Add Chef package registry (#22554)

This PR implements a [Chef registry](https://chef.io/) to manage
cookbooks. This package type was a bit complicated because Chef uses RSA
signed requests as authentication with the registry.


![grafik](https://user-images.githubusercontent.com/1666336/213747995-46819fd8-c3d6-45a2-afd4-a4c3c8505a4a.png)


![grafik](https://user-images.githubusercontent.com/1666336/213748145-d01c9e81-d4dd-41e3-a3cc-8241862c3166.png)

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

modules/packages/chef/metadata.go

@@ -0,0 +1,134 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package chef
+
+import (
+	"archive/tar"
+	"compress/gzip"
+	"io"
+	"regexp"
+	"strings"
+
+	"code.gitea.io/gitea/modules/json"
+	"code.gitea.io/gitea/modules/util"
+	"code.gitea.io/gitea/modules/validation"
+)
+
+const (
+	KeyBits          = 4096
+	SettingPublicPem = "chef.public_pem"
+)
+
+var (
+	ErrMissingMetadataFile = util.NewInvalidArgumentErrorf("metadata.json file is missing")
+	ErrInvalidName         = util.NewInvalidArgumentErrorf("package name is invalid")
+	ErrInvalidVersion      = util.NewInvalidArgumentErrorf("package version is invalid")
+
+	namePattern    = regexp.MustCompile(`\A\S+\z`)
+	versionPattern = regexp.MustCompile(`\A\d+\.\d+(?:\.\d+)?\z`)
+)
+
+// Package represents a Chef package
+type Package struct {
+	Name     string
+	Version  string
+	Metadata *Metadata
+}
+
+// Metadata represents the metadata of a Chef package
+type Metadata struct {
+	Description     string            `json:"description,omitempty"`
+	LongDescription string            `json:"long_description,omitempty"`
+	Author          string            `json:"author,omitempty"`
+	License         string            `json:"license,omitempty"`
+	RepositoryURL   string            `json:"repository_url,omitempty"`
+	Dependencies    map[string]string `json:"dependencies,omitempty"`
+}
+
+type chefMetadata struct {
+	Name               string            `json:"name"`
+	Description        string            `json:"description"`
+	LongDescription    string            `json:"long_description"`
+	Maintainer         string            `json:"maintainer"`
+	MaintainerEmail    string            `json:"maintainer_email"`
+	License            string            `json:"license"`
+	Platforms          map[string]string `json:"platforms"`
+	Dependencies       map[string]string `json:"dependencies"`
+	Providing          map[string]string `json:"providing"`
+	Recipes            map[string]string `json:"recipes"`
+	Version            string            `json:"version"`
+	SourceURL          string            `json:"source_url"`
+	IssuesURL          string            `json:"issues_url"`
+	Privacy            bool              `json:"privacy"`
+	ChefVersions       [][]string        `json:"chef_versions"`
+	Gems               [][]string        `json:"gems"`
+	EagerLoadLibraries bool              `json:"eager_load_libraries"`
+}
+
+// ParsePackage parses the Chef package file
+func ParsePackage(r io.Reader) (*Package, error) {
+	gzr, err := gzip.NewReader(r)
+	if err != nil {
+		return nil, err
+	}
+	defer gzr.Close()
+
+	tr := tar.NewReader(gzr)
+	for {
+		hd, err := tr.Next()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			return nil, err
+		}
+
+		if hd.Typeflag != tar.TypeReg {
+			continue
+		}
+
+		if strings.Count(hd.Name, "/") != 1 {
+			continue
+		}
+
+		if hd.FileInfo().Name() == "metadata.json" {
+			return ParseChefMetadata(tr)
+		}
+	}
+
+	return nil, ErrMissingMetadataFile
+}
+
+// ParseChefMetadata parses a metadata.json file to retrieve the metadata of a Chef package
+func ParseChefMetadata(r io.Reader) (*Package, error) {
+	var cm chefMetadata
+	if err := json.NewDecoder(r).Decode(&cm); err != nil {
+		return nil, err
+	}
+
+	if !namePattern.MatchString(cm.Name) {
+		return nil, ErrInvalidName
+	}
+
+	if !versionPattern.MatchString(cm.Version) {
+		return nil, ErrInvalidVersion
+	}
+
+	if !validation.IsValidURL(cm.SourceURL) {
+		cm.SourceURL = ""
+	}
+
+	return &Package{
+		Name:    cm.Name,
+		Version: cm.Version,
+		Metadata: &Metadata{
+			Description:     cm.Description,
+			LongDescription: cm.LongDescription,
+			Author:          cm.Maintainer,
+			License:         cm.License,
+			RepositoryURL:   cm.SourceURL,
+			Dependencies:    cm.Dependencies,
+		},
+	}, nil
+}