Certificates

Source: sslshopper.com

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

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

You can add -nocerts to only output the private key or add -nokeys to only output the certificates.

• 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

Troubleshooting

• Cert tools: https://www.sslshopper.com/ssl-certificate-tools.html

References

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