systemctl: make sure the tty agent does not retain a copy of stdio

https://bugzilla.redhat.com/show_bug.cgi?id=674916

2 files changed, 29 insertions, 2 deletions

diff --git a/src/systemctl.c b/src/systemctl.c
index 8cdc01aa49..66903aba28 100644
--- a/src/systemctl.c
+++ b/src/systemctl.c
@@ -151,13 +151,15 @@ static void spawn_ask_password_agent(void) {
 
         if (child == 0) {
                 /* In the child */
-
                 const char * const args[] = {
                         SYSTEMD_TTY_ASK_PASSWORD_AGENT_BINARY_PATH,
                         "--watch",
                         NULL
                 };
 
+                int fd;
+
+                /* Make sure the agent goes away when the parent dies */
                 if (prctl(PR_SET_PDEATHSIG, SIGTERM) < 0)
                         _exit(EXIT_FAILURE);
 
@@ -166,6 +168,31 @@ static void spawn_ask_password_agent(void) {
                 if (getppid() != parent)
                         _exit(EXIT_SUCCESS);
 
+                /* Don't leak fds to the agent */
+                close_all_fds(NULL, 0);
+
+                /* Detach from stdin/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. */
+                if ((fd = open("/dev/tty", O_RDWR|O_CLOEXEC|O_NONBLOCK)) < 0) {
+                        log_error("Failed to open /dev/tty: %m");
+                        _exit(EXIT_FAILURE);
+                }
+
+                close(STDIN_FILENO);
+                close(STDOUT_FILENO);
+                close(STDERR_FILENO);
+
+                dup2(fd, STDIN_FILENO);
+                dup2(fd, STDOUT_FILENO);
+                dup2(fd, STDERR_FILENO);
+
+                if (fd > 2)
+                        close(fd);
+
                 execv(args[0], (char **) args);
                 _exit(EXIT_FAILURE);
         }
diff --git a/src/tty-ask-password-agent.c b/src/tty-ask-password-agent.c
index c3c5f7a8b6..00496e7119 100644
--- a/src/tty-ask-password-agent.c
+++ b/src/tty-ask-password-agent.c
@@ -83,7 +83,7 @@ static int ask_password_plymouth(const char *message, usec_t until, const char *
         sa.sa.sa_family = AF_UNIX;
         strncpy(sa.un.sun_path+1, "/org/freedesktop/plymouthd", sizeof(sa.un.sun_path)-1);
         if (connect(fd, &sa.sa, offsetof(struct sockaddr_un, sun_path) + 1 + strlen(sa.un.sun_path+1)) < 0) {
-                log_error("FIALED TO CONNECT: %m");
+                log_error("FAILED TO CONNECT: %m");
                 r = -errno;
                 goto finish;
         }