rules:
  - id: auth.java.jwt.none-algorithm
    languages:
      - java
    severity: ERROR
    message: |
      A JWT is created or verified with the `none` algorithm, which means there
      is no signature at all. An `alg=none` token can be forged by anyone.
      Changing the subject, roles, or expiry costs nothing because there is no
      signature to verify (CWE-347). This is a common AI-generated mistake: the
      "no signature" algorithm is reached for during prototyping or testing and
      never swapped for a real signing key.

      Always sign and verify with a real algorithm. With jjwt use
      `Jwts.builder()...signWith(key)` and a keyed parser; with Auth0 java-jwt
      use `Algorithm.HMAC256(secret)` / `Algorithm.RSA256(...)` instead of
      `Algorithm.none()`.
    # jjwt (io.jsonwebtoken): the SignatureAlgorithm.NONE enum constant.
    # Auth0 java-jwt (com.auth0.jwt): the Algorithm.none() factory.
    pattern-either:
      - pattern: io.jsonwebtoken.SignatureAlgorithm.NONE
      - pattern: SignatureAlgorithm.NONE
      - pattern: com.auth0.jwt.algorithms.Algorithm.none()
      - pattern: Algorithm.none()
    metadata:
      oauthlint-rule-id: AUTH-JAVA-JWT-004
      oauthlint-doc-url: https://oauthlint.dev/rules/java-jwt-none-algorithm
      category: security
      cwe: CWE-347
      owasp: API2:2023
      llm-prevalence: MEDIUM
      technology:
        - jjwt
        - java-jwt
      references:
        - https://datatracker.ietf.org/doc/html/rfc8725#section-2.1
        - https://cwe.mitre.org/data/definitions/347.html