[v2] ui/ncurses: Safely handle lost terminal control commands

Message ID 20171113045045.32071-1-sam@mendozajonas.com
State Accepted
Headers show
Series
  • [v2] ui/ncurses: Safely handle lost terminal control commands
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Commit Message

Samuel Mendoza-Jonas Nov. 13, 2017, 4:50 a.m.
Normally terminal control commands are caught and handled before ncurses
or Petitboot could see them. However several combinations of broken
terminal emulators or console connections can cause these command
sequences to be seen by Petitboot, usually resulting in Petitboot
exiting due to the ESC character and then the rest printed to the
console.

Aside from confusing the user this can also cancel autoboot, so it's
important we don't let these sequences go unnoticed if possible.
In ui/ncurses/console-codes we add a state machine that recognises the
syntax of these control/escape sequences and handles the lost
characters. We don't try to emulate the functionality of these commands,
instead just logging them for reference.

Signed-off-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>
---
v2: Add extra test cases, clean up some string operations and NULL checks

 Makefile.am                |   1 +
 test/ui/Makefile.am        |  35 +++++++++
 test/ui/console-sequence.c | 112 ++++++++++++++++++++++++++++
 ui/ncurses/Makefile.am     |   2 +
 ui/ncurses/console-codes.c | 178 +++++++++++++++++++++++++++++++++++++++++++++
 ui/ncurses/console-codes.h |  20 +++++
 ui/ncurses/nc-cui.c        |  28 +++++++
 7 files changed, 376 insertions(+)
 create mode 100644 test/ui/Makefile.am
 create mode 100644 test/ui/console-sequence.c
 create mode 100644 ui/ncurses/console-codes.c
 create mode 100644 ui/ncurses/console-codes.h

Comments

Cyril Bur Nov. 13, 2017, 11:37 p.m. | #1
On Mon, 2017-11-13 at 15:50 +1100, Samuel Mendoza-Jonas wrote:
> Normally terminal control commands are caught and handled before ncurses
> or Petitboot could see them. However several combinations of broken
> terminal emulators or console connections can cause these command
> sequences to be seen by Petitboot, usually resulting in Petitboot
> exiting due to the ESC character and then the rest printed to the
> console.
> 
> Aside from confusing the user this can also cancel autoboot, so it's
> important we don't let these sequences go unnoticed if possible.
> In ui/ncurses/console-codes we add a state machine that recognises the
> syntax of these control/escape sequences and handles the lost
> characters. We don't try to emulate the functionality of these commands,
> instead just logging them for reference.
> 

I remember you mumbling things about signed chars vs [unsigned] chars.
I noticed that:
+	signed char c;
+	char *seq;

c is signed but seq are 'default'. If this is on purpose then:

Reviewed-by: Cyril Bur <cyrilbur@gmail.com>

> Signed-off-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>
> ---
> v2: Add extra test cases, clean up some string operations and NULL checks
> 
>  Makefile.am                |   1 +
>  test/ui/Makefile.am        |  35 +++++++++
>  test/ui/console-sequence.c | 112 ++++++++++++++++++++++++++++
>  ui/ncurses/Makefile.am     |   2 +
>  ui/ncurses/console-codes.c | 178 +++++++++++++++++++++++++++++++++++++++++++++
>  ui/ncurses/console-codes.h |  20 +++++
>  ui/ncurses/nc-cui.c        |  28 +++++++
>  7 files changed, 376 insertions(+)
>  create mode 100644 test/ui/Makefile.am
>  create mode 100644 test/ui/console-sequence.c
>  create mode 100644 ui/ncurses/console-codes.c
>  create mode 100644 ui/ncurses/console-codes.h
> 
> diff --git a/Makefile.am b/Makefile.am
> index 15d561f..c0ad839 100644
> --- a/Makefile.am
> +++ b/Makefile.am
> @@ -55,6 +55,7 @@ include test/Makefile.am
>  include test/lib/Makefile.am
>  include test/parser/Makefile.am
>  include test/urls/Makefile.am
> +include test/ui/Makefile.am
>  include ui/common/Makefile.am
>  
>  if WITH_NCURSES
> diff --git a/test/ui/Makefile.am b/test/ui/Makefile.am
> new file mode 100644
> index 0000000..19c3637
> --- /dev/null
> +++ b/test/ui/Makefile.am
> @@ -0,0 +1,35 @@
> +#  This program is free software; you can redistribute it and/or modify
> +#  it under the terms of the GNU General Public License as published by
> +#  the Free Software Foundation; version 2 of the License.
> +#
> +#  This program is distributed in the hope that it will be useful,
> +#  but WITHOUT ANY WARRANTY; without even the implied warranty of
> +#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +#  GNU General Public License for more details.
> +#
> +#  You should have received a copy of the GNU General Public License
> +#  along with this program; if not, write to the Free Software
> +#  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
> +
> +ui_TESTS = \
> +	test/ui/console-sequence
> +
> +TESTS += $(ui_TESTS)
> +check_PROGRAMS += $(ui_TESTS)
> +
> +test_ui_console_sequence_SOURCES = \
> +	test/ui/console-sequence.c
> +
> +test_ui_console_sequence_CPPFLAGS = \
> +	-DPETITBOOT_TEST \
> +	-I$(top_srcdir)/lib
> +
> +test_ui_console_sequence_LDFLAGS = \
> +	$(core_lib)
> +
> +
> +
> +#$(ui_TESTS): LIBS += \
> +#	ui/ncurses/libpbnc.la \
> +#	$(core_lib) \
> +#	@MENU_LIB@ @FORM_LIB@ @CURSES_LIB@
> diff --git a/test/ui/console-sequence.c b/test/ui/console-sequence.c
> new file mode 100644
> index 0000000..cbb2007
> --- /dev/null
> +++ b/test/ui/console-sequence.c
> @@ -0,0 +1,112 @@
> +/*
> + *  Copyright (C) 2017 IBM Corporation
> + *
> + *  This program is free software; you can redistribute it and/or modify
> + *  it under the terms of the GNU General Public License as published by
> + *  the Free Software Foundation; version 2 of the License.
> + *
> + *  This program is distributed in the hope that it will be useful,
> + *  but WITHOUT ANY WARRANTY; without even the implied warranty of
> + *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + *  GNU General Public License for more details.
> + *
> + */
> +
> +#include <stdlib.h>
> +#include <string.h>
> +#include <assert.h>
> +#include <stdbool.h>
> +#include <stdio.h>
> +
> +#include "talloc/talloc.h"
> +
> +#define ERR     (-1)
> +#define pb_log(...)	printf(__VA_ARGS__)
> +#define pb_debug(...)	printf(__VA_ARGS__)
> +
> +/*
> + * Several example terminal commands, see:
> + * https://vt100.net/docs/vt100-ug/chapter3.html
> + */
> +static char identify_rsp[] = {033, 0133, 077, 061, 073, 060, 0143, '\0'};
> +static char decdwl[] = {033, 043, 066, '\0'};
> +static char attrs[] = {033, 0133, 060, 073, 064, 073, 065, 0155, '\0'};
> +static char cursor[] = {033, 070, '\0'};
> +static char conf_test[] = {033, 0133, 062, 073, 061, 0171, '\0'};
> +static char status[] = {033, 0133, 060, 0156, '\0'};
> +static char erase_screen[] = {033, 0133, 062, 0112, '\0'};
> +static char status_ok_rsp[] = {033, 0133, 064, 0156, '\0'};
> +static char garbage[] = {001, 002, 003, 004, '\0'};
> +static char esc_garbage[] = {033, 002, 003, 004, '\0'};
> +static char *ptr;
> +
> +static char getch(void)
> +{
> +	if (!ptr || *ptr == '\0')
> +		return -ERR;
> +	return *ptr++;
> +}
> +
> +#include "ui/ncurses/console-codes.c"
> +
> +int main(void)
> +{
> +	void *ctx;
> +	char *seq, *confused;
> +
> +	ctx = talloc_new(NULL);
> +
> +	ptr = &identify_rsp[1];
> +	printf("Identity response\n");
> +	seq = handle_control_sequence(ctx, identify_rsp[0]);
> +	assert(strncmp(seq, identify_rsp, strlen(identify_rsp)) == 0);
> +
> +	printf("DECDWL\n");
> +	ptr = &decdwl[1];
> +	seq = handle_control_sequence(ctx, decdwl[0]);
> +	assert(strncmp(seq, decdwl, strlen(decdwl)) == 0);
> +
> +	printf("Attributes\n");
> +	ptr = &attrs[1];
> +	seq = handle_control_sequence(ctx, attrs[0]);
> +	assert(strncmp(seq, attrs, strlen(attrs)) == 0);
> +
> +	printf("Reset Cursor\n");
> +	ptr = &cursor[1];
> +	seq = handle_control_sequence(ctx, cursor[0]);
> +	assert(strncmp(seq, cursor, strlen(cursor)) == 0);
> +
> +	printf("Confidence Test\n");
> +	ptr = &conf_test[1];
> +	seq = handle_control_sequence(ctx, conf_test[0]);
> +	assert(strncmp(seq, conf_test, strlen(conf_test)) == 0);
> +
> +	printf("Status\n");
> +	ptr = &status[1];
> +	seq = handle_control_sequence(ctx, status[0]);
> +	assert(strncmp(seq, status, strlen(status)) == 0);
> +
> +	printf("Erase Screen\n");
> +	ptr = &erase_screen[1];
> +	seq = handle_control_sequence(ctx, erase_screen[0]);
> +	assert(strncmp(seq, erase_screen, strlen(erase_screen)) == 0);
> +
> +	printf("Status Response\n");
> +	ptr = &status_ok_rsp[1];
> +	seq = handle_control_sequence(ctx, status_ok_rsp[0]);
> +	assert(strncmp(seq, status_ok_rsp, strlen(status_ok_rsp)) == 0);
> +
> +	printf("Garbage\n");
> +	ptr = &garbage[1];
> +	seq = handle_control_sequence(ctx, garbage[0]);
> +	assert(seq == NULL);
> +
> +	printf("ESC then Garbage\n");
> +	ptr = &esc_garbage[1];
> +	confused = talloc_asprintf(ctx, "%c%c...", 033, 002);
> +	seq = handle_control_sequence(ctx, esc_garbage[0]);
> +	assert(strncmp(seq, confused, strlen(confused)) == 0);
> +
> +	talloc_free(ctx);
> +	return EXIT_SUCCESS;
> +}
> diff --git a/ui/ncurses/Makefile.am b/ui/ncurses/Makefile.am
> index 40e11b8..3bc5254 100644
> --- a/ui/ncurses/Makefile.am
> +++ b/ui/ncurses/Makefile.am
> @@ -24,6 +24,8 @@ ui_ncurses_libpbnc_la_SOURCES = \
>  	ui/ncurses/nc-config.c \
>  	ui/ncurses/nc-config.h \
>  	ui/ncurses/nc-config-help.c \
> +	ui/ncurses/console-codes.c \
> +	ui/ncurses/console-codes.h \
>  	ui/ncurses/nc-cui.c \
>  	ui/ncurses/nc-cui.h \
>  	ui/ncurses/nc-cui-help.c \
> diff --git a/ui/ncurses/console-codes.c b/ui/ncurses/console-codes.c
> new file mode 100644
> index 0000000..68cdfab
> --- /dev/null
> +++ b/ui/ncurses/console-codes.c
> @@ -0,0 +1,178 @@
> +/*
> + *  Copyright (C) 2017 IBM Corporation
> + *
> + *  This program is free software; you can redistribute it and/or modify
> + *  it under the terms of the GNU General Public License as published by
> + *  the Free Software Foundation; version 2 of the License.
> + *
> + *  This program is distributed in the hope that it will be useful,
> + *  but WITHOUT ANY WARRANTY; without even the implied warranty of
> + *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + *  GNU General Public License for more details.
> + *
> + */
> +
> +#if defined(HAVE_CONFIG_H)
> +#include "config.h"
> +#endif
> +
> +#include <ctype.h>
> +#include <errno.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <stdbool.h>
> +
> +#include "talloc/talloc.h"
> +
> +#ifndef PETITBOOT_TEST
> +#include "log/log.h"
> +#include "nc-scr.h"
> +#endif
> +
> +#include "console-codes.h"
> +
> +#define ESC_CHAR			033
> +#define CSI_CHAR			'['
> +#define INTER_CHAR_START		040
> +#define INTER_CHAR_END			057
> +#define ESC_SEQUENCE_FINAL_START	060
> +#define ESC_SEQUENCE_FINAL_END		0176
> +#define CTRL_SEQUENCE_FINAL_START	0100
> +#define CTRL_SEQUENCE_FINAL_END		0176
> +#define DEC_PARAMETER			077
> +
> +enum console_sequence_state {
> +	CONSOLE_STATE_START,
> +	CONSOLE_STATE_ESC_SEQ,
> +	CONSOLE_STATE_CTRL_SEQ_START,
> +	CONSOLE_STATE_CTRL_SEQ,
> +	CONSOLE_STATE_DONE,
> +	CONSOLE_STATE_CONFUSED,
> +};
> +
> +static inline bool is_intermediate(char c)
> +{
> +	return c > INTER_CHAR_START && c < INTER_CHAR_END;
> +}
> +
> +static inline bool is_parameter(char c)
> +{
> +	return (c >= 060 && c <= 071) || c == 073;
> +}
> +
> +static inline bool is_escape_final(char c)
> +{
> +	return c >= ESC_SEQUENCE_FINAL_START && c < ESC_SEQUENCE_FINAL_END;
> +}
> +
> +static inline bool is_control_final(char c)
> +{
> +	return c >= CTRL_SEQUENCE_FINAL_START && c <= CTRL_SEQUENCE_FINAL_END;
> +}
> +
> +static signed char console_sequence_getch(char **sequence)
> +{
> +	signed char c = getch();
> +
> +	if (c != ERR)
> +		*sequence = talloc_asprintf_append(*sequence, "%c", c);
> +	return c;
> +}
> +
> +/*
> + * Catch terminal control sequences that have accidentally been sent to
> + * Petitboot. These are of the form
> + * 	ESC I .. I F
> + * where I is an Intermediate Character and F is a Final Character, eg:
> + * 	ESC ^ [ ? 1 ; 0 c
> + * or	ESC # 6
> + *
> + * This is based off the definitions provided by
> + * https://vt100.net/docs/vt100-ug/contents.html
> + */
> +char *handle_control_sequence(void *ctx, char start)
> +{
> +	enum console_sequence_state state = CONSOLE_STATE_START;
> +	bool in_sequence = true;
> +	signed char c;
> +	char *seq;
> +
> +	if (start != ESC_CHAR) {
> +		pb_log("%s: Called with non-escape character: 0%o\n",
> +				__func__, start);
> +		return NULL;
> +	}
> +
> +	seq = talloc_asprintf(ctx, "%c", start);
> +
> +	while (in_sequence) {
> +		switch (state) {
> +		case CONSOLE_STATE_START:
> +			c = console_sequence_getch(&seq);
> +			if (c == CSI_CHAR)
> +				state = CONSOLE_STATE_CTRL_SEQ_START;
> +			else if (is_intermediate(c))
> +				state = CONSOLE_STATE_ESC_SEQ;
> +			else if (is_escape_final(c))
> +				state = CONSOLE_STATE_DONE;
> +			else if (c != ERR) {
> +				/* wait on c == ERR */
> +				pb_debug("Unexpected start: \\x%x\n", c);
> +				state = CONSOLE_STATE_CONFUSED;
> +			}
> +			break;
> +		case CONSOLE_STATE_ESC_SEQ:
> +			c = console_sequence_getch(&seq);
> +			if (is_intermediate(c))
> +				state = CONSOLE_STATE_ESC_SEQ;
> +			else if (is_escape_final(c))
> +				state = CONSOLE_STATE_DONE;
> +			else if (c != ERR) {
> +				/* wait on c == ERR */
> +				pb_debug("Unexpected character after intermediate: \\x%x\n",
> +						c);
> +				state = CONSOLE_STATE_CONFUSED;
> +			}
> +			break;
> +		case CONSOLE_STATE_CTRL_SEQ_START:
> +			c = console_sequence_getch(&seq);
> +			if (is_intermediate(c) || is_parameter(c) ||
> +					c == DEC_PARAMETER)
> +				state = CONSOLE_STATE_CTRL_SEQ;
> +			else if (is_control_final(c))
> +				state = CONSOLE_STATE_DONE;
> +			else if (c != ERR) {
> +				/* wait on c == ERR */
> +				pb_debug("Unexpected character in param string:  \\x%x\n",
> +						c);
> +				state = CONSOLE_STATE_CONFUSED;
> +			}
> +			break;
> +		case CONSOLE_STATE_CTRL_SEQ:
> +			c = console_sequence_getch(&seq);
> +			if (is_intermediate(c) || is_parameter(c))
> +				state = CONSOLE_STATE_CTRL_SEQ;
> +			else if (is_control_final(c))
> +				state = CONSOLE_STATE_DONE;
> +			else if (c != ERR) {
> +				/* wait on c == ERR */
> +				pb_debug("Unexpected character in param string:  \\x%x\n",
> +						c);
> +				state = CONSOLE_STATE_CONFUSED;
> +			}
> +			break;
> +		case CONSOLE_STATE_DONE:
> +			in_sequence = false;
> +			break;
> +		case CONSOLE_STATE_CONFUSED:
> +			/* fall-through */
> +		default:
> +			pb_debug("We got lost interpreting a control sequence!\n");
> +			seq = talloc_asprintf_append(seq, "...");
> +			in_sequence = false;
> +			break;
> +		};
> +	}
> +
> +	return seq;
> +}
> diff --git a/ui/ncurses/console-codes.h b/ui/ncurses/console-codes.h
> new file mode 100644
> index 0000000..6de54a7
> --- /dev/null
> +++ b/ui/ncurses/console-codes.h
> @@ -0,0 +1,20 @@
> +/*
> + *  Copyright (C) 2017 IBM Corporation
> + *
> + *  This program is free software; you can redistribute it and/or modify
> + *  it under the terms of the GNU General Public License as published by
> + *  the Free Software Foundation; version 2 of the License.
> + *
> + *  This program is distributed in the hope that it will be useful,
> + *  but WITHOUT ANY WARRANTY; without even the implied warranty of
> + *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + *  GNU General Public License for more details.
> + *
> + */
> +
> +#if !defined(_PB_UI_CONSOLE_CODES)
> +#define _PB_UI_CONSOLE_CODES
> +
> +char *handle_control_sequence(void *ctx, char start);
> +
> +#endif
> diff --git a/ui/ncurses/nc-cui.c b/ui/ncurses/nc-cui.c
> index 6ced24c..8060510 100644
> --- a/ui/ncurses/nc-cui.c
> +++ b/ui/ncurses/nc-cui.c
> @@ -21,6 +21,7 @@
>  #endif
>  
>  #include <assert.h>
> +#include <ctype.h>
>  #include <errno.h>
>  #include <stdlib.h>
>  #include <string.h>
> @@ -45,6 +46,7 @@
>  #include "nc-statuslog.h"
>  #include "nc-subset.h"
>  #include "nc-plugin.h"
> +#include "console-codes.h"
>  
>  extern const struct help_text main_menu_help_text;
>  extern const struct help_text plugin_menu_help_text;
> @@ -524,6 +526,9 @@ static bool process_global_keys(struct cui *cui, int key)
>  static int cui_process_key(void *arg)
>  {
>  	struct cui *cui = cui_from_arg(arg);
> +	unsigned int i;
> +	char *sequence;
> +	int grab;
>  
>  	assert(cui->current);
>  
> @@ -535,6 +540,29 @@ static int cui_process_key(void *arg)
>  		if (c == ERR)
>  			break;
>  
> +		if (c == 27) {
> +			/*
> +			 * If this is a console code sequence try to parse it
> +			 * and don't treat this as a key press.
> +			 */
> +			grab = getch();
> +			if (grab != ERR && grab != 27) {
> +				ungetch(grab);
> +				pb_debug("%s: Caught unhandled command sequence\n",
> +						__func__);
> +				sequence = handle_control_sequence(cui, c);
> +				pb_debug("Caught sequence ");
> +				if (sequence) {
> +					pb_debug("(%zu): ", strlen(sequence));
> +					for (i = 0; i < strlen(sequence); i++)
> +						pb_debug("0%o ", sequence[i]);
> +					pb_debug("\n");
> +				} else
> +					pb_debug("(0): (none)\n");
> +				continue;
> +			}
> +		}
> +
>  		if (!cui->has_input) {
>  			cui->has_input = true;
>  			if (cui->client) {

Patch

diff --git a/Makefile.am b/Makefile.am
index 15d561f..c0ad839 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -55,6 +55,7 @@  include test/Makefile.am
 include test/lib/Makefile.am
 include test/parser/Makefile.am
 include test/urls/Makefile.am
+include test/ui/Makefile.am
 include ui/common/Makefile.am
 
 if WITH_NCURSES
diff --git a/test/ui/Makefile.am b/test/ui/Makefile.am
new file mode 100644
index 0000000..19c3637
--- /dev/null
+++ b/test/ui/Makefile.am
@@ -0,0 +1,35 @@ 
+#  This program is free software; you can redistribute it and/or modify
+#  it under the terms of the GNU General Public License as published by
+#  the Free Software Foundation; version 2 of the License.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with this program; if not, write to the Free Software
+#  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+
+ui_TESTS = \
+	test/ui/console-sequence
+
+TESTS += $(ui_TESTS)
+check_PROGRAMS += $(ui_TESTS)
+
+test_ui_console_sequence_SOURCES = \
+	test/ui/console-sequence.c
+
+test_ui_console_sequence_CPPFLAGS = \
+	-DPETITBOOT_TEST \
+	-I$(top_srcdir)/lib
+
+test_ui_console_sequence_LDFLAGS = \
+	$(core_lib)
+
+
+
+#$(ui_TESTS): LIBS += \
+#	ui/ncurses/libpbnc.la \
+#	$(core_lib) \
+#	@MENU_LIB@ @FORM_LIB@ @CURSES_LIB@
diff --git a/test/ui/console-sequence.c b/test/ui/console-sequence.c
new file mode 100644
index 0000000..cbb2007
--- /dev/null
+++ b/test/ui/console-sequence.c
@@ -0,0 +1,112 @@ 
+/*
+ *  Copyright (C) 2017 IBM Corporation
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; version 2 of the License.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ */
+
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include <stdbool.h>
+#include <stdio.h>
+
+#include "talloc/talloc.h"
+
+#define ERR     (-1)
+#define pb_log(...)	printf(__VA_ARGS__)
+#define pb_debug(...)	printf(__VA_ARGS__)
+
+/*
+ * Several example terminal commands, see:
+ * https://vt100.net/docs/vt100-ug/chapter3.html
+ */
+static char identify_rsp[] = {033, 0133, 077, 061, 073, 060, 0143, '\0'};
+static char decdwl[] = {033, 043, 066, '\0'};
+static char attrs[] = {033, 0133, 060, 073, 064, 073, 065, 0155, '\0'};
+static char cursor[] = {033, 070, '\0'};
+static char conf_test[] = {033, 0133, 062, 073, 061, 0171, '\0'};
+static char status[] = {033, 0133, 060, 0156, '\0'};
+static char erase_screen[] = {033, 0133, 062, 0112, '\0'};
+static char status_ok_rsp[] = {033, 0133, 064, 0156, '\0'};
+static char garbage[] = {001, 002, 003, 004, '\0'};
+static char esc_garbage[] = {033, 002, 003, 004, '\0'};
+static char *ptr;
+
+static char getch(void)
+{
+	if (!ptr || *ptr == '\0')
+		return -ERR;
+	return *ptr++;
+}
+
+#include "ui/ncurses/console-codes.c"
+
+int main(void)
+{
+	void *ctx;
+	char *seq, *confused;
+
+	ctx = talloc_new(NULL);
+
+	ptr = &identify_rsp[1];
+	printf("Identity response\n");
+	seq = handle_control_sequence(ctx, identify_rsp[0]);
+	assert(strncmp(seq, identify_rsp, strlen(identify_rsp)) == 0);
+
+	printf("DECDWL\n");
+	ptr = &decdwl[1];
+	seq = handle_control_sequence(ctx, decdwl[0]);
+	assert(strncmp(seq, decdwl, strlen(decdwl)) == 0);
+
+	printf("Attributes\n");
+	ptr = &attrs[1];
+	seq = handle_control_sequence(ctx, attrs[0]);
+	assert(strncmp(seq, attrs, strlen(attrs)) == 0);
+
+	printf("Reset Cursor\n");
+	ptr = &cursor[1];
+	seq = handle_control_sequence(ctx, cursor[0]);
+	assert(strncmp(seq, cursor, strlen(cursor)) == 0);
+
+	printf("Confidence Test\n");
+	ptr = &conf_test[1];
+	seq = handle_control_sequence(ctx, conf_test[0]);
+	assert(strncmp(seq, conf_test, strlen(conf_test)) == 0);
+
+	printf("Status\n");
+	ptr = &status[1];
+	seq = handle_control_sequence(ctx, status[0]);
+	assert(strncmp(seq, status, strlen(status)) == 0);
+
+	printf("Erase Screen\n");
+	ptr = &erase_screen[1];
+	seq = handle_control_sequence(ctx, erase_screen[0]);
+	assert(strncmp(seq, erase_screen, strlen(erase_screen)) == 0);
+
+	printf("Status Response\n");
+	ptr = &status_ok_rsp[1];
+	seq = handle_control_sequence(ctx, status_ok_rsp[0]);
+	assert(strncmp(seq, status_ok_rsp, strlen(status_ok_rsp)) == 0);
+
+	printf("Garbage\n");
+	ptr = &garbage[1];
+	seq = handle_control_sequence(ctx, garbage[0]);
+	assert(seq == NULL);
+
+	printf("ESC then Garbage\n");
+	ptr = &esc_garbage[1];
+	confused = talloc_asprintf(ctx, "%c%c...", 033, 002);
+	seq = handle_control_sequence(ctx, esc_garbage[0]);
+	assert(strncmp(seq, confused, strlen(confused)) == 0);
+
+	talloc_free(ctx);
+	return EXIT_SUCCESS;
+}
diff --git a/ui/ncurses/Makefile.am b/ui/ncurses/Makefile.am
index 40e11b8..3bc5254 100644
--- a/ui/ncurses/Makefile.am
+++ b/ui/ncurses/Makefile.am
@@ -24,6 +24,8 @@  ui_ncurses_libpbnc_la_SOURCES = \
 	ui/ncurses/nc-config.c \
 	ui/ncurses/nc-config.h \
 	ui/ncurses/nc-config-help.c \
+	ui/ncurses/console-codes.c \
+	ui/ncurses/console-codes.h \
 	ui/ncurses/nc-cui.c \
 	ui/ncurses/nc-cui.h \
 	ui/ncurses/nc-cui-help.c \
diff --git a/ui/ncurses/console-codes.c b/ui/ncurses/console-codes.c
new file mode 100644
index 0000000..68cdfab
--- /dev/null
+++ b/ui/ncurses/console-codes.c
@@ -0,0 +1,178 @@ 
+/*
+ *  Copyright (C) 2017 IBM Corporation
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; version 2 of the License.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ */
+
+#if defined(HAVE_CONFIG_H)
+#include "config.h"
+#endif
+
+#include <ctype.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdbool.h>
+
+#include "talloc/talloc.h"
+
+#ifndef PETITBOOT_TEST
+#include "log/log.h"
+#include "nc-scr.h"
+#endif
+
+#include "console-codes.h"
+
+#define ESC_CHAR			033
+#define CSI_CHAR			'['
+#define INTER_CHAR_START		040
+#define INTER_CHAR_END			057
+#define ESC_SEQUENCE_FINAL_START	060
+#define ESC_SEQUENCE_FINAL_END		0176
+#define CTRL_SEQUENCE_FINAL_START	0100
+#define CTRL_SEQUENCE_FINAL_END		0176
+#define DEC_PARAMETER			077
+
+enum console_sequence_state {
+	CONSOLE_STATE_START,
+	CONSOLE_STATE_ESC_SEQ,
+	CONSOLE_STATE_CTRL_SEQ_START,
+	CONSOLE_STATE_CTRL_SEQ,
+	CONSOLE_STATE_DONE,
+	CONSOLE_STATE_CONFUSED,
+};
+
+static inline bool is_intermediate(char c)
+{
+	return c > INTER_CHAR_START && c < INTER_CHAR_END;
+}
+
+static inline bool is_parameter(char c)
+{
+	return (c >= 060 && c <= 071) || c == 073;
+}
+
+static inline bool is_escape_final(char c)
+{
+	return c >= ESC_SEQUENCE_FINAL_START && c < ESC_SEQUENCE_FINAL_END;
+}
+
+static inline bool is_control_final(char c)
+{
+	return c >= CTRL_SEQUENCE_FINAL_START && c <= CTRL_SEQUENCE_FINAL_END;
+}
+
+static signed char console_sequence_getch(char **sequence)
+{
+	signed char c = getch();
+
+	if (c != ERR)
+		*sequence = talloc_asprintf_append(*sequence, "%c", c);
+	return c;
+}
+
+/*
+ * Catch terminal control sequences that have accidentally been sent to
+ * Petitboot. These are of the form
+ * 	ESC I .. I F
+ * where I is an Intermediate Character and F is a Final Character, eg:
+ * 	ESC ^ [ ? 1 ; 0 c
+ * or	ESC # 6
+ *
+ * This is based off the definitions provided by
+ * https://vt100.net/docs/vt100-ug/contents.html
+ */
+char *handle_control_sequence(void *ctx, char start)
+{
+	enum console_sequence_state state = CONSOLE_STATE_START;
+	bool in_sequence = true;
+	signed char c;
+	char *seq;
+
+	if (start != ESC_CHAR) {
+		pb_log("%s: Called with non-escape character: 0%o\n",
+				__func__, start);
+		return NULL;
+	}
+
+	seq = talloc_asprintf(ctx, "%c", start);
+
+	while (in_sequence) {
+		switch (state) {
+		case CONSOLE_STATE_START:
+			c = console_sequence_getch(&seq);
+			if (c == CSI_CHAR)
+				state = CONSOLE_STATE_CTRL_SEQ_START;
+			else if (is_intermediate(c))
+				state = CONSOLE_STATE_ESC_SEQ;
+			else if (is_escape_final(c))
+				state = CONSOLE_STATE_DONE;
+			else if (c != ERR) {
+				/* wait on c == ERR */
+				pb_debug("Unexpected start: \\x%x\n", c);
+				state = CONSOLE_STATE_CONFUSED;
+			}
+			break;
+		case CONSOLE_STATE_ESC_SEQ:
+			c = console_sequence_getch(&seq);
+			if (is_intermediate(c))
+				state = CONSOLE_STATE_ESC_SEQ;
+			else if (is_escape_final(c))
+				state = CONSOLE_STATE_DONE;
+			else if (c != ERR) {
+				/* wait on c == ERR */
+				pb_debug("Unexpected character after intermediate: \\x%x\n",
+						c);
+				state = CONSOLE_STATE_CONFUSED;
+			}
+			break;
+		case CONSOLE_STATE_CTRL_SEQ_START:
+			c = console_sequence_getch(&seq);
+			if (is_intermediate(c) || is_parameter(c) ||
+					c == DEC_PARAMETER)
+				state = CONSOLE_STATE_CTRL_SEQ;
+			else if (is_control_final(c))
+				state = CONSOLE_STATE_DONE;
+			else if (c != ERR) {
+				/* wait on c == ERR */
+				pb_debug("Unexpected character in param string:  \\x%x\n",
+						c);
+				state = CONSOLE_STATE_CONFUSED;
+			}
+			break;
+		case CONSOLE_STATE_CTRL_SEQ:
+			c = console_sequence_getch(&seq);
+			if (is_intermediate(c) || is_parameter(c))
+				state = CONSOLE_STATE_CTRL_SEQ;
+			else if (is_control_final(c))
+				state = CONSOLE_STATE_DONE;
+			else if (c != ERR) {
+				/* wait on c == ERR */
+				pb_debug("Unexpected character in param string:  \\x%x\n",
+						c);
+				state = CONSOLE_STATE_CONFUSED;
+			}
+			break;
+		case CONSOLE_STATE_DONE:
+			in_sequence = false;
+			break;
+		case CONSOLE_STATE_CONFUSED:
+			/* fall-through */
+		default:
+			pb_debug("We got lost interpreting a control sequence!\n");
+			seq = talloc_asprintf_append(seq, "...");
+			in_sequence = false;
+			break;
+		};
+	}
+
+	return seq;
+}
diff --git a/ui/ncurses/console-codes.h b/ui/ncurses/console-codes.h
new file mode 100644
index 0000000..6de54a7
--- /dev/null
+++ b/ui/ncurses/console-codes.h
@@ -0,0 +1,20 @@ 
+/*
+ *  Copyright (C) 2017 IBM Corporation
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; version 2 of the License.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ */
+
+#if !defined(_PB_UI_CONSOLE_CODES)
+#define _PB_UI_CONSOLE_CODES
+
+char *handle_control_sequence(void *ctx, char start);
+
+#endif
diff --git a/ui/ncurses/nc-cui.c b/ui/ncurses/nc-cui.c
index 6ced24c..8060510 100644
--- a/ui/ncurses/nc-cui.c
+++ b/ui/ncurses/nc-cui.c
@@ -21,6 +21,7 @@ 
 #endif
 
 #include <assert.h>
+#include <ctype.h>
 #include <errno.h>
 #include <stdlib.h>
 #include <string.h>
@@ -45,6 +46,7 @@ 
 #include "nc-statuslog.h"
 #include "nc-subset.h"
 #include "nc-plugin.h"
+#include "console-codes.h"
 
 extern const struct help_text main_menu_help_text;
 extern const struct help_text plugin_menu_help_text;
@@ -524,6 +526,9 @@  static bool process_global_keys(struct cui *cui, int key)
 static int cui_process_key(void *arg)
 {
 	struct cui *cui = cui_from_arg(arg);
+	unsigned int i;
+	char *sequence;
+	int grab;
 
 	assert(cui->current);
 
@@ -535,6 +540,29 @@  static int cui_process_key(void *arg)
 		if (c == ERR)
 			break;
 
+		if (c == 27) {
+			/*
+			 * If this is a console code sequence try to parse it
+			 * and don't treat this as a key press.
+			 */
+			grab = getch();
+			if (grab != ERR && grab != 27) {
+				ungetch(grab);
+				pb_debug("%s: Caught unhandled command sequence\n",
+						__func__);
+				sequence = handle_control_sequence(cui, c);
+				pb_debug("Caught sequence ");
+				if (sequence) {
+					pb_debug("(%zu): ", strlen(sequence));
+					for (i = 0; i < strlen(sequence); i++)
+						pb_debug("0%o ", sequence[i]);
+					pb_debug("\n");
+				} else
+					pb_debug("(0): (none)\n");
+				continue;
+			}
+		}
+
 		if (!cui->has_input) {
 			cui->has_input = true;
 			if (cui->client) {