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Tips and Tricks for dealing with SSL

2 minutes to read Wolf Noble   Howto   Cert Certificate CSR Key Linux OpenSSL SSL WolfspyreLabs

SSL Crib Notes

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

Inspecting

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

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

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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

Remove a passphrase from a private key

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

Mutating and transforming certificates and keys Using OpenSSL

These commands allow you to convert certificates and keys to different formats to make them compatible with specific types of servers or software. For example, you can convert a normal PEM file that would work with Apache to a PFX (PKCS#12) file and use it with Tomcat or IIS. Use our SSL Converter to convert certificates without messing with 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