[QUERY] How to fetch the private key from Azure Keyvault Secret and convert it to a "java.security.PrivateKey" Java object?

[vijayaraghavan-tvr]

Query/Question
How to fetch the private key from Azure Keyvault Secret and convert it to a "java.security.PrivateKey" Java object? I've tried a sample code as follows, but, it was throwing an exception. Could you please help?

KeyVaultSecret secret = secretClient.getSecret(name, version);
KeyFactory kf = KeyFactory.getInstance("RSA");
PrivateKey privateKey = kf.generatePrivate(new PKCS8EncodedKeySpec(Base64.getDecoder().decode(secret.getValue())));

It threw

Caused by: java.security.spec.InvalidKeySpecException: java.security.InvalidKeyException: unknown version: 3
at java.base/sun.security.rsa.RSAKeyFactory.engineGeneratePrivate(RSAKeyFactory.java:253)
at java.base/java.security.KeyFactory.generatePrivate(KeyFactory.java:389)

Why is this not a Bug or a feature Request?
I just want to understand how to convert the private key value from the Keyvault secret to a "java.security.PrivateKey" Java object. It's not a bug or a feature request.

Setup (please complete the following information if applicable):
I'm using

• Azure Keyvault SDK (v 1.2.22) to fetch the secret.
• Java 17

Information Checklist
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[github-actions]

Thank you for your feedback. Tagging and routing to the team member best able to assist.

[vijayaraghavan-tvr]

Could you please help on the query?

[gataricd]

The problem is that the secret that you get is PFX encoded so you can use something like this:

fun pfxByteArrayToPrivateKey(privateKeyBytes: ByteArray): PrivateKey {
    val keyStore = KeyStore.getInstance("PKCS12")
    keyStore.load(privateKeyBytes.inputStream(), "".toCharArray())
    keyStore.aliases().toList().size
    return keyStore.getKey(keyStore.aliases().toList().first(), "".toCharArray()) as PrivateKey
  }