Adding upstream version 255.4.upstream/255.4

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1266 insertions, 0 deletions

diff --git a/src/login/pam_systemd.c b/src/login/pam_systemd.c
new file mode 100644
index 0000000..bf45974
--- /dev/null
+++ b/src/login/pam_systemd.c
@@ -0,0 +1,1266 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#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 <sys/stat.h>
+#include <sys/sysmacros.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "alloc-util.h"
+#include "audit-util.h"
+#include "bus-common-errors.h"
+#include "bus-error.h"
+#include "bus-internal.h"
+#include "bus-locator.h"
+#include "cap-list.h"
+#include "capability-util.h"
+#include "cgroup-setup.h"
+#include "devnum-util.h"
+#include "errno-util.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "format-util.h"
+#include "fs-util.h"
+#include "hostname-util.h"
+#include "locale-util.h"
+#include "login-util.h"
+#include "macro.h"
+#include "missing_syscall.h"
+#include "pam-util.h"
+#include "parse-util.h"
+#include "path-util.h"
+#include "percent-util.h"
+#include "process-util.h"
+#include "rlimit-util.h"
+#include "socket-util.h"
+#include "stdio-util.h"
+#include "strv.h"
+#include "terminal-util.h"
+#include "user-util.h"
+#include "userdb.h"
+
+#define LOGIN_SLOW_BUS_CALL_TIMEOUT_USEC (2*USEC_PER_MINUTE)
+
+static int parse_caps(
+                pam_handle_t *handle,
+                const char *value,
+                uint64_t *caps) {
+
+        bool subtract;
+        int r;
+
+        assert(handle);
+        assert(value);
+
+        if (value[0] == '~') {
+                subtract = true;
+                value++;
+        } else
+                subtract = false;
+
+        for (;;) {
+                _cleanup_free_ char *s = NULL;
+                uint64_t b, m;
+                int c;
+
+                /* We can't use spaces as separators here, as PAM's simplistic argument parser doesn't allow
+                 * spaces inside of arguments. We use commas instead (which is similar to cap_from_text(),
+                 * which also uses commas). */
+                r = extract_first_word(&value, &s, ",", EXTRACT_DONT_COALESCE_SEPARATORS);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        break;
+
+                c = capability_from_name(s);
+                if (c < 0) {
+                        pam_syslog(handle, LOG_WARNING, "Unknown capability, ignoring: %s", s);
+                        continue;
+                }
+
+                m = UINT64_C(1) << c;
+
+                if (!caps)
+                        continue;
+
+                if (*caps == UINT64_MAX)
+                        b = subtract ? all_capabilities() : 0;
+                else
+                        b = *caps;
+
+                if (subtract)
+                        *caps = b & ~m;
+                else
+                        *caps = b | m;
+        }
+
+        return 0;
+}
+
+static int parse_argv(
+                pam_handle_t *handle,
+                int argc, const char **argv,
+                const char **class,
+                const char **type,
+                const char **desktop,
+                bool *debug,
+                uint64_t *default_capability_bounding_set,
+                uint64_t *default_capability_ambient_set) {
+
+        int r;
+
+        assert(handle);
+        assert(argc >= 0);
+        assert(argc == 0 || argv);
+
+        for (int i = 0; i < argc; i++) {
+                const char *p;
+
+                if ((p = startswith(argv[i], "class="))) {
+                        if (class)
+                                *class = p;
+
+                } else if ((p = startswith(argv[i], "type="))) {
+                        if (type)
+                                *type = p;
+
+                } else if ((p = startswith(argv[i], "desktop="))) {
+                        if (desktop)
+                                *desktop = p;
+
+                } else if (streq(argv[i], "debug")) {
+                        if (debug)
+                                *debug = true;
+
+                } else if ((p = startswith(argv[i], "debug="))) {
+                        r = parse_boolean(p);
+                        if (r < 0)
+                                pam_syslog(handle, LOG_WARNING, "Failed to parse debug= argument, ignoring: %s", p);
+                        else if (debug)
+                                *debug = r;
+
+                } else if ((p = startswith(argv[i], "default-capability-bounding-set="))) {
+                        r = parse_caps(handle, p, default_capability_bounding_set);
+                        if (r < 0)
+                                pam_syslog(handle, LOG_WARNING, "Failed to parse default-capability-bounding-set= argument, ignoring: %s", p);
+
+                } else if ((p = startswith(argv[i], "default-capability-ambient-set="))) {
+                        r = parse_caps(handle, p, default_capability_ambient_set);
+                        if (r < 0)
+                                pam_syslog(handle, LOG_WARNING, "Failed to parse default-capability-ambient-set= argument, ignoring: %s", p);
+
+                } else
+                        pam_syslog(handle, LOG_WARNING, "Unknown parameter '%s', ignoring.", argv[i]);
+        }
+
+        return 0;
+}
+
+static int acquire_user_record(
+                pam_handle_t *handle,
+                UserRecord **ret_record) {
+
+        _cleanup_(user_record_unrefp) UserRecord *ur = NULL;
+        const char *username = NULL, *json = NULL;
+        _cleanup_free_ char *field = NULL;
+        int r;
+
+        assert(handle);
+
+        r = pam_get_user(handle, &username, NULL);
+        if (r != PAM_SUCCESS)
+                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to get user name: @PAMERR@");
+
+        if (isempty(username))
+                return pam_syslog_pam_error(handle, LOG_ERR, PAM_SERVICE_ERR, "User name not valid.");
+
+        /* If pam_systemd_homed (or some other module) already acquired the user record we can reuse it
+         * here. */
+        field = strjoin("systemd-user-record-", username);
+        if (!field)
+                return pam_log_oom(handle);
+
+        r = pam_get_data(handle, field, (const void**) &json);
+        if (!IN_SET(r, PAM_SUCCESS, PAM_NO_MODULE_DATA))
+                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to get PAM user record data: @PAMERR@");
+        if (r == PAM_SUCCESS && json) {
+                _cleanup_(json_variant_unrefp) JsonVariant *v = NULL;
+
+                /* Parse cached record */
+                r = json_parse(json, JSON_PARSE_SENSITIVE, &v, NULL, NULL);
+                if (r < 0)
+                        return pam_syslog_errno(handle, LOG_ERR, r, "Failed to parse JSON user record: %m");
+
+                ur = user_record_new();
+                if (!ur)
+                        return pam_log_oom(handle);
+
+                r = user_record_load(ur, v, USER_RECORD_LOAD_REFUSE_SECRET|USER_RECORD_PERMISSIVE);
+                if (r < 0)
+                        return pam_syslog_errno(handle, LOG_ERR, r, "Failed to load user record: %m");
+
+                /* Safety check if cached record actually matches what we are looking for */
+                if (!streq_ptr(username, ur->user_name))
+                        return pam_syslog_pam_error(handle, LOG_ERR, PAM_SERVICE_ERR,
+                                                    "Acquired user record does not match user name.");
+        } else {
+                _cleanup_free_ char *formatted = NULL;
+
+                /* Request the record ourselves */
+                r = userdb_by_name(username, 0, &ur);
+                if (r < 0) {
+                        pam_syslog_errno(handle, LOG_ERR, r, "Failed to get user record: %m");
+                        return PAM_USER_UNKNOWN;
+                }
+
+                r = json_variant_format(ur->json, 0, &formatted);
+                if (r < 0)
+                        return pam_syslog_errno(handle, LOG_ERR, r, "Failed to format user JSON: %m");
+
+                /* And cache it for everyone else */
+                r = pam_set_data(handle, field, formatted, pam_cleanup_free);
+                if (r != PAM_SUCCESS)
+                        return pam_syslog_pam_error(handle, LOG_ERR, r,
+                                                    "Failed to set PAM user record data '%s': @PAMERR@", field);
+                TAKE_PTR(formatted);
+        }
+
+        if (!uid_is_valid(ur->uid))
+                return pam_syslog_pam_error(handle, LOG_ERR, PAM_SERVICE_ERR,
+                                            "Acquired user record does not have a UID.");
+
+        if (ret_record)
+                *ret_record = TAKE_PTR(ur);
+
+        return PAM_SUCCESS;
+}
+
+static bool display_is_local(const char *display) {
+        assert(display);
+
+        return
+                display[0] == ':' &&
+                ascii_isdigit(display[1]);
+}
+
+static int socket_from_display(const char *display) {
+        _cleanup_free_ char *f = NULL;
+        size_t k;
+        char *c;
+        union sockaddr_union sa;
+        socklen_t sa_len;
+        _cleanup_close_ int fd = -EBADF;
+        int r;
+
+        assert(display);
+
+        if (!display_is_local(display))
+                return -EINVAL;
+
+        k = strspn(display+1, "0123456789");
+
+        /* Try abstract socket first. */
+        f = new(char, STRLEN("@/tmp/.X11-unix/X") + k + 1);
+        if (!f)
+                return -ENOMEM;
+
+        c = stpcpy(f, "@/tmp/.X11-unix/X");
+        memcpy(c, display+1, k);
+        c[k] = 0;
+
+        r = sockaddr_un_set_path(&sa.un, f);
+        if (r < 0)
+                return r;
+        sa_len = r;
+
+        fd = RET_NERRNO(socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0));
+        if (fd < 0)
+                return fd;
+
+        r = RET_NERRNO(connect(fd, &sa.sa, sa_len));
+        if (r >= 0)
+                return TAKE_FD(fd);
+        if (r != -ECONNREFUSED)
+                return r;
+
+        /* Try also non-abstract socket. */
+        r = sockaddr_un_set_path(&sa.un, f + 1);
+        if (r < 0)
+                return r;
+        sa_len = r;
+
+        r = RET_NERRNO(connect(fd, &sa.sa, sa_len));
+        if (r >= 0)
+                return TAKE_FD(fd);
+        return r;
+}
+
+static int get_seat_from_display(const char *display, const char **seat, uint32_t *vtnr) {
+        _cleanup_free_ char *sys_path = NULL, *tty = NULL;
+        _cleanup_close_ int fd = -EBADF;
+        struct ucred ucred;
+        int v, r;
+        dev_t display_ctty;
+
+        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. */
+
+        fd = socket_from_display(display);
+        if (fd < 0)
+                return fd;
+
+        r = getpeercred(fd, &ucred);
+        if (r < 0)
+                return r;
+
+        r = get_ctty_devnr(ucred.pid, &display_ctty);
+        if (r < 0)
+                return r;
+
+        if (asprintf(&sys_path, "/sys/dev/char/" DEVNUM_FORMAT_STR, DEVNUM_FORMAT_VAL(display_ctty)) < 0)
+                return -ENOMEM;
+        r = readlink_value(sys_path, &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,
+                const char *runtime) {
+
+        const char *s;
+        _cleanup_free_ char *t = NULL;
+        int r = PAM_BUF_ERR;
+
+        /* We need to export $DBUS_SESSION_BUS_ADDRESS because various applications will not connect
+         * correctly to the bus without it. This setting matches what dbus.socket does for the user
+         * session using 'systemctl --user set-environment'. We want to have the same configuration
+         * in processes started from the PAM session.
+         *
+         * The setting of the address is guarded by the access() check because it is also possible to compile
+         * dbus without --enable-user-session, in which case this socket is not used, and
+         * $DBUS_SESSION_BUS_ADDRESS should not be set. An alternative approach would to not do the access()
+         * check here, and let applications try on their own, by using "unix:path=%s/bus;autolaunch:". But we
+         * expect the socket to be present by the time we do this check, so we can just as well check once
+         * here. */
+
+        s = strjoina(runtime, "/bus");
+        if (access(s, F_OK) < 0)
+                return PAM_SUCCESS;
+
+        if (asprintf(&t, DEFAULT_USER_BUS_ADDRESS_FMT, runtime) < 0)
+                return pam_log_oom(handle);
+
+        r = pam_misc_setenv(handle, "DBUS_SESSION_BUS_ADDRESS", t, 0);
+        if (r != PAM_SUCCESS)
+                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to set bus variable: @PAMERR@");
+
+        return PAM_SUCCESS;
+}
+
+static int append_session_memory_max(pam_handle_t *handle, sd_bus_message *m, const char *limit) {
+        uint64_t val;
+        int r;
+
+        if (isempty(limit))
+                return PAM_SUCCESS;
+
+        if (streq(limit, "infinity")) {
+                r = sd_bus_message_append(m, "(sv)", "MemoryMax", "t", UINT64_MAX);
+                if (r < 0)
+                        return pam_bus_log_create_error(handle, r);
+
+                return PAM_SUCCESS;
+        }
+
+        r = parse_permyriad(limit);
+        if (r >= 0) {
+                r = sd_bus_message_append(m, "(sv)", "MemoryMaxScale", "u", UINT32_SCALE_FROM_PERMYRIAD(r));
+                if (r < 0)
+                        return pam_bus_log_create_error(handle, r);
+
+                return PAM_SUCCESS;
+        }
+
+        r = parse_size(limit, 1024, &val);
+        if (r >= 0) {
+                r = sd_bus_message_append(m, "(sv)", "MemoryMax", "t", val);
+                if (r < 0)
+                        return pam_bus_log_create_error(handle, r);
+
+                return PAM_SUCCESS;
+        }
+
+        pam_syslog(handle, LOG_WARNING, "Failed to parse systemd.memory_max, ignoring: %s", limit);
+        return PAM_SUCCESS;
+}
+
+static int append_session_runtime_max_sec(pam_handle_t *handle, sd_bus_message *m, const char *limit) {
+        usec_t val;
+        int r;
+
+        /* No need to parse "infinity" here, it will be set by default later in scope_init() */
+        if (isempty(limit) || streq(limit, "infinity"))
+                return PAM_SUCCESS;
+
+        r = parse_sec(limit, &val);
+        if (r >= 0) {
+                r = sd_bus_message_append(m, "(sv)", "RuntimeMaxUSec", "t", (uint64_t) val);
+                if (r < 0)
+                        return pam_bus_log_create_error(handle, r);
+        } else
+                pam_syslog(handle, LOG_WARNING, "Failed to parse systemd.runtime_max_sec: %s, ignoring.", limit);
+
+        return PAM_SUCCESS;
+}
+
+static int append_session_tasks_max(pam_handle_t *handle, sd_bus_message *m, const char *limit) {
+        uint64_t val;
+        int r;
+
+        /* No need to parse "infinity" here, it will be set unconditionally later in manager_start_scope() */
+        if (isempty(limit) || streq(limit, "infinity"))
+                return PAM_SUCCESS;
+
+        r = safe_atou64(limit, &val);
+        if (r >= 0) {
+                r = sd_bus_message_append(m, "(sv)", "TasksMax", "t", val);
+                if (r < 0)
+                        return pam_bus_log_create_error(handle, r);
+        } else
+                pam_syslog(handle, LOG_WARNING, "Failed to parse systemd.tasks_max, ignoring: %s", limit);
+
+        return PAM_SUCCESS;
+}
+
+static int append_session_cpu_weight(pam_handle_t *handle, sd_bus_message *m, const char *limit) {
+        uint64_t val;
+        int r;
+
+        if (isempty(limit))
+                return PAM_SUCCESS;
+
+        r = cg_cpu_weight_parse(limit, &val);
+        if (r < 0)
+                pam_syslog(handle, LOG_WARNING, "Failed to parse systemd.cpu_weight, ignoring: %s", limit);
+        else {
+                r = sd_bus_message_append(m, "(sv)", "CPUWeight", "t", val);
+                if (r < 0)
+                        return pam_bus_log_create_error(handle, r);
+        }
+
+        return PAM_SUCCESS;
+}
+
+static int append_session_io_weight(pam_handle_t *handle, sd_bus_message *m, const char *limit) {
+        uint64_t val;
+        int r;
+
+        if (isempty(limit))
+                return PAM_SUCCESS;
+
+        r = cg_weight_parse(limit, &val);
+        if (r < 0)
+                pam_syslog(handle, LOG_WARNING, "Failed to parse systemd.io_weight, ignoring: %s", limit);
+        else {
+                r = sd_bus_message_append(m, "(sv)", "IOWeight", "t", val);
+                if (r < 0)
+                        return pam_bus_log_create_error(handle, r);
+        }
+
+        return PAM_SUCCESS;
+}
+
+static const char* getenv_harder(pam_handle_t *handle, const char *key, const char *fallback) {
+        const char *v;
+
+        assert(handle);
+        assert(key);
+
+        /* Looks for an environment variable, preferably in the environment block associated with the
+         * specified PAM handle, falling back to the process' block instead. Why check both? Because we want
+         * to permit configuration of session properties from unit files that invoke PAM services, so that
+         * PAM services don't have to be reworked to set systemd-specific properties, but these properties
+         * can still be set from the unit file Environment= block. */
+
+        v = pam_getenv(handle, key);
+        if (!isempty(v))
+                return v;
+
+        /* We use secure_getenv() here, since we might get loaded into su/sudo, which are SUID. Ideally
+         * they'd clean up the environment before invoking foreign code (such as PAM modules), but alas they
+         * currently don't (to be precise, they clean up the environment they pass to their children, but
+         * not their own environ[]). */
+        v = secure_getenv(key);
+        if (!isempty(v))
+                return v;
+
+        return fallback;
+}
+
+static int update_environment(pam_handle_t *handle, const char *key, const char *value) {
+        int r;
+
+        assert(handle);
+        assert(key);
+
+        /* Updates the environment, but only if there's actually a value set. Also, log about errors */
+
+        if (isempty(value))
+                return PAM_SUCCESS;
+
+        r = pam_misc_setenv(handle, key, value, 0);
+        if (r != PAM_SUCCESS)
+                return pam_syslog_pam_error(handle, LOG_ERR, r,
+                                            "Failed to set environment variable %s: @PAMERR@", key);
+
+        return PAM_SUCCESS;
+}
+
+static bool validate_runtime_directory(pam_handle_t *handle, const char *path, uid_t uid) {
+        struct stat st;
+
+        assert(handle);
+        assert(path);
+
+        /* Some extra paranoia: let's not set $XDG_RUNTIME_DIR if the directory we'd set it to isn't actually
+         * set up properly for us. This is supposed to provide a careful safety net for supporting su/sudo
+         * type transitions: in that case the UID changes, but the session and thus the user owning it
+         * doesn't change. Since the $XDG_RUNTIME_DIR lifecycle is bound to the session's user being logged
+         * in at least once we should be particularly careful when setting the environment variable, since
+         * otherwise we might end up setting $XDG_RUNTIME_DIR to some directory owned by the wrong user. */
+
+        if (!path_is_absolute(path)) {
+                pam_syslog(handle, LOG_ERR, "Provided runtime directory '%s' is not absolute.", path);
+                goto fail;
+        }
+
+        if (lstat(path, &st) < 0) {
+                pam_syslog_errno(handle, LOG_ERR, errno, "Failed to stat() runtime directory '%s': %m", path);
+                goto fail;
+        }
+
+        if (!S_ISDIR(st.st_mode)) {
+                pam_syslog(handle, LOG_ERR, "Runtime directory '%s' is not actually a directory.", path);
+                goto fail;
+        }
+
+        if (st.st_uid != uid) {
+                pam_syslog(handle, LOG_ERR, "Runtime directory '%s' is not owned by UID " UID_FMT ", as it should.", path, uid);
+                goto fail;
+        }
+
+        return true;
+
+fail:
+        pam_syslog(handle, LOG_WARNING, "Not setting $XDG_RUNTIME_DIR, as the directory is not in order.");
+        return false;
+}
+
+static int pam_putenv_and_log(pam_handle_t *handle, const char *e, bool debug) {
+        int r;
+
+        assert(handle);
+        assert(e);
+
+        r = pam_putenv(handle, e);
+        if (r != PAM_SUCCESS)
+                return pam_syslog_pam_error(handle, LOG_ERR, r,
+                                            "Failed to set PAM environment variable %s: @PAMERR@", e);
+
+        pam_debug_syslog(handle, debug, "PAM environment variable %s set based on user record.", e);
+
+        return PAM_SUCCESS;
+}
+
+static int apply_user_record_settings(
+                pam_handle_t *handle,
+                UserRecord *ur,
+                bool debug,
+                uint64_t default_capability_bounding_set,
+                uint64_t default_capability_ambient_set) {
+        int r;
+
+        assert(handle);
+        assert(ur);
+
+        if (ur->umask != MODE_INVALID) {
+                umask(ur->umask);
+                pam_debug_syslog(handle, debug, "Set user umask to %04o based on user record.", ur->umask);
+        }
+
+        STRV_FOREACH(i, ur->environment) {
+                _cleanup_free_ char *n = NULL;
+                const char *e;
+
+                assert_se(e = strchr(*i, '=')); /* environment was already validated while parsing JSON record, this thus must hold */
+
+                n = strndup(*i, e - *i);
+                if (!n)
+                        return pam_log_oom(handle);
+
+                if (pam_getenv(handle, n)) {
+                        pam_debug_syslog(handle, debug,
+                                         "PAM environment variable $%s already set, not changing based on record.", *i);
+                        continue;
+                }
+
+                r = pam_putenv_and_log(handle, *i, debug);
+                if (r != PAM_SUCCESS)
+                        return r;
+        }
+
+        if (ur->email_address) {
+                if (pam_getenv(handle, "EMAIL"))
+                        pam_debug_syslog(handle, debug,
+                                         "PAM environment variable $EMAIL already set, not changing based on user record.");
+                else {
+                        _cleanup_free_ char *joined = NULL;
+
+                        joined = strjoin("EMAIL=", ur->email_address);
+                        if (!joined)
+                                return pam_log_oom(handle);
+
+                        r = pam_putenv_and_log(handle, joined, debug);
+                        if (r != PAM_SUCCESS)
+                                return r;
+                }
+        }
+
+        if (ur->time_zone) {
+                if (pam_getenv(handle, "TZ"))
+                        pam_debug_syslog(handle, debug,
+                                         "PAM environment variable $TZ already set, not changing based on user record.");
+                else if (!timezone_is_valid(ur->time_zone, LOG_DEBUG))
+                        pam_debug_syslog(handle, debug,
+                                         "Time zone specified in user record is not valid locally, not setting $TZ.");
+                else {
+                        _cleanup_free_ char *joined = NULL;
+
+                        joined = strjoin("TZ=:", ur->time_zone);
+                        if (!joined)
+                                return pam_log_oom(handle);
+
+                        r = pam_putenv_and_log(handle, joined, debug);
+                        if (r != PAM_SUCCESS)
+                                return r;
+                }
+        }
+
+        if (ur->preferred_language) {
+                if (pam_getenv(handle, "LANG"))
+                        pam_debug_syslog(handle, debug,
+                                         "PAM environment variable $LANG already set, not changing based on user record.");
+                else if (locale_is_installed(ur->preferred_language) <= 0)
+                        pam_debug_syslog(handle, debug,
+                                         "Preferred language specified in user record is not valid or not installed, not setting $LANG.");
+                else {
+                        _cleanup_free_ char *joined = NULL;
+
+                        joined = strjoin("LANG=", ur->preferred_language);
+                        if (!joined)
+                                return pam_log_oom(handle);
+
+                        r = pam_putenv_and_log(handle, joined, debug);
+                        if (r != PAM_SUCCESS)
+                                return r;
+                }
+        }
+
+        if (nice_is_valid(ur->nice_level)) {
+                if (nice(ur->nice_level) < 0)
+                        pam_syslog_errno(handle, LOG_ERR, errno,
+                                         "Failed to set nice level to %i, ignoring: %m", ur->nice_level);
+                else
+                        pam_debug_syslog(handle, debug,
+                                         "Nice level set to %i, based on user record.", ur->nice_level);
+        }
+
+        for (int rl = 0; rl < _RLIMIT_MAX; rl++) {
+
+                if (!ur->rlimits[rl])
+                        continue;
+
+                r = setrlimit_closest(rl, ur->rlimits[rl]);
+                if (r < 0)
+                        pam_syslog_errno(handle, LOG_ERR, r,
+                                         "Failed to set resource limit %s, ignoring: %m", rlimit_to_string(rl));
+                else
+                        pam_debug_syslog(handle, debug,
+                                         "Resource limit %s set, based on user record.", rlimit_to_string(rl));
+        }
+
+        uint64_t a, b;
+        a = user_record_capability_ambient_set(ur);
+        if (a == UINT64_MAX)
+                a = default_capability_ambient_set;
+
+        b = user_record_capability_bounding_set(ur);
+        if (b == UINT64_MAX)
+                b = default_capability_bounding_set;
+
+        if (a != UINT64_MAX && a != 0) {
+                a &= b;
+
+                r = capability_ambient_set_apply(a, /* also_inherit= */ true);
+                if (r < 0)
+                        pam_syslog_errno(handle, LOG_ERR, r,
+                                         "Failed to set ambient capabilities, ignoring: %m");
+        }
+
+        if (b != UINT64_MAX && !cap_test_all(b)) {
+                r = capability_bounding_set_drop(b, /* right_now= */ false);
+                if (r < 0)
+                        pam_syslog_errno(handle, LOG_ERR, r,
+                                         "Failed to set bounding capabilities, ignoring: %m");
+        }
+
+        return PAM_SUCCESS;
+}
+
+static int configure_runtime_directory(
+                pam_handle_t *handle,
+                UserRecord *ur,
+                const char *rt) {
+
+        int r;
+
+        assert(handle);
+        assert(ur);
+        assert(rt);
+
+        if (!validate_runtime_directory(handle, rt, ur->uid))
+                return PAM_SUCCESS;
+
+        r = pam_misc_setenv(handle, "XDG_RUNTIME_DIR", rt, 0);
+        if (r != PAM_SUCCESS)
+                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to set runtime dir: @PAMERR@");
+
+        return export_legacy_dbus_address(handle, rt);
+}
+
+static uint64_t pick_default_capability_ambient_set(
+                UserRecord *ur,
+                const char *service,
+                const char *seat) {
+
+        /* If not configured otherwise, let's enable CAP_WAKE_ALARM for regular users when logging in on a
+         * seat (i.e. when they are present physically on the device), or when invoked for the systemd --user
+         * instances. This allows desktops to install CAP_WAKE_ALARM to implement alarm clock apps without
+         * much fuss. */
+
+        return ur &&
+                user_record_disposition(ur) == USER_REGULAR &&
+                (streq_ptr(service, "systemd-user") || !isempty(seat)) ? (UINT64_C(1) << CAP_WAKE_ALARM) : UINT64_MAX;
+}
+
+typedef struct SessionContext {
+        const uid_t uid;
+        const pid_t pid;
+        const char *service;
+        const char *type;
+        const char *class;
+        const char *desktop;
+        const char *seat;
+        const uint32_t vtnr;
+        const char *tty;
+        const char *display;
+        const bool remote;
+        const char *remote_user;
+        const char *remote_host;
+        const char *memory_max;
+        const char *tasks_max;
+        const char *cpu_weight;
+        const char *io_weight;
+        const char *runtime_max_sec;
+} SessionContext;
+
+static int create_session_message(
+                sd_bus *bus,
+                pam_handle_t *handle,
+                const SessionContext *context,
+                bool avoid_pidfd,
+                sd_bus_message **ret) {
+
+        _cleanup_(sd_bus_message_unrefp) sd_bus_message *m = NULL;
+        _cleanup_close_ int pidfd = -EBADF;
+        int r;
+
+        assert(bus);
+        assert(handle);
+        assert(context);
+        assert(ret);
+
+        if (!avoid_pidfd) {
+                pidfd = pidfd_open(getpid_cached(), 0);
+                if (pidfd < 0 && !ERRNO_IS_NOT_SUPPORTED(errno) && !ERRNO_IS_PRIVILEGE(errno))
+                        return -errno;
+        }
+
+        r = bus_message_new_method_call(bus, &m, bus_login_mgr, pidfd >= 0 ? "CreateSessionWithPIDFD" : "CreateSession");
+        if (r < 0)
+                return r;
+
+        r = sd_bus_message_append(m,
+                                  pidfd >= 0 ? "uhsssssussbss" : "uusssssussbss",
+                                  (uint32_t) context->uid,
+                                  pidfd >= 0 ? pidfd : context->pid,
+                                  context->service,
+                                  context->type,
+                                  context->class,
+                                  context->desktop,
+                                  context->seat,
+                                  context->vtnr,
+                                  context->tty,
+                                  context->display,
+                                  context->remote,
+                                  context->remote_user,
+                                  context->remote_host);
+        if (r < 0)
+                return r;
+
+        if (pidfd >= 0) {
+                r = sd_bus_message_append(m, "t", UINT64_C(0));
+                if (r < 0)
+                        return r;
+        }
+
+        r = sd_bus_message_open_container(m, 'a', "(sv)");
+        if (r < 0)
+                return r;
+
+        r = append_session_memory_max(handle, m, context->memory_max);
+        if (r != PAM_SUCCESS)
+                return r;
+
+        r = append_session_runtime_max_sec(handle, m, context->runtime_max_sec);
+        if (r != PAM_SUCCESS)
+                return r;
+
+        r = append_session_tasks_max(handle, m, context->tasks_max);
+        if (r != PAM_SUCCESS)
+                return r;
+
+        r = append_session_cpu_weight(handle, m, context->cpu_weight);
+        if (r != PAM_SUCCESS)
+                return r;
+
+        r = append_session_io_weight(handle, m, context->io_weight);
+        if (r != PAM_SUCCESS)
+                return r;
+
+        r = sd_bus_message_close_container(m);
+        if (r < 0)
+                return r;
+
+        *ret = TAKE_PTR(m);
+        return 0;
+}
+
+_public_ PAM_EXTERN int pam_sm_open_session(
+                pam_handle_t *handle,
+                int flags,
+                int argc, const char **argv) {
+
+        /* Let's release the D-Bus connection once this function exits, after all the session might live
+         * quite a long time, and we are not going to process the bus connection in that time, so let's
+         * better close before the daemon kicks us off because we are not processing anything. */
+        _cleanup_(pam_bus_data_disconnectp) PamBusData *d = NULL;
+        _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
+        _cleanup_(sd_bus_message_unrefp) sd_bus_message *m = NULL, *reply = NULL;
+        const char
+                *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, *desktop_pam = NULL,
+                *memory_max = NULL, *tasks_max = NULL, *cpu_weight = NULL, *io_weight = NULL, *runtime_max_sec = NULL;
+        uint64_t default_capability_bounding_set = UINT64_MAX, default_capability_ambient_set = UINT64_MAX;
+        _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
+        _cleanup_(user_record_unrefp) UserRecord *ur = NULL;
+        int session_fd = -EBADF, existing, r;
+        bool debug = false, remote;
+        uint32_t vtnr = 0;
+        uid_t original_uid;
+
+        assert(handle);
+
+        if (parse_argv(handle,
+                       argc, argv,
+                       &class_pam,
+                       &type_pam,
+                       &desktop_pam,
+                       &debug,
+                       &default_capability_bounding_set,
+                       &default_capability_ambient_set) < 0)
+                return PAM_SESSION_ERR;
+
+        pam_debug_syslog(handle, debug, "pam-systemd initializing");
+
+        r = acquire_user_record(handle, &ur);
+        if (r != PAM_SUCCESS)
+                return r;
+
+        /* Make most of this a NOP on non-logind systems */
+        if (!logind_running())
+                goto success;
+
+        /* 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. */
+
+        r = pam_get_item(handle, PAM_SERVICE, (const void**) &service);
+        if (!IN_SET(r, PAM_BAD_ITEM, PAM_SUCCESS))
+                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to get PAM service: @PAMERR@");
+        if (streq_ptr(service, "systemd-user")) {
+                char rt[STRLEN("/run/user/") + DECIMAL_STR_MAX(uid_t)];
+
+                xsprintf(rt, "/run/user/"UID_FMT, ur->uid);
+                r = configure_runtime_directory(handle, ur, rt);
+                if (r != PAM_SUCCESS)
+                        return r;
+
+                goto success;
+        }
+
+        /* Otherwise, we ask logind to create a session for us */
+
+        r = pam_get_item(handle, PAM_XDISPLAY, (const void**) &display);
+        if (!IN_SET(r, PAM_BAD_ITEM, PAM_SUCCESS))
+                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to get PAM_XDISPLAY: @PAMERR@");
+        r = pam_get_item(handle, PAM_TTY, (const void**) &tty);
+        if (!IN_SET(r, PAM_BAD_ITEM, PAM_SUCCESS))
+                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to get PAM_TTY: @PAMERR@");
+        r = pam_get_item(handle, PAM_RUSER, (const void**) &remote_user);
+        if (!IN_SET(r, PAM_BAD_ITEM, PAM_SUCCESS))
+                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to get PAM_RUSER: @PAMERR@");
+        r = pam_get_item(handle, PAM_RHOST, (const void**) &remote_host);
+        if (!IN_SET(r, PAM_BAD_ITEM, PAM_SUCCESS))
+                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to get PAM_RHOST: @PAMERR@");
+
+        seat = getenv_harder(handle, "XDG_SEAT", NULL);
+        cvtnr = getenv_harder(handle, "XDG_VTNR", NULL);
+        type = getenv_harder(handle, "XDG_SESSION_TYPE", type_pam);
+        class = getenv_harder(handle, "XDG_SESSION_CLASS", class_pam);
+        desktop = getenv_harder(handle, "XDG_SESSION_DESKTOP", desktop_pam);
+
+        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 is setting PAM_TTY to "cron" for some reason (the commit carries no information why, but
+                 * probably because it wants to set it to something as pam_time/pam_access/… require PAM_TTY to be set
+                 * (as they otherwise even try to update it!) — but cron doesn't actually allocate a TTY for its forked
+                 * off processes.) */
+                type = "unspecified";
+                class = "background";
+                tty = NULL;
+
+        } else if (streq(tty, "ssh")) {
+                /* ssh has been setting PAM_TTY to "ssh" (for the same reason as cron does this, see above. For further
+                 * details look for "PAM_TTY_KLUDGE" in the openssh sources). */
+                type ="tty";
+                class = "user";
+                tty = NULL; /* This one is particularly sad, as this means that ssh sessions — even though usually
+                             * associated with a pty — won't be tracked by their tty in logind. This is because ssh
+                             * does the PAM session registration early for new connections, and registers a pty only
+                             * much later (this is because it doesn't know yet if it needs one at all, as whether to
+                             * register a pty or not is negotiated much later in the protocol). */
+
+        } else
+                /* Chop off leading /dev prefix that some clients specify, but others do not. */
+                tty = skip_dev_prefix(tty);
+
+        /* 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))
+                        (void) get_seat_from_display(display, &seat, &vtnr);
+                else if (streq(seat, "seat0"))
+                        (void) get_seat_from_display(display, NULL, &vtnr);
+        }
+
+        if (seat && !streq(seat, "seat0") && vtnr != 0) {
+                pam_debug_syslog(handle, 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);
+
+        r = pam_get_data(handle, "systemd.memory_max", (const void **)&memory_max);
+        if (!IN_SET(r, PAM_SUCCESS, PAM_NO_MODULE_DATA))
+                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to get PAM systemd.memory_max data: @PAMERR@");
+        r = pam_get_data(handle, "systemd.tasks_max",  (const void **)&tasks_max);
+        if (!IN_SET(r, PAM_SUCCESS, PAM_NO_MODULE_DATA))
+                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to get PAM systemd.tasks_max data: @PAMERR@");
+        r = pam_get_data(handle, "systemd.cpu_weight", (const void **)&cpu_weight);
+        if (!IN_SET(r, PAM_SUCCESS, PAM_NO_MODULE_DATA))
+                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to get PAM systemd.cpu_weight data: @PAMERR@");
+        r = pam_get_data(handle, "systemd.io_weight",  (const void **)&io_weight);
+        if (!IN_SET(r, PAM_SUCCESS, PAM_NO_MODULE_DATA))
+                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to get PAM systemd.io_weight data: @PAMERR@");
+        r = pam_get_data(handle, "systemd.runtime_max_sec", (const void **)&runtime_max_sec);
+        if (!IN_SET(r, PAM_SUCCESS, PAM_NO_MODULE_DATA))
+                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to get PAM systemd.runtime_max_sec data: @PAMERR@");
+
+        /* Talk to logind over the message bus */
+        r = pam_acquire_bus_connection(handle, "pam-systemd", &bus, &d);
+        if (r != PAM_SUCCESS)
+                return r;
+
+        pam_debug_syslog(handle, 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",
+                         ur->uid, getpid_cached(),
+                         strempty(service),
+                         type, class, strempty(desktop),
+                         strempty(seat), vtnr, strempty(tty), strempty(display),
+                         yes_no(remote), strempty(remote_user), strempty(remote_host));
+        pam_debug_syslog(handle, debug,
+                         "Session limits: "
+                         "memory_max=%s tasks_max=%s cpu_weight=%s io_weight=%s runtime_max_sec=%s",
+                         strna(memory_max), strna(tasks_max), strna(cpu_weight), strna(io_weight), strna(runtime_max_sec));
+
+        const SessionContext context = {
+                .uid = ur->uid,
+                .pid = 0,
+                .service = service,
+                .type = type,
+                .class = class,
+                .desktop = desktop,
+                .seat = seat,
+                .vtnr = vtnr,
+                .tty = tty,
+                .display = display,
+                .remote = remote,
+                .remote_user = remote_user,
+                .remote_host = remote_host,
+                .memory_max = memory_max,
+                .tasks_max = tasks_max,
+                .cpu_weight = cpu_weight,
+                .io_weight = io_weight,
+                .runtime_max_sec = runtime_max_sec,
+        };
+
+        r = create_session_message(bus,
+                                   handle,
+                                   &context,
+                                   /* avoid_pidfd = */ false,
+                                   &m);
+        if (r < 0)
+                return pam_bus_log_create_error(handle, r);
+
+        r = sd_bus_call(bus, m, LOGIN_SLOW_BUS_CALL_TIMEOUT_USEC, &error, &reply);
+        if (r < 0 && sd_bus_error_has_name(&error, SD_BUS_ERROR_UNKNOWN_METHOD)) {
+                sd_bus_error_free(&error);
+                pam_debug_syslog(handle, debug,
+                                 "CreateSessionWithPIDFD() API is not available, retrying with CreateSession().");
+
+                m = sd_bus_message_unref(m);
+                r = create_session_message(bus,
+                                           handle,
+                                           &context,
+                                           /* avoid_pidfd = */ true,
+                                           &m);
+                if (r < 0)
+                        return pam_bus_log_create_error(handle, r);
+
+                r = sd_bus_call(bus, m, LOGIN_SLOW_BUS_CALL_TIMEOUT_USEC, &error, &reply);
+        }
+        if (r < 0) {
+                if (sd_bus_error_has_name(&error, BUS_ERROR_SESSION_BUSY)) {
+                        /* We are already in a session, don't do anything */
+                        pam_debug_syslog(handle, debug,
+                                         "Not creating session: %s", bus_error_message(&error, r));
+                        goto success;
+                }
+
+                pam_syslog(handle, LOG_ERR,
+                           "Failed to create session: %s", bus_error_message(&error, r));
+                return PAM_SESSION_ERR;
+        }
+
+        r = sd_bus_message_read(reply,
+                                "soshusub",
+                                &id,
+                                &object_path,
+                                &runtime_path,
+                                &session_fd,
+                                &original_uid,
+                                &seat,
+                                &vtnr,
+                                &existing);
+        if (r < 0)
+                return pam_bus_log_parse_error(handle, r);
+
+        pam_debug_syslog(handle, 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 = update_environment(handle, "XDG_SESSION_ID", id);
+        if (r != PAM_SUCCESS)
+                return r;
+
+        if (original_uid == ur->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 = configure_runtime_directory(handle, ur, runtime_path);
+                if (r != PAM_SUCCESS)
+                        return r;
+        }
+
+        /* Most likely we got the session/type/class from environment variables, but might have gotten the data
+         * somewhere else (for example PAM module parameters). Let's now update the environment variables, so that this
+         * data is inherited into the session processes, and programs can rely on them to be initialized. */
+
+        r = update_environment(handle, "XDG_SESSION_TYPE", type);
+        if (r != PAM_SUCCESS)
+                return r;
+
+        r = update_environment(handle, "XDG_SESSION_CLASS", class);
+        if (r != PAM_SUCCESS)
+                return r;
+
+        r = update_environment(handle, "XDG_SESSION_DESKTOP", desktop);
+        if (r != PAM_SUCCESS)
+                return r;
+
+        r = update_environment(handle, "XDG_SEAT", seat);
+        if (r != PAM_SUCCESS)
+                return r;
+
+        if (vtnr > 0) {
+                char buf[DECIMAL_STR_MAX(vtnr)];
+                sprintf(buf, "%u", vtnr);
+
+                r = update_environment(handle, "XDG_VTNR", buf);
+                if (r != PAM_SUCCESS)
+                        return r;
+        }
+
+        r = pam_set_data(handle, "systemd.existing", INT_TO_PTR(!!existing), NULL);
+        if (r != PAM_SUCCESS)
+                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to install existing flag: @PAMERR@");
+
+        if (session_fd >= 0) {
+                _cleanup_close_ int fd = fcntl(session_fd, F_DUPFD_CLOEXEC, 3);
+                if (fd < 0)
+                        return pam_syslog_errno(handle, LOG_ERR, errno, "Failed to dup session fd: %m");
+
+                r = pam_set_data(handle, "systemd.session-fd", FD_TO_PTR(fd), NULL);
+                if (r != PAM_SUCCESS)
+                        return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to install session fd: @PAMERR@");
+                TAKE_FD(fd);
+        }
+
+success:
+        if (default_capability_ambient_set == UINT64_MAX)
+                default_capability_ambient_set = pick_default_capability_ambient_set(ur, service, seat);
+
+        return apply_user_record_settings(handle, ur, debug, default_capability_bounding_set, default_capability_ambient_set);
+}
+
+_public_ PAM_EXTERN int pam_sm_close_session(
+                pam_handle_t *handle,
+                int flags,
+                int argc, const char **argv) {
+
+        const void *existing = NULL;
+        bool debug = false;
+        const char *id;
+        int r;
+
+        assert(handle);
+
+        if (parse_argv(handle,
+                       argc, argv,
+                       NULL,
+                       NULL,
+                       NULL,
+                       &debug,
+                       NULL,
+                       NULL) < 0)
+                return PAM_SESSION_ERR;
+
+        pam_debug_syslog(handle, debug, "pam-systemd shutting down");
+
+        /* Only release session if it wasn't pre-existing when we
+         * tried to create it */
+        r = pam_get_data(handle, "systemd.existing", &existing);
+        if (!IN_SET(r, PAM_SUCCESS, PAM_NO_MODULE_DATA))
+                return pam_syslog_pam_error(handle, LOG_ERR, r,
+                                            "Failed to get PAM systemd.existing data: @PAMERR@");
+
+        id = pam_getenv(handle, "XDG_SESSION_ID");
+        if (id && !existing) {
+                _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
+                _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
+
+                /* 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 = pam_acquire_bus_connection(handle, "pam-systemd", &bus, NULL);
+                if (r != PAM_SUCCESS)
+                        return r;
+
+                r = bus_call_method(bus, bus_login_mgr, "ReleaseSession", &error, NULL, "s", id);
+                if (r < 0)
+                        return pam_syslog_pam_error(handle, LOG_ERR, PAM_SESSION_ERR,
+                                                    "Failed to release session: %s", bus_error_message(&error, r));
+        }
+
+        /* 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;
+}