API Security Fundamentals
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The document outlines various API security vulnerabilities as listed by OWASP in 2023, such as broken object level authorization, broken authentication, and unrestricted resource consumption. It provides an overview of key concepts like OAuth, OpenID Connect, and JWTs, as well as best practices for mitigating risks associated with vulnerable API designs and automating security testing. The author, José Haro Peralta, is a consultant and founder of microapis.io, and shares resources for connecting and learning more about API security.
API Security Fundamentals
- 2. $ whoami • I’m Jose • Consultant, author, instructor • Author of Microservice APIs • Founder of microapis.io @JoseHaroPeralta @microapis
- 3. Connect with me! Twitter: @JoseHaroPeralta GitHub: @abunuwas Newsletter: https://microapis.substack.com LinkedIn: https://www.linkedin.com/in/jose-haro- peralta/
- 4. Agenda OWASP Top 10 API Security Vulnerabilities (2019 and 2023) Open Authorization OpenID Connect Vulnerable API design Vulnerabilities around the API Automating API security testing
- 5. OWASP Top 10 API Vulnerabilities (2023) 1. Broken Object Level Authorization 2. Broken Authentication 3. Broken Object Property Level Authorization 4. Unrestricted Resource Consumption 5. Broken Function Level Authorization 6. Server-Side Request Forgery 7. Security Misconfiguration 8. Lack of Protection from Automated Threats 9. Improper Assets Management 10. Unsafe Consumption of APIs
- 6. Broken Object Level Authorization (BOLA) BOLA happens when attackers get access to information that belongs to other users. This type of attack is commonly done by manipulating resource URIs on the API. For example, if our API has a /blog/{blogId} endpoint, an attacker can play with different IDs to try and get access to different resources (APIs with predictable IDs, such as integers, are more vulnerable).
- 8. Broken Authentication When user authentication is incorrectly implemented, like weak passwords or token signatures, weak token validation (such as lack of signature, expiry date, or audience validation, or allowing to set “alg” to “none”), lack rate-limiting on the login endpoints, and so on.
- 10. Broken Object Property Level Authorization Broken Object Property Level Authorization brings together two different vulnerabilities from the 2019 edition: “Excessive Data Exposure” and “Mass Assignment”. The main idea is allowing a malicious user access object properties that they shouldn't be able to read or change.
- 13. Unrestricted Resource Consumption This vulnerability implies lack of rate-limiting and the inability to detect malicious activity. Malicious users can exploit this vulnerability to launch a DDoS attack, to impact the service provider’s billing, or to perform brute force attacks that bypass authorization (by launching requests with different tokens and so on).
- 15. Broken Function Level Authorization Most APIs and applications have a concept of user groups and functions. Broken Function Level Authorization happens when a malicious user can bypass the constraints of their user group.
- 17. Server-Side Request Forgery Most APIs and applications have a concept of user groups and functions. Broken Some APIs allow users to send URLs from which our service must retrieve a resource (for example to retrieve a user profile photo), or as part of some configuration (for example to configure a webhook). A malicious user may use this feature to include malicious URLs, or to obtain information from the system.
- 18. Security Misconfiguration Security misconfiguration refers to improper configuration at any level of the stack, including infrastructure, configuration management, or application configuration. Some examples are missing TLS, leaking stack trace in error responses, CORS misconfiguration, exposing more HTTP methods than are needed, missing security patches and updates, improperly configured cloud permissions, etc.
- 20. Lack of Protection from Automated Threats Means malicious users can harm the business model through the API. It involves knowledge of the underlying business model behind the API.
- 22. Improper Assets Management This refers to management of API, servers, and resources. When we roll out a new version of the API, it’s important to ensure deprecation of the older versions, especially if the newer versions come with security improvements. It’s also important to keep API documentation up to date, as obsolete documentation makes it difficult to monitor and test the APIs. We also need to ensure that non-production servers aren’t accessible to unauthorized users.
- 24. Unsafe Consumption of APIs Most APIs use third-party integrations, for example for authentication and authorization, for mapping and geolocation, for emailing, and so on. Most of the time, we tend to trust data that comes from third-party applications, and we don’t subject it to validation and sanitisation. This is a mistake, since an attacker can inject malicious code into the third-party application.
- 25. Injection (2019) Injection happens when an attacker injects malicious code through the API, such as SQL/noSQL injection queries that get executed in the database, or command injection statements that get executed in the server. An attacker can leverage any input field in the API to launch an injection attack, including URL query and path parameters, request payloads, header values, field values in a JWT, and so on.
- 26. Injection (2019)
- 27. Authentication vs Authorization Authentication is the process of verifying a user identity, while authorization is the process of verifying that they have access to something.
- 28. Open Authorization (OAuth) OAuth is a standard for access delegation. Resource owner Resource server Client Authorization server
- 33. JSON Web Tokens (JWTs) JSON Web Tokens (JWT, pronounced ‘JOT’) are JSON documents that contain information about a user. We call the properties of a JWT claims. Two types: ID tokens Access tokens
- 35. OpenID Connect (OIDC) OpenID Connect (OIDC) is an open authentication protocol built on top of OAuth that allows users to authenticate on a website using a third-party provider.
- 37. Vulnerable API design Unbound arrays Leaking objects Free-form strings Integer IDs Exposing server-side properties in user input Flexible schemas with unknown properties Too many IDs Improper pagination Unrestricted filters Very flexible schemas with optional parameters
- 38. Vulnerabilities around the API Protect the database Restrict outbound traffic Collect detailed logs and actively monitor them Use a WAF Rate-limit requests Restrict resource consumption Use safe packages and libraries
- 39. Automating API security testing with fencer
- 40. Thanks for listening! Twitter: @JoseHaroPeralta GitHub: @abunuwas Newsletter: https://microapis.substack.com LinkedIn: https://www.linkedin.com/in/jose-haro-peralta/