# day31sofAPISecurityTips **Repository Path**: stemmm/day31sofAPISecurityTips ## Basic Information - **Project Name**: day31sofAPISecurityTips - **Description**: This challenge is Inon Shkedy's 31 days API Security Tips. - **Primary Language**: Unknown - **License**: Not specified - **Default Branch**: master - **Homepage**: None - **GVP Project**: No ## Statistics - **Stars**: 0 - **Forks**: 0 - **Created**: 2021-06-03 - **Last Updated**: 2021-06-24 ## Categories & Tags **Categories**: Uncategorized **Tags**: None ## README # 31-days-of-API-Security-Tips ### This challenge is Inon Shkedy's 31 days API Security Tips #### -API TIP: 1/31- *Older APIs versions tend to be more vulnerable and they lack security mechanisms. Leverage the predictable nature of REST APIs to find old versions. Saw a call to `api/v3/login`? Check if `api/v1/login` exists as well. It might be more vulnerable.* -------------------------------------------------------------------------------------------------------------------------- #### -API TIP: 2/31- *Never assume there’s only one way to authenticate to an API! Modern apps have many API endpoints for AuthN: `/api/mobile/login` | `/api/v3/login` | `/api/magic_link`; etc.. Find and test all of them for AuthN problems.* -------------------------------------------------------------------------------------------------------------------------- #### -API TIP:3/31- *Remember how SQL Injections used to be extremely common 5-10 years ago, and you could break into almost every company? BOLA (IDOR) is the new epidemic of API security. As a pentester, if you understand how to exploit it, your glory is guaranteed.* > Learn more about BOLA : [https://medium.com/@inonst/a-deep-dive-on-the-most-critical-api-vulnerability-bola-1342224ec3f2](https://medium.com/@inonst/a-deep-dive-on-the-most-critical-api-vulnerability-bola-1342224ec3f2) -------------------------------------------------------------------------------------------------------------------------- #### -API TIP: 4/31- Testing a Ruby on Rails App & noticed an HTTP parameter containing a URL? Developers sometimes use "Kernel#open" function to access URLs == Game Over. Just send a pipe as the first character and then a shell command (Command Injection by design) > Learn more about the open function: [https://apidock.com/ruby/Kernel/open](https://apidock.com/ruby/Kernel/open) -------------------------------------------------------------------------------------------------------------------------- #### -API TIP:5/31- *Found SSRF? use it for:* * Internal port scanning * Leverage cloud services(like 169.254.169.254) * Use http://webhook.site to reveal IP Address & HTTP Library * Download a very large file (Layer 7 DoS) * Reflective SSRF? disclose local mgmt consoles -------------------------------------------------------------------------------------------------------------------------- #### -API TIP: 6/31- *Mass Assignment is a real thing. Modern frameworks encourage developers to use MA without understanding the security implications. During exploitation, don't guess object's properties names, simply find a GET endpoint that returns all of them.* ![Infographic](https://pbs.twimg.com/media/ENpsW25XYAAjEJE?format=jpg) -------------------------------------------------------------------------------------------------------------------------- #### - API TIP: 7/31 - *A company exposes an API for developers? This is not the same API which is used by mobile / web application. Always test them separately. Don't assume they implement the same security mechanisms.* -------------------------------------------------------------------------------------------------------------------------- #### - API TIP: 8/31 - Pentest for REST API? Give it a chance and check if the API supports SOAP also. Change the content-type to "application/xml", add a simple XML in the request body, and see how the API handles it. > Sometimes the authentication is done in a different component that is shared between REST & SOAP APIs == SOAP API may support JWT > If the API returns stack trace with a DUMPling, it's probably vulnerable** -------------------------------------------------------------------------------------------------------------------------- #### - API TIP: 9/31 - *Pentest for APIs? Trying to find BOLA (IDOR) vulnerabilities? IDs in the HTTP bodies/headers tend to be more vulnerable than IDs in URLs. Try to focus on them first.* -------------------------------------------------------------------------------------------------------------------------- #### -API TIP: 10/31- *Exploiting BFLA (Broken Function Level Authorization)? Leverage the predictable nature of REST to find admin API endpoints! E.g: you saw the following API call `GET /api/v1/users/` Give it a chance and change to `DELETE / POST to create/delete users.`* -------------------------------------------------------------------------------------------------------------------------- #### - API TIP: 11/31 - *The API uses Authorization header? Forget about CSRF! If the authentication mechanism doesn't support cookies, the API is protected against CSRF by design.* -------------------------------------------------------------------------------------------------------------------------- #### -API TIP : 12/31- *Testing for BOLA (IDOR)? Even if the ID is GUID or non-numeric, try to send a numeric value. For example: `/?user_id=111` instead of `user_id=inon@traceable.ai` Sometimes the AuthZ mechanism supports both and it's easier the brute force numbers.* -------------------------------------------------------------------------------------------------------------------------- #### -API TIP: 13/31- *Use Mass Assignment to bypass security mechanisms. E.g., "enter password" mechanism: - `POST /api/reset_pass` requires old password. - `PUT /api/update_user` is vulnerable to MA == can be used to update pass without sending the old one (For CSRF)* -------------------------------------------------------------------------------------------------------------------------- #### - API TIP: 14/31 - *Got stuck during an API pentest? Expand your attack surface! Find sub/sibling domains using http://Virustotal.com & http://Censys.io. Some of these domains might expose the same APIs with different configurations/versions.* -------------------------------------------------------------------------------------------------------------------------- #### -API TIP:15/31- *Static resource==photo,video,.. Web Servers(IIS, Apache) treat static resources differently when it comes to authorization. Even if developers implemented decent authorization, there's a good chance you can access static resources of other users.* -------------------------------------------------------------------------------------------------------------------------- #### -API TIP: 16/31- Even if you use another web proxy, always use Burp in the background. The guys at @PortSwigger are doing a really good job at helping you manage your pentest. Use the “tree view” (free version) feature to see all API endpoints you’ve accessed. -------------------------------------------------------------------------------------------------------------------------- #### -API TIP:17/31- *Mobile Certificate Pinning? Before you start reverse engineering & patching the client app, check for both iOS & Android clients and older versions of them. There's a decent chance that the pinning isn't enabled in one of them. Save time.* -------------------------------------------------------------------------------------------------------------------------- #### -API TIP: 18/31- *Companies & developers tend to put more resources (including security) into the main APIs. Always look for the most niche features that nobody uses to find interesting vulnerabilities. `POST /api/profile/upload_christmas_voice_greeting`* -------------------------------------------------------------------------------------------------------------------------- #### -API TIP:19/31- *Which features do you find tend to be more vulnerable?* *I'll start:* * Organization's user management * Export to CSV/HTML/PDF * Custom views of dashboards * Sub user creation&management * Object sharing (photos, posts,etc) -------------------------------------------------------------------------------------------------------------------------- #### - API TIP:20/31- *Testing AuthN APIs? If you test in production, there's a good chance that AuthN endpoints have anti brute-force protection. Anyhow, DevOps engineers tend to disable rate limiting in non-production environments. Don't forget to test them :)* > A good example of this issue: Facebook Breach (Found by @sehacure) [http://www.anandpraka.sh/2016/03/how-i-could-have-hacked-your-facebook.html](http://www.anandpraka.sh/2016/03/how-i-could-have-hacked-your-facebook.html) -------------------------------------------------------------------------------------------------------------------------- #### -API TIP:21/30- *Got stuck during an API pentest? Expand the attack surface! Use http://archive.com, find old versions of the web-app and explore new API endpoints. Can't use the client? scan the .js files for URLs. Some of them are API endpoints.* -------------------------------------------------------------------------------------------------------------------------- #### -API TIP:22/31- *APIs tend to leak PII by design. BE engineers return raw JSON objects and rely on FE engineers to filter out sensitive data. Found a sensitive resource (e.g, `receipt`)? Find all the EPs that return it: `/download_receipt`,`/export_receipt`, etc..* > Some of the endpoints might leak excessive data that should not be accessible by the user. > This is an example for OWASP Top 10 For APIs - #3 - Excessive Data Exposure -------------------------------------------------------------------------------------------------------------------------- #### -API TIP:23/31- *Found a way to download arbitrary files from a web server? Shift the test from black-box to white-box. Download the source code of the app (DLL files: use IL-spy; Compiled Java - use Luyten) Read the code and find new issues!* -------------------------------------------------------------------------------------------------------------------------- #### -API TIP:24/31- *Got stuck during an API pentest? Expand your attack surface! Remember: developers often disable security mechanisms in non-production environments (qa/staging/etc); Leverage this fact to bypass AuthZ, AuthN, rate limiting & input validation.* -------------------------------------------------------------------------------------------------------------------------- #### -API TIP:25/31- *Found an "export to PDF" feature? There's a good chance the developers use an external library to convert HTML --> PDF behind the scenes. Try to inject HTML elements and cause "Export Injection".* > Learn more about Export Injection: [https://medium.com/@inonst/export-injection-2eebc4f17117](https://medium.com/@inonst/export-injection-2eebc4f17117) -------------------------------------------------------------------------------------------------------------------------- #### -API TIP:26/31- *Looking for BOLA (IDOR) in APIs? got 401/403 errors? AuthZ bypass tricks:* * Wrap ID with an array` {“id”:111}` --> `{“id”:[111]}` * JSON wrap `{“id”:111}` --> `{“id”:{“id”:111}}` * Send ID twice `URL?id=&id=` * Send wildcard `{"user_id":"*"}` > In some cases, the AuthZ mechanism expects a plain string (an ID in this case), and if it receives a JSON instead it won't perform the AuthZ checks. Then, when the input goes to the data fetching component, it might be okay with a JSON instead of string(e.g: it flattens the JSON) -------------------------------------------------------------------------------------------------------------------------- #### -API TIP:27/31- *BE Servers no longer responsible for protecting against XSS. APIs don't return HTML, but JSON instead. If API returns XSS payload? - E.g: `{"name":"Inon}` That's fine! The protection always needs to be on the client side* -------------------------------------------------------------------------------------------------------------------------- #### -API TIP:28/31- *Pentest for .NET apps? Found a param containing file path/name? Developers sometimes use "Path.Combine(path_1,path_2)" to create full path. Path.Combine has weird behavior: if param#2 is absolute path, then param#1 is ignored.* ##### Leverage it to control the path > Learn more: [https://www.praetorian.com/blog/pathcombine-security-issues-in-aspnet-applications](https://www.praetorian.com/blog/pathcombine-security-issues-in-aspnet-applications) -------------------------------------------------------------------------------------------------------------------------- #### -API TIP:29/30- *APIs expose the underlying implementation of the app. Pentesters should leverage this fact to better understand users, roles, resources & correlations between them and find cool vulnerabilities & exploits. Always be curious about the API responses.* -------------------------------------------------------------------------------------------------------------------------- #### -API TIP:30/31- *Got stuck during an API pentest? Expand your attack surface! If the API has mobile clients, download old versions of the APK file to explore old/legacy functionality and discover new API endpoints.* > Remember: companies don’t always implement security mechanisms from day one && DevOps engineers don’t often deprecate old APIs. Leverage these facts to find shadow API endpoints that don’t implement security mechanism (authorization, input filtering & rate limiting) > Download old APK versions of android apps: [https://apkpure.com](https://apkpure.com) -------------------------------------------------------------------------------------------------------------------------- #### -API TIP: 31/31- *Found a `limit` / `page` param? (e.g: `/api/news?limit=100`) It might be vulnerable to Layer 7 DoS. Try to send a long value (e.g: `limit=999999999`) and see what happens :)* -------------------------------------------------------------------------------------------------------------------------- ## Source #### All of this information is taken from twitter of Inon Shkedy ##### Links: * [Inon Shkedy](https://twitter.com/inonshkedy) * [Traceableai](https://twitter.com/traceableai/) * [OWASP API PROJECT](https://github.com/OWASP/API-Security)