Introduce .zip import for docker context

Adds capabilities to import a .zip file with importZip.
Detects the content type of source by checking bytes & DetectContentType.
Adds LimitedReader reader, a fork of io.LimitedReader,
was needed for better error messaging instead of just getting back EOF.
We are using limited reader to avoid very big files causing memory issues.
Adds a new file size limit for context imports,
this limit is used for the main file for .zip & .tar and individual compressed
files for .zip.
Added TestImportZip that will check the import content type
Then will assert no err on Importing .zip file

Signed-off-by: Goksu Toprak <goksu.toprak@docker.com>

cli/command/context/import.go

@@ -14,7 +14,7 @@ import (
 func newImportCommand(dockerCli command.Cli) *cobra.Command {
 	cmd := &cobra.Command{
 		Use:   "import CONTEXT FILE|-",
-		Short: "Import a context from a tar file",
+		Short: "Import a context from a tar or zip file",
 		Args:  cli.ExactArgs(2),
 		RunE: func(cmd *cobra.Command, args []string) error {
 			return RunImport(dockerCli, args[0], args[1])
@@ -28,6 +28,7 @@ func RunImport(dockerCli command.Cli, name string, source string) error {
 	if err := checkContextNameForCreation(dockerCli.ContextStore(), name); err != nil {
 		return err
 	}
+
 	var reader io.Reader
 	if source == "-" {
 		reader = dockerCli.In()
@@ -43,6 +44,7 @@ func RunImport(dockerCli command.Cli, name string, source string) error {
 	if err := store.Import(name, dockerCli.ContextStore(), reader); err != nil {
 		return err
 	}
+
 	fmt.Fprintln(dockerCli.Out(), name)
 	fmt.Fprintf(dockerCli.Err(), "Successfully imported context %q\n", name)
 	return nil

cli/context/store/io_utils.go

@@ -0,0 +1,29 @@
+package store
+
+import (
+	"errors"
+	"io"
+)
+
+// LimitedReader is a fork of io.LimitedReader to override Read.
+type LimitedReader struct {
+	R io.Reader
+	N int64 // max bytes remaining
+}
+
+// Read is a fork of io.LimitedReader.Read that returns an error when limit exceeded.
+func (l *LimitedReader) Read(p []byte) (n int, err error) {
+	if l.N < 0 {
+		return 0, errors.New("read exceeds the defined limit")
+	}
+	if l.N == 0 {
+		return 0, io.EOF
+	}
+	// have to cap N + 1 otherwise we won't hit limit err
+	if int64(len(p)) > l.N+1 {
+		p = p[0 : l.N+1]
+	}
+	n, err = l.R.Read(p)
+	l.N -= int64(n)
+	return n, err
+}

cli/context/store/io_utils_test.go

@@ -0,0 +1,24 @@
+package store
+
+import (
+	"io/ioutil"
+	"strings"
+	"testing"
+
+	"gotest.tools/assert"
+)
+
+func TestLimitReaderReadAll(t *testing.T) {
+	r := strings.NewReader("Reader")
+
+	_, err := ioutil.ReadAll(r)
+	assert.NilError(t, err)
+
+	r = strings.NewReader("Test")
+	_, err = ioutil.ReadAll(&LimitedReader{R: r, N: 4})
+	assert.NilError(t, err)
+
+	r = strings.NewReader("Test")
+	_, err = ioutil.ReadAll(&LimitedReader{R: r, N: 2})
+	assert.Error(t, err, "read exceeds the defined limit")
+}

cli/context/store/store.go

@@ -2,12 +2,16 @@ package store
 
 import (
 	"archive/tar"
+	"archive/zip"
+	"bufio"
+	"bytes"
 	_ "crypto/sha256" // ensure ids can be computed
 	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
 	"io/ioutil"
+	"net/http"
 	"path"
 	"path/filepath"
 	"strings"
@@ -259,12 +263,44 @@ func Export(name string, s Reader) io.ReadCloser {
 	return reader
 }
 
+const (
+	maxAllowedFileSizeToImport int64  = 10 << 20
+	zipType                    string = "application/zip"
+)
+
+func getImportContentType(r *bufio.Reader) (string, error) {
+	head, err := r.Peek(512)
+	if err != nil && err != io.EOF {
+		return "", err
+	}
+
+	return http.DetectContentType(head), nil
+}
+
 // Import imports an exported context into a store
 func Import(name string, s Writer, reader io.Reader) error {
-	tr := tar.NewReader(reader)
+	// Buffered reader will not advance the buffer, needed to determine content type
+	r := bufio.NewReader(reader)
+
+	importContentType, err := getImportContentType(r)
+	if err != nil {
+		return err
+	}
+	switch importContentType {
+	case zipType:
+		return importZip(name, s, r)
+	default:
+		// Assume it's a TAR (TAR does not have a "magic number")
+		return importTar(name, s, r)
+	}
+}
+
+func importTar(name string, s Writer, reader io.Reader) error {
+	tr := tar.NewReader(&LimitedReader{R: reader, N: maxAllowedFileSizeToImport})
 	tlsData := ContextTLSData{
 		Endpoints: map[string]EndpointTLSData{},
 	}
+
 	for {
 		hdr, err := tr.Next()
 		if err == io.EOF {
@@ -282,37 +318,112 @@ func Import(name string, s Writer, reader io.Reader) error {
 			if err != nil {
 				return err
 			}
-			var meta Metadata
-			if err := json.Unmarshal(data, &meta); err != nil {
+			meta, err := parseMetadata(data, name)
+			if err != nil {
 				return err
 			}
-			meta.Name = name
 			if err := s.CreateOrUpdate(meta); err != nil {
 				return err
 			}
 		} else if strings.HasPrefix(hdr.Name, "tls/") {
-			relative := strings.TrimPrefix(hdr.Name, "tls/")
-			parts := strings.SplitN(relative, "/", 2)
-			if len(parts) != 2 {
-				return errors.New("archive format is invalid")
-			}
-			endpointName := parts[0]
-			fileName := parts[1]
 			data, err := ioutil.ReadAll(tr)
 			if err != nil {
 				return err
 			}
-			if _, ok := tlsData.Endpoints[endpointName]; !ok {
-				tlsData.Endpoints[endpointName] = EndpointTLSData{
-					Files: map[string][]byte{},
-				}
+			if err := importEndpointTLS(&tlsData, hdr.Name, data); err != nil {
+				return err
 			}
-			tlsData.Endpoints[endpointName].Files[fileName] = data
 		}
 	}
+
 	return s.ResetTLSMaterial(name, &tlsData)
 }
 
+func importZip(name string, s Writer, reader io.Reader) error {
+	body, err := ioutil.ReadAll(&LimitedReader{R: reader, N: maxAllowedFileSizeToImport})
+	if err != nil {
+		return err
+	}
+	zr, err := zip.NewReader(bytes.NewReader(body), int64(len(body)))
+	if err != nil {
+		return err
+	}
+	tlsData := ContextTLSData{
+		Endpoints: map[string]EndpointTLSData{},
+	}
+
+	for _, zf := range zr.File {
+		fi := zf.FileInfo()
+		if fi.IsDir() {
+			// skip this entry, only taking files into account
+			continue
+		}
+		if zf.Name == metaFile {
+			f, err := zf.Open()
+			if err != nil {
+				return err
+			}
+
+			data, err := ioutil.ReadAll(&LimitedReader{R: f, N: maxAllowedFileSizeToImport})
+			defer f.Close()
+			if err != nil {
+				return err
+			}
+			meta, err := parseMetadata(data, name)
+			if err != nil {
+				return err
+			}
+			if err := s.CreateOrUpdate(meta); err != nil {
+				return err
+			}
+		} else if strings.HasPrefix(zf.Name, "tls/") {
+			f, err := zf.Open()
+			if err != nil {
+				return err
+			}
+			data, err := ioutil.ReadAll(f)
+			defer f.Close()
+			if err != nil {
+				return err
+			}
+			err = importEndpointTLS(&tlsData, zf.Name, data)
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	return s.ResetTLSMaterial(name, &tlsData)
+}
+
+func parseMetadata(data []byte, name string) (Metadata, error) {
+	var meta Metadata
+	if err := json.Unmarshal(data, &meta); err != nil {
+		return meta, err
+	}
+	meta.Name = name
+	return meta, nil
+}
+
+func importEndpointTLS(tlsData *ContextTLSData, path string, data []byte) error {
+	parts := strings.SplitN(strings.TrimPrefix(path, "tls/"), "/", 2)
+	if len(parts) != 2 {
+		// TLS endpoints require archived file directory with 2 layers
+		// i.e. tls/{endpointName}/{fileName}
+		return errors.New("archive format is invalid")
+	}
+
+	epName := parts[0]
+	fileName := parts[1]
+	if _, ok := tlsData.Endpoints[epName]; !ok {
+		tlsData.Endpoints[epName] = EndpointTLSData{
+			Files: map[string][]byte{},
+		}
+	}
+	tlsData.Endpoints[epName].Files[fileName] = data
+	return nil
+}
+
 type setContextName interface {
 	setContext(name string)
 }

cli/context/store/store_test.go

@@ -1,9 +1,15 @@
 package store
 
 import (
+	"archive/zip"
+	"bufio"
+	"bytes"
 	"crypto/rand"
+	"encoding/json"
+	"io"
 	"io/ioutil"
 	"os"
+	"path"
 	"testing"
 
 	"gotest.tools/assert"
@@ -125,3 +131,66 @@ func TestErrHasCorrectContext(t *testing.T) {
 	assert.ErrorContains(t, err, "no-exists")
 	assert.Check(t, IsErrContextDoesNotExist(err))
 }
+
+func TestDetectImportContentType(t *testing.T) {
+	testDir, err := ioutil.TempDir("", t.Name())
+	assert.NilError(t, err)
+	defer os.RemoveAll(testDir)
+
+	buf := new(bytes.Buffer)
+	r := bufio.NewReader(buf)
+	ct, err := getImportContentType(r)
+	assert.NilError(t, err)
+	assert.Assert(t, zipType != ct)
+}
+
+func TestImportZip(t *testing.T) {
+	testDir, err := ioutil.TempDir("", t.Name())
+	assert.NilError(t, err)
+	defer os.RemoveAll(testDir)
+
+	zf := path.Join(testDir, "test.zip")
+
+	f, err := os.Create(zf)
+	defer f.Close()
+	assert.NilError(t, err)
+	w := zip.NewWriter(f)
+
+	meta, err := json.Marshal(Metadata{
+		Endpoints: map[string]interface{}{
+			"ep1": endpoint{Foo: "bar"},
+		},
+		Metadata: context{Bar: "baz"},
+		Name:     "source",
+	})
+	assert.NilError(t, err)
+	var files = []struct {
+		Name, Body string
+	}{
+		{"meta.json", string(meta)},
+		{path.Join("tls", "docker", "ca.pem"), string([]byte("ca.pem"))},
+	}
+
+	for _, file := range files {
+		f, err := w.Create(file.Name)
+		assert.NilError(t, err)
+		_, err = f.Write([]byte(file.Body))
+		assert.NilError(t, err)
+	}
+
+	err = w.Close()
+	assert.NilError(t, err)
+
+	source, err := os.Open(zf)
+	assert.NilError(t, err)
+	ct, err := getImportContentType(bufio.NewReader(source))
+	assert.NilError(t, err)
+	assert.Equal(t, zipType, ct)
+
+	source, _ = os.Open(zf)
+	defer source.Close()
+	var r io.Reader = source
+	s := New(testDir, testCfg)
+	err = Import("zipTest", s, r)
+	assert.NilError(t, err)
+}