add RSA private key generation restrictions to primitive layer

2 files changed, 25 insertions, 0 deletions

diff --git a/cryptography/hazmat/primitives/asymmetric/rsa.py b/cryptography/hazmat/primitives/asymmetric/rsa.py
index a9f57838..e3ad5f1d 100644
--- a/cryptography/hazmat/primitives/asymmetric/rsa.py
+++ b/cryptography/hazmat/primitives/asymmetric/rsa.py
@@ -187,6 +187,15 @@ class RSAPrivateKey(object):
                 _Reasons.BACKEND_MISSING_INTERFACE
             )
 
+        if public_exponent < 3:
+            raise ValueError("public_exponent must be >= 3.")
+
+        if public_exponent & 1 == 0:
+            raise ValueError("public_exponent must be odd.")
+
+        if key_size < 512:
+            raise ValueError("key_size must be at least 512-bits.")
+
         return backend.generate_rsa_private_key(public_exponent, key_size)
 
     def signer(self, padding, algorithm, backend):
diff --git a/tests/hazmat/backends/test_openssl.py b/tests/hazmat/backends/test_openssl.py
index 0ccf7286..bfcdf14a 100644
--- a/tests/hazmat/backends/test_openssl.py
+++ b/tests/hazmat/backends/test_openssl.py
@@ -277,6 +277,22 @@ class TestOpenSSLRSA(object):
         assert backend.generate_rsa_parameters_supported(3, 1024) is True
         assert backend.generate_rsa_parameters_supported(3, 511) is False
 
+    def test_generate_bad_public_exponent(self):
+        with pytest.raises(ValueError):
+            backend.generate_rsa_private_key(public_exponent=1, key_size=2048)
+
+        with pytest.raises(ValueError):
+            backend.generate_rsa_private_key(public_exponent=4, key_size=2048)
+
+    def test_cant_generate_insecure_tiny_key(self):
+        with pytest.raises(ValueError):
+            backend.generate_rsa_private_key(public_exponent=65537,
+                                             key_size=511)
+
+        with pytest.raises(ValueError):
+            backend.generate_rsa_private_key(public_exponent=65537,
+                                             key_size=256)
+
     @pytest.mark.skipif(
         backend._lib.OPENSSL_VERSION_NUMBER >= 0x1000100f,
         reason="Requires an older OpenSSL. Must be < 1.0.1"