This fixes a format string vulnerabilty.
evdev_log_message() composes a format string consisting of a fixed
prefix (including the rendered device name) and the passed-in format
buffer. This format string is then passed with the arguments to the
actual log handler, which usually and eventually ends up being printf.
If the device name contains a printf-style format directive, these ended
up in the format string and thus get interpreted correctly, e.g. for a
device "Foo%sBar" the log message vs printf invocation ends up being:
evdev_log_message(device, "some message %s", "some argument");
printf("event9 - Foo%sBar: some message %s", "some argument");
This can enable an attacker to execute malicious code with the
privileges of the process using libinput.
To exploit this, an attacker needs to be able to create a kernel device
with a malicious name, e.g. through /dev/uinput or a Bluetooth device.
To fix this, convert any potential format directives in the device name
by duplicating percentages.
Pre-rendering the device to avoid the issue altogether would be nicer
but the current log level hooks do not easily allow for this. The device
name is the only user-controlled part of the format string.
A second potential issue is the sysname of the device which is also
sanitized.
This issue was found by Albin Eldstål-Ahrens and Benjamin Svensson from
Assured AB, and independently by Lukas Lamster.
Fixes #752
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
'test/litest-device-dell-canvas-totem-touch.c',
'test/litest-device-elantech-touchpad.c',
'test/litest-device-elan-tablet.c',
+ 'test/litest-device-format-string.c',
'test/litest-device-generic-pressurepad.c',
'test/litest-device-generic-singletouch.c',
'test/litest-device-gpio-keys.c',
struct libinput *libinput = seat->libinput;
struct evdev_device *device = NULL;
int rc;
- int fd;
+ int fd = -1;
int unhandled_device = 0;
const char *devnode = udev_device_get_devnode(udev_device);
- const char *sysname = udev_device_get_sysname(udev_device);
+ char *sysname = str_sanitize(udev_device_get_sysname(udev_device));
if (!devnode) {
log_info(libinput, "%s: no device node associated\n", sysname);
- return NULL;
+ goto err;
}
if (udev_device_should_be_ignored(udev_device)) {
log_debug(libinput, "%s: device is ignored\n", sysname);
- return NULL;
+ goto err;
}
/* Use non-blocking mode so that we can loop on read on
sysname,
devnode,
strerror(-fd));
- return NULL;
+ goto err;
}
if (!evdev_device_have_same_syspath(udev_device, fd))
goto err;
device = zalloc(sizeof *device);
+ device->sysname = sysname;
+ sysname = NULL;
libinput_device_init(&device->base, seat);
libinput_seat_ref(seat);
device->dispatch = NULL;
device->fd = fd;
device->devname = libevdev_get_name(device->evdev);
+ /* the log_prefix_name is used as part of a printf format string and
+ * must not contain % directives, see evdev_log_msg */
+ device->log_prefix_name = str_sanitize(device->devname);
device->scroll.threshold = 5.0; /* Default may be overridden */
device->scroll.direction_lock_threshold = 5.0; /* Default may be overridden */
device->scroll.direction = 0;
return device;
err:
- close_restricted(libinput, fd);
- if (device) {
- unhandled_device = device->seat_caps == 0;
- evdev_device_destroy(device);
+ if (fd >= 0) {
+ close_restricted(libinput, fd);
+ if (device) {
+ unhandled_device = device->seat_caps == 0;
+ evdev_device_destroy(device);
+ }
}
+ free(sysname);
+
return unhandled_device ? EVDEV_UNHANDLED_DEVICE : NULL;
}
const char *
evdev_device_get_sysname(struct evdev_device *device)
{
- return udev_device_get_sysname(device->udev_device);
+ return device->sysname;
}
const char *
if (device->base.group)
libinput_device_group_unref(device->base.group);
+ free(device->log_prefix_name);
+ free(device->sysname);
free(device->output_name);
filter_destroy(device->pointer.filter);
libinput_timer_destroy(&device->scroll.timer);
struct udev_device *udev_device;
char *output_name;
const char *devname;
+ char *log_prefix_name;
+ char *sysname;
bool was_removed;
int fd;
enum evdev_device_seat_capability seat_caps;
sizeof(buf),
"%-7s - %s%s%s",
evdev_device_get_sysname(device),
- (priority > LIBINPUT_LOG_PRIORITY_DEBUG) ? device->devname : "",
+ (priority > LIBINPUT_LOG_PRIORITY_DEBUG) ? device->log_prefix_name : "",
(priority > LIBINPUT_LOG_PRIORITY_DEBUG) ? ": " : "",
format);
sizeof(buf),
"%-7s - %s%s%s",
evdev_device_get_sysname(device),
- (priority > LIBINPUT_LOG_PRIORITY_DEBUG) ? device->devname : "",
+ (priority > LIBINPUT_LOG_PRIORITY_DEBUG) ? device->log_prefix_name : "",
(priority > LIBINPUT_LOG_PRIORITY_DEBUG) ? ": " : "",
format);
#include <xlocale.h>
#endif
+#include "util-macros.h"
+
static inline bool
streq(const char *str1, const char *str2)
{
char *
trunkname(const char *filename);
+
+/**
+ * Return a copy of str with all % converted to %% to make the string
+ * acceptable as printf format.
+ */
+static inline char *
+str_sanitize(const char *str)
+{
+ if (!str)
+ return NULL;
+
+ if (!strchr(str, '%'))
+ return strdup(str);
+
+ size_t slen = min(strlen(str), 512);
+ char *sanitized = zalloc(2 * slen + 1);
+ const char *src = str;
+ char *dst = sanitized;
+
+ for (size_t i = 0; i < slen; i++) {
+ if (*src == '%')
+ *dst++ = '%';
+ *dst++ = *src++;
+ }
+ *dst = '\0';
+
+ return sanitized;
+}
--- /dev/null
+
+/*
+ * Copyright © 2013 Red Hat, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#include "config.h"
+
+#include "litest.h"
+#include "litest-int.h"
+
+static struct input_id input_id = {
+ .bustype = 0x3,
+ .vendor = 0x0123,
+ .product = 0x0456,
+};
+
+static int events[] = {
+ EV_KEY, BTN_LEFT,
+ EV_KEY, BTN_RIGHT,
+ EV_KEY, BTN_MIDDLE,
+ EV_REL, REL_X,
+ EV_REL, REL_Y,
+ EV_REL, REL_WHEEL,
+ EV_REL, REL_WHEEL_HI_RES,
+ -1 , -1,
+};
+
+TEST_DEVICE("mouse-format-string",
+ .type = LITEST_MOUSE_FORMAT_STRING,
+ .features = LITEST_RELATIVE | LITEST_BUTTON | LITEST_WHEEL,
+ .interface = NULL,
+
+ .name = "Evil %s %d %x Mouse %p %",
+ .id = &input_id,
+ .absinfo = NULL,
+ .events = events,
+)
LITEST_SYNAPTICS_PRESSUREPAD,
LITEST_GENERIC_PRESSUREPAD,
LITEST_WACOM_ISDV4_524C_PEN,
+ LITEST_MOUSE_FORMAT_STRING,
};
#define LITEST_DEVICELESS -2
}
END_TEST
+START_TEST(strsanitize_test)
+{
+ struct strsanitize_test {
+ const char *string;
+ const char *expected;
+ } tests[] = {
+ { "foobar", "foobar" },
+ { "", "" },
+ { "%", "%%" },
+ { "%%%%", "%%%%%%%%" },
+ { "x %s", "x %%s" },
+ { "x %", "x %%" },
+ { "%sx", "%%sx" },
+ { "%s%s", "%%s%%s" },
+ { NULL, NULL },
+ };
+
+ for (struct strsanitize_test *t = tests; t->string; t++) {
+ char *sanitized = str_sanitize(t->string);
+ ck_assert_str_eq(sanitized, t->expected);
+ free(sanitized);
+ }
+}
+END_TEST
+
START_TEST(list_test_insert)
{
struct list_test {
tcase_add_test(tc, strstrip_test);
tcase_add_test(tc, strendswith_test);
tcase_add_test(tc, strstartswith_test);
+ tcase_add_test(tc, strsanitize_test);
tcase_add_test(tc, time_conversion);
tcase_add_test(tc, human_time);
projects / platform / upstream / libinput.git / commitdiff