Fix null check for public key parameter.

[dkocher]

Addendum for #908 as discussed in ¹. Resolves #907.

Footnotes

1. https://github.com/hierynomus/sshj/pull/908/files#r1600044608 ↩

[hierynomus]

Actually the null check is not for the parameter, but was once meant to only ensure that a subsequent call to init would not re-initialize. Need to check what the potential problem is.

[diamondo25]

This has been blocked for ages. Here is my dirty solution for at least 1 init() call:

package com.hierynomus.sshj.userauth.keyprovider;

import lombok.val;

import java.security.PublicKey;

/**
 * This class fixes a bug with init() checking for pubKey != null, which causes publicKey (its argument) to never initialize...
 * <a href="https://github.com/hierynomus/sshj/pull/944">This Github pull request will be merged some day...</a>
 */
public class OpenSSHKeyV1KeyFileHacked extends OpenSSHKeyV1KeyFile {
    private class DummyPublicKey implements PublicKey {
        @Override
        public String getAlgorithm() {
            return "";
        }

        @Override
        public String getFormat() {
            return "";
        }

        @Override
        public byte[] getEncoded() {
            return new byte[0];
        }
    }
    
    @Override
    public void init(String privateKey, String publicKey) {
        // Make sure we only prepare loading the publicKey when its not null, as it'd otherwise throw a NullPointerException later.
        if (publicKey != null) {
            try {
                val field = OpenSSHKeyV1KeyFile.class.getDeclaredField("pubKey");
                field.setAccessible(true);
                field.set(this, new DummyPublicKey());
            } catch (Exception e) {
                throw new RuntimeException("Unable to hack pubKey field", e);
            }
        }
        
        super.init(privateKey, publicKey);
    }
}