DocuSign .NET SDK - Esign DLL - Dealing with changes in Docusign Config Params regarding Error: 'Unexpected PEM type' - .net-core

Question

In Esign version 4.1.1, the VS2019 Docusign project code generators produce this type of config file:
Note that the developer must copy and paste the private key generated on the DocuSign "Quick Start" page into the VS2019 Docusign Project Wizard. The key is converted into a string, with each line in the original key file represented with a carriage return.
Using the private key value in this fashion, inline, with all the other params was very convenient.
This "RSAKey" param value does work with the 4.1.1 version. But does not with the 5.2 version.
In the Esign 5.2 version, we are now in the Asp.Net Core 3.1/.NET 5 style of code, so we now have this configuration file format:
This won't work with Esign 5.2. I surmise the change in 5.2 is this - the Docusign server generates a hash value of the key file, and if the generated hash of the key file submitted by an external client does not match, an "Unknown PEM File" error is sent back. I am trying to highlight the nuance that the first “gate” on the DocuSign server checks the file itself, not the RSA key inside the file.
The ramification, if true, is that we now have to treat the key file with kid gloves. If I wanted to store/retrieve this file from a remote source, I would need to take great care that not a single byte was changed/added/removed. This will require careful testing. As you can see from my sample appsettings.json above, I am forced to add "KeyFilePath" param in order to grab the physical file, which means I must always have it on hand in my project or be able to remotely load it (intact byte-wise) from a remote source. This increases the burden on the developer and maintenance staff considerably.
Ideally, what we need is a way to get that capability to put the key-file-as-a-string back into the config params.
Any ideas appreciated.

Answer 1

One way to solve this is by using https://base64.guru/ .
Using the "File-to-Base64" option allow me to provide this as a string parameter in a normal config file.
Then the C# code to use it looks like this:
var cred = LoadDocusingConfigIntoObject();
byte[] buffer = Convert.FromBase64String(cred.PrivateKey);
this.OAuthToken = docusignClient.RequestJWTUserToken(
cred.IntegrationKey,
cred.ImpersonatedUserId,
cred.AuthServer,
buffer,
1,
scopes
);