NAME
    Plack::Middleware::CSRFBlock - CSRF are never propageted to app

SYNOPSIS
      use Plack::Builder;
  
      my $app = sub { ... }
  
      builder {
        enable 'Session';
        enable 'CSRFBlock';
        $app;
      }

DESCRIPTION
    This middleware blocks CSRF. You can use this middleware without any
    modifications to your application, in most cases. Here is the strategy:

    output filter
        When the application response content-type is "text/html" or
        "application/xhtml+xml", this inserts hidden input tag that contains
        token string into "form"s in the response body. For example, the
        application response body is:

          <html>
            <head><title>input form</title></head>
            <body>
              <form action="/receive" method="post">
                <input type="text" name="email" /><input type="submit" />
              </form>
          </html>

        this becomes:

          <html>
            <head><title>input form</title></head>
            <body>
              <form action="/api" method="post"><input type="hidden" name="SEC" value="0f15ba869f1c0d77" />
                <input type="text" name="email" /><input type="submit" />
              </form>
          </html>

        This affects "form" tags with "method="post"", case insensitive.

    input check
        For every POST requests, this module checks input parameters contain
        the collect token parameter. If not found, throws 403 Forbidden by
        default.

        Supports "application/x-www-form-urlencoded" and
        "multipart/form-data".

OPTIONS
    parameter_name (default:"SEC")
        Name of the input tag for the token.

    token_length (default:16);
        Length of the token string. Max value is 40.

    session_key (default:"csrfblock.token")
        This middleware uses Plack::Middleware::Session for token storage.
        this is the session key for that.

    blocked (default:403 response)
        The application called when CSRF is detected.

        Note: This application can read posted data, but DO NOT use them!

    onetime (default:FALSE)
        If this is true, this middleware uses onetime token, that is,
        whenever client sent collect token and this middleware detect that,
        token string is regenerated.

        This makes your applications more secure, but in many cases, is too
        strict.

CAVEATS
    This middleware doesn't work with pure Ajax POST request, because it
    cannot insert the token parameter to the request. We suggest, for
    example, to use jQuery Form Plugin like:

      <script type="text/javascript" src="jquery.js"></script>
      <script type="text/javascript" src="jquery.form.js"></script>

      <form action="/api" method="post" id="theform">
        ... blah ...
      </form>
      <script type="text/javascript>
        $('#theform').ajaxForm();
      </script>

    so, the middleware can insert token "input" tag next to "form" start
    tag, and the client can send it by Ajax form.

AUTHOR
    Rintaro Ishizaki <rintaro@cpan.org>

SEE ALSO
    Plack::Middleware::Session

LICENSE
    This library is free software; you can redistribute it and/or modify it
    under the same terms as Perl itself.

