Year: 2023

Securing the Cloud using multiple-layers of security

Post author By Kanti Kalyan Arumilli
Post date 6 September 2023

This blog post discusses some multi-layered security approach with several MFA based authentications.

In the current world, cyber-security has become the biggest threat! With the rise of hackers, powerful hacking equipment / techniques, even people with bare minimum knowledge of computing can become hackers.

This blog post in a certain way shows techniques to reduce the attack area. In the past, I have written few blog posts regarding cyber-security, this is in continuation of the overall concepts. Here are the blog posts:

How to get alerts for SSH / OpenVPN logins on AWS EC2 or any other debian/ubuntu based servers – ALight Technology And Services Limited (U.K) ALight Technologies USA Inc (alightservices.com)

WireGuard, OpenVPN, Pro Custodibus, TailScale – ALight Technology And Services Limited (U.K) ALight Technologies USA Inc (alightservices.com)

How to easily install OpenVPN and some easy C# code snippets for Process class – ALight Technology And Services Limited (U.K) ALight Technologies USA Inc (alightservices.com)

A method for randomizing VPN security for cloud based workloads – ALight Technology And Services Limited – ALight Technology And Services Limited (U.K) ALight Technologies USA Inc (alightservices.com)

The over-all concept is about using one-time use VPN profiles with time limits on the validity of the connection. i.e Once I create and connect to a VPN server, if anyone ever gets hold of the VPN profile and attempts to connect, the connection should not be allowed and based on organizations policy, breach alert should be sent / any other mitigation action should be performed.

As of now, ALight Technology And Services Limited does not have any other employees but, based on employee permissions and categories, the VPN’s outbound IP address should be segregated i.e x.x.x.x for accessing accessing production environments, y.y.y.y for different set of resources etc…

By doing this type of segregation, it becomes easy to segregate cloud workloads on top of IAM policies in AWS / RBAC in Azure. Moreover the policies can be restricted.

This being the over-all policy, I am going to implement such a implementation soon. In the anouncements blog – ALight Technology And Services Limited: Internal maintenance, server migration (alightservices.com), I have mentioned about moving most AWS cloud workloads into Azure for easier management reasons, because the biggest workload of ALight Technology And Services Limited – WebVeta is going to be hosted on Azure. Because I am attempting Azure Certified Developer Associate certification on September 15th (Thanks Microsoft for the free exam voucher, gratitude). I am planning to get the Server migration completed by September 20th. The planned one-time use VPN profiles implementation + moving developer workload into the cloud by September 25th – i.e After this implementation, the source code, development, visual studio would be in the cloud. My laptop would not have anything critical. I am considering doing a webcast soon and would cover the following topics:

Using YubiKey for logging into laptop – not too useful, because this step can be bypassed and any other laptop can be used.
Setting up one-time use OpenVPN profile secured by a random password with pre-configured validity – One of the critical step.
Biometric Authentication MFA for accessing AWS for getting the OpenVPN profile.
Accessing internal servers i.e RDP for Windows / SSH for Linux and requiring YubiKey – Another critical step – TODO i.e I still need to implement this step. / Alternatively, having a different kind of MFA requirement prior to accessing RDP for Windows or SSH for Linux.

By doing the above set of activities, the following multi-layered security can be implemented:

MFA for accessing VPN profile.
One-time use VPN profile with pre-configured validity.
Random and different password for each profile.
Alerts / Mitigations for any breach / second attempts – sometimes could be false alarm i.e network reasons.
Requiring another layer of MFA for accessing the VPN profile.
Another layer of MFA for accessing servers.

Now, here are some No-No’s:

Don’t use the same type of MFA for all the stages, use different form of MFA or different MFA device for each stage i.e lost phone / stolen one-time codes / keys would not affect. If for example, if you are using same totp generator / normal yubikey / mobile phone for SMS, losing the key or phone can cause a breach. But having different MFA at each stage would minimise the problem.

Irrespective of how many layers of security or how much cyber security measures, implement logging, monitoring, metrics, alerting and do review the logs, monitor metrics for abnormalities. Have a plan of action i.e what to monitor, what are considered normal, what are considered abnormal, how to detect and attack, what needs to be done during an attack for mitigation, what needs to be done for reversing the damage, how to identify the damage, root-cause analysis, future mitigation, communication plan based on what has happened.

I am hoping this blog post and some of my previous blog posts, can help small SME’s and small startups like mine.

–

Mr. Kanti Kalyan Arumilli

Arumilli Kanti Kalyan, Founder & CEO

B.Tech, M.B.A

Founder & CEO, Lead Full-Stack .Net developer

ALight Technology And Services Limited

ALight Technologies USA Inc

Youtube

Facebook

Phone / SMS / WhatsApp on the following 3 numbers:

+91-789-362-6688, +1-480-347-6849, +44-07718-273-964

kantikalyan@gmail.com, kantikalyan@outlook.com, admin@alightservices.com, kantikalyan.arumilli@alightservices.com, KArumilli2020@student.hult.edu, KantiKArumilli@outlook.com and 3 more rarely used email addresses – hardly once or twice a year.

Tags Security

.Net C# Cryptography

BenchmarkDotNet with hash implementation in C#

Post author By Kanti Kalyan Arumilli
Post date 30 August 2023

In earlier blog post:

A discussion of cryptographic hash and non-cryptographic hash implementations using C#

I have discussed about cryptographic and non-cryptographic hashes.

Here is a Github repo associated with this:

https://github.com/ALightTechnologyAndServicesLimited/Benchmark-Hash-Implementations-in-CSharp

For using BenchmarkDotNet:

Add the nuget package to a console application:

dotnet add package BenchmarkDotNet --version 0.13.7

Create a class and use the attributes [GlobalSetup] for any initialization, use the [Benchmark] attribute for the methods. Use [MemoryDiagnoser] for memory related information.

In the Program.cs use:

BenchmarkRunner.Run<BENCHMARK_CLASS>();

The code in the github repo clearly demonstrates the usage.

In the previous blog post I have mentioned about non-cryptographic hashes for general purposes.

Here are the results:

32 bytes data:

I commented some code and evaluated with more data sizes:

25 KB:

5 MB:

25 MB:

Conclusion:

For non-cryptographic 128 bit hashes use Murmur3.

–

Mr. Kanti Kalyan Arumilli

Arumilli Kanti Kalyan, Founder & CEO

B.Tech, M.B.A

Founder & CEO, Lead Full-Stack .Net developer

ALight Technology And Services Limited

ALight Technologies USA Inc

Youtube

Facebook

Phone / SMS / WhatsApp on the following 3 numbers:

+91-789-362-6688, +1-480-347-6849, +44-07718-273-964

Tags .Net, C#, Cryptography

.Net C# Cryptography

A discussion of cryptographic hash and non-cryptographic hash implementations using C#

Post author By Kanti Kalyan Arumilli
Post date 30 August 2023

Hash algorithms take some data and create fixed size representation. The representations can be of various sizes such as 32/64/128/256/512 bytes.

Hash generated are in-general non-reversible i.e you can’t get the original data from hash.

Cryptographic hashes use some high level of cryptography and should be used for sensitive information such as passwords etc…

Non-cryptographic hash implementations can be used for general information.

SHA256, SHA384 and SHA512 are for cryptographic hashes.

The above mentioned SHA implementations are secure but little slower.

Here are some faster hash implementations for non-secure data purposes:

FastHash – Can generate 32/64/128 bit hashes.

var sometext = "SOME TEXT";

ReadOnlySpan<byte> data = new ReadOnlySpan<byte>(Encoding.UTF8.GetBytes(sometext));

var retVal = FastHash.HashGenerator.GenerateHash128(data);

var guid = retVal.AsGuid().ToString();
          OR
Convert.ToBase64String(retVal.AsSpan());

MurmurHash3 – Generates 128 bit hash and faster than FastHash’s 128 bit implementation.

var sometext = "SOME TEXT";

var data = Encoding.UTF8.GetBytes(sometext);

var retVal = murmurHasher.ComputeHash(data);

var guid = Convert.ToBase64String(retVal);

BLAKE2 – Generates 1-64 bytes i.e 8-512 bits hash.

var sometext = "SOME TEXT";

var bytes2 = Blake2Fast.Blake2b.ComputeHash(new ReadOnlySpan<byte>(Encoding.UTF8.GetBytes(sometext)));

var guid = Convert.ToBase64String(bytes2);

For specifying the hash-size in bytes use the overload for ComputeHash.

var bytes2 = Blake2Fast.Blake2b.ComputeHash(new ReadOnlySpan<byte>(<bytes>, Encoding.UTF8.GetBytes(sometext)));

The value of <bytes> can be between 1 and 64.

–

Mr. Kanti Kalyan Arumilli

Arumilli Kanti Kalyan, Founder & CEO

B.Tech, M.B.A

Founder & CEO, Lead Full-Stack .Net developer

ALight Technology And Services Limited

ALight Technologies USA Inc

Youtube

Facebook

Phone / SMS / WhatsApp on the following 3 numbers:

+91-789-362-6688, +1-480-347-6849, +44-07718-273-964

Tags .Net, C#, Cryptography

.Net C# NLog UnitTests

Code Coverage in .Net 2023

Post author By Kanti Kalyan Arumilli
Post date 29 August 2023

In the past, I have written a blog post about code coverage using NUnit, OpenCover and ReportGenerator – https://www.alightservices.com/2022/06/23/code-coverage-in-net/.

OpenCover development has stopped for over 2 years.

This blog post talks about another tool known as Coverlet.

This blog posts has a accompanying Github repo – https://github.com/ALightTechnologyAndServicesLimited/CodeCoverage/

The code has 4 methods regarding DateTime class. And 3 helper methods:

double GetUnixEpoch(DateTime)
DateTime GetDateTimeFromUnixEpoch(double)
long GetYYYMMDD(DateTime)
bool IsLeapYear(int)

There are 9 unit tests for the above mentioned 4 methods.

The batch file – RunCodeCoverage.bat has the commands.

The usage is very simple, add the Coverlet nuget package, install the ReportGenerator tool and run some commands. Navigate to the unittest project.

dotnet add package coverlet.collector

dotnet tool install -g dotnet-reportgenerator-globaltool

The nuget package coverlet.collector needs to be added for every unit test project. The reportgenerator can be installed once.

Then run this command for invoking coverlet:

dotnet test --collect:"XPlat Code Coverage"

This generates a xml file under TestResults/[some-random-guid].

This xml file would be used by reportgenerator for generating HTML report:

reportgenerator.exe "-reports:TestResults**.*.xml" "-targetdir:report"

The above command looks for xml files under TestResults/* folder and generates HTML reports under report folder.

The HTML report looks like this. If there is any code that was not covered under unit test, those can be seen easily. The following screenshots have 100% code coverage, but if there is any code not covered, the code would be shown in red.

–

Mr. Kanti Kalyan Arumilli

Arumilli Kanti Kalyan, Founder & CEO

B.Tech, M.B.A

Founder & CEO, Lead Full-Stack .Net developer

ALight Technology And Services Limited

ALight Technologies USA Inc

Youtube

Facebook

Phone / SMS / WhatsApp on the following 3 numbers:

+91-789-362-6688, +1-480-347-6849, +44-07718-273-964

Tags .Net, C#, NUnit, UnitTests

.Net EntityFramework MariaDB MySQL

MySQL DBFirst using Entity Framework

Post author By Kanti Kalyan Arumilli
Post date 25 August 2023

If there is an existing database and if you need to use Entity Framework, use Database First approach. Have Entity Framework generate the DBContext and the classes.

Install / Update Entity Framework tool:

dotnet tool install --global dotnet-ef
dotnet tool update --global dotnet-ef

Add the following nuget packages:

Microsoft.EntityFrameworkCore
Microsoft.EntityFrameworkCore.Design
Microsoft.EntityFrameworkCore.Relational
Pomelo.EntityFrameworkCore.MySql
Pomelo.EntityFrameworkCore.MySql.Design

Then run the following command:

dotnet ef dbcontext scaffold "Server=<SERVER>;User=<USERNAME>;Password=<PASSWORD>;Database=<DATABASE>;"  "Pomelo.EntityFrameworkCore.MySql"

The EF classes and DBContext gets scaffolded.

–

Mr. Kanti Kalyan Arumilli

Arumilli Kanti Kalyan, Founder & CEO

B.Tech, M.B.A

Founder & CEO, Lead Full-Stack .Net developer

ALight Technology And Services Limited

ALight Technologies USA Inc

Youtube

Facebook

Phone / SMS / WhatsApp on the following 3 numbers:

+91-789-362-6688, +1-480-347-6849, +44-07718-273-964

Tags .Net, EntityFramework, MySQL

.Net C# Cryptography Security

Symmetric encryption using TripleDES in C#

Post author By Kanti Kalyan Arumilli
Post date 15 August 2023

Symmetric encryption is an encryption technique where the same set of keys are used for encryption and decryption. Whereas, Asymmetric encryption uses different keys i.e public key for encryption and associated private key for decryption.

TripleDES is an algorithm for implementing symmetric encryption.

TripleDES uses Key and IV.

public string EncryptTripleDES(string plainText, byte[] Key, byte[] IV)
{
    byte[] encrypted;
    using (TripleDESCryptoServiceProvider tdes = new TripleDESCryptoServiceProvider())
    {
        ICryptoTransform encryptor = tdes.CreateEncryptor(Key, IV);
        using (MemoryStream ms = new MemoryStream())
        {
            using (CryptoStream cs = new CryptoStream(ms, encryptor, CryptoStreamMode.Write))
            {
                using (StreamWriter sw = new StreamWriter(cs))
                    sw.Write(plainText);
                encrypted = ms.ToArray();
            }
        }
    }
    return Convert.ToBase64String(encrypted);
}

The above code snippet is for encryption.

public string DecryptTripleDES(string cipherText, byte[] Key, byte[] IV)
{
    string plaintext = null;
    var cipherBytes = Convert.FromBase64String(cipherText);
    using (TripleDESCryptoServiceProvider tdes = new TripleDESCryptoServiceProvider())
    {
        ICryptoTransform decryptor = tdes.CreateDecryptor(Key, IV);
        using (MemoryStream ms = new MemoryStream(cipherBytes))
        {
            using (CryptoStream cs = new CryptoStream(ms, decryptor, CryptoStreamMode.Read))
            {
                using (StreamReader reader = new StreamReader(cs))
                    plaintext = reader.ReadToEnd();
            }
        }
    }
    return plaintext;
}

The above code snippet is for Decryption.

My open-source tool LightKeysTransfer uses TripleDES and the accompanying source code can be found at:

https://github.com/ALightTechnologyAndServicesLimited/LightKeysTransfer

The encryption/decryption related code can be found at:

https://github.com/ALightTechnologyAndServicesLimited/LightKeysTransfer/blob/main/LightKeysTransfer/LightKeysTransfer/CryptHelper.cs

–

Mr. Kanti Kalyan Arumilli

Arumilli Kanti Kalyan, Founder & CEO

B.Tech, M.B.A

Founder & CEO, Lead Full-Stack .Net developer

ALight Technology And Services Limited

ALight Technologies USA Inc

Youtube

Facebook

Phone / SMS / WhatsApp on the following 3 numbers:

+91-789-362-6688, +1-480-347-6849, +44-07718-273-964

Tags .Net, C#, Security

.Net C# Cryptography Security

An overview of RSA for asymmetric encryption, decryption using C#

Post author By Kanti Kalyan Arumilli
Post date 14 August 2023

The RSACryptoServiceProvider in C# provides way for asymmetric encryption and decryption. The encryption happens using public key. The encrypted data can be decrypted only by the associated private key.

The implementation supports keys of sizes varying from 512 bits to 16,384 bits. The larger the key size, the more secure but slower. Depending on the size of the key, the amount of data that can be encrypted would be different.

The public key can be exported and passed for encrypting data. The private key needs to be properly secured.

My open source project LightKeysTransfer uses RSA for encryption and decryption. CryptHelper.cs has the code implementation.

var rsa = RSACryptoServiceProvider.Create(2048);
var rsa2 = RSACryptoServiceProvider.Create(2048);

// code for exporting the public key
var publicKey = rsa.ToXmlString(false);

// code for importing the public key on a different instance
rsa2.FromXmlString(publicKey);

// code for getting bytes from string, there are several other ways of converting text into bytes
var plainBytes = UTF8Encoding.UTF8.GetBytes("Hello!");

// code for encrypting 
var encryptedBytes = rsa2.Encrypt(plainBytes, RSAEncryptionPadding.OaepSHA512);

// code for decrypting
var decryptedBytes = rsa.Decrypt(encryptedBytes, RSAEncryptionPadding.OaepSHA512);

In a different blog post in the next few days, I would post about TripleDES, I am implementing a combination of TripleDES and RSA for encrypting and decrypting slightly larger data. Larger data cannot be encrypted using RSA!

–

Mr. Kanti Kalyan Arumilli

Arumilli Kanti Kalyan, Founder & CEO

B.Tech, M.B.A

Founder & CEO, Lead Full-Stack .Net developer

ALight Technology And Services Limited

ALight Technologies USA Inc

Youtube

Facebook

Phone / SMS / WhatsApp on the following 3 numbers:

+91-789-362-6688, +1-480-347-6849, +44-07718-273-964

Tags .Net, C#, Cryptography, Security

Security

How to get alerts for SSH / OpenVPN logins on AWS EC2 or any other debian/ubuntu based servers

Post author By Kanti Kalyan Arumilli
Post date 13 August 2023

This blog post is specifically for AWS EC2 but the same concepts can be used in any Ubuntu based environments.

This is part of my personal effort in enhancing the cyber-security of my own startup – ALight Technology And Services Limited and ALight Technologies USA Inc. I am using multi-cloud environment for additional security. I have workloads in Azure, AWS! Azure has more important workloads. I am trying to come up with a plan where if an attacker hacks one of the accounts, the critical workload in Azure should not be accessible. This is pretty much like creating multiple layers of security. In other words this is like multi-MFA accounts security with various multi-factor authentication methods.

At least during locked-down period, the multi-MFA accounts security level would enhance the security. During maintenance window this level of security wouldn’t be possible and I am planning some monitoring, alerts and automatic mitigations if abnormal activity gets detected during maintenance windows based on logs, metrics. And even automatic terminations for any higher abnormal activity. Almost like a self-developed, zero trust system, intrusion detection and prevention system.

Here are several related blog posts:

WireGuard, OpenVPN, Pro Custodibus, TailScale

How to easily install OpenVPN and some easy C# code snippets for Process class

A method for randomizing VPN security for cloud based workloads – ALight Technology And Services Limited

The spy-attackers-toes (I think extremist division of R&AW, spying organization of my own country, India) = terrorist odour can utmost do screenshots but cannot directly access the servers. This is one man’s effort against an army of anonymous spy-hackers. Shame on the bribery/extortion/ransom takers. sugarified word – taking – harsh reality = extortion/ransom, instead they could have opted to asking for help.

In AWS configure a SNS topic to send alerts to emails / SMS to phone. Add the emails and phone numbers, subscribe and validate the emails and phones.

Create a role for use with EC2 instances and give permission for publish to the SNS topic.

When launching the SNS use associate the IAM role with permission for publishing.

Install aws cli.

> sudo apt install awscli

Create a script for example / var/LoginAlert/LoginAlert.sh

#!/bin/bash
aws sns publish --topic-arn <ARN_OF_SNS_TOPIC> --message "User Logged In!" --region <AWS_REGION>
exit 0

Replace the ARN and Region with your own ARN and Region of the SNS topic.

Instead of “aws sns publish”, we can use any other executable such as writing some customcode and writing into some database for audit purposes, send alert via various other methods such as Slack etc… Or may be even a curl request to Slack.

https://api.slack.com/tutorials/tracks/posting-messages-with-curl

Give execute permissions on the script

sudo chmod +x /var/LoginAlert/LoginAlert.sh

Edit the file /etc/profile

sudo nano /etc/profile

Add the following code:

/var/LoginAlert/LoginAlert.sh

Now, reboot and re-login, you should have received an alert.

Now for OpenVPN, we can use the same script. Edit server.conf usually under /etc/openvpn or /etc/openvpn/server. Add the following lines:

client-connect "/var/LoginAlert/LoginAlert.sh"
script-security 2

Now, try connecting to your VPN instance, you should receive an alert.

–

Mr. Kanti Kalyan Arumilli

Arumilli Kanti Kalyan, Founder & CEO

B.Tech, M.B.A

Founder & CEO, Lead Full-Stack .Net developer

ALight Technology And Services Limited

ALight Technologies USA Inc

Youtube

Facebook

Phone / SMS / WhatsApp on the following 3 numbers:

+91-789-362-6688, +1-480-347-6849, +44-07718-273-964

Tags CyberSecurity, Security

AWS Azure Security VPN

WireGuard, OpenVPN, Pro Custodibus, TailScale

Post author By Kanti Kalyan Arumilli
Post date 9 August 2023

In my startup – ALight Technology And Services Limited, I don’t have any employees. I do everything myself. I know .Net web development. These other activities are something new for me.

Most of you know, I have been looking for secure, efficient way of accessing servers hosted in my AWS and Azure accounts. This effort is part of productionizing WebVeta and securing the servers.

I have written some blog articles about OpenVPN in the past and how-to automate changing keys using some C# code at random for higher security.

This blog post is about few other alternatives and some tips.

WireGuard is another free VPN software! But the problem 256-bit key. i.e less secure but high throughput. One possible way is by rotating the key on a timely basis. There is another software known as Pro Custodibus, that helps in rotating keys and managing keys + MFA!

OpenVPN is very highly configurable and can support 2048 bit keys and above.

How to easily install OpenVPN and some easy C# code snippets for Process class

The above blog post talks about how to install and use some C# code for re-generating server and client side keys. The above blog post allows keys + password protection for the ovpn file i.e 2 layers of higher security.

OpenVPN has the following interesting options for further security / monitoring and alerting:

--ipchange cmd
--route-up cmd
--route-pre-down cmd
--ping-exit n
--up cmd
--down cmd
--down-pre
--up-restart
--client-connect
--client-disconnect
--auth-user-pass-verify cmd method
--auth-gen-token [lifetime]
--single-session

Using some of these options and commands, alerts can be generated by either using scripts or programs. I would use C#, but any programming language or even shell scripts can be used.

Using –auth-user-pass-verify 3rd level of security can be added i.e an additional username + password security can be added.

–single-session allows one and only one session, no session re-negotiation – Probably perfect for my scenario.

TailScale is a very nice VPN management software and has a very generous free-tier of upto 100 devices and 3 users. With a little bit of custom programming and using TailScale the security can be increased and can be easily managed. However, one of the biggest problems I saw was registering servers. TailGate displays a URL in plain-text, the URL needs to be entered in browser and authenticated for registering a server in TailGate. If anyone knows the URL and if they authenticate before you, they can try to take-over the server and of-course you can immediately terminate server etc…

I think re-gistering servers should be 2 way i.e

In the website allow copying some random GUID (don’t show the GUID in plain text).
In the server after tailscale up, prompt for the GUID, treat the GUID like password, allow pasting but don’t echo the GUID.
Generate another unique GUID on the server and display.
User copies the server-side GUID and pastes in the website.
Now pair the servers

Even if someone somehow steals the first GUID and pastes in their server, the second GUID generated by their server would be different and can’t be paired.

If someone steals the second guid, their browser-side first guid associated with their account would be different and can’t be paired.

Meanwhile TailScale pairing can be done little securely using my opensource tool – https://github.com/ALightTechnologyAndServicesLimited/LightKeysTransfer – This feature to be implemented, I would make an announcement when the feature gets implemented.

The feature would be very simple, instead of displaying the URL, the URL would be encrypted, use the client-mode part of tool for decrypting, copy and paste in small-sized browser window and approve.

This feature request has been submitted – https://github.com/tailscale/tailscale/issues/8823

–

Mr. Kanti Kalyan Arumilli

Arumilli Kanti Kalyan, Founder & CEO

B.Tech, M.B.A

Founder & CEO, Lead Full-Stack .Net developer

ALight Technology And Services Limited

ALight Technologies USA Inc

Youtube

Facebook

Phone / SMS / WhatsApp on the following 3 numbers:

+91-789-362-6688, +1-480-347-6849, +44-07718-273-964

Tags AWS, Azure, CyberSecurity, Security, VPN

.Net C# Linux Security

How to easily install OpenVPN and some easy C# code snippets for Process class

Post author By Kanti Kalyan Arumilli
Post date 6 August 2023

This blog article is based on the script provided at:

https://raw.githubusercontent.com/Nyr/openvpn-install/master/openvpn-install.sh

This script has been slightly modified for certain reasons mentioned below:

The above script uses pre-defined dh.pem (My version generates a new random 2048 bit dh params)
The above script generates client cert without password (My version mandates password and allows specifying the passwords in a separate file)
The above script generates certificates with 10 years validity (My version generates certificates with 1 day validity i.e because I plan to re-generate certificates often, hmmmm, more like One time use certificates like OTP’s)

I have mentioned in a previous blog post – https://www.alightservices.com/2023/08/03/a-method-for-randomizing-vpn-security-for-cloud-based-workloads-alight-technology-and-services-limited/

I am looking for ways to randomize server-side cert, client ovpn, etc…

This script is part of the effort.

The script is attached here. Later a separate GitHub repo with some demo code would be provided. Then this blog post would be updated.

https://www.alightservices.com/wp-content/uploads/2023/08/openvpn-install.sh_.zip

Download the zip file, unzip, change the extension i.e remove .txt.

Provide execute permissions and execute the script.

> wget https://www.alightservices.com/wp-content/uploads/2023/08/openvpn-install.sh_.zip

> unzip openvpn-install.sh_.zip

> mv openvpn-install.sh.txt openvpn-install.sh

> sudo chmod +x openvpn-install.sh

> echo 'password
password' > infile

> cp infile outfile

> ./openvpn-install.sh

In the above snippets, infile and outfile contains the same password two times on two different lines. Replace the password with what’s necessary or use some tools or utilities for generating password and writing into infile and outfile.

Now the C# part:

Using C# code, it’s very easy to generate random passwords and writing the passwords to infile, outfile.

System.Diagnostics.Process class allows executing shell scripts on Linux. Let’s look at some code sample:

Process process = new();
process.StartInfo.WorkingDirectory = "/path";
process.StartInfo.FileName = "/path/openvpn-install.sh";
process.StartInfo.Arguments = "";
process.EnableRaisingEvents = true;
process.Exited += Process_Exited;
process.ErrorDataReceived += Process_ErrorDataReceived;
process.OutputDataReceived += Process_OutputDataReceived;
process.StartInfo.RedirectStandardInput = true;
process.Start();
.
.
.
process.WaitForExit();


void Process_ErrorDataReceived(object sender, DataReceivedEventArgs e)
{
    // Do whatever is necessary with e.Data;
}

void Process_OutputDataReceived(object sender, DataReceivedEventArgs e)
{
     // Do whatever is necessary with e.Data;
}

void Process_Exited(object? sender, EventArgs e)
{
     // Handle code if necessary
}

In the above code snippet, we are executing a shell script located inside /path directory.

Because we are re-directing StandardInput by setting RedirectStandardInput = true, we can enter different values programatically on a necessary basis.

Or in the above shell script, the interactive prompts can be removed and pre-defined values can be used.

Using the above mentioned script, C# code snippets and by having passwords inside file, it becomes very easy to generate new server and client certificates and re-genrate certificates.

BTW the above mentioned script generates /etc/openvpn/server/server.conf, the following code server-config snippets might be of use, if needed add manually or update the script.

max-clients n
log /var/log/openvpn/openvpn.log
status /var/log/openvpn/status.txt

max-clients limits the maximum number of simultaneous connections.

log – writes log file, the verbosity can be controlled using verb. verb value of 9 means very verbose.

status – a little text file having information about current clients connections.

–

Mr. Kanti Kalyan Arumilli

Arumilli Kanti Kalyan, Founder & CEO

B.Tech, M.B.A

Founder & CEO, Lead Full-Stack .Net developer

ALight Technology And Services Limited

ALight Technologies USA Inc

Youtube

Facebook

Phone / SMS / WhatsApp on the following 3 numbers:

+91-789-362-6688, +1-480-347-6849, +44-07718-273-964

Tags .Net, C#, Linux, Security

Cookie	Duration	Description
cookielawinfo-checkbox-advertisement	1 year	Set by the GDPR Cookie Consent plugin, this cookie is used to record the user consent for the cookies in the "Advertisement" category .
cookielawinfo-checkbox-analytics	11 months	This cookie is set by GDPR Cookie Consent plugin. The cookie is used to store the user consent for the cookies in the category "Analytics".
cookielawinfo-checkbox-functional	11 months	The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category "Functional".
cookielawinfo-checkbox-necessary	11 months	This cookie is set by GDPR Cookie Consent plugin. The cookies is used to store the user consent for the cookies in the category "Necessary".
cookielawinfo-checkbox-others	11 months	This cookie is set by GDPR Cookie Consent plugin. The cookie is used to store the user consent for the cookies in the category "Other.
cookielawinfo-checkbox-performance	11 months	This cookie is set by GDPR Cookie Consent plugin. The cookie is used to store the user consent for the cookies in the category "Performance".
viewed_cookie_policy	11 months	The cookie is set by the GDPR Cookie Consent plugin and is used to store whether or not user has consented to the use of cookies. It does not store any personal data.