iOS App Fails to Establish Secure Connection (NSURLErrorDomain Code=-1200 SSL Error)

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Hi everyone 👋

I’m running into a persistent SSL issue on iOS where the app fails to establish a secure HTTPS connection to our backend APIs. The same endpoints work fine on Android and web, but on iOS the requests fail with:

Error Domain=NSURLErrorDomain Code=-1200
"An SSL error has occurred and a secure connection to the server cannot be made."
UserInfo={
    NSLocalizedDescription = "An SSL error has occurred and a secure connection to the server cannot be made.";
    _kCFStreamErrorDomainKey = 3;
    _kCFStreamErrorCodeKey = -9802;
}

🔍 What I’ve Checked:

The servers use valid, trusted SSL certificates from a public CA
TLS 1.2 and 1.3 are enabled
The intermediate certificates appear correctly configured (verified using SSL Labs)
The issue happens on our customer's end. (Got it via Sentry)

Note: We recently removed NSAppTransportSecurity(NSAllowsArbitraryLoads) on our app, since all the endpoints use valid HTTPS certificates and standard configurations.

❓ Questions:

Are there additional SSL validation checks performed by iOS when ATS is enabled?
Has anyone seen similar behaviour, where valid certificate chains still trigger SSL errors?

Any insights or debugging suggestions would be greatly appreciated 🙏

Answered by DTS Engineer in 864066022

As Albert suggested, I recommend that you isolate this in a small test project. You can then experiment with adding and removing NSAllowsArbitraryLoads. That’ll tell you whether ATS is a factor or not, and that’s always a good first step in situations like this.

That -9802 error is errSSLFatalAlert. This is a common symptom of ATS problems because ATS simulates the TLS fatal alert on its failure path. However, it’s not a definitive, because TLS fatal alerts can have other origins.

Finally, is your server available on the public Internet. If so, and you post the URL, I’d be happy to take a look.

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

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Answer 1

DTS Engineer OP

Apple

1d

Thank you for sharing the post. The error appears to be related to the domain in my opinion. Have you created a simple application to test different HTTPS domains using your code to determine if you obtain the same results?

If you encounter the same error with different domains, I suggest posting your sample code here to identify the source of the request. If the code functions correctly with other domains, I recommend investigating potential issues with your domain or certificate. A focused sample application targeting your domain may provide insights into the request’s problem and offer guidance on resolving it.

Hope this simple troubleshooting helps narrow it down.

Albert Pascual   Worldwide Developer Relations.

0

Answer 2