378 lines
13 KiB
Diff
378 lines
13 KiB
Diff
From d897789b4dc7d115c915842eabf33ed3de20110a Mon Sep 17 00:00:00 2001
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From: Lennart Poettering <lennart@poettering.net>
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Date: Tue, 7 Aug 2018 13:49:34 +0200
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Subject: [PATCH] logind: optionally watch utmp for login data
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This allows us to determine the TTY an ssh session is for, which is
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useful to to proper idle detection for ssh sessions.
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Fixes: #9622
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(cherry picked from commit 3d0ef5c7e00155bc74f6f71c34cad518a4ff56ba)
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Related: #2122288
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---
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src/login/logind-core.c | 143 +++++++++++++++++++++++++++++++++++++
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src/login/logind-dbus.c | 5 ++
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src/login/logind-session.c | 24 +++++++
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src/login/logind-session.h | 14 +++-
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src/login/logind.c | 10 +++
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src/login/logind.h | 8 +++
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6 files changed, 203 insertions(+), 1 deletion(-)
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diff --git a/src/login/logind-core.c b/src/login/logind-core.c
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index 0ed812a2c8..7e33f8e6aa 100644
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--- a/src/login/logind-core.c
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+++ b/src/login/logind-core.c
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@@ -5,6 +5,9 @@
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#include <sys/ioctl.h>
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#include <sys/types.h>
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#include <linux/vt.h>
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+#if ENABLE_UTMP
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+#include <utmpx.h>
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+#endif
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#include "alloc-util.h"
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#include "bus-error.h"
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@@ -14,6 +17,7 @@
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#include "fd-util.h"
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#include "logind.h"
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#include "parse-util.h"
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+#include "path-util.h"
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#include "process-util.h"
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#include "strv.h"
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#include "terminal-util.h"
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@@ -692,3 +696,142 @@ bool manager_all_buttons_ignored(Manager *m) {
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return true;
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}
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+
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+int manager_read_utmp(Manager *m) {
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+#if ENABLE_UTMP
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+ int r;
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+
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+ assert(m);
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+
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+ if (utmpxname(_PATH_UTMPX) < 0)
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+ return log_error_errno(errno, "Failed to set utmp path to " _PATH_UTMPX ": %m");
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+
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+ setutxent();
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+
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+ for (;;) {
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+ _cleanup_free_ char *t = NULL;
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+ struct utmpx *u;
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+ const char *c;
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+ Session *s;
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+
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+ errno = 0;
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+ u = getutxent();
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+ if (!u) {
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+ if (errno != 0)
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+ log_warning_errno(errno, "Failed to read " _PATH_UTMPX ", ignoring: %m");
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+ r = 0;
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+ break;
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+ }
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+
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+ if (u->ut_type != USER_PROCESS)
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+ continue;
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+
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+ if (!pid_is_valid(u->ut_pid))
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+ continue;
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+
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+ t = strndup(u->ut_line, sizeof(u->ut_line));
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+ if (!t) {
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+ r = log_oom();
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+ break;
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+ }
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+
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+ c = path_startswith(t, "/dev/");
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+ if (c) {
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+ r = free_and_strdup(&t, c);
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+ if (r < 0) {
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+ log_oom();
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+ break;
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+ }
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+ }
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+
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+ if (isempty(t))
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+ continue;
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+
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+ s = hashmap_get(m->sessions_by_leader, PID_TO_PTR(u->ut_pid));
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+ if (!s)
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+ continue;
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+
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+ if (s->tty_validity == TTY_FROM_UTMP && !streq_ptr(s->tty, t)) {
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+ /* This may happen on multiplexed SSH connection (i.e. 'SSH connection sharing'). In
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+ * this case PAM and utmp sessions don't match. In such a case let's invalidate the TTY
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+ * information and never acquire it again. */
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+
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+ s->tty = mfree(s->tty);
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+ s->tty_validity = TTY_UTMP_INCONSISTENT;
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+ log_debug("Session '%s' has inconsistent TTY information, dropping TTY information.", s->id);
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+ continue;
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+ }
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+
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+ /* Never override what we figured out once */
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+ if (s->tty || s->tty_validity >= 0)
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+ continue;
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+
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+ s->tty = TAKE_PTR(t);
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+ s->tty_validity = TTY_FROM_UTMP;
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+ log_debug("Acquired TTY information '%s' from utmp for session '%s'.", s->tty, s->id);
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+ }
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+
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+ endutxent();
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+ return r;
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+#else
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+ return 0
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+#endif
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+}
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+
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+#if ENABLE_UTMP
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+static int manager_dispatch_utmp(sd_event_source *s, const struct inotify_event *event, void *userdata) {
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+ Manager *m = userdata;
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+
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+ assert(m);
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+
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+ /* If there's indication the file itself might have been removed or became otherwise unavailable, then let's
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+ * reestablish the watch on whatever there's now. */
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+ if ((event->mask & (IN_ATTRIB|IN_DELETE_SELF|IN_MOVE_SELF|IN_Q_OVERFLOW|IN_UNMOUNT)) != 0)
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+ manager_connect_utmp(m);
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+
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+ (void) manager_read_utmp(m);
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+ return 0;
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+}
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+#endif
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+
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+void manager_connect_utmp(Manager *m) {
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+#if ENABLE_UTMP
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+ sd_event_source *s = NULL;
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+ int r;
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+
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+ assert(m);
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+
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+ /* Watch utmp for changes via inotify. We do this to deal with tools such as ssh, which will register the PAM
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+ * session early, and acquire a TTY only much later for the connection. Thus during PAM the TTY won't be known
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+ * yet. ssh will register itself with utmp when it finally acquired the TTY. Hence, let's make use of this, and
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+ * watch utmp for the TTY asynchronously. We use the PAM session's leader PID as key, to find the right entry.
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+ *
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+ * Yes, relying on utmp is pretty ugly, but it's good enough for informational purposes, as well as idle
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+ * detection (which, for tty sessions, relies on the TTY used) */
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+
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+ r = sd_event_add_inotify(m->event, &s, _PATH_UTMPX, IN_MODIFY|IN_MOVE_SELF|IN_DELETE_SELF|IN_ATTRIB, manager_dispatch_utmp, m);
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+ if (r < 0)
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+ log_full_errno(r == -ENOENT ? LOG_DEBUG: LOG_WARNING, r, "Failed to create inotify watch on " _PATH_UTMPX ", ignoring: %m");
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+ else {
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+ r = sd_event_source_set_priority(s, SD_EVENT_PRIORITY_IDLE);
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+ if (r < 0)
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+ log_warning_errno(r, "Failed to adjust utmp event source priority, ignoring: %m");
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+
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+ (void) sd_event_source_set_description(s, "utmp");
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+ }
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+
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+ sd_event_source_unref(m->utmp_event_source);
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+ m->utmp_event_source = s;
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+#endif
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+}
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+
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+void manager_reconnect_utmp(Manager *m) {
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+#if ENABLE_UTMP
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+ assert(m);
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+
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+ if (m->utmp_event_source)
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+ return;
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+
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+ manager_connect_utmp(m);
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+#endif
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+}
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diff --git a/src/login/logind-dbus.c b/src/login/logind-dbus.c
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index 1bb152bc20..0248042308 100644
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--- a/src/login/logind-dbus.c
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+++ b/src/login/logind-dbus.c
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@@ -772,6 +772,9 @@ static int method_create_session(sd_bus_message *message, void *userdata, sd_bus
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} while (hashmap_get(m->sessions, id));
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}
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+ /* If we are not watching utmp aleady, try again */
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+ manager_reconnect_utmp(m);
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+
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r = manager_add_user_by_uid(m, uid, &user);
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if (r < 0)
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goto fail;
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@@ -795,6 +798,8 @@ static int method_create_session(sd_bus_message *message, void *userdata, sd_bus
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r = -ENOMEM;
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goto fail;
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}
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+
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+ session->tty_validity = TTY_FROM_PAM;
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}
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if (!isempty(display)) {
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diff --git a/src/login/logind-session.c b/src/login/logind-session.c
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index 1143a834a4..d666f86d3f 100644
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--- a/src/login/logind-session.c
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+++ b/src/login/logind-session.c
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@@ -56,6 +56,7 @@ int session_new(Session **ret, Manager *m, const char *id) {
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.fifo_fd = -1,
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.vtfd = -1,
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.audit_id = AUDIT_SESSION_INVALID,
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+ .tty_validity = _TTY_VALIDITY_INVALID,
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};
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s->state_file = strappend("/run/systemd/sessions/", id);
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@@ -219,6 +220,9 @@ int session_save(Session *s) {
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if (s->tty)
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fprintf(f, "TTY=%s\n", s->tty);
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+ if (s->tty_validity >= 0)
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+ fprintf(f, "TTY_VALIDITY=%s\n", tty_validity_to_string(s->tty_validity));
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+
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if (s->display)
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fprintf(f, "DISPLAY=%s\n", s->display);
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@@ -355,6 +359,7 @@ static int session_load_devices(Session *s, const char *devices) {
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int session_load(Session *s) {
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_cleanup_free_ char *remote = NULL,
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*seat = NULL,
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+ *tty_validity = NULL,
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*vtnr = NULL,
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*state = NULL,
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*position = NULL,
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@@ -380,6 +385,7 @@ int session_load(Session *s) {
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"FIFO", &s->fifo_path,
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"SEAT", &seat,
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"TTY", &s->tty,
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+ "TTY_VALIDITY", &tty_validity,
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"DISPLAY", &s->display,
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"REMOTE_HOST", &s->remote_host,
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"REMOTE_USER", &s->remote_user,
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@@ -456,6 +462,16 @@ int session_load(Session *s) {
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seat_claim_position(s->seat, s, npos);
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}
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+ if (tty_validity) {
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+ TTYValidity v;
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+
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+ v = tty_validity_from_string(tty_validity);
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+ if (v < 0)
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+ log_debug("Failed to parse TTY validity: %s", tty_validity);
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+ else
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+ s->tty_validity = v;
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+ }
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+
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if (leader) {
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if (parse_pid(leader, &s->leader) >= 0)
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(void) audit_session_from_pid(s->leader, &s->audit_id);
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@@ -1368,3 +1384,11 @@ static const char* const kill_who_table[_KILL_WHO_MAX] = {
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};
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DEFINE_STRING_TABLE_LOOKUP(kill_who, KillWho);
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+
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+static const char* const tty_validity_table[_TTY_VALIDITY_MAX] = {
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+ [TTY_FROM_PAM] = "from-pam",
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+ [TTY_FROM_UTMP] = "from-utmp",
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+ [TTY_UTMP_INCONSISTENT] = "utmp-inconsistent",
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+};
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+
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+DEFINE_STRING_TABLE_LOOKUP(tty_validity, TTYValidity);
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diff --git a/src/login/logind-session.h b/src/login/logind-session.h
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index 9bd0c96a03..7da845cea3 100644
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--- a/src/login/logind-session.h
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+++ b/src/login/logind-session.h
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@@ -46,6 +46,14 @@ enum KillWho {
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_KILL_WHO_INVALID = -1
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};
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+typedef enum TTYValidity {
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+ TTY_FROM_PAM,
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+ TTY_FROM_UTMP,
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+ TTY_UTMP_INCONSISTENT, /* may happen on ssh sessions with multiplexed TTYs */
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+ _TTY_VALIDITY_MAX,
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+ _TTY_VALIDITY_INVALID = -1,
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+} TTYValidity;
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+
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struct Session {
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Manager *manager;
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@@ -60,8 +68,9 @@ struct Session {
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dual_timestamp timestamp;
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- char *tty;
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char *display;
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+ char *tty;
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+ TTYValidity tty_validity;
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bool remote;
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char *remote_user;
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@@ -159,6 +168,9 @@ SessionClass session_class_from_string(const char *s) _pure_;
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const char *kill_who_to_string(KillWho k) _const_;
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KillWho kill_who_from_string(const char *s) _pure_;
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+const char* tty_validity_to_string(TTYValidity t) _const_;
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+TTYValidity tty_validity_from_string(const char *s) _pure_;
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+
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int session_prepare_vt(Session *s);
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void session_restore_vt(Session *s);
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void session_leave_vt(Session *s);
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diff --git a/src/login/logind.c b/src/login/logind.c
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index 6c208c8e89..25de9a6ab2 100644
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--- a/src/login/logind.c
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+++ b/src/login/logind.c
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@@ -132,6 +132,10 @@ static Manager* manager_unref(Manager *m) {
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sd_event_source_unref(m->udev_button_event_source);
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sd_event_source_unref(m->lid_switch_ignore_event_source);
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+#if ENABLE_UTMP
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+ sd_event_source_unref(m->utmp_event_source);
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+#endif
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+
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safe_close(m->console_active_fd);
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udev_monitor_unref(m->udev_seat_monitor);
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@@ -1095,6 +1099,9 @@ static int manager_startup(Manager *m) {
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if (r < 0)
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return log_error_errno(r, "Failed to register SIGHUP handler: %m");
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+ /* Connect to utmp */
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+ manager_connect_utmp(m);
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+
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/* Connect to console */
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r = manager_connect_console(m);
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if (r < 0)
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@@ -1150,6 +1157,9 @@ static int manager_startup(Manager *m) {
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/* Reserve the special reserved VT */
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manager_reserve_vt(m);
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+ /* Read in utmp if it exists */
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+ manager_read_utmp(m);
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+
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/* And start everything */
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HASHMAP_FOREACH(seat, m->seats, i)
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seat_start(seat);
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diff --git a/src/login/logind.h b/src/login/logind.h
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index d29b01c75b..bb127bf4a5 100644
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--- a/src/login/logind.h
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+++ b/src/login/logind.h
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@@ -43,6 +43,10 @@ struct Manager {
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sd_event_source *udev_vcsa_event_source;
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sd_event_source *udev_button_event_source;
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+#if ENABLE_UTMP
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+ sd_event_source *utmp_event_source;
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+#endif
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+
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int console_active_fd;
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unsigned n_autovts;
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@@ -150,6 +154,10 @@ bool manager_is_docked_or_external_displays(Manager *m);
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bool manager_is_on_external_power(void);
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bool manager_all_buttons_ignored(Manager *m);
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+int manager_read_utmp(Manager *m);
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+void manager_connect_utmp(Manager *m);
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+void manager_reconnect_utmp(Manager *m);
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+
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extern const sd_bus_vtable manager_vtable[];
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int match_job_removed(sd_bus_message *message, void *userdata, sd_bus_error *error);
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