Oleksandr Kovalchuk
System Administrator
Ukraine
Summary
👤
Senior🎓
Top SchoolOleksandr Kovalchuk is a seasoned system administrator and former backend developer with 11 years of experience building and securing web applications in Ukraine. After several years developing Python-based back-office systems at Prom.ua, he moved into infrastructure and backend operations at EVO, where he now manages and hardens server-side systems. He contributes to open-source projects focused on security and certificates, notably fixing vulnerabilities and improving domain handling for ACME flows, demonstrating a strong blend of application-level security and production systems knowledge. Comfortable across Python, PostgreSQL and Go, he pairs pragmatic engineering with attention to secure defaults and observability. Colleagues rely on him for hands-on problem solving that bridges development and operations.
11 years of coding experience
4 years of employment as a software developer
Igor Sikorsky Kyiv Polytechnic Institute
English, Ukrainian
Stackoverflow
11reputation
2kreached
3answers
0questions
Github Skills (25)
python10
web-application-security10
acme10
certificate10
go10
sql10
vulnerabilities10
testing9
postgresql9
x5099
documentation9
aiohttp8
pki8
certificate-authority8
redis7
Programming languages (14)
Github contributions (5)
anxolerd/dvpwa
Jul 2017 - Nov 2022
Damn Vulnerable Python Web App
Role in this project:
Back-end Developer & Security Engineer
Back-end Developer & Security EngineerContributions:15 commits, 3 PRs, 9 pushes in 5 years 4 months
Contributions summary:Oleksandr primarily contributed to the back-end of the "Damn Vulnerable Python Web App," focusing on fixing bugs, improving the README documentation, and enhancing the application's security awareness. They addressed a SQL injection vulnerability by adding quotes, refactored code blocks, and added descriptions of vulnerabilities, including session fixation and XSS. The user also implemented logging, updated dependencies, and integrated a "StandWithUkraine" banner.
vulnerablepythonpython-websecuritydamn-vulnerable
smallstep/certificates
Dec 2019 - May 2020
🛡️ A private certificate authority (X.509 & SSH) & ACME server for secure automated certificate management, so you can use TLS everywhere & SSO for SSH.
Role in this project:Back-end Developer
Back-end DeveloperContributions:8 commits, 2 PRs, 6 comments in 4 months
Contributions summary:Oleksandr primarily contributed to the ACME server and certificate management functionalities within the `smallstep/certificates` repository. They focused on improving domain normalization for wildcard domains used in the DNS-01 challenge and implemented a configuration option to force the Subject.CommonName in certificates. Furthermore, they added tests to validate the functionality, including a new test case to ensure correct domain passing to the lookupTxt function. The work involved modifying Go code and tests related to certificate requests and issuance.
sshacme-serversecurecertificate-authoritysecurity-tools
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