work-club-manager/backend/WorkClub.Api/Middleware/TenantValidationMiddleware.cs

using System.Text.Json;

namespace WorkClub.Api.Middleware;

public class TenantValidationMiddleware
{
    private readonly RequestDelegate _next;

    public TenantValidationMiddleware(RequestDelegate next)
    {
        _next = next;
    }

    public async Task InvokeAsync(HttpContext context)
    {
        if (!context.User.Identity?.IsAuthenticated ?? true)
        {
            await _next(context);
            return;
        }

        if (!context.Request.Headers.TryGetValue("X-Tenant-Id", out var tenantIdHeader) ||
            string.IsNullOrWhiteSpace(tenantIdHeader))
        {
            context.Response.StatusCode = StatusCodes.Status400BadRequest;
            await context.Response.WriteAsJsonAsync(new { error = "X-Tenant-Id header is required" });
            return;
        }

        var requestedTenantId = tenantIdHeader.ToString();
        var clubsClaim = context.User.FindFirst("clubs")?.Value;

        if (string.IsNullOrEmpty(clubsClaim))
        {
            context.Response.StatusCode = StatusCodes.Status403Forbidden;
            await context.Response.WriteAsJsonAsync(new { error = "User does not have clubs claim" });
            return;
        }

        Dictionary<string, string>? clubsDict;
        try
        {
            clubsDict = JsonSerializer.Deserialize<Dictionary<string, string>>(clubsClaim);
        }
        catch (JsonException)
        {
            context.Response.StatusCode = StatusCodes.Status403Forbidden;
            await context.Response.WriteAsJsonAsync(new { error = "Invalid clubs claim format" });
            return;
        }

        if (clubsDict == null || !clubsDict.ContainsKey(requestedTenantId))
        {
            context.Response.StatusCode = StatusCodes.Status403Forbidden;
            await context.Response.WriteAsJsonAsync(new { error = $"User is not a member of tenant {requestedTenantId}" });
            return;
        }

        await _next(context);
    }
}