# openssl 🔐


### Install

Install the OpenSSL on Debian based systems

```sh
sudo apt-get install openssl
```


### Commands

Create a private key

```sh
openssl genrsa -out server.key 4096
```


Generate a new private key and certificate signing request

```sh
openssl req -out server.csr -new -newkey rsa:4096 -nodes -keyout server.key
```


Generate a self-signed certificate

```sh
openssl req -x509 -sha256 -nodes -days 365 -newkey rsa:4096 -keyout server.key -out server.crt
```


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

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


Generate a certificate signing request based on an existing certificate

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


Remove a passphrase from a private key

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


Parse a list of revoked serial numbers

```sh
openssl crl -inform DER -text -noout -in list.crl
```


Check a certificate signing request (CSR)

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


Check a private key

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


Check a public key

```sh
openssl rsa -inform PEM -pubin -in pub.key -text -noout
openssl pkey -inform PEM -pubin -in pub.key -text -noout
```


Check a certificate

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


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

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


Verify a request certificate (`.csr`)

```sh
openssl req -verify -inform PEM -noout -in intCA.csr.pem
openssl req -verify -inform PEM -noout -in server.csr.pem
```

Verify a signed certificate (`.crt`)

```sh
openssl req -verify -inform PEM -noout -in server.crt.pem 
```

Verify a signed certificate against the CAs

```sh
openssl verify -verbose -no-CApath -CAfile rootCA.crt.pem server.crt.pem
openssl verify -verbose -no-CApath -CAfile intCA.crt.pem server.crt.pem 
```


Verify a private key matches an certificate

```sh
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
```


Verify a certificate against the CA chain

```sh
openssl verify -show_chain -untrusted intermediate-cert.pem  leaf-cert.pem
```

Display all certificates including all parent CAs (offline, fullchain file)

```sh
openssl crl2pkcs7 -nocrl -certfile chain.pem | openssl pkcs7 -print_certs -noout
```


Display all certificates including intermediates (online)

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


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

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


Convert a PEM file to DER

```sh
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

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


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

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


Generate a Diffie Hellman key

```sh
openssl dhparam -out dhparam.pem 2048
```


Encrypt files with rsautl

```sh
openssl rsautl -encrypt -in plaintext.txt -out encrypted.txt -pubin -inkey pubkey.pem
```


Decrypt files with rsautl

```sh
openssl rsautl -decrypt -in encrypted.txt -out plaintext.txt -inkey privkey.pem
```


View when the CRL will next be updated

```sh
openssl crl -in intCA.crl.pem -nextupdate -noout
```

Expert OpenSSL Stuff
==================

Insert selected attributes into a specific section of `openssl.cnf` (only with 'openssl ca', or 'openssl x509 -req'; sorry, nothing for 'openssl req')

```sh
openssl ... -extfile <(printf "subjectAltName=DNS:example.com,DNS:www.example.com") ...
```
as in:
```sh
openssl genrsa -out ca.key 2048
openssl req -new -x509 -days 365 -key ca.key -subj "/C=CN/ST=GD/L=SZ/O=Acme, Inc./CN=Acme Root CA" -out ca.crt
openssl req -newkey rsa:2048 -nodes -keyout server.key -subj "/C=CN/ST=GD/L=SZ/O=Acme, Inc./CN=*.example.com" -out server.csr
openssl x509 -req -extfile <(printf "subjectAltName=DNS:example.com,DNS:www.example.com") -days 365 -in server.csr -CA ca.crt -CAkey ca.key -CAcreateserial -out server.crt
```

Be not influenced by default settings provided by `/usr/lib/ssl/openssl.cnf`

```sh
env OPENSSL_CONF=/dev/null openssl -config your-config ...
```

Strip "/-BEGIN CERTIFICATE-/" (caused by `-text`) from PEM file using `sed` before using as pure PEM

```sh
  openssl s_client -connect ${CERT} 2>/dev/null |\
  sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' |\
  openssl x509 -noout -subject -dates