Creating SSL Certs For google app engine Using ZeroSSL And Let's Encrypt

Question

I'm trying to install ssl certificates created using the ZeroSSL.com page for Let's Encrypt, into the Google Cloud Platform. I followed the FREE SSL Certificate Wizard to do so. The ZeroSSL page generates four files in the process: domain-crt.txt domain-key.txt account-key.txt domain-csr.txt

The google Cloud Platform asks for two files: PEM encoded X.509 public key certificate Unencrypted PEM encoded RSA private key

I've made all the combinations, and followed all suggestion I could find in the web, but I had no success.

Answer 1

I asked this to the zeroSSL people, and Alexander answers me with the solution.

SSL Certificate Wizard generates a longer more secure 4096 bits key by default, but Google only accepts 2048 bits key. So you should generate the new CSR separately first by using CSR Generator at https://zerossl.com/free-ssl/#csr and making sure you select 2048 bits. Then download the produced key and CSR (please note that this is the domain key, not the LE key) and then use the same LE key as you used originally and this new CSR with the SSL Certificate Wizard. At the last Wizard step, you might need to split the domain-crt.txt file in two. The first part between ---BEGIN CERTIFICATE----- and ---END CERTIFICATE----- will go into "Public key certificate" field. Finally, the content of domain-key.txt should be pasted into "Private key" field.