Default Config:

• Cookie name is SESSION.
• Encoding and decoding of msg is done through ToJSON and FromJSON.

• The Encryption scheme is the nonce-misuse resistant AEAD_AES_256_GCM_SIV as defined in in RFC 8452, using a Wai.CSRF.Token as AEAD associated data.

  As an AEAD encryption scheme, you can be confident that a successfully decrypted cookie could only have been encrypted by the same Key known only to your server, and associated with a specific Wai.CSRF.Token, expected to have been sent with the incoming request.

  In principle, this makes this encryption scheme suitable for storing server-generated user session data in the msg. However, you must make sure that you rotate the Wai.CSRF.Token ocassionally, at least each time a new user session is established, so as to avoid CSRF risks.

• This defaultConfig suggests you should be composing middleware and Wai.CSRF.middleware in this way:

  Wai.CSRF.middleware myCsrfConfig
     . Wai.CryptoCookie.middleware myCryptoCookieEnv
          :: (Maybe (Wai.CSRF.Token, msg) -> Application)
          -> Application
  

Configuration for Env.

Consider using defaultConfig and updating desired fields only.

Stateful encryption environment for interacting with the encrypted cookie.

It is safe to use Env concurrently if necessary. Concurrency is handled safely internally.

Obtain with newEnv.

Obtain a new Env.

Transform an Application so that if there is an encrypted message in the incoming Request cookies, it will be automatically decrypted and made available to the underlying Application.

The aad is the AEAD associated data that came with the Request. Consider using middleware in conjunction with Wai.CSRF.middleware, using Wai.CSRF.Token as aad.

Obtain the msg from the Request cookies.

You don't need to use this if you are using middleware.

Construct a SetCookie containing the encrypted msg.

The associated data aad will not be included in this cookie, but it will be taken into account for encryption and necessary for eventual decryption.

The SetCookie has these settings, some of which could be overriden.

• Cookie name is Config's cookieName.
• HttpOnly: Yes, and you shouldn't change this.
• Max-Age and Expires: This cookie never expires. We recommend relying on server-side expiration instead, as the lifetime of the cookie could easily be extended by a legitimate but malicious client. You can store a creation or expiration timestamp inside msg, and make a decision based on that.
• Path: /
• SameSite: Lax.
• Secure: Yes.
• Domain: Not set.

Note: If you are using Wai.CSRF.Token as aad, it is recommended that you generate a new Wai.CSRF.Token at least each time a new user session is established, but possibly more frequently, and send it alongside this one (see Wai.CSRF.setCookie).

Construct a SetCookie expiring the cookie named Config's cookieName.

AEAD encryption method.

If the FilePath exists, then read the base-16 representation of a Key from it. Ignores trailing newlines.

Otherwise, generate a random new Key and write its base-16 representation in the FilePath.

Finally, return the Key.

Read a base-16 encoded Key from a file. Ignores trailing newlines.

Read a Key from a file.

Save a key to a file.