long ssl3_get_message(SSL *s, int st1, int stn, int mt, long max, int *ok)
{
    unsigned char *p;
    unsigned long l;
    long n;
    int i, al;

    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_SSL3_GET_MESSAGE, SSL_R_UNEXPECTED_MESSAGE);
            goto f_err;
        }
        *ok = 1;
        s->state = stn;
        s->init_msg = s->init_buf->data + SSL3_HM_HEADER_LENGTH;
        s->init_num = (int)s->s3->tmp.message_size;
        return s->init_num;
    }

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

    if (s->state == st1) {      /* s->init_num < SSL3_HM_HEADER_LENGTH */
        int skip_message;

        do {
            while (s->init_num < SSL3_HM_HEADER_LENGTH) {
                i = s->method->ssl_read_bytes(s, SSL3_RT_HANDSHAKE,
                                              &p[s->init_num],
                                              SSL3_HM_HEADER_LENGTH -
                                              s->init_num, 0);
                if (i <= 0) {
                    s->rwstate = SSL_READING;
                    *ok = 0;
                    return i;
                }
                s->init_num += i;
            }

            skip_message = 0;
            if (!s->server)
                if (p[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 (p[1] == 0 && p[2] == 0 && p[3] == 0) {
                        s->init_num = 0;
                        skip_message = 1;

                        if (s->msg_callback)
                            s->msg_callback(0, s->version, SSL3_RT_HANDSHAKE,
                                            p, SSL3_HM_HEADER_LENGTH, s,
                                            s->msg_callback_arg);
                    }
        }
        while (skip_message);

        /* s->init_num == SSL3_HM_HEADER_LENGTH */

        if ((mt >= 0) && (*p != mt)) {
            al = SSL_AD_UNEXPECTED_MESSAGE;
            SSLerr(SSL_F_SSL3_GET_MESSAGE, SSL_R_UNEXPECTED_MESSAGE);
            goto f_err;
        }
        if ((mt < 0) && (*p == SSL3_MT_CLIENT_HELLO) &&
            (st1 == SSL3_ST_SR_CERT_A) && (stn == SSL3_ST_SR_CERT_B)) {
            /*
             * At this point we have got an MS SGC second client hello (maybe
             * we should always allow the client to start a new handshake?).
             * We need to restart the mac. Don't increment
             * {num,total}_renegotiations because we have not completed the
             * handshake.
             */
            ssl3_init_finished_mac(s);
        }

        s->s3->tmp.message_type = *(p++);

        n2l3(p, l);
        if (l > (unsigned long)max) {
            al = SSL_AD_ILLEGAL_PARAMETER;
            SSLerr(SSL_F_SSL3_GET_MESSAGE, SSL_R_EXCESSIVE_MESSAGE_SIZE);
            goto f_err;
        }
        /*
         * Make buffer slightly larger than message length as a precaution
         * against small OOB reads e.g. CVE-2016-6306
         */
        if (l
            && !BUF_MEM_grow_clean(s->init_buf,
                                   (int)l + SSL3_HM_HEADER_LENGTH + 16)) {
            SSLerr(SSL_F_SSL3_GET_MESSAGE, ERR_R_BUF_LIB);
            goto err;
        }
        s->s3->tmp.message_size = l;
        s->state = stn;

        s->init_msg = s->init_buf->data + SSL3_HM_HEADER_LENGTH;
        s->init_num = 0;
    }

    /* next state (stn) */
    p = s->init_msg;
    n = s->s3->tmp.message_size - s->init_num;
    while (n > 0) {
        i = s->method->ssl_read_bytes(s, SSL3_RT_HANDSHAKE, &p[s->init_num],
                                      n, 0);
        if (i <= 0) {
            s->rwstate = SSL_READING;
            *ok = 0;
            return i;
        }
        s->init_num += i;
        n -= i;
    }

#ifndef OPENSSL_NO_NEXTPROTONEG
    /*
     * If receiving Finished, record MAC of prior handshake messages for
     * Finished verification.
     */
    if (*s->init_buf->data == SSL3_MT_FINISHED)
        ssl3_take_mac(s);
#endif

    /* Feed this message into MAC computation. */
    ssl3_finish_mac(s, (unsigned char *)s->init_buf->data,
                    s->init_num + SSL3_HM_HEADER_LENGTH);
    if (s->msg_callback)
        s->msg_callback(0, s->version, SSL3_RT_HANDSHAKE, s->init_buf->data,
                        (size_t)s->init_num + SSL3_HM_HEADER_LENGTH, s,
                        s->msg_callback_arg);
    *ok = 1;
    return s->init_num;
 f_err:
    ssl3_send_alert(s, SSL3_AL_FATAL, al);
 err:
    *ok = 0;
    return (-1);
}