3 files changed, 8 insertions, 30 deletions
diff --git a/cryptography/hazmat/backends/__init__.py b/cryptography/hazmat/backends/__init__.py
index ae78822c..b0f663fe 100644
--- a/cryptography/hazmat/backends/__init__.py
+++ b/cryptography/hazmat/backends/__init__.py
@@ -13,13 +13,9 @@
 
 from __future__ import absolute_import, division, print_function
 
+import pkg_resources
+
 from cryptography.hazmat.backends.multibackend import MultiBackend
-from cryptography.hazmat.bindings.commoncrypto.binding import (
-    Binding as CommonCryptoBinding
-)
-from cryptography.hazmat.bindings.openssl.binding import (
-    Binding as OpenSSLBinding
-)
 
 
 _available_backends_list = None
@@ -29,19 +25,15 @@ def _available_backends():
     global _available_backends_list
 
     if _available_backends_list is None:
-        _available_backends_list = []
-
-        if CommonCryptoBinding.is_available():
-            from cryptography.hazmat.backends import commoncrypto
-            _available_backends_list.append(commoncrypto.backend)
-
-        if OpenSSLBinding.is_available():
-            from cryptography.hazmat.backends import openssl
-            _available_backends_list.append(openssl.backend)
+        _available_backends_list = [
+            backend.load(require=False)
+            for backend in pkg_resources.iter_entry_points(
+                "cryptography.backends"
+            )
+        ]
 
     return _available_backends_list
 
-
 _default_backend = None
 
 
diff --git a/cryptography/hazmat/bindings/commoncrypto/binding.py b/cryptography/hazmat/bindings/commoncrypto/binding.py
index ee7378ad..ee09bebd 100644
--- a/cryptography/hazmat/bindings/commoncrypto/binding.py
+++ b/cryptography/hazmat/bindings/commoncrypto/binding.py
@@ -13,9 +13,6 @@
 
 from __future__ import absolute_import, division, print_function
 
-import platform
-import sys
-
 from cryptography.hazmat.bindings.utils import build_ffi
 
 
@@ -53,8 +50,3 @@ class Binding(object):
             modules=cls._modules,
             extra_link_args=["-framework", "Security"]
         )
-
-    @classmethod
-    def is_available(cls):
-        return sys.platform == "darwin" and list(map(
-            int, platform.mac_ver()[0].split("."))) >= [10, 8, 0]
diff --git a/cryptography/hazmat/bindings/openssl/binding.py b/cryptography/hazmat/bindings/openssl/binding.py
index 4cbe3c5b..37891f6b 100644
--- a/cryptography/hazmat/bindings/openssl/binding.py
+++ b/cryptography/hazmat/bindings/openssl/binding.py
@@ -116,12 +116,6 @@ class Binding(object):
         assert res != 0
 
     @classmethod
-    def is_available(cls):
-        # For now, OpenSSL is considered our "default" binding, so we treat it
-        # as always available.
-        return True
-
-    @classmethod
     def init_static_locks(cls):
         with cls._lock_init_lock:
             cls._ensure_ffi_initialized()