507 lines
17 KiB
C
507 lines
17 KiB
C
/*-*- Mode: C; c-basic-offset: 8 -*-*/
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/***
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This file is part of systemd.
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Copyright 2010 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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***/
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#include <errno.h>
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#include <fcntl.h>
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#include <sys/file.h>
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#include <pwd.h>
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#include <endian.h>
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#include <security/pam_modules.h>
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#include <security/_pam_macros.h>
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#include <security/pam_modutil.h>
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#include <security/pam_ext.h>
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#include <security/pam_misc.h>
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#include "util.h"
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#include "cgroup-util.h"
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#include "macro.h"
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#include "sd-daemon.h"
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static int parse_argv(pam_handle_t *handle,
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int argc, const char **argv,
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bool *create_session,
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bool *kill_session,
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bool *kill_user) {
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unsigned i;
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assert(argc >= 0);
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assert(argc == 0 || argv);
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for (i = 0; i < (unsigned) argc; i++) {
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int k;
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if (startswith(argv[i], "create-session=")) {
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if ((k = parse_boolean(argv[i] + 15)) < 0) {
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pam_syslog(handle, LOG_ERR, "Failed to parse create-session= argument.");
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return k;
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}
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if (create_session)
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*create_session = k;
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} else if (startswith(argv[i], "kill-session=")) {
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if ((k = parse_boolean(argv[i] + 13)) < 0) {
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pam_syslog(handle, LOG_ERR, "Failed to parse kill-session= argument.");
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return k;
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}
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if (kill_session)
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*kill_session = k;
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} else if (startswith(argv[i], "kill-user=")) {
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if ((k = parse_boolean(argv[i] + 10)) < 0) {
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pam_syslog(handle, LOG_ERR, "Failed to parse kill-user= argument.");
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return k;
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}
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if (kill_user)
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*kill_user = k;
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} else {
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pam_syslog(handle, LOG_ERR, "Unknown parameter '%s'.", argv[i]);
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return -EINVAL;
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}
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}
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if (kill_session && *kill_session && kill_user)
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*kill_user = true;
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return 0;
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}
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static int open_file_and_lock(const char *fn) {
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int fd;
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assert(fn);
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if ((fd = open(fn, O_RDWR|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW|O_CREAT, 0600)) < 0)
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return -errno;
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/* The BSD socket semantics are a lot nicer than those of
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* POSIX locks. Which is why we use flock() here. BSD locking
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* does not work across NFS which however is not needed here
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* as the filesystems in question should be local, and only
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* locally accessible, and most likely even tmpfs. */
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if (flock(fd, LOCK_EX) < 0)
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return -errno;
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return fd;
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}
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enum {
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SESSION_ID_AUDIT = 'a',
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SESSION_ID_COUNTER = 'c',
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SESSION_ID_RANDOM = 'r'
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};
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static uint64_t get_session_id(int *mode) {
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char *s;
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int fd;
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assert(mode);
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/* First attempt: let's use the session ID of the audit
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* system, if it is available. */
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if (read_one_line_file("/proc/self/sessionid", &s) >= 0) {
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uint32_t u;
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int r;
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r = safe_atou32(s, &u);
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free(s);
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if (r >= 0 && u != (uint32_t) -1) {
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*mode = SESSION_ID_AUDIT;
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return (uint64_t) u;
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}
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}
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/* Second attempt, use our own counter. */
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if ((fd = open_file_and_lock(RUNTIME_DIR "/user/.pam-systemd-session")) >= 0) {
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uint64_t counter;
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ssize_t r;
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/* We do a bit of endianess swapping here, just to be
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* sure. /var should be machine specific anyway, and
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* /var/run even mounted from tmpfs, so this
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* byteswapping should really not be necessary. But
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* then again, you never know, so let's avoid any
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* risk. */
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if (loop_read(fd, &counter, sizeof(counter), false) != sizeof(counter))
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counter = 1;
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else
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counter = le64toh(counter) + 1;
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if (lseek(fd, 0, SEEK_SET) == 0) {
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uint64_t swapped = htole64(counter);
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r = loop_write(fd, &swapped, sizeof(swapped), false);
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if (r != sizeof(swapped))
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r = -EIO;
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} else
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r = -errno;
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close_nointr_nofail(fd);
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if (r >= 0) {
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*mode = SESSION_ID_COUNTER;
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return counter;
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}
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}
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*mode = SESSION_ID_RANDOM;
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/* Last attempt, pick a random value */
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return (uint64_t) random_ull();
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}
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static int get_user_data(
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pam_handle_t *handle,
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const char **ret_username,
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struct passwd **ret_pw) {
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const char *username;
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struct passwd *pw;
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int r;
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assert(handle);
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assert(ret_username);
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assert(ret_pw);
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if ((r = pam_get_user(handle, &username, NULL)) != PAM_SUCCESS) {
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pam_syslog(handle, LOG_ERR, "Failed to get user name.");
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return r;
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}
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if (!username || !*username) {
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pam_syslog(handle, LOG_ERR, "User name not valid.");
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return PAM_AUTH_ERR;
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}
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if (!(pw = pam_modutil_getpwnam(handle, username))) {
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pam_syslog(handle, LOG_ERR, "Failed to get user data.");
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return PAM_USER_UNKNOWN;
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}
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*ret_pw = pw;
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*ret_username = username;
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return PAM_SUCCESS;
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}
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static int create_user_group(pam_handle_t *handle, const char *group, struct passwd *pw, bool attach, bool remember) {
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int r;
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assert(handle);
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assert(group);
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if (attach)
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r = cg_create_and_attach(SYSTEMD_CGROUP_CONTROLLER, group, 0);
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else
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r = cg_create(SYSTEMD_CGROUP_CONTROLLER, group);
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if (r < 0) {
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pam_syslog(handle, LOG_ERR, "Failed to create cgroup: %s", strerror(-r));
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return PAM_SESSION_ERR;
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}
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if (r > 0 && remember) {
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/* Remember that it was us who created this group, and
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* that hence we need to remove it too. This is a
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* protection against removing the cgroup when run
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* recursively. */
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if ((r = pam_set_data(handle, "systemd.created", INT_TO_PTR(1), NULL)) != PAM_SUCCESS) {
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pam_syslog(handle, LOG_ERR, "Failed to install created variable.");
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return r;
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}
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}
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if ((r = cg_set_task_access(SYSTEMD_CGROUP_CONTROLLER, group, 0755, pw->pw_uid, pw->pw_gid)) < 0 ||
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(r = cg_set_group_access(SYSTEMD_CGROUP_CONTROLLER, group, 0755, pw->pw_uid, pw->pw_gid)) < 0) {
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pam_syslog(handle, LOG_ERR, "Failed to change access modes: %s", strerror(-r));
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return PAM_SESSION_ERR;
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}
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return PAM_SUCCESS;
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}
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_public_ PAM_EXTERN int pam_sm_open_session(
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pam_handle_t *handle,
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int flags,
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int argc, const char **argv) {
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const char *username = NULL;
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struct passwd *pw;
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int r;
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char *buf = NULL;
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int lock_fd = -1;
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bool create_session = true;
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assert(handle);
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/* pam_syslog(handle, LOG_DEBUG, "pam-systemd initializing"); */
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if (parse_argv(handle, argc, argv, &create_session, NULL, NULL) < 0)
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return PAM_SESSION_ERR;
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/* Make this a NOP on non-systemd systems */
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if (sd_booted() <= 0)
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return PAM_SUCCESS;
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if ((r = get_user_data(handle, &username, &pw)) != PAM_SUCCESS)
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goto finish;
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if (safe_mkdir(RUNTIME_DIR "/user", 0755, 0, 0) < 0) {
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pam_syslog(handle, LOG_ERR, "Failed to create runtime directory: %m");
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r = PAM_SYSTEM_ERR;
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goto finish;
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}
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if ((lock_fd = open_file_and_lock(RUNTIME_DIR "/user/.pam-systemd-lock")) < 0) {
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pam_syslog(handle, LOG_ERR, "Failed to lock runtime directory: %m");
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r = PAM_SYSTEM_ERR;
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goto finish;
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}
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/* Create /var/run/$USER */
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free(buf);
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if (asprintf(&buf, RUNTIME_DIR "/user/%s", username) < 0) {
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r = PAM_BUF_ERR;
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goto finish;
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}
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if (safe_mkdir(buf, 0700, pw->pw_uid, pw->pw_gid) < 0) {
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pam_syslog(handle, LOG_WARNING, "Failed to create runtime directory: %m");
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r = PAM_SYSTEM_ERR;
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goto finish;
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} else if ((r = pam_misc_setenv(handle, "XDG_RUNTIME_DIR", buf, 0)) != PAM_SUCCESS) {
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pam_syslog(handle, LOG_ERR, "Failed to set runtime dir.");
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goto finish;
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}
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free(buf);
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buf = NULL;
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if (create_session) {
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const char *id;
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/* Reuse or create XDG session ID */
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if (!(id = pam_getenv(handle, "XDG_SESSION_ID"))) {
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int mode;
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if (asprintf(&buf, "%llux", (unsigned long long) get_session_id(&mode)) < 0) {
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r = PAM_BUF_ERR;
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goto finish;
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}
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/* To avoid id clashes we add the session id
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* source to our session ids. Note that the
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* session id source might change during
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* runtime, because a filesystem became
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* writable or the system reconfigured. */
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buf[strlen(buf)-1] =
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mode != SESSION_ID_AUDIT ? (char) mode : 0;
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if ((r = pam_misc_setenv(handle, "XDG_SESSION_ID", buf, 0)) != PAM_SUCCESS) {
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pam_syslog(handle, LOG_ERR, "Failed to set session id.");
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goto finish;
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}
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if (!(id = pam_getenv(handle, "XDG_SESSION_ID"))) {
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pam_syslog(handle, LOG_ERR, "Failed to get session id.");
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r = PAM_SESSION_ERR;
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goto finish;
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}
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}
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r = asprintf(&buf, "/user/%s/%s", username, id);
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} else
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r = asprintf(&buf, "/user/%s/no-session", username);
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if (r < 0) {
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r = PAM_BUF_ERR;
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goto finish;
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}
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pam_syslog(handle, LOG_INFO, "Moving new user session for %s into control group %s.", username, buf);
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if ((r = create_user_group(handle, buf, pw, true, true)) != PAM_SUCCESS)
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goto finish;
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r = PAM_SUCCESS;
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finish:
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free(buf);
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if (lock_fd >= 0)
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close_nointr_nofail(lock_fd);
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return r;
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}
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static int session_remains(pam_handle_t *handle, const char *user_path) {
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int r;
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bool remains = false;
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DIR *d;
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char *subgroup;
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if ((r = cg_enumerate_subgroups(SYSTEMD_CGROUP_CONTROLLER, user_path, &d)) < 0)
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return r;
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while ((r = cg_read_subgroup(d, &subgroup)) > 0) {
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remains = !streq(subgroup, "no-session");
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free(subgroup);
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if (remains)
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break;
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}
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closedir(d);
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if (r < 0)
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return r;
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return !!remains;
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}
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_public_ PAM_EXTERN int pam_sm_close_session(
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pam_handle_t *handle,
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int flags,
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int argc, const char **argv) {
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const char *username = NULL;
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bool kill_session = false;
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bool kill_user = false;
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int lock_fd = -1, r;
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char *session_path = NULL, *nosession_path = NULL, *user_path = NULL;
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const char *id;
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struct passwd *pw;
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const void *created = NULL;
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assert(handle);
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if (parse_argv(handle, argc, argv, NULL, &kill_session, &kill_user) < 0)
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return PAM_SESSION_ERR;
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/* Make this a NOP on non-systemd systems */
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if (sd_booted() <= 0)
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return PAM_SUCCESS;
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if ((r = get_user_data(handle, &username, &pw)) != PAM_SUCCESS)
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goto finish;
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if ((lock_fd = open_file_and_lock(RUNTIME_DIR "/user/.pam-systemd-lock")) < 0) {
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pam_syslog(handle, LOG_ERR, "Failed to lock runtime directory: %m");
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r = PAM_SYSTEM_ERR;
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goto finish;
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}
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/* We are probably still in some session/no-session dir. Move ourselves out of the way as first step */
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if ((r = cg_attach(SYSTEMD_CGROUP_CONTROLLER, "/user", 0)) < 0)
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pam_syslog(handle, LOG_ERR, "Failed to move us away: %s", strerror(-r));
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if (asprintf(&user_path, "/user/%s", username) < 0) {
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r = PAM_BUF_ERR;
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goto finish;
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}
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pam_get_data(handle, "systemd.created", &created);
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if ((id = pam_getenv(handle, "XDG_SESSION_ID")) && created) {
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if (asprintf(&session_path, "/user/%s/%s", username, id) < 0 ||
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asprintf(&nosession_path, "/user/%s/no-session", username) < 0) {
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r = PAM_BUF_ERR;
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goto finish;
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}
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if (kill_session) {
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pam_syslog(handle, LOG_INFO, "Killing remaining processes of user session %s of %s.", id, username);
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/* Kill processes in session cgroup, and delete it */
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if ((r = cg_kill_recursive_and_wait(SYSTEMD_CGROUP_CONTROLLER, session_path, true)) < 0)
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pam_syslog(handle, LOG_ERR, "Failed to kill session cgroup: %s", strerror(-r));
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} else {
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pam_syslog(handle, LOG_INFO, "Moving remaining processes of user session %s of %s into control group %s.", id, username, nosession_path);
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/* Migrate processes from session to
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* no-session cgroup. First, try to create the
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* no-session group in case it doesn't exist
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* yet. Also, delete the session group. */
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create_user_group(handle, nosession_path, pw, false, false);
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if ((r = cg_migrate_recursive(SYSTEMD_CGROUP_CONTROLLER, session_path, nosession_path, false, true)) < 0)
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pam_syslog(handle, LOG_ERR, "Failed to migrate session cgroup: %s", strerror(-r));
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}
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}
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/* GC user tree */
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cg_trim(SYSTEMD_CGROUP_CONTROLLER, user_path, false);
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if ((r = session_remains(handle, user_path)) < 0)
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pam_syslog(handle, LOG_ERR, "Failed to determine whether a session remains: %s", strerror(-r));
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/* Kill user processes not attached to any session */
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if (kill_user && r == 0) {
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/* Kill no-session cgroup */
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if ((r = cg_kill_recursive_and_wait(SYSTEMD_CGROUP_CONTROLLER, user_path, true)) < 0)
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pam_syslog(handle, LOG_ERR, "Failed to kill user cgroup: %s", strerror(-r));
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} else {
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if ((r = cg_is_empty_recursive(SYSTEMD_CGROUP_CONTROLLER, user_path, true)) < 0)
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pam_syslog(handle, LOG_ERR, "Failed to check user cgroup: %s", strerror(-r));
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/* Remove user cgroup */
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if (r > 0) {
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if ((r = cg_delete(SYSTEMD_CGROUP_CONTROLLER, user_path)) < 0)
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pam_syslog(handle, LOG_ERR, "Failed to delete user cgroup: %s", strerror(-r));
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/* If we managed to find somebody, don't cleanup the cgroup. */
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} else if (r == 0)
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r = -EBUSY;
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}
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if (r >= 0) {
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const char *runtime_dir;
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if ((runtime_dir = pam_getenv(handle, "XDG_RUNTIME_DIR")))
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if ((r = rm_rf(runtime_dir, false, true)) < 0)
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pam_syslog(handle, LOG_ERR, "Failed to remove runtime directory: %s", strerror(-r));
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}
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/* pam_syslog(handle, LOG_DEBUG, "pam-systemd done"); */
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r = PAM_SUCCESS;
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finish:
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if (lock_fd >= 0)
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close_nointr_nofail(lock_fd);
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free(session_path);
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free(nosession_path);
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free(user_path);
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return r;
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}
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