Webpack has a feature of adding nonce to all scripts it loads.
To activate the feature set a __webpack_nonce__ variable needs to be included in your entry script.
Entry file in react app geneated by create react app by defaulty is index.js. So all I need to do is add in entry file:
// ...
__webpack_nonce__ = 'c29tZSBjb29sIHN0cmluZyB3aWxsIHBvcCB1cCAxMjM=';
// ...
And last thing is to enable webpack CSP.
Please note that CSPs are not enabled by default. A corresponding header Content-Security-Policy or meta tag needs to be sent with the document to instruct the browser to enable the CSP. Here's an example of what a CSP header including a CDN white-listed URL might look like: Content-Security-Policy: default-src 'self'; script-src 'self' https://trusted.cdn.com;
However, I got error
'__webpack_nonce__' is not defined
I've tried to declare nonce. Still doesn't work.
webpack_nonce is specified in the entry file and not in the configuration.
So, what I am doing wrong? Maybe docs are missing some key info about that topic? How to enable CSP feature in webpack for React app?
If you are using create-react-app then it may be ESLint that is reporting the error.
Try disabling it for the line:
__webpack_nonce__ = 'c29tZSBjb29sIHN0cmluZyB3aWxsIHBvcCB1cCAxMjM='; // eslint-disable-line no-undef
Related
I have a React App using creact-react-app and Material-UI.
I'm trying to enable CSP headers for my react web app inside AWS CloudFront.
I dont know why, but I keep getting these empty inline "data-emotion" style tags ..
I've set the .env as follows:
ESLINT_NO_DEV_ERRORS=true
INLINE_RUNTIME_CHUNK=false
IMAGE_INLINE_SIZE_LIMIT=0
Try setting the style-src directive as "style-src 'self' 'sha256-2NO5...' 'sha256-47DE...';" with the full hashes as provided in the error messages.
I recently added CSP header to my project.
At the same time, I am also using PDFTron webviewer in my project.
As you know, PDFTron webviewer is rendered in an iframe and after adding CSP headers, I'm getting below error - related frame-ancestors.
Question1 is how can I add a frame-ancestors header to the PDFtron webviewer to bypass this error?
Question2 is the second error related with cross domain is not fixable by adding my domains to configorigin.txt, is it related with the csp header setting?
To Question1: Just change frame-ancestors 'none' to the frame-ancestors 'self' (or to frame-ancestors localhost:* if in your particular browser the 'self' token does not cover a localhost:port_number) to allow embedding PDF webviewer.
To Question2: I think the second error is CSP-related (side effect of CSP blocking) because localhost should not be a cross-origin resource since main page is loaded with the same host name and port number http://localhost:3000.
I get the following error in the Chrome's web console on my deployed React app:
Refused to frame 'https://www.youtube.com/' because it violates the following Content Security Policy directive: "default-src 'self'". Note that 'frame-src' was not explicitly set, so 'default-src' is used as a fallback.
However, I have specified frame-src in my index.html like in the following snippet:
<meta http-equiv="Content-Security-Policy" content="frame-src https://www.youtube.com/">
The source for the error is a YouTube embed, and with the meta tag in place the embed works fine on localhost. What could cause this error only to appear on a deployed React app?
Fixed it by adding Content-Security-Policy header on the server. So it wasn't an issue with the front-end code after all.
noob here.
Creating a PWA React app using create-react-app and running into the CSP issue regarding default set to none and no img setting to override it.
Have searched for and tried many, many helpful answers for this exact problem but have not hit upon the one that will work for my app.
Maybe I just need a second pair of eyes?
The error is:
Cannot GET /
The console tells me this:
Failed to load resource: the server responded with a status of 404 (Not Found)
localhost/:1 Refused to load the image 'http://localhost:3002/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.
localhost/:1 Failed to load resource: the server responded with a status of 404 (Not Found)
Screenshot of server.js where I tried to implement express-csp-header:
server.js
Screenshot of index.html to show the added images and that there is no meta tag for CSP:
index.html
I have tried adding the tag as advised elsewhere.
I tried every other suggestion from stackoverflow that I could find.
Please advise.
----EDIT--- I guess what I need to know is how to override the CSP that comes with webpack as part of Create-React-App because the console error message says that 'img src' is NOT defined so it defaulted to "default src", which is set to 'none'. I believed I have installed express-csp-header correctly and have 'img src' set correctly, why doesn't the browser find that?
----Another EDIT--- Here all this time I was thinking that webpack must be where the browser is getting the "default-scr: NONE" referred to in the error message. I just searched all of the files in react-script, which is where webpack config files live, and don't find any occurance of "default-scr: NONE". Is it an Express setting? Why am I dealing with CSP with this CRA app and not the other dozen I created the same way? Pulling my hair out.
Maybe I just need a second pair of eyes?
Yeah, it is difficult to find a black cat in a dark room, especially if it is not there.
Refused to load the image 'http://localhost:3002/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.
This is a great example of a misleading diagnostic message. Your issue have nothing to do with Content Security Policy (CSP).
Just place favicon.ico file into %PUBLIC_URL% folder and add into <head> section:
<link rel="icon" type="image/x-icon" href="%PUBLIC_URL%/favicon.ico">
All nitty-gritty is here. Briefly - browser by default tries to get favicon from the root of website, since you do not set right <link rel="icon" tag. There is no favicon there, so 404 Not Found occurs (anyway Express do not serve root folder by default).
Your CSP is published on "200 OK pages" only, so Express by default uses its own default-src 'none' for nonexistent pages (with status codes 404/403/500/etc).
This can really be confusing to anyone.
PS: Quite possible that the presence of %PUBLIC_URL% means you do not set PUBLIC_URL / homepage properly, because it should be substituted by a real folder/path. I just use your notation in the <link rel="icon" tag above.
PPS: I think if you add a custom error pages handler, it help to avoid similar misleading diag (code example you can take here).
UPDATE:
Cannot GET /
means webpack dos not know what page to show - defServer{...} output{...} sections misconfigured or wrong router(). Therefore you get 404 Not Found page.
You could to look in the Developer tools is the Status Code 404/200 and which Content-Security-Policy HTTP header you have really got (here is a tutorial).
In case of 404 Not Found, webpack shows built-in default error page (since you do not created your own). This error page is served with default webpack's CSP, not yours (your CSP will be published on pages with 200 OK status code only).
I just searched all of the files in react-script, which is where
webpack config files live, and don't find any occurance of
"default-scr: NONE"
AFAIK, webpack-dev-server uses a finalhandler which rejects /favicons on 404 pages exactly with the same issue you have. In this way default-src: 'none' should be in node_modules/finalhandler/index.js.
Why am I dealing with CSP with this CRA app and not the other dozen I
created the same way?
Previously finalhandler has default-src 'self' so /faficons was not blocks by CSP. But after this thread: default-src should be 'none' in finalhandler at May 2019 - things changed.
I guess you issue is not CSP related, it's just have misconfigured defServer{...} or output{...} (some path: __dirname + 'public/' or publicPath: points to a wrong dir).
CSP error is only a symptom (bad thing it's a false symptom) of the disease, but we need to treat a cause but not symptoms.
PS: I think instead of %PUBLIC_URL%/favicon.ico it should be http://localhost/favicon.ico in HTML, it's something misconfigured here too.
I am using the INLINE_RUNTIME_CHUNK=false variable in my create-react-app build and it's setting a CSP directive at build time (building on Heroku) for img-src of 'self' data:. I need to modify this to host profile pics coming in from the IDP i'm using, so that img-src directive needs to be changed.
How can I change this as part of the build process? Or should I override the whole CSP string with a meta tag in index.html? Is there a way to configure this on the build step as part of the heroku-postinstall command?