~kris/suckless

slock

a7afade1701a809f6a33b53525d59dd29b38d381 — Hiltjo Posthuma 10 years ago 65b8d52
clear passwords with explicit_bzero

Make sure to explicitly clear memory that is used for password input. memset
is often optimized out by the compiler.

Brought to attention by the OpenBSD community, see:
https://marc.info/?t=146989502600003&r=1&w=2
Thread subject: x11/slock: clear passwords with explicit_bzero

Changes:

- explicit_bzero.c import from libressl-portable.
- Makefile: add COMPATSRC for compatibility src.
- config.mk: add separate *BSD section in config.mk to simply uncomment it on
  these platforms.
5 files changed, 34 insertions(+), 5 deletions(-)

M Makefile
M config.mk
A explicit_bzero.c
M slock.c
A util.h
M Makefile => Makefile +3 -3
@@ 3,7 3,7 @@

include config.mk

SRC = slock.c
SRC = slock.c ${COMPATSRC}
OBJ = ${SRC:.c=.o}

all: options slock


@@ 35,8 35,8 @@ clean:
dist: clean
	@echo creating dist tarball
	@mkdir -p slock-${VERSION}
	@cp -R LICENSE Makefile README config.def.h config.mk ${SRC} slock.1 \
		slock-${VERSION}
	@cp -R LICENSE Makefile README config.def.h config.mk ${SRC} \
		explicit_bzero.c slock.1 slock-${VERSION}
	@tar -cf slock-${VERSION}.tar slock-${VERSION}
	@gzip slock-${VERSION}.tar
	@rm -rf slock-${VERSION}

M config.mk => config.mk +4 -0
@@ 18,9 18,13 @@ LIBS = -L/usr/lib -lc -lcrypt -L${X11LIB} -lX11 -lXext -lXrandr
CPPFLAGS = -DVERSION=\"${VERSION}\" -DHAVE_SHADOW_H
CFLAGS = -std=c99 -pedantic -Wall -Os ${INCS} ${CPPFLAGS}
LDFLAGS = -s ${LIBS}
COMPATSRC = explicit_bzero.c

# On *BSD remove -DHAVE_SHADOW_H from CPPFLAGS and add -DHAVE_BSD_AUTH
# On OpenBSD and Darwin remove -lcrypt from LIBS
#LIBS = -L/usr/lib -lc -L${X11LIB} -lX11 -lXext -lXrandr
#CPPFLAGS = -DVERSION=\"${VERSION}\" -DHAVE_BSD_AUTH -D_BSD_SOURCE
#COMPATSRC =

# compiler and linker
CC = cc

A explicit_bzero.c => explicit_bzero.c +19 -0
@@ 0,0 1,19 @@
/*	$OpenBSD: explicit_bzero.c,v 1.3 2014/06/21 02:34:26 matthew Exp $ */
/*
 * Public domain.
 * Written by Matthew Dempsky.
 */

#include <string.h>

__attribute__((weak)) void
__explicit_bzero_hook(void *buf, size_t len)
{
}

void
explicit_bzero(void *buf, size_t len)
{
	memset(buf, 0, len);
	__explicit_bzero_hook(buf, len);
}

M slock.c => slock.c +6 -2
@@ 23,6 23,8 @@
#include <bsd_auth.h>
#endif

#include "util.h"

enum {
	INIT,
	INPUT,


@@ 135,7 137,7 @@ readpw(Display *dpy, const char *pws)
	 * timeout. */
	while (running && !XNextEvent(dpy, &ev)) {
		if (ev.type == KeyPress) {
			buf[0] = 0;
			explicit_bzero(&buf, sizeof(buf));
			num = XLookupString(&ev.xkey, buf, sizeof(buf), &ksym, 0);
			if (IsKeypadKey(ksym)) {
				if (ksym == XK_KP_Enter)


@@ 161,14 163,16 @@ readpw(Display *dpy, const char *pws)
					XBell(dpy, 100);
					failure = True;
				}
				explicit_bzero(&passwd, sizeof(passwd));
				len = 0;
				break;
			case XK_Escape:
				explicit_bzero(&passwd, sizeof(passwd));
				len = 0;
				break;
			case XK_BackSpace:
				if (len)
					--len;
					passwd[len--] = 0;
				break;
			default:
				if (num && !iscntrl((int)buf[0]) && (len + num < sizeof(passwd))) {

A util.h => util.h +2 -0
@@ 0,0 1,2 @@
#undef explicit_bzero
void explicit_bzero(void *, size_t);