fix: ctx cancellation on login prompt

Signed-off-by: Alano Terblanche <[email protected]>

cli/command/registry.go

@@ -1,10 +1,8 @@
 package command
 
 import (
-	"bufio"
 	"context"
 	"fmt"
-	"io"
 	"os"
 	"runtime"
 	"strings"
@@ -17,7 +15,6 @@ import (
 	"github.com/docker/docker/api/types"
 	registrytypes "github.com/docker/docker/api/types/registry"
 	"github.com/docker/docker/registry"
-	"github.com/moby/term"
 	"github.com/pkg/errors"
 )
 
@@ -43,7 +40,7 @@ func RegistryAuthenticationPrivilegedFunc(cli Cli, index *registrytypes.IndexInf
 		default:
 		}
 
-		err = ConfigureAuth(cli, "", "", &authConfig, isDefaultRegistry)
+		err = ConfigureAuth(ctx, cli, "", "", &authConfig, isDefaultRegistry)
 		if err != nil {
 			return "", err
 		}
@@ -89,7 +86,7 @@ func GetDefaultAuthConfig(cfg *configfile.ConfigFile, checkCredStore bool, serve
 }
 
 // ConfigureAuth handles prompting of user's username and password if needed
-func ConfigureAuth(cli Cli, flUser, flPassword string, authconfig *registrytypes.AuthConfig, isDefaultRegistry bool) error {
+func ConfigureAuth(ctx context.Context, cli Cli, flUser, flPassword string, authconfig *registrytypes.AuthConfig, isDefaultRegistry bool) error {
 	// On Windows, force the use of the regular OS stdin stream.
 	//
 	// See:
@@ -124,9 +121,15 @@ func ConfigureAuth(cli Cli, flUser, flPassword string, authconfig *registrytypes
 				fmt.Fprintln(cli.Out())
 			}
 		}
-		promptWithDefault(cli.Out(), "Username", authconfig.Username)
+
+		var prompt string
+		if authconfig.Username == "" {
+			prompt = "Username: "
+		} else {
+			prompt = fmt.Sprintf("Username (%s): ", authconfig.Username)
+		}
 		var err error
-		flUser, err = readInput(cli.In())
+		flUser, err = PromptForInput(ctx, cli.In(), cli.Out(), prompt)
 		if err != nil {
 			return err
 		}
@@ -138,16 +141,8 @@ func ConfigureAuth(cli Cli, flUser, flPassword string, authconfig *registrytypes
 		return errors.Errorf("Error: Non-null Username Required")
 	}
 	if flPassword == "" {
-		oldState, err := term.SaveState(cli.In().FD())
-		if err != nil {
-			return err
-		}
-		fmt.Fprintf(cli.Out(), "Password: ")
-		_ = term.DisableEcho(cli.In().FD(), oldState)
-		defer func() {
-			_ = term.RestoreTerminal(cli.In().FD(), oldState)
-		}()
-		flPassword, err = readInput(cli.In())
+		var err error
+		flPassword, err = PromptForInput(ctx, cli.In(), cli.Out(), "Password: ", WithHideUserInput(true))
 		if err != nil {
 			return err
 		}
@@ -163,25 +158,6 @@ func ConfigureAuth(cli Cli, flUser, flPassword string, authconfig *registrytypes
 	return nil
 }
 
-// readInput reads, and returns user input from in. It tries to return a
-// single line, not including the end-of-line bytes, and trims leading
-// and trailing whitespace.
-func readInput(in io.Reader) (string, error) {
-	line, _, err := bufio.NewReader(in).ReadLine()
-	if err != nil {
-		return "", errors.Wrap(err, "error while reading input")
-	}
-	return strings.TrimSpace(string(line)), nil
-}
-
-func promptWithDefault(out io.Writer, prompt string, configDefault string) {
-	if configDefault == "" {
-		fmt.Fprintf(out, "%s: ", prompt)
-	} else {
-		fmt.Fprintf(out, "%s (%s): ", prompt, configDefault)
-	}
-}
-
 // RetrieveAuthTokenFromImage retrieves an encoded auth token given a complete
 // image. The auth configuration is serialized as a base64url encoded RFC4648,
 // section 5) JSON string for sending through the X-Registry-Auth header.

cli/command/registry/login.go

@@ -121,7 +121,7 @@ func runLogin(ctx context.Context, dockerCli command.Cli, opts loginOptions) err
 		response, err = loginWithCredStoreCreds(ctx, dockerCli, &authConfig)
 	}
 	if err != nil || authConfig.Username == "" || authConfig.Password == "" {
-		err = command.ConfigureAuth(dockerCli, opts.user, opts.password, &authConfig, isDefaultRegistry)
+		err = command.ConfigureAuth(ctx, dockerCli, opts.user, opts.password, &authConfig, isDefaultRegistry)
 		if err != nil {
 			return err
 		}

cli/command/utils.go

@@ -19,6 +19,7 @@ import (
 	"github.com/docker/docker/api/types/versions"
 	"github.com/docker/docker/errdefs"
 	"github.com/moby/sys/sequential"
+	"github.com/moby/term"
 	"github.com/pkg/errors"
 	"github.com/spf13/pflag"
 )
@@ -76,6 +77,69 @@ func PrettyPrint(i any) string {
 
 var ErrPromptTerminated = errdefs.Cancelled(errors.New("prompt terminated"))
 
+type promptOptions struct {
+	disableEcho bool
+}
+
+type PromptOptions func(*promptOptions)
+
+func WithHideUserInput(t bool) PromptOptions {
+	return func(p *promptOptions) {
+		p.disableEcho = t
+	}
+}
+
+// PromptForInput requests input from the user.
+//
+// If the user terminates the CLI with SIGINT or SIGTERM while the prompt is
+// active, the prompt will return an empty string ("") with an ErrPromptTerminated error.
+// When the prompt returns an error, the caller should propagate the error up
+// the stack and close the io.Reader used for the prompt which will prevent the
+// background goroutine from blocking indefinitely.
+func PromptForInput(ctx context.Context, ins *streams.In, outs *streams.Out, message string, opts ...PromptOptions) (string, error) {
+	options := promptOptions{}
+	for _, o := range opts {
+		o(&options)
+	}
+
+	_, _ = fmt.Fprint(outs, message)
+
+	if options.disableEcho {
+		oldState, err := term.SaveState(ins.FD())
+		if err != nil {
+			return "", err
+		}
+		_ = term.DisableEcho(ins.FD(), oldState)
+		defer func() {
+			_ = term.RestoreTerminal(ins.FD(), oldState)
+		}()
+	}
+
+	// On Windows, force the use of the regular OS stdin stream.
+	if runtime.GOOS == "windows" {
+		ins = streams.NewIn(os.Stdin)
+	}
+
+	result := make(chan string)
+
+	go func() {
+		reader := bufio.NewReader(ins)
+		line, err := reader.ReadString('\n')
+		if err != nil {
+			result <- ""
+		}
+		result <- strings.TrimSpace(line)
+	}()
+
+	select {
+	case <-ctx.Done():
+		_, _ = fmt.Fprintln(outs, "")
+		return "", ErrPromptTerminated
+	case r := <-result:
+		return r, nil
+	}
+}
+
 // PromptForConfirmation requests and checks confirmation from the user.
 // This will display the provided message followed by ' [y/N] '. If the user
 // input 'y' or 'Y' it returns true otherwise false. If no message is provided,