Imported Upstream version 2.2.1upstream/2.2.1

1 files changed, 486 insertions, 0 deletions

diff --git a/packet_id.c b/packet_id.c
new file mode 100644
index 0000000..b11e71f
--- /dev/null
+++ b/packet_id.c
@@ -0,0 +1,486 @@
+/*
+ *  OpenVPN -- An application to securely tunnel IP networks
+ *             over a single TCP/UDP port, with support for SSL/TLS-based
+ *             session authentication and key exchange,
+ *             packet encryption, packet authentication, and
+ *             packet compression.
+ *
+ *  Copyright (C) 2002-2010 OpenVPN Technologies, Inc. <sales@openvpn.net>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License version 2
+ *  as published by the Free Software Foundation.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program (see the file COPYING included with this
+ *  distribution); if not, write to the Free Software Foundation, Inc.,
+ *  59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+/*
+ * These routines are designed to catch replay attacks,
+ * where a man-in-the-middle captures packets and then
+ * attempts to replay them back later.
+ *
+ * We use the "sliding-window" algorithm, similar
+ * to IPSec.
+ */
+
+#include "syshead.h"
+
+#ifdef USE_CRYPTO
+
+#include "packet_id.h"
+#include "misc.h"
+#include "integer.h"
+
+#include "memdbg.h"
+
+/*
+ * Special time_t value that indicates that
+ * sequence number has expired.
+ */
+#define SEQ_UNSEEN  ((time_t)0)
+#define SEQ_EXPIRED ((time_t)1)
+
+void
+packet_id_init (struct packet_id *p, int seq_backtrack, int time_backtrack)
+{
+  dmsg (D_PID_DEBUG_LOW, "PID packet_id_init seq_backtrack=%d time_backtrack=%d",
+       seq_backtrack,
+       time_backtrack);
+
+  ASSERT (p);
+  CLEAR (*p);
+
+  if (seq_backtrack)
+    {
+      ASSERT (MIN_SEQ_BACKTRACK <= seq_backtrack && seq_backtrack <= MAX_SEQ_BACKTRACK);
+      ASSERT (MIN_TIME_BACKTRACK <= time_backtrack && time_backtrack <= MAX_TIME_BACKTRACK);
+      CIRC_LIST_ALLOC (p->rec.seq_list, struct seq_list, seq_backtrack);
+      p->rec.seq_backtrack = seq_backtrack;
+      p->rec.time_backtrack = time_backtrack;
+    }
+  p->rec.initialized = true;
+}
+
+void
+packet_id_free (struct packet_id *p)
+{
+  if (p)
+    {
+      dmsg (D_PID_DEBUG_LOW, "PID packet_id_free");
+      if (p->rec.seq_list)
+	free (p->rec.seq_list);
+      CLEAR (*p);
+    }
+}
+
+void
+packet_id_add (struct packet_id_rec *p, const struct packet_id_net *pin)
+{
+  const time_t local_now = now;
+  if (p->seq_list)
+    {
+      packet_id_type diff;
+
+      /*
+       * If time value increases, start a new
+       * sequence number sequence.
+       */
+      if (!CIRC_LIST_SIZE (p->seq_list)
+	  || pin->time > p->time
+	  || (pin->id >= (packet_id_type)p->seq_backtrack
+	      && pin->id - (packet_id_type)p->seq_backtrack > p->id))
+	{
+	  p->time = pin->time;
+	  p->id = 0;
+	  if (pin->id > (packet_id_type)p->seq_backtrack)
+	    p->id = pin->id - (packet_id_type)p->seq_backtrack;
+	  CIRC_LIST_RESET (p->seq_list);
+	}
+
+      while (p->id < pin->id)
+	{
+	  CIRC_LIST_PUSH (p->seq_list, SEQ_UNSEEN);
+	  ++p->id;
+	}
+
+      diff = p->id - pin->id;
+      if (diff < (packet_id_type) CIRC_LIST_SIZE (p->seq_list)
+	  && local_now > SEQ_EXPIRED)
+	CIRC_LIST_ITEM (p->seq_list, diff) = local_now;
+    }
+  else
+    {
+      p->time = pin->time;
+      p->id = pin->id;
+    }
+}
+
+/*
+ * Expire sequence numbers which can no longer
+ * be accepted because they would violate
+ * time_backtrack.
+ */
+void
+packet_id_reap (struct packet_id_rec *p)
+{
+  const time_t local_now = now;
+  if (p->time_backtrack)
+    {
+      int i;
+      bool expire = false;
+      for (i = 0; i < CIRC_LIST_SIZE (p->seq_list); ++i)
+	{
+	  const time_t t = CIRC_LIST_ITEM (p->seq_list, i);
+	  if (t == SEQ_EXPIRED)
+	    break;
+	  if (!expire && t && t + p->time_backtrack < local_now)
+	    expire = true;
+	  if (expire)
+	    CIRC_LIST_ITEM (p->seq_list, i) = SEQ_EXPIRED;
+	}
+    }
+  p->last_reap = local_now;
+}
+
+/*
+ * Return true if packet id is ok, or false if
+ * it is a replay.
+ */
+bool
+packet_id_test (const struct packet_id_rec *p,
+		const struct packet_id_net *pin)
+{
+  static int max_backtrack_stat;
+  packet_id_type diff;
+
+  dmsg (D_PID_DEBUG,
+       "PID TEST " time_format ":" packet_id_format " " time_format ":" packet_id_format "",
+       (time_type)p->time, (packet_id_print_type)p->id, (time_type)pin->time,
+       (packet_id_print_type)pin->id);
+
+  ASSERT (p->initialized);
+
+  if (!pin->id)
+    return false;
+
+  if (p->seq_backtrack)
+    {
+      /*
+       * In backtrack mode, we allow packet reordering subject
+       * to the seq_backtrack and time_backtrack constraints.
+       *
+       * This mode is used with UDP.
+       */
+      if (pin->time == p->time)
+	{
+	  /* is packet-id greater than any one we've seen yet? */
+	  if (pin->id > p->id)
+	    return true;
+
+	  /* check packet-id sliding window for original/replay status */
+	  diff = p->id - pin->id;
+
+	  /* keep track of maximum backtrack seen for debugging purposes */
+	  if ((int)diff > max_backtrack_stat)
+	    {
+	      max_backtrack_stat = (int)diff;
+	      msg (D_BACKTRACK, "Replay-window backtrack occurred [%d]", max_backtrack_stat);
+	    }
+
+	  if (diff >= (packet_id_type) CIRC_LIST_SIZE (p->seq_list))
+	    return false;
+
+	  return CIRC_LIST_ITEM (p->seq_list, diff) == 0;
+	}
+      else if (pin->time < p->time) /* if time goes back, reject */
+	return false;
+      else                          /* time moved forward */
+	return true;
+    }
+  else
+    {
+      /*
+       * In non-backtrack mode, all sequence number series must
+       * begin at some number n > 0 and must increment linearly without gaps.
+       *
+       * This mode is used with TCP.
+       */
+      if (pin->time == p->time)
+	return !p->id || pin->id == p->id + 1;
+      else if (pin->time < p->time) /* if time goes back, reject */
+	return false;
+      else                          /* time moved forward */
+	return pin->id == 1;
+    }
+}
+
+/*
+ * Read/write a packet ID to/from the buffer.  Short form is sequence number
+ * only.  Long form is sequence number and timestamp.
+ */
+
+bool
+packet_id_read (struct packet_id_net *pin, struct buffer *buf, bool long_form)
+{
+  packet_id_type net_id;
+  net_time_t net_time;
+
+  pin->id = 0;
+  pin->time = 0;
+
+  if (!buf_read (buf, &net_id, sizeof (net_id)))
+    return false;
+  pin->id = ntohpid (net_id);
+  if (long_form)
+    {
+      if (!buf_read (buf, &net_time, sizeof (net_time)))
+	return false;
+      pin->time = ntohtime (net_time);
+    }
+  return true;
+}
+
+bool
+packet_id_write (const struct packet_id_net *pin, struct buffer *buf, bool long_form, bool prepend)
+{
+  packet_id_type net_id = htonpid (pin->id);
+  net_time_t net_time = htontime (pin->time);
+
+  if (prepend)
+    {
+      if (long_form)
+	{
+	  if (!buf_write_prepend (buf, &net_time, sizeof (net_time)))
+	    return false;
+	}
+      if (!buf_write_prepend (buf, &net_id, sizeof (net_id)))
+	return false;
+    }
+  else
+    {
+      if (!buf_write (buf, &net_id, sizeof (net_id)))
+	return false;
+      if (long_form)
+	{
+	  if (!buf_write (buf, &net_time, sizeof (net_time)))
+	    return false;
+	}
+    }
+  return true;
+}
+
+const char *
+packet_id_net_print (const struct packet_id_net *pin, bool print_timestamp, struct gc_arena *gc)
+{
+  struct buffer out = alloc_buf_gc (256, gc);
+
+  buf_printf (&out, "[ #" packet_id_format, (packet_id_print_type)pin->id);
+  if (print_timestamp && pin->time)
+      buf_printf (&out, " / time = (" packet_id_format ") %s", 
+		  (packet_id_print_type)pin->time,
+		  time_string (pin->time, 0, false, gc));
+
+  buf_printf (&out, " ]");
+  return BSTR (&out);
+}
+
+/* initialize the packet_id_persist structure in a disabled state */
+void
+packet_id_persist_init (struct packet_id_persist *p)
+{
+  p->filename = NULL;
+  p->fd = -1;
+  p->time = p->time_last_written = 0;
+  p->id = p->id_last_written = 0;
+}
+
+/* close the file descriptor if it is open, and switch to disabled state */
+void
+packet_id_persist_close (struct packet_id_persist *p)
+{
+  if (packet_id_persist_enabled (p))
+    {
+      if (close (p->fd))
+	msg (D_PID_PERSIST | M_ERRNO, "Close error on --replay-persist file %s", p->filename);
+      packet_id_persist_init (p);
+    }
+}
+
+/* load persisted rec packet_id (time and id) only once from file, and set state to enabled */
+void
+packet_id_persist_load (struct packet_id_persist *p, const char *filename)
+{
+  struct gc_arena gc = gc_new ();
+  if (!packet_id_persist_enabled (p))
+    {
+      /* open packet-id persist file for both read and write */
+      p->fd = open (filename,
+		    O_CREAT | O_RDWR | O_BINARY,
+		    S_IRUSR | S_IWUSR);
+      if (p->fd == -1)
+	{
+	  msg (D_PID_PERSIST | M_ERRNO,
+	       "Cannot open --replay-persist file %s for read/write",
+	       filename);
+	}
+      else
+	{
+	  struct packet_id_persist_file_image image;
+	  ssize_t n;
+
+#if defined(HAVE_FLOCK) && defined(LOCK_EX) && defined(LOCK_NB)
+	  if (flock (p->fd, LOCK_EX | LOCK_NB))
+	    msg (M_ERR, "Cannot obtain exclusive lock on --replay-persist file %s", filename);
+#endif
+
+	  p->filename = filename;
+	  n = read (p->fd, &image, sizeof(image));
+	  if (n == sizeof(image))
+	    {
+	      p->time = p->time_last_written = image.time;
+	      p->id = p->id_last_written = image.id;
+	      dmsg (D_PID_PERSIST_DEBUG, "PID Persist Read from %s: %s",
+		   p->filename, packet_id_persist_print (p, &gc));
+	    }
+	  else if (n == -1)
+	    {
+	      msg (D_PID_PERSIST | M_ERRNO,
+		   "Read error on --replay-persist file %s",
+		   p->filename);
+	    }
+	}
+    }
+  gc_free (&gc);
+}
+
+/* save persisted rec packet_id (time and id) to file (only if enabled state) */
+void
+packet_id_persist_save (struct packet_id_persist *p)
+{
+  if (packet_id_persist_enabled (p) && p->time && (p->time != p->time_last_written ||
+						   p->id != p->id_last_written))
+    {
+      struct packet_id_persist_file_image image;
+      ssize_t n;
+      off_t seek_ret;
+      struct gc_arena gc = gc_new ();
+
+      image.time = p->time;
+      image.id = p->id;
+      seek_ret = lseek(p->fd, (off_t)0, SEEK_SET);
+      if (seek_ret == (off_t)0)
+	{
+	  n = write(p->fd, &image, sizeof(image));
+	  if (n == sizeof(image))
+	    {
+	      p->time_last_written = p->time;
+	      p->id_last_written = p->id;
+	      dmsg (D_PID_PERSIST_DEBUG, "PID Persist Write to %s: %s",
+		   p->filename, packet_id_persist_print (p, &gc));
+	    }
+	  else
+	    {
+	      msg (D_PID_PERSIST | M_ERRNO,
+		   "Cannot write to --replay-persist file %s",
+		   p->filename);
+	    }
+	}
+      else
+	{
+	  msg (D_PID_PERSIST | M_ERRNO,
+	       "Cannot seek to beginning of --replay-persist file %s",
+	       p->filename);
+	}
+      gc_free (&gc);
+    }
+}
+
+/* transfer packet_id_persist -> packet_id */
+void
+packet_id_persist_load_obj (const struct packet_id_persist *p, struct packet_id *pid)
+{
+  if (p && pid && packet_id_persist_enabled (p) && p->time)
+    {
+      pid->rec.time = p->time;
+      pid->rec.id = p->id;
+    }
+}
+
+const char *
+packet_id_persist_print (const struct packet_id_persist *p, struct gc_arena *gc)
+{
+  struct buffer out = alloc_buf_gc (256, gc);
+
+  buf_printf (&out, "[");
+
+  if (packet_id_persist_enabled (p))
+    {
+      buf_printf (&out, " #" packet_id_format, (packet_id_print_type)p->id);
+      if (p->time)
+	buf_printf (&out, " / time = (" packet_id_format ") %s",
+		    (packet_id_print_type)p->time,
+		    time_string (p->time, 0, false, gc));
+    }
+
+  buf_printf (&out, " ]");
+  return (char *)out.data;
+}
+
+#ifdef PID_TEST
+
+void
+packet_id_interactive_test ()
+{
+  struct packet_id pid;
+  struct packet_id_net pin;
+  bool long_form;
+  bool count = 0;
+  bool test;
+
+  const int seq_backtrack = 10;
+  const int time_backtrack = 10;
+
+  packet_id_init (&pid, seq_backtrack, time_backtrack);
+
+  while (true) {
+    char buf[80];
+    if (!fgets(buf, sizeof(buf), stdin))
+      break;
+    update_time ();
+    if (sscanf (buf, "%lu,%u", &pin.time, &pin.id) == 2)
+      {
+	packet_id_reap_test (&pid.rec);
+	test = packet_id_test (&pid.rec, &pin);
+	printf ("packet_id_test (" time_format ", " packet_id_format ") returned %d\n",
+		(time_type)pin.time,
+		(packet_id_print_type)pin.id,
+		test);
+	if (test)
+	  packet_id_add (&pid.rec, &pin);
+      }
+    else
+      {
+	long_form = (count < 20);
+	packet_id_alloc_outgoing (&pid.send, &pin, long_form);
+	printf ("(" time_format "(" packet_id_format "), %d)\n",
+		(time_type)pin.time,
+		(packet_id_print_type)pin.id,
+		long_form);
+	if (pid.send.id == 10)
+	  pid.send.id = 0xFFFFFFF8;
+	++count;
+      }
+  }
+  packet_id_free (&pid);
+}
+#endif
+
+#endif /* USE_CRYPTO */