Unleashed v1.4

[unleashed.git] / lib / libssl / d1_both.c

/* $OpenBSD: d1_both.c,v 1.55 2018/09/05 16:58:59 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 <limits.h>
#include <stdio.h>
#include <string.h>

#include "ssl_locl.h"

#include <openssl/buffer.h>
#include <openssl/evp.h>
#include <openssl/objects.h>
#include <openssl/x509.h>

#include "pqueue.h"
#include "bytestring.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; } }

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 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 int dtls1_write_message_header(const struct hm_header_st *msg_hdr,
    unsigned long frag_off, unsigned long frag_len, unsigned char *p);
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 = malloc(sizeof(hm_fragment));
        if (frag == NULL)
                return NULL;

        if (frag_len) {
                buf = malloc(frag_len);
                if (buf == NULL) {
                        free(frag);
                        return NULL;
                }
        }

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

        /* Initialize reassembly bitmask if necessary */
        if (reassembly) {
                bitmask = malloc(RSMBLY_BITMASK_SIZE(frag_len));
                if (bitmask == NULL) {
                        free(buf);
                        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 == NULL)
                return;

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

/* send s->internal->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 (D1I(s)->mtu < dtls1_min_mtu() &&
            !(SSL_get_options(s) & SSL_OP_NO_QUERY_MTU)) {
                D1I(s)->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 the MTU (ie., the initial write), so just
                 * make sure we have a reasonable number
                 */
                if (D1I(s)->mtu < dtls1_min_mtu()) {
                        D1I(s)->mtu = 0;
                        D1I(s)->mtu = dtls1_guess_mtu(D1I(s)->mtu);
                        BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SET_MTU,
                            D1I(s)->mtu, NULL);
                }
        }

        OPENSSL_assert(D1I(s)->mtu >= dtls1_min_mtu());
        /* should have something reasonable now */

        if (s->internal->init_off == 0  && type == SSL3_RT_HANDSHAKE)
                OPENSSL_assert(s->internal->init_num ==
                    (int)D1I(s)->w_msg_hdr.msg_len + DTLS1_HM_HEADER_LENGTH);

        if (s->internal->write_hash)
                mac_size = EVP_MD_CTX_size(s->internal->write_hash);
        else
                mac_size = 0;

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

        frag_off = 0;
        while (s->internal->init_num) {
                curr_mtu = D1I(s)->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 = D1I(s)->mtu - DTLS1_RT_HEADER_LENGTH -
                            mac_size - blocksize;
                }

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


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

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

                        dtls1_fix_message_header(s, frag_off,
                            len - DTLS1_HM_HEADER_LENGTH);

                        if (!dtls1_write_message_header(&D1I(s)->w_msg_hdr,
                            D1I(s)->w_msg_hdr.frag_off, D1I(s)->w_msg_hdr.frag_len,
                            (unsigned char *)&s->internal->init_buf->data[s->internal->init_off]))
                                return -1;

                        OPENSSL_assert(len >= DTLS1_HM_HEADER_LENGTH);
                }

                ret = dtls1_write_bytes(s, type,
                    &s->internal->init_buf->data[s->internal->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)
                                D1I(s)->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 &&
                            !D1I(s)->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->internal->init_buf->data[s->internal->init_off];
                                const struct hm_header_st *msg_hdr = &D1I(s)->w_msg_hdr;
                                int xlen;

                                if (frag_off == 0) {
                                        /*
                                         * Reconstruct message header is if it
                                         * is being sent in single fragment
                                         */
                                        if (!dtls1_write_message_header(msg_hdr,
                                            0, msg_hdr->msg_len, p))
                                                return (-1);
                                        xlen = ret;
                                } else {
                                        p += DTLS1_HM_HEADER_LENGTH;
                                        xlen = ret - DTLS1_HM_HEADER_LENGTH;
                                }

                                tls1_finish_mac(s, p, xlen);
                        }

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

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

                                return (1);
                        }
                        s->internal->init_off += ret;
                        s->internal->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->internal->tmp is used to store messages that are unexpected, caused
         * by the absence of an optional handshake message
         */
        if (S3I(s)->tmp.reuse_message) {
                S3I(s)->tmp.reuse_message = 0;
                if ((mt >= 0) && (S3I(s)->tmp.message_type != mt)) {
                        al = SSL_AD_UNEXPECTED_MESSAGE;
                        SSLerror(s, SSL_R_UNEXPECTED_MESSAGE);
                        goto f_err;
                }
                *ok = 1;
                s->internal->init_msg = s->internal->init_buf->data + DTLS1_HM_HEADER_LENGTH;
                s->internal->init_num = (int)S3I(s)->tmp.message_size;
                return s->internal->init_num;
        }

        msg_hdr = &D1I(s)->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->internal->init_buf->data;
        msg_len = msg_hdr->msg_len;

        /* reconstruct message header */
        if (!dtls1_write_message_header(msg_hdr, 0, msg_len, p))
                return -1;

        msg_len += DTLS1_HM_HEADER_LENGTH;

        tls1_finish_mac(s, p, msg_len);
        if (s->internal->msg_callback)
                s->internal->msg_callback(0, s->version, SSL3_RT_HANDSHAKE, p, msg_len,
                    s, s->internal->msg_callback_arg);

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

        /* Don't change sequence numbers while listening */
        if (!D1I(s)->listen)
                D1I(s)->handshake_read_seq++;

        s->internal->init_msg = s->internal->init_buf->data + DTLS1_HM_HEADER_LENGTH;
        return s->internal->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) {
                SSLerror(s, SSL_R_EXCESSIVE_MESSAGE_SIZE);
                return SSL_AD_ILLEGAL_PARAMETER;
        }

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

        if ( D1I(s)->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->internal->init_buf,
                    msg_len + DTLS1_HM_HEADER_LENGTH)) {
                        SSLerror(s, ERR_R_BUF_LIB);
                        return SSL_AD_INTERNAL_ERROR;
                }

                S3I(s)->tmp.message_size = msg_len;
                D1I(s)->r_msg_hdr.msg_len = msg_len;
                S3I(s)->tmp.message_type = msg_hdr->type;
                D1I(s)->r_msg_hdr.type = msg_hdr->type;
                D1I(s)->r_msg_hdr.seq = msg_hdr->seq;
        } else if (msg_len != D1I(s)->r_msg_hdr.msg_len) {
                /*
                 * They must be playing with us! BTW, failure to enforce
                 * upper limit would open possibility for buffer overrun.
                 */
                SSLerror(s, 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->internal->init_buf->data[]
         * (2) update s->internal->init_num
         */
        pitem *item;
        hm_fragment *frag;
        int al;

        *ok = 0;
        item = pqueue_peek(D1I(s)->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 (D1I(s)->handshake_read_seq == frag->msg_header.seq) {
                unsigned long frag_len = frag->msg_header.frag_len;
                pqueue_pop(D1I(s)->buffered_messages);

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

                if (al == 0) /* no alert */
                {
                        unsigned char *p = (unsigned char *)s->internal->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->internal->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;

        max_len = DTLS1_HM_HEADER_LENGTH + SSL3_RT_MAX_ENCRYPTED_LENGTH;
        if (max_len < (unsigned long)s->internal->max_cert_list)
                return s->internal->max_cert_list;
        return max_len;
}

static int
dtls1_reassemble_fragment(SSL *s, 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) {
                i = DTLS1_HM_FRAGMENT_RETRY;
                goto err;
        }

        /* 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(D1I(s)->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.
         */
        if (frag->reassembly == NULL) {
                unsigned char devnull [256];

                while (frag_len) {
                        i = s->method->internal->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;
                }
                i = DTLS1_HM_FRAGMENT_RETRY;
                goto err;
        }

        /* read the body of the fragment (header has already been read */
        i = s->method->internal->ssl_read_bytes(s, SSL3_RT_HANDSHAKE,
            frag->fragment + msg_hdr->frag_off, frag_len, 0);
        if (i <= 0 || (unsigned long)i != frag_len)
                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) {
                free(frag->reassembly);
                frag->reassembly = NULL;
        }

        if (item == NULL) {
                memset(seq64be, 0, sizeof(seq64be));
                seq64be[6] = (unsigned char)(msg_hdr->seq >> 8);
                seq64be[7] = (unsigned char)(msg_hdr->seq);

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

                pqueue_insert(D1I(s)->buffered_messages, item);
        }

        return DTLS1_HM_FRAGMENT_RETRY;

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


static int
dtls1_process_out_of_seq_message(SSL *s, 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(D1I(s)->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 <= D1I(s)->handshake_read_seq ||
            msg_hdr->seq > D1I(s)->handshake_read_seq + 10 || item != NULL ||
            (D1I(s)->handshake_read_seq == 0 &&
            msg_hdr->type == SSL3_MT_FINISHED)) {
                unsigned char devnull [256];

                while (frag_len) {
                        i = s->method->internal->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->internal->ssl_read_bytes(s, SSL3_RT_HANDSHAKE,
                            frag->fragment, frag_len, 0);
                        if (i <= 0 || (unsigned long)i != frag_len)
                                goto err;
                }

                memset(seq64be, 0, sizeof(seq64be));
                seq64be[6] = (unsigned char)(msg_hdr->seq >> 8);
                seq64be[7] = (unsigned char)(msg_hdr->seq);

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

                pqueue_insert(D1I(s)->buffered_messages, item);
        }

        return DTLS1_HM_FRAGMENT_RETRY;

err:
        if (item == NULL && frag != 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;

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

        /* read handshake message header */
        i = s->method->internal->ssl_read_bytes(s, SSL3_RT_HANDSHAKE, wire,
            DTLS1_HM_HEADER_LENGTH, 0);
        if (i <= 0)     /* nbio, or an error */
        {
                s->internal->rwstate = SSL_READING;
                *ok = 0;
                return i;
        }
        /* Handshake fails if message header is incomplete */
        if (i != DTLS1_HM_HEADER_LENGTH ||
            /* parse the message fragment header */
            dtls1_get_message_header(wire, &msg_hdr) == 0) {
                al = SSL_AD_UNEXPECTED_MESSAGE;
                SSLerror(s, SSL_R_UNEXPECTED_MESSAGE);
                goto f_err;
        }

        /*
         * 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 != D1I(s)->handshake_read_seq &&
            !(D1I(s)->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 && D1I(s)->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->internal->msg_callback)
                                s->internal->msg_callback(0, s->version,
                                    SSL3_RT_HANDSHAKE, wire,
                                    DTLS1_HM_HEADER_LENGTH, s,
                                    s->internal->msg_callback_arg);

                        s->internal->init_num = 0;
                        goto again;
                }
                else /* Incorrectly formated Hello request */
                {
                        al = SSL_AD_UNEXPECTED_MESSAGE;
                        SSLerror(s, 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 */
        S3I(s)->hs.state = stn;

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

                i = s->method->internal->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->internal->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;
                SSLerror(s, SSL3_AD_ILLEGAL_PARAMETER);
                goto f_err;
        }

        *ok = 1;

        /*
         * Note that s->internal->init_num is *not* used as current offset in
         * s->internal->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->internal->init_num = frag_len;
        return frag_len;

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

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

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

        if (!SSL_in_init(s))  /* done, no need to send a retransmit */
        {
                BIO_set_flags(SSL_get_rbio(s), BIO_FLAGS_READ);
                return code;
        }

        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) {
#ifdef DEBUG
                        fprintf(stderr, "dtls1_retransmit_message() failed\n");
#endif
                        return -1;
                }
        }

        return 1;
}

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

        /* Buffer the messsage in order to handle DTLS retransmissions. */

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

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

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

        if (is_ccs) {
                OPENSSL_assert(D1I(s)->w_msg_hdr.msg_len +
                    ((s->version == DTLS1_VERSION) ?
                    DTLS1_CCS_HEADER_LENGTH : 3) == (unsigned int)s->internal->init_num);
        } else {
                OPENSSL_assert(D1I(s)->w_msg_hdr.msg_len +
                    DTLS1_HM_HEADER_LENGTH == (unsigned int)s->internal->init_num);
        }

        frag->msg_header.msg_len = D1I(s)->w_msg_hdr.msg_len;
        frag->msg_header.seq = D1I(s)->w_msg_hdr.seq;
        frag->msg_header.type = D1I(s)->w_msg_hdr.type;
        frag->msg_header.frag_off = 0;
        frag->msg_header.frag_len = D1I(s)->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->internal->enc_write_ctx;
        frag->msg_header.saved_retransmit_state.write_hash = s->internal->write_hash;
        frag->msg_header.saved_retransmit_state.session = s->session;
        frag->msg_header.saved_retransmit_state.epoch = D1I(s)->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;
        }

        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->internal->init_num == 0);
          OPENSSL_assert(s->internal->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) {
#ifdef DEBUG
                fprintf(stderr, "retransmit:  message %d non-existant\n", seq);
#endif
                *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->internal->init_buf->data, frag->fragment,
            frag->msg_header.msg_len + header_length);
        s->internal->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->internal->enc_write_ctx;
        saved_state.write_hash = s->internal->write_hash;
        saved_state.session = s->session;
        saved_state.epoch = D1I(s)->w_epoch;

        D1I(s)->retransmitting = 1;

        /* restore state in which the message was originally sent */
        s->internal->enc_write_ctx = frag->msg_header.saved_retransmit_state.enc_write_ctx;
        s->internal->write_hash = frag->msg_header.saved_retransmit_state.write_hash;
        s->session = frag->msg_header.saved_retransmit_state.session;
        D1I(s)->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, S3I(s)->write_sequence,
                    sizeof(S3I(s)->write_sequence));
                memcpy(S3I(s)->write_sequence, D1I(s)->last_write_sequence,
                    sizeof(S3I(s)->write_sequence));
        }

        ret = dtls1_do_write(s, frag->msg_header.is_ccs ?
            SSL3_RT_CHANGE_CIPHER_SPEC : SSL3_RT_HANDSHAKE);

        /* restore current state */
        s->internal->enc_write_ctx = saved_state.enc_write_ctx;
        s->internal->write_hash = saved_state.write_hash;
        s->session = saved_state.session;
        D1I(s)->w_epoch = saved_state.epoch;

        if (frag->msg_header.saved_retransmit_state.epoch ==
            saved_state.epoch - 1) {
                memcpy(D1I(s)->last_write_sequence, S3I(s)->write_sequence,
                    sizeof(S3I(s)->write_sequence));
                memcpy(S3I(s)->write_sequence, save_write_sequence,
                    sizeof(S3I(s)->write_sequence));
        }

        D1I(s)->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);
        }
}

void
dtls1_set_message_header(SSL *s, 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 && !D1I(s)->listen) {
                D1I(s)->handshake_write_seq = D1I(s)->next_handshake_write_seq;
                D1I(s)->next_handshake_write_seq++;
        }

        dtls1_set_message_header_int(s, mt, len, D1I(s)->handshake_write_seq,
            frag_off, frag_len);
}

/* don't actually do the writing, wait till the MTU has been retrieved */
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 = &D1I(s)->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 = &D1I(s)->w_msg_hdr;

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

static int
dtls1_write_message_header(const struct hm_header_st *msg_hdr,
    unsigned long frag_off, unsigned long frag_len, unsigned char *p)
{
        CBB cbb;

        /* We assume DTLS1_HM_HEADER_LENGTH bytes are available for now... */
        if (!CBB_init_fixed(&cbb, p, DTLS1_HM_HEADER_LENGTH))
                return 0;
        if (!CBB_add_u8(&cbb, msg_hdr->type))
                goto err;
        if (!CBB_add_u24(&cbb, msg_hdr->msg_len))
                goto err;
        if (!CBB_add_u16(&cbb, msg_hdr->seq))
                goto err;
        if (!CBB_add_u24(&cbb, frag_off))
                goto err;
        if (!CBB_add_u24(&cbb, frag_len))
                goto err;
        if (!CBB_finish(&cbb, NULL, NULL))
                goto err;

        return 1;

 err:
        CBB_cleanup(&cbb);
        return 0;
}

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;
}

int
dtls1_get_message_header(unsigned char *data, struct hm_header_st *msg_hdr)
{
        CBS header;
        uint32_t msg_len, frag_off, frag_len;
        uint16_t seq;
        uint8_t type;

        CBS_init(&header, data, sizeof(*msg_hdr));

        memset(msg_hdr, 0, sizeof(*msg_hdr));

        if (!CBS_get_u8(&header, &type))
                return 0;
        if (!CBS_get_u24(&header, &msg_len))
                return 0;
        if (!CBS_get_u16(&header, &seq))
                return 0;
        if (!CBS_get_u24(&header, &frag_off))
                return 0;
        if (!CBS_get_u24(&header, &frag_len))
                return 0;

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

        return 1;
}

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++);
}