# Common OpenSSL Commands

## General OpenSSL Commands

*   Generate a new private key and Certificate Signing Request

    ```
    openssl req -out CSR.csr -new -newkey rsa:2048 -nodes -keyout privateKey.key
    ```
*   Generate a self-signed certificate (see How to Create and Install an Apache Self Signed Certificate for more info)

    ```
    openssl req -x509 -sha256 -nodes -days 365 -newkey rsa:2048 -keyout privateKey.key -out certificate.crt
    ```
*   Generate a certificate signing request (CSR) for an existing private key

    ```
    openssl req -out CSR.csr -key privateKey.key -new
    ```
*   Generate a certificate signing request based on an existing certificate

    ```
    openssl x509 -x509toreq -in certificate.crt -out CSR.csr -signkey privateKey.key
    ```
*   Remove a passphrase from a private key

    ```
    openssl rsa -in privateKey.pem -out newPrivateKey.pem
    ```

## Checking Using OpenSSL

*   Check a Certificate Signing Request (CSR)

    ```
    openssl req -text -noout -verify -in CSR.csr
    ```
*   Check a private key

    ```
    openssl rsa -in privateKey.key -check
    ```
*   Check a certificate

    ```
    openssl x509 -in certificate.crt -text -noout
    ```
*   Check a PKCS#12 file (.pfx or .p12)

    ```
    openssl pkcs12 -info -in keyStore.p12
    ```
*   List the certificates stored in a PKCS12 keystore with Java Keytool

    ```
    keytool -list -v -keystore <path to keystore.pfx> -storepass <password> -storetype PKCS12
    ```

## Debugging Using OpenSSL

*   Check an MD5 hash of the public key to ensure that it matches with what is in a CSR or private key

    ```
    openssl x509 -noout -modulus -in certificate.crt | openssl md5
    openssl rsa -noout -modulus -in privateKey.key | openssl md5
    openssl req -noout -modulus -in CSR.csr | openssl md5
    ```
*   Check an SSL connection. All the certificates (including Intermediates) should be displayed

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

## Converting Using OpenSSL

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

    ```
    openssl x509 -inform der -in certificate.cer -out certificate.pem
    ```
*   Convert a PEM file to DER

    ```
    openssl x509 -outform der -in certificate.pem -out certificate.der
    ```
*   Convert a PKCS#12 file (.pfx .p12) containing a private key and certificates to PEM

    ```
    openssl pkcs12 -in keyStore.pfx -out keyStore.pem -nodes
    ```
*   Convert a PEM certificate file and a private key to PKCS#12 (.pfx .p12)

    ```
    openssl pkcs12 -export -out certificate.pfx -inkey privateKey.key -in certificate.crt -certfile CACert.crt
    ```

## Reference

* [https://www.sslshopper.com/article-most-common-openssl-commands.html](https://www.sslshopper.com/article-most-common-openssl-commands.html)
