Re: Why does NSURLSession in iOS9 return -9802?

Thanks a lot. That was it. Doh :/

Here's a sample project that has NSExceptionAllowsInsecureHTTPLoads.

Thanks.  It’s really helpful to have a simple example to play with.  And, after a bit of spelunking, I have a rough idea what’s going on.

Your test app accesses api.braintreegateway.com, so I compared its TLS setup to dhoerl’s S3 example that I’ve been testing:

$ TLSTool s_client -connect api.braintreegateway.com:443
…
* protocol: TLS 1.2
* cipher: ECDHE_RSA_WITH_AES_128_CBC_SHA256
* trust result: unspecified
* certificate info:
*  0 rsaEncryption 2048 sha1-with-rsa-signature 'api.braintreegateway.com'
…
^C
$ TLSTool s_client -connect s3.amazonaws.com:443
…
* protocol: TLS 1.2
* cipher: ECDHE_RSA_WITH_AES_128_CBC_SHA
* trust result: unspecified
* certificate info:
*  0 rsaEncryption 2048 sha1-with-rsa-signature 's3.amazonaws.com'
…
^C

The results are very similar, with two things to note:

• Your site uses ECDHE_RSA_WITH_AES_128_CBC_SHA256, which is ‘better’ than the ECDHE_RSA_WITH_AES_128_CBC_SHA used by S3.  Both are explicitly allowed by ATS.

• Both sites use sha1-with-rsa-signature, which is the ATS roadblock we’re trying to get around.

I then set up a test project with an ATS dictionary like this:

<key>NSAppTransportSecurity</key>
<dict>
    <key>NSExceptionDomains</key>
    <dict>
        <key>s3.amazonaws.com</key>
        <dict>
            <key>NSExceptionAllowsInsecureHTTPLoads</key>
            <true/>
        </dict>
        <key>api.braintreegateway.com</key>
        <dict>
            <key>NSExceptionAllowsInsecureHTTPLoads</key>
            <true/>
        </dict>
    </dict>
</dict>

Weirdly, this works for S3 and not for your domain.  Why?

After some digging I worked this out: the OS thinks that your site requires HTTP Strict Transport Security (HSTS).  Now, I don’t know why the OS thinks that, but the fact that it does overrides the ATS exception in the Info.plist.  In short, HSTS trumps ATS.

Alas, I’ve totally run out of time to investigate this in the context of DevForums.  I’d be happy to look into the HSTS side of things in the context of a DTS tech support incident.

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Quinn "The Eskimo!"
Apple Developer Relations, Developer Technical Support, Core OS/Hardware
let myEmail = "eskimo" + "1" + "@apple.com"

You may want to retest on the public release. I am actually seeing different results between the GM and the final public release which I was not expecting.

The Twitter search api at https://api.twitter.com is similar to the Amazon S3 example above. It uses TLS 1.2 and ECDHE_RSA key exchange which provides forward secrecy but has a weakly signed SHA1 signature (see https://www.ssllabs.com/ssltest/analyze.html?d=api.twitter.com&s=199.59.148.87).

When testing with the GM I was seeing ATS rejections (error code -9802) which was fixed adding the NSThirdPartyExceptionAllowsInsecureHTTPLoads exception. This would seem to be expected if I have understood the ATS policy correctly.

What is odd is that with the public release of iOS 9 the exception is no longer required. The connection succeeds with the default ATS policy. Maybe the requirement for a SHA256 signed signature was relaxed but then at least the ATS Technote should be updated.

I have logged radar 22763438 with CFNetwork debug logs for both cases.