Initial revision

1 files changed, 644 insertions, 0 deletions

diff --git a/serverloop.c b/serverloop.c
new file mode 100644
index 000000000..552c69c29
--- /dev/null
+++ b/serverloop.c
@@ -0,0 +1,644 @@
+/*
+
+serverloop.c
+
+Author: Tatu Ylonen <ylo@cs.hut.fi>
+
+Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
+                   All rights reserved
+
+Created: Sun Sep 10 00:30:37 1995 ylo
+
+Server main loop for handling the interactive session.
+
+*/
+
+#include "includes.h"
+#include "xmalloc.h"
+#include "ssh.h"
+#include "packet.h"
+#include "buffer.h"
+#include "servconf.h"
+#include "pty.h"
+
+static Buffer stdin_buffer;     /* Buffer for stdin data. */
+static Buffer stdout_buffer;    /* Buffer for stdout data. */
+static Buffer stderr_buffer;    /* Buffer for stderr data. */
+static int fdin;                /* Descriptor for stdin (for writing) */
+static int fdout;               /* Descriptor for stdout (for reading);
+                                   May be same number as fdin. */
+static int fderr;               /* Descriptor for stderr.  May be -1. */
+static long stdin_bytes = 0;    /* Number of bytes written to stdin. */
+static long stdout_bytes = 0;   /* Number of stdout bytes sent to client. */
+static long stderr_bytes = 0;   /* Number of stderr bytes sent to client. */
+static long fdout_bytes = 0;    /* Number of stdout bytes read from program. */
+static int stdin_eof = 0;       /* EOF message received from client. */
+static int fdout_eof = 0;       /* EOF encountered reading from fdout. */
+static int fderr_eof = 0;       /* EOF encountered readung from fderr. */
+static int connection_in;       /* Connection to client (input). */
+static int connection_out;      /* Connection to client (output). */
+static unsigned int buffer_high;/* "Soft" max buffer size. */
+static int max_fd;              /* Max file descriptor number for select(). */
+
+/* This SIGCHLD kludge is used to detect when the child exits.  The server
+   will exit after that, as soon as forwarded connections have terminated. */
+
+static int child_pid;                   /* Pid of the child. */
+static volatile int child_terminated;   /* The child has terminated. */
+static volatile int child_wait_status;  /* Status from wait(). */
+
+void sigchld_handler(int sig)
+{
+  int save_errno = errno;
+  int wait_pid;
+  debug("Received SIGCHLD.");
+  wait_pid = wait((int *)&child_wait_status);
+  if (wait_pid != -1)
+    {
+      if (wait_pid != child_pid)
+        error("Strange, got SIGCHLD and wait returned pid %d but child is %d",
+              wait_pid, child_pid);
+      if (WIFEXITED(child_wait_status) ||
+          WIFSIGNALED(child_wait_status))
+        child_terminated = 1;
+    }
+  signal(SIGCHLD, sigchld_handler);
+  errno = save_errno;
+}
+
+/* Process any buffered packets that have been received from the client. */
+
+void process_buffered_input_packets()
+{
+  int type;
+  char *data;
+  unsigned int data_len;
+  int row, col, xpixel, ypixel;
+  int payload_len;
+
+  /* Process buffered packets from the client. */
+  while ((type = packet_read_poll(&payload_len)) != SSH_MSG_NONE)
+    {
+      switch (type)
+        {
+        case SSH_CMSG_STDIN_DATA:
+          /* Stdin data from the client.  Append it to the buffer. */
+          if (fdin == -1)
+            break; /* Ignore any data if the client has closed stdin. */
+          data = packet_get_string(&data_len);
+          packet_integrity_check(payload_len, (4 + data_len), type);
+          buffer_append(&stdin_buffer, data, data_len);
+          memset(data, 0, data_len);
+          xfree(data);
+          break;
+          
+        case SSH_CMSG_EOF:
+          /* Eof from the client.  The stdin descriptor to the program
+             will be closed when all buffered data has drained. */
+          debug("EOF received for stdin.");
+          packet_integrity_check(payload_len, 0, type);
+          stdin_eof = 1;
+          break;
+
+        case SSH_CMSG_WINDOW_SIZE:
+          debug("Window change received.");
+          packet_integrity_check(payload_len, 4*4, type);
+          row = packet_get_int();
+          col = packet_get_int();
+          xpixel = packet_get_int();
+          ypixel = packet_get_int();
+          if (fdin != -1)
+            pty_change_window_size(fdin, row, col, xpixel, ypixel);
+          break;
+          
+        case SSH_MSG_PORT_OPEN:
+          debug("Received port open request.");
+          channel_input_port_open(payload_len);
+          break;
+          
+        case SSH_MSG_CHANNEL_OPEN_CONFIRMATION:
+          debug("Received channel open confirmation.");
+          packet_integrity_check(payload_len, 4 + 4, type);
+          channel_input_open_confirmation();
+          break;
+
+        case SSH_MSG_CHANNEL_OPEN_FAILURE:
+          debug("Received channel open failure.");
+          packet_integrity_check(payload_len, 4, type);
+          channel_input_open_failure();
+          break;
+          
+        case SSH_MSG_CHANNEL_DATA:
+          channel_input_data(payload_len);
+          break;
+          
+        case SSH_MSG_CHANNEL_CLOSE:
+          debug("Received channel close.");
+          packet_integrity_check(payload_len, 4, type);
+          channel_input_close();
+          break;
+
+        case SSH_MSG_CHANNEL_CLOSE_CONFIRMATION:
+          debug("Received channel close confirmation.");
+          packet_integrity_check(payload_len, 4, type);
+          channel_input_close_confirmation();
+          break;
+
+        default:
+          /* In this phase, any unexpected messages cause a protocol
+             error.  This is to ease debugging; also, since no 
+             confirmations are sent messages, unprocessed unknown 
+             messages could cause strange problems.  Any compatible 
+             protocol extensions must be negotiated before entering the 
+             interactive session. */
+          packet_disconnect("Protocol error during session: type %d", 
+                            type);
+        }
+    }
+}
+
+/* Make packets from buffered stderr data, and buffer it for sending
+   to the client. */
+
+void make_packets_from_stderr_data()
+{
+  int len;
+
+  /* Send buffered stderr data to the client. */
+  while (buffer_len(&stderr_buffer) > 0 && 
+         packet_not_very_much_data_to_write())
+    {
+      len = buffer_len(&stderr_buffer);
+      if (packet_is_interactive())
+        {
+          if (len > 512)
+            len = 512;
+        }
+      else
+        {
+          if (len > 32768)
+            len = 32768;  /* Keep the packets at reasonable size. */
+        }
+      packet_start(SSH_SMSG_STDERR_DATA);
+      packet_put_string(buffer_ptr(&stderr_buffer), len);
+      packet_send();
+      buffer_consume(&stderr_buffer, len);
+      stderr_bytes += len;
+    }
+}
+
+/* Make packets from buffered stdout data, and buffer it for sending to the
+   client. */
+
+void make_packets_from_stdout_data()
+{
+  int len;
+
+  /* Send buffered stdout data to the client. */
+  while (buffer_len(&stdout_buffer) > 0 && 
+         packet_not_very_much_data_to_write())
+    {
+      len = buffer_len(&stdout_buffer);
+      if (packet_is_interactive())
+        {
+          if (len > 512)
+            len = 512;
+        }
+      else
+        {
+          if (len > 32768)
+            len = 32768;  /* Keep the packets at reasonable size. */
+        }
+      packet_start(SSH_SMSG_STDOUT_DATA);
+      packet_put_string(buffer_ptr(&stdout_buffer), len);
+      packet_send();
+      buffer_consume(&stdout_buffer, len);
+      stdout_bytes += len;
+    }
+}
+
+/* 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). */
+
+void wait_until_can_do_something(fd_set *readset, fd_set *writeset,
+                                 unsigned int max_time_milliseconds)
+{
+  struct timeval tv, *tvp;
+  int ret;
+
+  /* When select fails we restart from here. */
+retry_select:
+
+  /* Initialize select() masks. */
+  FD_ZERO(readset);
+  
+  /* Read packets from the client unless we have too much buffered stdin
+     or channel data. */
+  if (buffer_len(&stdin_buffer) < 4096 &&
+      channel_not_very_much_buffered_data())
+    FD_SET(connection_in, readset);
+  
+  /* 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())
+    {
+      if (!fdout_eof)
+        FD_SET(fdout, readset);
+      if (!fderr_eof)
+        FD_SET(fderr, readset);
+    }
+  
+  FD_ZERO(writeset);
+  
+  /* Set masks for channel descriptors. */
+  channel_prepare_select(readset, writeset);
+  
+  /* If we have buffered packet data going to the client, mark that
+     descriptor. */
+  if (packet_have_data_to_write())
+    FD_SET(connection_out, writeset);
+  
+  /* 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, writeset);
+  
+  /* Update the maximum descriptor number if appropriate. */
+  if (channel_max_fd() > max_fd)
+    max_fd = channel_max_fd();
+  
+  /* If child has terminated, read as much as is available and then exit. */
+  if (child_terminated)
+    if (max_time_milliseconds == 0)
+      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(max_fd + 1, readset, writeset, NULL, tvp);
+  
+  if (ret < 0)
+    {
+      if (errno != EINTR)
+        error("select: %.100s", strerror(errno));
+      else
+        goto retry_select;
+    }
+}
+
+/* Processes input from the client and the program.  Input data is stored
+   in buffers and processed later. */
+
+void process_input(fd_set *readset)
+{
+  int len;
+  char buf[16384];
+
+  /* Read and buffer any input data from the client. */
+  if (FD_ISSET(connection_in, readset))
+    {
+      len = read(connection_in, buf, sizeof(buf));
+      if (len == 0)
+        fatal("Connection closed by remote host.");
+
+      /* There is a kernel bug on Solaris that causes select to sometimes
+         wake up even though there is no data available. */
+      if (len < 0 && errno == EAGAIN)
+        len = 0;
+
+      if (len < 0)
+        fatal("Read error from remote host: %.100s", strerror(errno));
+
+      /* Buffer any received data. */
+      packet_process_incoming(buf, len);
+    }
+  
+  /* Read and buffer any available stdout data from the program. */
+  if (!fdout_eof && FD_ISSET(fdout, readset))
+    {
+      len = read(fdout, buf, sizeof(buf));
+      if (len <= 0)
+        fdout_eof = 1;
+      else
+        {
+          buffer_append(&stdout_buffer, buf, len);
+          fdout_bytes += len;
+        }
+    }
+  
+  /* Read and buffer any available stderr data from the program. */
+  if (!fderr_eof && FD_ISSET(fderr, readset))
+    {
+      len = read(fderr, buf, sizeof(buf));
+      if (len <= 0)
+        fderr_eof = 1;
+      else
+        buffer_append(&stderr_buffer, buf, len);
+    }
+}
+
+/* Sends data from internal buffers to client program stdin. */
+
+void process_output(fd_set *writeset)
+{
+  int len;
+
+  /* Write buffered data to program stdin. */
+  if (fdin != -1 && FD_ISSET(fdin, writeset))
+    {
+      len = write(fdin, buffer_ptr(&stdin_buffer),
+                  buffer_len(&stdin_buffer));
+      if (len <= 0)
+        {
+#ifdef USE_PIPES
+          close(fdin); 
+#else
+          if (fdout == -1)
+            close(fdin);
+          else
+            shutdown(fdin, SHUT_WR); /* We will no longer send. */
+#endif
+          fdin = -1;
+        }
+      else
+        {
+          /* Successful write.  Consume the data from the buffer. */
+          buffer_consume(&stdin_buffer, len);
+          /* Update the count of bytes written to the program. */
+          stdin_bytes += len;
+        }
+    }
+  
+  /* Send any buffered packet data to the client. */
+  if (FD_ISSET(connection_out, writeset))
+    packet_write_poll();
+}
+
+/* Wait until all buffered output has been sent to the client.
+   This is used when the program terminates. */
+
+void drain_output()
+{
+  /* Send any buffered stdout data to the client. */
+  if (buffer_len(&stdout_buffer) > 0)
+    {
+      packet_start(SSH_SMSG_STDOUT_DATA);
+      packet_put_string(buffer_ptr(&stdout_buffer), 
+                        buffer_len(&stdout_buffer));
+      packet_send();
+      /* Update the count of sent bytes. */
+      stdout_bytes += buffer_len(&stdout_buffer);
+    }
+  
+  /* Send any buffered stderr data to the client. */
+  if (buffer_len(&stderr_buffer) > 0)
+    {
+      packet_start(SSH_SMSG_STDERR_DATA);
+      packet_put_string(buffer_ptr(&stderr_buffer), 
+                        buffer_len(&stderr_buffer));
+      packet_send();
+      /* Update the count of sent bytes. */
+      stderr_bytes += buffer_len(&stderr_buffer);
+    }
+  
+  /* Wait until all buffered data has been written to the client. */
+  packet_write_wait();
+}
+
+/* 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(int pid, int fdin_arg, int fdout_arg, int fderr_arg)
+{
+  int wait_status, wait_pid;    /* Status and pid returned by wait(). */
+  int waiting_termination = 0;  /* Have displayed waiting close message. */
+  unsigned int max_time_milliseconds;
+  unsigned int previous_stdout_buffer_bytes;
+  unsigned int stdout_buffer_bytes;
+  int type;
+
+  debug("Entering interactive session.");
+
+  /* Initialize the SIGCHLD kludge. */
+  child_pid = pid;
+  child_terminated = 0;
+  signal(SIGCHLD, sigchld_handler);
+
+  /* Initialize our global variables. */
+  fdin = fdin_arg;
+  fdout = fdout_arg;
+  fderr = fderr_arg;
+  connection_in = packet_get_connection_in();
+  connection_out = packet_get_connection_out();
+  
+  previous_stdout_buffer_bytes = 0;
+
+  /* Set approximate I/O buffer size. */
+  if (packet_is_interactive())
+    buffer_high = 4096;
+  else
+    buffer_high = 64 * 1024;
+
+  /* Initialize max_fd to the maximum of the known file descriptors. */
+  max_fd = fdin;
+  if (fdout > max_fd)
+    max_fd = fdout;
+  if (fderr != -1 && fderr > max_fd)
+    max_fd = fderr;
+  if (connection_in > max_fd)
+    max_fd = connection_in;
+  if (connection_out > max_fd)
+    max_fd = connection_out;
+
+  /* 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;
+
+  /* Main loop of the server for the interactive session mode. */
+  for (;;)
+    {
+      fd_set readset, writeset;
+
+      /* 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)
+        {
+#ifdef USE_PIPES
+          close(fdin);
+#else
+          if (fdout == -1)
+            close(fdin);
+          else
+            shutdown(fdin, SHUT_WR); /* We will no longer send. */
+#endif
+          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)
+        max_time_milliseconds = 10; /* try again after a while */
+      else
+        make_packets_from_stdout_data(); /* Send it now. */
+      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())
+            goto quit;
+          if (!waiting_termination)
+            {
+              const char *s = 
+                "Waiting for forwarded connections to terminate...\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));
+              xfree(cp);
+            }
+        }
+
+      /* Sleep in select() until we can do something. */
+      wait_until_can_do_something(&readset, &writeset,
+                                  max_time_milliseconds);
+
+      /* 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);
+    }
+
+ quit:
+  /* 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;
+
+  /* Stop listening for channels; this removes unix domain sockets. */
+  channel_stop_listening();
+  
+  /* Wait for the child to exit.  Get its exit status. */
+  wait_pid = wait(&wait_status);
+  if (wait_pid < 0)
+    {
+      /* It is possible that the wait was handled by SIGCHLD handler.  This
+         may result in either: this call returning with EINTR, or: this
+         call returning ECHILD. */
+      if (child_terminated)
+        wait_status = child_wait_status;
+      else
+        packet_disconnect("wait: %.100s", strerror(errno));
+    }
+  else
+    {
+      /* Check if it matches the process we forked. */
+      if (wait_pid != pid)
+        error("Strange, wait returned pid %d, expected %d", wait_pid, pid);
+    }
+
+  /* We no longer want our SIGCHLD handler to be called. */
+  signal(SIGCHLD, SIG_DFL);
+
+  /* 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
+        {
+          int plen;
+          type = packet_read(&plen);
+        }
+      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*/
+}
+