ruby.jwt.security.jwt-none-alg.ruby-jwt-none-alg

Verifed by r2c
Community Favorite
profile photo of semgrepsemgrep
Author
63,819
Download Count*
LGPL Commons Clause
License

Detected use of the 'none' algorithm in a JWT token. The 'none' algorithm assumes the integrity of the token has already been verified. This would allow a malicious actor to forge a JWT token that will automatically be verified. Do not explicitly use the 'none' algorithm. Instead, use an algorithm such as 'HS256'.

Run Locally

Run in CI

Semgrep CI docs

Defintion

Edit RuleView Source
Open in Playground 
rules:
  - id: ruby-jwt-none-alg
    message: Detected use of the 'none' algorithm in a JWT token. The 'none'
      algorithm assumes the integrity of the token has already been verified.
      This would allow a malicious actor to forge a JWT token that will
      automatically be verified. Do not explicitly use the 'none' algorithm.
      Instead, use an algorithm such as 'HS256'.
    metadata:
      cwe:
        - "CWE-327: Use of a Broken or Risky Cryptographic Algorithm"
      owasp:
        - A03:2017 - Sensitive Data Exposure
        - A02:2021 - Cryptographic Failures
      source-rule-url: https://semgrep.dev/blog/2020/hardcoded-secrets-unverified-tokens-and-other-common-jwt-mistakes/
      category: security
      technology:
        - jwt
      references:
        - https://owasp.org/Top10/A02_2021-Cryptographic_Failures
      subcategory:
        - audit
      likelihood: LOW
      impact: LOW
      confidence: LOW
      license: Commons Clause License Condition v1.0[LGPL-2.1-only]
      vulnerability_class:
        - Cryptographic Issues
    languages:
      - ruby
    severity: ERROR
    patterns:
      - pattern-inside: |
          require 'jwt'
          ...
      - pattern: |
          JWT.encode($PAYLOAD, $SECRET, 'none', ...)

Examples

jwt-none-alg.rb

require 'jwt'

def bad1
    payload = { data: 'test' }
    # ruleid: ruby-jwt-none-alg
    token = JWT.encode payload, nil, 'none'
    puts token
end

def ok1(hmac_secret)
    # ok: ruby-jwt-none-alg
    token = JWT.encode payload, hmac_secret, 'HS256'
    puts token
    decoded_token = JWT.decode token, hmac_secret, true, { algorithm: 'HS256' }
    puts decoded_token
end