WTF - HOW A CLIENT SAYS HELLO

static int ssl23_client_hello(SSL *s)
    {
    unsigned char *buf;
    unsigned char *p,*d;
    int i,ch_len;
    unsigned long l;
    int ssl2_compat;
    int version = 0, version_major, version_minor;
    int al = 0;
#ifndef OPENSSL_NO_COMP
    int j;
    SSL_COMP *comp;
#endif
    int ret;
    unsigned long mask, options = s->options;

    ssl2_compat = (options & SSL_OP_NO_SSLv2) ? 0 : 1;

    if (ssl2_compat && !ssl_security(s, SSL_SECOP_SSL2_COMPAT, 0, 0, NULL))
        ssl2_compat = 0;
    if (ssl2_compat && ssl23_no_ssl2_ciphers(s))
        ssl2_compat = 0;

    /*
     * SSL_OP_NO_X disables all protocols above X *if* there are
     * some protocols below X enabled. This is required in order
     * to maintain "version capability" vector contiguous. So
     * that if application wants to disable TLS1.0 in favour of
     * TLS1>=1, it would be insufficient to pass SSL_NO_TLSv1, the
     * answer is SSL_OP_NO_TLSv1|SSL_OP_NO_SSLv3|SSL_OP_NO_SSLv2.
     */
    mask =  SSL_OP_NO_TLSv1_1|SSL_OP_NO_TLSv1
#if !defined(OPENSSL_NO_SSL3)
        |SSL_OP_NO_SSLv3
#endif
#if !defined(OPENSSL_NO_SSL2)
        |(ssl2_compat?SSL_OP_NO_SSLv2:0)
#endif
        ;
#if !defined(OPENSSL_NO_TLS1_2_CLIENT)
    version = TLS1_2_VERSION;

    if ((options & SSL_OP_NO_TLSv1_2) && (options & mask) != mask)
        version = TLS1_1_VERSION;
#else
    version = TLS1_1_VERSION;
#endif
    mask &= ~SSL_OP_NO_TLSv1_1;
    if ((options & SSL_OP_NO_TLSv1_1) && (options & mask) != mask)
        version = TLS1_VERSION;
    mask &= ~SSL_OP_NO_TLSv1;
#if !defined(OPENSSL_NO_SSL3)
    if ((options & SSL_OP_NO_TLSv1) && (options & mask) != mask)
        version = SSL3_VERSION;
    mask &= ~SSL_OP_NO_SSLv3;
#endif
#if !defined(OPENSSL_NO_SSL2)
    if ((options & SSL_OP_NO_SSLv3) && (options & mask) != mask)
        version = SSL2_VERSION;
#endif

#ifndef OPENSSL_NO_TLSEXT
    if (version != SSL2_VERSION)
        {
        /* have to disable SSL 2.0 compatibility if we need TLS extensions */

        if (s->tlsext_hostname != NULL)
            ssl2_compat = 0;
        if (s->tlsext_status_type != -1)
            ssl2_compat = 0;
#ifdef TLSEXT_TYPE_opaque_prf_input
        if (s->ctx->tlsext_opaque_prf_input_callback != 0 || s->tlsext_opaque_prf_input != NULL)
            ssl2_compat = 0;
#endif
        if (s->ctx->custom_cli_ext_records_count != 0)
            ssl2_compat = 0;
        if (s->ctx->cli_supp_data_records_count != 0)
            ssl2_compat = 0;
        }
#endif

    buf=(unsigned char *)s->init_buf->data;
    if (s->state == SSL23_ST_CW_CLNT_HELLO_A)
        {
#if 0
        /* don't reuse session-id's */
        if (!ssl_get_new_session(s,0))
            {
            return(-1);
            }
#endif
       p=s->s3->client_random;
        if (ssl_fill_hello_random(s, 0, p, SSL3_RANDOM_SIZE) <= 0)
            return -1;

        if (version == TLS1_2_VERSION)
            {
            version_major = TLS1_2_VERSION_MAJOR;
            version_minor = TLS1_2_VERSION_MINOR;
            }
        else if (tls1_suiteb(s))
            {
            SSLerr(SSL_F_SSL23_CLIENT_HELLO,
                    SSL_R_ONLY_TLS_1_2_ALLOWED_IN_SUITEB_MODE);
            return -1;
            }
        else if (version == TLS1_1_VERSION)
            {
            version_major = TLS1_1_VERSION_MAJOR;
            version_minor = TLS1_1_VERSION_MINOR;
            }
        else if (version == TLS1_VERSION)
            {
            version_major = TLS1_VERSION_MAJOR;
            version_minor = TLS1_VERSION_MINOR;
            }
#ifdef OPENSSL_FIPS
        else if(FIPS_mode())
            {
            SSLerr(SSL_F_SSL23_CLIENT_HELLO,
                    SSL_R_ONLY_TLS_ALLOWED_IN_FIPS_MODE);
            return -1;
            }
#endif
        else if (version == SSL3_VERSION)
            {
            version_major = SSL3_VERSION_MAJOR;
            version_minor = SSL3_VERSION_MINOR;
            }
        else if (version == SSL2_VERSION)
            {
            version_major = SSL2_VERSION_MAJOR;
            version_minor = SSL2_VERSION_MINOR;
            }
        else
            {
            SSLerr(SSL_F_SSL23_CLIENT_HELLO,SSL_R_NO_PROTOCOLS_AVAILABLE);
            return(-1);
            }

        s->client_version = version;

        if (ssl2_compat)
            {
            /* create SSL 2.0 compatible Client Hello */

            /* two byte record header will be written last */
            d = &(buf[2]);
            p = d + 9; /* leave space for message type, version, individual length fields */

            *(d++) = SSL2_MT_CLIENT_HELLO;
            *(d++) = version_major;
            *(d++) = version_minor;

            /* Ciphers supported */
            i=ssl_cipher_list_to_bytes(s,SSL_get_ciphers(s),p,0);
            if (i == 0)
                {
                /* no ciphers */
                SSLerr(SSL_F_SSL23_CLIENT_HELLO,SSL_R_NO_CIPHERS_AVAILABLE);
               return -1;
                }
            s2n(i,d);
            p+=i;

            /* put in the session-id length (zero since there is no reuse) */
#if 0
            s->session->session_id_length=0;
#endif
            s2n(0,d);

            if (s->options & SSL_OP_NETSCAPE_CHALLENGE_BUG)
                ch_len=SSL2_CHALLENGE_LENGTH;
            else
                ch_len=SSL2_MAX_CHALLENGE_LENGTH;

            /* write out sslv2 challenge */
            /* Note that ch_len must be <= SSL3_RANDOM_SIZE (32),
               because it is one of SSL2_MAX_CHALLENGE_LENGTH (32)
               or SSL2_MAX_CHALLENGE_LENGTH (16), but leave the
               check in for futurproofing */
            if (SSL3_RANDOM_SIZE < ch_len)
                i=SSL3_RANDOM_SIZE;
            else
                i=ch_len;
            s2n(i,d);
            memset(&(s->s3->client_random[0]),0,SSL3_RANDOM_SIZE);
            if (RAND_pseudo_bytes(&(s->s3->client_random[SSL3_RANDOM_SIZE-i]),i) <= 0)
                return -1;

            memcpy(p,&(s->s3->client_random[SSL3_RANDOM_SIZE-i]),i);
            p+=i;

            i= p- &(buf[2]);
            buf[0]=((i>>8)&0xff)|0x80;
            buf[1]=(i&0xff);

            /* number of bytes to write */
            s->init_num=i+2;
            s->init_off=0;

            ssl3_finish_mac(s,&(buf[2]),i);
            }
        else
            {
            /* create Client Hello in SSL 3.0/TLS 1.0 format */

            /* do the record header (5 bytes) and handshake message header (4 bytes) last */
            d = p = &(buf[9]);

            *(p++) = version_major;
            *(p++) = version_minor;

            /* Random stuff */
            memcpy(p, s->s3->client_random, SSL3_RANDOM_SIZE);
            p += SSL3_RANDOM_SIZE;

            /* Session ID (zero since there is no reuse) */
            *(p++) = 0;

            /* Ciphers supported (using SSL 3.0/TLS 1.0 format) */
            i=ssl_cipher_list_to_bytes(s,SSL_get_ciphers(s),&(p[2]),ssl3_put_cipher_by_char);
            if (i == 0)
                {
                SSLerr(SSL_F_SSL23_CLIENT_HELLO,SSL_R_NO_CIPHERS_AVAILABLE);
                return -1;
                }
#ifdef OPENSSL_MAX_TLS1_2_CIPHER_LENGTH
            /* Some servers hang if client hello > 256 bytes
             * as hack workaround chop number of supported ciphers
             * to keep it well below this if we use TLS v1.2
             */
            if (TLS1_get_version(s) >= TLS1_2_VERSION
                && i > OPENSSL_MAX_TLS1_2_CIPHER_LENGTH)
                i = OPENSSL_MAX_TLS1_2_CIPHER_LENGTH & ~1;
#endif
            s2n(i,p);
            p+=i;

            /* COMPRESSION */
#ifdef OPENSSL_NO_COMP
            *(p++)=1;
#else
            if (!ssl_allow_compression(s) || !s->ctx->comp_methods)
                j=0;
            else
                j=sk_SSL_COMP_num(s->ctx->comp_methods);
            *(p++)=1+j;
            for (i=0; i<j; i++)
                {
                comp=sk_SSL_COMP_value(s->ctx->comp_methods,i);
                *(p++)=comp->id;
                }
#endif
            *(p++)=0; /* Add the NULL method */

#ifndef OPENSSL_NO_TLSEXT
            /* TLS extensions*/
            if (ssl_prepare_clienthello_tlsext(s) <= 0)
                {
                SSLerr(SSL_F_SSL23_CLIENT_HELLO,SSL_R_CLIENTHELLO_TLSEXT);
                return -1;
                }
            if ((p = ssl_add_clienthello_tlsext(s, p, buf+SSL3_RT_MAX_PLAIN_LENGTH, &al)) == NULL)
                {
                ssl3_send_alert(s,SSL3_AL_FATAL,al);
                SSLerr(SSL_F_SSL23_CLIENT_HELLO,ERR_R_INTERNAL_ERROR);
                return -1;

               }
#endif

            l = p-d;

            /* fill in 4-byte handshake header */
            d=&(buf[5]);
            *(d++)=SSL3_MT_CLIENT_HELLO;
            l2n3(l,d);

            l += 4;

            if (l > SSL3_RT_MAX_PLAIN_LENGTH)
                {
                SSLerr(SSL_F_SSL23_CLIENT_HELLO,ERR_R_INTERNAL_ERROR);
                return -1;
                }

            /* fill in 5-byte record header */
            d=buf;
            *(d++) = SSL3_RT_HANDSHAKE;
            *(d++) = version_major;
            /* Some servers hang if we use long client hellos
             * and a record number > TLS 1.0.
             */
            if (TLS1_get_client_version(s) > TLS1_VERSION)
                *(d++) = 1;
            else
                *(d++) = version_minor;
            s2n((int)l,d);

            /* number of bytes to write */
            s->init_num=p-buf;
            s->init_off=0;

            ssl3_finish_mac(s,&(buf[5]), s->init_num - 5);
            }

        s->state=SSL23_ST_CW_CLNT_HELLO_B;
        s->init_off=0;
        }

    /* SSL3_ST_CW_CLNT_HELLO_B */
    ret = ssl23_write_bytes(s);

    if ((ret >= 2) && s->msg_callback)
        {
        /* Client Hello has been sent; tell msg_callback */

        if (ssl2_compat)
            s->msg_callback(1, SSL2_VERSION, 0, s->init_buf->data+2, ret-2, s, s->msg_callback_arg);
        else
            {
            s->msg_callback(1, version, SSL3_RT_HEADER, s->init_buf->data, 5, s, s->msg_callback_arg);
            s->msg_callback(1, version, SSL3_RT_HANDSHAKE, s->init_buf->data+5, ret-5, s, s->msg_callback_arg);
            }
        }

    return ret;
    }