path: root/lib/libssl/d1_pkt.c

/* $OpenBSD: d1_pkt.c,v 1.112 2021/09/04 14:31:54 jsing Exp $ */
/*
 * DTLS implementation written by Nagendra Modadugu
 * (nagendra@cs.stanford.edu) for the OpenSSL project 2005.
 */
/* ====================================================================
 * Copyright (c) 1998-2005 The OpenSSL Project.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. All advertising materials mentioning features or use of this
 *    software must display the following acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
 *
 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For written permission, please contact
 *    openssl-core@openssl.org.
 *
 * 5. Products derived from this software may not be called "OpenSSL"
 *    nor may "OpenSSL" appear in their names without prior written
 *    permission of the OpenSSL Project.
 *
 * 6. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
 *
 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 * ====================================================================
 *
 * This product includes cryptographic software written by Eric Young
 * (eay@cryptsoft.com).  This product includes software written by Tim
 * Hudson (tjh@cryptsoft.com).
 *
 */
/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
 * All rights reserved.
 *
 * This package is an SSL implementation written
 * by Eric Young (eay@cryptsoft.com).
 * The implementation was written so as to conform with Netscapes SSL.
 *
 * This library is free for commercial and non-commercial use as long as
 * the following conditions are aheared to.  The following conditions
 * apply to all code found in this distribution, be it the RC4, RSA,
 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
 * included with this distribution is covered by the same copyright terms
 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
 *
 * Copyright remains Eric Young's, and as such any Copyright notices in
 * the code are not to be removed.
 * If this package is used in a product, Eric Young should be given attribution
 * as the author of the parts of the library used.
 * This can be in the form of a textual message at program startup or
 * in documentation (online or textual) provided with the package.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    "This product includes cryptographic software written by
 *     Eric Young (eay@cryptsoft.com)"
 *    The word 'cryptographic' can be left out if the rouines from the library
 *    being used are not cryptographic related :-).
 * 4. If you include any Windows specific code (or a derivative thereof) from
 *    the apps directory (application code) you must include an acknowledgement:
 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
 *
 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * The licence and distribution terms for any publically available version or
 * derivative of this code cannot be changed.  i.e. this code cannot simply be
 * copied and put under another distribution licence
 * [including the GNU Public Licence.]
 */

#include <machine/endian.h>

#include <errno.h>
#include <stdio.h>

#include <openssl/buffer.h>
#include <openssl/evp.h>

#include "bytestring.h"
#include "dtls_locl.h"
#include "pqueue.h"
#include "ssl_locl.h"

/* mod 128 saturating subtract of two 64-bit values in big-endian order */
static int
satsub64be(const unsigned char *v1, const unsigned char *v2)
{
	int ret, sat, brw, i;

	if (sizeof(long) == 8)
		do {
			long l;

			if (BYTE_ORDER == LITTLE_ENDIAN)
				break;
			/* not reached on little-endians */
			/* following test is redundant, because input is
			 * always aligned, but I take no chances... */
			if (((size_t)v1 | (size_t)v2) & 0x7)
				break;

			l  = *((long *)v1);
			l -= *((long *)v2);
			if (l > 128)
				return 128;
			else if (l<-128)
				return -128;
			else
				return (int)l;
		} while (0);

	ret = (int)v1[7] - (int)v2[7];
	sat = 0;
	brw = ret >> 8;	/* brw is either 0 or -1 */
	if (ret & 0x80) {
		for (i = 6; i >= 0; i--) {
			brw += (int)v1[i]-(int)v2[i];
			sat |= ~brw;
			brw >>= 8;
		}
	} else {
		for (i = 6; i >= 0; i--) {
			brw += (int)v1[i]-(int)v2[i];
			sat |= brw;
			brw >>= 8;
		}
	}
	brw <<= 8;	/* brw is either 0 or -256 */

	if (sat & 0xff)
		return brw | 0x80;
	else
		return brw + (ret & 0xFF);
}

static int dtls1_record_replay_check(SSL *s, DTLS1_BITMAP *bitmap,
    const unsigned char *seq);
static void dtls1_record_bitmap_update(SSL *s, DTLS1_BITMAP *bitmap,
    const unsigned char *seq);
static DTLS1_BITMAP *dtls1_get_bitmap(SSL *s, SSL3_RECORD_INTERNAL *rr,
    unsigned int *is_next_epoch);
static int dtls1_buffer_record(SSL *s, record_pqueue *q,
    unsigned char *priority);
static int dtls1_process_record(SSL *s);

/* copy buffered record into SSL structure */
static int
dtls1_copy_record(SSL *s, DTLS1_RECORD_DATA_INTERNAL *rdata)
{
	ssl3_release_buffer(&S3I(s)->rbuf);

	s->internal->packet = rdata->packet;
	s->internal->packet_length = rdata->packet_length;
	memcpy(&(S3I(s)->rbuf), &(rdata->rbuf), sizeof(SSL3_BUFFER_INTERNAL));
	memcpy(&(S3I(s)->rrec), &(rdata->rrec), sizeof(SSL3_RECORD_INTERNAL));

	return (1);
}

static int
dtls1_buffer_record(SSL *s, record_pqueue *queue, unsigned char *priority)
{
	DTLS1_RECORD_DATA_INTERNAL *rdata;
	pitem *item;

	/* Limit the size of the queue to prevent DOS attacks */
	if (pqueue_size(queue->q) >= 100)
		return 0;

	rdata = malloc(sizeof(DTLS1_RECORD_DATA_INTERNAL));
	item = pitem_new(priority, rdata);
	if (rdata == NULL || item == NULL)
		goto init_err;

	rdata->packet = s->internal->packet;
	rdata->packet_length = s->internal->packet_length;
	memcpy(&(rdata->rbuf), &(S3I(s)->rbuf), sizeof(SSL3_BUFFER_INTERNAL));
	memcpy(&(rdata->rrec), &(S3I(s)->rrec), sizeof(SSL3_RECORD_INTERNAL));

	item->data = rdata;

	s->internal->packet = NULL;
	s->internal->packet_length = 0;
	memset(&(S3I(s)->rbuf), 0, sizeof(SSL3_BUFFER_INTERNAL));
	memset(&(S3I(s)->rrec), 0, sizeof(SSL3_RECORD_INTERNAL));

	if (!ssl3_setup_buffers(s))
		goto err;

	/* insert should not fail, since duplicates are dropped */
	if (pqueue_insert(queue->q, item) == NULL)
		goto err;

	return (1);

 err:
	ssl3_release_buffer(&rdata->rbuf);

 init_err:
	SSLerror(s, ERR_R_INTERNAL_ERROR);
	free(rdata);
	pitem_free(item);
	return (-1);
}


static int
dtls1_retrieve_buffered_record(SSL *s, record_pqueue *queue)
{
	pitem *item;

	item = pqueue_pop(queue->q);
	if (item) {
		dtls1_copy_record(s, item->data);

		free(item->data);
		pitem_free(item);

		return (1);
	}

	return (0);
}

static int
dtls1_process_buffered_record(SSL *s)
{
	/* Check if epoch is current. */
	if (D1I(s)->unprocessed_rcds.epoch !=
	    tls12_record_layer_read_epoch(s->internal->rl))
		return (0);

	/* Update epoch once all unprocessed records have been processed. */
	if (pqueue_peek(D1I(s)->unprocessed_rcds.q) == NULL) {
		D1I(s)->unprocessed_rcds.epoch =
		    tls12_record_layer_read_epoch(s->internal->rl) + 1;
		return (0);
	}

	/* Process one of the records. */
	if (!dtls1_retrieve_buffered_record(s, &D1I(s)->unprocessed_rcds))
		return (-1);
	if (!dtls1_process_record(s))
		return (-1);

	return (1);
}

static int
dtls1_process_record(SSL *s)
{
	SSL3_RECORD_INTERNAL *rr = &(S3I(s)->rrec);
	uint8_t alert_desc;
	uint8_t *out;
	size_t out_len;

	tls12_record_layer_set_version(s->internal->rl, s->version);

	if (!tls12_record_layer_open_record(s->internal->rl, s->internal->packet,
	    s->internal->packet_length, &out, &out_len)) {
		tls12_record_layer_alert(s->internal->rl, &alert_desc);

		if (alert_desc == 0)
			goto err;

		/*
		 * DTLS should silently discard invalid records, including those
		 * with a bad MAC, as per RFC 6347 section 4.1.2.1.
		 */
		if (alert_desc == SSL_AD_BAD_RECORD_MAC) {
			out_len = 0;
			goto done;
		}

		if (alert_desc == SSL_AD_RECORD_OVERFLOW)
			SSLerror(s, SSL_R_ENCRYPTED_LENGTH_TOO_LONG);

		goto fatal_err;
	}

 done:
	rr->data = out;
	rr->length = out_len;
	rr->off = 0;

	s->internal->packet_length = 0;

	return (1);

 fatal_err:
	ssl3_send_alert(s, SSL3_AL_FATAL, alert_desc);
 err:
	return (0);
}

/* Call this to get a new input record.
 * It will return <= 0 if more data is needed, normally due to an error
 * or non-blocking IO.
 * When it finishes, one packet has been decoded and can be found in
 * ssl->s3->internal->rrec.type    - is the type of record
 * ssl->s3->internal->rrec.data, 	 - data
 * ssl->s3->internal->rrec.length, - number of bytes
 */
/* used only by dtls1_read_bytes */
int
dtls1_get_record(SSL *s)
{
	SSL3_RECORD_INTERNAL *rr = &(S3I(s)->rrec);
	unsigned char *p = NULL;
	DTLS1_BITMAP *bitmap;
	unsigned int is_next_epoch;
	int ret, n;

	/* See if there are pending records that can now be processed. */
	if ((ret = dtls1_process_buffered_record(s)) != 0)
		return (ret);

	/* get something from the wire */
	if (0) {
 again:
		/* dump this record on all retries */
		rr->length = 0;
		s->internal->packet_length = 0;
	}

	/* check if we have the header */
	if ((s->internal->rstate != SSL_ST_READ_BODY) ||
	    (s->internal->packet_length < DTLS1_RT_HEADER_LENGTH)) {
		CBS header, seq_no;
		uint16_t epoch, len, ssl_version;
		uint8_t type;

		n = ssl3_packet_read(s, DTLS1_RT_HEADER_LENGTH);
		if (n <= 0)
			return (n);

		/* If this packet contained a partial record, dump it. */
		if (n != DTLS1_RT_HEADER_LENGTH)
			goto again;

		s->internal->rstate = SSL_ST_READ_BODY;

		CBS_init(&header, s->internal->packet, s->internal->packet_length);

		/* Pull apart the header into the DTLS1_RECORD */
		if (!CBS_get_u8(&header, &type))
			goto again;
		if (!CBS_get_u16(&header, &ssl_version))
			goto again;

		/* Sequence number is 64 bits, with top 2 bytes = epoch. */
		if (!CBS_get_bytes(&header, &seq_no, SSL3_SEQUENCE_SIZE))
			goto again;
		if (!CBS_get_u16(&seq_no, &epoch))
			goto again;
		if (!CBS_write_bytes(&seq_no, &rr->seq_num[2],
		    sizeof(rr->seq_num) - 2, NULL))
			goto again;

		if (!CBS_get_u16(&header, &len))
			goto again;

		rr->type = type;
		rr->epoch = epoch;
		rr->length = len;

		/* unexpected version, silently discard */
		if (!s->internal->first_packet && ssl_version != s->version)
			goto again;

		/* wrong version, silently discard record */
		if ((ssl_version & 0xff00) != (s->version & 0xff00))
			goto again;

		/* record too long, silently discard it */
		if (rr->length > SSL3_RT_MAX_ENCRYPTED_LENGTH)
			goto again;

		/* now s->internal->rstate == SSL_ST_READ_BODY */
		p = (unsigned char *)CBS_data(&header);
	}

	/* s->internal->rstate == SSL_ST_READ_BODY, get and decode the data */

	n = ssl3_packet_extend(s, DTLS1_RT_HEADER_LENGTH + rr->length);
	if (n <= 0)
		return (n);

	/* If this packet contained a partial record, dump it. */
	if (n != DTLS1_RT_HEADER_LENGTH + rr->length)
		goto again;

	s->internal->rstate = SSL_ST_READ_HEADER; /* set state for later operations */

	/* match epochs.  NULL means the packet is dropped on the floor */
	bitmap = dtls1_get_bitmap(s, rr, &is_next_epoch);
	if (bitmap == NULL)
		goto again;

	/*
	 * Check whether this is a repeat, or aged record.
	 * Don't check if we're listening and this message is
	 * a ClientHello. They can look as if they're replayed,
	 * since they arrive from different connections and
	 * would be dropped unnecessarily.
	 */
	if (!(D1I(s)->listen && rr->type == SSL3_RT_HANDSHAKE &&
	    p != NULL && *p == SSL3_MT_CLIENT_HELLO) &&
	    !dtls1_record_replay_check(s, bitmap, rr->seq_num))
		goto again;

	/* just read a 0 length packet */
	if (rr->length == 0)
		goto again;

	/* If this record is from the next epoch (either HM or ALERT),
	 * and a handshake is currently in progress, buffer it since it
	 * cannot be processed at this time. However, do not buffer
	 * anything while listening.
	 */
	if (is_next_epoch) {
		if ((SSL_in_init(s) || s->internal->in_handshake) && !D1I(s)->listen) {
			if (dtls1_buffer_record(s, &(D1I(s)->unprocessed_rcds),
			    rr->seq_num) < 0)
				return (-1);
			/* Mark receipt of record. */
			dtls1_record_bitmap_update(s, bitmap, rr->seq_num);
		}
		goto again;
	}

	if (!dtls1_process_record(s))
		goto again;

	/* Mark receipt of record. */
	dtls1_record_bitmap_update(s, bitmap, rr->seq_num);

	return (1);
}

/* Return up to 'len' payload bytes received in 'type' records.
 * 'type' is one of the following:
 *
 *   -  SSL3_RT_HANDSHAKE (when ssl3_get_message calls us)
 *   -  SSL3_RT_APPLICATION_DATA (when ssl3_read calls us)
 *   -  0 (during a shutdown, no data has to be returned)
 *
 * If we don't have stored data to work from, read a SSL/TLS record first
 * (possibly multiple records if we still don't have anything to return).
 *
 * This function must handle any surprises the peer may have for us, such as
 * Alert records (e.g. close_notify), ChangeCipherSpec records (not really
 * a surprise, but handled as if it were), or renegotiation requests.
 * Also if record payloads contain fragments too small to process, we store
 * them until there is enough for the respective protocol (the record protocol
 * may use arbitrary fragmentation and even interleaving):
 *     Change cipher spec protocol
 *             just 1 byte needed, no need for keeping anything stored
 *     Alert protocol
 *             2 bytes needed (AlertLevel, AlertDescription)
 *     Handshake protocol
 *             4 bytes needed (HandshakeType, uint24 length) -- we just have
 *             to detect unexpected Client Hello and Hello Request messages
 *             here, anything else is handled by higher layers
 *     Application data protocol
 *             none of our business
 */
int
dtls1_read_bytes(SSL *s, int type, unsigned char *buf, int len, int peek)
{
	int al, i, ret;
	unsigned int n;
	SSL3_RECORD_INTERNAL *rr;

	if (S3I(s)->rbuf.buf == NULL) /* Not initialized yet */
		if (!ssl3_setup_buffers(s))
			return (-1);

	if ((type &&
	     type != SSL3_RT_APPLICATION_DATA && type != SSL3_RT_HANDSHAKE) ||
	    (peek && (type != SSL3_RT_APPLICATION_DATA))) {
		SSLerror(s, ERR_R_INTERNAL_ERROR);
		return -1;
	}

	if (!s->internal->in_handshake && SSL_in_init(s)) {
		i = s->internal->handshake_func(s);
		if (i < 0)
			return (i);
		if (i == 0) {
			SSLerror(s, SSL_R_SSL_HANDSHAKE_FAILURE);
			return (-1);
		}
	}

 start:
	s->internal->rwstate = SSL_NOTHING;

	/* S3I(s)->rrec.type	    - is the type of record
	 * S3I(s)->rrec.data,    - data
	 * S3I(s)->rrec.off,     - offset into 'data' for next read
	 * S3I(s)->rrec.length,  - number of bytes. */
	rr = &(S3I(s)->rrec);

	/* We are not handshaking and have no data yet,
	 * so process data buffered during the last handshake
	 * in advance, if any.
	 */
	if (S3I(s)->hs.state == SSL_ST_OK && rr->length == 0)
		dtls1_retrieve_buffered_record(s, &(D1I(s)->buffered_app_data));

	/* Check for timeout */
	if (dtls1_handle_timeout(s) > 0)
		goto start;

	/* get new packet if necessary */
	if ((rr->length == 0) || (s->internal->rstate == SSL_ST_READ_BODY)) {
		ret = dtls1_get_record(s);
		if (ret <= 0) {
			ret = dtls1_read_failed(s, ret);
			/* anything other than a timeout is an error */
			if (ret <= 0)
				return (ret);
			else
				goto start;
		}
	}

	if (D1I(s)->listen && rr->type != SSL3_RT_HANDSHAKE) {
		rr->length = 0;
		goto start;
	}

	/* we now have a packet which can be read and processed */

	if (S3I(s)->change_cipher_spec /* set when we receive ChangeCipherSpec,
	                               * reset by ssl3_get_finished */
	    && (rr->type != SSL3_RT_HANDSHAKE)) {
		/* We now have application data between CCS and Finished.
		 * Most likely the packets were reordered on their way, so
		 * buffer the application data for later processing rather
		 * than dropping the connection.
		 */
		if (dtls1_buffer_record(s, &(D1I(s)->buffered_app_data),
		    rr->seq_num) < 0) {
			SSLerror(s, ERR_R_INTERNAL_ERROR);
			return (-1);
		}
		rr->length = 0;
		goto start;
	}

	/* If the other end has shut down, throw anything we read away
	 * (even in 'peek' mode) */
	if (s->internal->shutdown & SSL_RECEIVED_SHUTDOWN) {
		rr->length = 0;
		s->internal->rwstate = SSL_NOTHING;
		return (0);
	}

	/* SSL3_RT_APPLICATION_DATA or SSL3_RT_HANDSHAKE */
	if (type == rr->type) {
		/* make sure that we are not getting application data when we
		 * are doing a handshake for the first time */
		if (SSL_in_init(s) && type == SSL3_RT_APPLICATION_DATA &&
		    !tls12_record_layer_read_protected(s->internal->rl)) {
			al = SSL_AD_UNEXPECTED_MESSAGE;
			SSLerror(s, SSL_R_APP_DATA_IN_HANDSHAKE);
			goto fatal_err;
		}

		if (len <= 0)
			return (len);

		if ((unsigned int)len > rr->length)
			n = rr->length;
		else
			n = (unsigned int)len;

		memcpy(buf, &(rr->data[rr->off]), n);
		if (!peek) {
			rr->length -= n;
			rr->off += n;
			if (rr->length == 0) {
				s->internal->rstate = SSL_ST_READ_HEADER;
				rr->off = 0;
			}
		}

		return (n);
	}

	/*
	 * If we get here, then type != rr->type; if we have a handshake
	 * message, then it was unexpected (Hello Request or Client Hello).
	 */

	{
		unsigned int record_min_len = 0;

		if (rr->type == SSL3_RT_HANDSHAKE) {
			record_min_len = DTLS1_HM_HEADER_LENGTH;
		} else if (rr->type == SSL3_RT_ALERT) {
			record_min_len = DTLS1_AL_HEADER_LENGTH;
		} else if (rr->type == SSL3_RT_CHANGE_CIPHER_SPEC) {
			record_min_len = DTLS1_CCS_HEADER_LENGTH;
		} else if (rr->type == SSL3_RT_APPLICATION_DATA) {
			/*
			 * Application data while renegotiating is allowed.
			 * Try reading again.
			 */
			BIO *bio;

			S3I(s)->in_read_app_data = 2;
			bio = SSL_get_rbio(s);
			s->internal->rwstate = SSL_READING;
			BIO_clear_retry_flags(bio);
			BIO_set_retry_read(bio);
			return (-1);
		} else {
			/* Not certain if this is the right error handling */
			al = SSL_AD_UNEXPECTED_MESSAGE;
			SSLerror(s, SSL_R_UNEXPECTED_RECORD);
			goto fatal_err;
		}

		if (record_min_len > 0 && rr->length < record_min_len) {
			s->internal->rstate = SSL_ST_READ_HEADER;
			rr->length = 0;
			goto start;
		}
	}

	/* If we are a client, check for an incoming 'Hello Request': */
	if (!s->server && rr->type == SSL3_RT_HANDSHAKE &&
	    rr->length >= DTLS1_HM_HEADER_LENGTH && rr->off == 0 &&
	    rr->data[0] == SSL3_MT_HELLO_REQUEST &&
	    s->session != NULL && s->session->cipher != NULL) {
		struct hm_header_st msg_hdr;
		CBS cbs;

		CBS_init(&cbs, rr->data, rr->length);
		if (!dtls1_get_message_header(&cbs, &msg_hdr))
			return -1;
		if (msg_hdr.msg_len != 0) {
			al = SSL_AD_DECODE_ERROR;
			SSLerror(s, SSL_R_BAD_HELLO_REQUEST);
			goto fatal_err;
		}
		rr->length = 0;

		/* no need to check sequence number on HELLO REQUEST messages */

		ssl_msg_callback(s, 0, SSL3_RT_HANDSHAKE, rr->data, 4);

		if (SSL_is_init_finished(s) &&
		    !(s->s3->flags & SSL3_FLAGS_NO_RENEGOTIATE_CIPHERS) &&
		    !S3I(s)->renegotiate) {
			D1I(s)->handshake_read_seq++;
			s->internal->new_session = 1;
			ssl3_renegotiate(s);
			if (ssl3_renegotiate_check(s)) {
				i = s->internal->handshake_func(s);
				if (i < 0)
					return (i);
				if (i == 0) {
					SSLerror(s, SSL_R_SSL_HANDSHAKE_FAILURE);
					return (-1);
				}

				if (!(s->internal->mode & SSL_MODE_AUTO_RETRY)) {
					if (S3I(s)->rbuf.left == 0) /* no read-ahead left? */
					{
						BIO *bio;
						/* In the case where we try to read application data,
						 * but we trigger an SSL handshake, we return -1 with
						 * the retry option set.  Otherwise renegotiation may
						 * cause nasty problems in the blocking world */
						s->internal->rwstate = SSL_READING;
						bio = SSL_get_rbio(s);
						BIO_clear_retry_flags(bio);
						BIO_set_retry_read(bio);
						return (-1);
					}
				}
			}
		}
		/* we either finished a handshake or ignored the request,
		 * now try again to obtain the (application) data we were asked for */
		rr->length = 0;
		goto start;
	}

	if (rr->type == SSL3_RT_ALERT && rr->length >= DTLS1_AL_HEADER_LENGTH &&
	    rr->off == 0) {
		int alert_level = rr->data[0];
		int alert_descr = rr->data[1];

		ssl_msg_callback(s, 0, SSL3_RT_ALERT, rr->data, 2);

		ssl_info_callback(s, SSL_CB_READ_ALERT,
		    (alert_level << 8) | alert_descr);

		if (alert_level == SSL3_AL_WARNING) {
			S3I(s)->warn_alert = alert_descr;
			if (alert_descr == SSL_AD_CLOSE_NOTIFY) {
				s->internal->shutdown |= SSL_RECEIVED_SHUTDOWN;
				return (0);
			}
		} else if (alert_level == SSL3_AL_FATAL) {
			s->internal->rwstate = SSL_NOTHING;
			S3I(s)->fatal_alert = alert_descr;
			SSLerror(s, SSL_AD_REASON_OFFSET + alert_descr);
			ERR_asprintf_error_data("SSL alert number %d",
			    alert_descr);
			s->internal->shutdown|=SSL_RECEIVED_SHUTDOWN;
			SSL_CTX_remove_session(s->ctx, s->session);
			return (0);
		} else {
			al = SSL_AD_ILLEGAL_PARAMETER;
			SSLerror(s, SSL_R_UNKNOWN_ALERT_TYPE);
			goto fatal_err;
		}

		rr->length = 0;
		goto start;
	}

	if (s->internal->shutdown & SSL_SENT_SHUTDOWN) {
		s->internal->rwstate = SSL_NOTHING;
		rr->length = 0;
		return (0);
	}

	if (rr->type == SSL3_RT_CHANGE_CIPHER_SPEC) {
		/* 'Change Cipher Spec' is just a single byte, so we know
		 * exactly what the record payload has to look like */
		/* XDTLS: check that epoch is consistent */
		if ((rr->length != DTLS1_CCS_HEADER_LENGTH) ||
		    (rr->off != 0) || (rr->data[0] != SSL3_MT_CCS)) {
			al = SSL_AD_DECODE_ERROR;
			SSLerror(s, SSL_R_BAD_CHANGE_CIPHER_SPEC);
			goto fatal_err;
		}

		ssl_msg_callback(s, 0, SSL3_RT_CHANGE_CIPHER_SPEC, rr->data, 1);

		/* We can't process a CCS now, because previous handshake
		 * messages are still missing, so just drop it.
		 */
		if (!D1I(s)->change_cipher_spec_ok) {
			rr->length = 0;
			goto start;
		}

		D1I(s)->change_cipher_spec_ok = 0;

		S3I(s)->change_cipher_spec = 1;
		if (!ssl3_do_change_cipher_spec(s))
			goto err;

		rr->length = 0;
		goto start;
	}

	/* Unexpected handshake message (Client Hello, or protocol violation) */
	if (rr->type == SSL3_RT_HANDSHAKE &&
	    rr->length >= DTLS1_HM_HEADER_LENGTH && rr->off == 0 &&
	    !s->internal->in_handshake) {
		struct hm_header_st msg_hdr;
		CBS cbs;

		/* this may just be a stale retransmit */
		CBS_init(&cbs, rr->data, rr->length);
		if (!dtls1_get_message_header(&cbs, &msg_hdr))
			return -1;
		if (rr->epoch != tls12_record_layer_read_epoch(s->internal->rl)) {
			rr->length = 0;
			goto start;
		}

		/* If we are server, we may have a repeated FINISHED of the
		 * client here, then retransmit our CCS and FINISHED.
		 */
		if (msg_hdr.type == SSL3_MT_FINISHED) {
			if (dtls1_check_timeout_num(s) < 0)
				return -1;

			dtls1_retransmit_buffered_messages(s);
			rr->length = 0;
			goto start;
		}

		if (((S3I(s)->hs.state&SSL_ST_MASK) == SSL_ST_OK) &&
		    !(s->s3->flags & SSL3_FLAGS_NO_RENEGOTIATE_CIPHERS)) {
			S3I(s)->hs.state = s->server ? SSL_ST_ACCEPT : SSL_ST_CONNECT;
			s->internal->renegotiate = 1;
			s->internal->new_session = 1;
		}
		i = s->internal->handshake_func(s);
		if (i < 0)
			return (i);
		if (i == 0) {
			SSLerror(s, SSL_R_SSL_HANDSHAKE_FAILURE);
			return (-1);
		}

		if (!(s->internal->mode & SSL_MODE_AUTO_RETRY)) {
			if (S3I(s)->rbuf.left == 0) /* no read-ahead left? */
			{
				BIO *bio;
				/* In the case where we try to read application data,
				 * but we trigger an SSL handshake, we return -1 with
				 * the retry option set.  Otherwise renegotiation may
				 * cause nasty problems in the blocking world */
				s->internal->rwstate = SSL_READING;
				bio = SSL_get_rbio(s);
				BIO_clear_retry_flags(bio);
				BIO_set_retry_read(bio);
				return (-1);
			}
		}
		rr->length = 0;
		goto start;
	}

	switch (rr->type) {
	default:
		al = SSL_AD_UNEXPECTED_MESSAGE;
		SSLerror(s, SSL_R_UNEXPECTED_RECORD);
		goto fatal_err;
	case SSL3_RT_CHANGE_CIPHER_SPEC:
	case SSL3_RT_ALERT:
	case SSL3_RT_HANDSHAKE:
		/* we already handled all of these, with the possible exception
		 * of SSL3_RT_HANDSHAKE when s->internal->in_handshake is set, but that
		 * should not happen when type != rr->type */
		al = SSL_AD_UNEXPECTED_MESSAGE;
		SSLerror(s, ERR_R_INTERNAL_ERROR);
		goto fatal_err;
	case SSL3_RT_APPLICATION_DATA:
		/* At this point, we were expecting handshake data,
		 * but have application data.  If the library was
		 * running inside ssl3_read() (i.e. in_read_app_data
		 * is set) and it makes sense to read application data
		 * at this point (session renegotiation not yet started),
		 * we will indulge it.
		 */
		if (S3I(s)->in_read_app_data &&
		    (S3I(s)->total_renegotiations != 0) &&
		    (((S3I(s)->hs.state & SSL_ST_CONNECT) &&
		    (S3I(s)->hs.state >= SSL3_ST_CW_CLNT_HELLO_A) &&
		    (S3I(s)->hs.state <= SSL3_ST_CR_SRVR_HELLO_A)) || (
		    (S3I(s)->hs.state & SSL_ST_ACCEPT) &&
		    (S3I(s)->hs.state <= SSL3_ST_SW_HELLO_REQ_A) &&
		    (S3I(s)->hs.state >= SSL3_ST_SR_CLNT_HELLO_A)))) {
			S3I(s)->in_read_app_data = 2;
			return (-1);
		} else {
			al = SSL_AD_UNEXPECTED_MESSAGE;
			SSLerror(s, SSL_R_UNEXPECTED_RECORD);
			goto fatal_err;
		}
	}
	/* not reached */

 fatal_err:
	ssl3_send_alert(s, SSL3_AL_FATAL, al);
 err:
	return (-1);
}

int
dtls1_write_app_data_bytes(SSL *s, int type, const void *buf_, int len)
{
	int i;

	if (SSL_in_init(s) && !s->internal->in_handshake)
	{
		i = s->internal->handshake_func(s);
		if (i < 0)
			return (i);
		if (i == 0) {
			SSLerror(s, SSL_R_SSL_HANDSHAKE_FAILURE);
			return -1;
		}
	}

	if (len > SSL3_RT_MAX_PLAIN_LENGTH) {
		SSLerror(s, SSL_R_DTLS_MESSAGE_TOO_BIG);
		return -1;
	}

	i = dtls1_write_bytes(s, type, buf_, len);
	return i;
}

/* Call this to write data in records of type 'type'
 * It will return <= 0 if not all data has been sent or non-blocking IO.
 */
int
dtls1_write_bytes(SSL *s, int type, const void *buf, int len)
{
	int i;

	OPENSSL_assert(len <= SSL3_RT_MAX_PLAIN_LENGTH);
	s->internal->rwstate = SSL_NOTHING;
	i = do_dtls1_write(s, type, buf, len);
	return i;
}

int
do_dtls1_write(SSL *s, int type, const unsigned char *buf, unsigned int len)
{
	SSL3_BUFFER_INTERNAL *wb = &(S3I(s)->wbuf);
	size_t out_len;
	CBB cbb;
	int ret;

	memset(&cbb, 0, sizeof(cbb));

	/*
	 * First check if there is a SSL3_BUFFER_INTERNAL still being written
	 * out.  This will happen with non blocking IO.
	 */
	if (wb->left != 0) {
		OPENSSL_assert(0); /* XDTLS:  want to see if we ever get here */
		return (ssl3_write_pending(s, type, buf, len));
	}

	/* If we have an alert to send, let's send it */
	if (S3I(s)->alert_dispatch) {
		if ((ret = ssl3_dispatch_alert(s)) <= 0)
			return (ret);
		/* If it went, fall through and send more stuff. */
	}

	if (len == 0)
		return 0;

	wb->offset = 0;

	if (!CBB_init_fixed(&cbb, wb->buf, wb->len))
		goto err;

	tls12_record_layer_set_version(s->internal->rl, s->version);

	if (!tls12_record_layer_seal_record(s->internal->rl, type, buf, len, &cbb))
		goto err;

	if (!CBB_finish(&cbb, NULL, &out_len))
		goto err;

	wb->left = out_len;

	/*
	 * Memorize arguments so that ssl3_write_pending can detect
	 * bad write retries later.
	 */
	S3I(s)->wpend_tot = len;
	S3I(s)->wpend_buf = buf;
	S3I(s)->wpend_type = type;
	S3I(s)->wpend_ret = len;

	/* We now just need to write the buffer. */
	return ssl3_write_pending(s, type, buf, len);

 err:
	CBB_cleanup(&cbb);

	return -1;
}

static int
dtls1_record_replay_check(SSL *s, DTLS1_BITMAP *bitmap,
    const unsigned char *seq)
{
	unsigned int shift;
	int cmp;

	cmp = satsub64be(seq, bitmap->max_seq_num);
	if (cmp > 0)
		return 1; /* this record in new */
	shift = -cmp;
	if (shift >= sizeof(bitmap->map)*8)
		return 0; /* stale, outside the window */
	else if (bitmap->map & (1UL << shift))
		return 0; /* record previously received */

	return 1;
}

static void
dtls1_record_bitmap_update(SSL *s, DTLS1_BITMAP *bitmap,
    const unsigned char *seq)
{
	unsigned int shift;
	int cmp;

	cmp = satsub64be(seq, bitmap->max_seq_num);
	if (cmp > 0) {
		shift = cmp;
		if (shift < sizeof(bitmap->map)*8)
			bitmap->map <<= shift, bitmap->map |= 1UL;
		else
			bitmap->map = 1UL;
		memcpy(bitmap->max_seq_num, seq, 8);
	} else {
		shift = -cmp;
		if (shift < sizeof(bitmap->map) * 8)
			bitmap->map |= 1UL << shift;
	}
}

static DTLS1_BITMAP *
dtls1_get_bitmap(SSL *s, SSL3_RECORD_INTERNAL *rr, unsigned int *is_next_epoch)
{
	uint16_t read_epoch, read_epoch_next;

	*is_next_epoch = 0;

	read_epoch = tls12_record_layer_read_epoch(s->internal->rl);
	read_epoch_next = read_epoch + 1;

	/* In current epoch, accept HM, CCS, DATA, & ALERT */
	if (rr->epoch == read_epoch)
		return &D1I(s)->bitmap;

	/* Only HM and ALERT messages can be from the next epoch */
	if (rr->epoch == read_epoch_next &&
	    (rr->type == SSL3_RT_HANDSHAKE || rr->type == SSL3_RT_ALERT)) {
		*is_next_epoch = 1;
		return &D1I(s)->next_bitmap;
	}

	return NULL;
}

void
dtls1_reset_read_seq_numbers(SSL *s)
{
	memcpy(&(D1I(s)->bitmap), &(D1I(s)->next_bitmap), sizeof(DTLS1_BITMAP));
	memset(&(D1I(s)->next_bitmap), 0, sizeof(DTLS1_BITMAP));
}