print a big warning about cleartext passwords

Signed-off-by: Tycho Andersen <tycho@docker.com>

cli/command/registry/login.go

@@ -17,6 +17,11 @@ import (
 	"github.com/spf13/cobra"
 )
 
+const unencryptedWarning = `WARNING! Your password will be stored unencrypted in %s.
+Configure a credential helper to remove this warning. See
+https://docs.docker.com/engine/reference/commandline/login/#credentials-store
+`
+
 type loginOptions struct {
 	serverAddress string
 	user          string
@@ -50,6 +55,29 @@ func NewLoginCommand(dockerCli command.Cli) *cobra.Command {
 	return cmd
 }
 
+// unencryptedPrompt prompts the user to find out whether they want to continue
+// with insecure credential storage. If stdin is not a terminal, we assume they
+// want it (sadly), because people may have been scripting insecure logins and
+// we don't want to break them. Maybe they'll see the warning in their logs and
+// fix things.
+func unencryptedPrompt(dockerCli command.Streams, filename string) error {
+	fmt.Fprintln(dockerCli.Err(), fmt.Sprintf(unencryptedWarning, filename))
+
+	if dockerCli.In().IsTerminal() {
+		if command.PromptForConfirmation(dockerCli.In(), dockerCli.Out(), "") {
+			return nil
+		}
+		return errors.Errorf("User refused unencrypted credentials storage.")
+	}
+
+	return nil
+}
+
+type isFileStore interface {
+	IsFileStore() bool
+	GetFilename() string
+}
+
 func verifyloginOptions(dockerCli command.Cli, opts *loginOptions) error {
 	if opts.password != "" {
 		fmt.Fprintln(dockerCli.Err(), "WARNING! Using --password via the CLI is insecure. Use --password-stdin.")
@@ -74,7 +102,7 @@ func verifyloginOptions(dockerCli command.Cli, opts *loginOptions) error {
 	return nil
 }
 
-func runLogin(dockerCli command.Cli, opts loginOptions) error {
+func runLogin(dockerCli command.Cli, opts loginOptions) error { //nolint: gocyclo
 	ctx := context.Background()
 	clnt := dockerCli.Client()
 	if err := verifyloginOptions(dockerCli, &opts); err != nil {
@@ -113,7 +141,18 @@ func runLogin(dockerCli command.Cli, opts loginOptions) error {
 		authConfig.Password = ""
 		authConfig.IdentityToken = response.IdentityToken
 	}
-	if err := dockerCli.ConfigFile().GetCredentialsStore(serverAddress).Store(*authConfig); err != nil {
+
+	creds := dockerCli.ConfigFile().GetCredentialsStore(serverAddress)
+
+	store, isDefault := creds.(isFileStore)
+	if isDefault {
+		err = unencryptedPrompt(dockerCli, store.GetFilename())
+		if err != nil {
+			return err
+		}
+	}
+
+	if err := creds.Store(*authConfig); err != nil {
 		return errors.Errorf("Error saving credentials: %v", err)
 	}
 

cli/config/configfile/file.go

@@ -307,3 +307,8 @@ func (configFile *ConfigFile) GetAllCredentials() (map[string]types.AuthConfig,
 	}
 	return auths, nil
 }
+
+// GetFilename returns the file name that this config file is based on.
+func (configFile *ConfigFile) GetFilename() string {
+	return configFile.Filename
+}

cli/config/credentials/file_store.go

@@ -8,6 +8,7 @@ import (
 type store interface {
 	Save() error
 	GetAuthConfigs() map[string]types.AuthConfig
+	GetFilename() string
 }
 
 // fileStore implements a credentials store using
@@ -53,3 +54,11 @@ func (c *fileStore) Store(authConfig types.AuthConfig) error {
 	c.file.GetAuthConfigs()[authConfig.ServerAddress] = authConfig
 	return c.file.Save()
 }
+
+func (c *fileStore) GetFilename() string {
+	return c.file.GetFilename()
+}
+
+func (c *fileStore) IsFileStore() bool {
+	return true
+}

cli/config/credentials/file_store_test.go

@@ -20,6 +20,10 @@ func (f *fakeStore) GetAuthConfigs() map[string]types.AuthConfig {
 	return f.configs
 }
 
+func (f *fakeStore) GetFilename() string {
+	return "/tmp/docker-fakestore"
+}
+
 func newStore(auths map[string]types.AuthConfig) store {
 	return &fakeStore{configs: auths}
 }