We are currently implementing the payment flow, and for handling payment details — including card entry and validation — we are utilizing a WKWebView. The webview securely loads the payment provider’s page, ensuring sensitive information such as card numbers are entered and validated directly within the web context.
I’d like to clarify that this change has not yet been released to Production. As part of a feature enhancement to our existing payment flow, we are transitioning to a new payment vendor, SnapPay. While trying to load the SnapPay URL embedded within an iFrame in our iOS app, I observed the following error in the Xcode console. While this error may be generic, I wanted to highlight it:
825a18 - [pageProxyID=7, webPageID=8, PID=67346] WebPageProxy::didFailLoadForFrame: frameID=24, isMainFrame=0, domain=NSURLErrorDomain, code=-999
Upon investigating, we compared the headers from our existing payment URL and SnapPay's URL, and found that SnapPay includes the following Content-Security-Policy (CSP) header: Content-Security-Policy: frame-ancestors ...
"Content-Security-Policy" value="default-src 'self'; script-src 'self' https://hcaptcha.com https://.hcaptcha.com https://code.jquery.com https://www.gstatic.com https://code.jquery.com/jquery-3.3.1.min.js https://test.lightbox.cardx.com/v1/lightbox.min.js https://www.ssa.gov/accessibility/andi/ https://c.evidon.com 'unsafe-inline' 'unsafe-eval'; style-src 'self' https://hcaptcha.com https://.hcaptcha.com https://fonts.googleapis.com/css https://stage.snappayglobal.com/Resource/ https://www.ssa.gov/accessibility/andi/andi.css 'unsafe-inline'; img-src 'self' data: https:; font-src 'self' *.googleapis.com *.gstatic.com ; connect-src 'self' https://demo1.cditechnology.com https:; form-action https://hcaptcha.com https: 'self' *.ipg-online.com secure.bluepay.com https://test.api.lightbox.cardx.com https://3ds-acs.test.modirum.com/ https://demo1.cditechnology.com/; frame-ancestors https://snappaydirect-perf.fiserv.com 'self' file: https: http; frame-src .snappayglobal.com 'self' https://hcaptcha.com https://.hcaptcha.com https: https://www.google.com .ipg-online.com secure.bluepay.com https://.cardconnect.com https://test.api.lightbox.cardx.com/ https://test.lightbox.cardx.com https://paywithcardx.com/payment/auth.cgi securepayments.cardpointe.com *.cardpointe.com https://3ds-acs.test.modirum.com/ https://www.yokohamatire.com http://uat1-txt.ad.portal.texas.gov https://uat1-txt.ad.portal.texas.gov "
After multiple working sessions with the SnapPay team, we were able to confirm that when they disable CSP or remove the frame-ancestors directive, the iFrame loads successfully within our app. However, SnapPay cannot change on their CSP.
To enable the iFrame to load in the iOS app, we added the following line of code: webView.configuration.preferences.setValue(true, forKey: "allowFileAccessFromFileURLs").
This resolved the issue with loading the iFrame. Note: the file being loaded is a local .html file,. Before submitting this update to the App Store, I’d like to confirm whether this usage of allowFileAccessFromFileURLs is acceptable for App Store review.
I wanted to confirm that with this change is there a security concern for WKWebview?