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systemd/src/pam-module.c

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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 General Public License as published by
the Free Software Foundation; either version 2 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
General Public License for more details.
You should have received a copy of the GNU General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <errno.h>
#include <fcntl.h>
#include <sys/file.h>
#include <pwd.h>
#include <endian.h>
#include <security/pam_modules.h>
#include <security/_pam_macros.h>
#include <security/pam_modutil.h>
#include <security/pam_ext.h>
#include <security/pam_misc.h>
#include "util.h"
#include "cgroup-util.h"
#include "macro.h"
#include "sd-daemon.h"
static int parse_argv(pam_handle_t *handle,
int argc, const char **argv,
bool *create_session,
bool *kill_session,
bool *kill_user) {
unsigned i;
assert(argc >= 0);
assert(argc == 0 || argv);
for (i = 0; i < (unsigned) argc; i++) {
int k;
if (startswith(argv[i], "create-session=")) {
if ((k = parse_boolean(argv[i] + 15)) < 0) {
pam_syslog(handle, LOG_ERR, "Failed to parse create-session= argument.");
return k;
}
if (create_session)
*create_session = k;
} else if (startswith(argv[i], "kill-session=")) {
if ((k = parse_boolean(argv[i] + 13)) < 0) {
pam_syslog(handle, LOG_ERR, "Failed to parse kill-session= argument.");
return k;
}
if (kill_session)
*kill_session = k;
} else if (startswith(argv[i], "kill-user=")) {
if ((k = parse_boolean(argv[i] + 10)) < 0) {
pam_syslog(handle, LOG_ERR, "Failed to parse kill-user= argument.");
return k;
}
if (kill_user)
*kill_user = k;
} else {
pam_syslog(handle, LOG_ERR, "Unknown parameter '%s'.", argv[i]);
return -EINVAL;
}
}
if (kill_session && *kill_session && kill_user)
*kill_user = true;
return 0;
}
static int open_file_and_lock(const char *fn) {
int fd;
assert(fn);
if ((fd = open(fn, O_RDWR|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW|O_CREAT, 0600)) < 0)
return -errno;
/* The BSD socket semantics are a lot nicer than those of
* POSIX locks. Which is why we use flock() here. BSD locking
* does not work across NFS which however is not needed here
* as the filesystems in question should be local, and only
* locally accessible, and most likely even tmpfs. */
if (flock(fd, LOCK_EX) < 0)
return -errno;
return fd;
}
enum {
SESSION_ID_AUDIT = 'a',
SESSION_ID_COUNTER = 'c',
SESSION_ID_RANDOM = 'r'
};
static uint64_t get_session_id(int *mode) {
char *s;
int fd;
assert(mode);
/* First attempt: let's use the session ID of the audit
* system, if it is available. */
if (read_one_line_file("/proc/self/sessionid", &s) >= 0) {
uint32_t u;
int r;
r = safe_atou32(s, &u);
free(s);
if (r >= 0 && u != (uint32_t) -1) {
*mode = SESSION_ID_AUDIT;
return (uint64_t) u;
}
}
/* Second attempt, use our own counter. */
if ((fd = open_file_and_lock(RUNTIME_DIR "/user/.pam-systemd-session")) >= 0) {
uint64_t counter;
ssize_t r;
/* We do a bit of endianess swapping here, just to be
* sure. /var should be machine specific anyway, and
* /var/run even mounted from tmpfs, so this
* byteswapping should really not be necessary. But
* then again, you never know, so let's avoid any
* risk. */
if (loop_read(fd, &counter, sizeof(counter), false) != sizeof(counter))
counter = 1;
else
counter = le64toh(counter) + 1;
if (lseek(fd, 0, SEEK_SET) == 0) {
uint64_t swapped = htole64(counter);
r = loop_write(fd, &swapped, sizeof(swapped), false);
if (r != sizeof(swapped))
r = -EIO;
} else
r = -errno;
close_nointr_nofail(fd);
if (r >= 0) {
*mode = SESSION_ID_COUNTER;
return counter;
}
}
*mode = SESSION_ID_RANDOM;
/* Last attempt, pick a random value */
return (uint64_t) random_ull();
}
static int get_user_data(
pam_handle_t *handle,
const char **ret_username,
struct passwd **ret_pw) {
const char *username;
struct passwd *pw;
int r;
assert(handle);
assert(ret_username);
assert(ret_pw);
if ((r = pam_get_user(handle, &username, NULL)) != PAM_SUCCESS) {
pam_syslog(handle, LOG_ERR, "Failed to get user name.");
return r;
}
if (!username || !*username) {
pam_syslog(handle, LOG_ERR, "User name not valid.");
return PAM_AUTH_ERR;
}
if (!(pw = pam_modutil_getpwnam(handle, username))) {
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 create_user_group(pam_handle_t *handle, const char *group, struct passwd *pw, bool attach, bool remember) {
int r;
assert(handle);
assert(group);
if (attach)
r = cg_create_and_attach(SYSTEMD_CGROUP_CONTROLLER, group, 0);
else
r = cg_create(SYSTEMD_CGROUP_CONTROLLER, group);
if (r < 0) {
pam_syslog(handle, LOG_ERR, "Failed to create cgroup: %s", strerror(-r));
return PAM_SESSION_ERR;
}
if (r > 0 && remember) {
/* Remember that it was us who created this group, and
* that hence we need to remove it too. This is a
* protection against removing the cgroup when run
* recursively. */
if ((r = pam_set_data(handle, "systemd.created", INT_TO_PTR(1), NULL)) != PAM_SUCCESS) {
pam_syslog(handle, LOG_ERR, "Failed to install created variable.");
return r;
}
}
if ((r = cg_set_task_access(SYSTEMD_CGROUP_CONTROLLER, group, 0755, pw->pw_uid, pw->pw_gid)) < 0 ||
(r = cg_set_group_access(SYSTEMD_CGROUP_CONTROLLER, group, 0755, pw->pw_uid, pw->pw_gid)) < 0) {
pam_syslog(handle, LOG_ERR, "Failed to change access modes: %s", strerror(-r));
return PAM_SESSION_ERR;
}
return PAM_SUCCESS;
}
_public_ PAM_EXTERN int pam_sm_open_session(
pam_handle_t *handle,
int flags,
int argc, const char **argv) {
const char *username = NULL;
struct passwd *pw;
int r;
char *buf = NULL;
int lock_fd = -1;
bool create_session = true;
assert(handle);
/* pam_syslog(handle, LOG_DEBUG, "pam-systemd initializing"); */
if (parse_argv(handle, argc, argv, &create_session, NULL, NULL) < 0)
return PAM_SESSION_ERR;
/* Make this a NOP on non-systemd systems */
if (sd_booted() <= 0)
return PAM_SUCCESS;
if ((r = get_user_data(handle, &username, &pw)) != PAM_SUCCESS)
goto finish;
if (safe_mkdir(RUNTIME_DIR "/user", 0755, 0, 0) < 0) {
pam_syslog(handle, LOG_ERR, "Failed to create runtime directory: %m");
r = PAM_SYSTEM_ERR;
goto finish;
}
if ((lock_fd = open_file_and_lock(RUNTIME_DIR "/user/.pam-systemd-lock")) < 0) {
pam_syslog(handle, LOG_ERR, "Failed to lock runtime directory: %m");
r = PAM_SYSTEM_ERR;
goto finish;
}
/* Create /var/run/$USER */
free(buf);
if (asprintf(&buf, RUNTIME_DIR "/user/%s", username) < 0) {
r = PAM_BUF_ERR;
goto finish;
}
if (safe_mkdir(buf, 0700, pw->pw_uid, pw->pw_gid) < 0) {
pam_syslog(handle, LOG_WARNING, "Failed to create runtime directory: %m");
r = PAM_SYSTEM_ERR;
goto finish;
} else if ((r = pam_misc_setenv(handle, "XDG_RUNTIME_DIR", buf, 0)) != PAM_SUCCESS) {
pam_syslog(handle, LOG_ERR, "Failed to set runtime dir.");
goto finish;
}
free(buf);
buf = NULL;
if (create_session) {
const char *id;
/* Reuse or create XDG session ID */
if (!(id = pam_getenv(handle, "XDG_SESSION_ID"))) {
int mode;
if (asprintf(&buf, "%llux", (unsigned long long) get_session_id(&mode)) < 0) {
r = PAM_BUF_ERR;
goto finish;
}
/* To avoid id clashes we add the session id
* source to our session ids. Note that the
* session id source might change during
* runtime, because a filesystem became
* writable or the system reconfigured. */
buf[strlen(buf)-1] =
mode != SESSION_ID_AUDIT ? (char) mode : 0;
if ((r = pam_misc_setenv(handle, "XDG_SESSION_ID", buf, 0)) != PAM_SUCCESS) {
pam_syslog(handle, LOG_ERR, "Failed to set session id.");
goto finish;
}
if (!(id = pam_getenv(handle, "XDG_SESSION_ID"))) {
pam_syslog(handle, LOG_ERR, "Failed to get session id.");
r = PAM_SESSION_ERR;
goto finish;
}
}
r = asprintf(&buf, "/user/%s/%s", username, id);
} else
r = asprintf(&buf, "/user/%s/no-session", username);
if (r < 0) {
r = PAM_BUF_ERR;
goto finish;
}
pam_syslog(handle, LOG_INFO, "Moving new user session for %s into control group %s.", username, buf);
if ((r = create_user_group(handle, buf, pw, true, true)) != PAM_SUCCESS)
goto finish;
r = PAM_SUCCESS;
finish:
free(buf);
if (lock_fd >= 0)
close_nointr_nofail(lock_fd);
return r;
}
static int session_remains(pam_handle_t *handle, const char *user_path) {
int r;
bool remains = false;
DIR *d;
char *subgroup;
if ((r = cg_enumerate_subgroups(SYSTEMD_CGROUP_CONTROLLER, user_path, &d)) < 0)
return r;
while ((r = cg_read_subgroup(d, &subgroup)) > 0) {
remains = !streq(subgroup, "no-session");
free(subgroup);
if (remains)
break;
}
closedir(d);
if (r < 0)
return r;
return !!remains;
}
_public_ PAM_EXTERN int pam_sm_close_session(
pam_handle_t *handle,
int flags,
int argc, const char **argv) {
const char *username = NULL;
bool kill_session = false;
bool kill_user = false;
int lock_fd = -1, r;
char *session_path = NULL, *nosession_path = NULL, *user_path = NULL;
const char *id;
struct passwd *pw;
const void *created = NULL;
assert(handle);
if (parse_argv(handle, argc, argv, NULL, &kill_session, &kill_user) < 0)
return PAM_SESSION_ERR;
/* Make this a NOP on non-systemd systems */
if (sd_booted() <= 0)
return PAM_SUCCESS;
if ((r = get_user_data(handle, &username, &pw)) != PAM_SUCCESS)
goto finish;
if ((lock_fd = open_file_and_lock(RUNTIME_DIR "/user/.pam-systemd-lock")) < 0) {
pam_syslog(handle, LOG_ERR, "Failed to lock runtime directory: %m");
r = PAM_SYSTEM_ERR;
goto finish;
}
/* We are probably still in some session/no-session dir. Move ourselves out of the way as first step */
if ((r = cg_attach(SYSTEMD_CGROUP_CONTROLLER, "/user", 0)) < 0)
pam_syslog(handle, LOG_ERR, "Failed to move us away: %s", strerror(-r));
if (asprintf(&user_path, "/user/%s", username) < 0) {
r = PAM_BUF_ERR;
goto finish;
}
pam_get_data(handle, "systemd.created", &created);
if ((id = pam_getenv(handle, "XDG_SESSION_ID")) && created) {
if (asprintf(&session_path, "/user/%s/%s", username, id) < 0 ||
asprintf(&nosession_path, "/user/%s/no-session", username) < 0) {
r = PAM_BUF_ERR;
goto finish;
}
if (kill_session) {
pam_syslog(handle, LOG_INFO, "Killing remaining processes of user session %s of %s.", id, username);
/* Kill processes in session cgroup, and delete it */
if ((r = cg_kill_recursive_and_wait(SYSTEMD_CGROUP_CONTROLLER, session_path, true)) < 0)
pam_syslog(handle, LOG_ERR, "Failed to kill session cgroup: %s", strerror(-r));
} else {
pam_syslog(handle, LOG_INFO, "Moving remaining processes of user session %s of %s into control group %s.", id, username, nosession_path);
/* Migrate processes from session to
* no-session cgroup. First, try to create the
* no-session group in case it doesn't exist
* yet. Also, delete the session group. */
create_user_group(handle, nosession_path, pw, false, false);
if ((r = cg_migrate_recursive(SYSTEMD_CGROUP_CONTROLLER, session_path, nosession_path, false, true)) < 0)
pam_syslog(handle, LOG_ERR, "Failed to migrate session cgroup: %s", strerror(-r));
}
}
/* GC user tree */
cg_trim(SYSTEMD_CGROUP_CONTROLLER, user_path, false);
if ((r = session_remains(handle, user_path)) < 0)
pam_syslog(handle, LOG_ERR, "Failed to determine whether a session remains: %s", strerror(-r));
/* Kill user processes not attached to any session */
if (kill_user && r == 0) {
/* Kill no-session cgroup */
if ((r = cg_kill_recursive_and_wait(SYSTEMD_CGROUP_CONTROLLER, user_path, true)) < 0)
pam_syslog(handle, LOG_ERR, "Failed to kill user cgroup: %s", strerror(-r));
} else {
if ((r = cg_is_empty_recursive(SYSTEMD_CGROUP_CONTROLLER, user_path, true)) < 0)
pam_syslog(handle, LOG_ERR, "Failed to check user cgroup: %s", strerror(-r));
/* Remove user cgroup */
if (r > 0) {
if ((r = cg_delete(SYSTEMD_CGROUP_CONTROLLER, user_path)) < 0)
pam_syslog(handle, LOG_ERR, "Failed to delete user cgroup: %s", strerror(-r));
/* If we managed to find somebody, don't cleanup the cgroup. */
} else if (r == 0)
r = -EBUSY;
}
if (r >= 0) {
const char *runtime_dir;
if ((runtime_dir = pam_getenv(handle, "XDG_RUNTIME_DIR")))
if ((r = rm_rf(runtime_dir, false, true)) < 0)
pam_syslog(handle, LOG_ERR, "Failed to remove runtime directory: %s", strerror(-r));
}
/* pam_syslog(handle, LOG_DEBUG, "pam-systemd done"); */
r = PAM_SUCCESS;
finish:
if (lock_fd >= 0)
close_nointr_nofail(lock_fd);
free(session_path);
free(nosession_path);
free(user_path);
return r;
}
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