mirror of
https://codeberg.org/forgejo/forgejo.git
synced 2024-11-24 08:57:03 -05:00
104 lines
4.4 KiB
Go
104 lines
4.4 KiB
Go
// Copyright (c) 2014, David Kitchen <david@buro9.com>
|
|
//
|
|
// All rights reserved.
|
|
//
|
|
// Redistribution and use in source and binary forms, with or without
|
|
// modification, are permitted provided that the following conditions are met:
|
|
//
|
|
// * Redistributions of source code must retain the above copyright notice, this
|
|
// list of conditions and the following disclaimer.
|
|
//
|
|
// * Redistributions in binary form must reproduce the above copyright notice,
|
|
// this list of conditions and the following disclaimer in the documentation
|
|
// and/or other materials provided with the distribution.
|
|
//
|
|
// * Neither the name of the organisation (Microcosm) nor the names of its
|
|
// contributors may be used to endorse or promote products derived from
|
|
// this software without specific prior written permission.
|
|
//
|
|
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
|
|
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
|
|
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
|
|
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
|
|
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
|
|
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
|
|
// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
|
|
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
|
|
|
/*
|
|
Package bluemonday provides a way of describing a whitelist of HTML elements
|
|
and attributes as a policy, and for that policy to be applied to untrusted
|
|
strings from users that may contain markup. All elements and attributes not on
|
|
the whitelist will be stripped.
|
|
|
|
The default bluemonday.UGCPolicy().Sanitize() turns this:
|
|
|
|
Hello <STYLE>.XSS{background-image:url("javascript:alert('XSS')");}</STYLE><A CLASS=XSS></A>World
|
|
|
|
Into the more harmless:
|
|
|
|
Hello World
|
|
|
|
And it turns this:
|
|
|
|
<a href="javascript:alert('XSS1')" onmouseover="alert('XSS2')">XSS<a>
|
|
|
|
Into this:
|
|
|
|
XSS
|
|
|
|
Whilst still allowing this:
|
|
|
|
<a href="http://www.google.com/">
|
|
<img src="https://ssl.gstatic.com/accounts/ui/logo_2x.png"/>
|
|
</a>
|
|
|
|
To pass through mostly unaltered (it gained a rel="nofollow"):
|
|
|
|
<a href="http://www.google.com/" rel="nofollow">
|
|
<img src="https://ssl.gstatic.com/accounts/ui/logo_2x.png"/>
|
|
</a>
|
|
|
|
The primary purpose of bluemonday is to take potentially unsafe user generated
|
|
content (from things like Markdown, HTML WYSIWYG tools, etc) and make it safe
|
|
for you to put on your website.
|
|
|
|
It protects sites against XSS (http://en.wikipedia.org/wiki/Cross-site_scripting)
|
|
and other malicious content that a user interface may deliver. There are many
|
|
vectors for an XSS attack (https://www.owasp.org/index.php/XSS_Filter_Evasion_Cheat_Sheet)
|
|
and the safest thing to do is to sanitize user input against a known safe list
|
|
of HTML elements and attributes.
|
|
|
|
Note: You should always run bluemonday after any other processing.
|
|
|
|
If you use blackfriday (https://github.com/russross/blackfriday) or
|
|
Pandoc (http://johnmacfarlane.net/pandoc/) then bluemonday should be run after
|
|
these steps. This ensures that no insecure HTML is introduced later in your
|
|
process.
|
|
|
|
bluemonday is heavily inspired by both the OWASP Java HTML Sanitizer
|
|
(https://code.google.com/p/owasp-java-html-sanitizer/) and the HTML Purifier
|
|
(http://htmlpurifier.org/).
|
|
|
|
We ship two default policies, one is bluemonday.StrictPolicy() and can be
|
|
thought of as equivalent to stripping all HTML elements and their attributes as
|
|
it has nothing on it's whitelist.
|
|
|
|
The other is bluemonday.UGCPolicy() and allows a broad selection of HTML
|
|
elements and attributes that are safe for user generated content. Note that
|
|
this policy does not whitelist iframes, object, embed, styles, script, etc.
|
|
|
|
The essence of building a policy is to determine which HTML elements and
|
|
attributes are considered safe for your scenario. OWASP provide an XSS
|
|
prevention cheat sheet ( https://www.google.com/search?q=xss+prevention+cheat+sheet )
|
|
to help explain the risks, but essentially:
|
|
|
|
1. Avoid whitelisting anything other than plain HTML elements
|
|
2. Avoid whitelisting `script`, `style`, `iframe`, `object`, `embed`, `base`
|
|
elements
|
|
3. Avoid whitelisting anything other than plain HTML elements with simple
|
|
values that you can match to a regexp
|
|
*/
|
|
package bluemonday
|