machined: when opening a shell via machined, pass tty fds in

With this change we'll open the shell's tty right from machined and then
pass it to the transient unit we create. This way we make sure the pty
is opened exactly as long as the transient service is around, and no
longer, and vice versa. This way pty forwarders do not have to deal with
EIO problems due to vhangup, as the pty is open all the time from the
point we set things up to the point where the service goes away.

6 files changed, 82 insertions, 10 deletions

diff --git a/src/basic/terminal-util.c b/src/basic/terminal-util.c
index 50a86a331c..e9097d8ae5 100644
--- a/src/basic/terminal-util.c
+++ b/src/basic/terminal-util.c
@@ -1152,3 +1152,51 @@ int openpt_in_namespace(pid_t pid, int flags) {
 
         return receive_one_fd(pair[0], 0);
 }
+
+int open_terminal_in_namespace(pid_t pid, const char *name, int mode) {
+        _cleanup_close_ int pidnsfd = -1, mntnsfd = -1, usernsfd = -1, rootfd = -1;
+        _cleanup_close_pair_ int pair[2] = { -1, -1 };
+        siginfo_t si;
+        pid_t child;
+        int r;
+
+        r = namespace_open(pid, &pidnsfd, &mntnsfd, NULL, &usernsfd, &rootfd);
+        if (r < 0)
+                return r;
+
+        if (socketpair(AF_UNIX, SOCK_DGRAM, 0, pair) < 0)
+                return -errno;
+
+        child = fork();
+        if (child < 0)
+                return -errno;
+
+        if (child == 0) {
+                int master;
+
+                pair[0] = safe_close(pair[0]);
+
+                r = namespace_enter(pidnsfd, mntnsfd, -1, usernsfd, rootfd);
+                if (r < 0)
+                        _exit(EXIT_FAILURE);
+
+                master = open_terminal(name, mode|O_NOCTTY|O_CLOEXEC);
+                if (master < 0)
+                        _exit(EXIT_FAILURE);
+
+                if (send_one_fd(pair[1], master, 0) < 0)
+                        _exit(EXIT_FAILURE);
+
+                _exit(EXIT_SUCCESS);
+        }
+
+        pair[1] = safe_close(pair[1]);
+
+        r = wait_for_terminate(child, &si);
+        if (r < 0)
+                return r;
+        if (si.si_code != CLD_EXITED || si.si_status != EXIT_SUCCESS)
+                return -EIO;
+
+        return receive_one_fd(pair[0], 0);
+}
diff --git a/src/basic/terminal-util.h b/src/basic/terminal-util.h
index 050d0524a5..ee0b68b433 100644
--- a/src/basic/terminal-util.h
+++ b/src/basic/terminal-util.h
@@ -124,3 +124,4 @@ int ptsname_malloc(int fd, char **ret);
 int ptsname_namespace(int pty, char **ret);
 
 int openpt_in_namespace(pid_t pid, int flags);
+int open_terminal_in_namespace(pid_t pid, const char *name, int mode);
diff --git a/src/machine/machine-dbus.c b/src/machine/machine-dbus.c
index 21026829a9..6e41e92962 100644
--- a/src/machine/machine-dbus.c
+++ b/src/machine/machine-dbus.c
@@ -639,7 +639,7 @@ int bus_machine_method_open_shell(sd_bus_message *message, void *userdata, sd_bu
         _cleanup_free_ char *pty_name = NULL;
         _cleanup_bus_flush_close_unref_ sd_bus *allocated_bus = NULL;
         sd_bus *container_bus = NULL;
-        _cleanup_close_ int master = -1;
+        _cleanup_close_ int master = -1, slave = -1;
         _cleanup_strv_free_ char **env = NULL, **args = NULL;
         Machine *m = userdata;
         const char *p, *unit, *user, *path, *description, *utmp_id;
@@ -700,8 +700,11 @@ int bus_machine_method_open_shell(sd_bus_message *message, void *userdata, sd_bu
                 return r;
 
         p = path_startswith(pty_name, "/dev/pts/");
-        if (!p)
-                return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS, "PTS name %s is invalid", pty_name);
+        assert(p);
+
+        slave = machine_open_terminal(m, pty_name, O_RDWR|O_NOCTTY|O_CLOEXEC);
+        if (slave < 0)
+                return slave;
 
         utmp_id = path_startswith(pty_name, "/dev/");
         assert(utmp_id);
@@ -735,16 +738,14 @@ int bus_machine_method_open_shell(sd_bus_message *message, void *userdata, sd_bu
 
         description = strjoina("Shell for User ", isempty(user) ? "root" : user);
         r = sd_bus_message_append(tm,
-                                  "(sv)(sv)(sv)(sv)(sv)(sv)(sv)(sv)(sv)(sv)(sv)(sv)(sv)(sv)",
+                                  "(sv)(sv)(sv)(sv)(sv)(sv)(sv)(sv)(sv)(sv)(sv)(sv)",
                                   "Description", "s", description,
-                                  "StandardInput", "s", "tty",
-                                  "StandardOutput", "s", "tty",
-                                  "StandardError", "s", "tty",
-                                  "TTYPath", "s", pty_name,
+                                  "StandardInputFileDescriptor", "h", slave,
+                                  "StandardOutputFileDescriptor", "h", slave,
+                                  "StandardErrorFileDescriptor", "h", slave,
                                   "SendSIGHUP", "b", true,
                                   "IgnoreSIGPIPE", "b", false,
                                   "KillMode", "s", "mixed",
-                                  "TTYVHangup", "b", true,
                                   "TTYReset", "b", true,
                                   "UtmpIdentifier", "s", utmp_id,
                                   "UtmpMode", "s", "user",
@@ -845,6 +846,8 @@ int bus_machine_method_open_shell(sd_bus_message *message, void *userdata, sd_bu
         if (r < 0)
                 return r;
 
+        slave = safe_close(slave);
+
         r = sd_bus_message_new_method_return(message, &reply);
         if (r < 0)
                 return r;
diff --git a/src/machine/machine.c b/src/machine/machine.c
index 0f1942d1f4..7ab84607fb 100644
--- a/src/machine/machine.c
+++ b/src/machine/machine.c
@@ -572,6 +572,25 @@ int machine_openpt(Machine *m, int flags) {
         }
 }
 
+int machine_open_terminal(Machine *m, const char *path, int mode) {
+        assert(m);
+
+        switch (m->class) {
+
+        case MACHINE_HOST:
+                return open_terminal(path, mode);
+
+        case MACHINE_CONTAINER:
+                if (m->leader <= 0)
+                        return -EINVAL;
+
+                return open_terminal_in_namespace(m->leader, path, mode);
+
+        default:
+                return -EOPNOTSUPP;
+        }
+}
+
 MachineOperation *machine_operation_unref(MachineOperation *o) {
         if (!o)
                 return NULL;
diff --git a/src/machine/machine.h b/src/machine/machine.h
index 5f978289f2..ad7f2a162f 100644
--- a/src/machine/machine.h
+++ b/src/machine/machine.h
@@ -123,3 +123,4 @@ const char *kill_who_to_string(KillWho k) _const_;
 KillWho kill_who_from_string(const char *s) _pure_;
 
 int machine_openpt(Machine *m, int flags);
+int machine_open_terminal(Machine *m, const char *path, int mode);
diff --git a/src/machine/machinectl.c b/src/machine/machinectl.c
index e75b183328..0a21ab4415 100644
--- a/src/machine/machinectl.c
+++ b/src/machine/machinectl.c
@@ -1390,7 +1390,7 @@ static int shell_machine(int argc, char *argv[], void *userdata) {
         if (r < 0)
                 return bus_log_parse_error(r);
 
-        return process_forward(event, &forward, master, PTY_FORWARD_IGNORE_INITIAL_VHANGUP, machine);
+        return process_forward(event, &forward, master, 0, machine);
 }
 
 static int remove_image(int argc, char *argv[], void *userdata) {