feat: notation plugin install command

cmd/notation/internal/plugin/plugin.go

@@ -0,0 +1,85 @@
+// Copyright The Notary Project 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 plugin
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"net/http"
+	"time"
+
+	"github.com/notaryproject/notation/internal/httputil"
+)
+
+// MaxPluginSourceBytes specifies the limit on how many bytes are allowed in the
+// server's response to the download from URL request.
+//
+// The plugin source size must be strictly less than this value.
+var MaxPluginSourceBytes int64 = 256 * 1024 * 1024 // 256 MiB
+
+// PluginSourceType is an enum for plugin source
+type PluginSourceType int
+
+const (
+	// PluginSourceTypeFile means plugin source is file
+	PluginSourceTypeFile PluginSourceType = 1 + iota
+
+	// PluginSourceTypeURL means plugin source is URL
+	PluginSourceTypeURL
+)
+
+const (
+	// MediaTypeZip means plugin file is zip
+	MediaTypeZip = "application/zip"
+
+	// MediaTypeGzip means plugin file is gzip
+	MediaTypeGzip = "application/x-gzip"
+)
+
+// DownloadPluginFromURLTimeout is the timeout when downloading plugin from a
+// URL
+const DownloadPluginFromURLTimeout = 10 * time.Minute
+
+// DownloadPluginFromURL downloads plugin file from url to a tmp directory
+func DownloadPluginFromURL(ctx context.Context, pluginURL string, tmpFile io.Writer) error {
+	// Get the data
+	client := httputil.NewAuthClient(ctx, &http.Client{Timeout: DownloadPluginFromURLTimeout})
+	req, err := http.NewRequest(http.MethodGet, pluginURL, nil)
+	if err != nil {
+		return err
+	}
+	resp, err := client.Do(req)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+	// Check server response
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("%s %q: https response bad status: %s", resp.Request.Method, resp.Request.URL, resp.Status)
+	}
+	// Write the body to file
+	lr := &io.LimitedReader{
+		R: resp.Body,
+		N: MaxPluginSourceBytes,
+	}
+	_, err = io.Copy(tmpFile, lr)
+	if err != nil {
+		return err
+	}
+	if lr.N == 0 {
+		return fmt.Errorf("%s %q: https response reaches the %d MiB size limit", resp.Request.Method, resp.Request.URL, MaxPluginSourceBytes)
+	}
+	return nil
+}

cmd/notation/plugin/cmd.go

@@ -23,6 +23,7 @@ func Cmd() *cobra.Command {
 
 	command.AddCommand(
 		listCommand(),
+		installCommand(nil),
 		uninstallCommand(nil),
 	)