Graphql Introspection in Aspnet with Dynamodb

GraphQL introspection in an ASP.NET application that uses Amazon DynamoDB as the backing data store can expose both schema details and data access patterns when not explicitly restricted. Introspection is a core GraphQL feature that allows clients to query the schema structure, types, queries, and mutations. While useful during development, enabling introspection in production can reveal field names, relationships, and resolver behavior, which may aid an attacker in crafting injection or probing attacks.

When GraphQL is implemented in ASP.NET and integrated with DynamoDB through a client or an O/R mapping layer, introspection responses can include type names and field names that map directly to DynamoDB table and attribute conventions. If authorization checks are applied at the resolver level only, introspection may still return fields that a given caller is not permitted to access. This mismatch can expose whether certain DynamoDB-backed resources exist and how they are keyed, supporting enumeration or Low-Level API confusion attacks.

An additional concern specific to DynamoDB is how resolver implementations handle pagination, filter expressions, and key-condition patterns. Introspection may reveal which fields are used as sort keys or global secondary index (GSI) attributes, enabling an attacker to infer access patterns. Combined with insufficient rate limiting or missing property-level authorization, this can facilitate BOLA/IDOR or BFLA-style abuse where attackers iterate through identifiers or escalate privileges by leveraging knowledge of the underlying DynamoDB schema.

To mitigate these risks, disable introspection in production for ASP.NET GraphQL endpoints, apply consistent authorization checks before resolving any DynamoDB-backed field, and validate input against strict type constraints. Tools like middleBrick can detect whether introspection is exposed and whether findings align with compliance frameworks such as OWASP API Top 10 and SOC2, providing prioritized remediation guidance without claiming to fix or block issues directly.

Securing GraphQL with DynamoDB in ASP.NET requires explicit schema design, strict input validation, and defensive authorization. Below are concrete steps and code examples to reduce exposure.

• Disable introspection in production

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddGraphQLServer()
    .AddQueryType<Query>()
    .AddProjections()
    .AddFiltering()
    .AddSorting();

// Disable introspection in production via schema configuration
builder.Services.Configure<GraphQLServerOptions>(options =>
{
    options.EnableMetrics = false;
    options.AllowIntrospection = false; // Disables introspection in production
});

var app = builder.Build();
app.MapGraphQL();
app.Run();

• Apply property-level authorization before DynamoDB access

public class SecureTodoResolver
{
    private readonly IAuthorizationService _authz;
    private readonly IAmazonDynamoDB _ddb;

    public SecureTodoResolver(IAuthorizationService authz, IAmazonDynamoDB ddb)
    {
        _authz = authz;
        _ddb = ddb;
    }

    public async Task<TodoItem> GetTodoAsync(Guid id, ClaimsPrincipal user)
    {
        var request = new GetItemRequest
        {
            TableName = "Todos",
            Key = new Dictionary<string, AttributeValue>
            {
                { "PK", new AttributeValue { S = $"USER#${user.FindFirst(ClaimTypes.NameIdentifier)?.Value}" } },
                { "SK", new AttributeValue { S = $"TODO#{id}" } }
            }
        };

        var response = await _ddb.GetItemAsync(request);
        if (response.Item == null) return null;

        var todo = new TodoItem
        {
            Id = Guid.Parse(response.Item["SK"].S),
            Title = response.Item["Title"].S,
            Done = response.Item["Done"].BOOL ?? false
        };

        var authResult = await _authz.AuthorizeAsync(user, todo, new TodoRequirement(TodoOperations.Read));
        if (!authResult.Succeeded) return null;

        return todo;
    }
}

• Validate and restrict GraphQL input to prevent injection and enumeration

public class TodoInputType : InputObjectGraphType<TodoInput>
{
    public TodoInputType()
    {
        Field<StringGraphType>("title")
            .Validate(c =>
            {
                var value = c.GetArgument<string>("value");
                if (string.IsNullOrWhiteSpace(value) || value.Length > 256)
                    c.ReportError("Title is required and must be 256 characters or less.");
            });
    }
}

public class Query
{
    public async Task<IEnumerable<TodoItem>> ListTodos(
        [Service] IAmazonDynamoDB ddb,
        string statusFilter,
        int limit = 10)
    {
        // Validate input to avoid unexpected DynamoDB behavior
        if (limit < 1 || limit > 50) limit = 10;

        var request = new ScanRequest
        {
            TableName = "Todos",
            FilterExpression = "status = :status",
            ExpressionAttributeValues = new Dictionary<string, AttributeValue>
            {
                { ":status", new AttributeValue { S = statusFilter ?? "OPEN" } }
            },
            Limit = limit
        };

        var response = await ddb.ScanAsync(request);
        return response.Items.Select(i => new TodoItem
        {
            Id = Guid.Parse(i["PK"].S.Split('#')[1]),
            Title = i["Title"].S,
            Done = i["Done"].BOOL ?? false
        });
    }
}

These examples demonstrate disabling introspection, enforcing authorization at the resolver level, and validating inputs before they reach DynamoDB. They align with secure coding practices and help reduce the attack surface when exposing data via GraphQL in ASP.NET.