rules:
  - id: auth.go.jwt.none-algorithm
    languages:
      - go
    severity: ERROR
    message: |
      A JWT is created or accepted with the `none` algorithm, which produces an
      unsigned token. Anyone can forge such a token by setting `alg: none` and
      omitting the signature, so the server has no way to verify who issued it:
      a complete authentication bypass (CWE-347). In golang-jwt this happens
      when signing with `jwt.SigningMethodNone` or passing the
      `jwt.UnsafeAllowNoneSignatureType` sentinel to `SignedString`.

      Never use the `none` algorithm. Sign tokens with a real algorithm such as
      HS256 (`jwt.SigningMethodHS256`), RS256 (`jwt.SigningMethodRS256`), or
      ES256 (`jwt.SigningMethodES256`) and verify them with the matching key.
    # Targets code that ENABLES `none`: building a token with
    # `SigningMethodNone`, or the `UnsafeAllowNoneSignatureType` sentinel (which
    # is only ever used to allow none). A defensive comparison such as
    # `token.Method == jwt.SigningMethodNone` to REJECT none is deliberately not
    # flagged. HS256/RS256/ES256 are never matched.
    pattern-either:
      - pattern: jwt.NewWithClaims(jwt.SigningMethodNone, ...)
      - pattern: jwt.New(jwt.SigningMethodNone, ...)
      - pattern: jwt.New(jwt.SigningMethodNone)
      - pattern: jwt.UnsafeAllowNoneSignatureType
    metadata:
      oauthlint-rule-id: AUTH-GO-JWT-001
      oauthlint-doc-url: https://oauthlint.dev/rules/go-jwt-none-algorithm
      category: security
      cwe: CWE-347
      owasp: API2:2023
      llm-prevalence: HIGH
      technology:
        - golang-jwt
      references:
        - https://pkg.go.dev/github.com/golang-jwt/jwt/v5#pkg-variables
        - https://cwe.mitre.org/data/definitions/347.html