Add restore handler for password input

This commit restores the terminal state in case the program is
interrupted while being in password read mode. This ensures the terminal
remains usable, also if the password input is being cancelled.

Signed-off-by: Felix Niederwanger <[email protected]>

pkg/auth/auth.go

@@ -10,13 +10,13 @@ import (
 	"path/filepath"
 	"strings"
 
+	"github.com/containers/common/pkg/util"
 	"github.com/containers/image/v5/docker"
 	"github.com/containers/image/v5/docker/reference"
 	"github.com/containers/image/v5/pkg/docker/config"
 	"github.com/containers/image/v5/pkg/sysregistriesv2"
 	"github.com/containers/image/v5/types"
 	"github.com/sirupsen/logrus"
-	terminal "golang.org/x/term"
 )
 
 // GetDefaultAuthFile returns env value REGISTRY_AUTH_FILE as default
@@ -244,12 +244,12 @@ func getUserAndPass(opts *LoginOptions, password, userFromAuthFile string) (user
 	}
 	if password == "" {
 		fmt.Fprint(opts.Stdout, "Password: ")
-		pass, err := terminal.ReadPassword(int(os.Stdin.Fd()))
+		pass, err := util.ReadPassword(int(os.Stdin.Fd()))
 		if err != nil {
 			return "", "", fmt.Errorf("reading password: %w", err)
 		}
-		password = string(pass)
 		fmt.Fprintln(opts.Stdout)
+		password = string(pass)
 	}
 	return strings.TrimSpace(username), password, err
 }

pkg/util/util.go

@@ -1,6 +1,14 @@
 package util
 
-import "regexp"
+import (
+	"fmt"
+	"os"
+	"os/signal"
+	"regexp"
+	"syscall"
+
+	"golang.org/x/term"
+)
 
 // StringInSlice determines if a string is in a string slice, returns bool
 func StringInSlice(s string, sl []string) bool {
@@ -22,3 +30,68 @@ func StringMatchRegexSlice(s string, re []string) bool {
 	}
 	return false
 }
+
+// ReadPassword reads a password from the terminal and restores the terminal state on interruption
+func ReadPassword(fd int) ([]byte, error) {
+	// Store and restore the terminal status on interruptions to
+	// avoid that the terminal remains in the password state
+	// This is necessary as for https://github.com/golang/go/issues/31180
+
+	/* WARNING: This commit contains two suggestions and should as such not be commited !! */
+	reemitSolution := true
+
+	/* Suggestion 1: Re-emit the interrupt signal, but restore the terminal in-between*/
+	if reemitSolution {
+		oldState, _ := term.GetState(fd)
+		interruptChannel := make(chan os.Signal, 1)
+		signal.Notify(interruptChannel, os.Interrupt)
+		defer func() {
+			signal.Stop(interruptChannel)
+			close(interruptChannel)
+		}()
+		go func() {
+			for range interruptChannel {
+				if oldState != nil {
+					term.Restore(fd, oldState)
+				}
+				// Call the default SIGINT handler
+				signal.Reset(os.Interrupt)
+				syscall.Kill(syscall.Getpid(), syscall.SIGINT)
+			}
+		}()
+		return term.ReadPassword(fd)
+	} else {
+		/* Suggestion 2: Gracefully handle the interrupt signal, but leave the terminal input blocked */
+
+		type ByteBuffer struct {
+			buf []byte
+			err error
+		}
+
+		oldState, _ := term.GetState(fd)
+		interruptChannel := make(chan os.Signal, 1)
+		signal.Notify(interruptChannel, os.Interrupt)
+		defer func() {
+			signal.Stop(interruptChannel)
+			close(interruptChannel)
+		}()
+
+		// Read from the file descriptor or wait for the interrupt signal
+		inputChannel := make(chan ByteBuffer, 1)
+		defer close(inputChannel)
+		go func() {
+			var buf ByteBuffer
+			buf.buf, buf.err = term.ReadPassword(fd)
+			inputChannel <- buf
+		}()
+		select {
+		case <-interruptChannel:
+			if oldState != nil {
+				term.Restore(fd, oldState)
+			}
+			return make([]byte, 0), fmt.Errorf("interrupted")
+		case buf := <-inputChannel:
+			return buf.buf, buf.err
+		}
+	}
+}