHA256} {
prefix := fmt.Sprintf("%s:", ha)
if strings.HasPrefix(s, prefix) {
return ha.FromString(s[len(prefix):])
}
}
var ha HashAlgorithm
switch len(s) {
case 32:
ha = HashAlgorithmMD5
case 40:
ha = HashAlgorithmSHA1
case 64:
ha = HashAlgorithmSHA256
default:
return nil, fmt.Errorf("cannot determine algorithm for hash length: %d", len(s))
}
return ha.FromString(s)
}
func (ha HashAlgorithm) Hash(r io.Reader) (*Hash, error) {
hasher := ha.NewHasher()
_, err := copyToHasher(hasher, r)
if err != nil {
return nil, fmt.Errorf("error while hashing resource: %v", err)
}
return &Hash{Algorithm: ha, HashValue: hasher.Sum(nil)}, nil
}
func (ha HashAlgorithm) HashFile(p string) (*Hash, error) {
f, err := os.OpenFile(p, os.O_RDONLY, 0)
if err != nil {
if os.IsNotExist(err) {
return nil, err
}
return nil, fmt.Errorf("error opening file %q: %v", p, err)
}
defer try.CloseFile(f)
return ha.Hash(f)
}
func copyToHasher(dest io.Writer, src io.Reader) (int64, error) {
n, err := io.Copy(dest, src)
if err != nil {
return n, fmt.Errorf("error hashing data: %v", err)
}
return n, nil
}
func (l *Hash) Equal(r *Hash) bool {
return (l.Algorithm == r.Algorithm) && bytes.Equal(l.HashValue, r.HashValue)
}