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Systemd is causing mislabeled devices to be created and then attempting to read them.

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On 07/28/2010 05:57 AM, Kay Sievers wrote:
> On Wed, Jul 28, 2010 at 11:43, Lennart Poettering
> <lennart@poettering.net> wrote:
>> On Mon, 26.07.10 16:42, Daniel J Walsh (dwalsh@redhat.com) wrote:
>>> tcontext=system_u:object_r:device_t:s0 tclass=chr_file
>>> type=1400 audit(1280174589.476:7): avc:  denied  { read } for  pid=1
>>> comm="systemd" name="autofs" dev=devtmpfs ino=9482
>>> scontext=system_u:system_r:init_t:s0
>>> tcontext=system_u:object_r:device_t:s0 tclass=chr_file
>>> type=1400 audit(1280174589.476:8): avc:  denied  { read } for  pid=1
>>> comm="systemd" name="autofs" dev=devtmpfs ino=9482
>>> scontext=system_u:system_r:init_t:s0
>>> tcontext=system_u:object_r:device_t:s0 tclass=chr_file
>>>
>>> Lennart, we talked about this earlier.  I think this is caused by the
>>> modprobe calls to create /dev/autofs.  Since udev is not created at the
>>> point that init loads the kernel modules, the devices get created with
>>> the wrong label.  Once udev starts the labels get fixed.
>>>
>>> I can allow init_t to read device_t chr_files.
>>
>> Hmm, I think a cleaner fix would be to make systemd relabel this device
>> properly before accessing it? Given that this is only one device this
>> should not be a problem for us to maintain, I think? How would the
>> fixing of the label work? Would we have to spawn restorecon for this, or
>> can we actually do this in C without too much work?
>
> I guess we can just do what udev is doing, and call setfilecon(), with
> a context of an earlier matchpathcon().
>
> Kay
> _______________________________________________
> systemd-devel mailing list
> systemd-devel@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/systemd-devel

Here is the updated patch with a fix for the labeling of /dev/autofs
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This commit is contained in:
Daniel J Walsh 2010-07-28 09:39:54 -04:00 committed by Lennart Poettering
parent 8b33e5ca72
commit 56cf987fe7
8 changed files with 293 additions and 99 deletions
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21
configure.ac
View file

@ -105,15 +105,26 @@ PKG_CHECK_MODULES(DBUS, [ dbus-1 >= 1.3.2 ])
AC_SUBST(DBUS_CFLAGS)
AC_SUBST(DBUS_LIBS)
PKG_CHECK_MODULES(SELINUX, [ libselinux ])
AC_SUBST(SELINUX_CFLAGS)
AC_SUBST(SELINUX_LIBS)
AC_SEARCH_LIBS([is_selinux_enabled], [selinux], [], [AC_MSG_ERROR([*** libselinux library not found])])
PKG_CHECK_MODULES(DBUSGLIB, [ dbus-glib-1 ])
AC_SUBST(DBUSGLIB_CFLAGS)
AC_SUBST(DBUSGLIB_LIBS)
have_selinux=no
AC_ARG_ENABLE(selinux, AS_HELP_STRING([--disable-selinux], [Disable optional SELINUX support]))
if test "x$enable_selinux" != "xno"; then
# not using PKG_CHECK_MODULES as for some reason libselinux didn't
# install any pkg-config modules here
AC_SEARCH_LIBS([getcon], [selinux],
[AC_DEFINE(HAVE_SELINUX, 1, [Define if SELINUX is available]) have_selinux=yes],
have_selinux=no)
AC_SUBST(SELINUX_CFLAGS)
AC_SUBST(SELINUX_LIBS)
if test "x$have_selinux" = xno -a "x$enable_selinux" = xyes; then
AC_MSG_ERROR([*** selinux support requested but libraries not found])
fi
fi
AM_CONDITIONAL(HAVE_SELINUX, [test "$have_selinux" = "yes"])
AC_ARG_ENABLE([tcpwrap],
AS_HELP_STRING([--disable-tcpwrap],[Disable optional TCP wrappers support]),
[case "${enableval}" in

2
src/automount.c
View file

@ -304,6 +304,8 @@ static int open_dev_autofs(Manager *m) {
if (m->dev_autofs_fd >= 0)
return m->dev_autofs_fd;
label_fix("/dev/autofs");
if ((m->dev_autofs_fd = open("/dev/autofs", O_CLOEXEC|O_RDONLY)) < 0) {
log_error("Failed to open /dev/autofs: %s", strerror(errno));
return -errno;

5
src/main.c
View file

@ -836,6 +836,9 @@ int main(int argc, char *argv[]) {
return 1;
}
if (label_init() < 0)
goto finish;
log_show_color(isatty(STDERR_FILENO) > 0);
log_show_location(false);
log_set_max_level(LOG_INFO);
@ -1113,5 +1116,7 @@ finish:
if (getpid() == 1)
freeze();
label_finish();
return retval;
}

13
src/socket-util.c
View file

@ -29,7 +29,6 @@
#include <net/if.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <selinux/selinux.h>
#include "macro.h"
#include "util.h"
@ -306,7 +305,7 @@ int socket_address_listen(
bool free_bind,
mode_t directory_mode,
mode_t socket_mode,
security_context_t scon,
const char *label,
int *ret) {
int r, fd, one;
@ -316,16 +315,14 @@ int socket_address_listen(
if ((r = socket_address_verify(a)) < 0)
return r;
if (setsockcreatecon(scon) < 0) {
log_error("Failed to set SELinux context (%s) on socket: %m", scon);
if (security_getenforce() == 1)
return -errno;
}
r = label_socket_set(label);
if (r < 0)
return r;
fd = socket(socket_address_family(a), a->type | SOCK_NONBLOCK | SOCK_CLOEXEC, 0);
r = fd < 0 ? -errno : 0;
setsockcreatecon(NULL);
label_socket_clear();
if (r < 0)
return r;

3
src/socket-util.h
View file

@ -26,7 +26,6 @@
#include <netinet/in.h>
#include <sys/un.h>
#include <net/if.h>
#include <selinux/selinux.h>
#include "macro.h"
#include "util.h"
@ -72,7 +71,7 @@ int socket_address_listen(
bool free_bind,
mode_t directory_mode,
mode_t socket_mode,
security_context_t scon,
const char *label,
int *ret);
bool socket_address_is(const SocketAddress *a, const char *s, int type);

94
src/socket.c
View file

@ -27,7 +27,6 @@
#include <sys/epoll.h>
#include <signal.h>
#include <arpa/inet.h>
#include <selinux/selinux.h>
#include "unit.h"
#include "socket.h"
@ -653,89 +652,25 @@ static void socket_apply_fifo_options(Socket *s, int fd) {
log_warning("F_SETPIPE_SZ: %m");
}
static int selinux_getconfromexe(
const char *exe,
security_context_t *newcon) {
security_context_t mycon = NULL, fcon = NULL;
security_class_t sclass;
int r = 0;
r = getcon(&mycon);
if (r < 0)
goto fail;
r = getfilecon(exe, &fcon);
if (r < 0)
goto fail;
sclass = string_to_security_class("process");
r = security_compute_create(mycon, fcon, sclass, newcon);
fail:
if (r < 0)
r = -errno;
freecon(mycon);
freecon(fcon);
return r;
}
static int selinux_getfileconfrompath(
const security_context_t scon,
const char *path,
const char *class,
security_context_t *fcon) {
security_context_t dir_con = NULL;
security_class_t sclass;
int r = 0;
r = getfilecon(path, &dir_con);
if (r >= 0) {
r = -1;
if ((sclass = string_to_security_class(class)) != 0)
r = security_compute_create(scon, dir_con, sclass, fcon);
}
if (r < 0)
r = -errno;
freecon(dir_con);
return r;
}
static int fifo_address_create(
const char *path,
mode_t directory_mode,
mode_t socket_mode,
security_context_t scon,
const char *label,
int *_fd) {
int fd = -1, r = 0;
struct stat st;
mode_t old_mask;
security_context_t filecon = NULL;
assert(path);
assert(_fd);
mkdir_parents(path, directory_mode);
if (scon) {
if (scon && ((r = selinux_getfileconfrompath(scon, path, "fifo_file", &filecon)) == 0)) {
r = setfscreatecon(filecon);
if (r < 0) {
log_error("Failed to set SELinux file context (%s) on %s: %m", scon, path);
r = -errno;
}
freecon(filecon);
}
if (r < 0 && security_getenforce() == 1)
goto fail;
}
if ((r = label_fifofile_set(label, path)) < 0)
goto fail;
/* Enforce the right access mode for the fifo */
old_mask = umask(~ socket_mode);
@ -756,7 +691,7 @@ static int fifo_address_create(
goto fail;
}
setfscreatecon(NULL);
label_file_clear();
if (fstat(fd, &st) < 0) {
r = -errno;
@ -776,7 +711,8 @@ static int fifo_address_create(
return 0;
fail:
setfscreatecon(NULL);
label_file_clear();
if (fd >= 0)
close_nointr_nofail(fd);
@ -786,20 +722,16 @@ fail:
static int socket_open_fds(Socket *s) {
SocketPort *p;
int r;
security_context_t scon = NULL;
char *label = NULL;
assert(s);
if ((r = socket_instantiate_service(s)) < 0)
return r;
if (selinux_getconfromexe(s->service->exec_command[SERVICE_EXEC_START]->path, &scon) < 0) {
log_error("Failed to get SELinux exec context for %s \n", s->service->exec_command[SERVICE_EXEC_START]->path);
if (security_getenforce() == 1)
return -errno;
}
if ((r = label_get_socket_label_from_exe(s->service->exec_command[SERVICE_EXEC_START]->path, &label)) < 0)
return r;
log_debug("SELinux Socket context for %s set to %s\n", s->service->exec_command[SERVICE_EXEC_START]->path, scon);
LIST_FOREACH(port, p, s->ports) {
if (p->fd >= 0)
@ -815,7 +747,7 @@ static int socket_open_fds(Socket *s) {
s->free_bind,
s->directory_mode,
s->socket_mode,
scon,
label,
&p->fd)) < 0)
goto rollback;
@ -827,7 +759,7 @@ static int socket_open_fds(Socket *s) {
p->path,
s->directory_mode,
s->socket_mode,
scon,
label,
&p->fd)) < 0)
goto rollback;
@ -837,12 +769,12 @@ static int socket_open_fds(Socket *s) {
assert_not_reached("Unknown port type");
}
freecon(scon);
label_free(label);
return 0;
rollback:
socket_close_fds(s);
freecon(scon);
label_free(label);
return r;
}

244
src/util.c
View file

@ -56,6 +56,244 @@
#include "log.h"
#include "strv.h"
#if HAVE_SELINUX
#include <selinux/selinux.h>
#include <selinux/label.h>
static struct selabel_handle *label_hnd = NULL;
static inline int use_selinux(void) {
static int use_selinux_ind = -1;
if (use_selinux_ind == -1)
use_selinux_ind = (is_selinux_enabled() == 1);
return use_selinux_ind;
}
static int label_get_file_label_from_path(
const char *label,
const char *path,
const char *class,
security_context_t *fcon) {
security_context_t dir_con = NULL;
security_class_t sclass;
int r = 0;
r = getfilecon(path, &dir_con);
if (r >= 0) {
r = -1;
if ((sclass = string_to_security_class(class)) != 0)
r = security_compute_create((security_context_t) label, dir_con, sclass, fcon);
}
if (r < 0)
r = -errno;
freecon(dir_con);
return r;
}
#endif
int label_init(void) {
int r = 0;
#if HAVE_SELINUX
if (use_selinux()) {
label_hnd = selabel_open(SELABEL_CTX_FILE, NULL, 0);
if (!label_hnd) {
log_full(security_getenforce() == 1 ? LOG_ERR : LOG_DEBUG, "Failed to initialize SELinux context: %m");
r = (security_getenforce() == 1) ? -errno : 0;
}
}
#endif
return r;
}
int label_fix(const char *path) {
int r = 0;
#if HAVE_SELINUX
struct stat st;
security_context_t fcon;
if (use_selinux()) {
r = lstat(path, &st);
if (r == 0) {
r = selabel_lookup_raw(label_hnd, &fcon, path, st.st_mode);
if (r == 0) {
r = setfilecon(path, fcon);
freecon(fcon);
}
}
if (r < 0) {
log_error("Unable to fix label of %s: %m", path);
r = (security_getenforce() == 1) ? -errno : 0;
}
}
#endif
return r;
}
void label_finish(void) {
#if HAVE_SELINUX
if (use_selinux())
selabel_close(label_hnd);
#endif
}
int label_get_socket_label_from_exe(
const char *exe,
char **label) {
int r = 0;
#if HAVE_SELINUX
security_context_t mycon = NULL, fcon = NULL;
security_class_t sclass;
r = getcon(&mycon);
if (r < 0)
goto fail;
r = getfilecon(exe, &fcon);
if (r < 0)
goto fail;
sclass = string_to_security_class("process");
r = security_compute_create(mycon, fcon, sclass, (security_context_t *) label);
if (r == 0)
log_debug("SELinux Socket context for %s will be set to %s", exe, *label);
fail:
if (r< 0 && security_getenforce() == 1)
r = -errno;
freecon(mycon);
freecon(fcon);
#endif
return r;
}
int label_fifofile_set(const char *label, const char *path) {
int r = 0;
#if HAVE_SELINUX
security_context_t filecon = NULL;
if (use_selinux() && label) {
if (((r = label_get_file_label_from_path(label, path, "fifo_file", &filecon)) == 0)) {
if ((r = setfscreatecon(filecon)) < 0) {
log_error("Failed to set SELinux file context (%s) on %s: %m", label, path);
r = -errno;
}
freecon(filecon);
}
if (r < 0 && security_getenforce() == 0)
r = 0;
}
#endif
return r;
}
int label_socket_set(const char *label) {
#if HAVE_SELINUX
if (use_selinux() && setsockcreatecon((security_context_t) label) < 0) {
log_error("Failed to set SELinux context (%s) on socket: %m", label);
if (security_getenforce() == 1)
return -errno;
}
#endif
return 0;
}
void label_file_clear(void) {
#if HAVE_SELINUX
if (use_selinux())
setfscreatecon(NULL);
#endif
return;
}
void label_free(const char *label) {
#if HAVE_SELINUX
if (use_selinux())
freecon((security_context_t) label);
#endif
return;
}
void label_socket_clear(void) {
#if HAVE_SELINUX
if (use_selinux())
setsockcreatecon(NULL);
#endif
return;
}
static int label_mkdir(
const char *path,
mode_t mode) {
#if HAVE_SELINUX
int r;
security_context_t fcon = NULL;
if (use_selinux()) {
if (path[0] == '/') {
r = selabel_lookup_raw(label_hnd, &fcon, path, mode);
}
else {
char *cwd = NULL;
char *newpath = NULL;
cwd = getcwd(NULL,0);
if ((! cwd) || (asprintf(&newpath, "%s/%s",cwd,path) < 0)) {
free(cwd);
return -errno;
}
r = selabel_lookup_raw(label_hnd, &fcon, newpath, mode);
free(cwd);
free(newpath);
}
if (r == 0)
r = setfscreatecon(fcon);
if ((r < 0) && (errno != ENOENT)) {
log_error("Failed to set security context %s for %s", fcon, path);
if (security_getenforce() == 1)
goto finish;
}
}
r = mkdir(path, mode);
finish:
if (use_selinux()) {
setfscreatecon(NULL);
freecon(fcon);
}
return r;
#else
return mkdir(path, mode);
#endif
}
bool streq_ptr(const char *a, const char *b) {
/* Like streq(), but tries to make sense of NULL pointers */
@ -969,7 +1207,7 @@ char *file_in_same_dir(const char *path, const char *filename) {
int safe_mkdir(const char *path, mode_t mode, uid_t uid, gid_t gid) {
struct stat st;
if (mkdir(path, mode) >= 0)
if (label_mkdir(path, mode) >= 0)
if (chmod_and_chown(path, mode, uid, gid) < 0)
return -errno;
@ -1012,7 +1250,7 @@ int mkdir_parents(const char *path, mode_t mode) {
if (!(t = strndup(path, e - path)))
return -ENOMEM;
r = mkdir(t, mode);
r = label_mkdir(t, mode);
free(t);
if (r < 0 && errno != EEXIST)
@ -1028,7 +1266,7 @@ int mkdir_p(const char *path, mode_t mode) {
if ((r = mkdir_parents(path, mode)) < 0)
return r;
if (mkdir(path, mode) < 0 && errno != EEXIST)
if (label_mkdir(path, mode) < 0 && errno != EEXIST)
return -errno;
return 0;

10
src/util.h
View file

@ -360,4 +360,14 @@ int ip_tos_from_string(const char *s);
const char *signal_to_string(int i);
int signal_from_string(const char *s);
int label_init(void);
int label_fix(const char *path);
void label_finish(void);
int label_socket_set(const char *label);
void label_socket_clear(void);
int label_fifofile_set(const char *label, const char *path);
void label_file_clear(void);
void label_free(const char *label);
int label_get_socket_label_from_exe(const char *exe, char **label);
#endif