3 - Linux key support and associated tests passing OK

[gtaban]

Add functionality for key support for Linux.

Enable the following 14 key-based tests which run OK on Linux:

test_public_initWithData
test_public_initWithCertData
test_public_initWithCertData2
test_public_initWithBase64String
test_public_initWithBase64StringWhichContainsNewLines
test_public_initWithPEMString
test_public_initWithPEMName
test_public_initWithDERName
test_publicKeysFromEmptyPEMFileReturnsEmptyArray
test_public_initWithCertificateName
test_public_initWithCertificateName2
test_private_initWithPEMString
test_private_initWithPEMName
test_private_initWithDERName

Description

Motivation and Context

How Has This Been Tested?

Linux 16.04 OpenSSL 1.0.2g

Checklist:

• I have submitted a CLA form
• If applicable, I have updated the documentation accordingly.
• If applicable, I have added tests to cover my changes.

[billabt]

I made some minor changes to exploit common code and eliminate some redundancy. Also, the XXXX_initWithPEMStringHeaderless tests should be enabled and working on Linux as well. They test the case where a PEM string is passed that's already been stripped. This can happen when the PEM is created on Linux and then used on macOS. The problem is with this piece of code...

	public class func createPublicKey(withPEM pemString: String) throws -> PublicKey {
		
        #if os(Linux)
			
            // OpenSSL takes the full PEM format...
            let keyData = pemString.data(using: String.Encoding.utf8)!

            return try PublicKey(with: keyData)
            
        #else
			
            // Get the Base64 representation of the PEM encoded string after stripping off the PEM markers
            let base64String = try CryptorRSA.base64String(for: pemString)
            
            return try createPublicKey(withBase64: base64String)
			
        #endif
	}

In the statement

let keyData = pemString.data(using: String.Encoding.utf8)!

you are explicitly force unwrapping the object. This is the point where the test is failing on Linux with the following exception:

fatal error: unexpectedly found nil while unwrapping an Optional value

Once you fix that, the headerless tests should work.