write: query logind for list of users with tty (#2088)

util-linux · May 31, 2023 · 289653b · 289653b
1 parent 010c443
commit 289653b
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Showing 2 changed files with 123 additions and 11 deletions.
diff --git a/term-utils/Makemodule.am b/term-utils/Makemodule.am
@@ -126,6 +126,10 @@ write_SOURCES = term-utils/write.c
 write_CFLAGS = $(SUID_CFLAGS) $(AM_CFLAGS)
 write_LDFLAGS = $(SUID_LDFLAGS) $(AM_LDFLAGS)
 write_LDADD = $(LDADD) libcommon.la
+if HAVE_SYSTEMD
+write_LDADD += $(SYSTEMD_LIBS)
+write_CFLAGS += $(SYSTEMD_CFLAGS)
+endif
 
 if USE_TTY_GROUP
 if MAKEINSTALL_DO_CHOWN

diff --git a/term-utils/write.c b/term-utils/write.c
@@ -59,6 +59,11 @@
 #include <unistd.h>
 #include <utmpx.h>
 
+#if defined(USE_SYSTEMD) && HAVE_DECL_SD_SESSION_GET_USERNAME == 1
+# include <systemd/sd-login.h>
+# include <systemd/sd-daemon.h>
+#endif
+
 #include "c.h"
 #include "carefulputc.h"
 #include "closestream.h"
@@ -131,19 +136,56 @@ static int check_utmp(const struct write_control *ctl)
 {
 	struct utmpx *u;
 	int res = 1;
-
-	utmpxname(_PATH_UTMP);
-	setutxent();
-
-	while ((u = getutxent())) {
-		if (strncmp(ctl->dst_login, u->ut_user, sizeof(u->ut_user)) == 0 &&
-		    strncmp(ctl->dst_tty_name, u->ut_line, sizeof(u->ut_line)) == 0) {
-			res = 0;
-			break;
+#if defined(USE_SYSTEMD) && HAVE_DECL_SD_SESSION_GET_USERNAME == 1
+	if (sd_booted() > 0) {
+		char **sessions_list;
+		int sessions = sd_get_sessions(&sessions_list);
+		if (sessions < 0)
+			errx(EXIT_FAILURE, _("error getting sessions: %s"),
+				strerror(-sessions));
+
+		for (int i = 0; i < sessions; i++) {
+
+			char *name, *tty;
+			int r;
+
+			if ((r = sd_session_get_username(sessions_list[i], &name)) < 0)
+				errx(EXIT_FAILURE, _("get user name failed: %s"), strerror (-r));
+			if (sd_session_get_tty(sessions_list[i], &tty) < 0) {
+				free(name);
+				continue;
+			}
+
+			if  (strcmp(ctl->dst_login, name) == 0 &&
+					strcmp(ctl->dst_tty_name, tty) == 0) {
+				free(name);
+				free(tty);
+				res = 0;
+				break;
+			}
+			free(name);
+			free(tty);
+		}
+		for (int i = 0; i < sessions; i++)
+			free(sessions_list[i]);
+		free(sessions_list);
+	} else {
+#endif
+		utmpxname(_PATH_UTMP);
+		setutxent();
+
+		while ((u = getutxent())) {
+			if (strncmp(ctl->dst_login, u->ut_user, sizeof(u->ut_user)) == 0 &&
+		    		strncmp(ctl->dst_tty_name, u->ut_line, sizeof(u->ut_line)) == 0) {
+				res = 0;
+				break;
+			}
 		}
-	}
 
-	endutxent();
+		endutxent();
+#if defined(USE_SYSTEMD) && HAVE_DECL_SD_SESSION_GET_USERNAME == 1
+	}
+#endif
 	return res;
 }
 
@@ -163,6 +205,69 @@ static void search_utmp(struct write_control *ctl)
 	struct utmpx *u;
 	time_t best_atime = 0, tty_atime;
 	int num_ttys = 0, valid_ttys = 0, tty_writeable = 0, user_is_me = 0;
+
+#if defined(USE_SYSTEMD) && HAVE_DECL_SD_SESSION_GET_USERNAME == 1
+	if (sd_booted() > 0) {
+		char path[256];
+		char **sessions_list;
+		int sessions = sd_get_sessions(&sessions_list);
+		if (sessions < 0)
+			errx(EXIT_FAILURE, _("error getting sessions: %s"),
+			     strerror(-sessions));
+
+		for (int i = 0; i < sessions; i++) {
+			char *name, *tty;
+			int r;
+
+			if ((r = sd_session_get_username(sessions_list[i], &name)) < 0)
+				errx(EXIT_FAILURE, _("get user name failed: %s"), strerror (-r));
+
+			if  (strcmp(ctl->dst_login, name) != 0) {
+				free(name);
+				continue;
+			}
+
+			if (sd_session_get_tty(sessions_list[i], &tty) < 0) {
+				free(name);
+				continue;
+			}
+
+			num_ttys++;
+			snprintf(path, sizeof(path), "/dev/%s", tty);
+			if (check_tty(path, &tty_writeable, &tty_atime, 0)) {
+				/* bad term? skip */
+				free(name);
+				free(tty);
+				continue;
+			}
+			if (ctl->src_uid && !tty_writeable) {
+				/* skip ttys with msgs off */
+				free(name);
+				free(tty);
+				continue;
+			}
+			if (strcmp(tty, ctl->src_tty_name) == 0) {
+				user_is_me = 1;
+				free(name);
+				free(tty);
+				/* don't write to yourself */
+				continue;
+			}
+			valid_ttys++;
+			if (best_atime < tty_atime) {
+				best_atime = tty_atime;
+				free(ctl->dst_tty_path);
+				ctl->dst_tty_path = xstrdup(path);
+				ctl->dst_tty_name = ctl->dst_tty_path + 5;
+			}
+			free(name);
+			free(tty);
+		}
+		for (int i = 0; i < sessions; i++)
+			free(sessions_list[i]);
+		free(sessions_list);
+	} else {
+#endif
 	char path[sizeof(u->ut_line) + 6];
 
 	utmpxname(_PATH_UTMP);
@@ -197,6 +302,9 @@ static void search_utmp(struct write_control *ctl)
 	}
 
 	endutxent();
+#if defined(USE_SYSTEMD) && HAVE_DECL_SD_SESSION_GET_USERNAME == 1
+	}
+#endif
 	if (num_ttys == 0)
 		errx(EXIT_FAILURE, _("%s is not logged in"), ctl->dst_login);
 	if (valid_ttys == 0) {