I know I can use the ActionView helper strip_tags method in my views to sanitize output, but what is the best way to sanitize user input before I persist it to my db? Should I find a way to include the view helper in my controller and reuse the strip_tags method? I thought rails would have something available globally to do something like this.
What about the xss_terminate plugin ?
maybe sanitize gem: http://wonko.com/post/sanitize
Why do you need to sanitize the user's input?
Typically, all that is needed is rigorous, context-aware encoding/escaping of the user's input any time you print it or embed it within a larger block of output.
Why do you want to sanitize user inputs? That doesn't even make any sense! You always want to sanitize (escape) outputs, not inputs, because the meaning of sanitization depends on the context that you are using the content in. There is no such thing as a string that is safe in any context. You do not want a bunch of mangled strings in your database that are "safe" in whatever scenario your application is using them today, because tomorrow, you might want to do something different with them. If your presentation layer is doing the right thing (escaping content based on the context), then you're fine, no matter how many quotes, backslashes or DROP TABLE statements are in them.
Related
In my rails 4 app i want to add comments to my articles, but i want to add functional as most forum-engines do (like SMF), and i need to add bb-code for it.
Are there any good gem for it? With rails 4 support? How then in controller i can translate [quote] to some div with some style?
Also how is it good to store html data in database?
For example if i use haml, and somebody post comment as
- current_user.id
or something similar to this, how to secure my app from "bad boys" ? Sure i can change comments system to something like: quote_parent_id, but if i have multiple quotes in one comment? so it is hard to realise, better is to store html, but to secure it somehow.
Could i do this? And how? Please give good ideas, tutorials, gem-links.
Look into https://github.com/veger/ruby-bbcode
Since it converts to HTML and does not excecute user input as Ruby code - you'll be fairly safe. However, I havent tried the gem and its possible it introduces some XSS vulnerabilities.
Have you considered Markdown as an option?
You should also look into https://github.com/asceth/bbcoder ( I should note I am the original author ).
In the controller, changing a string such as "[quote=user]My post of epic importance[/quote]" into a div etc is just doing:
# assume params[:comment] is the text you are converting
params[:comment].bbcode_to_html
As for storing html in a database, there is no right or wrong answer. If you want to allow users to edit their posts later then I would lean towards not storing the html version but storing their original bbcode version. This way when you allow them to edit you aren't having to convert html back to bbcode.
To make sure you aren't open to XSS and other attacks I recommend combining other gems like sanitize.
Sanitize.clean(text.to_s).bbcode_to_html
Some more notes:
Multiple tags and nested tags are parsed as they are seen without any additional steps required. So a comment or post with lots of bbcode tags, multiple quotes, b tags or anything else is dealt with by just calling bbcode_to_html on the variable/string.
If a user tries to use haml in their post it should appear as-is. haml shouldn't try to eval the string unless you specifically tell it to which I'm not even sure how to do that unless haml as a special filter or operator.
I have a question.
I have comment model, in which it has body column that users can type anything in there.
obviously user might type the url link to other website.
In my guess, I think it should be replaced with < a href > tag when it is being saved.
Is there any good gem or something to handle this kind of thing?
If you don't want to use a full-blown markdown parser (Redcarpet), use Rinku. It's super fast and safe. Do not use any regex based solutions as you would most likely open yourself to security risks.
text = "Hello! Check this out: https://github.com/vmg/rinku"
Rinku.auto_link(text, mode=:all, link_attr=nil, skip_tags=nil)
Produces:
=> "Hello! Check this out: https://github.com/vmg/rinku"
Preserving for posterity's sake, but I feel it's important to note that this is NOT a secure way to solve the problem. Unless you want to figure out all the security implications for yourself, don't follow this advice. Jiří Pospíšil's answer is better. =D
You don't really need a gem to do that (I personally try to avoid gems for something so simple). Write a regular expression that is reasonably reliable for your purposes, and then use something like
input.gsub(regex, 'some text')
to convert the links into their html equivalent. Note that you'll need to use raw to display the results of this, otherwise rails will escape the output for you. This also means users will be able to put other arbitrary markup in, unless you escape it as it goes into the database. Make sure you do that.
Alternately, you could do the same thing as you display it, with slightly different considerations/steps necessary.
When I allow a user to enter text using s:textfield, he can enter something like <b>Name</b> or something like \Me/. I want that these should be escaped before I am saving them to the database. When we retrieve them, the escaping is done automatically, but I want it to happen also when we are saving it.
I was trying to return a json output from my action class, but due to a name \a/ stored in my database, wrong json was being formed. This would have been avoided if the name had been escaped before being saved into the database.
You can use StringEscapeUtils. You can call escapeJavascript(textfield) in your action and then store it into the database.
#Daud, The problem you explained is called Cross site scripting or XSS.
And I think you should use Filters to clean the request parameters. This is the most sophisticated way. You can call these filters for the actions which are posting some parameters via request.
Visit my blog to see how to avoid XSS threat using Filter approach.
I also faced this issue when our project was tested by well known firm specializing in security testing and they suggested this filter approach.
You can give it a try.
Can I use ActionView::Helpers::SanitizeHelper#sanitize on user-entered text that I plan on showing to other users? E.g., will it properly handle all cases described on this site?
Also, the documentation mentions:
Please note that sanitizing
user-provided text does not guarantee
that the resulting markup is valid
(conforming to a document type) or
even well-formed. The output may still
contain e.g. unescaped ’<’, ’>’, ’&’
characters and confuse browsers.
What's the best way to handle this? Pass the sanitized text through Hpricot before displaying?
Ryan Grove's Sanitize goes a lot farther than Rails 3 sanitize. It ensures the output HTML is well-formed and has three built-in whitelists:
Sanitize::Config::RESTRICTED
Allows only very simple inline formatting markup. No links, images, or block elements.
Sanitize::Config::BASIC
Allows a variety of markup including formatting tags, links, and lists. Images and tables are not allowed, links are limited to FTP, HTTP, HTTPS, and mailto protocols, and a attribute is added to all links to mitigate SEO spam.
Sanitize::Config::RELAXED Allows an even wider variety of markup than BASIC, including images and tables. Links are still limited to FTP, HTTP, HTTPS, and mailto protocols, while images are limited to HTTP and HTTPS. In this mode, is not added to links.
Sanitize is certainly better than the "h" helper. Instead of escaping everything, it actually allows the html tags that you specify. And yes, it does prevent cross-site scripting because it removes javascript from the mix entirely.
In short, both will get the job done. Use "h" when you don't expect anything other than plaintext, and use sanitize when you want to allow some, or you believe people may try to enter it. Even if you disallow all tags with sanitize, it'll "pretty up" the code by removing them instead of escaping them as "h" does.
As for incomplete tags: You could run a validation on the model that passes html-containing fields through hpricot, but I think this is overkill in most applications.
The best course of action depends on two things:
Your rails version (2.x or 3.x)
Whether your users are supposed to enter any html at all on the input or not.
As a general rule, I don't allow my users to input html - instead I let them input textile.
On rails 3.x:
User input is sanitized by default. You don't have to do anything, unless you want your users to be able to send some html. In that case, keep reading.
This railscast deals with XSS attacks on rails 3.
On rails 2.x:
If you don't allow any html from your users, just protect your output with the h method, like this:
<%= h post.text %>
If you want your users to send some html: you can use rails' sanitize method or HTML::StathamSanitizer
What is the best solution to sanitize output HTML in Rails (to avoid XSS attacks)?
I have two options: white_list plugin or sanitize method from Sanitize Helper http://api.rubyonrails.com/classes/ActionView/Helpers/SanitizeHelper.html . For me until today the white_list plugin worked better and in the past, Sanitize was very buggy, but as part of the Core, probably it will be under development and be supported for a while.
I recommend http://code.google.com/p/xssterminate/.
I think the h helper method will work here:
<%= h #user.profile %>
This will escape angle brackets and therefore neutralize any embedded JavaScript. Of course this will also eliminate any formatting your users might use.
If you want formatting, maybe look at markdown.
Personally I think it's not a small decision to accept any HTML entry in any web app. You can test for white/blacklisted tags as much as you like, but unless you're testing for correct nesting, someone could enter a series of closing tags, for example
</td></tr></span></div>
and really mess with your layout.
I'd usually give people something like Textile to enter their markup, since I'd rather spend my time working on business logic than HTML parsing.
Of course, if this text entry is more fundamental to your app (as for example it is for stackoverflow) then you probably should give more attention to hand-rolling your own.