.NET Dev Certificate Trust on Linux

When to Use This Skill

Use this skill when:

• Redis TLS connections fail with UntrustedRoot or RemoteCertificateNameMismatch in Aspire
• dotnet dev-certs https --check --trust returns exit code 7
• HTTPS localhost connections fail with certificate validation errors
• After running dotnet dev-certs https --clean and needing to restore trust
• Setting up a new Linux dev machine for .NET HTTPS development
• Aspire dashboard or inter-service gRPC calls fail with TLS errors
• Upgrading from Aspire < 13.1.0 (which didn't use TLS on Redis by default)

The Problem

On Windows and macOS, dotnet dev-certs https --trust handles everything automatically, it generates the certificate, installs it in the user store, and adds it to the system trust store. On Linux, it does almost nothing useful. The command generates the cert and places it in the user store, but:

1. It does not export the certificate to the system CA directory
2. It does not run update-ca-certificates to rebuild the CA bundle
3. It does not add the cert to browser trust stores (NSS/NSSDB)
4. The --trust flag silently succeeds but the cert remains untrusted

This means .NET applications, OpenSSL, curl, and browsers all reject the dev certificate, even though dotnet dev-certs https --check reports it exists.

Why This Surfaces with Aspire 13.1.0+

Prior to Aspire 13.1.0, Redis connections used plaintext. Starting with 13.1.0, Aspire enables TLS on Redis by default. If your dev cert isn't trusted at the system level, Redis connections fail immediately with:

System.Security.Authentication.AuthenticationException:
  The remote certificate is invalid because of errors in the certificate chain: UntrustedRoot

How Linux Certificate Trust Works

Understanding the architecture prevents cargo-cult debugging: