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-rw-r--r--src/openvpn/fragment.c414
1 files changed, 414 insertions, 0 deletions
diff --git a/src/openvpn/fragment.c b/src/openvpn/fragment.c
new file mode 100644
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--- /dev/null
+++ b/src/openvpn/fragment.c
@@ -0,0 +1,414 @@
+/*
+ * OpenVPN -- An application to securely tunnel IP networks
+ * over a single 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
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#elif defined(_MSC_VER)
+#include "config-msvc.h"
+#endif
+
+#include "syshead.h"
+
+#ifdef ENABLE_FRAGMENT
+
+#include "misc.h"
+#include "fragment.h"
+#include "integer.h"
+#include "memdbg.h"
+
+#define FRAG_ERR(s) { errmsg = s; goto error; }
+
+static void
+fragment_list_buf_init (struct fragment_list *list, const struct frame *frame)
+{
+ int i;
+ for (i = 0; i < N_FRAG_BUF; ++i)
+ list->fragments[i].buf = alloc_buf (BUF_SIZE (frame));
+}
+
+static void
+fragment_list_buf_free (struct fragment_list *list)
+{
+ int i;
+ for (i = 0; i < N_FRAG_BUF; ++i)
+ free_buf (&list->fragments[i].buf);
+}
+
+/*
+ * Given a sequence ID number, get a fragment buffer. Use a sliding window,
+ * similar to packet_id code.
+ */
+static struct fragment *
+fragment_list_get_buf (struct fragment_list *list, int seq_id)
+{
+ int diff;
+ if (abs (diff = modulo_subtract (seq_id, list->seq_id, N_SEQ_ID)) >= N_FRAG_BUF)
+ {
+ int i;
+ for (i = 0; i < N_FRAG_BUF; ++i)
+ list->fragments[i].defined = false;
+ list->index = 0;
+ list->seq_id = seq_id;
+ diff = 0;
+ }
+ while (diff > 0)
+ {
+ list->fragments[list->index = modulo_add (list->index, 1, N_FRAG_BUF)].defined = false;
+ list->seq_id = modulo_add (list->seq_id, 1, N_SEQ_ID);
+ --diff;
+ }
+ return &list->fragments[modulo_add (list->index, diff, N_FRAG_BUF)];
+}
+
+struct fragment_master *
+fragment_init (struct frame *frame)
+{
+ struct fragment_master *ret;
+
+ /* code that initializes other parts of
+ fragment_master assume an initial CLEAR */
+ ALLOC_OBJ_CLEAR (ret, struct fragment_master);
+
+ /* add in the size of our contribution to the expanded frame size */
+ frame_add_to_extra_frame (frame, sizeof(fragment_header_type));
+
+ /*
+ * Outgoing sequence ID is randomized to reduce
+ * the probability of sequence number collisions
+ * when openvpn sessions are restarted. This is
+ * not done out of any need for security, as all
+ * fragmentation control information resides
+ * inside of the encrypted/authenticated envelope.
+ */
+ ret->outgoing_seq_id = (int)get_random() & (N_SEQ_ID - 1);
+
+ event_timeout_init (&ret->wakeup, FRAG_WAKEUP_INTERVAL, now);
+
+ return ret;
+}
+
+void
+fragment_free (struct fragment_master *f)
+{
+ fragment_list_buf_free (&f->incoming);
+ free_buf (&f->outgoing);
+ free_buf (&f->outgoing_return);
+ free (f);
+}
+
+void
+fragment_frame_init (struct fragment_master *f, const struct frame *frame)
+{
+ fragment_list_buf_init (&f->incoming, frame);
+ f->outgoing = alloc_buf (BUF_SIZE (frame));
+ f->outgoing_return = alloc_buf (BUF_SIZE (frame));
+}
+
+/*
+ * Accept an incoming datagram (which may be a fragment) from remote.
+ * If the datagram is whole (i.e not a fragment), pass through.
+ * If the datagram is a fragment, join with other fragments received so far.
+ * If a fragment fully completes the datagram, return the datagram.
+ */
+void
+fragment_incoming (struct fragment_master *f, struct buffer *buf,
+ const struct frame* frame)
+{
+ const char *errmsg = NULL;
+ fragment_header_type flags = 0;
+ int frag_type = 0;
+
+ if (buf->len > 0)
+ {
+ /* get flags from packet head */
+ if (!buf_read (buf, &flags, sizeof (flags)))
+ FRAG_ERR ("flags not found in packet");
+ flags = ntoh_fragment_header_type (flags);
+
+ /* get fragment type from flags */
+ frag_type = ((flags >> FRAG_TYPE_SHIFT) & FRAG_TYPE_MASK);
+
+#if 0
+ /*
+ * If you want to extract FRAG_EXTRA_MASK/FRAG_EXTRA_SHIFT bits,
+ * do it here.
+ */
+ if (frag_type == FRAG_WHOLE || frag_type == FRAG_YES_NOTLAST)
+ {
+ }
+#endif
+
+ /* handle the fragment type */
+ if (frag_type == FRAG_WHOLE)
+ {
+ dmsg (D_FRAG_DEBUG,
+ "FRAG_IN buf->len=%d type=FRAG_WHOLE flags="
+ fragment_header_format,
+ buf->len,
+ flags);
+
+ if (flags & (FRAG_SEQ_ID_MASK | FRAG_ID_MASK))
+ FRAG_ERR ("spurrious FRAG_WHOLE flags");
+ }
+ else if (frag_type == FRAG_YES_NOTLAST || frag_type == FRAG_YES_LAST)
+ {
+ const int seq_id = ((flags >> FRAG_SEQ_ID_SHIFT) & FRAG_SEQ_ID_MASK);
+ const int n = ((flags >> FRAG_ID_SHIFT) & FRAG_ID_MASK);
+ const int size = ((frag_type == FRAG_YES_LAST)
+ ? (int)(((flags >> FRAG_SIZE_SHIFT) & FRAG_SIZE_MASK) << FRAG_SIZE_ROUND_SHIFT)
+ : buf->len);
+
+ /* get the appropriate fragment buffer based on received seq_id */
+ struct fragment *frag = fragment_list_get_buf (&f->incoming, seq_id);
+
+ dmsg (D_FRAG_DEBUG,
+ "FRAG_IN len=%d type=%d seq_id=%d frag_id=%d size=%d flags="
+ fragment_header_format,
+ buf->len,
+ frag_type,
+ seq_id,
+ n,
+ size,
+ flags);
+
+ /* make sure that size is an even multiple of 1<<FRAG_SIZE_ROUND_SHIFT */
+ if (size & FRAG_SIZE_ROUND_MASK)
+ FRAG_ERR ("bad fragment size");
+
+ /* is this the first fragment for our sequence number? */
+ if (!frag->defined || (frag->defined && frag->max_frag_size != size))
+ {
+ frag->defined = true;
+ frag->max_frag_size = size;
+ frag->map = 0;
+ ASSERT (buf_init (&frag->buf, FRAME_HEADROOM_ADJ (frame, FRAME_HEADROOM_MARKER_FRAGMENT)));
+ }
+
+ /* copy the data to fragment buffer */
+ if (!buf_copy_range (&frag->buf, n * size, buf, 0, buf->len))
+ FRAG_ERR ("fragment buffer overflow");
+
+ /* set elements in bit array to reflect which fragments have been received */
+ frag->map |= (((frag_type == FRAG_YES_LAST) ? FRAG_MAP_MASK : 1) << n);
+
+ /* update timestamp on partially built datagram */
+ frag->timestamp = now;
+
+ /* received full datagram? */
+ if ((frag->map & FRAG_MAP_MASK) == FRAG_MAP_MASK)
+ {
+ frag->defined = false;
+ *buf = frag->buf;
+ }
+ else
+ {
+ buf->len = 0;
+ }
+ }
+ else if (frag_type == FRAG_TEST)
+ {
+ FRAG_ERR ("FRAG_TEST not implemented");
+ }
+ else
+ {
+ FRAG_ERR ("unknown fragment type");
+ }
+ }
+
+ return;
+
+ error:
+ if (errmsg)
+ msg (D_FRAG_ERRORS, "FRAG_IN error flags=" fragment_header_format ": %s", flags, errmsg);
+ buf->len = 0;
+ return;
+}
+
+/* pack fragment parms into a uint32_t and prepend to buffer */
+static void
+fragment_prepend_flags (struct buffer *buf,
+ int type,
+ int seq_id,
+ int frag_id,
+ int frag_size)
+{
+ fragment_header_type flags = ((type & FRAG_TYPE_MASK) << FRAG_TYPE_SHIFT)
+ | ((seq_id & FRAG_SEQ_ID_MASK) << FRAG_SEQ_ID_SHIFT)
+ | ((frag_id & FRAG_ID_MASK) << FRAG_ID_SHIFT);
+
+ if (type == FRAG_WHOLE || type == FRAG_YES_NOTLAST)
+ {
+ /*
+ * If you want to set FRAG_EXTRA_MASK/FRAG_EXTRA_SHIFT bits,
+ * do it here.
+ */
+ dmsg (D_FRAG_DEBUG,
+ "FRAG_OUT len=%d type=%d seq_id=%d frag_id=%d frag_size=%d flags="
+ fragment_header_format,
+ buf->len, type, seq_id, frag_id, frag_size, flags);
+ }
+ else
+ {
+ flags |= (((frag_size >> FRAG_SIZE_ROUND_SHIFT) & FRAG_SIZE_MASK) << FRAG_SIZE_SHIFT);
+
+ dmsg (D_FRAG_DEBUG,
+ "FRAG_OUT len=%d type=%d seq_id=%d frag_id=%d frag_size=%d flags="
+ fragment_header_format,
+ buf->len, type, seq_id, frag_id, frag_size, flags);
+ }
+
+ flags = hton_fragment_header_type (flags);
+ ASSERT (buf_write_prepend (buf, &flags, sizeof (flags)));
+}
+
+/*
+ * Without changing the number of fragments, return a possibly smaller
+ * max fragment size that will allow for the last fragment to be of
+ * similar size as previous fragments.
+ */
+static inline int
+optimal_fragment_size (int len, int max_frag_size)
+{
+ const int mfs_aligned = (max_frag_size & ~FRAG_SIZE_ROUND_MASK);
+ const int div = len / mfs_aligned;
+ const int mod = len % mfs_aligned;
+
+ if (div > 0 && mod > 0 && mod < mfs_aligned * 3 / 4)
+ return min_int (mfs_aligned, (max_frag_size - ((max_frag_size - mod) / (div + 1))
+ + FRAG_SIZE_ROUND_MASK) & ~FRAG_SIZE_ROUND_MASK);
+ else
+ return mfs_aligned;
+}
+
+/* process an outgoing datagram, possibly breaking it up into fragments */
+void
+fragment_outgoing (struct fragment_master *f, struct buffer *buf,
+ const struct frame* frame)
+{
+ const char *errmsg = NULL;
+ if (buf->len > 0)
+ {
+ /* The outgoing buffer should be empty so we can put new data in it */
+ if (f->outgoing.len)
+ msg (D_FRAG_ERRORS, "FRAG: outgoing buffer is not empty, len=[%d,%d]",
+ buf->len, f->outgoing.len);
+ if (buf->len > PAYLOAD_SIZE_DYNAMIC(frame)) /* should we fragment? */
+ {
+ /*
+ * Send the datagram as a series of 2 or more fragments.
+ */
+ f->outgoing_frag_size = optimal_fragment_size (buf->len, PAYLOAD_SIZE_DYNAMIC(frame));
+ if (buf->len > f->outgoing_frag_size * MAX_FRAGS)
+ FRAG_ERR ("too many fragments would be required to send datagram");
+ ASSERT (buf_init (&f->outgoing, FRAME_HEADROOM (frame)));
+ ASSERT (buf_copy (&f->outgoing, buf));
+ f->outgoing_seq_id = modulo_add (f->outgoing_seq_id, 1, N_SEQ_ID);
+ f->outgoing_frag_id = 0;
+ buf->len = 0;
+ ASSERT (fragment_ready_to_send (f, buf, frame));
+ }
+ else
+ {
+ /*
+ * Send the datagram whole.
+ */
+ fragment_prepend_flags (buf,
+ FRAG_WHOLE,
+ 0,
+ 0,
+ 0);
+ }
+ }
+ return;
+
+ error:
+ if (errmsg)
+ msg (D_FRAG_ERRORS, "FRAG_OUT error, len=%d frag_size=%d MAX_FRAGS=%d: %s",
+ buf->len, f->outgoing_frag_size, MAX_FRAGS, errmsg);
+ buf->len = 0;
+ return;
+}
+
+/* return true (and set buf) if we have an outgoing fragment which is ready to send */
+bool
+fragment_ready_to_send (struct fragment_master *f, struct buffer *buf,
+ const struct frame* frame)
+{
+ if (fragment_outgoing_defined (f))
+ {
+ /* get fragment size, and determine if it is the last fragment */
+ int size = f->outgoing_frag_size;
+ int last = false;
+ if (f->outgoing.len <= size)
+ {
+ size = f->outgoing.len;
+ last = true;
+ }
+
+ /* initialize return buffer */
+ *buf = f->outgoing_return;
+ ASSERT (buf_init (buf, FRAME_HEADROOM (frame)));
+ ASSERT (buf_copy_n (buf, &f->outgoing, size));
+
+ /* fragment flags differ based on whether or not we are sending the last fragment */
+ fragment_prepend_flags (buf,
+ last ? FRAG_YES_LAST : FRAG_YES_NOTLAST,
+ f->outgoing_seq_id,
+ f->outgoing_frag_id++,
+ f->outgoing_frag_size);
+
+ ASSERT (!last || !f->outgoing.len); /* outgoing buffer length should be zero after last fragment sent */
+
+ return true;
+ }
+ else
+ return false;
+}
+
+static void
+fragment_ttl_reap (struct fragment_master *f)
+{
+ int i;
+ for (i = 0; i < N_FRAG_BUF; ++i)
+ {
+ struct fragment *frag = &f->incoming.fragments[i];
+ if (frag->defined && frag->timestamp + FRAG_TTL_SEC <= now)
+ {
+ msg (D_FRAG_ERRORS, "FRAG TTL expired i=%d", i);
+ frag->defined = false;
+ }
+ }
+}
+
+/* called every FRAG_WAKEUP_INTERVAL seconds */
+void
+fragment_wakeup (struct fragment_master *f, struct frame *frame)
+{
+ /* delete fragments with expired TTLs */
+ fragment_ttl_reap (f);
+}
+
+#else
+static void dummy(void) {}
+#endif
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