Sure: I am required to implement HPKP (aka. Public Key Pinning Extension for HTTP) as defined in RFC 7469 which is not supported out of the box (cf. FB5986841). Additionally I have to secure the first-ever connection as well by supporting preloaded pins, but I cannot use Identity Pinning (cf. thread and FB12333846). So I have to build everything from scratch.

I see. However, doing this: Leave ATS enabled. Intercept the server trust authentication challenge (NSURLAuthenticationMethodServerTrust). Apply your extra checks. Complete the challenge with .performDefaultHandling. causes the trust evaluation to be performed after the extra checks, correct? What if I wanted to have the system check be done first - then I would to resort to calling SecTrustEvaluate myself?

Thanks. Does that mean the example code if checkValidity(of: serverTrust) { let credential = URLCredential(trust: serverTrust) completionHandler(.useCredential, credential) } does not perform trust evaluation?

FWIW, the resolution of the feedback I filed was basically "works as designed".

This does not actually symbolicate the crash log for me. I filed FB13543963 about this.

FWIW: If so, the next step is to confirm that the data and its signature made it to your server intact. On both the iOS and server side, generate an independent hash of the data and the signature and check that they match. Turns out this was the issue, the cause being the same as the one discussed in this thread. But thanks anyway.

@eskimo I am not really getting anywhere with this so far other than that I can confirm the problem still persists in yesterday's beta 7. Would it be helpful if I opened a DTS incident for this?

Thank you for the clarification. I had hoped, though, that there was a way to proceed (the certificate the SPKI fingerprint from the Info.plist belongs to may since have expired, but the app may have knowledge of the current certificate's SPKI hash).

For the record: I suspect that you may be able to do this using one of the data representations, but I’ve not investigated that in depth. I tried converting a Keychain key to a CryptoKit key by utilising SecKeyCopyExternalRepresentation(_:_:), but as the documentation suggests that does not work: The operation couldn’t be completed. (OSStatus error -4 - export not implemented for key <SecKeyRef:('com.apple.setoken') (which should be errSecUnimplemented).

Thanks Quinn. Would it be possible then for someone other than Apple to create a profile (with a payload unrelated to logging) that auto-expires after installation?

Thanks Quinn, I did as you suggested (FB12036482).

I dug a little deeper (thanks, Quinn!) and found two possibly related errors in the system log. errSecNoSuchAttr seems to be caused by error:[-25303] Error Domain=NSOSStatusErrorDomain Code=-25303 "attribute u_CredRef not found in class keys" UserInfo={numberOfErrorsDeep=0, NSDescription=attribute u_CredRef not found in class keys} while errSecAuthFailed seems to be a fallout from evaluateAccessControl on LAContext[5448:4] cid:17 returned Error Domain=com.apple.LocalAuthentication Code=-1009 "ACL operation is not allowed: 'oe'" UserInfo={NSDebugDescription=ACL operation is not allowed: 'oe', NSLocalizedDescription=Vorgang ist nicht zulässig.} I filed this as FB11884381, FWIW.

Update: The documentation for SecItemUpdate includes the following w.r.t. the attributesToUpdate dictionary: Only real keychain attributes are permitted in this dictionary (no "meta" attributes are allowed.)  It is unclear (at least to me) what those "meta" attributes may be. Is kSecAttrAccessControl maybe one of them?

Thanks Quinn, here its is: https://developer.apple.com/forums/thread/720592

Have you tried calling  SecItemUpdate to change the  kSecAttrAccessControl value on the private key item? I'm currently struggling trying to do just that in a context where I have a private key inside the Secure Enclave further protected by an application password which I want to change. I have been unsuccessful getting the queryand attributesToUpdate dictionaries right though, with SecItemUpdate returning either errSecParam or errSecNoSuchAttr. Am I on the right track here or am I trying to do something that is not possible?