picoCTF ReadMyCert writeup

This is a medium level cryptography challenge

We are given a .csr file. I looked around on the web trying to find information about what a CSR file is and got myself familiar to it.

I spawned the webshell in picoctf, used wget to download the file and checked what type of file it was.

file readmycert.csr

It was a PEM file. A PEM file is a Base64-encoded container format that stores cryptographic keys, certificates, or other data enclosed between header and footer lines.

Now I knew I had to use OpenSSL to check the file and its contents.

I used the command:

openssl req -in readmycert.csr -noout -text

I found the flag in the contents of that file.

Happy hacking!