Add boilerplate for OpenVPNPrivateKey implementation

OpenVPN Adapter/OpenVPNPrivateKey.h

@@ -0,0 +1,26 @@
+//
+//  OpenVPNPrivateKey.h
+//  OpenVPN Adapter
+//
+//  Created by Sergey Abramchuk on 07.09.17.
+//
+//
+
+#import <Foundation/Foundation.h>
+
+@interface OpenVPNPrivateKey : NSObject
+
++ (nullable OpenVPNPrivateKey *)keyWithPEM:(nonnull NSData *)pemData
+                                  password:(nullable NSString *)password
+                                     error:(out NSError * __nullable * __nullable)error;
+
++ (nullable OpenVPNPrivateKey *)keyWithDER:(nonnull NSData *)derData
+                                  password:(nullable NSString *)password
+                                     error:(out NSError * __nullable * __nullable)error;
+
+- (nonnull instancetype) __unavailable init;
+
+- (nullable NSData *)pemData:(out NSError * __nullable * __nullable)error;
+- (nullable NSData *)derData:(out NSError * __nullable * __nullable)error;
+
+@end

OpenVPN Adapter/OpenVPNPrivateKey.m

@@ -0,0 +1,49 @@
+//
+//  OpenVPNPrivateKey.m
+//  OpenVPN Adapter
+//
+//  Created by Sergey Abramchuk on 07.09.17.
+//
+//
+
+#import <mbedtls/pk.h>
+
+#import "NSError+Message.h"
+#import "OpenVPNError.h"
+#import "OpenVPNPrivateKey.h"
+
+@interface OpenVPNPrivateKey ()
+
+@property (nonatomic, assign) mbedtls_pk_context *key;
+
+@end
+
+@implementation OpenVPNPrivateKey
+
+- (instancetype)init {
+    self = [super init];
+    if (self) {
+        self.key = malloc(sizeof(mbedtls_pk_context));
+        mbedtls_pk_init(self.key);
+    }
+    return self;
+}
+
++ (nullable OpenVPNPrivateKey *)keyWithPEM:(NSData *)pemData password:(NSString *)password error:(out NSError **)error {
+    OpenVPNPrivateKey *key = [OpenVPNPrivateKey new];
+    
+    return key;
+}
+
++ (nullable OpenVPNPrivateKey *)keyWithDER:(NSData *)derData password:(NSString *)password error:(out NSError **)error {
+    OpenVPNPrivateKey *key = [OpenVPNPrivateKey new];
+    
+    return key;
+}
+
+- (void)dealloc {
+    mbedtls_pk_free(self.key);
+    free(self.key);
+}
+
+@end