java.java-jwt.security.jwt-none-alg.java-jwt-none-alg

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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'.

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Defintion

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rules:
  - id: java-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
      confidence: HIGH
      references:
        - https://owasp.org/Top10/A02_2021-Cryptographic_Failures
      subcategory:
        - vuln
      likelihood: HIGH
      impact: MEDIUM
      license: Commons Clause License Condition v1.0[LGPL-2.1-only]
      vulnerability_class:
        - Cryptographic Issues
    languages:
      - java
    severity: ERROR
    pattern-either:
      - pattern: |
          $JWT.sign(com.auth0.jwt.algorithms.Algorithm.none());
      - pattern: |
          $NONE = com.auth0.jwt.algorithms.Algorithm.none();
          ...
          $JWT.sign($NONE);
      - pattern: |-
          class $CLASS {
            ...
            $TYPE $NONE = com.auth0.jwt.algorithms.Algorithm.none();
            ...
            $RETURNTYPE $FUNC (...) {
              ...
              $JWT.sign($NONE);
              ...
            }
            ...
          }

Examples

jwt-none-alg.java

package jwt_test.jwt_test_1;

import com.auth0.jwt.JWT;
import com.auth0.jwt.algorithms.Algorithm;
import com.auth0.jwt.exceptions.JWTCreationException;

public class App
{

    private static void bad1() {
        try {
            // ruleid: java-jwt-none-alg
            Algorithm algorithm = Algorithm.none();
            String token = JWT.create()
                .withIssuer("auth0")
                .sign(algorithm);
        } catch (JWTCreationException exception){
            //Invalid Signing configuration / Couldn't convert Claims.
        }
    }

    private static void bad2() {
        try {
            // ruleid: java-jwt-none-alg
            String token = JWT.create()
                .withIssuer("auth0")
                .sign(Algorithm.none());
        } catch (JWTCreationException exception){
            //Invalid Signing configuration / Couldn't convert Claims.
        }
    }

    private static void ok1(String secretKey) {
        try {
            // ok: java-jwt-none-alg
            Algorithm algorithm = Algorithm.HMAC256(secretKey);
            String token = JWT.create()
                .withIssuer("auth0")
                .sign(algorithm);
        } catch (JWTCreationException exception){
            //Invalid Signing configuration / Couldn't convert Claims.
        }
    }

    public static void main( String[] args )
    {
        bad1();
        bad2();
        ok1(args[0]);
    }
}