Virtual Box Guest connect to Windows Host

You have a Windows Host running Virtual Box, and a CentOS 7 Guest as virtual machine.
Guest needs to connect to some service in Host. As an example, Host has an Apache web server running in port 80.


First, you have to determine the gateway used by the Guest.

enp0s3 is my "host only" network interface in VirtualBox.
In my case, it's 192.168.56.1. This is the IP the Guest knows as Host so, if you call for port 80, you should get Apache home page.

As you see Guest is not able to connecto to Host. In order to allow that, you need to configure Host firewall, in my case, Windows 10.
You can disable firewall for private networks as follow, but this is not a good solition due security concerns.



The proper solution is to configure a firewall rule for this port in the private network.

Connect Apache Web Server and Apache Tomcat

We have Apache Web Server (httpd) as front-end and Apache Tomcat as back-end.
This solution is based on mod_proxy and AJP connector.

Apache web server config

You have to configure mod_proxy in apache httpd.
I added the following conf file in conf.d directory:

<VirtualHost 172.22.215.219:80>
    Servername sisifo.domain1
 
    RewriteEngine on
    RewriteCond %{SERVER_PORT} !^443$
    RewriteRule ^/(.*) https://%{HTTP_HOST}/$1 [NC,R=301,L]
 
 
    LogLevel info
    ErrorLog  /var/log/httpd/sisifo.domain1_error_log
    CustomLog /var/log/httpd/sisifo.domain1_access_log combined
</VirtualHost>
 
 
 
<VirtualHost 172.22.215.219:443>
    Servername sisifo.domain1
 
    SSLEngine on
    SSLProtocol all -SSLv2 -SSLv3
    SSLCipherSuite ECDHE-RSA-AES128-GCM-SHA384:ECDHE-RSA-AES128-GCM-SHA128:DHE-RSA-AES128-GCM-SHA384:DHE-RSA-AES128-GCM-SHA128:ECDHE-RSA-AES128-SHA384:ECDHE-RSA-AES128-SHA128:ECDHE-RSA-AES128-SHA:ECDHE-RSA-AES128-SHA:DHE-RSA-AES128-SHA128:DHE-RSA-AES128-SHA128:DHE-RSA-AES128-SHA:DHE-RSA-AES128-SHA:ECDHE-RSA-DES-CBC3-SHA:EDH-RSA-DES-CBC3-SHA:AES128-GCM-SHA384:AES128-GCM-SHA128:AES128-SHA128:AES128-SHA128:AES128-SHA:AES128-SHA:DES-CBC3-SHA:HIGH:!aNULL:!eNULL:!EXPORT:!DES:!MD5:!PSK:!RC4
 
    SSLCertificateKeyFile /etc/pki/tls/private/localhost.key
    SSLCertificateFile /etc/pki/tls/certs/localhost.crt
    #SSLCertificateChainFile /etc/pki/tls/certs/server-chain.crt
    #SSLCACertificatePath /etc/httpd/certs/ca
 
    <Location "/">
    Order Deny,Allow
                    Deny from all
                    Allow from all
                    #Allow from 10.224.0.0/12
    </Location>
 
    ##########
 
    ProxyRequests Off
    ProxyPassMatch ^/(.*)$ balancer://tomcat_cluster/$1$2 stickysession=JSESSIONID|jsessionid
 
    <Proxy balancer://tomcat_cluster>
      BalancerMember ajp://[TOMCAT1]:8009 loadfactor=1 route=jvmTomcat1 ping=1
   BalancerMember ajp://[TOMCAT2]:8009 loadfactor=1 route=jvmTomcat2 ping=1
       
      ProxySet lbmethod=byrequests
      ProxySet nofailover=off
      ProxySet timeout=300
    </Proxy>
     
    ##########
 
    LogLevel info  
    ErrorLog /var/log/httpd/sisifo.domain1_ssl_error_log
    CustomLog /var/log/httpd/sisifo.domain1_ssl_access_log combined
</VirtualHost>

Tomcat config

You have to edit $TOMCAT_HOM/config/server.xml of each tomcat instance and set an unique value for  jvmRoute attribute. This attribute is in Engine tag.

<Engine defaultHost="localhost" name="Catalina" jvmRoute="jvmTomcat1">

ORA-00942 Table or View Does Not Exist - Identify target table

During the installation of a third party application which uses Oracle Database, I found the following error in server log:

ORA-00942: table or view does not exist
00942. 00000 -  "table or view does not exist"

The error was clear, the application was trying to execute an SQL statement against a table that was not in database, or the user did not have permissions. But, which table or view was that?

In order to discover the SQL the client was invoking I found this post: https://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:2975793633621#284628100346267414. In my post I´ll just refactor it in order to easy understanding.

The idea behind of this is to register a trigger for server error 942, obtain  context information and the sql being executed, and save all this info in other table. The complete code is as follow:

-- Table to store errors
create table ERROR942 (id number, 
    "time" timestamp,
    "event" varchar(100), 
    "user" varchar(100),
    "server_error" varchar2(4000),
    "sql" varchar2(4000) );

-- Sequence to generate the table id
create sequence SEQ_ERROR942;


-- Trigger to insert errors in table
create or replace trigger TGR_SERVER942
after servererror on database
declare
   l_sql_text ora_name_list_t;
   full_sql varchar2(4000);
   l_n number;
begin
    if ( is_servererror(942) )
    then        
        full_sql := '';
        l_n := ora_sql_txt( l_sql_text );
        for i in 1 .. l_n
        loop
           full_sql := full_sql || l_sql_text(i);
        end loop;
        
         insert into ERROR942 values (SEQ_ERROR942.nextval, current_date, ora_sysevent, ora_login_user,  ora_server_error(1), full_sql);
    end if;
end;

commit;

The main aspects here are:

• We create ERROR942 table in order to store all errors
• We create SEQ_ERROR942 in order to generate the previous table ids
• We create TGR_SERVER942 trigger in order to capture server errors and store then in the table. 

You can test the solution as follow:

select * from UNEXIST_TABLE;

select * ERROR942;

Apache httpd - Windows 10

In order to disable port 80 in windows 10 and to allow Apache Web Server start, execute de following command as administrator:

net stop branchcache

Create timestamp certificate

This procedure is explained with KeystoreExplorer (http://keystore-explorer.org/)

1 - Create the CA

The important thing is to set the following extensions:

• Basic Constraints: Subject is a CA
• Key Usage: Certificate Signing

2 - Create the timestamp certificate

The important thing is to set the following extensions:

• Extended Key Usage: Time Stamping [Critial extension]