Internal.Cryptography.CryptoThrowHelper.WindowsCryptographicException

One of two problems is going on.

1) The file "exists", but is a symlink. That tends to confuse the underlying system. (The response is to do File.ReadAllBytes and use the byte[] constructor).

2) The file doesn't exist.

To help diagnose #2 you can read Environment.CurrentDirectory to know where "here" is, and use Directory.EnumerateFiles() to see what is present in the directory and why your file doesn't exist.

Of course, if you didn't think you were loading by file, but thought you were loading from a certificate store: Check your configuration and try again... since you're loading from file :).

If you're running in docker, another workaround is doing a copy at startup.

# The copy is done, because wildcard_certificate.pfx is put into the container using docker secrets, which makes it a symlink. 
# Reading a certificate as a symlink is not supported at this moment: https://stackoverflow.com/q/43955181/1608705
# After doing a copy, the copied version is not a symlink anymore.
ENTRYPOINT (IF EXIST "c:\certificates\wildcard_certificate.pfx" (copy c:\certificates\wildcard_certificate.pfx c:\app\wildcard_certificate.pfx)) && dotnet webapplication.dll

My application runs in the "c:\app" folder and I put my "to be copied" certificates in "c:\certificates". At startup the certificate is copied to "c:\app", which my environment variables point to.

version: "3.7"
services:
  webapplication:
    image: ({CONTAINER_REGISTRY})/webapplication:({LABEL})
    environment:
      - ASPNETCORE_URLS=https://+;http://+
      - ASPNETCORE_HTTPS_PORT=443
      - ASPNETCORE_Kestrel__Certificates__Default__Path=wildcard_certificate.pfx
    secrets:
      - source: config_secrets
        target: C:/app/appsettings.json
      - source: wildcard_certificate_pfx
        target: c:\certificates\wildcard_certificate.pfx