Servicestack netcoreidentityauthprovider: System.FormatException when using GUID IDs

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Summary

The System.FormatException occurs in a .NET 10 project using ServiceStack v10 when using string-based UserAuthIds (GUIDs) and an authenticated user has no roles or permissions assigned. This exception is thrown during the identity resolution phase, specifically when the NetCoreIdentityAuthProvider attempts to parse the UserAuthId as an integer.

Root Cause

The root cause of this issue is the fallback path in the NetCoreIdentityAuthProvider that attempts to populate ClaimTypes.NameIdentifier by parsing the UserAuthId as an integer when the user session contains no roles. The key factors contributing to this issue are:

  • Using GUIDs as UserAuthId
  • The user having no roles assigned
  • The NetCoreIdentityAuthProvider following a fallback path to populate ClaimTypes.NameIdentifier

Why This Happens in Real Systems

This issue occurs in real systems due to the following reasons:

  • Inconsistent data: Users may not always have roles assigned, leading to the NetCoreIdentityAuthProvider attempting to parse the UserAuthId as an integer
  • Fallback logic: The NetCoreIdentityAuthProvider has a fallback path to populate ClaimTypes.NameIdentifier, which can lead to errors if the UserAuthId is not in the correct format
  • Type mismatches: The UserAuthId is a string (GUID), but the NetCoreIdentityAuthProvider attempts to parse it as an integer, resulting in a System.FormatException

Real-World Impact

The real-world impact of this issue includes:

  • Authentication failures: Users with no roles assigned may not be able to authenticate successfully
  • System crashes: The System.FormatException can cause the system to crash or become unresponsive
  • Security vulnerabilities: Inconsistent authentication logic can lead to security vulnerabilities if not addressed properly

Example or Code

using ServiceStack;
using Microsoft.AspNetCore.Authentication;

public class CustomAuthRepository : AuthRepository
{
    public CustomAuthRepository(IDbConnection dbConnection) : base(dbConnection)
    {
    }

    public override async Task GetUserAuthAsync(string userAuthId)
    {
        // Custom logic to handle GUID UserAuthId
        var userAuth = await base.GetUserAuthAsync(userAuthId);
        if (userAuth != null && string.IsNullOrEmpty(userAuth.Roles))
        {
            // Handle empty roles logic
            userAuth.Claims.Add(new Claim(ClaimTypes.NameIdentifier, userAuthId));
        }
        return userAuth;
    }
}

How Senior Engineers Fix It

Senior engineers can fix this issue by:

  • Implementing custom authentication logic: Creating a custom AuthRepository to handle GUID UserAuthId and empty roles logic
  • Updating the NetCoreIdentityAuthProvider: Modifying the NetCoreIdentityAuthProvider to correctly handle string-based UserAuthId and empty roles
  • Adding error handling: Implementing try-catch blocks to handle System.FormatException and provide a fallback mechanism

Why Juniors Miss It

Junior engineers may miss this issue due to:

  • Lack of understanding of authentication logic: Not fully comprehending the authentication flow and the NetCoreIdentityAuthProvider‘s fallback path
  • Inadequate testing: Not testing the system with various scenarios, including users with no roles assigned
  • Insufficient error handling: Not implementing proper error handling mechanisms to catch and handle System.FormatException