I am serving a HTML page in my node.js server with express.public() function.
and i added this into my html page:
<script src="https://cdn.jsdelivr.net/npm/vue#2/dist/vue.js"></script>
And Chrome gaves me a Content-Security-Policy to me.
I used this middlewares in my Node index.js
app.use(morgan('tiny'));
app.use(helmet());
app.use(cors());
app.use(express.json());
app.use(express.static("./public"));
My application headers:
Content-Security-Policy: default-src 'self';base-uri 'self';block-all-mixed-content;font-src 'self' https: data:;frame-ancestors 'self';img-src 'self' data:;object-src 'none';script-src 'self';script-src-attr 'none';style-src 'self' https: 'unsafe-inline';upgrade-insecure-requests
How can i add this script without any SecurityPolicy
SOLVED
I remove "Helmet" from my project. Helmet is blocking the all cdn and scripts other then absolute domain.
Content Security Policy is set in the html file being served or by the software serving the html (e.g Nginx, Apache).
At the moment you have: default-src 'self', this means you are telling the browser that it is only able to make requests to its own domain.
You need to add https://cdn.jsdelivr.net/npm/vue#2/dist/vue.js to this list of domains it can access.
That would be something like:
Content-Security-Policy: default-src 'self';script-src 'self' https://cdn.jsdelivr.net/npm/vue#2/dist/vue.js; base-uri 'self';block-all-mixed-content;font-src 'self' https: data:;frame-ancestors 'self';img-src 'self' data:;object-src 'none';script-src-attr 'none';style-src 'self' https: 'unsafe-inline';upgrade-insecure-requests
So default-src: self sets the default to restrict requests to only your own domain.
script-src 'self' https://cdn.jsdelivr.net/npm/vue#2/dist/vue.js overrides this and says specifically for scripts restricts request to only your domain and that url.
This has lots of details and examples:
https://content-security-policy.com
In addition to what silent-tiger said, I think you should first find out which middleware is responsible for adding this content policy. Do this by disabling all middleware (except express static) and then add the other middlewares one by one until you see the Content Secutity Policy headers again.
If you found which middleware is responsible, then you know which middleware you should configure.
Related
I've tried to set CSP header for my site to load data from trusted resources
CSP blocks my local JS files. here is my nuxt.config.js:
const self = 'localhost:*'
render: {
csp: {
reportOnly:false,
addMeta: true,
policies: {
'default-src': [self],
'script-src': [self, 'unsafe-inline','strict-dynamic'],
'style-src': [self,"'unsafe-inline'"],
'img-src':[self,'data:'],
'object-src':[self,'self']
}
}
},
Blocked files:
http://localhost:3500/_nuxt/runtime.js
http://localhost:3500/_nuxt/layouts/default.js
http://localhost:3500/_nuxt/pages/index.js
http://localhost:3500/_nuxt/commons/app.js
http://localhost:3500/_nuxt/vendors/app.js
http://localhost:3500/_nuxt/app.js
The error:
Refused to load the script '<URL>' because it violates the following Content Security Policy directive: "script-src 'sha256-6SIdoCBgtiLdpIihMzGUvd5OCiaDdcIHhB8Tzkn9l8M='". Note that 'script-src-elem' was not explicitly set, so 'script-src' is used as a fallback.
It's header request shown in network tab for more details, It's strange but one time it gets same js file and one time it gives the error...
Examples below from mdn docs. Guess you problem can be solved by one of them. Please refer for more examples here
Example 1
A web site administrator wants all content to come from the site's own origin (this excludes subdomains.)
Content-Security-Policy: default-src 'self'
Example 2
A web site administrator wants to allow content from a trusted domain and all its subdomains (it doesn't have to be the same domain that the CSP is set on.)
Content-Security-Policy: default-src 'self' trusted.com *.trusted.com
Example 3
A web site administrator wants to allow users of a web application to include images from any origin in their own content, but to restrict audio or video media to trusted providers, and all scripts only to a specific server that hosts trusted code.
Content-Security-Policy: default-src 'self'; img-src *; media-src media1.com media2.com; script-src userscripts.example.com
Here, by default, content is only permitted from the document's origin, with the following exceptions:
Images may load from anywhere (note the "*" wildcard).
Media is only allowed from media1.com and media2.com (and not from subdomains of those sites).
Executable script is only allowed from userscripts.example.com.
I changed addMeta to false and problem solved!
I'll explain the reason later
const self = 'localhost:*'
render: {
csp: {
reportOnly:false,
addMeta: false,
policies: {
'default-src': [self],
'script-src': [self, 'unsafe-inline','strict-dynamic'],
'style-src': [self,"'unsafe-inline'"],
'img-src':[self,'data:'],
'object-src':[self,'self']
}
}
},
I want to access a website using javascript. but I am getting the following error in the console.
Refused to connect to 'https://example.com' because it violates the following Content Security Policy directive: "default-src 'self'". Note that 'connect-src' was not explicitly set, so 'default-src' is used as a fallback.
I have added the following meta tag in the index.html,
meta http-equiv="Content-Security-Policy" content="connect-src 'self' http://example.com;" />
Isn't this the right way to add CSP? please help.
You already have one CSP published with the default-src 'self' policy. Quite possible it was done via HTTP header.
Check the Helmet middleware settings in case of NodeJS server, or Header set in the .htaccess file in case on Apache server. In case of Nginx it can be add_header in the config.
By adding <meta> tag you just publish a second CSP, which does not overrides the first one. 2 CSPs works subsequently - all sources should pass both CSP.
Figure out where CSP is publushed and add connect-src 'self' http://example.com; there.
When building a web app with separated frontend and backend (no server side rendering) I still want to make use of CSP nonce. Usually the CSP header and the html should contain the same nonce, which is no problem with SSR but seems to be impossible without SSR.
Now I thought of a different way to make use of the nonce without SSR:
Server: Besides sending the nonce with the CSP header, also send it as a cookie (still changing for every request!) This also seems to be a common approach for CSRF
UI: instead of including the <script> which needs a nonce directly inside the html, rather load it dynamically from my own script:
const script = document.createElement('script')
script.setAttribute('src', 'https://example.com')
script.setAttribute('data-csp-nonce', getCspNonceFromCookie())
document.head.appendChild(script);
Is this a valid approach for this problem? Are there security concerns?
Your solution works. One of my projects does it in a similar way. But you should set a nonce attribute instead of data-csp-nonce.
script.setAttribute('nonce', 'THE-GENERATED-NONCE')
So the script tag looks like:
<script nonce="jETnT70lr0T3Hw4b5WeCjuJ421a3kcBl">
// ...
</script>
This is only secure when the headers, send by the server, includes already content-security-policy which denies external scripts. E.g.:
content-security-policy: default-src 'self'; script-src 'self' 'nonce-jETnT70lr0T3Hw4b5WeCjuJ421a3kcBl'; img-src 'self' data:; object-src 'none'
I am creating a web app using the mean stack in angular 6 but I am getting below error message on the browser console.
"Refused to load the font '<URL>' because it violates the following
Content Security Policy directive: "default-src 'self'". Note that
'font-src' was not explicitly set, so 'default-src' is used as a
fallback."
Code:
getUsers() {
return this._http.get("/api/users")
.pipe(map(result => this.result = result.json().data));
}
Content security policy is a way for modern browsers, to define a set of restrictions when loading remote resources.
Response headers from the HTTP protocol can set those policies:
Content-Security-Policy header (official), X-Content-Security-Policy (supported by Mozilla Firefox and IE10) and X-WebKit-CSP (supported by Google Chrome and Safari) HTTP response headers with the list of Content Security Policy directives. (from seckit drupal module)
You can set different policies to different types of elements in the DOM (e.g <img>, <script>, <object>, <embed>, <iframe> and so on...), to restrict requests that originates from that element.
So you need to change 'self' to one of the following:
'none' - block content from any source
'self' - allow content only from your domain
'unsafe-inline' - allow specific inline content (note, that it is supported by a subset of directives)
'unsafe-eval' - allow a set of string-to-code API which is restricted by default (supported by script-src directive)
Wildcards (*) are allowed:
* - load content from any source
*.example.com - load content from example.com and all its subdomains
example.com:* - load content from example.com via any port. -
Otherwise, it will use your website default port
Adding 'self' and data: to the font-src works for me.
Content-Security-Policy: font-src 'self' data:;
font-src reference doc from MDN
The Content-Security-Policy header is set by your api. Check your api response for its value.
As per the error, I think your fonts are loaded from a different domain than your application domain. Unless your api whitelists that domain, your browser will not load the font.
Example:
Content-Security-Policy: font-src https://example.com/
just close all browser, clear cache and restart VSC or your code editor. Ir worked fro me.
I have the Content Security Policy:
default-src 'none';
style-src 'self';
script-src 'self' https://www.google-analytics.com;
img-src 'self' https://www.google-analytics.com;
connect-src 'self';
On my page I have put the inline GA code into an async script:
<script src="/javascript/ga.js" async></script>
This causes a CSP error:
Refused to load the script 'data:application/javascript;base64,KGZ1bmN0aW9uKCkgewoJLy8gaHR0cHM6Ly9kZXZl…07Cgl9OwoJZ2EucmVtb3ZlID0gbm9vcGZuOwoJd2luZG93W2dhTmFtZV0gPSBnYTsKfSkoKTs=' because it violates the following Content Security Policy directive: "script-src 'self' https://www.google-analytics.com".
Is there any way to serve this script from a JS file, and if not how would I need to change the CSP?
Google Analytics is CSP-compatible. The base64-encoded data: blob OP is seeing is being injected by the uBlock Origin extension. To verify, disable it/try incognito. IIRC, this is due to an "experimental/unbreak" setting in the extension.
Please resist the temptation to whitelist data: in script-src. That would make the policy completely useless for XSS mitigation, since an attacker could just inject <script src="data:text/javascript,alert(1)"></script> to execute Javascript.
Please see Michele Spagnuolo's answer and upvote.
This is caused by uBlock Origin and it is because data URLs are not whitelisted:
script-src data:;
There is no point in doing this as this could leave your application vulnerable should untrusted data be used as URLs anywhere within your application, or if the attacker can inject tags that use such URLs. This of course depends on the injection point and which characters are allowed.
Of course you should be whitelisting any user entered URLs (e.g. make sure they start with http:// or https://), however as CSP is defence-in-depth measure you probably don't want to weaken it too much.
The upshot is that you're weakening your CSP by doing this in order to prevent a CSP report or error from being triggered.