rules:
  - id: auth.java.crypto.weak-hash
    languages:
      - java
    severity: WARNING
    message: |
      A broken hash algorithm (MD5 or SHA-1) is being instantiated via JCA
      `MessageDigest.getInstance(...)`. MD5 and SHA-1 are cryptographically
      broken: practical collision attacks exist, so they must NOT be used for
      any security purpose: integrity checks, content/token fingerprints,
      digital signatures, HMAC keys, or deduplication that a trust decision
      depends on (CWE-328 / CWE-327).

      Use SHA-256 or stronger (SHA-384, SHA-512, SHA-3):
      `MessageDigest.getInstance("SHA-256")`. Note: this rule covers the general
      weak-digest case; storing *passwords* needs a dedicated slow hasher
      (BCrypt/Argon2/PBKDF2), which is enforced separately.
    # Match only the algorithm string passed to MessageDigest.getInstance(...).
    # The metavariable-regex flags the broken digests MD5, SHA-1 and the SHA1
    # alias (case-insensitive, optional hyphen). It is scoped to the
    # getInstance(...) instantiation site on purpose so it is low-FP and does
    # NOT overlap auth.java.crypto.weak-password-hash, which instead anchors on
    # a password-named digest()/update() call (and also flags SHA-256/SHA-512 in
    # that password context). "SHA-256"/"SHA-512" are silent here.
    patterns:
      - pattern: java.security.MessageDigest.getInstance($ALG, ...)
      - metavariable-regex:
          metavariable: $ALG
          regex: (?i)^"(md5|sha-?1)"$
    metadata:
      oauthlint-rule-id: AUTH-JAVA-CRYPTO-004
      oauthlint-doc-url: https://oauthlint.dev/rules/java-crypto-weak-hash
      category: security
      cwe: CWE-328
      owasp: A02:2021
      llm-prevalence: MEDIUM
      technology:
        - java
      references:
        - https://cwe.mitre.org/data/definitions/328.html
        - https://csrc.nist.gov/news/2022/nist-transitioning-away-from-sha-1-for-all-apps