[kbd] [PATCH] kbd_mode: Add -f option and deny dangerous mode switches without it

[Alexey Gladkov]

On Tue, Apr 23, 2019 at 05:38:07PM +0200, Balint Reczey wrote:
> kbd_mode(1) already had a warning but kbd_mode still performed all
> mode changes even when they made keyboards unusable.
> 
> The added flag let's the callers try safe changes or force the risky
> ones. This change may break scripts but the broken scripts most likely
> made the keyboard unusable and should be updated.
> 
> Original bug report at:
> https://bugs.launchpad.net/ubuntu/+source/kbd/+bug/520546
> 
> Signed-off-by: Balint Reczey <balint.reczey at canonical.com>

It sounds sane. Applied. Thanks!

> ---
>  docs/man/man1/kbd_mode.1 |  8 +++--
>  src/kbd_mode.c           | 65 ++++++++++++++++++++++++++++------------
>  2 files changed, 52 insertions(+), 21 deletions(-)
> 
> diff --git a/docs/man/man1/kbd_mode.1 b/docs/man/man1/kbd_mode.1
> index 960b36c..f605c02 100644
> --- a/docs/man/man1/kbd_mode.1
> +++ b/docs/man/man1/kbd_mode.1
> @@ -7,6 +7,8 @@ kbd_mode \- report or set the keyboard mode
>  [
>  .I -a | -u | -k | -s 
>  ] [
> +.I -f
> +] [
>  .I -C CONSOLE
>  ]
>  .SH DESCRIPTION
> @@ -36,11 +38,13 @@ kbd_mode operates on the console specified by the "\-C" option; if there
>  is none, the console associated with stdin is used.
>  
>  Warning: changing the keyboard mode, other than between ASCII and
> -Unicode, will probably make your keyboard unusable.
> +Unicode, will probably make your keyboard unusable. Set the "\-f" option
> +to force such changes.
>  This command is only meant for use (say via remote login)
>  when some program left your keyboard in the wrong state.
>  Note that in some obsolete versions of this program the "\-u"
> -option was a synonym for "\-s".
> +option was a synonym for "\-s" and older versions of this program may
> +not recognize the "\-f" option.
>  .SH "SEE ALSO"
>  .BR loadkeys (1)
>  
> diff --git a/src/kbd_mode.c b/src/kbd_mode.c
> index 5d291b7..956ea51 100644
> --- a/src/kbd_mode.c
> +++ b/src/kbd_mode.c
> @@ -20,13 +20,34 @@
>  static void __attribute__((noreturn))
>  usage(void)
>  {
> -	fprintf(stderr, _("usage: kbd_mode [-a|-u|-k|-s] [-C device]\n"));
> +	fprintf(stderr, _("usage: kbd_mode [-a|-u|-k|-s] [-f] [-C device]\n"));
>  	exit(EXIT_FAILURE);
>  }
>  
> +static void
> +fprint_mode(FILE *stream, int  mode)
> +{
> +	switch (mode) {
> +		case K_RAW:
> +			fprintf(stream, _("The keyboard is in raw (scancode) mode\n"));
> +			break;
> +		case K_MEDIUMRAW:
> +			fprintf(stream, _("The keyboard is in mediumraw (keycode) mode\n"));
> +			break;
> +		case K_XLATE:
> +			fprintf(stream, _("The keyboard is in the default (ASCII) mode\n"));
> +			break;
> +		case K_UNICODE:
> +			fprintf(stream, _("The keyboard is in Unicode (UTF-8) mode\n"));
> +			break;
> +		default:
> +			fprintf(stream, _("The keyboard is in some unknown mode\n"));
> +        }
> +}
> +
>  int main(int argc, char *argv[])
>  {
> -	int fd, mode, c, n = 0;
> +	int fd, mode, orig_mode, c, n = 0, force = 0;
>  	char *console = NULL;
>  
>  	set_progname(argv[0]);
> @@ -38,7 +59,7 @@ int main(int argc, char *argv[])
>  	if (argc == 2 && !strcmp(argv[1], "-V"))
>  		print_version_and_exit();
>  
> -	while ((c = getopt(argc, argv, "auskC:")) != EOF) {
> +	while ((c = getopt(argc, argv, "auskfC:")) != EOF) {
>  		switch (c) {
>  			case 'a':
>  				if (n > 0)
> @@ -64,6 +85,9 @@ int main(int argc, char *argv[])
>  				mode = K_MEDIUMRAW;
>  				n++;
>  				break;
> +			case 'f':
> +				force = 1;
> +				break;
>  			case 'C':
>  				if (!optarg || !optarg[0])
>  					usage();
> @@ -82,25 +106,28 @@ int main(int argc, char *argv[])
>  		if (ioctl(fd, KDGKBMODE, &mode)) {
>  			kbd_error(EXIT_FAILURE, errno, "ioctl KDGKBMODE");
>  		}
> -		switch (mode) {
> -			case K_RAW:
> -				printf(_("The keyboard is in raw (scancode) mode\n"));
> -				break;
> -			case K_MEDIUMRAW:
> -				printf(_("The keyboard is in mediumraw (keycode) mode\n"));
> -				break;
> -			case K_XLATE:
> -				printf(_("The keyboard is in the default (ASCII) mode\n"));
> -				break;
> -			case K_UNICODE:
> -				printf(_("The keyboard is in Unicode (UTF-8) mode\n"));
> -				break;
> -			default:
> -				printf(_("The keyboard is in some unknown mode\n"));
> -		}
> +		fprint_mode(stdout, mode);
>  		return EXIT_SUCCESS;
>  	}
>  
> +	if (force == 0) {
> +		/* only perform safe mode switches */
> +		if (ioctl(fd, KDGKBMODE, &orig_mode)) {
> +			kbd_error(EXIT_FAILURE, errno, "ioctl KDGKBMODE");
> +		}
> +
> +		if (mode == orig_mode) {
> +			/* skip mode change */
> +			return EXIT_SUCCESS;
> +		}
> +
> +		if ((mode == K_XLATE && orig_mode != K_UNICODE) || (mode == K_UNICODE && orig_mode != K_XLATE)) {
> +			fprint_mode(stderr, orig_mode);
> +			fprintf(stderr, _("Changing to the requested mode may make "
> +				"your keyboard unusable, please use -f to force the change.\n"));
> +			return EXIT_FAILURE;
> +		}
> +	}
>  	if (ioctl(fd, KDSKBMODE, mode)) {
>  		kbd_error(EXIT_FAILURE, errno, "ioctl KDSKBMODE");
>  	}
> -- 
> 2.17.1
> 
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-- 
Rgrds, legion