rules:
  - id: auth.csharp.crypto.ecb-mode
    languages:
      - csharp
    severity: WARNING
    message: |
      A symmetric cipher is configured with `CipherMode.ECB`. ECB encrypts each
      block independently, so identical plaintext blocks produce identical
      ciphertext, leaking structure and enabling block-shuffling attacks
      (CWE-327). This matters for anything auth-related: encrypted tokens,
      cookies, or credentials.

      Use an authenticated mode instead: prefer AES-GCM
      (`AesGcm`) or, failing that, CBC with a random IV and a separate MAC.
    patterns:
      - pattern-either:
          - pattern: $X.Mode = System.Security.Cryptography.CipherMode.ECB
          - pattern: $X.Mode = CipherMode.ECB
    paths:
      exclude:
        - "**/test/**"
        - "**/*Test.cs"
        - "**/*Tests.cs"
    metadata:
      oauthlint-rule-id: AUTH-CSHARP-CRYPTO-003
      oauthlint-doc-url: https://oauthlint.dev/rules/csharp-crypto-ecb-mode
      category: security
      cwe: CWE-327
      owasp: A02:2021
      llm-prevalence: MEDIUM
      technology:
        - dotnet
      references:
        - https://cwe.mitre.org/data/definitions/327.html