Fix panic 'provided file is not a console'

As outlined in #3433, containerd/console will panic on a call to console.Current().
This patch provides a simple consoleutil wrapper that will return an error instead.

Note that part of #3300 is being reverted, as no longer necessary.

This patch does not try to be "smart" and does not check the status of stdin/out/err otherwise or if it is consistent with user provided flags,
but merely ensures we do not crash.

Signed-off-by: apostasie <spam_blackhole@farcloser.world>

Author: apostasie

cmd/nerdctl/container/container_exec.go

@@ -18,9 +18,7 @@ package container
 
 import (
 	"errors"
-	"os"
 
-	"github.com/moby/term"
 	"github.com/spf13/cobra"
 
 	containerd "github.com/containerd/containerd/v2/client"
@@ -88,13 +86,6 @@ func processExecCommandOptions(cmd *cobra.Command) (types.ContainerExecOptions,
 		}
 	}
 
-	_, isTerminal := term.GetFdInfo(os.Stdin)
-	if !flagD {
-		if flagT && flagI && !isTerminal {
-			return types.ContainerExecOptions{}, errors.New("the input device is not a TTY")
-		}
-	}
-
 	workdir, err := cmd.Flags().GetString("workdir")
 	if err != nil {
 		return types.ContainerExecOptions{}, err

cmd/nerdctl/container/container_run.go

@@ -389,7 +389,10 @@ func runAction(cmd *cobra.Command, args []string) error {
 
 	var con console.Console
 	if createOpt.TTY && !createOpt.Detach {
-		con = console.Current()
+		con, err = consoleutil.Current()
+		if err != nil {
+			return err
+		}
 		defer con.Reset()
 		if err := con.SetRaw(); err != nil {
 			return err

pkg/cmd/container/attach.go

@@ -66,7 +66,10 @@ func Attach(ctx context.Context, client *containerd.Client, req string, options
 		con console.Console
 	)
 	if spec.Process.Terminal {
-		con = console.Current()
+		con, err = consoleutil.Current()
+		if err != nil {
+			return err
+		}
 		defer con.Reset()
 		if err := con.SetRaw(); err != nil {
 			return fmt.Errorf("failed to set the console to raw mode: %w", err)

pkg/cmd/container/exec.go

@@ -106,7 +106,10 @@ func execActionWithContainer(ctx context.Context, client *containerd.Client, con
 
 	var con console.Console
 	if options.TTY {
-		con = console.Current()
+		con, err = consoleutil.Current()
+		if err != nil {
+			return err
+		}
 		defer con.Reset()
 		if err := con.SetRaw(); err != nil {
 			return err
@@ -164,7 +167,11 @@ func generateExecProcessSpec(ctx context.Context, client *containerd.Client, con
 	pspec := spec.Process
 	pspec.Terminal = options.TTY
 	if pspec.Terminal {
-		if size, err := console.Current().Size(); err == nil {
+		con, err := consoleutil.Current()
+		if err != nil {
+			return nil, err
+		}
+		if size, err := con.Size(); err == nil {
 			pspec.ConsoleSize = &specs.Box{Height: uint(size.Height), Width: uint(size.Width)}
 		}
 	}

pkg/consoleutil/consoleutil.go

@@ -18,8 +18,22 @@ package consoleutil
 
 import (
 	"context"
+	"os"
+
+	"github.com/containerd/console"
 )
 
+// Current is from https://github.com/containerd/console/blob/main/console.go#L68-L80
+// adapted so that it does not panic
+func Current() (c console.Console, err error) {
+	for _, s := range []*os.File{os.Stderr, os.Stdout, os.Stdin} {
+		if c, err = console.ConsoleFromFile(s); err == nil {
+			return c, nil
+		}
+	}
+	return nil, console.ErrNotAConsole
+}
+
 // resizer is from https://github.com/containerd/containerd/blob/v1.7.0-rc.2/cmd/ctr/commands/tasks/tasks.go#L25-L27
 type resizer interface {
 	Resize(ctx context.Context, w, h uint32) error

pkg/containerutil/containerutil.go

@@ -244,7 +244,10 @@ func Start(ctx context.Context, container containerd.Container, flagA bool, clie
 	flagT := process.Process.Terminal
 	var con console.Console
 	if flagA && flagT {
-		con = console.Current()
+		con, err = consoleutil.Current()
+		if err != nil {
+			return err
+		}
 		defer con.Reset()
 		if err := con.SetRaw(); err != nil {
 			return err