Fixes stdin default during jailing

Prior to this fix the SDK would use os.Stdin if no stdin was provided in
the jailer config. This would cause shell sessions to break and should
only include stdin if it was provided in the jailer config.

Signed-off-by: xibz <[email protected]>

Author: jeromegn

jailer.go

@@ -309,12 +309,7 @@ func jail(ctx context.Context, m *Machine, cfg *Config) error {
 		stderr = os.Stderr
 	}
 
-	stdin := cfg.JailerCfg.Stdin
-	if stdin == nil {
-		stdin = os.Stdin
-	}
-
-	m.cmd = NewJailerCommandBuilder().
+	builder := NewJailerCommandBuilder().
 		WithID(cfg.JailerCfg.ID).
 		WithUID(*cfg.JailerCfg.UID).
 		WithGID(*cfg.JailerCfg.GID).
@@ -324,9 +319,13 @@ func jail(ctx context.Context, m *Machine, cfg *Config) error {
 		WithDaemonize(cfg.JailerCfg.Daemonize).
 		WithSeccompLevel(cfg.JailerCfg.SeccompLevel).
 		WithStdout(stdout).
-		WithStderr(stderr).
-		WithStdin(stdin).
-		Build(ctx)
+		WithStderr(stderr)
+
+	if stdin := cfg.JailerCfg.Stdin; stdin != nil {
+		builder.WithStdin(stdin)
+	}
+
+	m.cmd = builder.Build(ctx)
 
 	if err := cfg.JailerCfg.ChrootStrategy.AdaptHandlers(&m.Handlers); err != nil {
 		return err