I'm planning a webapp that will allow users to create resources without signing in. I plan on using the Google Docs / Pastebin style of security by creating unique hard-to-guess URLs. (e.g. example.com/ytasdfweoirue/)
What are some things to watch out for? What guidelines would you use in designing the token generator? What are some things I should consider? Is there a best set of characters to choose from?
My backend will likely be CouchDB, but I'm interested in platform agnostic, general guidelines and problems that might crop up in any platform.
Use PRNG
You should generate a random URL with a PRNG, not with your framework's simplest Random() function. (FYI In theory .NET GUID is not designed for security, in practice in a web app you should be fine, but you've been warned)
Do not include 3rd party resources in the "hidden" page
Ensure that the page visitors visit do not include any 3rd party resources (javascripts, images, flash animations etc.) Pretty much all of them will leak the the current URL via REFERRER and your hidden URL will be exposed to all those 3rd parties. This is same even if you are using HTTPS and included URLs are using HTTPs.
Do not include links to 3rd party websites, if you have to then take care of Referrers
Again REFERRER leaking can be a problem if the page you are serving includes links to 3rd party URLs. In which case you can either redirect them from a common page (if you do so be careful about Open Redirect vulnerabilities) or you can use a JavaScript trick to strip REFERRER.
You don't mention your technology stack, but the best option here sounds like a Guid. Just have your url:
http://whatever.com/resource/{guid}
Guids are long enough to be hard / impossible to guess or enumerate and you have a pretty strong guarantee that you won't generate two guids that are the same. As long as you aren't in javascript, your language should have a guid generator available as a built in (.net) or a library.
Here is the wikipedia page for more discussion: http://en.wikipedia.org/wiki/Globally_unique_identifier
Related
I'm using CakePHP 2.6. I want to create a website like blogger(blogspot) where every registered user has its subdomain and can add its articles add javascript codes.
Is is safe to allow registered users to add javascripts on their subdomains?
Thanks
Is is safe to allow registered users to add javascripts on their
subdomains?
If done right yes. Search for JSONP, CSRF, XSS, CORS, and same origin policy.
I'm clearly not going to explain all of this in an answer, it is far to much for this place here.
Allowing arbitrary JavaScript, Flash and other active content (such as iframes etc...) from untrusted sources carries a security risk. JavaScript and other active content can be used for malicious purposes through the use of Cross-Site Scripting (XSS).
Allowing JavaScript from untrusted sources has caused issues in the past (one of the most famous examples of this was the MySpace XSS worm).
For an overview on XSS I suggest you take a look at the following resource from Acunetix.
How difficult/easy is it to break into Joomla backend & to access the pages which are only set to be accessible by selected Joomla users of the website? Is it safe enough to rely on Joomla's management system?
Yes, Joomla is quite secure system by itself. Although you have to be careful with third party extensions and always track update news for all components (including core) you have installed and use your judgement about updating them. Usually security issues spotted quite quickly and you have time before succeed attack.
Another thing keep in mind is proactive defense with all possible means you have in hands, this includes .htaccess and .htpasswd, also good idea to restrict ftp access to only local ips and use sftp instead.
Also check out the security extensions around JED, the ones which prevents high level DDoS and extend admin page access protection might be also helpful, usually they are simple modules or plugins.
And yes, do not forget change default username for superuser. And change all passwords ftp/superusers/mysql/htpasswd on regular basis.
Follow this simple rules and you will be fine, at least most of the time you will be fine.
While Joomla security is fairly good, you need to keep up with the patches and, as dmi3y mentioned, you need to watch the third party extensions.
When it comes to information security, nothing is ever perfect. This solution may or may not be appropriate depending on the type of information that you are looking to secure, the number of users accessing it and how you manage the user rights.
By including Google Analytics in a website (specifically the Javascript version) isn't it true that you are giving Google complete access to all your cookies and site information? (ie. it could be a security hole).
Can this be mitigated by putting Google in an iFrame that is sandboxed? Or maybe only passing Google the necessary information (ie. browser type, screen resolution, etc)?
How can someone get the most out of Google Analytics without leaving the entire site open?
Or perhaps passing the data through my own server and then uploading it to Google?
You can create a scriptless implementation via the measurement protocol (for Universal Analytics enabled properties). This not only avoids any security issues with the script (although I'd rather trust Google on that), it also means you have more control what data is submitted to the Google Server.
A script run on your site can read cookies on your site, yes. And that data can be sent back to google, yes. That is why you shouldn't store sensitive information in cookies. You shouldn't do this even if you don't use google analytics. Even if you don't use ANY other code except your own. Browsers and browser addons can also read that stuff and you definitely cannot control that. Again, never store sensitive information in cookies.
As far as access to "site information".. javascript can be used to read the content on your pages, know urls of pages, etc.. IOW anything you serve up on a web page. Anything that is not behind a wall (e.g. login barrier) is surely up for grabs. But crawlers will look at that stuff anyway. Stuff behind walls can still be grabbed automatically, depending on what they have to actually do to get past those walls (e.g. simple registration/login barriers are pretty easy to get past).
This is also why you should never display sensitive information even in content of your site. E.g. credit card numbers, passwords, etc.. that's why virtually every site you go to that has even remotely sensitive information always shows a mask (e.g. ** ) instead of actual values.
Google Analytics does not actively do these things, but you're right: there's nothing stopping them from doing it, and you've already given them the right to do it by using their script.
And you are right: the safest way to control what Google can actually see is to send server-side requests to them. And also put all your content behind barriers that cannot be easily crawled or scraped. The strongest barrier being one that involves having to pay for access. People are ingenious about making bots about making crawlers and bots to get past all sorts of forms and "human" checks etc.. and you're fighting a losing battle on that count, but nothing stops a bot faster than requiring someone to give you money to access your stuff. Of course, this also means you'd have to make everybody pay for access...
Anyways.. if you're that paranoid about this stuff, why use GA at all? Use something you host yourself (e.g. Piwik). This won't solve for crawlers/bots, obviously, but it will solve for worries about GA grabbing more than you want it to.
I'm currently in the process of building a browser helper object.
One of the things the BHO has to do is to make cross-site requests that bypass the cross-domain policy.
For this, I'm exposing a __MyBHONameSpace.Request method that uses WebClient internally.
However, it has occurred to me that anyone that is using my BHO now has a CSRF vulnerability everywhere as a smart attacker can now make arbitrary requests from my clients' computers.
Is there any clever way to mitigate this?
The only way to fully protect against such attacks is to separate the execution context of the page's JavaScript and your extension's JavaScript code.
When I researched this issue, I found that Internet Explorer does provide a way to achieve creation of such context, namely via IActiveScript. I have not implemented this solution though, for the following reasons:
Lack of documentation / examples that combines IActiveScript with BHOs.
Lack of certainty about the future (e.g. https://stackoverflow.com/a/17581825).
Possible performance implications (IE is not known for its superb performance, how would two instances of a JavaScript engines for each page affect the browsing speed?).
Cost of maintenance: I already had an existing solution which was working well, based on very reasonable assumptions. Because I'm not certain whether the alternative method (using IActiveScript) would be bugfree and future-proof (see 2), I decided to drop the idea.
What I have done instead is:
Accept that very determined attackers will be able to access (part of) my extension's functionality.
#Benjamin asked whether access to a persistent storage API would pose a threat to the user's privacy. I consider this risk to be acceptable, because a storage quota is enforced, and all stored data is validated before it's used, and it's not giving an attacker any more tools to attack the user. If an attacker wants to track the user via persistent storage, they can just use localStorage on some domain, and communicate with this domain via an <iframe> using the postMessage API. This method works across all browsers, not just IE with my BHO installed, so it is unlikely that any attacker dedicates time at reverse-engineering my BHO in order to use the API, when there's a method that already works in all modern browsers (IE8+).
Restrict the functionality of the extension:
The extension should only be activated on pages where it needs to be activated. This greatly reduces the attack surface, because it's more difficult for an attacker to run code on https://trusted.example.com and trick the user into visiting https://trusted.example.com.
Create and enforce whitelisted URLs for cross-domain access at extension level (in native code (e.g. C++) inside the BHO).
For sensitive APIs, limit its exposure to a very small set of trusted URLs (again, not in JavaScript, but in native code).
The part of the extension that handles the cross-domain functionality does not share any state with Internet Explorer. Cookies and authorization headers are stripped from the request and response. So, even if an attacker manages to get access to my API, they cannot impersonate the user at some other website, because of missing session information.
This does not protect against sites who use the IP of the requestor for authentication (such as intranet sites or routers), but this attack vector is already covered by a correct implemention a whitelist (see step 2).
"Enforce in native code" does not mean "hard-code in native code". You can still serve updates that include metadata and the JavaScript code. MSVC++ (2010) supports ECMAScript-style regular expressions <regex>, which makes implementing a regex-based whitelist quite easy.
If you want to go ahead and use IActiveScript, you can find sample code in the source code of ceee, Gears (both discontinued) or any other project that attempts to enhance the scripting environment of IE.
Web applications on uncompromised computers are vulnerable to XSS,CRSF,sql injection attacks and cookie stealing in unsecure wifi environments.
To prevent those security issues there are the folowing remedies
sql injection: a good datamapper(like linq-to-sql) does not have the risk of sql injection (am i naïeve to believe this?)
CSRF: Every form-post is verified with the <%:Html.AntiForgeryToken() %> (this is a token in a asp.net mvc environment that is stored in a cookie and verified on the server)
XSS: every form that is allowed to post html is converted, only bb code is allowed, the rest is encoded . All possible save actions are done with a post event so rogue img tags should have no effect
cookie stealing: https
Am i now invulnerable to web-based hacking attempts(when implemented correctly)? Or am i missing some other security issues in web-development?(except for possible holes in the OS platform or other software)
The easy answer is "No you're not invulnerable - nobody is!"
This is a good start, but there are a few other things you could do. The main one you haven't mentioned is validation of untrusted data against a white-list and this is important as it spans multiple exploits such as both SQLi and XSS. Take a look at OWASP Top 10 for .NET developers part 1: Injection and in particular, the section about "All input must be validated against a whitelist of acceptable value ranges".
Next up, you should apply the principle of least privilege to the accounts connecting to your SQL Server. See the heading under this name in the previous link.
Given you're working with ASP.NET, make sure Request Validation remains on and if you absolutely, positively need to disable it, just do it at a page level. More on this in Request Validation, DotNetNuke and design utopia.
For your output encoding, the main thing is to ensure that you're encoding for the right context. HTML encoding != JavaScript encoding != CSS encoding. More on this in OWASP Top 10 for .NET developers part 2: Cross-Site Scripting (XSS).
For the cookies, make them HTTP only and if possible, only allow them to be served securely (if you're happy to only run over HTTPS). Try putting your web.config through the web.config security analyser which will help point you in the right direction.
Another CSRF defense - albeit one with a usability impact - is CAPTCHA. Obviously you want to use this sparingly but if you've got any really critical functions you want to protect, this puts a pretty swift stop to it. More in OWASP Top 10 for .NET developers part 5: Cross-Site Request Forgery (CSRF).
Other than that, it sounds like you're aware of many of the important principles. It won't make you invulnerable, but it's a good start.
Am I now invulnerable to web-based hacking attempts?
Because, no matter how good you are, everyone makes mistakes, the answer is no. You almost certainly forgot to sanitize some input, or use some anti-forgery token. If you haven't now, you or another developer will as your application grows larger.
This is one of the reason we use frameworks - MVC, for example, will automatically generate anti-CSRF tokens, while LINQ-to-SQL (as you mentioned) will sanitize input for the database. So, if you are not already using a framework which makes anti-XSS and anti-CSRF measures the default, you should begin now.
Of course, these will protect you against these specific threats, but it's never possible to be secure against all threats. For instance, if you have an insecure SQL-connection password, it's possible that someone will brute-force your DB password and gain access. If you don't keep your versions of .Net/SQL-Server/everything up to date, you could be the victim of online worm (and even if you do, it's still possible to be zero-dayed).
There are even problems you can't solve in software: A script kiddie could DDOS your site. Your server-company could go bankrupt. A shady competitor could simply take a hedge-clippers to your internet line. Your warehouse could burn down. A developer could sell the source-code to a company in Russia.
The point is, again, you can't ever be secure against everything - you can only be secure against specific threats.
This is the definitive guide to web attacks. Also, I would recommend you use Metasploit against your web app.
It definitely is not enough! There are several other security issues you have to keep in mind when developing a web-app.
To get an overview you can use the OWASP Top-Ten
I think this is an very interesting post to read when thinking about web-security: What should a developer know before building a public web site?
There is a section about security that contains good links for most of the threats you are facing when developing web-apps.
The most important thing to keep in mind when thinking about security is:
Never trust user input!
[I am answering to this "old" question because I think it is always an actual topic.]
About what you didn't mention:
You missed a dangerous attack in MVC frameworks: Over Posting Attack
You also missed the most annoying threats: Denial of Service
You also should pay enough attention to file uploads (if any...) and many more...
About what you mentioned:
XSS is really really really waster and more annoying to mitigate. There are several types of encoding including Html Encoding, Javascript Encoding, CSS Encoding, Html Attribute Encoding, Url Encoding, ...
Each of them should be performed to the proper content, in the proper place - i.e. Just doing Html Encoding the content is not enough in all situations.
And the most annoying about XSS, is that there are some situations that you should perform Combinational Encoding(i.e. first JavascriptEncode and then HtmlEncode...!!!)
Take a look at the following link to become more familiar with a nightmare called XSS...!!!
XSS Filter Evasion Cheat Sheet - OWASP