#openssl

###Install

Install the OpenSSL on Debian based systems

```bash
sudo apt-get install openssl
```

###Commands

Create a private key

```bash
openssl genrsa -out server.key 2048
```

Generate a new private key and certificate signing request

```bash
openssl req -out server.csr -new -newkey rsa:2048 -nodes -keyout server.key
```

Generate a self-signed certificate

```bash
openssl req -x509 -sha256 -nodes -days 365 -newkey rsa:2048 -keyout server.key -out server.crt
```

Generate a certificate signing request (CSR) for an existing private key

```bash
openssl req -out server.csr -key server.key -new
```

Generate a certificate signing request based on an existing certificate

```bash
openssl x509 -x509toreq -in server.crt -out server.csr -signkey server.key
```

Remove a passphrase from a private key

```bash
openssl rsa -in server.pem -out newserver.pem
```

Check a certificate signing request (CSR)

```bash
openssl req -text -noout -verify -in server.csr
```

Check a private key

```bash
openssl rsa -in server.key -check
```

Check a certificate

```bash
openssl x509 -in server.crt -text -noout
openssl x509 -in server.cer -text -noout
```

Check a PKCS#12 file (.pfx or .p12)

```bash
openssl pkcs12 -info -in server.p12
```

Verify a private key matches an certificate

```bash
openssl x509 -noout -modulus -in server.crt | openssl md5
openssl rsa -noout -modulus -in server.key | openssl md5
openssl req -noout -modulus -in server.csr | openssl md5
```

Display all certificates including intermediates

```bash
openssl s_client -connect www.paypal.com:443
```

Convert a DER file (.crt .cer .der) to PEM

```bash
openssl x509 -inform der -in server.cer -out server.pem
```

Convert a PEM file to DER

```bash
openssl x509 -outform der -in server.pem -out server.der
```

Convert a PKCS#12 file (.pfx .p12) containing a private key and certificates to PEM

```bash
openssl pkcs12 -in server.pfx -out server.pem -nodes
```

Convert a PEM certificate file and a private key to PKCS#12 (.pfx .p12)

```bash
openssl pkcs12 -export -out server.pfx -inkey server.key -in server.crt -certfile CACert.crt
```