crypto: Build a base object for openssl modules (#26945)

More openssl modules are about to be made, each of them rewriting
some pieces of code that can be refactored and used via a common
library.

This commit aims to create this "base" object and the common functions
one might want to reuse in order to avoid duplication.

lib/ansible/module_utils/crypto.py

@@ -23,7 +23,16 @@ except ImportError:
     # user know that OpenSSL couldn't be found.
     pass
 
+import abc
+import errno
 import hashlib
+import os
+
+from ansible.module_utils import six
+
+
+class OpenSSLObjectError(Exception):
+    pass
 
 
 def get_fingerprint(path, passphrase):
@@ -48,3 +57,69 @@ def get_fingerprint(path, passphrase):
         pass
 
     return fingerprint
+
+
+def load_privatekey(path, passphrase=None):
+    """Load the specified OpenSSL private key."""
+
+    try:
+        privatekey_content = open(path, 'rb').read()
+        privatekey = crypto.load_privatekey(crypto.FILETYPE_PEM,
+                                            privatekey_content,
+                                            passphrase)
+        return privatekey
+    except (IOError, OSError) as exc:
+        raise OpenSSLObjectError(exc)
+
+
+def load_certificate(path):
+    """Load the specified certificate."""
+
+    try:
+        cert_content = open(path, 'rb').read()
+        cert = crypto.load_certificate(crypto.FILETYPE_PEM, cert_content)
+        return cert
+    except (IOError, OSError) as exc:
+        raise OpenSSLObjectError(exc)
+
+
+@six.add_metaclass(abc.ABCMeta)
+class OpenSSLObject(object):
+
+    def __init__(self, path, state, force, check_mode):
+        self.path = path
+        self.state = state
+        self.force = force
+        self.name = os.path.basename(path)
+        self.changed = False
+        self.check_mode = check_mode
+
+    @abc.abstractmethod
+    def check(self):
+        """Ensure the resource is in its desired state."""
+
+        pass
+
+    @abc.abstractmethod
+    def dump(self):
+        """Serialize the object into a dictionary."""
+
+        pass
+
+    @abc.abstractmethod
+    def generate(self):
+        """Generate the resource."""
+
+        pass
+
+    def remove(self):
+        """Remove the resource from the filesystem."""
+
+        try:
+            os.remove(self.path)
+            self.changed = True
+        except OSError as exc:
+            if exc.errno != errno.ENOENT:
+                raise OpenSSLObjectError(exc)
+            else:
+                pass