Oh well... This does indeed work. The remark "You must import this API explicitly." completely threw me off. Thanks Quinn!

I have been watching the logs closely during on of the failing builds and I see codesign report a "UNIX error exception: 17" (EEXIST maybe?) followed by several CSSM errors (e.g. CSSMERR_DL_DATASTORE_DOESNOT_EXIST) before xcodebuild reports a "UNIX error exception: 22" (EINVAL?). Does that ring any bells?

For the record: It seems that the problem was caused by xcodebuild not waiting for the pre-action script to complete before proceeding with the build. In that case the entitlements file was not present at the location pointed to by CODE_SIGN_ENTITLEMENTS (it is in fact not under version control there, it is instead copied there by the pre-action script and being gitignored afterwards). A reboot of the Jenkins node was enough to remedy the problem - at least for the time being. The CSSM errors mentioned above seem to be unrelated after all.

Thanks Quinn! The Random Unification - https://github.com/apple/swift-evolution/blob/master/proposals/0202-random-unification.md Swift evolution proposal makes the same assumption. Without a definitive source one could also assume that arc4random always utilizes RC4 and conclude that it (and thus the Swift SystemRandomNumberGenerator - https://developer.apple.com/documentation/swift/systemrandomnumbergenerator) is to be avoided, though.

Why do you need this in nscurl specifically? Mostly just to understand how specific status codes are handled on iOS. To elaborate: I have been hitting the same issue described here and here - the URL Loading System raises an error if it receives a response with the status code 403 and a client certificate was involved in the handshake (regardless of whether the certificate was accepted or not). I (re-)raised this as FB10026351. In my case all requests to the server require client authentication and the server may return 403 for unrelated reasons (e.g. for domain errors). The server team agreed to use a different status code for those cases but wanted me to make sure they don't pick one where a similar situation could arise. In my lab appointment the network engineer pointed out that there are in fact status codes other than 403 that receive special treatment and suggested using nscurl to quickly check how specific status codes are handled, but apparently the behaviour changes if a client certificate is involved. Here is what I found: Without client authentication: If no client certificate is involved and the server responds with 401 the client gets an error (NSURLErrorCannotConnectToHost) If no client certificate is involved and the server responds with 403 the client gets the response With client authentication: If a (valid) client certificate is involved and the server responds with 401 the client gets the response If a (valid) client certificate is involved and the server responds with 403 the client gets an error (NSURLErrorClientCertificateRequired) However, the scenarios involving a client certificate cannot be tested with nscurl, hence my question.

Thanks Quinn! You know, there are days where I feel I would not get anything done without you helping me out... Does that mean the dataRepresentation of a SecureEnclave.P256.Signing.PrivateKey is already stored in the keychain by the system, but is inaccessible to client code so the only way for it to get a reference to such a key is to store the dataRepresentation itself and recreate the key from it? And if the key had instead been created by not using CryptoKit, but the Security framework (passing .privateKeyUsage in the access control list) it could later be retrieved by SecItemCopyMatching, correct?

Ok, I think I am getting close. So while SE keys are not actually stored inside the Secure Enclave keys generated by the Security framework are (or can be, depending on whether kSecAttrIsPermanentis set or not) stored in the keychain. Keys generated by Apple CryptoKit are not stored at all and there is no way to convert between the two kinds of keys. Correct?

Thanks again. Do you deem it worthwile to file an enhancement request asking for API parity in this regard (i.e. by providing an initializer on SecureEnclave.P256.Signing.PrivateKeythat takes a parameter akin to kSecAttrIsPermanent)?

Hi Quinn, did anything ever come out of this?

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?

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

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?

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.

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

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?