[thirdparty/openssl.git] / ssl / d1_both.c

/* ssl/d1_both.c */
/* 
 * 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 <limits.h>
#include <string.h>
#include <stdio.h>
#include "ssl_locl.h"
#include <openssl/buffer.h>
#include <openssl/rand.h>
#include <openssl/objects.h>
#include <openssl/evp.h>
#include <openssl/x509.h>

#define RSMBLY_BITMASK_SIZE(msg_len) (((msg_len) + 7) / 8)

#define RSMBLY_BITMASK_MARK(bitmask, start, end) { \
                        if ((end) - (start) <= 8) { \
                                long ii; \
                                for (ii = (start); ii < (end); ii++) bitmask[((ii) >> 3)] |= (1 << ((ii) & 7)); \
                        } else { \
                                long ii; \
                                bitmask[((start) >> 3)] |= bitmask_start_values[((start) & 7)]; \
                                for (ii = (((start) >> 3) + 1); ii < ((((end) - 1)) >> 3); ii++) bitmask[ii] = 0xff; \
                                bitmask[(((end) - 1) >> 3)] |= bitmask_end_values[((end) & 7)]; \
                        } }

#define RSMBLY_BITMASK_IS_COMPLETE(bitmask, msg_len, is_complete) { \
                        long ii; \
                        OPENSSL_assert((msg_len) > 0); \
                        is_complete = 1; \
                        if (bitmask[(((msg_len) - 1) >> 3)] != bitmask_end_values[((msg_len) & 7)]) is_complete = 0; \
                        if (is_complete) for (ii = (((msg_len) - 1) >> 3) - 1; ii >= 0 ; ii--) \
                                if (bitmask[ii] != 0xff) { is_complete = 0; break; } }

#if 0
#define RSMBLY_BITMASK_PRINT(bitmask, msg_len) { \
                        long ii; \
                        printf("bitmask: "); for (ii = 0; ii < (msg_len); ii++) \
                        printf("%d ", (bitmask[ii >> 3] & (1 << (ii & 7))) >> (ii & 7)); \
                        printf("\n"); }
#endif

static unsigned char bitmask_start_values[] = {0xff, 0xfe, 0xfc, 0xf8, 0xf0, 0xe0, 0xc0, 0x80};
static unsigned char bitmask_end_values[]   = {0xff, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f};

/* XDTLS:  figure out the right values */
static const unsigned int g_probable_mtu[] = {1500 - 28, 512 - 28, 256 - 28};

static unsigned int dtls1_guess_mtu(unsigned int curr_mtu);
static void dtls1_fix_message_header(SSL *s, unsigned long frag_off, 
        unsigned long frag_len);
static unsigned char *dtls1_write_message_header(SSL *s,
        unsigned char *p);
static void dtls1_set_message_header_int(SSL *s, unsigned char mt,
        unsigned long len, unsigned short seq_num, unsigned long frag_off, 
        unsigned long frag_len);
static long dtls1_get_message_fragment(SSL *s, int st1, int stn, 
        long max, int *ok);

static hm_fragment *
dtls1_hm_fragment_new(unsigned long frag_len, int reassembly)
        {
        hm_fragment *frag = NULL;
        unsigned char *buf = NULL;
        unsigned char *bitmask = NULL;

        frag = (hm_fragment *)OPENSSL_malloc(sizeof(hm_fragment));
        if ( frag == NULL)
                return NULL;

        if (frag_len)
                {
                buf = (unsigned char *)OPENSSL_malloc(frag_len);
                if ( buf == NULL)
                        {
                        OPENSSL_free(frag);
                        return NULL;
                        }
                }

        /* zero length fragment gets zero frag->fragment */
        frag->fragment = buf;

        /* Initialize reassembly bitmask if necessary */
        if (reassembly)
                {
                bitmask = (unsigned char *)OPENSSL_malloc(RSMBLY_BITMASK_SIZE(frag_len));
                if (bitmask == NULL)
                        {
                        if (buf != NULL) OPENSSL_free(buf);
                        OPENSSL_free(frag);
                        return NULL;
                        }
                memset(bitmask, 0, RSMBLY_BITMASK_SIZE(frag_len));
                }

        frag->reassembly = bitmask;

        return frag;
        }

static void
dtls1_hm_fragment_free(hm_fragment *frag)
        {

        if (frag->msg_header.is_ccs)
                {
                EVP_CIPHER_CTX_free(frag->msg_header.saved_retransmit_state.enc_write_ctx);
                EVP_MD_CTX_destroy(frag->msg_header.saved_retransmit_state.write_hash);
                }
        if (frag->fragment) OPENSSL_free(frag->fragment);
        if (frag->reassembly) OPENSSL_free(frag->reassembly);
        OPENSSL_free(frag);
        }

/* send s->init_buf in records of type 'type' (SSL3_RT_HANDSHAKE or SSL3_RT_CHANGE_CIPHER_SPEC) */
int dtls1_do_write(SSL *s, int type)
        {
        int ret;
        int curr_mtu;
        unsigned int len, frag_off, mac_size, blocksize;

        /* AHA!  Figure out the MTU, and stick to the right size */
        if (s->d1->mtu < dtls1_min_mtu() && !(SSL_get_options(s) & SSL_OP_NO_QUERY_MTU))
                {
                s->d1->mtu = 
                        BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_QUERY_MTU, 0, NULL);

                /* I've seen the kernel return bogus numbers when it doesn't know
                 * (initial write), so just make sure we have a reasonable number */
                if (s->d1->mtu < dtls1_min_mtu())
                        {
                        s->d1->mtu = 0;
                        s->d1->mtu = dtls1_guess_mtu(s->d1->mtu);
                        BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SET_MTU, 
                                s->d1->mtu, NULL);
                        }
                }
#if 0 
        mtu = s->d1->mtu;

        fprintf(stderr, "using MTU = %d\n", mtu);

        mtu -= (DTLS1_HM_HEADER_LENGTH + DTLS1_RT_HEADER_LENGTH);

        curr_mtu = mtu - BIO_wpending(SSL_get_wbio(s));

        if ( curr_mtu > 0)
                mtu = curr_mtu;
        else if ( ( ret = BIO_flush(SSL_get_wbio(s))) <= 0)
                return ret;

        if ( BIO_wpending(SSL_get_wbio(s)) + s->init_num >= mtu)
                {
                ret = BIO_flush(SSL_get_wbio(s));
                if ( ret <= 0)
                        return ret;
                mtu = s->d1->mtu - (DTLS1_HM_HEADER_LENGTH + DTLS1_RT_HEADER_LENGTH);
                }
#endif

        OPENSSL_assert(s->d1->mtu >= dtls1_min_mtu());  /* should have something reasonable now */

        if ( s->init_off == 0  && type == SSL3_RT_HANDSHAKE)
                OPENSSL_assert(s->init_num == 
                        (int)s->d1->w_msg_hdr.msg_len + DTLS1_HM_HEADER_LENGTH);

        if (s->write_hash)
                {
                if (s->enc_write_ctx && EVP_CIPHER_CTX_mode(s->enc_write_ctx) == EVP_CIPH_GCM_MODE)
                        mac_size = 0;
                else
                        mac_size = EVP_MD_CTX_size(s->write_hash);
                }
        else
                mac_size = 0;

        if (s->enc_write_ctx && 
                (EVP_CIPHER_CTX_mode(s->enc_write_ctx) == EVP_CIPH_CBC_MODE))
                blocksize = 2 * EVP_CIPHER_block_size(s->enc_write_ctx->cipher);
        else
                blocksize = 0;

        frag_off = 0;
        while( s->init_num)
                {
                curr_mtu = s->d1->mtu - BIO_wpending(SSL_get_wbio(s)) - 
                        DTLS1_RT_HEADER_LENGTH - mac_size - blocksize;

                if ( curr_mtu <= DTLS1_HM_HEADER_LENGTH)
                        {
                        /* grr.. we could get an error if MTU picked was wrong */
                        ret = BIO_flush(SSL_get_wbio(s));
                        if ( ret <= 0)
                                return ret;
                        curr_mtu = s->d1->mtu - DTLS1_RT_HEADER_LENGTH -
                                mac_size - blocksize;
                        }

                if ( s->init_num > curr_mtu)
                        len = curr_mtu;
                else
                        len = s->init_num;


                /* XDTLS: this function is too long.  split out the CCS part */
                if ( type == SSL3_RT_HANDSHAKE)
                        {
                        if ( s->init_off != 0)
                                {
                                OPENSSL_assert(s->init_off > DTLS1_HM_HEADER_LENGTH);
                                s->init_off -= DTLS1_HM_HEADER_LENGTH;
                                s->init_num += DTLS1_HM_HEADER_LENGTH;

                                if ( s->init_num > curr_mtu)
                                        len = curr_mtu;
                                else
                                        len = s->init_num;
                                }

                        dtls1_fix_message_header(s, frag_off, 
                                len - DTLS1_HM_HEADER_LENGTH);

                        dtls1_write_message_header(s, (unsigned char *)&s->init_buf->data[s->init_off]);

                        OPENSSL_assert(len >= DTLS1_HM_HEADER_LENGTH);
                        }

                ret=dtls1_write_bytes(s,type,&s->init_buf->data[s->init_off],
                        len);
                if (ret < 0)
                        {
                        /* might need to update MTU here, but we don't know
                         * which previous packet caused the failure -- so can't
                         * really retransmit anything.  continue as if everything
                         * is fine and wait for an alert to handle the
                         * retransmit 
                         */
                        if ( BIO_ctrl(SSL_get_wbio(s),
                                BIO_CTRL_DGRAM_MTU_EXCEEDED, 0, NULL) > 0 )
                                s->d1->mtu = BIO_ctrl(SSL_get_wbio(s),
                                        BIO_CTRL_DGRAM_QUERY_MTU, 0, NULL);
                        else
                                return(-1);
                        }
                else
                        {

                        /* bad if this assert fails, only part of the handshake
                         * message got sent.  but why would this happen? */
                        OPENSSL_assert(len == (unsigned int)ret);

                        if (type == SSL3_RT_HANDSHAKE && ! s->d1->retransmitting)
                                {
                                /* should not be done for 'Hello Request's, but in that case
                                 * we'll ignore the result anyway */
                                unsigned char *p = (unsigned char *)&s->init_buf->data[s->init_off];
                                const struct hm_header_st *msg_hdr = &s->d1->w_msg_hdr;
                                int xlen;

                                if (frag_off == 0 && s->version != DTLS1_BAD_VER)
                                        {
                                        /* reconstruct message header is if it
                                         * is being sent in single fragment */
                                        *p++ = msg_hdr->type;
                                        l2n3(msg_hdr->msg_len,p);
                                        s2n (msg_hdr->seq,p);
                                        l2n3(0,p);
                                        l2n3(msg_hdr->msg_len,p);
                                        p  -= DTLS1_HM_HEADER_LENGTH;
                                        xlen = ret;
                                        }
                                else
                                        {
                                        p  += DTLS1_HM_HEADER_LENGTH;
                                        xlen = ret - DTLS1_HM_HEADER_LENGTH;
                                        }

                                ssl3_finish_mac(s, p, xlen);
                                }

                        if (ret == s->init_num)
                                {
                                if (s->msg_callback)
                                        s->msg_callback(1, s->version, type, s->init_buf->data, 
                                                (size_t)(s->init_off + s->init_num), s, 
                                                s->msg_callback_arg);

                                s->init_off = 0;  /* done writing this message */
                                s->init_num = 0;

                                return(1);
                                }
                        s->init_off+=ret;
                        s->init_num-=ret;
                        frag_off += (ret -= DTLS1_HM_HEADER_LENGTH);
                        }
                }
        return(0);
        }


/* Obtain handshake message of message type 'mt' (any if mt == -1),
 * maximum acceptable body length 'max'.
 * Read an entire handshake message.  Handshake messages arrive in
 * fragments.
 */
long dtls1_get_message(SSL *s, int st1, int stn, int mt, long max, int *ok)
        {
        int i, al;
        struct hm_header_st *msg_hdr;
        unsigned char *p;
        unsigned long msg_len;

        /* s3->tmp is used to store messages that are unexpected, caused
         * by the absence of an optional handshake message */
        if (s->s3->tmp.reuse_message)
                {
                s->s3->tmp.reuse_message=0;
                if ((mt >= 0) && (s->s3->tmp.message_type != mt))
                        {
                        al=SSL_AD_UNEXPECTED_MESSAGE;
                        SSLerr(SSL_F_DTLS1_GET_MESSAGE,SSL_R_UNEXPECTED_MESSAGE);
                        goto f_err;
                        }
                *ok=1;
                s->init_msg = s->init_buf->data + DTLS1_HM_HEADER_LENGTH;
                s->init_num = (int)s->s3->tmp.message_size;
                return s->init_num;
                }

        msg_hdr = &s->d1->r_msg_hdr;
        memset(msg_hdr, 0x00, sizeof(struct hm_header_st));

again:
        i = dtls1_get_message_fragment(s, st1, stn, max, ok);
        if ( i == DTLS1_HM_BAD_FRAGMENT ||
                i == DTLS1_HM_FRAGMENT_RETRY)  /* bad fragment received */
                goto again;
        else if ( i <= 0 && !*ok)
                return i;

        p = (unsigned char *)s->init_buf->data;
        msg_len = msg_hdr->msg_len;

        /* reconstruct message header */
        *(p++) = msg_hdr->type;
        l2n3(msg_len,p);
        s2n (msg_hdr->seq,p);
        l2n3(0,p);
        l2n3(msg_len,p);
        if (s->version != DTLS1_BAD_VER) {
                p       -= DTLS1_HM_HEADER_LENGTH;
                msg_len += DTLS1_HM_HEADER_LENGTH;
        }

        ssl3_finish_mac(s, p, msg_len);
        if (s->msg_callback)
                s->msg_callback(0, s->version, SSL3_RT_HANDSHAKE,
                        p, msg_len,
                        s, s->msg_callback_arg);

        memset(msg_hdr, 0x00, sizeof(struct hm_header_st));

        /* Don't change sequence numbers while listening */
        if (!s->d1->listen)
                s->d1->handshake_read_seq++;

        s->init_msg = s->init_buf->data + DTLS1_HM_HEADER_LENGTH;
        return s->init_num;

f_err:
        ssl3_send_alert(s,SSL3_AL_FATAL,al);
        *ok = 0;
        return -1;
        }


static int dtls1_preprocess_fragment(SSL *s,struct hm_header_st *msg_hdr,int max)
        {
        size_t frag_off,frag_len,msg_len;

        msg_len  = msg_hdr->msg_len;
        frag_off = msg_hdr->frag_off;
        frag_len = msg_hdr->frag_len;

        /* sanity checking */
        if ( (frag_off+frag_len) > msg_len)
                {
                SSLerr(SSL_F_DTLS1_PREPROCESS_FRAGMENT,SSL_R_EXCESSIVE_MESSAGE_SIZE);
                return SSL_AD_ILLEGAL_PARAMETER;
                }

        if ( (frag_off+frag_len) > (unsigned long)max)
                {
                SSLerr(SSL_F_DTLS1_PREPROCESS_FRAGMENT,SSL_R_EXCESSIVE_MESSAGE_SIZE);
                return SSL_AD_ILLEGAL_PARAMETER;
                }

        if ( s->d1->r_msg_hdr.frag_off == 0) /* first fragment */
                {
                /* msg_len is limited to 2^24, but is effectively checked
                 * against max above */
                if (!BUF_MEM_grow_clean(s->init_buf,msg_len+DTLS1_HM_HEADER_LENGTH))
                        {
                        SSLerr(SSL_F_DTLS1_PREPROCESS_FRAGMENT,ERR_R_BUF_LIB);
                        return SSL_AD_INTERNAL_ERROR;
                        }

                s->s3->tmp.message_size  = msg_len;
                s->d1->r_msg_hdr.msg_len = msg_len;
                s->s3->tmp.message_type  = msg_hdr->type;
                s->d1->r_msg_hdr.type    = msg_hdr->type;
                s->d1->r_msg_hdr.seq     = msg_hdr->seq;
                }
        else if (msg_len != s->d1->r_msg_hdr.msg_len)
                {
                /* They must be playing with us! BTW, failure to enforce
                 * upper limit would open possibility for buffer overrun. */
                SSLerr(SSL_F_DTLS1_PREPROCESS_FRAGMENT,SSL_R_EXCESSIVE_MESSAGE_SIZE);
                return SSL_AD_ILLEGAL_PARAMETER;
                }

        return 0; /* no error */
        }


static int
dtls1_retrieve_buffered_fragment(SSL *s, long max, int *ok)
        {
        /* (0) check whether the desired fragment is available
         * if so:
         * (1) copy over the fragment to s->init_buf->data[]
         * (2) update s->init_num
         */
        pitem *item;
        hm_fragment *frag;
        int al;

        *ok = 0;
        item = pqueue_peek(s->d1->buffered_messages);
        if ( item == NULL)
                return 0;

        frag = (hm_fragment *)item->data;
        
        /* Don't return if reassembly still in progress */
        if (frag->reassembly != NULL)
                return 0;

        if ( s->d1->handshake_read_seq == frag->msg_header.seq)
                {
                unsigned long frag_len = frag->msg_header.frag_len;
                pqueue_pop(s->d1->buffered_messages);

                al=dtls1_preprocess_fragment(s,&frag->msg_header,max);

                if (al==0) /* no alert */
                        {
                        unsigned char *p = (unsigned char *)s->init_buf->data+DTLS1_HM_HEADER_LENGTH;
                        memcpy(&p[frag->msg_header.frag_off],
                                frag->fragment,frag->msg_header.frag_len);
                        }

                dtls1_hm_fragment_free(frag);
                pitem_free(item);

                if (al==0)
                        {
                        *ok = 1;
                        return frag_len;
                        }

                ssl3_send_alert(s,SSL3_AL_FATAL,al);
                s->init_num = 0;
                *ok = 0;
                return -1;
                }
        else
                return 0;
        }

/* dtls1_max_handshake_message_len returns the maximum number of bytes
 * permitted in a DTLS handshake message for |s|. The minimum is 16KB, but may
 * be greater if the maximum certificate list size requires it. */
static unsigned long dtls1_max_handshake_message_len(const SSL *s)
        {
        unsigned long max_len = DTLS1_HM_HEADER_LENGTH + SSL3_RT_MAX_ENCRYPTED_LENGTH;
        if (max_len < (unsigned long)s->max_cert_list)
                return s->max_cert_list;
        return max_len;
        }

static int
dtls1_reassemble_fragment(SSL *s, const struct hm_header_st* msg_hdr, int *ok)
        {
        hm_fragment *frag = NULL;
        pitem *item = NULL;
        int i = -1, is_complete;
        unsigned char seq64be[8];
        unsigned long frag_len = msg_hdr->frag_len;

        if ((msg_hdr->frag_off+frag_len) > msg_hdr->msg_len ||
            msg_hdr->msg_len > dtls1_max_handshake_message_len(s))
                goto err;

        if (frag_len == 0)
                return DTLS1_HM_FRAGMENT_RETRY;

        /* Try to find item in queue */
        memset(seq64be,0,sizeof(seq64be));
        seq64be[6] = (unsigned char) (msg_hdr->seq>>8);
        seq64be[7] = (unsigned char) msg_hdr->seq;
        item = pqueue_find(s->d1->buffered_messages, seq64be);

        if (item == NULL)
                {
                frag = dtls1_hm_fragment_new(msg_hdr->msg_len, 1);
                if ( frag == NULL)
                        goto err;
                memcpy(&(frag->msg_header), msg_hdr, sizeof(*msg_hdr));
                frag->msg_header.frag_len = frag->msg_header.msg_len;
                frag->msg_header.frag_off = 0;
                }
        else
                {
                frag = (hm_fragment*) item->data;
                if (frag->msg_header.msg_len != msg_hdr->msg_len)
                        {
                        item = NULL;
                        frag = NULL;
                        goto err;
                        }
                }


        /* If message is already reassembled, this must be a
         * retransmit and can be dropped. In this case item != NULL and so frag
         * does not need to be freed.
         */
        if (frag->reassembly == NULL)
                {
                unsigned char devnull [256];

                while (frag_len)
                        {
                        i = s->method->ssl_read_bytes(s,SSL3_RT_HANDSHAKE,
                                devnull,
                                frag_len>sizeof(devnull)?sizeof(devnull):frag_len,0);
                        if (i<=0) goto err;
                        frag_len -= i;
                        }
                return DTLS1_HM_FRAGMENT_RETRY;
                }

        /* read the body of the fragment (header has already been read */
        i = s->method->ssl_read_bytes(s,SSL3_RT_HANDSHAKE,
                frag->fragment + msg_hdr->frag_off,frag_len,0);
        if ((unsigned long)i!=frag_len)
                i=-1;
        if (i<=0)
                goto err;

        RSMBLY_BITMASK_MARK(frag->reassembly, (long)msg_hdr->frag_off,
                            (long)(msg_hdr->frag_off + frag_len));

        RSMBLY_BITMASK_IS_COMPLETE(frag->reassembly, (long)msg_hdr->msg_len,
                                   is_complete);

        if (is_complete)
                {
                OPENSSL_free(frag->reassembly);
                frag->reassembly = NULL;
                }

        if (item == NULL)
                {
                item = pitem_new(seq64be, frag);
                if (item == NULL)
                        {
                        i = -1;
                        goto err;
                        }

                item = pqueue_insert(s->d1->buffered_messages, item);
                /* pqueue_insert fails iff a duplicate item is inserted.
                 * However, |item| cannot be a duplicate. If it were,
                 * |pqueue_find|, above, would have returned it and control
                 * would never have reached this branch. */
                OPENSSL_assert(item != NULL);
                }

        return DTLS1_HM_FRAGMENT_RETRY;

err:
        if (frag != NULL && item == NULL) dtls1_hm_fragment_free(frag);
        *ok = 0;
        return i;
        }


static int
dtls1_process_out_of_seq_message(SSL *s, const struct hm_header_st* msg_hdr, int *ok)
{
        int i=-1;
        hm_fragment *frag = NULL;
        pitem *item = NULL;
        unsigned char seq64be[8];
        unsigned long frag_len = msg_hdr->frag_len;

        if ((msg_hdr->frag_off+frag_len) > msg_hdr->msg_len)
                goto err;

        /* Try to find item in queue, to prevent duplicate entries */
        memset(seq64be,0,sizeof(seq64be));
        seq64be[6] = (unsigned char) (msg_hdr->seq>>8);
        seq64be[7] = (unsigned char) msg_hdr->seq;
        item = pqueue_find(s->d1->buffered_messages, seq64be);

        /* If we already have an entry and this one is a fragment,
         * don't discard it and rather try to reassemble it.
         */
        if (item != NULL && frag_len != msg_hdr->msg_len)
                item = NULL;

        /* Discard the message if sequence number was already there, is
         * too far in the future, already in the queue or if we received
         * a FINISHED before the SERVER_HELLO, which then must be a stale
         * retransmit.
         */
        if (msg_hdr->seq <= s->d1->handshake_read_seq ||
                msg_hdr->seq > s->d1->handshake_read_seq + 10 || item != NULL ||
                (s->d1->handshake_read_seq == 0 && msg_hdr->type == SSL3_MT_FINISHED))
                {
                unsigned char devnull [256];

                while (frag_len)
                        {
                        i = s->method->ssl_read_bytes(s,SSL3_RT_HANDSHAKE,
                                devnull,
                                frag_len>sizeof(devnull)?sizeof(devnull):frag_len,0);
                        if (i<=0) goto err;
                        frag_len -= i;
                        }
                }
        else
                {
                if (frag_len != msg_hdr->msg_len)
                        return dtls1_reassemble_fragment(s, msg_hdr, ok);

                if (frag_len > dtls1_max_handshake_message_len(s))
                        goto err;

                frag = dtls1_hm_fragment_new(frag_len, 0);
                if ( frag == NULL)
                        goto err;

                memcpy(&(frag->msg_header), msg_hdr, sizeof(*msg_hdr));

                if (frag_len)
                        {
                        /* read the body of the fragment (header has already been read */
                        i = s->method->ssl_read_bytes(s,SSL3_RT_HANDSHAKE,
                                frag->fragment,frag_len,0);
                        if ((unsigned long)i!=frag_len)
                                i = -1;
                        if (i<=0)
                                goto err;
                        }

                item = pitem_new(seq64be, frag);
                if ( item == NULL)
                        goto err;

                item = pqueue_insert(s->d1->buffered_messages, item);
                /* pqueue_insert fails iff a duplicate item is inserted.
                 * However, |item| cannot be a duplicate. If it were,
                 * |pqueue_find|, above, would have returned it. Then, either
                 * |frag_len| != |msg_hdr->msg_len| in which case |item| is set
                 * to NULL and it will have been processed with
                 * |dtls1_reassemble_fragment|, above, or the record will have
                 * been discarded. */
                OPENSSL_assert(item != NULL);
                }

        return DTLS1_HM_FRAGMENT_RETRY;

err:
        if (frag != NULL && item == NULL) dtls1_hm_fragment_free(frag);
        *ok = 0;
        return i;
        }


static long
dtls1_get_message_fragment(SSL *s, int st1, int stn, long max, int *ok)
        {
        unsigned char wire[DTLS1_HM_HEADER_LENGTH];
        unsigned long len, frag_off, frag_len;
        int i,al;
        struct hm_header_st msg_hdr;

        redo:
        /* see if we have the required fragment already */
        if ((frag_len = dtls1_retrieve_buffered_fragment(s,max,ok)) || *ok)
                {
                if (*ok)        s->init_num = frag_len;
                return frag_len;
                }

        /* read handshake message header */
        i=s->method->ssl_read_bytes(s,SSL3_RT_HANDSHAKE,wire,
                DTLS1_HM_HEADER_LENGTH, 0);
        if (i <= 0)     /* nbio, or an error */
                {
                s->rwstate=SSL_READING;
                *ok = 0;
                return i;
                }
        /* Handshake fails if message header is incomplete */
        if (i != DTLS1_HM_HEADER_LENGTH)
                {
                al=SSL_AD_UNEXPECTED_MESSAGE;
                SSLerr(SSL_F_DTLS1_GET_MESSAGE_FRAGMENT,SSL_R_UNEXPECTED_MESSAGE);
                goto f_err;
                }

        /* parse the message fragment header */
        dtls1_get_message_header(wire, &msg_hdr);

        /* 
         * if this is a future (or stale) message it gets buffered
         * (or dropped)--no further processing at this time
         * While listening, we accept seq 1 (ClientHello with cookie)
         * although we're still expecting seq 0 (ClientHello)
         */
        if (msg_hdr.seq != s->d1->handshake_read_seq && !(s->d1->listen && msg_hdr.seq == 1))
                return dtls1_process_out_of_seq_message(s, &msg_hdr, ok);

        len = msg_hdr.msg_len;
        frag_off = msg_hdr.frag_off;
        frag_len = msg_hdr.frag_len;

        if (frag_len && frag_len < len)
                return dtls1_reassemble_fragment(s, &msg_hdr, ok);

        if (!s->server && s->d1->r_msg_hdr.frag_off == 0 &&
                wire[0] == SSL3_MT_HELLO_REQUEST)
                {
                /* The server may always send 'Hello Request' messages --
                 * we are doing a handshake anyway now, so ignore them
                 * if their format is correct. Does not count for
                 * 'Finished' MAC. */
                if (wire[1] == 0 && wire[2] == 0 && wire[3] == 0)
                        {
                        if (s->msg_callback)
                                s->msg_callback(0, s->version, SSL3_RT_HANDSHAKE, 
                                        wire, DTLS1_HM_HEADER_LENGTH, s, 
                                        s->msg_callback_arg);
                        
                        s->init_num = 0;
                        goto redo;
                        }
                else /* Incorrectly formated Hello request */
                        {
                        al=SSL_AD_UNEXPECTED_MESSAGE;
                        SSLerr(SSL_F_DTLS1_GET_MESSAGE_FRAGMENT,SSL_R_UNEXPECTED_MESSAGE);
                        goto f_err;
                        }
                }

        if ((al=dtls1_preprocess_fragment(s,&msg_hdr,max)))
                goto f_err;

        /* XDTLS:  ressurect this when restart is in place */
        s->state=stn;

        if ( frag_len > 0)
                {
                unsigned char *p=(unsigned char *)s->init_buf->data+DTLS1_HM_HEADER_LENGTH;

                i=s->method->ssl_read_bytes(s,SSL3_RT_HANDSHAKE,
                        &p[frag_off],frag_len,0);
                /* XDTLS:  fix this--message fragments cannot span multiple packets */
                if (i <= 0)
                        {
                        s->rwstate=SSL_READING;
                        *ok = 0;
                        return i;
                        }
                }
        else
                i = 0;

        /* XDTLS:  an incorrectly formatted fragment should cause the 
         * handshake to fail */
        if (i != (int)frag_len)
                {
                al=SSL3_AD_ILLEGAL_PARAMETER;
                SSLerr(SSL_F_DTLS1_GET_MESSAGE_FRAGMENT,SSL3_AD_ILLEGAL_PARAMETER);
                goto f_err;
                }

        *ok = 1;

        /* Note that s->init_num is *not* used as current offset in
         * s->init_buf->data, but as a counter summing up fragments'
         * lengths: as soon as they sum up to handshake packet
         * length, we assume we have got all the fragments. */
        s->init_num = frag_len;
        return frag_len;

f_err:
        ssl3_send_alert(s,SSL3_AL_FATAL,al);
        s->init_num = 0;

        *ok=0;
        return(-1);
        }

/* for these 2 messages, we need to
 * ssl->enc_read_ctx                    re-init
 * ssl->s3->read_sequence               zero
 * ssl->s3->read_mac_secret             re-init
 * ssl->session->read_sym_enc           assign
 * ssl->session->read_compression       assign
 * ssl->session->read_hash              assign
 */
int dtls1_send_change_cipher_spec(SSL *s, int a, int b)
        { 
        unsigned char *p;

        if (s->state == a)
                {
                p=(unsigned char *)s->init_buf->data;
                *p++=SSL3_MT_CCS;
                s->d1->handshake_write_seq = s->d1->next_handshake_write_seq;
                s->init_num=DTLS1_CCS_HEADER_LENGTH;

                if (s->version == DTLS1_BAD_VER) {
                        s->d1->next_handshake_write_seq++;
                        s2n(s->d1->handshake_write_seq,p);
                        s->init_num+=2;
                }

                s->init_off=0;

                dtls1_set_message_header_int(s, SSL3_MT_CCS, 0, 
                        s->d1->handshake_write_seq, 0, 0);

                /* buffer the message to handle re-xmits */
                dtls1_buffer_message(s, 1);

                s->state=b;
                }

        /* SSL3_ST_CW_CHANGE_B */
        return(dtls1_do_write(s,SSL3_RT_CHANGE_CIPHER_SPEC));
        }

int dtls1_read_failed(SSL *s, int code)
        {
        if ( code > 0)
                {
                fprintf( stderr, "invalid state reached %s:%d", __FILE__, __LINE__);
                return 1;
                }

        if (!dtls1_is_timer_expired(s))
                {
                /* not a timeout, none of our business, 
                   let higher layers handle this.  in fact it's probably an error */
                return code;
                }

#ifndef OPENSSL_NO_HEARTBEATS
        if (!SSL_in_init(s) && !s->tlsext_hb_pending)  /* done, no need to send a retransmit */
#else
        if (!SSL_in_init(s))  /* done, no need to send a retransmit */
#endif
                {
                BIO_set_flags(SSL_get_rbio(s), BIO_FLAGS_READ);
                return code;
                }

#if 0 /* for now, each alert contains only one record number */
        item = pqueue_peek(state->rcvd_records);
        if ( item )
                {
                /* send an alert immediately for all the missing records */
                }
        else
#endif

#if 0  /* no more alert sending, just retransmit the last set of messages */
        if ( state->timeout.read_timeouts >= DTLS1_TMO_READ_COUNT)
                ssl3_send_alert(s,SSL3_AL_WARNING,
                        DTLS1_AD_MISSING_HANDSHAKE_MESSAGE);
#endif

        return dtls1_handle_timeout(s);
        }

int
dtls1_get_queue_priority(unsigned short seq, int is_ccs)
        {
        /* The index of the retransmission queue actually is the message sequence number,
         * since the queue only contains messages of a single handshake. However, the
         * ChangeCipherSpec has no message sequence number and so using only the sequence
         * will result in the CCS and Finished having the same index. To prevent this,
         * the sequence number is multiplied by 2. In case of a CCS 1 is subtracted.
         * This does not only differ CSS and Finished, it also maintains the order of the
         * index (important for priority queues) and fits in the unsigned short variable.
         */     
        return seq * 2 - is_ccs;
        }

int
dtls1_retransmit_buffered_messages(SSL *s)
        {
        pqueue sent = s->d1->sent_messages;
        piterator iter;
        pitem *item;
        hm_fragment *frag;
        int found = 0;

        iter = pqueue_iterator(sent);

        for ( item = pqueue_next(&iter); item != NULL; item = pqueue_next(&iter))
                {
                frag = (hm_fragment *)item->data;
                        if ( dtls1_retransmit_message(s,
                                (unsigned short)dtls1_get_queue_priority(frag->msg_header.seq, frag->msg_header.is_ccs),
                                0, &found) <= 0 && found)
                        {
                        fprintf(stderr, "dtls1_retransmit_message() failed\n");
                        return -1;
                        }
                }

        return 1;
        }

int
dtls1_buffer_message(SSL *s, int is_ccs)
        {
        pitem *item;
        hm_fragment *frag;
        unsigned char seq64be[8];

        /* this function is called immediately after a message has 
         * been serialized */
        OPENSSL_assert(s->init_off == 0);

        frag = dtls1_hm_fragment_new(s->init_num, 0);
        if (!frag)
                return 0;

        memcpy(frag->fragment, s->init_buf->data, s->init_num);

        if ( is_ccs)
                {
                OPENSSL_assert(s->d1->w_msg_hdr.msg_len + 
                               DTLS1_CCS_HEADER_LENGTH == (unsigned int)s->init_num);
                }
        else
                {
                OPENSSL_assert(s->d1->w_msg_hdr.msg_len + 
                        DTLS1_HM_HEADER_LENGTH == (unsigned int)s->init_num);
                }

        frag->msg_header.msg_len = s->d1->w_msg_hdr.msg_len;
        frag->msg_header.seq = s->d1->w_msg_hdr.seq;
        frag->msg_header.type = s->d1->w_msg_hdr.type;
        frag->msg_header.frag_off = 0;
        frag->msg_header.frag_len = s->d1->w_msg_hdr.msg_len;
        frag->msg_header.is_ccs = is_ccs;

        /* save current state*/
        frag->msg_header.saved_retransmit_state.enc_write_ctx = s->enc_write_ctx;
        frag->msg_header.saved_retransmit_state.write_hash = s->write_hash;
        frag->msg_header.saved_retransmit_state.compress = s->compress;
        frag->msg_header.saved_retransmit_state.session = s->session;
        frag->msg_header.saved_retransmit_state.epoch = s->d1->w_epoch;
        
        memset(seq64be,0,sizeof(seq64be));
        seq64be[6] = (unsigned char)(dtls1_get_queue_priority(frag->msg_header.seq,
                                                                                                                  frag->msg_header.is_ccs)>>8);
        seq64be[7] = (unsigned char)(dtls1_get_queue_priority(frag->msg_header.seq,
                                                                                                                  frag->msg_header.is_ccs));

        item = pitem_new(seq64be, frag);
        if ( item == NULL)
                {
                dtls1_hm_fragment_free(frag);
                return 0;
                }

#if 0
        fprintf( stderr, "buffered messge: \ttype = %xx\n", msg_buf->type);
        fprintf( stderr, "\t\t\t\t\tlen = %d\n", msg_buf->len);
        fprintf( stderr, "\t\t\t\t\tseq_num = %d\n", msg_buf->seq_num);
#endif

        pqueue_insert(s->d1->sent_messages, item);
        return 1;
        }

int
dtls1_retransmit_message(SSL *s, unsigned short seq, unsigned long frag_off,
        int *found)
        {
        int ret;
        /* XDTLS: for now assuming that read/writes are blocking */
        pitem *item;
        hm_fragment *frag ;
        unsigned long header_length;
        unsigned char seq64be[8];
        struct dtls1_retransmit_state saved_state;
        unsigned char save_write_sequence[8];

        /*
          OPENSSL_assert(s->init_num == 0);
          OPENSSL_assert(s->init_off == 0);
         */

        /* XDTLS:  the requested message ought to be found, otherwise error */
        memset(seq64be,0,sizeof(seq64be));
        seq64be[6] = (unsigned char)(seq>>8);
        seq64be[7] = (unsigned char)seq;

        item = pqueue_find(s->d1->sent_messages, seq64be);
        if ( item == NULL)
                {
                fprintf(stderr, "retransmit:  message %d non-existant\n", seq);
                *found = 0;
                return 0;
                }

        *found = 1;
        frag = (hm_fragment *)item->data;

        if ( frag->msg_header.is_ccs)
                header_length = DTLS1_CCS_HEADER_LENGTH;
        else
                header_length = DTLS1_HM_HEADER_LENGTH;

        memcpy(s->init_buf->data, frag->fragment, 
                frag->msg_header.msg_len + header_length);
                s->init_num = frag->msg_header.msg_len + header_length;

        dtls1_set_message_header_int(s, frag->msg_header.type, 
                frag->msg_header.msg_len, frag->msg_header.seq, 0, 
                frag->msg_header.frag_len);

        /* save current state */
        saved_state.enc_write_ctx = s->enc_write_ctx;
        saved_state.write_hash = s->write_hash;
        saved_state.compress = s->compress;
        saved_state.session = s->session;
        saved_state.epoch = s->d1->w_epoch;
        saved_state.epoch = s->d1->w_epoch;
        
        s->d1->retransmitting = 1;
        
        /* restore state in which the message was originally sent */
        s->enc_write_ctx = frag->msg_header.saved_retransmit_state.enc_write_ctx;
        s->write_hash = frag->msg_header.saved_retransmit_state.write_hash;
        s->compress = frag->msg_header.saved_retransmit_state.compress;
        s->session = frag->msg_header.saved_retransmit_state.session;
        s->d1->w_epoch = frag->msg_header.saved_retransmit_state.epoch;
        
        if (frag->msg_header.saved_retransmit_state.epoch == saved_state.epoch - 1)
        {
                memcpy(save_write_sequence, s->s3->write_sequence, sizeof(s->s3->write_sequence));
                memcpy(s->s3->write_sequence, s->d1->last_write_sequence, sizeof(s->s3->write_sequence));
        }
        
        ret = dtls1_do_write(s, frag->msg_header.is_ccs ? 
                                                 SSL3_RT_CHANGE_CIPHER_SPEC : SSL3_RT_HANDSHAKE);
        
        /* restore current state */
        s->enc_write_ctx = saved_state.enc_write_ctx;
        s->write_hash = saved_state.write_hash;
        s->compress = saved_state.compress;
        s->session = saved_state.session;
        s->d1->w_epoch = saved_state.epoch;
        
        if (frag->msg_header.saved_retransmit_state.epoch == saved_state.epoch - 1)
        {
                memcpy(s->d1->last_write_sequence, s->s3->write_sequence, sizeof(s->s3->write_sequence));
                memcpy(s->s3->write_sequence, save_write_sequence, sizeof(s->s3->write_sequence));
        }

        s->d1->retransmitting = 0;

        (void)BIO_flush(SSL_get_wbio(s));
        return ret;
        }

/* call this function when the buffered messages are no longer needed */
void
dtls1_clear_record_buffer(SSL *s)
        {
        pitem *item;

        for(item = pqueue_pop(s->d1->sent_messages);
                item != NULL; item = pqueue_pop(s->d1->sent_messages))
                {
                dtls1_hm_fragment_free((hm_fragment *)item->data);
                pitem_free(item);
                }
        }


unsigned char *
dtls1_set_message_header(SSL *s, unsigned char *p, unsigned char mt,
                        unsigned long len, unsigned long frag_off, unsigned long frag_len)
        {
        /* Don't change sequence numbers while listening */
        if (frag_off == 0 && !s->d1->listen)
                {
                s->d1->handshake_write_seq = s->d1->next_handshake_write_seq;
                s->d1->next_handshake_write_seq++;
                }

        dtls1_set_message_header_int(s, mt, len, s->d1->handshake_write_seq,
                frag_off, frag_len);

        return p += DTLS1_HM_HEADER_LENGTH;
        }


/* don't actually do the writing, wait till the MTU has been retrieved */
static void
dtls1_set_message_header_int(SSL *s, unsigned char mt,
                            unsigned long len, unsigned short seq_num, unsigned long frag_off,
                            unsigned long frag_len)
        {
        struct hm_header_st *msg_hdr = &s->d1->w_msg_hdr;

        msg_hdr->type = mt;
        msg_hdr->msg_len = len;
        msg_hdr->seq = seq_num;
        msg_hdr->frag_off = frag_off;
        msg_hdr->frag_len = frag_len;
        }

static void
dtls1_fix_message_header(SSL *s, unsigned long frag_off,
                        unsigned long frag_len)
        {
        struct hm_header_st *msg_hdr = &s->d1->w_msg_hdr;

        msg_hdr->frag_off = frag_off;
        msg_hdr->frag_len = frag_len;
        }

static unsigned char *
dtls1_write_message_header(SSL *s, unsigned char *p)
        {
        struct hm_header_st *msg_hdr = &s->d1->w_msg_hdr;

        *p++ = msg_hdr->type;
        l2n3(msg_hdr->msg_len, p);

        s2n(msg_hdr->seq, p);
        l2n3(msg_hdr->frag_off, p);
        l2n3(msg_hdr->frag_len, p);

        return p;
        }

unsigned int 
dtls1_min_mtu(void)
        {
        return (g_probable_mtu[(sizeof(g_probable_mtu) / 
                sizeof(g_probable_mtu[0])) - 1]);
        }

static unsigned int 
dtls1_guess_mtu(unsigned int curr_mtu)
        {
        unsigned int i;

        if ( curr_mtu == 0 )
                return g_probable_mtu[0] ;

        for ( i = 0; i < sizeof(g_probable_mtu)/sizeof(g_probable_mtu[0]); i++)
                if ( curr_mtu > g_probable_mtu[i])
                        return g_probable_mtu[i];

        return curr_mtu;
        }

void
dtls1_get_message_header(unsigned char *data, struct hm_header_st *msg_hdr)
        {
        memset(msg_hdr, 0x00, sizeof(struct hm_header_st));
        msg_hdr->type = *(data++);
        n2l3(data, msg_hdr->msg_len);

        n2s(data, msg_hdr->seq);
        n2l3(data, msg_hdr->frag_off);
        n2l3(data, msg_hdr->frag_len);
        }

void
dtls1_get_ccs_header(unsigned char *data, struct ccs_header_st *ccs_hdr)
        {
        memset(ccs_hdr, 0x00, sizeof(struct ccs_header_st));

        ccs_hdr->type = *(data++);
        }

int dtls1_shutdown(SSL *s)
        {
        int ret;
#ifndef OPENSSL_NO_SCTP
        if (BIO_dgram_is_sctp(SSL_get_wbio(s)) &&
            !(s->shutdown & SSL_SENT_SHUTDOWN))
                {
                ret = BIO_dgram_sctp_wait_for_dry(SSL_get_wbio(s));
                if (ret < 0) return -1;

                if (ret == 0)
                        BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SAVE_SHUTDOWN, 1, NULL);
                }
#endif
        ret = ssl3_shutdown(s);
#ifndef OPENSSL_NO_SCTP
        BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SAVE_SHUTDOWN, 0, NULL);
#endif
        return ret;
        }

#ifndef OPENSSL_NO_HEARTBEATS
int
dtls1_process_heartbeat(SSL *s)
        {
        unsigned char *p = &s->s3->rrec.data[0], *pl;
        unsigned short hbtype;
        unsigned int payload;
        unsigned int padding = 16; /* Use minimum padding */

        if (s->msg_callback)
                s->msg_callback(0, s->version, TLS1_RT_HEARTBEAT,
                        &s->s3->rrec.data[0], s->s3->rrec.length,
                        s, s->msg_callback_arg);

        /* Read type and payload length first */
        if (1 + 2 + 16 > s->s3->rrec.length)
                return 0; /* silently discard */
        if (s->s3->rrec.length > SSL3_RT_MAX_PLAIN_LENGTH)
                return 0; /* silently discard per RFC 6520 sec. 4 */

        hbtype = *p++;
        n2s(p, payload);
        if (1 + 2 + payload + 16 > s->s3->rrec.length)
                return 0; /* silently discard per RFC 6520 sec. 4 */
        pl = p;

        if (hbtype == TLS1_HB_REQUEST)
                {
                unsigned char *buffer, *bp;
                unsigned int write_length = 1 /* heartbeat type */ +
                                            2 /* heartbeat length */ +
                                            payload + padding;
                int r;

                if (write_length > SSL3_RT_MAX_PLAIN_LENGTH)
                        return 0;

                /* Allocate memory for the response, size is 1 byte
                 * message type, plus 2 bytes payload length, plus
                 * payload, plus padding
                 */
                buffer = OPENSSL_malloc(write_length);
                bp = buffer;

                /* Enter response type, length and copy payload */
                *bp++ = TLS1_HB_RESPONSE;
                s2n(payload, bp);
                memcpy(bp, pl, payload);
                bp += payload;
                /* Random padding */
                RAND_pseudo_bytes(bp, padding);

                r = dtls1_write_bytes(s, TLS1_RT_HEARTBEAT, buffer, write_length);

                if (r >= 0 && s->msg_callback)
                        s->msg_callback(1, s->version, TLS1_RT_HEARTBEAT,
                                buffer, write_length,
                                s, s->msg_callback_arg);

                OPENSSL_free(buffer);

                if (r < 0)
                        return r;
                }
        else if (hbtype == TLS1_HB_RESPONSE)
                {
                unsigned int seq;

                /* We only send sequence numbers (2 bytes unsigned int),
                 * and 16 random bytes, so we just try to read the
                 * sequence number */
                n2s(pl, seq);

                if (payload == 18 && seq == s->tlsext_hb_seq)
                        {
                        dtls1_stop_timer(s);
                        s->tlsext_hb_seq++;
                        s->tlsext_hb_pending = 0;
                        }
                }

        return 0;
        }

int
dtls1_heartbeat(SSL *s)
        {
        unsigned char *buf, *p;
        int ret;
        unsigned int payload = 18; /* Sequence number + random bytes */
        unsigned int padding = 16; /* Use minimum padding */

        /* Only send if peer supports and accepts HB requests... */
        if (!(s->tlsext_heartbeat & SSL_TLSEXT_HB_ENABLED) ||
            s->tlsext_heartbeat & SSL_TLSEXT_HB_DONT_SEND_REQUESTS)
                {
                SSLerr(SSL_F_DTLS1_HEARTBEAT,SSL_R_TLS_HEARTBEAT_PEER_DOESNT_ACCEPT);
                return -1;
                }

        /* ...and there is none in flight yet... */
        if (s->tlsext_hb_pending)
                {
                SSLerr(SSL_F_DTLS1_HEARTBEAT,SSL_R_TLS_HEARTBEAT_PENDING);
                return -1;
                }

        /* ...and no handshake in progress. */
        if (SSL_in_init(s) || s->in_handshake)
                {
                SSLerr(SSL_F_DTLS1_HEARTBEAT,SSL_R_UNEXPECTED_MESSAGE);
                return -1;
                }

        /* Check if padding is too long, payload and padding
         * must not exceed 2^14 - 3 = 16381 bytes in total.
         */
        OPENSSL_assert(payload + padding <= 16381);

        /* Create HeartBeat message, we just use a sequence number
         * as payload to distuingish different messages and add
         * some random stuff.
         *  - Message Type, 1 byte
         *  - Payload Length, 2 bytes (unsigned int)
         *  - Payload, the sequence number (2 bytes uint)
         *  - Payload, random bytes (16 bytes uint)
         *  - Padding
         */
        buf = OPENSSL_malloc(1 + 2 + payload + padding);
        p = buf;
        /* Message Type */
        *p++ = TLS1_HB_REQUEST;
        /* Payload length (18 bytes here) */
        s2n(payload, p);
        /* Sequence number */
        s2n(s->tlsext_hb_seq, p);
        /* 16 random bytes */
        RAND_pseudo_bytes(p, 16);
        p += 16;
        /* Random padding */
        RAND_pseudo_bytes(p, padding);

        ret = dtls1_write_bytes(s, TLS1_RT_HEARTBEAT, buf, 3 + payload + padding);
        if (ret >= 0)
                {
                if (s->msg_callback)
                        s->msg_callback(1, s->version, TLS1_RT_HEARTBEAT,
                                buf, 3 + payload + padding,
                                s, s->msg_callback_arg);

                dtls1_start_timer(s);
                s->tlsext_hb_pending = 1;
                }

        OPENSSL_free(buf);

        return ret;
        }
#endif