proposal-system/api/tests/ProposalSystem.Tests/Middleware/InternalApiKeyMiddlewareTests.cs

using System.Security.Claims;
using FluentAssertions;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Logging;
using NSubstitute;
using ProposalSystem.Api.Middleware;
using Xunit;

namespace ProposalSystem.Tests.Middleware;

/// <summary>
/// QA-C4: InternalApiKeyMiddleware tests.
/// Validates that internal API key authentication works correctly:
/// - Valid key on any path sets system claims and calls next (current behavior)
/// - Invalid key logs warning but still calls next (passes through to JWT)
/// - Missing key header passes through to next middleware (JWT auth)
/// - Empty key in config disables the middleware entirely
///
/// Note: API-C1 audit finding identified that this middleware applies globally
/// and bypasses JWT on ANY route when a valid key is provided. These tests
/// document the current behavior; the fix should scope keys to /internal/ paths.
/// </summary>
public class InternalApiKeyMiddlewareTests
{
    private const string ValidApiKey = "test-internal-api-key-secret-value";

    [Fact(DisplayName = "QA-C4: Valid key sets system claims and calls next")]
    public async Task ValidKey_SetsClaimsAndCallsNext()
    {
        // Arrange
        var (middleware, context, nextCalled) = CreateMiddleware(ValidApiKey);
        context.Request.Headers["X-Internal-Api-Key"] = ValidApiKey;
        context.Request.Path = "/api/proposals/123";

        // Act
        await middleware.InvokeAsync(context);

        // Assert
        nextCalled().Should().BeTrue("next middleware should be called");
        context.User.Identity!.IsAuthenticated.Should().BeTrue();
        context.User.Identity!.AuthenticationType.Should().Be("InternalApiKey");
        context.User.FindFirst(ClaimTypes.NameIdentifier)!.Value.Should().Be("system");
        context.User.FindFirst("sub")!.Value.Should().Be("system-lambda-caller");
        context.User.FindFirst(ClaimTypes.Role)!.Value.Should().Be("admins");
        context.User.FindFirst("cognito:groups")!.Value.Should().Be("admins");
        context.User.FindFirst(ClaimTypes.Email)!.Value.Should().Be("system@proposal-system.internal");
    }

    [Fact(DisplayName = "QA-C4/API-H1: Invalid key returns 401 immediately")]
    public async Task InvalidKey_Returns401()
    {
        // Arrange
        var (middleware, context, nextCalled) = CreateMiddleware(ValidApiKey);
        context.Request.Headers["X-Internal-Api-Key"] = "wrong-key";
        context.Request.Path = "/api/proposals/123";

        // Act
        await middleware.InvokeAsync(context);

        // Assert — API-H1 fix: invalid key short-circuits with 401
        nextCalled().Should().BeFalse("invalid key should not fall through");
        context.Response.StatusCode.Should().Be(401);
    }

    [Fact(DisplayName = "QA-C4: Missing key header passes through to next middleware")]
    public async Task MissingKeyHeader_PassesThrough()
    {
        // Arrange
        var (middleware, context, nextCalled) = CreateMiddleware(ValidApiKey);
        // No X-Internal-Api-Key header set
        context.Request.Path = "/api/proposals";

        // Act
        await middleware.InvokeAsync(context);

        // Assert
        nextCalled().Should().BeTrue("request should pass through to next middleware");
        context.User.Identity!.IsAuthenticated.Should().BeFalse();
    }

    [Fact(DisplayName = "QA-C4: Empty key in config disables API key check entirely")]
    public async Task EmptyKeyInConfig_DisablesMiddleware()
    {
        // Arrange - empty config key means middleware is effectively disabled
        var (middleware, context, nextCalled) = CreateMiddleware("");
        context.Request.Headers["X-Internal-Api-Key"] = "any-key-value";
        context.Request.Path = "/api/proposals/123";

        // Act
        await middleware.InvokeAsync(context);

        // Assert
        nextCalled().Should().BeTrue("next middleware should be called");
        context.User.Identity!.IsAuthenticated.Should().BeFalse(
            "middleware is disabled when config key is empty");
    }

    [Fact(DisplayName = "QA-C4: Null config key disables API key check")]
    public async Task NullConfigKey_DisablesMiddleware()
    {
        // Arrange - null config key (INTERNAL_API_KEY not set)
        var (middleware, context, nextCalled) = CreateMiddleware(null);
        context.Request.Headers["X-Internal-Api-Key"] = "any-key-value";

        // Act
        await middleware.InvokeAsync(context);

        // Assert
        nextCalled().Should().BeTrue();
        context.User.Identity!.IsAuthenticated.Should().BeFalse();
    }

    [Fact(DisplayName = "QA-C4: Empty header value passes through")]
    public async Task EmptyHeaderValue_PassesThrough()
    {
        // Arrange
        var (middleware, context, nextCalled) = CreateMiddleware(ValidApiKey);
        context.Request.Headers["X-Internal-Api-Key"] = "";

        // Act
        await middleware.InvokeAsync(context);

        // Assert
        nextCalled().Should().BeTrue();
        context.User.Identity!.IsAuthenticated.Should().BeFalse();
    }

    [Fact(DisplayName = "QA-C4: Timing-safe comparison used (key differs by one char)")]
    public async Task SimilarKey_Returns401()
    {
        var (middleware, context, nextCalled) = CreateMiddleware(ValidApiKey);
        context.Request.Headers["X-Internal-Api-Key"] = ValidApiKey + "x";
        context.Request.Path = "/api/proposals/123";

        // Act
        await middleware.InvokeAsync(context);

        // Assert — API-H1 fix: invalid key short-circuits with 401
        nextCalled().Should().BeFalse("similar but wrong key should not fall through");
        context.Response.StatusCode.Should().Be(401);
    }

    [Fact(DisplayName = "QA-C4/API-C1: Valid key on allowed path authenticates")]
    public async Task ValidKey_AllowedPath_Authenticates()
    {
        var allowedPaths = new[] { "/api/proposals", "/api/vendor-proposals/1", "/api/generated-pdfs", "/api/files/upload" };

        foreach (var path in allowedPaths)
        {
            var (middleware, context, nextCalled) = CreateMiddleware(ValidApiKey);
            context.Request.Headers["X-Internal-Api-Key"] = ValidApiKey;
            context.Request.Path = path;

            await middleware.InvokeAsync(context);

            context.User.Identity!.IsAuthenticated.Should().BeTrue(
                $"valid key should authenticate on allowed path {path}");
            nextCalled().Should().BeTrue();
        }
    }

    [Fact(DisplayName = "QA-C4/API-C1: Valid key on disallowed path returns 403")]
    public async Task ValidKey_DisallowedPath_Returns403()
    {
        var disallowedPaths = new[] { "/api/admin/dashboard", "/api/users", "/health" };

        foreach (var path in disallowedPaths)
        {
            var (middleware, context, nextCalled) = CreateMiddleware(ValidApiKey);
            context.Request.Headers["X-Internal-Api-Key"] = ValidApiKey;
            context.Request.Path = path;

            await middleware.InvokeAsync(context);

            nextCalled().Should().BeFalse($"valid key on disallowed path {path} should not call next");
            context.Response.StatusCode.Should().Be(403);
        }
    }

    private static (InternalApiKeyMiddleware middleware, HttpContext context, Func<bool> nextCalled) CreateMiddleware(string? configuredKey)
    {
        var wasNextCalled = false;
        RequestDelegate next = _ =>
        {
            wasNextCalled = true;
            return Task.CompletedTask;
        };

        var configData = new Dictionary<string, string?>();
        if (configuredKey != null)
        {
            configData["INTERNAL_API_KEY"] = configuredKey;
        }

        var configuration = new ConfigurationBuilder()
            .AddInMemoryCollection(configData)
            .Build();

        var logger = Substitute.For<ILogger<InternalApiKeyMiddleware>>();

        var middleware = new InternalApiKeyMiddleware(next, configuration, logger);
        var context = new DefaultHttpContext();

        return (middleware, context, () => wasNextCalled);
    }
}