</para>
<para>
Previous versions of <command>lxc-attach</command> simply attached to the
- specified namespaces of a container and ran a shell or the specified
- command without allocating a pseudo terminal. This made them vulnerable to
+ specified namespaces of a container and ran a shell or the specified command
+ without first allocating a pseudo terminal. This made them vulnerable to
input faking via a TIOCSTI <command>ioctl</command> call after switching
between userspace execution contexts with different privilege levels. Newer
versions of <command>lxc-attach</command> will try to allocate a pseudo
- terminal master/slave pair and attach any standard file descriptors which
- refer to a terminal to the slave side of the pseudo terminal before
- executing a shell or command. <command>lxc-attach</command> will first try
- to allocate a pseudo terminal in the container. Should this fail it will try
- to allocate a pseudo terminal on the host before finally giving up. Note,
- that if none of the standard file descriptors refer to a terminal
- <command>lxc-attach</command> will not try to allocate a pseudo terminal.
- Instead it will simply attach to the containers namespaces and run a shell
- or the specified command.
+ terminal master/slave pair on the host and attach any standard file
+ descriptors which refer to a terminal to the slave side of the pseudo
+ terminal before executing a shell or command. Note, that if none of the
+ standard file descriptors refer to a terminal <command>lxc-attach</command>
+ will not try to allocate a pseudo terminal. Instead it will simply attach
+ to the containers namespaces and run a shell or the specified command.
</para>
</refsect1>
struct wrapargs {
lxc_attach_options_t *options;
lxc_attach_command_t *command;
- struct lxc_tty_state *ts;
struct lxc_console *console;
int ptyfd;
};
return 0;
}
-/* Minimalistic forkpty() implementation. */
-static pid_t fork_pty(int *masterfd)
-{
- int master, slave;
- int ret = openpty(&master, &slave, NULL, NULL, NULL);
- if (ret < 0)
- return -1;
-
- pid_t pid = fork();
-
- if (pid < 0) {
- close(master);
- close(slave);
- return -1;
- } else if (pid == 0) {
- close(master);
- if (login_pty(slave) < 0)
- _exit(-1); /* closes fds */
- return 0;
- } else {
- *masterfd = master;
- close(slave);
- return pid;
- }
-}
-
-/*
- * This is probably redundant but just so that intentions can be checked against
- * code for future modifications. Here is what this is supposed to achieve:
- * Since we fork() in pty_in_container() the shell that is run on the slave side
- * of the pty is the grandchild of c->attach() in main(). But what we probably
- * are interested in is the exit code of the grandchild. So we wait for the
- * grandchild to change status and return its exit code from this function. We
- * thereby make the exit code of the grandchild the exit code of the child and
- * allow the grandparent to see the exit code of the grandchild by waiting on
- * the pid of the child to change status:
- *
- * grandchild: lxc_attach_run_command()/lxc_attach_run_shell()
- *
- * child: pty_in_container()
- * - perform waitpid() on pid returned by lxc_attach_run_command() or
- * lxc_attach_run_shell()
- *
- * grandparent: c->attach()
- * - return pid of pty_in_container() in pid argument.
- *
- * main()
- * - perform waitpid() on pid returned in pid argument of c->attach()
- */
-static int pty_in_container(void *p)
-{
- int ret;
- int pid = -1;
- int master = -1;
- struct wrapargs *args = p;
-
- INFO("Trying to allocate a pty in the container.");
-
- if (!isatty(args->ptyfd)) {
- ERROR("stdin is not a tty");
- return -1;
- }
-
- /* Get termios from one of the stdfds. */
- struct termios oldtios;
- ret = lxc_setup_tios(args->ptyfd, &oldtios);
- if (ret < 0)
- return -1;
-
- /* Create master/slave fd pair for pty. */
- pid = fork_pty(&master);
- if (pid < 0)
- goto err1;
-
- /* Pass windowsize from one of the stdfds to the current masterfd. */
- lxc_console_winsz(args->ptyfd, master);
-
- /* Run shell/command on slave side of pty. */
- if (pid == 0) {
- if (args->command->program)
- lxc_attach_run_command(args->command);
- else
- lxc_attach_run_shell(NULL);
-
- return -1;
- }
-
- /*
- * For future reference: Must use process_lock() when called from a
- * threaded context.
- */
- args->ts = lxc_console_sigwinch_init(args->ptyfd, master);
- if (!args->ts) {
- ret = -1;
- goto err2;
- }
- args->ts->escape = -1;
- args->ts->stdoutfd = STDOUT_FILENO;
- args->ts->winch_proxy = NULL;
-
- struct lxc_epoll_descr descr;
- ret = lxc_mainloop_open(&descr);
- if (ret) {
- ERROR("failed to create mainloop");
- goto err3;
- }
-
- /* Register sigwinch handler in mainloop. */
- ret = lxc_mainloop_add_handler(&descr, args->ts->sigfd,
- lxc_console_cb_sigwinch_fd, args->ts);
- if (ret) {
- ERROR("failed to add handler for SIGWINCH fd");
- goto err4;
- }
-
- /* Register i/o callbacks in mainloop. */
- ret = lxc_mainloop_add_handler(&descr, args->ts->stdinfd,
- lxc_console_cb_tty_stdin, args->ts);
- if (ret) {
- ERROR("failed to add handler for stdinfd");
- goto err4;
- }
-
- ret = lxc_mainloop_add_handler(&descr, args->ts->masterfd,
- lxc_console_cb_tty_master, args->ts);
- if (ret) {
- ERROR("failed to add handler for masterfd");
- goto err4;
- }
-
- ret = lxc_mainloop(&descr, -1);
- if (ret) {
- ERROR("mainloop returned an error");
- goto err4;
- }
-
-err4:
- lxc_mainloop_close(&descr);
-err3:
- lxc_console_sigwinch_fini(args->ts);
-err2:
- close(args->ts->masterfd);
-err1:
- tcsetattr(args->ptyfd, TCSAFLUSH, &oldtios);
-
- ret = lxc_wait_for_pid_status(pid);
- if (ret < 0)
- return ret;
-
- if (WIFEXITED(ret))
- return WEXITSTATUS(ret);
-
- return -1;
-}
-
-static int pty_on_host_callback(void *p)
+static int get_pty_on_host_callback(void *p)
{
struct wrapargs *wrap = p;
return -1;
}
-static int pty_on_host(struct lxc_container *c, struct wrapargs *wrap, int *pid)
+static int get_pty_on_host(struct lxc_container *c, struct wrapargs *wrap, int *pid)
{
int ret = -1;
struct wrapargs *args = wrap;
/* Send wrapper function on its way. */
wrap->console = &conf->console;
- if (c->attach(c, pty_on_host_callback, wrap, wrap->options, pid) < 0)
+ if (c->attach(c, get_pty_on_host_callback, wrap, wrap->options, pid) < 0)
goto err1;
close(conf->console.slave); /* Close slave side. */
int main(int argc, char *argv[])
{
int ret = -1;
+ int wexit = 0;
pid_t pid;
lxc_attach_options_t attach_options = LXC_ATTACH_OPTIONS_DEFAULT;
lxc_attach_command_t command = (lxc_attach_command_t){.program = NULL};
wrap.ptyfd = STDOUT_FILENO;
else if (isatty(STDERR_FILENO))
wrap.ptyfd = STDERR_FILENO;
- ret = c->attach(c, pty_in_container, &wrap, &attach_options, &pid);
- if (ret < 0)
- ret = pty_on_host(c, &wrap, &pid);
+ ret = get_pty_on_host(c, &wrap, &pid);
} else {
if (my_args.argc > 1)
ret = c->attach(c, lxc_attach_run_command, &command, &attach_options, &pid);
ret = c->attach(c, lxc_attach_run_shell, NULL, &attach_options, &pid);
}
- lxc_container_put(c);
-
if (ret < 0)
- exit(EXIT_FAILURE);
+ goto out;
ret = lxc_wait_for_pid_status(pid);
if (ret < 0)
- exit(EXIT_FAILURE);
+ goto out;
if (WIFEXITED(ret))
- return WEXITSTATUS(ret);
-
+ wexit = WEXITSTATUS(ret);
+out:
+ lxc_container_put(c);
+ if (ret >= 0)
+ exit(wexit);
exit(EXIT_FAILURE);
}
projects / thirdparty / lxc.git / commitdiff
