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Systemd/src/login/pam_systemd.c
Lennart Poettering 4afd3348c7 tree-wide: expose "p"-suffix unref calls in public APIs to make gcc cleanup easy 
GLIB has recently started to officially support the gcc cleanup
attribute in its public API, hence let's do the same for our APIs.

With this patch we'll define an xyz_unrefp() call for each public
xyz_unref() call, to make it easy to use inside a
__attribute__((cleanup())) expression. Then, all code is ported over to
make use of this.

The new calls are also documented in the man pages, with examples how to
use them (well, I only added docs where the _unref() call itself already
had docs, and the examples, only cover sd_bus_unrefp() and
sd_event_unrefp()).

This also renames sd_lldp_free() to sd_lldp_unref(), since that's how we
tend to call our destructors these days.

Note that this defines no public macro that wraps gcc's attribute and
makes it easier to use. While I think it's our duty in the library to
make our stuff easy to use, I figure it's not our duty to make gcc's own
features easy to use on its own. Most likely, client code which wants to
make use of this should define its own:

       #define _cleanup_(function) __attribute__((cleanup(function)))

Or similar, to make the gcc feature easier to use.

Making this logic public has the benefit that we can remove three header
files whose only purpose was to define these functions internally.

See #2008.
2015-11-27 19:19:36 +01:00

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/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
/***
This file is part of systemd.
Copyright 2010 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <endian.h>
#include <errno.h>
#include <fcntl.h>
#include <pwd.h>
#include <security/_pam_macros.h>
#include <security/pam_ext.h>
#include <security/pam_misc.h>
#include <security/pam_modules.h>
#include <security/pam_modutil.h>
#include <sys/file.h>
#include "alloc-util.h"
#include "audit-util.h"
#include "bus-common-errors.h"
#include "bus-error.h"
#include "bus-util.h"
#include "def.h"
#include "fd-util.h"
#include "fileio.h"
#include "formats-util.h"
#include "hostname-util.h"
#include "login-util.h"
#include "macro.h"
#include "parse-util.h"
#include "socket-util.h"
#include "strv.h"
#include "terminal-util.h"
#include "util.h"
static int parse_argv(
pam_handle_t *handle,
int argc, const char **argv,
const char **class,
const char **type,
bool *debug) {
unsigned i;
assert(argc >= 0);
assert(argc == 0 || argv);
for (i = 0; i < (unsigned) argc; i++) {
if (startswith(argv[i], "class=")) {
if (class)
*class = argv[i] + 6;
} else if (startswith(argv[i], "type=")) {
if (type)
*type = argv[i] + 5;
} else if (streq(argv[i], "debug")) {
if (debug)
*debug = true;
} else if (startswith(argv[i], "debug=")) {
int k;
k = parse_boolean(argv[i] + 6);
if (k < 0)
pam_syslog(handle, LOG_WARNING, "Failed to parse debug= argument, ignoring.");
else if (debug)
*debug = k;
} else
pam_syslog(handle, LOG_WARNING, "Unknown parameter '%s', ignoring", argv[i]);
}
return 0;
}
static int get_user_data(
pam_handle_t *handle,
const char **ret_username,
struct passwd **ret_pw) {
const char *username = NULL;
struct passwd *pw = NULL;
int r;
assert(handle);
assert(ret_username);
assert(ret_pw);
r = pam_get_user(handle, &username, NULL);
if (r != PAM_SUCCESS) {
pam_syslog(handle, LOG_ERR, "Failed to get user name.");
return r;
}
if (isempty(username)) {
pam_syslog(handle, LOG_ERR, "User name not valid.");
return PAM_AUTH_ERR;
}
pw = pam_modutil_getpwnam(handle, username);
if (!pw) {
pam_syslog(handle, LOG_ERR, "Failed to get user data.");
return PAM_USER_UNKNOWN;
}
*ret_pw = pw;
*ret_username = username;
return PAM_SUCCESS;
}
static int get_seat_from_display(const char *display, const char **seat, uint32_t *vtnr) {
union sockaddr_union sa = {
.un.sun_family = AF_UNIX,
};
_cleanup_free_ char *p = NULL, *tty = NULL;
_cleanup_close_ int fd = -1;
struct ucred ucred;
int v, r;
assert(display);
assert(vtnr);
/* We deduce the X11 socket from the display name, then use
* SO_PEERCRED to determine the X11 server process, ask for
* the controlling tty of that and if it's a VC then we know
* the seat and the virtual terminal. Sounds ugly, is only
* semi-ugly. */
r = socket_from_display(display, &p);
if (r < 0)
return r;
strncpy(sa.un.sun_path, p, sizeof(sa.un.sun_path)-1);
fd = socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0);
if (fd < 0)
return -errno;
if (connect(fd, &sa.sa, offsetof(struct sockaddr_un, sun_path) + strlen(sa.un.sun_path)) < 0)
return -errno;
r = getpeercred(fd, &ucred);
if (r < 0)
return r;
r = get_ctty(ucred.pid, NULL, &tty);
if (r < 0)
return r;
v = vtnr_from_tty(tty);
if (v < 0)
return v;
else if (v == 0)
return -ENOENT;
if (seat)
*seat = "seat0";
*vtnr = (uint32_t) v;
return 0;
}
static int export_legacy_dbus_address(
pam_handle_t *handle,
uid_t uid,
const char *runtime) {
_cleanup_free_ char *s = NULL;
int r = PAM_BUF_ERR;
if (is_kdbus_available()) {
if (asprintf(&s, KERNEL_USER_BUS_ADDRESS_FMT ";" UNIX_USER_BUS_ADDRESS_FMT, uid, runtime) < 0)
goto error;
} else {
/* FIXME: We *really* should move the access() check into the
* daemons that spawn dbus-daemon, instead of forcing
* DBUS_SESSION_BUS_ADDRESS= here. */
s = strjoin(runtime, "/bus", NULL);
if (!s)
goto error;
if (access(s, F_OK) < 0)
return PAM_SUCCESS;
s = mfree(s);
if (asprintf(&s, UNIX_USER_BUS_ADDRESS_FMT, runtime) < 0)
goto error;
}
r = pam_misc_setenv(handle, "DBUS_SESSION_BUS_ADDRESS", s, 0);
if (r != PAM_SUCCESS)
goto error;
return PAM_SUCCESS;
error:
pam_syslog(handle, LOG_ERR, "Failed to set bus variable.");
return r;
}
_public_ PAM_EXTERN int pam_sm_open_session(
pam_handle_t *handle,
int flags,
int argc, const char **argv) {
_cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
_cleanup_(sd_bus_message_unrefp) sd_bus_message *reply = NULL;
const char
*username, *id, *object_path, *runtime_path,
*service = NULL,
*tty = NULL, *display = NULL,
*remote_user = NULL, *remote_host = NULL,
*seat = NULL,
*type = NULL, *class = NULL,
*class_pam = NULL, *type_pam = NULL, *cvtnr = NULL, *desktop = NULL;
_cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
int session_fd = -1, existing, r;
bool debug = false, remote;
struct passwd *pw;
uint32_t vtnr = 0;
uid_t original_uid;
assert(handle);
/* Make this a NOP on non-logind systems */
if (!logind_running())
return PAM_SUCCESS;
if (parse_argv(handle,
argc, argv,
&class_pam,
&type_pam,
&debug) < 0)
return PAM_SESSION_ERR;
if (debug)
pam_syslog(handle, LOG_DEBUG, "pam-systemd initializing");
r = get_user_data(handle, &username, &pw);
if (r != PAM_SUCCESS) {
pam_syslog(handle, LOG_ERR, "Failed to get user data.");
return r;
}
/* Make sure we don't enter a loop by talking to
* systemd-logind when it is actually waiting for the
* background to finish start-up. If the service is
* "systemd-user" we simply set XDG_RUNTIME_DIR and
* leave. */
pam_get_item(handle, PAM_SERVICE, (const void**) &service);
if (streq_ptr(service, "systemd-user")) {
_cleanup_free_ char *rt = NULL;
if (asprintf(&rt, "/run/user/"UID_FMT, pw->pw_uid) < 0)
return PAM_BUF_ERR;
r = pam_misc_setenv(handle, "XDG_RUNTIME_DIR", rt, 0);
if (r != PAM_SUCCESS) {
pam_syslog(handle, LOG_ERR, "Failed to set runtime dir.");
return r;
}
r = export_legacy_dbus_address(handle, pw->pw_uid, rt);
if (r != PAM_SUCCESS)
return r;
return PAM_SUCCESS;
}
/* Otherwise, we ask logind to create a session for us */
pam_get_item(handle, PAM_XDISPLAY, (const void**) &display);
pam_get_item(handle, PAM_TTY, (const void**) &tty);
pam_get_item(handle, PAM_RUSER, (const void**) &remote_user);
pam_get_item(handle, PAM_RHOST, (const void**) &remote_host);
seat = pam_getenv(handle, "XDG_SEAT");
if (isempty(seat))
seat = getenv("XDG_SEAT");
cvtnr = pam_getenv(handle, "XDG_VTNR");
if (isempty(cvtnr))
cvtnr = getenv("XDG_VTNR");
type = pam_getenv(handle, "XDG_SESSION_TYPE");
if (isempty(type))
type = getenv("XDG_SESSION_TYPE");
if (isempty(type))
type = type_pam;
class = pam_getenv(handle, "XDG_SESSION_CLASS");
if (isempty(class))
class = getenv("XDG_SESSION_CLASS");
if (isempty(class))
class = class_pam;
desktop = pam_getenv(handle, "XDG_SESSION_DESKTOP");
if (isempty(desktop))
desktop = getenv("XDG_SESSION_DESKTOP");
tty = strempty(tty);
if (strchr(tty, ':')) {
/* A tty with a colon is usually an X11 display,
* placed there to show up in utmp. We rearrange
* things and don't pretend that an X display was a
* tty. */
if (isempty(display))
display = tty;
tty = NULL;
} else if (streq(tty, "cron")) {
/* cron has been setting PAM_TTY to "cron" for a very
* long time and it probably shouldn't stop doing that
* for compatibility reasons. */
type = "unspecified";
class = "background";
tty = NULL;
} else if (streq(tty, "ssh")) {
/* ssh has been setting PAM_TTY to "ssh" for a very
* long time and probably shouldn't stop doing that
* for compatibility reasons. */
type ="tty";
class = "user";
tty = NULL;
}
/* If this fails vtnr will be 0, that's intended */
if (!isempty(cvtnr))
(void) safe_atou32(cvtnr, &vtnr);
if (!isempty(display) && !vtnr) {
if (isempty(seat))
get_seat_from_display(display, &seat, &vtnr);
else if (streq(seat, "seat0"))
get_seat_from_display(display, NULL, &vtnr);
}
if (seat && !streq(seat, "seat0") && vtnr != 0) {
pam_syslog(handle, LOG_DEBUG, "Ignoring vtnr %"PRIu32" for %s which is not seat0", vtnr, seat);
vtnr = 0;
}
if (isempty(type))
type = !isempty(display) ? "x11" :
!isempty(tty) ? "tty" : "unspecified";
if (isempty(class))
class = streq(type, "unspecified") ? "background" : "user";
remote = !isempty(remote_host) && !is_localhost(remote_host);
/* Talk to logind over the message bus */
r = sd_bus_open_system(&bus);
if (r < 0) {
pam_syslog(handle, LOG_ERR, "Failed to connect to system bus: %s", strerror(-r));
return PAM_SESSION_ERR;
}
if (debug)
pam_syslog(handle, LOG_DEBUG, "Asking logind to create session: "
"uid="UID_FMT" pid="PID_FMT" service=%s type=%s class=%s desktop=%s seat=%s vtnr=%"PRIu32" tty=%s display=%s remote=%s remote_user=%s remote_host=%s",
pw->pw_uid, getpid(),
strempty(service),
type, class, strempty(desktop),
strempty(seat), vtnr, strempty(tty), strempty(display),
yes_no(remote), strempty(remote_user), strempty(remote_host));
r = sd_bus_call_method(bus,
"org.freedesktop.login1",
"/org/freedesktop/login1",
"org.freedesktop.login1.Manager",
"CreateSession",
&error,
&reply,
"uusssssussbssa(sv)",
(uint32_t) pw->pw_uid,
(uint32_t) getpid(),
service,
type,
class,
desktop,
seat,
vtnr,
tty,
display,
remote,
remote_user,
remote_host,
0);
if (r < 0) {
if (sd_bus_error_has_name(&error, BUS_ERROR_SESSION_BUSY)) {
pam_syslog(handle, LOG_DEBUG, "Cannot create session: %s", bus_error_message(&error, r));
return PAM_SUCCESS;
} else {
pam_syslog(handle, LOG_ERR, "Failed to create session: %s", bus_error_message(&error, r));
return PAM_SYSTEM_ERR;
}
}
r = sd_bus_message_read(reply,
"soshusub",
&id,
&object_path,
&runtime_path,
&session_fd,
&original_uid,
&seat,
&vtnr,
&existing);
if (r < 0) {
pam_syslog(handle, LOG_ERR, "Failed to parse message: %s", strerror(-r));
return PAM_SESSION_ERR;
}
if (debug)
pam_syslog(handle, LOG_DEBUG, "Reply from logind: "
"id=%s object_path=%s runtime_path=%s session_fd=%d seat=%s vtnr=%u original_uid=%u",
id, object_path, runtime_path, session_fd, seat, vtnr, original_uid);
r = pam_misc_setenv(handle, "XDG_SESSION_ID", id, 0);
if (r != PAM_SUCCESS) {
pam_syslog(handle, LOG_ERR, "Failed to set session id.");
return r;
}
if (original_uid == pw->pw_uid) {
/* Don't set $XDG_RUNTIME_DIR if the user we now
* authenticated for does not match the original user
* of the session. We do this in order not to result
* in privileged apps clobbering the runtime directory
* unnecessarily. */
r = pam_misc_setenv(handle, "XDG_RUNTIME_DIR", runtime_path, 0);
if (r != PAM_SUCCESS) {
pam_syslog(handle, LOG_ERR, "Failed to set runtime dir.");
return r;
}
r = export_legacy_dbus_address(handle, pw->pw_uid, runtime_path);
if (r != PAM_SUCCESS)
return r;
}
if (!isempty(seat)) {
r = pam_misc_setenv(handle, "XDG_SEAT", seat, 0);
if (r != PAM_SUCCESS) {
pam_syslog(handle, LOG_ERR, "Failed to set seat.");
return r;
}
}
if (vtnr > 0) {
char buf[DECIMAL_STR_MAX(vtnr)];
sprintf(buf, "%u", vtnr);
r = pam_misc_setenv(handle, "XDG_VTNR", buf, 0);
if (r != PAM_SUCCESS) {
pam_syslog(handle, LOG_ERR, "Failed to set virtual terminal number.");
return r;
}
}
r = pam_set_data(handle, "systemd.existing", INT_TO_PTR(!!existing), NULL);
if (r != PAM_SUCCESS) {
pam_syslog(handle, LOG_ERR, "Failed to install existing flag.");
return r;
}
if (session_fd >= 0) {
session_fd = fcntl(session_fd, F_DUPFD_CLOEXEC, 3);
if (session_fd < 0) {
pam_syslog(handle, LOG_ERR, "Failed to dup session fd: %m");
return PAM_SESSION_ERR;
}
r = pam_set_data(handle, "systemd.session-fd", FD_TO_PTR(session_fd), NULL);
if (r != PAM_SUCCESS) {
pam_syslog(handle, LOG_ERR, "Failed to install session fd.");
safe_close(session_fd);
return r;
}
}
return PAM_SUCCESS;
}
_public_ PAM_EXTERN int pam_sm_close_session(
pam_handle_t *handle,
int flags,
int argc, const char **argv) {
_cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
_cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
const void *existing = NULL;
const char *id;
int r;
assert(handle);
/* Only release session if it wasn't pre-existing when we
* tried to create it */
pam_get_data(handle, "systemd.existing", &existing);
id = pam_getenv(handle, "XDG_SESSION_ID");
if (id && !existing) {
/* Before we go and close the FIFO we need to tell
* logind that this is a clean session shutdown, so
* that it doesn't just go and slaughter us
* immediately after closing the fd */
r = sd_bus_open_system(&bus);
if (r < 0) {
pam_syslog(handle, LOG_ERR, "Failed to connect to system bus: %s", strerror(-r));
return PAM_SESSION_ERR;
}
r = sd_bus_call_method(bus,
"org.freedesktop.login1",
"/org/freedesktop/login1",
"org.freedesktop.login1.Manager",
"ReleaseSession",
&error,
NULL,
"s",
id);
if (r < 0) {
pam_syslog(handle, LOG_ERR, "Failed to release session: %s", bus_error_message(&error, r));
return PAM_SESSION_ERR;
}
}
/* Note that we are knowingly leaking the FIFO fd here. This
* way, logind can watch us die. If we closed it here it would
* not have any clue when that is completed. Given that one
* cannot really have multiple PAM sessions open from the same
* process this means we will leak one FD at max. */
return PAM_SUCCESS;
}
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