Security Knowledge Framework
  • Introduction
  • Auth Bypass
    • Python - Auth Bypass
    • NodeJS - Auth Bypass
  • Auth Bypass - 1
    • Python - Auth Bypass - 1
    • NodeJS - Auth Bypass - 1
    • Java - Auth Bypass - 1
  • Auth Bypass - 2
    • Python - Auth Bypass - 2
    • NodeJS - Auth Bypass - 2
    • Java - Auth Bypass - 2
  • Auth-bypass - 3
    • Python - Auth-bypass - 3
    • NodeJS - Auth-bypass - 3
    • Java - Auth-bypass - 3
  • Auth-bypass - Simple
    • Python - Auth-bypass - Simple
    • NodeJS - Auth-bypass - Simple
    • Java - Auth-bypass - Simple
  • Client Side Restriction Bypass
    • Python - Client Side Restriction Bypass
    • NodeJS - Client Side Restriction Bypass
    • Java - Client Side Restriction Bypass
  • Client Side Restriction Bypass - Harder
    • Python - Client Side Restriction Bypass - Harder
    • NodeJS - Client Side Restriction Bypass - Harder
    • Java - Client Side Restriction Bypass - Harder
  • Client Side Template Injection (CSTI)
    • Python - Client Side Template Injection (CSTI)
    • NodeJS - Client Side Template Injection (CSTI)
    • Java - Client Side Template Injection (CSTI)
  • Command Injection (CMD)
    • Python - Command Injection (CMD)
    • NodeJS - Command Injection (CMD)
    • Java - Command Injection (CMD)
  • Command Injection 2 (CMD-2)
    • Python - Command Injection 2 (CMD-2)
    • NodeJS - Command Injection 2 (CMD-2)
    • Java - Command Injection 2 (CMD-2)
  • Command Injection 3 (CMD-3)
    • Python - Command Injection 3 (CMD-3)
    • Java - Command Injection 3 (CMD-3)
  • Command Injection 4 (CMD-4)
    • Python - Command Injection 4 (CMD-4)
    • NodeJS - Command Injection 4 (CMD-4)
    • Java - Command Injection 4 (CMD-4)
  • Command Injection Blind (CMD-Blind)
    • Python - Command Injection Blind (CMD-Blind)
    • NodeJS - Command Injection Blind (CMD-Blind)
    • Java - Command Injection Blind (CMD-Blind)
  • Content-Security-Policy (CSP)
    • Python - Content-Security-Policy (CSP)
    • NodeJS - Content-Security-Policy (CSP)
    • Java - Content-Security-Policy (CSP)
  • CORS exploitation
    • Python - CORS exploitation
    • Java - CORS exploitation
  • Credentials Guessing
    • Python - Credentials Guessing
    • NodeJS - Credentials Guessing
    • Java - Credentials Guessing
  • Credentials Guessing - 2
    • Python - Credentials Guessing - 2
    • NodeJS - Credentials Guessing - 2
    • Java - Credentials Guessing - 2
  • Cross Site Scripting (XSS)
    • Python - XSS
    • NodeJS - XSS
    • Java - XSS
  • Cross Site Scripting - Attribute (XSS-Attribute)
    • Python - XSS-Attribute
    • NodeJS - XSS-Attribute
  • Cross Site Scripting - href (XSS-href)
    • Python - XSS-href
    • NodeJS - XSS-href
    • Java - XSS-href
  • Cross Site Scripting - DOM (XSS-DOM)
    • Python - XSS-DOM
    • NodeJS - XSS-DOM
    • Java - XSS-DOM
  • Cross Site Scripting - DOM-2 (XSS-DOM-2)
    • Python - XSS-DOM-2
    • NodeJS - XSS-DOM-2
    • Java - XSS-DOM-2
  • Cross Site Scripting - Stored (XSS-Stored)
    • Java - XSS-Stored
  • CSRF
    • Python - CSRF
    • NodeJS - CSRF
    • Java - CSRF
  • CSRF - Samesite
    • Python - CSRF-SameSite
    • NodeJS - CSRF-SameSite
    • Java - CSRF-SameSite
  • CSRF - Weak
    • Python - CSRF-Weak
    • NodeJS - CSRF-Weak
    • Java - CSRF-Weak
  • CSS Injection (CSSI)
    • Python - CSS Injection (CSSI)
    • NodeJS - CSS Injection (CSSI)
    • Java - CSS Injection (CSSI)
  • Deserialisation Java (DES-Java)
    • Java - Deserialisation Java (DES-Java)
  • Deserialisation Yaml (DES-Yaml)
    • Python - Deserialisation Yaml (DES-Yaml)
  • Deserialisation Pickle (DES-Pickle)
    • Python - Deserialisation Pickle (DES-Pickle)
  • Deserialisation Pickle 2 (DES-Pickle-2)
    • Python - Deserialisation Pickle 2 (DES-Pickle-2)
  • DoS Regex
    • Python - DoS Regex
    • NodeJS - DoS Regex
    • Java - DoS Regex
  • File upload
    • Python - File-Upload
    • NodeJS - File-Upload
    • Java - File-Upload
  • Formula Injection
    • Python - Formula Injection
    • NodeJS - Formula Injection
    • Java - Formula Injection
  • GraphQL DOS
    • Python - GraphQL DOS
  • GraphQL IDOR
    • Python - GraphQL IDOR
    • NodeJS - GraphQL IDOR
    • Java - GraphQL IDOR
  • GraphQL Injections
    • Python - GraphQL Injections
    • NodeJS - GraphQL Injections
    • Java - GraphQL Injections
  • GraphQL Introspection
    • Python - GraphQL Introspection
    • NodeJS - GraphQL Introspection
    • Java - GraphQL Introspection
  • GraphQL Mutations
    • Python - GraphQL Mutations
    • NodeJS - GraphQL Mutations
    • Java - GraphQL Mutations
  • Host Header Injection (Authentication Bypass)
    • Python - HttpOnly Session Hijacking XSS
  • HttpOnly Session Hijacking XSS
    • Python - HttpOnly Session Hijacking XSS
    • NodeJS - HttpOnly Session Hijacking XSS
    • Java - HttpOnly Session Hijacking XSS
  • Information Leakeage in Comments
    • Python - Information Leakeage in Comments
    • NodeJS - Information Leakeage in Comments
    • Java - Information Leakeage in Comments
  • Information Leakeage in Metadata
    • Python - Information Leakeage in Metadata
    • NodeJS - Information Leakeage in Metadata
    • Java - Information Leakeage in Metadata
  • Insecure Direct Object References (IDOR)
    • Python - Insecure Direct Object References (IDOR)
    • NodeJS - Insecure Direct Object References (IDOR)
    • Java - Insecure Direct Object References (IDOR)
  • JWT Null
    • Python - JWT Null
    • NodeJS - JWT Null
    • Java - JWT Null
  • JWT Secret
    • Python - JWT Secret
    • NodeJS - JWT Secret
    • Java - JWT Secret
  • Ldap Injection
    • Python - Ldap Injection
    • NodeJS - Ldap Injection
    • Java - Ldap Injection
  • Ldap Injection - harder
    • Python - Ldap Injection - harder
    • NodeJS - Ldap Injection - harder
    • Java - Ldap Injection - harder
  • Local File Inclusion 1 (LFI-1)
    • Python - Local File Inclusion 1 (LFI-1)
    • NodeJS - Local File Inclusion 1 (LFI-1)
    • Java - Local File Inclusion 1 (LFI-1)
  • Local File Inclusion 2 (LFI-2)
    • Python - Local File Inclusion 2 (LFI-2)
    • NodeJS - Local File Inclusion 2 (LFI-2)
    • Java - Local File Inclusion 2 (LFI-2)
  • Local File Inclusion 3 (LFI-3)
    • Python - Local File Inclusion 3 (LFI-3)
    • NodeJS - Local File Inclusion 3 (LFI-3)
    • Java - Local File Inclusion 3 (LFI-3)
  • Parameter Binding
    • Ruby - Parameter Binding
    • NodeJS - Parameter Binding
    • Java - Parameter Binding
  • Prototype Pollution
    • NodeJS - Prototype Pollution
  • Race Condition
    • Python - Race Condition
    • NodeJS - Race Condition
    • Java - Race Condition
  • Race Condition File-Write
    • Python - Race Condition File-Write
    • NodeJS - Race Condition File-Write
    • Java - Race Condition File-Write
  • Ratelimiting (Brute-force login)
    • Python - Ratelimiting
    • NodeJS - Ratelimiting
    • Java - Ratelimiting
  • Remote File Inclusion (RFI)
    • Python - Remote File Inclusion (RFI)
    • NodeJS - Remote File Inclusion (RFI)
    • Java - Remote File Inclusion (RFI)
  • Right To Left Override (RTLO)
    • Python - Right To Left Override (RTLO)
    • NodeJS - Right To Left Override (RTLO)
    • Java - Right To Left Override (RTLO)
  • Server Side Request Forgery (SSRF)
    • Python - Server Side Request Forgery (SSRF)
    • NodeJS - Server Side Request Forgery (SSRF)
  • Server Side Template Injection (SSTI)
    • Python - Server Side Template Injection (SSTI)
    • Java - Server Side Template Injection (SSTI)
  • Session Hijacking XSS
  • Session Puzzling
    • Python - Session Puzzling
    • NodeJS - Session Puzzling
    • Java - Session Puzzling
  • Session Management 1
    • Python - Session Management 1
  • SQLI (Union)
    • Python - SQLI (Union)
    • NodeJS - SQLI (Union)
    • Java - SQLI (Union)
  • SQLI Login Bypass
    • Python - Login Bypass
  • SQLI (Like)
    • Python - SQLI (Like)
    • NodeJS - SQLI (Like)
    • Java - SQLI (Like)
  • SQLI (Blind)
    • Python - SQLI (Blind)
    • NodeJS - SQLI (Blind)
    • Java - SQLI (Blind)
  • TLS Downgrade
    • Python - TLS Downgrade
  • Untrusted Sources (XSSI)
    • Python - Untrusted Sources (XSSI)
    • NodeJS - Untrusted Sources (XSSI)
    • Java - Untrusted Sources (XSSI)
  • URL Redirection
    • Python - URL Redirection
    • NodeJS - URL Redirection
    • Java - URL Redirection
  • URL Redirection - Harder
    • Python - URL Redirection - Harder
    • NodeJS - URL Redirection - Harder
    • Java - URL Redirection - Harder
  • URL Redirection - Harder-2
    • Python - URL Redirection - Harder-2
    • NodeJS - URL Redirection - Harder-2
    • Java - URL Redirection - Harder-2
  • WebSocket Message Manipulation
    • Python - WebSocket Message Manipulation
  • XML External Entity (XXE)
    • Python - XXE
    • NodeJS - XXE
    • Java - XXE
  • Exposed docker daemon
    • Python - Exposed docker daemon
  • Insecure Random
    • Python - Insecure Random
  • template item
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On this page
  • Running the app on Docker
  • Reconnaissance
  • Step1
  • Exploitation
  • Step 1
  • Step 2
  • Step 2
  • Additional Resources

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  1. JWT Null

NodeJS - JWT Null

PreviousPython - JWT NullNextJava - JWT Null

Last updated 2 years ago

Was this helpful?

Running the app on Docker

$ sudo docker pull blabla1337/owasp-skf-lab:js-jwt-null
$ sudo docker run -ti -p 127.0.0.1:5000:5000 blabla1337/owasp-skf-lab:js-jwt-null

Now that the app is running let's go hacking!

Reconnaissance

Step1

The application let us authenticate an user and see its privileges.

First thing we need to do know is to do more investigation on the requests that are being made. We do this by setting up our intercepting proxy so we can gain more understanding of the application under test.

After we set up our favourite intercepting proxy we are going to look at the traffic between the server and the front-end. Enter the credentials: username: user | password:user

The first thing to notice is after sucessful logon, the response contains an access token.

The image above shows the access-token contains three base64 encoded splitted with two dots (.) separators, which indicates it's a JSON Web Token (JWT):

Header

{
 "alg": "HS256",
 "typ": "JWT"
}

Claims

{
 "exp": 1553003718,
 "iat": 1553003418,
 "nbf": 1553003418,
 "identity": 1
}

Signature

Last encrypted part, containing the digital signature for the token..

Exploitation

Step 1

As shown in the above picture, there are 2 points which can be tampered.

  • alg header: contains the information of which algorithm is being used for digital signature of the token.

  • indentity: this information is used by the application to identify which user ID is currently authenticated.

How about checking if the server is blindly accepting the digital signature algorithm as stored by token. Of course, changing the signature would also change the token signature, but, what if the server accepts NONE algorithm?

The NONE algorithm means signature is not required, so the token can be tampered and will be accepted by the server.

=======

Step 2

Header tampering

{
  "typ": "JWT",
  "alg": "NONE"
}
#base64 eyJ0eXAiOiJKV1QiLCAiYWxnIjoiTk9ORSJ9

Now, let's play with the identity:

{
  "exp": 1553003718,
  "iat": 1553003418,
  "nbf": 1553003418,
  "identity": 2
}

As the signature is not required, the new tampered JWT token will look like this:

eyJ0eXAiOiJKV1QiLCAiYWxnIjoiTk9ORSJ9.eyJleHAiOjE1NTMwMDM3MTgsImlhdCI6MTU1MzAwMzQxOCwibmJmIjoxNTUzMDAzNDE4LCJpZGVudGl0eSI6Mn0.

Step 2

Open the local storage tab within the browser and replace the original token:

Now hit the Admin button and check if the tampered token was accepted.

Yes! The server accepted the tampered access-token. Can we check if there are more users available which can be impersonated?

Additional Resources

Please refer to the JWT.io information for more information regarding JWT.

Also consider OWASP JWT Cheat Sheet as reference.

Other:

A potential attacker can now decode the token in website to check its content.

http://jwt.io
JWT.IO - JSON Web Tokens Introduction
JSON Web Token for Java - OWASP Cheat Sheet Series
https://owasp.org/www-chapter-vancouver/assets/presentations/2020-01_Attacking_and_Securing_JWT.pdf
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