Publish TeamCity via Sophos XG Firewall

I am running TeamCity product at home for my development work and would like to publish the site via my Sophos XG Firewall. TeamCity runs on the internal domain namespace and to publish it to the Internet, you need to configure it so that it recognises the external domain namespace.

I don't want to make any change on the TeamCity, and luckily Sophos can do it !

Create Business Application Rule on your Sophos Firewall make sure the "Rewrite HTML" is selected as shown below. That's it!

AWS Certified Solutions Architect - Associate

New year, 2018! New challenges!!

Passed the exam and now I am officially AWS Certified Solutions Architect - Associate. Next is Professional #StayTune

Let's Encrypt Certificate Renewal

To renew the certificate that was generated by Let's Encrypt:

1# Go to sslzero.com site
2# Use the same Let's Encrypt Key generated by the site when certificate was originated
3# Get the CSR
4# That's it

Proxy PAC Tester v.2.0

New version of Proxy PAC Tester that supports client IP address to be passed to some of the JS function that checks against client IP address.

#LoveCoding

Active Directory GUID

Active Directory GUID is stored as Byte array (Byte[]).

To convert from Byte[] to string:

string guid = new Guid(Byte[] Object).ToString()

To convert from string to Byte[]:

string guid = <string guid here>

Guid g = Guid.Parse(guid);
Byte[] gba = g.ToByteArray();

string result = "";
foreach(Byte b in gba){ result += @"\" + b.ToString("x2"); }

GUID String to Octect String

If you need to perform LDAP query against Active Directory with objectGUID as the filter, you need to convert the string representation of that GUID to octetstring.

For example, if the objectGUID string value is: ffe17244-4c77-48e7-9db7-69578be7e232
You need to convert it to: \44\72\e1\ff\77\4c\e7\48\9d\b7\69\57\8b\e7\e2\32

so then you can provide the LDAP filter with:
(objectGUID=\44\72\e1\ff\77\4c\e7\48\9d\b7\69\57\8b\e7\e2\32)

To do this by C#, use the following function:

        private string convertStringGuidToOctectString(string guid)
        {
            Guid g = Guid.Parse(guid);
            Byte[] gba = g.ToByteArray();

            string result = "";
            foreach (Byte b in gba)
            {
                result = result + @"\" + b.ToString("x2");
            }

            return result;
        }

Good luck!

Let's Encrypt and Sophos XG Firewall

I am publishing my web server behind the Sophos XG firewall. I need SSL certificate that is free and trusted by most of internet browsers. The answer is Let's Encrypt.

I use this site to help integrate with Let's Encrypt : http://zerossl.com

Steps
#1 Generate CSR from the XG firewall and download the CSR and the private key
#2 Navigate to zerossl.com and paste the CSR content
#3 Follow the instruction to validate your domain - I did DNS option by inserting TXT value
#4 Once validation is successful, the signed public key is ready to be downloaded
#5 Upload the signed key to XG firewall along with the private key that was downloaded on step #1
#6 (optional) if XG firewall does not trust Let's Encrypt CA, add this to the Trusted CA

Done!!