Implement parsing private key DER and PEM data

OpenVPN Adapter/OpenVPNPrivateKey.m

@@ -14,7 +14,7 @@
 
 @interface OpenVPNPrivateKey ()
 
-@property (nonatomic, assign) mbedtls_pk_context *key;
+@property (nonatomic, assign) mbedtls_pk_context *ctx;
 
 @end
 
@@ -23,8 +23,8 @@
 - (instancetype)init {
     self = [super init];
     if (self) {
-        self.key = malloc(sizeof(mbedtls_pk_context));
+        self.ctx = malloc(sizeof(mbedtls_pk_context));
-        mbedtls_pk_init(self.key);
+        mbedtls_pk_init(self.ctx);
     }
     return self;
 }
@@ -32,18 +32,46 @@
 + (nullable OpenVPNPrivateKey *)keyWithPEM:(NSData *)pemData password:(NSString *)password error:(out NSError **)error {
     OpenVPNPrivateKey *key = [OpenVPNPrivateKey new];
     
+    NSString *pemString = [[NSString alloc] initWithData:pemData encoding:NSUTF8StringEncoding];
+    
+    int result = mbedtls_pk_parse_key(key.ctx, (const unsigned char *)pemString.UTF8String, pemData.length + 1, (const unsigned char *)password.UTF8String, password.length + 1);
+    if (result < 0) {
+        if (error) {
+            NSString *reason = [NSError reasonFromResult:result];
+            *error = [NSError errorWithDomain:OpenVPNIdentityErrorDomain code:result userInfo:@{
+                NSLocalizedDescriptionKey: @"Failed to read PEM data.",
+                NSLocalizedFailureReasonErrorKey: reason
+            }];
+        }
+        
+        return nil;
+    }
+    
     return key;
 }
 
 + (nullable OpenVPNPrivateKey *)keyWithDER:(NSData *)derData password:(NSString *)password error:(out NSError **)error {
     OpenVPNPrivateKey *key = [OpenVPNPrivateKey new];
     
+    int result = mbedtls_pk_parse_key(key.ctx, derData.bytes, derData.length, (const unsigned char *)password.UTF8String, password.length + 1);
+    if (result < 0) {
+        if (error) {
+            NSString *reason = [NSError reasonFromResult:result];
+            *error = [NSError errorWithDomain:OpenVPNIdentityErrorDomain code:result userInfo:@{
+                NSLocalizedDescriptionKey: @"Failed to read DER data.",
+                NSLocalizedFailureReasonErrorKey: reason
+            }];
+        }
+        
+        return nil;
+    }
+    
     return key;
 }
 
 - (void)dealloc {
-    mbedtls_pk_free(self.key);
+    mbedtls_pk_free(self.ctx);
-    free(self.key);
+    free(self.ctx);
 }
 
 @end