Chromium Embedded Framework Forum

by **finder2** » Sun Aug 27, 2023 10:38 am

I need to add JS sripts from Chrome extension after <html> and before <head> to replicate the functionality of some extensions.
OnWebKitInitialized doesn't work for my JS code on my client and i can't use OnContextCreated because document.documentElement is null.
How can I inject JS script before <head>?
Where should I intercept it?

by **KatrinaS** » Sun Aug 27, 2023 11:42 am

Use one of the mechanisms available to Intercept the request such as in request handler, resource handler or similar, download it yourself 'in the raw', add what you need to the html then pass that new html to the browser?

by **magreenblatt** » Sun Aug 27, 2023 1:01 pm

You can use CefResponseFilter to modify the HTML contents on the fly.

by **finder2** » Mon Aug 28, 2023 1:20 am

Thank you guus, for pointing me out. Hope it will work with JS IIFE functions.

by **KatrinaS** » Mon Aug 28, 2023 11:05 pm

I'm unsure if JavaScript in this particular position is going to be interpreted, it's not really a well formed document, but that said browsers in general are pretty fault / form tolerant so good luck with it

by **finder2** » Tue Aug 29, 2023 2:21 pm

KatrinaS wrote:I'm unsure if JavaScript in this particular position is going to be interpreted, it's not really a well formed document, but that said browsers in general are pretty fault / form tolerant so good luck with it

Chrome places its extension with "document_start" right after <head> when i investigated it.

by **finder2** » Thu Nov 02, 2023 3:59 pm

Finally i figured out how to add a JS code to html on the fly, but when I open, for example, google.com it says

Code: Select all: [Report Only] Refused to execute inline script because it violates the following Content Security Policy directive: "script-src 'nonce-7FHIekf3Jv342WbLuHw_8Q' 'strict-dynamic' 'report-sample' 'unsafe-eval' 'unsafe-inline' https: http:". Note that 'unsafe-inline' is ignored if either a hash or nonce value is present in the source list.

I tried to run CEF with

Code: Select all: --disable-web-security=1

to disable CSP, but it didn't help

Any tips, guys?

Another questions...
Can I intercept JS functions from C++ somewhere or can i find a start point in CEF where JS starts implementing its scripts?

by **KatrinaS** » Thu Nov 02, 2023 7:33 pm

Having no idea what / how you are tinkering with (either online, local or whatever) try enabling as much local file access as possible such as adding... disable-site-isolation-trails, allow-universal-access-from-files, allow-file-access-from-files etc etc,, in whatever language you are using's equivalent to CefAppHandlerAdapter / onBeforeCommandLineProcessing

As for the last question. Probably, but all of that's a headache (for me anyway) :lol:

by **finder2** » Sun Nov 05, 2023 2:14 pm

Seems i was able to inject code with JS MutationObserver, i create MutationObserver on OnContextCreated and inject code when DOM is building.

by **KatrinaS** » Mon Nov 06, 2023 7:57 pm

Oh right,, never heard of it

You C/++ guys have some good toys, makes me think my toys are sh*t :lol:

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Can't inject JS Script before <head>

Can't inject JS Script before <head>

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