When you need to use a client Certificate Authentication from Java the issues starts even from the beginning with the certificate, since usually it is not in the way you want it.

I recently had to use a PFX certificate for client authentication (maybe another post will be coming) and for that reason I had to convert it to a Java keystore (JKS).

We will create BOTH a truststore and a keystore, because based on your needs you might need one or the other.
The difference between truststore and keystore if you are not aware is(quote from the JSSE ref guide:
TrustManager: Determines whether the remote authentication credentials (and thus the connection) should be trusted.
KeyManager: Determines which authentication credentials to send to the remote host.

Ok that’s enough what you will need is openssl and Java 7 or newer !

First let’s generate a key from the pfx file, this key is later used for p12 keystore.

openssl pkcs12 -in example.pfx -nocerts -out example.key
Enter Import Password:
MAC verified OK
Enter PEM pass phrase:
Verifying — Enter PEM pass phrase:

As shown here you will be asked for the password of the pfx file, later you will be asked to enter a PEM passphase lets for example use 123456 for everything here.

The second commands is almost the same but it is about nokey and a crt this time

openssl pkcs12 -in example.pfx -clcerts -nokeys -out example.crt
Enter Import Password:
MAC verified OK
Now we have a key and and a crt file

Next step is to create a truststore.

keytool -import -file example.crt -alias exampleCA -keystore truststore.jks
Enter keystore password:
Re-enter new password:
Owner: CN=…..
…….
Trust this certificate? [no]: yes
Certificate was added to keystore

As you can see here you just import this crt file into a jks truststore and set some password. For the question do you trust this certificate you say yes, so it is added in the truststore.

We are done if you only need a truststore !

The last step(s) is to create a keystore

openssl pkcs12 -export -in example.crt -inkey example.key -certfile example.crt -name “examplecert” -out keystore.p12
Enter pass phrase for example.key:
Enter Export Password:
Verifying — Enter Export Password:

This p12 keystore is enough in many cases, still if you need a JKS keystore you need one additional command

keytool -importkeystore -srckeystore keystore.p12 -srcstoretype pkcs12 -destkeystore keystore.jks -deststoretype JKS
Importing keystore keystore.p12 to keystore.jks…
Enter destination keystore password:
Re-enter new password:
Enter source keystore password:
Entry for alias examplecert successfully imported.
Import command completed: 1 entries successfully imported, 0 entries failed or cancelled
Warning:
The JKS keystore uses a proprietary format. It is recommended to migrate to PKCS12 which is an industry standard format using “keytool -importkeystore -srckeystore keystore.jks -destkeystore keystore.jks -deststoretype pkcs12”.

Lets verify what we have at the end !

ls
example.pfx example.key keystore.p12
example.crt keystore.jks truststore.jks

That is all folks ! I hope this helps someone :)

There will be a second post how to use this keystore for client side authentication from Java.

Also how to use the truststore if you need to use it.