multibacken for docs

2 files changed, 30 insertions, 3 deletions

diff --git a/cryptography/hazmat/backends/multibackend.py b/cryptography/hazmat/backends/multibackend.py
index 6893cad6..221f1a1e 100644
--- a/cryptography/hazmat/backends/multibackend.py
+++ b/cryptography/hazmat/backends/multibackend.py
@@ -17,8 +17,9 @@ from cryptography import utils
 from cryptography.exceptions import UnsupportedAlgorithm, _Reasons
 from cryptography.hazmat.backends.interfaces import (
     CMACBackend, CipherBackend, DSABackend, EllipticCurveBackend, HMACBackend,
-    HashBackend, PBKDF2HMACBackend, PKCS8SerializationBackend,
-    RSABackend, TraditionalOpenSSLSerializationBackend
+    HashBackend, PBKDF2HMACBackend, PEMSerializationBackend,
+    PKCS8SerializationBackend, RSABackend,
+    TraditionalOpenSSLSerializationBackend
 )
 
 
@@ -32,6 +33,7 @@ from cryptography.hazmat.backends.interfaces import (
 @utils.register_interface(TraditionalOpenSSLSerializationBackend)
 @utils.register_interface(DSABackend)
 @utils.register_interface(EllipticCurveBackend)
+@utils.register_interface(PEMSerializationBackend)
 class MultiBackend(object):
     name = "multibackend"
 
@@ -318,6 +320,15 @@ class MultiBackend(object):
             _Reasons.UNSUPPORTED_ELLIPTIC_CURVE
         )
 
+    def load_pem_private_key(self, data, password):
+        for b in self._filtered_backends(PEMSerializationBackend):
+            return b.load_pem_private_key(data, password)
+
+        raise UnsupportedAlgorithm(
+            "This backend does not support this key serialization.",
+            _Reasons.UNSUPPORTED_SERIALIZATION
+        )
+
     def load_pkcs8_pem_private_key(self, data, password):
         for b in self._filtered_backends(PKCS8SerializationBackend):
             return b.load_pkcs8_pem_private_key(data, password)
diff --git a/tests/hazmat/backends/test_multibackend.py b/tests/hazmat/backends/test_multibackend.py
index 168ed688..655acc44 100644
--- a/tests/hazmat/backends/test_multibackend.py
+++ b/tests/hazmat/backends/test_multibackend.py
@@ -19,7 +19,8 @@ from cryptography.exceptions import (
 )
 from cryptography.hazmat.backends.interfaces import (
     CMACBackend, CipherBackend, DSABackend, EllipticCurveBackend, HMACBackend,
-    HashBackend, PBKDF2HMACBackend, PKCS8SerializationBackend, RSABackend,
+    HashBackend, PBKDF2HMACBackend, PEMSerializationBackend,
+    PKCS8SerializationBackend, RSABackend,
     TraditionalOpenSSLSerializationBackend
 )
 from cryptography.hazmat.backends.multibackend import MultiBackend
@@ -211,6 +212,12 @@ class DummyTraditionalOpenSSLSerializationBackend(object):
         pass
 
 
+@utils.register_interface(PEMSerializationBackend)
+class DummyPEMSerializationBackend(object):
+    def load_pem_private_key(self, data, password):
+        pass
+
+
 class TestMultiBackend(object):
     def test_ciphers(self):
         backend = MultiBackend([
@@ -520,3 +527,12 @@ class TestMultiBackend(object):
         backend = MultiBackend([])
         with raises_unsupported_algorithm(_Reasons.UNSUPPORTED_SERIALIZATION):
             backend.load_traditional_openssl_pem_private_key(b"keydata", None)
+
+    def test_pem_serialization_backend(self):
+        backend = MultiBackend([DummyPEMSerializationBackend()])
+
+        backend.load_pem_private_key(b"keydata", None)
+
+        backend = MultiBackend([])
+        with raises_unsupported_algorithm(_Reasons.UNSUPPORTED_SERIALIZATION):
+            backend.load_pem_private_key(b"keydata", None)