Ok, im just lost. I opened an electron start app and added one simple code, to console log on button press. The function is in a file renderer.js and in being called in in my index.html. Why when I press the button
I get this message ....
Refused to execute inline event handler because it violates the following Content
Security Policy directive: "script-src 'self'". Either the 'unsafe-inline' keyword, a
hash ('sha256-...'), or a nonce ('nonce-...') is required to enable inline execution.
Why would I not be allowed to execute something inline? An external source seems more vulnerable. Can anyone clear this up for me please?
Content Security Policy is using to avoid XSS based attacks in browser.In electron the background is running in a chrome engine, so the code is actullay running in a chromium browser.This browser is prone to all security issues that a browser is having
What is Content-Security-Policy?
Content-Security-Policy is the name of a HTTP response header that modern browsers use to enhance the security of the document (or web page). The Content-Security-Policy header allows you to restrict how resources such as JavaScript, CSS, or pretty much anything that the browser loads.
you can add the following code at the top of HTML to avoid the content security issue. this new header will allow the inline code to execute
<meta http-equiv="Content-Security-Policy" content="script-src 'self';">
What this meta tag will do ?
Allows
With the above CSP policy, the following are allowed to load and execute in the browser:
<!-- allowed by 'self' -->
<script src="/js/some-file.js"></script>
<!-- allowed by https://js.example.com -->
<script src="https://js.example.com/file.js"></script>
Blocks
The Example Policy above will block the following from loading or executing in the browser:
<script src="https://attacker.example.com/file.js"></script>
Related
I have a Node/React app and get this error when I refresh the page in my production build, for all routes apart from "/", and a blank page is shown.
Refused to execute inline script because it violates the following
Content Security Policy directive: "script-src 'self'". Either the
'unsafe-inline' keyword, a hash
('sha256-eE1k/Cs1U0Li9/ihPPQ7jKIGDvR8fYw65VJw+txfifw='), or a nonce
('nonce-...') is required to enable inline execution.
Page refreshing functions normally in my local build.
I have seen a similar issue here:
Inline script because it violates the following Content Security Policy directive: "script-src 'self'"
and so have tried the INLINE_RUNTIME_CHUNK=false, which made no difference, and when I tried to add the cross-env, I got a CORS error. I don't really understand why cross-env helps or why it could be causing my requests to be blocked by CORS.
Does anyone have any advice? Or let me know if you need more information about my setup.
Thanks!
I am trying to load jQuery in Electron (v. 16.0.0), but I get this error:
Inside the head element I have included this line:
<meta http-equiv="Content-Security-Policy" content="script-src 'self';">
Also, inside the body element, I am trying to load jQuery like this:
<script src="https://code.jquery.com/jquery-3.6.0.min.js" integrity="sha256-/xUj+3OJU5yExlq6GSYGSHk7tPXikynS7ogEvDej/m4=" crossorigin="anonymous"></script>
I have tried so many ways to find a solution for this, but to no avail. Previously, I also tried to load jQuery like this, but it gave me a similar error, shown below:
<script>window.$ = window.jQuery = require('./libraries/jQuery/jquery.min.js');</script>
Answers to a related question did not work for me either. What should I do?
The reason Electron, or any other Web browser that implements Content Security Policy, for that matter, would correctly refuse to load a script from an arbitrary origin (URL), or even an "inline" script (e.g. script text inside a script element), is because your security policy is explicitly specified to deny such attempts, with that meta element you said you added:
<meta http-equiv="Content-Security-Policy" content="script-src 'self';">
Why did you add it? Was it there by someone else's hand? Why is it there? It's the reason why Electron denies loading of the scripts in question.
The value of the content attribute above has the effect of instructing Electron to only allow loading scripts from the same origin as the origin of the document containing the meta element. That effectively excludes every other origin like https://code.jquery.com and inline scripts (which have to be allowed explicitly in this case because self denies these). Basically, the value is to be interpreted as "only allow loading scripts from the same site". Inline scripts are not considered as "same site".
Simpler put, you yourself prohibit loading of scripts from the kind of locations you then attempt to use, with that meta element.
You need to learn how Content Security Policy mechanism works and applies in your case. You will have to decide whether you want to allow loading of scripts from domains like code.jquery.com, or whether, for example, you will only want to allow loading scripts from your website, which in turn will probably necessitate you copying the JQuery library you want to use to be served by your website. You also will have to decide if you want to allow "inline" scripts on your site, for whatever reason you may consider necessary.
The security policy mechanism itself is very useful, don't shy away from it, it's there for a reason -- to help you prevent abuse of your site users by malicious scripts loaded by other malicious scripts or mechanisms. But you need to use it correctly, obviously.
You have 2 issues because of jQuery:
script-src 'self' does not allow to load script from https://code.jquery.com/jquery-3.6.0.min.js, that's why you observe Refused to load the script 'https://code.jquery.com/jquery-3.6.0.min.js'... error.
You have to adjust your CSP at least as script-src 'self' https://code.jquery.com;.
After page loads, the jQuery pick up all scripts having $() and place them into one inline script in the <head> section. That's why you observe Refused to execute inline script ... error.
This inline script can be resolved with either 'unsafe-inline' or 'unsafe-eval' or 'nonce-value'(for jQuery > 3.4).
Allowing 'unsafe-inline' is a very harmful advice, since such CSP will not protect against XSS at all (https://youtu.be/zlH_bBQMgkc?t=717).
Also Electron does not have the technical ability to refresh the 'nonce' value.
Therefore, the most secure CSP you can do is:
script-src 'self' 'unsafe-eval' https://code.jquery.com;
or much better:
default-src 'self'; script-src 'self' 'unsafe-eval' https://code.jquery.com;
Note: Contrary to a common misconception, 'self' does not mean the Same Origin Policy, CSP interprets 'self' much more broadly.
I have a single page application (built in .net core MVC 2.2), where html section are loaded on the fly.
On main document, added CSP policy with a dynamically generated header looks like:
Content-Security-Policy: script-src 'self' 'nonce-I64vb811BxRNGV9Xf0pM'
Then comes a page section loaded via jquery ajax load function. page section contains a script (from src) with a nonce. Page section served with CSP header looks like
Content-Security-Policy: script-src 'self' 'nonce-ci5TQsyidT8x2jwBLRHS'
all good but browsers (chrome, safari blocking the script), with message:
jqueryscriptsbundle.js:formatted:43 Refused to execute inline script
because it violates the following
Content Security Policy directive: "script-src 'self' 'nonce-I64vb811BxRNGV9Xf0pM'
So browser is comparing nonce of script i.e. ci5TQsyidT8x2jwBLRHS with root/main page nonce value I64vb811BxRNGV9Xf0pM hence script blocked.
Is it correct behavior ? What can I do to make it work?
Your initial CSP, loaded with the page, provides a nonce. What you're trying to do is add another nonce, via Ajax, after the initial page load. CSP explicitly doesn't allow this; that's not a bug -- it's the entire point.
What you might do is allow a script-src of strict-dynamic. This allows you to authorize a script, and anything loaded by that script is also authorized. See https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/script-src
I'm working on a Javascript App food2fork. But I get an error when AJAX call API promise fulfilled and render the results (Recipes). But when I click one of them it moves to the next page and say
Cannot GET /47746
and give an error on the console
Refused to load the image 'http://localhost:8080/favicon.ico' because it violates the following Content Security Policy directive: "default-src 'none'". Note that 'img-src' was not explicitly set, so 'default-src' is used as a fallback".
How to get rid of this kind of error?
This is because a Content Security Policy (CSP) header is set somewhere in your application.
Content Security Policy (CSP) is an added layer of security that helps
to detect and mitigate certain types of attacks, including Cross Site
Scripting (XSS) and data injection attacks./.../
A CSP compatible browser will then only execute scripts loaded in
source files received from those allowlisted domains, ignoring all
other script (including inline scripts and event-handling HTML
attributes).
As an ultimate form of protection, sites that want to never allow
scripts to be executed can opt to globally disallow script execution. [edit: hence the "default-src 'none'" policy]
More on CSP: https://developer.mozilla.org/en-US/docs/Web/HTTP/CSP
You can create a CSP with online tools, like
https://report-uri.com/home/generate
https://www.cspisawesome.com
A CSP with "default-src 'none'" means that nothing can be displayed/run on your domain - you have to "whitelist" the services/content that you allow (default-src is a fallback for other resource types that do not have policies of their own, so you have it set like none, then you have to add sources that are explicitly allowed).
A policy is described using a series of policy directives, each of
which describes the policy for a certain resource type or policy area.
WHAT YOU CAN DO
In your case, you may need a policy something like:
"default-src 'none'; img-src 'self'".
I'm pretty sure though, that as you go forward you'll need more rules, so check out the sources and the online CSP generators, so you won't have a hard time.
OR you may
Remove the CSP (not advised - it's a security measure)
For development purposes, you may set Content-Security-Policy-Report-Only (this way the CSP does not stop your content to be displayed/run, but shows "what would have been done, if not set to only to report the problems". Don't forget to handle this in production environment!)
REFERENCE
CSP reference: https://content-security-policy.com
More on CSP: https://scotthelme.co.uk/content-security-policy-an-introduction/
I have a page that I set the script-src of the content security policy like this:
script-src 'self' *.uservoice.com *.intuit.com ajax.googleapis.com localhost:*
When I load the page with a hard-coded inline script I have created myself to test, it is blocked like expected:
Refused to execute inline script because it violates the following
Content Security Policy directive: "script-src 'self'
*.uservoice.com *.intuit.com ajax.googleapis.com localhost:* ". Either the 'unsafe-inline' keyword, a hash ('sha256-...'), or a nonce
('nonce-...') is required to enable inline execution.
However, when I insert a new script tag dynamically, the script isn't blocked, for example, this still executes:
$("body").append("<script>alert('xss');</script>")
I am using Chrome as the browser here for testing. I was hoping that this script would be blocked as well, since that would really help to prevent xss. Is there something I can change to block this type of script injection as well?
The script you add with append or innerHtml won't be executed unless you use eval(). So it's not violating CSP.
Although this may look like a cross-site scripting attack, the result is harmless. HTML5 specifies that a tag inserted via innerHTML should not execute. 1
See script elements inserted using innerHTML do not execute when they are inserted.