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A user submits a search query to my site.
I then take this query and use it in other places, as well as echo'ing it back out to the page.
Right now I'm using htmlspecialchars(); to filter it.
What other steps should I take to prevent XSS, SQL Injection, etc, and things I can't even think of. I want to have all my bases covered.
<?php
$query = $_GET["query"];
$query = htmlspecialchars($query);
?>
Right now I'm using htmlspecialchars(); to filter it.
What other steps should I take to prevent XSS, SQL Injection, etc, and things I can't even think of. I want to have all my bases covered.
To cover all your bases, this depends a lot. The most straight forward (but unsatisfying) answer then probably is: do not accept user input.
And even this may sound easy, it is often not and then forgotten that any input from a different context has to be considered user input. For example when you open a file from the file-system, e.g. reading records from a database or some other data from some other system or service - not only some parameter from the HTTP request or a file upload.
Thinking this through, in context of PHP, this normally also includes the PHP code itself which is often read from disk. Not SQL, just PHP code injection.
So if you really think about the question in such a generally broad way ("etc"), the first thing you need to ensure is you've got a defined process to deploy the application and have checks and marks in place that the files of the deployment can't be tempered with (e.g. a read-only file-system). And from the operational side: You can create and restore the known state of the program within seconds with little or no side effects.
Only after that you should start to worry about other kind of user-input. For which - to complete the answer - you should only accept what is acceptable.
A user submits a search query to my site.
Accepting a search query is the higher art of user input. It involves (free form) text which tends to become more and more complex after every other day and may also include logical operators and instructions which may require parsing which involves even more components that can break and can be exploited by various kind of attacks (and SQL Injection is only one of those, albeit still pretty popular). So plan ahead for it.
As a first level mitigation, you can question if the search is really a feature that is needed. Then if you have decided on that, you should outline which problems it generally creates and you should take a look if the problems are common. That question is important because common questions may already have answers, even common answers. So if a problem is common, it is likely that the problem is already solved. Leaning towards an existing solution then only bears the problem to integrate that solution (that is understanding the problem - you always need to do it and you learn soon enough, one or two decades is normally fine - and then understanding the specific solution as you need to integrate it).
For example:
$query = $_GET["query"];
$query = htmlspecialchars($query);
is making use of variable re-use. This is commonly known to be error prone. Using different variable names that mark the context of its value(s) can help:
$getQuery = $_GET["query"];
$htmlQuery = htmlspecialchars($getQuery);
It is then more visible that $htmlQuery can be used in HTML output to show the search query (or at least was intended for it). Similar to $_GET["query"], it would make totally visible that $getQuery would not be appropriate for HTML output and its string concatenation operations.
In the original example, this would not be equally visible for $query.
It would then perhaps also made visible that in other than HTML output contexts, it ($htmlQuery) is not appropriate either. As your question suggests you already imagine that $getQuery or $htmlQuery is not appropriate to deal with the risks of an SQL Injection for example.
The example is intentionally verbose on the naming, real-life naming schemes are normally different and wouldn't emphasize the type on the variable name that much but would have a concrete type:
try {
...
$query = new Query($_GET["query"]);
...
<?= htmlspecialchars($query) ?>
If you already read up to this point, it may become more clear that there hardly can not be any one-size-fits-it-all function that magically prevents all attacks (apart from muting any kind of user-input which sometimes is equal to deleting the overall software in the first place - which is known to be safe, perhaps most of all for your software users). If you allow me the joke, maybe this is it:
$safeQuery = unset($_GET["query"]); // null
which technically works in PHP, but I hope you get the idea, it's not really meant as an answer to your question.
So now as it is hopefully clear that each input needs to be treated in context of input and output to work, it should give some pointers how and where to look for the data-handling that is of need.
Context is a big word here. One guidance is to take a look if you're dealing with user data (user input) in the input phase of a system or in the output phase.
In the input phase what you normally want to do is to sanitize, to verify the data. E.g. is it correctly encoded? Can the actual value or values the data represents (or is intended to represent) be safely decoded? Can any actual value be obtained from that data? If the encoding is already broken, ensure no further processing of that data is done. This is basically error handling and commonly means to refuse input. In context of a web-application this can mean to close the connection on the TCP transport layer (or not send anything (back) on UDP), to respond with a HTTP Status Code that denotes an error (with or without further, spare details in the response body), with a more user-friendly hypertext message in the response body, or, for a HTML-Form dedicated error messages for the part of the input that was not accepted and for some API in the format that the client can consume for the API protocol to channel out errors with the request input data (the deeper you go, the more complicated).
In the output phase it is a bit different. If you for example identified the user-input being a search query and passed the query (as value) to a search service or system and then get back the results (the reflected user input which still is user input), all this data needs to be correctly encoded to transport all result value(s) back to the user. So for example if you output the search query along with the search results, all this data needs to be passed in the expected format. In context of a web application, the user normally tells with each request what the preferred encoding of the response should be. Lets say this is normally hypertext encoded as HTML. Then all values need to be output in a way/form so that these are properly represented in HTML (and not for some error as HTML, e.g. a search for <marquee> would not cause the whole output to move all over the page - you get the idea).
htmlspecialchars() may do the job here, so might by chance htmlentities(), but which function to use with which parameters highly depends on underlying encoding like HTTP, HTML or character encoding and to which part something belongs in the response (e.g. using htmlspecialchars() on a value that is communicated back with a cookie response header would certainly not lead to intended results).
In the input phase you assert the input is matching your expectations so that you can safely let pass it along into the application or refuse further processing. Only you can know in detail what these requirements are.
In the output phase your job is to ensure that all data is properly encoded and formatted for the overall output to work and the user can safely consume it.
In the input phase you should not try to "fix" issues with the incoming data yourself, instead assume the best and communicate back that there will be no communication - or - what the problem was (note: do not let fool yourself: if this involves output of user input, mind what is important for the output phase of it, there is less risk in just dropping user input and not further process it, e.g. do not reflect it by communicating it back).
This is a bit different for the non-error handling output phase (given the input was acceptable), you err here on the safe side and encode it properly, you may even be fine with filtering the user-data so that it is safe in the output (not as the output which belongs to your overall process, and mind filtering is harder than it looks on first sight).
In short, don't filter input, only let it pass along if it is acceptable (sanitize). Filter input only in/for output if you do not have any other option (it is a fall-back, often gone wrong). Mind that filtering is often much harder and much more error prone incl. opening up to attacks than just refusing the data overall (so there is some truth in the initial joke).
Next to input or output context for the data, there is also the context in use of the values. In your example the search query. How could anyone here on Stackoverflow or any other internet site answer that as it remains completely undefined in your question: A search query. A search query for what? Isn't your question itself in a search for an answer? Taking it as an example, Stackoverflow can take it:
Verify the input is in the form of a question title and its text message that can safely enter their database - it passed that check, which can be verified as your question was published.
With your attempt to enter that query on Stackoverflow, some input validation steps were done prior sending it to the database - while already querying it: Similar questions, is your user valid etc.
As this short example shows, many of the questions for a concrete application (your application, your code) needs not only the basic foundation to work (and therefore do error handling on the protocol level, standard input and output so to say), but also to build on top of it to work technically correct (a database search for existing questions must not be prone to SQL injection, neither on the title, not on the question text, nor must the display of error messages or hints introduce other form of injections).
To come back to your own example, $htmlQuery is not appropriate if you need to encode it as a Javascript string in a response. To encode a value within Javascript as a string you would certainly use a different function, maybe json_encode($string) instead of htmlspecialchars($string).
And for passing the search query to a search service, it may be as well encoded differently, e.g. as XML, JSON or SQL (for which most database drivers offers a nice feature called parameterized queries or more formalized prepared statements which are of great help to handle input and output context more easily - common problems, common solutions).
prevent XSS, SQL Injection, etc, and things I can't even think of. I want to have all my bases covered.
You may already now spot the "error" with this "search query". It's not about the part that there aren't things you or anyone else can even think of. Regardless of how much knowledge you have, there always will be known and unknown unknowns. Next to the just sheer number of mistakes we do encode into software each other day. The one "wrong" perhaps is in thinking that there would be a one-size-fits-it-all solution (even in good intend as things must have been solved already - and truly most have been, but still one needs to learn about them first, so good you ask) and perhaps more important the other one to assume that others are solving your problems: your technical problems perhaps, but your problems you can only solve yourself. And if that sentence may sound hard, take the good side of it: You can solve them. And I write this even I can only give a lengthy answer to your question.
So take any security advice - including the text-wall I just placed here - on Stackoverflow or elsewhere with a grain of salt. Only your own sharp eyes can decide if they are appropriate to cover your bases.
Older PHP Security Poster (via my blog)
I am building website where people can learn to code. I know how the courses are going to be stored, but I need one more thing, Custom Error messages. I want it so the creator of the course can put in some conman error you might make so people who just started not error messages they don't understand. I am trying to make a feature for it so you can type /*/ in the errors and that can mean anything. Let's say you are meant to type: console.log('hi'), but they type: console.log(hi) instead. I want to tell them that they put in the wrong value, not a big error message or just you got something wrong. Basically, I just want to find text that can have anything inside it in a place in a string. How would I do that?
As far i understand your requirement that you want to implement a custom editor which instantaneously prompt the user if there is anything wrong in sense of syntax error. For this you must have to develop a code parser using compiler construction algorithms. You may look for DFA OR NFA for much better understanding of developing a custom code parser. Well, We all know a quote
Don't re-invent the wheel
That's means instead of wasting time and energy on implementing custom parser for end users, you can use the third party open source tools that can be easily embed in your site with all features ready to use. Further you may be interested in following urls.
https://codemirror.net/1/story.html
https://gist.github.com/DmitrySoshnikov/a6c1535ffca1b4056a923a04299e60dc
I am trying to create a scenario that will work every time but I do not know how to deal with the uniquely hashed javascript and CSS. I could not find any answer in the documentation about that.
What I want specifically is the ability to pass a regex into my get but that is not possible since it only takes a string.
.get("/dist/precache-manifest.3efd6185a8d8559962673d45aed7ae98.js")
.headers(headers_0)
I expect a way to be able to somehow get the URL with a regex and then use it in my get above. Is there a way to do that in a Gatling scenario.
I found a way but its a hack and it takes a lot of time I am answering this because someone might want to use this way. However this could be considered a bug.
.get("").queryParam("", _ =>regex("""\/dist\/precache-manifest.[A-Za-z0-9]+.js"""))
.headers(headers_0),
I'm working in a system where there is no document and no jQuery, but
I do have to present html entities in an understandable way. So the trick of putting the string in an element and then taking the .text() won't work.
I need a pure JavaScript solution. The system isn't reachable from the outside, there is no user-input so security is not really an issue.
Thanks for any help, I'm out of ideas (not that I had to many to begin with)...
Perhaps I should clarify, what I am looking for is a function (or pointers to get me pointing in the right direction) which is able to translate a string with substrings that should translate to characters. So it should be able to translate "blah < blahblah" into "blah < blahblah".
There are no additional frameworks I can use other than pure javascript.
UPDATE:
I've got the html4 part working, not extremely difficult, but I have been busy with other things. Here's the fiddle:html4 entities to characters.
You could have done the same with a dictionary with just the characters already in there, but I didn't feel like making such a dictionary. The function is fairly simple but I guess it could do with some refactoring, can't really be bothered at the moment...
This function exists in PHP (htmlspecialchars_decode). As such, you'll find a javascript port from PHPJS. This is based on a very established codebase, and should be better than rolling something on your own.
Edit / Add:
Flub on my part. I didn't read the entities part properly. You want the equiv of html_entity_decode:
http://phpjs.org/functions/html_entity_decode/
Assuming you are using nodejs, cheerio is exactly what you need. I have used it myself a couple of times with great success for off-browser testing of HTML structures returned from servers.
https://github.com/cheeriojs/cheerio
The most awesome part is that it uses jQuery API.
I want to be able to validate a form field called promotional codes, without using a data base.
There are two valid codes and the forms field needs to match either one of these. They are codes like this 'VK2012'.
I've tried the equalto with a hidden form field but this doesn't quite work.
Any suggestions greatly appreciated.
First, the comments are right. You should do this on the server side. Client side validation of this sort really ought to be reserved for the case where you can safely assume that your users are acting in good faith (and as soon as you're talking about things like promotional codes, you cannot assume that). As far as a non-database solution goes, it's ugly and maintains poorly, but you could always hardwire the strings to compare to into the code on the server side. Alternately, for a somewhat less ugly (but somewhat more involved) version, you could put them into config files, which would let you change the codes without recompiling.