systemctl: hook up new install logic

[elogind.git] / src / spawn-agent.c

diff --git a/src/spawn-agent.c b/src/spawn-agent.c
new file mode 100644 (file)
index 0000000..2de2530
--- /dev/null
+++ b/src/spawn-agent.c
@@ -0,0 +1,120 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2011 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 2 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <sys/types.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <sys/prctl.h>
+#include <signal.h>
+#include <fcntl.h>
+
+#include "log.h"
+#include "util.h"
+#include "spawn-agent.h"
+
+static pid_t agent_pid = 0;
+
+void agent_open(void) {
+        pid_t parent_pid;
+
+        if (agent_pid > 0)
+                return;
+
+        /* We check STDIN here, not STDOUT, since this is about input,
+         * not output */
+        if (!isatty(STDIN_FILENO))
+                return;
+
+        parent_pid = getpid();
+
+        /* Spawns a temporary TTY agent, making sure it goes away when
+         * we go away */
+
+        agent_pid = fork();
+        if (agent_pid < 0) {
+                log_error("Failed to fork agent: %m");
+                return;
+        }
+
+        if (agent_pid == 0) {
+                /* In the child */
+
+                int fd;
+                bool stdout_is_tty, stderr_is_tty;
+
+                /* Make sure the agent goes away when the parent dies */
+                if (prctl(PR_SET_PDEATHSIG, SIGTERM) < 0)
+                        _exit(EXIT_FAILURE);
+
+                /* Check whether our parent died before we were able
+                 * to set the death signal */
+                if (getppid() != parent_pid)
+                        _exit(EXIT_SUCCESS);
+
+                /* Don't leak fds to the agent */
+                close_all_fds(NULL, 0);
+
+                stdout_is_tty = isatty(STDOUT_FILENO);
+                stderr_is_tty = isatty(STDERR_FILENO);
+
+                if (!stdout_is_tty || !stderr_is_tty) {
+                        /* Detach from stdout/stderr. and reopen
+                         * /dev/tty for them. This is important to
+                         * ensure that when systemctl is started via
+                         * popen() or a similar call that expects to
+                         * read EOF we actually do generate EOF and
+                         * not delay this indefinitely by because we
+                         * keep an unused copy of stdin around. */
+                        fd = open("/dev/tty", O_WRONLY);
+                        if (fd < 0) {
+                                log_error("Failed to open /dev/tty: %m");
+                                _exit(EXIT_FAILURE);
+                        }
+
+                        if (!stdout_is_tty)
+                                dup2(fd, STDOUT_FILENO);
+
+                        if (!stderr_is_tty)
+                                dup2(fd, STDERR_FILENO);
+
+                        if (fd > 2)
+                                close(fd);
+                }
+
+                execl(SYSTEMD_TTY_ASK_PASSWORD_AGENT_BINARY_PATH, SYSTEMD_TTY_ASK_PASSWORD_AGENT_BINARY_PATH, "--watch", NULL);
+
+                log_error("Unable to execute agent: %m");
+                _exit(EXIT_FAILURE);
+        }
+}
+
+void agent_close(void) {
+
+        if (agent_pid <= 0)
+                return;
+
+        /* Inform agent that we are done */
+        kill(agent_pid, SIGTERM);
+        kill(agent_pid, SIGCONT);
+        wait_for_terminate(agent_pid, NULL);
+        agent_pid = 0;
+}