/*
* Sleep in select() until we can do something. This will initialize the
* select masks. Upon return, the masks will indicate which descriptors
* have data or can accept data. Optionally, a maximum time can be specified
* for the duration of the wait (0 = infinite).
*/
static void
wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
u_int *nallocp, u_int64_t max_time_milliseconds)
{
struct timeval tv, *tvp;
int ret;
time_t minwait_secs = 0;
int client_alive_scheduled = 0;
int program_alive_scheduled = 0;
/* Allocate and update select() masks for channel descriptors. */
channel_prepare_select(readsetp, writesetp, maxfdp, nallocp,
&minwait_secs, 0);
if (minwait_secs != 0)
max_time_milliseconds = MIN(max_time_milliseconds,
(u_int)minwait_secs * 1000);
/*
* if using client_alive, set the max timeout accordingly,
* and indicate that this particular timeout was for client
* alive by setting the client_alive_scheduled flag.
*
* this could be randomized somewhat to make traffic
* analysis more difficult, but we're not doing it yet.
*/
if (compat20 &&
max_time_milliseconds == 0 && options.client_alive_interval) {
client_alive_scheduled = 1;
max_time_milliseconds =
(u_int64_t)options.client_alive_interval * 1000;
}
if (compat20) {
#if 0
/* wrong: bad condition XXX */
if (channel_not_very_much_buffered_data())
#endif
FD_SET(connection_in, *readsetp);
} else {
/*
* Read packets from the client unless we have too much
* buffered stdin or channel data.
*/
if (buffer_len(&stdin_buffer) < buffer_high &&
channel_not_very_much_buffered_data())
FD_SET(connection_in, *readsetp);
/*
* If there is not too much data already buffered going to
* the client, try to get some more data from the program.
*/
if (packet_not_very_much_data_to_write()) {
program_alive_scheduled = child_terminated;
if (!fdout_eof)
FD_SET(fdout, *readsetp);
if (!fderr_eof)
FD_SET(fderr, *readsetp);
}
/*
* If we have buffered data, try to write some of that data
* to the program.
*/
if (fdin != -1 && buffer_len(&stdin_buffer) > 0)
FD_SET(fdin, *writesetp);
}
notify_prepare(*readsetp);
/*
* If we have buffered packet data going to the client, mark that
* descriptor.
*/
if (packet_have_data_to_write())
FD_SET(connection_out, *writesetp);
/*
* If child has terminated and there is enough buffer space to read
* from it, then read as much as is available and exit.
*/
if (child_terminated && packet_not_very_much_data_to_write())
if (max_time_milliseconds == 0 || client_alive_scheduled)
max_time_milliseconds = 100;
if (max_time_milliseconds == 0)
tvp = NULL;
else {
tv.tv_sec = max_time_milliseconds / 1000;
tv.tv_usec = 1000 * (max_time_milliseconds % 1000);
tvp = &tv;
}
/* Wait for something to happen, or the timeout to expire. */
ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);
if (ret == -1) {
memset(*readsetp, 0, *nallocp);
memset(*writesetp, 0, *nallocp);
if (errno != EINTR)
error("select: %.100s", strerror(errno));
} else {
if (ret == 0 && client_alive_scheduled)
client_alive_check();
if (!compat20 && program_alive_scheduled && fdin_is_tty) {
if (!fdout_eof)
FD_SET(fdout, *readsetp);
if (!fderr_eof)
FD_SET(fderr, *readsetp);
}
}
notify_done(*readsetp);
}
/*
* Performs the interactive session. This handles data transmission between
* the client and the program. Note that the notion of stdin, stdout, and
* stderr in this function is sort of reversed: this function writes to
* stdin (of the child program), and reads from stdout and stderr (of the
* child program).
*/
void
server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg)
{
fd_set *readset = NULL, *writeset = NULL;
int max_fd = 0;
u_int nalloc = 0;
int wait_status; /* Status returned by wait(). */
pid_t wait_pid; /* pid returned by wait(). */
int waiting_termination = 0; /* Have displayed waiting close message. */
u_int64_t max_time_milliseconds;
u_int previous_stdout_buffer_bytes;
u_int stdout_buffer_bytes;
int type;
debug("Entering interactive session.");
/* Initialize the SIGCHLD kludge. */
child_terminated = 0;
mysignal(SIGCHLD, sigchld_handler);
if (!use_privsep) {
signal(SIGTERM, sigterm_handler);
signal(SIGINT, sigterm_handler);
signal(SIGQUIT, sigterm_handler);
}
/* Initialize our global variables. */
fdin = fdin_arg;
fdout = fdout_arg;
fderr = fderr_arg;
/* nonblocking IO */
set_nonblock(fdin);
set_nonblock(fdout);
/* we don't have stderr for interactive terminal sessions, see below */
if (fderr != -1)
set_nonblock(fderr);
if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin))
fdin_is_tty = 1;
connection_in = packet_get_connection_in();
connection_out = packet_get_connection_out();
notify_setup();
previous_stdout_buffer_bytes = 0;
/* Set approximate I/O buffer size. */
if (packet_is_interactive())
buffer_high = 4096;
else
buffer_high = 64 * 1024;
#if 0
/* Initialize max_fd to the maximum of the known file descriptors. */
max_fd = MAX(connection_in, connection_out);
max_fd = MAX(max_fd, fdin);
max_fd = MAX(max_fd, fdout);
if (fderr != -1)
max_fd = MAX(max_fd, fderr);
#endif
/* Initialize Initialize buffers. */
buffer_init(&stdin_buffer);
buffer_init(&stdout_buffer);
buffer_init(&stderr_buffer);
/*
* If we have no separate fderr (which is the case when we have a pty
* - there we cannot make difference between data sent to stdout and
* stderr), indicate that we have seen an EOF from stderr. This way
* we don't need to check the descriptor everywhere.
*/
if (fderr == -1)
fderr_eof = 1;
server_init_dispatch();
/* Main loop of the server for the interactive session mode. */
for (;;) {
/* Process buffered packets from the client. */
process_buffered_input_packets();
/*
* If we have received eof, and there is no more pending
* input data, cause a real eof by closing fdin.
*/
if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) {
if (fdin != fdout)
close(fdin);
else
shutdown(fdin, SHUT_WR); /* We will no longer send. */
fdin = -1;
}
/* Make packets from buffered stderr data to send to the client. */
make_packets_from_stderr_data();
/*
* Make packets from buffered stdout data to send to the
* client. If there is very little to send, this arranges to
* not send them now, but to wait a short while to see if we
* are getting more data. This is necessary, as some systems
* wake up readers from a pty after each separate character.
*/
max_time_milliseconds = 0;
stdout_buffer_bytes = buffer_len(&stdout_buffer);
if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 &&
stdout_buffer_bytes != previous_stdout_buffer_bytes) {
/* try again after a while */
max_time_milliseconds = 10;
} else {
/* Send it now. */
make_packets_from_stdout_data();
}
previous_stdout_buffer_bytes = buffer_len(&stdout_buffer);
/* Send channel data to the client. */
if (packet_not_very_much_data_to_write())
channel_output_poll();
/*
* Bail out of the loop if the program has closed its output
* descriptors, and we have no more data to send to the
* client, and there is no pending buffered data.
*/
if (fdout_eof && fderr_eof && !packet_have_data_to_write() &&
buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) {
if (!channel_still_open())
break;
if (!waiting_termination) {
const char *s = "Waiting for forwarded connections to terminate... (press ~& to background)\r\n";
char *cp;
waiting_termination = 1;
buffer_append(&stderr_buffer, s, strlen(s));
/* Display list of open channels. */
cp = channel_open_message();
buffer_append(&stderr_buffer, cp, strlen(cp));
free(cp);
}
}
max_fd = MAX(connection_in, connection_out);
max_fd = MAX(max_fd, fdin);
max_fd = MAX(max_fd, fdout);
max_fd = MAX(max_fd, fderr);
max_fd = MAX(max_fd, notify_pipe[0]);
/* Sleep in select() until we can do something. */
wait_until_can_do_something(&readset, &writeset, &max_fd,
&nalloc, max_time_milliseconds);
if (received_sigterm) {
logit("Exiting on signal %d", (int)received_sigterm);
/* Clean up sessions, utmp, etc. */
cleanup_exit(255);
}
/* Process any channel events. */
channel_after_select(readset, writeset);
/* Process input from the client and from program stdout/stderr. */
process_input(readset);
/* Process output to the client and to program stdin. */
process_output(writeset);
}
free(readset);
free(writeset);
/* Cleanup and termination code. */
/* Wait until all output has been sent to the client. */
drain_output();
debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.",
stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes);
/* Free and clear the buffers. */
buffer_free(&stdin_buffer);
buffer_free(&stdout_buffer);
buffer_free(&stderr_buffer);
/* Close the file descriptors. */
if (fdout != -1)
close(fdout);
fdout = -1;
fdout_eof = 1;
if (fderr != -1)
close(fderr);
fderr = -1;
fderr_eof = 1;
if (fdin != -1)
close(fdin);
fdin = -1;
channel_free_all();
/* We no longer want our SIGCHLD handler to be called. */
mysignal(SIGCHLD, SIG_DFL);
while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0)
if (errno != EINTR)
packet_disconnect("wait: %.100s", strerror(errno));
if (wait_pid != pid)
error("Strange, wait returned pid %ld, expected %ld",
(long)wait_pid, (long)pid);
/* Check if it exited normally. */
if (WIFEXITED(wait_status)) {
/* Yes, normal exit. Get exit status and send it to the client. */
debug("Command exited with status %d.", WEXITSTATUS(wait_status));
packet_start(SSH_SMSG_EXITSTATUS);
packet_put_int(WEXITSTATUS(wait_status));
packet_send();
packet_write_wait();
/*
* Wait for exit confirmation. Note that there might be
* other packets coming before it; however, the program has
* already died so we just ignore them. The client is
* supposed to respond with the confirmation when it receives
* the exit status.
*/
do {
type = packet_read();
}
while (type != SSH_CMSG_EXIT_CONFIRMATION);
debug("Received exit confirmation.");
return;
}
/* Check if the program terminated due to a signal. */
if (WIFSIGNALED(wait_status))
packet_disconnect("Command terminated on signal %d.",
WTERMSIG(wait_status));
/* Some weird exit cause. Just exit. */
packet_disconnect("wait returned status %04x.", wait_status);
/* NOTREACHED */
}
static void
client_wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp,
int *maxfdp, int *nallocp, int rekeying)
{
struct timeval tv, *tvp;
int ret;
/* Add any selections by the channel mechanism. */
channel_prepare_select(readsetp, writesetp, maxfdp, nallocp, rekeying);
if (!compat20) {
/* Read from the connection, unless our buffers are full. */
if (buffer_len(&stdout_buffer) < buffer_high &&
buffer_len(&stderr_buffer) < buffer_high &&
channel_not_very_much_buffered_data())
FD_SET(connection_in, *readsetp);
/*
* Read from stdin, unless we have seen EOF or have very much
* buffered data to send to the server.
*/
if (!stdin_eof && packet_not_very_much_data_to_write())
FD_SET(fileno(stdin), *readsetp);
/* Select stdout/stderr if have data in buffer. */
if (buffer_len(&stdout_buffer) > 0)
FD_SET(fileno(stdout), *writesetp);
if (buffer_len(&stderr_buffer) > 0)
FD_SET(fileno(stderr), *writesetp);
} else {
/* channel_prepare_select could have closed the last channel */
if (session_closed && !channel_still_open() &&
!packet_have_data_to_write()) {
/* clear mask since we did not call select() */
memset(*readsetp, 0, *nallocp);
memset(*writesetp, 0, *nallocp);
return;
} else {
FD_SET(connection_in, *readsetp);
}
}
/* Select server connection if have data to write to the server. */
if (packet_have_data_to_write())
FD_SET(connection_out, *writesetp);
/*
* Wait for something to happen. This will suspend the process until
* some selected descriptor can be read, written, or has some other
* event pending.
*/
if (options.server_alive_interval == 0 || !compat20)
tvp = NULL;
else {
tv.tv_sec = options.server_alive_interval;
tv.tv_usec = 0;
tvp = &tv;
}
ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);
if (ret < 0) {
char buf[100];
/*
* We have to clear the select masks, because we return.
* We have to return, because the mainloop checks for the flags
* set by the signal handlers.
*/
memset(*readsetp, 0, *nallocp);
memset(*writesetp, 0, *nallocp);
if (errno == EINTR)
return;
/* Note: we might still have data in the buffers. */
snprintf(buf, sizeof buf, "select: %s\r\n", strerror(errno));
buffer_append(&stderr_buffer, buf, strlen(buf));
quit_pending = 1;
} else if (ret == 0)
server_alive_check();
}