Securing Your ASP.NET Core OpenTelemetry /metrics Endpoint: A Comprehensive Guide
Understanding the Problem: Securing Your Observability Data
OpenTelemetry is a powerful tool for collecting and exporting metrics, traces, and logs. In ASP.NET Core applications, these valuable insights are often exposed via the /metrics endpoint, which can be accessed by anyone. This poses a significant security risk, as sensitive data about your application could be compromised.
The Scenario: Unprotected OpenTelemetry Metrics
Let's imagine you have an ASP.NET Core application configured with OpenTelemetry to export metrics to Prometheus. Your Program.cs might look something like this:
using OpenTelemetry.Exporter;
using OpenTelemetry.Metrics;
var builder = WebApplication.CreateBuilder(args);
// Configure OpenTelemetry
builder.Services.AddOpenTelemetry()
.WithMetrics(metrics => metrics
.AddAspNetCoreInstrumentation()
.AddMeter("MyApplication") // Add custom metrics
.AddPrometheusExporter(options => {
options.Port = 9100; // Expose metrics on port 9100
options.ExportIntervalMilliseconds = 5000; // Export every 5 seconds
})
);
var app = builder.Build();
// ... (rest of your application setup)
app.MapGet("/", () => "Hello World!");
app.Run();
This code snippet exposes the /metrics endpoint on port 9100, making it accessible to anyone on the network.
The Solution: Authentication and Authorization
The solution is to secure the /metrics endpoint by implementing authentication and authorization. This ensures that only authorized users or systems can access your sensitive observability data.
Authentication:
- Basic Authentication: Requires users to provide a username and password.
- API Key Authentication: Uses a unique key for identification.
- OAuth 2.0: Allows users to authenticate using a third-party provider like Google or Microsoft.
Authorization:
- Role-based Access Control (RBAC): Limits access based on user roles or permissions.
- Policy-based Authorization: Allows you to define custom authorization policies.
Implementation Examples:
1. API Key Authentication:
// ... (OpenTelemetry configuration)
// Define an API Key for authentication
var apiKey = "your_secret_api_key";
app.MapGet("/metrics", async (HttpContext context) =>
{
// Check if the API Key is provided in the header
if (context.Request.Headers.TryGetValue("Authorization", out var authorizationHeader) &&
authorizationHeader.FirstOrDefault() == {{content}}quot;Bearer {apiKey}")
{
// Authenticated, retrieve and return metrics
var metrics = await context.RequestServices.GetRequiredService<MeterProvider>().GetMeter("MyApplication").GetReader().ReadAllAsync();
return Results.Ok(metrics);
}
else
{
// Unauthorized access
return Results.Unauthorized();
}
});
app.Run();
2. Role-based Access Control (RBAC) with Azure Active Directory (AAD):
// ... (OpenTelemetry configuration)
// Configure AAD authentication
builder.Services.AddAuthentication(AzureADDefaults.AuthenticationScheme)
.AddAzureAD(options => {
options.Instance = "https://login.microsoftonline.com/";
options.Domain = "your-tenant-id.onmicrosoft.com"; // Replace with your tenant ID
options.ClientId = "your-application-id"; // Replace with your application ID
options.CallbackPath = "/signin-oidc"; // Optional, default is /signin-oidc
});
// Authorize access to `/metrics` endpoint for users in a specific role
builder.Services.AddAuthorization(options =>
{
options.AddPolicy("MetricsReader", policy => policy.RequireRole("MetricsReader"));
});
app.UseAuthentication();
app.UseAuthorization();
// Secure the `/metrics` endpoint with the "MetricsReader" role
app.MapGet("/metrics", [Authorize("MetricsReader")] async (HttpContext context) =>
{
// ... (Retrieve and return metrics)
});
app.Run();
Choosing the Right Approach:
The best approach depends on your specific security requirements and application architecture. Consider factors like:
- Complexity: Basic authentication is simple to implement, while OAuth 2.0 is more complex.
- Security: OAuth 2.0 offers stronger security, but it can be more challenging to implement.
- Existing infrastructure: If you already use AAD or other identity providers, consider leveraging them for authentication.
Best Practices:
- Implement a robust security policy: Clearly define who has access to your metrics and under what conditions.
- Minimize the scope of access: Only grant access to the data that is absolutely necessary.
- Monitor access patterns: Regularly review access logs to identify any unusual activity.
- Keep your software updated: Patch vulnerabilities promptly to maintain the integrity of your system.
Resources:
- OpenTelemetry Documentation: https://opentelemetry.io/docs/
- ASP.NET Core Authentication and Authorization: https://learn.microsoft.com/en-us/aspnet/core/security/authentication?view=aspnetcore-7.0
- Azure Active Directory: https://learn.microsoft.com/en-us/azure/active-directory/
By securing your OpenTelemetry /metrics endpoint, you can significantly improve the security of your ASP.NET Core application and safeguard your valuable observability data. Remember, security is an ongoing process, and it's essential to regularly review and update your implementation to stay ahead of evolving threats.
