App Transport Security Tip

If you're dealing with App Transport Security (ATS), here's one small snippet from the OS X El Capitan Developer Beta 6 Release Notes that you might have missed (I know I did)...

The

nscurl

tool on OS X El Capitan supports diagnosing ATS secure connections. For example,

/usr/bin/nscurl --ats-diagnostics https://www.example.com

will display ATS connection information for

www.example.com

. Run

/usr/bin/nscurl -h

for more information.

The

nscurl

In addition, if you’re trying to work out exactly what TLS parameters your server supports, one good option is to connect to it using TLSTool. For example:

$ TLSTool s_client -connect forums.developer.apple.com:443
*  input stream did open
* output stream did open
* output stream has space
* protocol: TLS 1.2
* cipher: ECDHE_RSA_WITH_AES_256_GCM_SHA384
* trust result: unspecified
* certificate info:
*   0 rsaEncryption 2048 sha256-with-rsa-signature 'forums.developer.apple.com'
*   1 rsaEncryption 2048 sha256-with-rsa-signature 'Symantec Class 3 EV SSL CA - G3'
*   2 rsaEncryption 2048 sha1-with-rsa-signature 'VeriSign Class 3 Public Primary Certification Authority - G5'
^C

As you can see, DevForums meets all the ATS requirements, including:

• a TLS version of 1.2 (line 5)

• a cypher suite of

  ECDHE_RSA_WITH_AES_256_GCM_SHA384

  (line 6)

• a 2048 bit RSA key in its server certificate (line 9)

• that certificate protected by a SHA2-256 signature (line 9)

Some hints and tips for using

TLSTool

• If you’re targeting iOS 9, run

  TLSTool

  on a Mac running OS X 10.11.x on the same network as your iOS device.

• Alternatively, as

  TLSTool

  is sample code, simply integrate its source code into a test function within your iOS app.

• If

  TLSTool

  fails to connect, try running it with the

  -noverify

  option.

• If you want to know what certificates are in play, run

  TLSTool

  with the

  -showcerts

  option.

Share and Enjoy
—
Quinn "The Eskimo!"
Apple Developer Relations, Developer Technical Support, Core OS/Hardware

let myEmail = "eskimo" + "1" + "@apple.com"