# OpenSSL Cheat Sheet

## Basics

General commands to analyze a certificate.

Test a TLS connection

```bash
openssl s_client -connect example.net:443
```

Get the certificate from a web endpoint

```bash
openssl s_client -showcerts -connect example.net:443 </dev/null
```

Check whether the private key of a certificate, key and CSR match

```bash
openssl rsa -noout -modulus -in example.key | openssl sha256
openssl x509 -noout -modulus -in example.crt | openssl sha256
openssl req -noout -modulus -in example.csr | openssl sha256
```

## Handling keys

Decrypt a RSA private key

```bash
openssl rsa -in <encrypted_private.key>  -out <decrypted_private.key>
```