mirror of https://github.com/containers/podman.git
124 lines
3.2 KiB
Go
124 lines
3.2 KiB
Go
// Copyright 2018 Google LLC All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package v1
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import (
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"crypto"
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"encoding/hex"
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"encoding/json"
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"fmt"
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"hash"
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"io"
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"strconv"
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"strings"
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)
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// Hash is an unqualified digest of some content, e.g. sha256:deadbeef
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type Hash struct {
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// Algorithm holds the algorithm used to compute the hash.
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Algorithm string
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// Hex holds the hex portion of the content hash.
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Hex string
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}
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// String reverses NewHash returning the string-form of the hash.
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func (h Hash) String() string {
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return fmt.Sprintf("%s:%s", h.Algorithm, h.Hex)
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}
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// NewHash validates the input string is a hash and returns a strongly type Hash object.
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func NewHash(s string) (Hash, error) {
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h := Hash{}
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if err := h.parse(s); err != nil {
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return Hash{}, err
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}
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return h, nil
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}
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// MarshalJSON implements json.Marshaler
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func (h Hash) MarshalJSON() ([]byte, error) {
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return json.Marshal(h.String())
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}
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// UnmarshalJSON implements json.Unmarshaler
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func (h *Hash) UnmarshalJSON(data []byte) error {
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s, err := strconv.Unquote(string(data))
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if err != nil {
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return err
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}
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return h.parse(s)
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}
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// MarshalText implements encoding.TextMarshaler. This is required to use
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// v1.Hash as a key in a map when marshalling JSON.
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func (h Hash) MarshalText() (text []byte, err error) {
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return []byte(h.String()), nil
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}
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// UnmarshalText implements encoding.TextUnmarshaler. This is required to use
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// v1.Hash as a key in a map when unmarshalling JSON.
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func (h *Hash) UnmarshalText(text []byte) error {
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return h.parse(string(text))
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}
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// Hasher returns a hash.Hash for the named algorithm (e.g. "sha256")
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func Hasher(name string) (hash.Hash, error) {
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switch name {
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case "sha256":
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return crypto.SHA256.New(), nil
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default:
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return nil, fmt.Errorf("unsupported hash: %q", name)
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}
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}
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func (h *Hash) parse(unquoted string) error {
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parts := strings.Split(unquoted, ":")
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if len(parts) != 2 {
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return fmt.Errorf("cannot parse hash: %q", unquoted)
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}
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rest := strings.TrimLeft(parts[1], "0123456789abcdef")
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if len(rest) != 0 {
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return fmt.Errorf("found non-hex character in hash: %c", rest[0])
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}
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hasher, err := Hasher(parts[0])
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if err != nil {
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return err
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}
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// Compare the hex to the expected size (2 hex characters per byte)
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if len(parts[1]) != hasher.Size()*2 {
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return fmt.Errorf("wrong number of hex digits for %s: %s", parts[0], parts[1])
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}
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h.Algorithm = parts[0]
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h.Hex = parts[1]
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return nil
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}
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// SHA256 computes the Hash of the provided io.Reader's content.
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func SHA256(r io.Reader) (Hash, int64, error) {
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hasher := crypto.SHA256.New()
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n, err := io.Copy(hasher, r)
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if err != nil {
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return Hash{}, 0, err
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}
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return Hash{
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Algorithm: "sha256",
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Hex: hex.EncodeToString(hasher.Sum(make([]byte, 0, hasher.Size()))),
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}, n, nil
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}
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