NAME
Plack::Middleware::CSRFBlock - Block CSRF Attacks with minimal changes to your app
VERSION
version 0.10
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 a hidden input tag that contains a token string into
forms in the response body. For example, when the application response body is:<html> <head> <title>input form</title> </head> <body> <form action="/api" 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
formtags withmethod="post", case insensitive.It is possible to add an optional meta tag by setting
meta_tagto a defined value. The 'name' attribute of the HTML tag will be set to the value ofmeta_tag. For the previous example, whenmeta_tagis set to 'csrf_token', the output will be:<html> <head><meta name="csrf_token" content="0f15ba869f1c0d77"/> <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> -
input check
For every POST requests, this module checks the
X-CSRF-Tokenheader first, thenPOSTinput parameters. If the correct token is not found in either, then a 403 Forbidden is returned by default.Supports
application/x-www-form-urlencodedandmultipart/form-datafor input parameters, but anyPOSTwill be validated with theX-CSRF-Tokenheader. Thus, everyPOSTwill have to have either the header, or the appropriate form parameters in the body. -
javascript
This module can be used easily with javascript by having your javascript provide the
X-CSRF-Tokenwith any ajaxPOSTrequests it makes. You can get thetokenin javascript by getting the value of thecsrftokenmetatag in the page . Here is sample code that will work forjQuery:$(document).ajaxSend(function(e, xhr, options) { var token = $("meta[name='csrftoken']").attr("content"); xhr.setRequestHeader("X-CSRF-Token", token); });This will include the X-CSRF-Token header with any
AJAXrequests made from your javascript.
OPTIONS
use Plack::Builder;
my $app = sub { ... }
builder {
enable 'Session';
enable 'CSRFBlock',
parameter_name => 'csrf_secret',
token_length => 20,
session_key => 'csrf_token',
blocked => sub {
[302, [Location => 'http://www.google.com'], ['']];
},
onetime => 0,
;
$app;
}
-
parameter_name (default:"SEC")
Name of the input tag for the token.
-
meta_tag (default:undef)
Name of the
metatag added to theheadtag of output pages. The content of thismetatag will be the token value. The purpose of this tag is to give javascript access to the token if needed for AJAX requests. If this attribute is not explicitly set the meta tag will not be included. -
header_name (default:"X-CSRF-Token")
Name of the HTTP Header that the token can be sent in. This is useful for sending the header for Javascript AJAX requests, and this header is required for any post request that is not of type
application/x-www-form-urlencodedormultipart/form-data. -
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.
SEE ALSO
AUTHORS
- Rintaro Ishizaki rintaro@cpan.org
- William Wolf throughnothing@gmail.com
- Matthew Phillips mattp@cpan.org
COPYRIGHT AND LICENSE
This software is copyright (c) 2014 by the Authors of Plack-Middleware-CSRFBlock.
This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.