[CVE-2021-22904] Possible DoS Vulnerability in Action Controller Token Authentication

[Aaron Patterson]

There is a possible DoS vulnerability in the Token Authentication logic in

Action Controller.  This vulnerability has been assigned the CVE identifier

CVE-2021-22904.

Versions Affected:  >= 4.0.0

Not affected:       < 4.0.0

Fixed Versions:     6.1.3.2, 6.0.3.7, 5.2.4.6, 5.2.6

Impact

------

Impacted code uses `authenticate_or_request_with_http_token` or

`authenticate_with_http_token` for request authentication.  Impacted code will

look something like this:

```

class PostsController < ApplicationController

  before_action :authenticate

  private

  def authenticate

    authenticate_or_request_with_http_token do |token, options|

      # ...

    end

  end

end

```

All users running an affected release should either upgrade or use one of the

workarounds immediately.

Releases

--------

The fixed releases are available at the normal locations.

Workarounds

-----------

The following monkey patch placed in an initializer can be used to work around

the issue:

```ruby

module ActionController::HttpAuthentication::Token

  AUTHN_PAIR_DELIMITERS = /(?:,|;|\t)/

end

```

Patches

-------

To aid users who aren't able to upgrade immediately we have provided patches for

the two supported release series. They are in git-am format and consist of a

single changeset.

* 5-2-http-authentication-dos.patch - Patch for 5.2 series

* 6-0-http-authentication-dos.patch - Patch for 6.0 series

* 6-1-http-authentication-dos.patch - Patch for 6.1 series

Please note that only the 6.1.Z, 6.0.Z, and 5.2.Z series are supported at

present. Users of earlier unsupported releases are advised to upgrade as soon

as possible as we cannot guarantee the continued availability of security

fixes for unsupported releases.

Credits

-------

Thank you to https://hackerone.com/wonda_tea_coffee for reporting this issue!

--

Aaron Patterson
http://tenderlovemaking.com/