mirror of https://github.com/gohugoio/hugo.git
123 lines
3.3 KiB
Go
123 lines
3.3 KiB
Go
// Copyright 2018 The Hugo Authors. 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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// 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 integrity
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import (
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"crypto/md5"
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"crypto/sha256"
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"crypto/sha512"
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"encoding/base64"
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"encoding/hex"
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"hash"
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"html/template"
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"io"
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"github.com/gohugoio/hugo/resources/internal"
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"github.com/pkg/errors"
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"github.com/gohugoio/hugo/resources"
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"github.com/gohugoio/hugo/resources/resource"
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)
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const defaultHashAlgo = "sha256"
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// Client contains methods to fingerprint (cachebusting) and other integrity-related
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// methods.
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type Client struct {
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rs *resources.Spec
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}
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// New creates a new Client with the given specification.
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func New(rs *resources.Spec) *Client {
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return &Client{rs: rs}
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}
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type fingerprintTransformation struct {
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algo string
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}
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func (t *fingerprintTransformation) Key() internal.ResourceTransformationKey {
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return internal.NewResourceTransformationKey("fingerprint", t.algo)
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}
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// Transform creates a MD5 hash of the Resource content and inserts that hash before
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// the extension in the filename.
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func (t *fingerprintTransformation) Transform(ctx *resources.ResourceTransformationCtx) error {
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h, err := newHash(t.algo)
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if err != nil {
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return err
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}
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var w io.Writer
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if rc, ok := ctx.From.(io.ReadSeeker); ok {
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// This transformation does not change the content, so try to
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// avoid writing to To if we can.
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defer rc.Seek(0, 0)
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w = h
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} else {
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w = io.MultiWriter(h, ctx.To)
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}
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io.Copy(w, ctx.From)
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d, err := digest(h)
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if err != nil {
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return err
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}
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ctx.Data["Integrity"] = integrity(t.algo, d)
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ctx.AddOutPathIdentifier("." + hex.EncodeToString(d[:]))
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return nil
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}
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func newHash(algo string) (hash.Hash, error) {
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switch algo {
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case "md5":
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return md5.New(), nil
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case "sha256":
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return sha256.New(), nil
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case "sha384":
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return sha512.New384(), nil
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case "sha512":
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return sha512.New(), nil
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default:
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return nil, errors.Errorf("unsupported crypto algo: %q, use either md5, sha256, sha384 or sha512", algo)
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}
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}
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// Fingerprint applies fingerprinting of the given resource and hash algorithm.
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// It defaults to sha256 if none given, and the options are md5, sha256 or sha512.
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// The same algo is used for both the fingerprinting part (aka cache busting) and
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// the base64-encoded Subresource Integrity hash, so you will have to stay away from
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// md5 if you plan to use both.
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// See https://developer.mozilla.org/en-US/docs/Web/Security/Subresource_Integrity
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func (c *Client) Fingerprint(res resources.ResourceTransformer, algo string) (resource.Resource, error) {
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if algo == "" {
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algo = defaultHashAlgo
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}
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return res.Transform(&fingerprintTransformation{algo: algo})
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}
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func integrity(algo string, sum []byte) template.HTMLAttr {
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encoded := base64.StdEncoding.EncodeToString(sum)
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return template.HTMLAttr(algo + "-" + encoded)
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}
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func digest(h hash.Hash) ([]byte, error) {
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sum := h.Sum(nil)
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return sum, nil
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}
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