Added the ability to specify/change the default cipher suite used by OpenSSL.

Author: Bill Abt

README.md

@@ -85,9 +85,11 @@ Both clients and server require at a minimum the following configuration items:
 
 *Note 3:* For the first two versions of the API, if your `Private key` is included in your certificate file, you can omit this parameter and the API will use the same file name as specified for the certificate file.
 
+*Note 4:* If you desire to customize the cipher suite used, you can do so by setting the `cipherSuite` member after creating the configuration.  The default value if not changed is set to `ALL:!ADH:!EXPORT56:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP:+eNULL`. See the example below.
+
 #### Example
 
-The following illustrates creating a configuration using the second form of the API above using a self-signed certificate file as the key file and not supplying a certificate chain file:
+The following illustrates creating a configuration using the second form of the API above using a self-signed certificate file as the key file and not supplying a certificate chain file.  It also illustrates setting the cipher suite to `ALL` from the default:
 ```swift
 import SSLService
 
@@ -98,6 +100,8 @@ let myKeyPath = "/opt/myApp/config/myKeyFile.pem"
 
 let myConfig = SSLService.Configuration(withCACertificateDirectory: nil, usingCertificateFile: myCertPath, withKeyFile: myKeyFile)
 
+myConfig.cipherSuite = "ALL"
+
 ...
 
 ```

Sources/SSLService.swift

@@ -62,6 +62,9 @@ public class SSLService : SSLServiceDelegate {
 		/// True if using `self-signed` certificates.
 		public private(set) var certsAreSelfSigned = false
 
+		/// Cipher suite to use. Defaults to `ALL:!ADH:!EXPORT56:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP:+eNULL`
+		public var cipherSuite: String = "ALL:!ADH:!EXPORT56:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP:+eNULL"
+		
 		// MARK: Lifecycle
 
 		///
@@ -506,7 +509,7 @@ public class SSLService : SSLServiceDelegate {
 		}
 
 		// Handle the stuff common to both client and server...
-		SSL_CTX_set_cipher_list(context, "ALL")
+		SSL_CTX_set_cipher_list(context, self.configuration.cipherSuite)
 		if self.configuration.certsAreSelfSigned {
 			SSL_CTX_set_verify(context, SSL_VERIFY_NONE, nil)
 		} else {