rules:
  - id: auth.java.jwt.unsigned-jwt
    languages:
      - java
    severity: ERROR
    message: |
      This JWT is created or parsed without a signature, so its contents are
      neither authenticated nor tamper-proof (CWE-347). An unsecured ("alg=none")
      token can be forged by anyone. Changing the claims (e.g. the subject or
      roles) costs nothing because there is no signature to verify. This is a
      common AI-generated mistake: the "plaintext"/"unsecured" JWT API is reached
      for during prototyping and never swapped for a signed token.

      Sign tokens and verify their signatures. With nimbus-jose-jwt use
      `SignedJWT` (and verify with a `JWSVerifier`); with jjwt build tokens via
      `Jwts.builder()...signWith(key)` and parse them with `parseSignedClaims`
      (or the legacy `parseClaimsJws`) instead of `parseClaimsJwt` /
      `parsePlaintextJwt`.
    # nimbus-jose-jwt: PlainJWT is the unsecured (alg=none) variant.
    # jjwt (io.jsonwebtoken): parseClaimsJwt / parsePlaintextJwt parse an
    # UNSIGNED JWT; the signed counterparts are parseSignedClaims /
    # parseClaimsJws and are intentionally not matched.
    pattern-either:
      - pattern: new com.nimbusds.jwt.PlainJWT(...)
      - pattern: new PlainJWT(...)
      - pattern: $P.parseClaimsJwt(...)
      - pattern: $P.parsePlaintextJwt(...)
    metadata:
      oauthlint-rule-id: AUTH-JAVA-JWT-001
      oauthlint-doc-url: https://oauthlint.dev/rules/java-jwt-unsigned-jwt
      category: security
      cwe: CWE-347
      owasp: API2:2023
      llm-prevalence: MEDIUM
      technology:
        - jjwt
        - nimbus-jose-jwt
      references:
        - https://connect2id.com/products/nimbus-jose-jwt/examples/unsecured-jwt
        - https://github.com/jwtk/jjwt#reading-a-jwt
        - https://cwe.mitre.org/data/definitions/347.html