static int ssl_parse_client_hello_v2( ssl_context *ssl )
{
    int ret;
    unsigned int i, j;
    size_t n;
    unsigned int ciph_len, sess_len, chal_len;
    unsigned char *buf, *p;

    SSL_DEBUG_MSG( 2, ( "=> parse client hello v2" ) );

    if( ssl->renegotiation != SSL_INITIAL_HANDSHAKE )
    {
        SSL_DEBUG_MSG( 1, ( "client hello v2 illegal for renegotiation" ) );

        if( ( ret = ssl_send_fatal_handshake_failure( ssl ) ) != 0 )
            return( ret );

        return( POLARSSL_ERR_SSL_BAD_HS_CLIENT_HELLO );
    }

    buf = ssl->in_hdr;

    SSL_DEBUG_BUF( 4, "record header", buf, 5 );

    SSL_DEBUG_MSG( 3, ( "client hello v2, message type: %d",
                   buf[2] ) );
    SSL_DEBUG_MSG( 3, ( "client hello v2, message len.: %d",
                   ( ( buf[0] & 0x7F ) << 8 ) | buf[1] ) );
    SSL_DEBUG_MSG( 3, ( "client hello v2, max. version: [%d:%d]",
                   buf[3], buf[4] ) );

    /*
     * SSLv2 Client Hello
     *
     * Record layer:
     *     0  .   1   message length
     *
     * SSL layer:
     *     2  .   2   message type
     *     3  .   4   protocol version
     */
    if( buf[2] != SSL_HS_CLIENT_HELLO ||
        buf[3] != SSL_MAJOR_VERSION_3 )
    {
        SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
        return( POLARSSL_ERR_SSL_BAD_HS_CLIENT_HELLO );
    }

    n = ( ( buf[0] << 8 ) | buf[1] ) & 0x7FFF;

    if( n < 17 || n > 512 )
    {
        SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
        return( POLARSSL_ERR_SSL_BAD_HS_CLIENT_HELLO );
    }

    ssl->major_ver = SSL_MAJOR_VERSION_3;
    ssl->minor_ver = ( buf[4] <= SSL_MINOR_VERSION_3 )
                     ? buf[4]  : SSL_MINOR_VERSION_3;

    if( ssl->minor_ver < ssl->min_minor_ver )
    {
        SSL_DEBUG_MSG( 1, ( "client only supports ssl smaller than minimum"
                            " [%d:%d] < [%d:%d]", ssl->major_ver, ssl->minor_ver,
                            ssl->min_major_ver, ssl->min_minor_ver ) );

        ssl_send_alert_message( ssl, SSL_ALERT_LEVEL_FATAL,
                                     SSL_ALERT_MSG_PROTOCOL_VERSION );
        return( POLARSSL_ERR_SSL_BAD_HS_PROTOCOL_VERSION );
    }

    ssl->max_major_ver = buf[3];
    ssl->max_minor_ver = buf[4];

    if( ( ret = ssl_fetch_input( ssl, 2 + n ) ) != 0 )
    {
        SSL_DEBUG_RET( 1, "ssl_fetch_input", ret );
        return( ret );
    }

    ssl->handshake->update_checksum( ssl, buf + 2, n );

    buf = ssl->in_msg;
    n = ssl->in_left - 5;

    /*
     *    0  .   1   ciphersuitelist length
     *    2  .   3   session id length
     *    4  .   5   challenge length
     *    6  .  ..   ciphersuitelist
     *   ..  .  ..   session id
     *   ..  .  ..   challenge
     */
    SSL_DEBUG_BUF( 4, "record contents", buf, n );

    ciph_len = ( buf[0] << 8 ) | buf[1];
    sess_len = ( buf[2] << 8 ) | buf[3];
    chal_len = ( buf[4] << 8 ) | buf[5];

    SSL_DEBUG_MSG( 3, ( "ciph_len: %d, sess_len: %d, chal_len: %d",
                   ciph_len, sess_len, chal_len ) );

    /*
     * Make sure each parameter length is valid
     */
    if( ciph_len < 3 || ( ciph_len % 3 ) != 0 )
    {
        SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
        return( POLARSSL_ERR_SSL_BAD_HS_CLIENT_HELLO );
    }

    if( sess_len > 32 )
    {
        SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
        return( POLARSSL_ERR_SSL_BAD_HS_CLIENT_HELLO );
    }

    if( chal_len < 8 || chal_len > 32 )
    {
        SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
        return( POLARSSL_ERR_SSL_BAD_HS_CLIENT_HELLO );
    }

    if( n != 6 + ciph_len + sess_len + chal_len )
    {
        SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
        return( POLARSSL_ERR_SSL_BAD_HS_CLIENT_HELLO );
    }

    SSL_DEBUG_BUF( 3, "client hello, ciphersuitelist",
                   buf + 6, ciph_len );
    SSL_DEBUG_BUF( 3, "client hello, session id",
                   buf + 6 + ciph_len, sess_len );
    SSL_DEBUG_BUF( 3, "client hello, challenge",
                   buf + 6 + ciph_len + sess_len, chal_len );

    p = buf + 6 + ciph_len;
    ssl->session_negotiate->length = sess_len;
    memset( ssl->session_negotiate->id, 0, sizeof( ssl->session_negotiate->id ) );
    memcpy( ssl->session_negotiate->id, p, ssl->session_negotiate->length );

    p += sess_len;
    memset( ssl->handshake->randbytes, 0, 64 );
    memcpy( ssl->handshake->randbytes + 32 - chal_len, p, chal_len );

    /*
     * Check for TLS_EMPTY_RENEGOTIATION_INFO_SCSV
     */
    for( i = 0, p = buf + 6; i < ciph_len; i += 3, p += 3 )
    {
        if( p[0] == 0 && p[1] == 0 && p[2] == SSL_EMPTY_RENEGOTIATION_INFO )
        {
            SSL_DEBUG_MSG( 3, ( "received TLS_EMPTY_RENEGOTIATION_INFO " ) );
            if( ssl->renegotiation == SSL_RENEGOTIATION )
            {
                SSL_DEBUG_MSG( 1, ( "received RENEGOTIATION SCSV during renegotiation" ) );

                if( ( ret = ssl_send_fatal_handshake_failure( ssl ) ) != 0 )
                    return( ret );

                return( POLARSSL_ERR_SSL_BAD_HS_CLIENT_HELLO );
            }
            ssl->secure_renegotiation = SSL_SECURE_RENEGOTIATION;
            break;
        }
    }

    for( i = 0; ssl->ciphersuites[ssl->minor_ver][i] != 0; i++ )
    {
        for( j = 0, p = buf + 6; j < ciph_len; j += 3, p += 3 )
        {
            if( p[0] == 0 &&
                p[1] == 0 &&
                p[2] == ssl->ciphersuites[ssl->minor_ver][i] )
                goto have_ciphersuite_v2;
        }
    }

    SSL_DEBUG_MSG( 1, ( "got no ciphersuites in common" ) );

    return( POLARSSL_ERR_SSL_NO_CIPHER_CHOSEN );

have_ciphersuite_v2:
    ssl->session_negotiate->ciphersuite = ssl->ciphersuites[ssl->minor_ver][i];
    ssl_optimize_checksum( ssl, ssl->session_negotiate->ciphersuite );

    /*
     * SSLv2 Client Hello relevant renegotiation security checks
     */
    if( ssl->secure_renegotiation == SSL_LEGACY_RENEGOTIATION &&
        ssl->allow_legacy_renegotiation == SSL_LEGACY_BREAK_HANDSHAKE )
    {
        SSL_DEBUG_MSG( 1, ( "legacy renegotiation, breaking off handshake" ) );

        if( ( ret = ssl_send_fatal_handshake_failure( ssl ) ) != 0 )
            return( ret );

        return( POLARSSL_ERR_SSL_BAD_HS_CLIENT_HELLO );
    }

    ssl->in_left = 0;
    ssl->state++;

    SSL_DEBUG_MSG( 2, ( "<= parse client hello v2" ) );

    return( 0 );
}
static int ssl_parse_client_hello_v2( ssl_context *ssl )
{
    int ret;
    unsigned int i, j;
    size_t n;
    unsigned int ciph_len, sess_len, chal_len;
    unsigned char *buf, *p;

    SSL_DEBUG_MSG( 2, ( "=> parse client hello v2" ) );

    if( ssl->renegotiation != SSL_INITIAL_HANDSHAKE )
    {
        SSL_DEBUG_MSG( 1, ( "client hello v2 illegal for renegotiation" ) );

        if( ( ret = ssl_send_fatal_handshake_failure( ssl ) ) != 0 )
            return( ret );

        return( POLARSSL_ERR_SSL_BAD_HS_CLIENT_HELLO );
    }

    buf = ssl->in_hdr;

    SSL_DEBUG_BUF( 4, "record header", buf, 5 );

    SSL_DEBUG_MSG( 3, ( "client hello v2, message type: %d",
                   buf[2] ) );
    SSL_DEBUG_MSG( 3, ( "client hello v2, message len.: %d",
                   ( ( buf[0] & 0x7F ) << 8 ) | buf[1] ) );
    SSL_DEBUG_MSG( 3, ( "client hello v2, max. version: [%d:%d]",
                   buf[3], buf[4] ) );

     
    if( buf[2] != SSL_HS_CLIENT_HELLO ||
        buf[3] != SSL_MAJOR_VERSION_3 )
    {
        SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
        return( POLARSSL_ERR_SSL_BAD_HS_CLIENT_HELLO );
    }

    n = ( ( buf[0] << 8 ) | buf[1] ) & 0x7FFF;

    if( n < 17 || n > 512 )
    {
        SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
        return( POLARSSL_ERR_SSL_BAD_HS_CLIENT_HELLO );
    }

    ssl->major_ver = SSL_MAJOR_VERSION_3;
    ssl->minor_ver = ( buf[4] <= SSL_MINOR_VERSION_3 )
                     ? buf[4]  : SSL_MINOR_VERSION_3;

    if( ssl->minor_ver < ssl->min_minor_ver )
    {
        SSL_DEBUG_MSG( 1, ( "client only supports ssl smaller than minimum"
                            " [%d:%d] < [%d:%d]", ssl->major_ver, ssl->minor_ver,
                            ssl->min_major_ver, ssl->min_minor_ver ) );

        ssl_send_alert_message( ssl, SSL_ALERT_LEVEL_FATAL,
                                     SSL_ALERT_MSG_PROTOCOL_VERSION );
        return( POLARSSL_ERR_SSL_BAD_HS_PROTOCOL_VERSION );
    }

    ssl->max_major_ver = buf[3];
    ssl->max_minor_ver = buf[4];

    if( ( ret = ssl_fetch_input( ssl, 2 + n ) ) != 0 )
    {
        SSL_DEBUG_RET( 1, "ssl_fetch_input", ret );
        return( ret );
    }

    ssl->handshake->update_checksum( ssl, buf + 2, n );

    buf = ssl->in_msg;
    n = ssl->in_left - 5;

     
    SSL_DEBUG_BUF( 4, "record contents", buf, n );

    ciph_len = ( buf[0] << 8 ) | buf[1];
    sess_len = ( buf[2] << 8 ) | buf[3];
    chal_len = ( buf[4] << 8 ) | buf[5];

    SSL_DEBUG_MSG( 3, ( "ciph_len: %d, sess_len: %d, chal_len: %d",
                   ciph_len, sess_len, chal_len ) );

     
    if( ciph_len < 3 || ( ciph_len % 3 ) != 0 )
    {
        SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
        return( POLARSSL_ERR_SSL_BAD_HS_CLIENT_HELLO );
    }

    if( sess_len > 32 )
    {
        SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
        return( POLARSSL_ERR_SSL_BAD_HS_CLIENT_HELLO );
    }

    if( chal_len < 8 || chal_len > 32 )
    {
        SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
        return( POLARSSL_ERR_SSL_BAD_HS_CLIENT_HELLO );
    }

    if( n != 6 + ciph_len + sess_len + chal_len )
    {
        SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
        return( POLARSSL_ERR_SSL_BAD_HS_CLIENT_HELLO );
    }

    SSL_DEBUG_BUF( 3, "client hello, ciphersuitelist",
                   buf + 6, ciph_len );
    SSL_DEBUG_BUF( 3, "client hello, session id",
                   buf + 6 + ciph_len, sess_len );
    SSL_DEBUG_BUF( 3, "client hello, challenge",
                   buf + 6 + ciph_len + sess_len, chal_len );

    p = buf + 6 + ciph_len;
    ssl->session_negotiate->length = sess_len;
    memset( ssl->session_negotiate->id, 0, sizeof( ssl->session_negotiate->id ) );
    memcpy( ssl->session_negotiate->id, p, ssl->session_negotiate->length );

    p += sess_len;
    memset( ssl->handshake->randbytes, 0, 64 );
    memcpy( ssl->handshake->randbytes + 32 - chal_len, p, chal_len );

     
    for( i = 0, p = buf + 6; i < ciph_len; i += 3, p += 3 )
    {
        if( p[0] == 0 && p[1] == 0 && p[2] == SSL_EMPTY_RENEGOTIATION_INFO )
        {
            SSL_DEBUG_MSG( 3, ( "received TLS_EMPTY_RENEGOTIATION_INFO " ) );
            if( ssl->renegotiation == SSL_RENEGOTIATION )
            {
                SSL_DEBUG_MSG( 1, ( "received RENEGOTIATION SCSV during renegotiation" ) );

                if( ( ret = ssl_send_fatal_handshake_failure( ssl ) ) != 0 )
                    return( ret );

                return( POLARSSL_ERR_SSL_BAD_HS_CLIENT_HELLO );
            }
            ssl->secure_renegotiation = SSL_SECURE_RENEGOTIATION;
            break;
        }
    }

    for( i = 0; ssl->ciphersuites[ssl->minor_ver][i] != 0; i++ )
    {
        for( j = 0, p = buf + 6; j < ciph_len; j += 3, p += 3 )
        {
            if( p[0] == 0 &&
                p[1] == 0 &&
                p[2] == ssl->ciphersuites[ssl->minor_ver][i] )
                goto have_ciphersuite_v2;
        }
    }

    SSL_DEBUG_MSG( 1, ( "got no ciphersuites in common" ) );

    return( POLARSSL_ERR_SSL_NO_CIPHER_CHOSEN );

have_ciphersuite_v2:
    ssl->session_negotiate->ciphersuite = ssl->ciphersuites[ssl->minor_ver][i];
    ssl_optimize_checksum( ssl, ssl->session_negotiate->ciphersuite );

     
    if( ssl->secure_renegotiation == SSL_LEGACY_RENEGOTIATION &&
        ssl->allow_legacy_renegotiation == SSL_LEGACY_BREAK_HANDSHAKE )
    {
        SSL_DEBUG_MSG( 1, ( "legacy renegotiation, breaking off handshake" ) );

        if( ( ret = ssl_send_fatal_handshake_failure( ssl ) ) != 0 )
            return( ret );

        return( POLARSSL_ERR_SSL_BAD_HS_CLIENT_HELLO );
    }

    ssl->in_left = 0;
    ssl->state++;

    SSL_DEBUG_MSG( 2, ( "<= parse client hello v2" ) );

    return( 0 );
}