Login & authentication rework, part 2: prompt cleanup

pkg/cmd/login/login.go

@@ -17,18 +17,14 @@
 package login
 
 import (
-	"bufio"
 	"context"
 	"errors"
 	"fmt"
 	"io"
 	"net/http"
 	"net/url"
-	"os"
-	"strings"
 
 	"golang.org/x/net/context/ctxhttp"
-	"golang.org/x/term"
 
 	"github.com/containerd/containerd/v2/core/remotes/docker"
 	"github.com/containerd/containerd/v2/core/remotes/docker/config"
@@ -66,7 +62,7 @@ func Login(ctx context.Context, options types.LoginCommandOptions, stdout io.Wri
 	}
 
 	if err != nil || credentials.Username == "" || credentials.Password == "" {
-		err = configureAuthentication(credentials, options.Username, options.Password)
+		err = promptUserForAuthentication(credentials, options.Username, options.Password, stdout)
 		if err != nil {
 			return err
 		}
@@ -205,56 +201,3 @@ func tryLoginWithRegHost(ctx context.Context, rh docker.RegistryHost) error {
 
 	return errors.New("too many 401 (probably)")
 }
-
-func configureAuthentication(credentials *dockerconfigresolver.Credentials, username, password string) error {
-	if username = strings.TrimSpace(username); username == "" {
-		username = credentials.Username
-	}
-	if username == "" {
-		fmt.Print("Enter Username: ")
-		usr, err := readUsername()
-		if err != nil {
-			return err
-		}
-		username = usr
-	}
-	if username == "" {
-		return fmt.Errorf("error: Username is Required")
-	}
-
-	if password == "" {
-		fmt.Print("Enter Password: ")
-		pwd, err := readPassword()
-		fmt.Println()
-		if err != nil {
-			return err
-		}
-		password = pwd
-	}
-	if password == "" {
-		return fmt.Errorf("error: Password is Required")
-	}
-
-	credentials.Username = username
-	credentials.Password = password
-
-	return nil
-}
-
-func readUsername() (string, error) {
-	var fd *os.File
-	if term.IsTerminal(int(os.Stdin.Fd())) {
-		fd = os.Stdin
-	} else {
-		return "", fmt.Errorf("stdin is not a terminal (Hint: use `nerdctl login --username=USERNAME --password-stdin`)")
-	}
-
-	reader := bufio.NewReader(fd)
-	username, err := reader.ReadString('\n')
-	if err != nil {
-		return "", fmt.Errorf("error reading username: %w", err)
-	}
-	username = strings.TrimSpace(username)
-
-	return username, nil
-}

pkg/cmd/login/prompt.go

@@ -0,0 +1,109 @@
+/*
+   Copyright The containerd 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 login
+
+import (
+	"bufio"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"strings"
+
+	"golang.org/x/term"
+
+	"github.com/containerd/nerdctl/v2/pkg/imgutil/dockerconfigresolver"
+)
+
+var (
+	// User did not provide non-empty credentials when prompted for it
+	ErrUsernameIsRequired = errors.New("username is required")
+	ErrPasswordIsRequired = errors.New("password is required")
+
+	// System errors - not a terminal, failure to read, etc
+	ErrReadingUsername        = errors.New("unable to read username")
+	ErrReadingPassword        = errors.New("unable to read password")
+	ErrNotATerminal           = errors.New("stdin is not a terminal (Hint: use `nerdctl login --username=USERNAME --password-stdin`)")
+	ErrCannotAllocateTerminal = errors.New("error allocating terminal")
+)
+
+// promptUserForAuthentication will prompt the user for credentials if needed
+// It might error with any of the errors defined above.
+func promptUserForAuthentication(credentials *dockerconfigresolver.Credentials, username, password string, stdout io.Writer) error {
+	var err error
+
+	// If the provided username is empty...
+	if username = strings.TrimSpace(username); username == "" {
+		// Use the one we know of (from the store)
+		username = credentials.Username
+		// If the one from the store was empty as well, prompt and read the username
+		if username == "" {
+			_, _ = fmt.Fprint(stdout, "Enter Username: ")
+			username, err = readUsername()
+			if err != nil {
+				return err
+			}
+
+			username = strings.TrimSpace(username)
+			// If it still is empty, that is an error
+			if username == "" {
+				return ErrUsernameIsRequired
+			}
+		}
+	}
+
+	// If password was NOT passed along, ask for it
+	if password == "" {
+		_, _ = fmt.Fprint(stdout, "Enter Password: ")
+		password, err = readPassword()
+		if err != nil {
+			return err
+		}
+
+		_, _ = fmt.Fprintln(stdout)
+		password = strings.TrimSpace(password)
+
+		// If nothing was provided, error out
+		if password == "" {
+			return ErrPasswordIsRequired
+		}
+	}
+
+	// Attach non-empty credentials to the auth object and return
+	credentials.Username = username
+	credentials.Password = password
+
+	return nil
+}
+
+// readUsername will try to read from user input
+// It might error with:
+// - ErrNotATerminal
+// - ErrReadingUsername
+func readUsername() (string, error) {
+	fd := os.Stdin
+	if !term.IsTerminal(int(fd.Fd())) {
+		return "", ErrNotATerminal
+	}
+
+	username, err := bufio.NewReader(fd).ReadString('\n')
+	if err != nil {
+		return "", errors.Join(ErrReadingUsername, err)
+	}
+
+	return strings.TrimSpace(username), nil
+}

pkg/cmd/login/login_unix.go → pkg/cmd/login/prompt_unix.go

@@ -19,28 +19,34 @@
 package login
 
 import (
-	"fmt"
+	"errors"
 	"os"
 	"syscall"
 
 	"golang.org/x/term"
+
+	"github.com/containerd/log"
 )
 
 func readPassword() (string, error) {
-	var fd int
-	if term.IsTerminal(syscall.Stdin) {
-		fd = syscall.Stdin
-	} else {
+	fd := syscall.Stdin
+	if !term.IsTerminal(fd) {
 		tty, err := os.Open("/dev/tty")
 		if err != nil {
-			return "", fmt.Errorf("error allocating terminal: %w", err)
+			return "", errors.Join(ErrCannotAllocateTerminal, err)
 		}
-		defer tty.Close()
+		defer func() {
+			err = tty.Close()
+			if err != nil {
+				log.L.WithError(err).Error("failed closing tty")
+			}
+		}()
 		fd = int(tty.Fd())
 	}
+
 	bytePassword, err := term.ReadPassword(fd)
 	if err != nil {
-		return "", fmt.Errorf("error reading password: %w", err)
+		return "", errors.Join(ErrReadingPassword, err)
 	}
 
 	return string(bytePassword), nil

pkg/cmd/login/login_windows.go → pkg/cmd/login/prompt_windows.go

@@ -17,22 +17,21 @@
 package login
 
 import (
-	"fmt"
+	"errors"
 	"syscall"
 
 	"golang.org/x/term"
 )
 
 func readPassword() (string, error) {
-	var fd int
-	if term.IsTerminal(int(syscall.Stdin)) {
-		fd = int(syscall.Stdin)
-	} else {
-		return "", fmt.Errorf("error allocating terminal")
+	fd := int(syscall.Stdin)
+	if !term.IsTerminal(fd) {
+		return "", ErrNotATerminal
 	}
+
 	bytePassword, err := term.ReadPassword(fd)
 	if err != nil {
-		return "", fmt.Errorf("error reading password: %w", err)
+		return "", errors.Join(ErrReadingPassword, err)
 	}
 
 	return string(bytePassword), nil