3 files changed, 76 insertions, 2 deletions
diff --git a/src/cryptography/hazmat/backends/openssl/backend.py b/src/cryptography/hazmat/backends/openssl/backend.py
index 0038ddb0..2752d98d 100644
--- a/src/cryptography/hazmat/backends/openssl/backend.py
+++ b/src/cryptography/hazmat/backends/openssl/backend.py
@@ -38,7 +38,8 @@ from cryptography.hazmat.backends.openssl.rsa import (
     _RSAPrivateKey, _RSAPublicKey
 )
 from cryptography.hazmat.backends.openssl.x509 import (
-    _Certificate, _CertificateSigningRequest
+    _Certificate, _CertificateSigningRequest, _DISTPOINT_TYPE_FULLNAME,
+    _DISTPOINT_TYPE_RELATIVENAME
 )
 from cryptography.hazmat.bindings.openssl.binding import Binding
 from cryptography.hazmat.primitives import hashes, serialization
@@ -359,6 +360,67 @@ def _encode_extended_key_usage(backend, extended_key_usage):
     return pp, r
 
 
+_CRLREASONFLAGS = {
+    x509.ReasonFlags.key_compromise: 1,
+    x509.ReasonFlags.ca_compromise: 2,
+    x509.ReasonFlags.affiliation_changed: 3,
+    x509.ReasonFlags.superseded: 4,
+    x509.ReasonFlags.cessation_of_operation: 5,
+    x509.ReasonFlags.certificate_hold: 6,
+    x509.ReasonFlags.privilege_withdrawn: 7,
+    x509.ReasonFlags.aa_compromise: 8,
+}
+
+
+def _encode_crl_distribution_points(backend, crl_distribution_points):
+    cdp = backend._lib.sk_DIST_POINT_new_null()
+    cdp = backend._ffi.gc(cdp, backend._lib.sk_DIST_POINT_free)
+    for point in crl_distribution_points:
+        dp = backend._lib.DIST_POINT_new()
+        assert dp != backend._ffi.NULL
+
+        if point.reasons:
+            bitmask = backend._lib.ASN1_BIT_STRING_new()
+            assert bitmask != backend._ffi.NULL
+            dp.reasons = bitmask
+            for reason in point.reasons:
+                res = backend._lib.ASN1_BIT_STRING_set_bit(
+                    bitmask, _CRLREASONFLAGS[reason], 1
+                )
+                assert res == 1
+
+        if point.full_name:
+            dpn = backend._lib.DIST_POINT_NAME_new()
+            assert dpn != backend._ffi.NULL
+            dpn.type = _DISTPOINT_TYPE_FULLNAME
+            dpn.name.fullname = _encode_general_names(backend, point.full_name)
+            dp.distpoint = dpn
+
+        if point.relative_name:
+            dpn = backend._lib.DIST_POINT_NAME_new()
+            assert dpn != backend._ffi.NULL
+            dpn.type = _DISTPOINT_TYPE_RELATIVENAME
+            name = _encode_name_gc(backend, point.relative_name)
+            relativename = backend._lib.sk_X509_NAME_ENTRY_dup(name.entries)
+            assert relativename != backend._ffi.NULL
+            dpn.name.relativename = relativename
+            dp.distpoint = dpn
+
+        if point.crl_issuer:
+            dp.CRLissuer = _encode_general_names(backend, point.crl_issuer)
+
+        res = backend._lib.sk_DIST_POINT_push(cdp, dp)
+        assert res >= 1
+
+    pp = backend._ffi.new('unsigned char **')
+    r = backend._lib.i2d_CRL_DIST_POINTS(cdp, pp)
+    assert r > 0
+    pp = backend._ffi.gc(
+        pp, lambda pointer: backend._lib.OPENSSL_free(pointer[0])
+    )
+    return pp, r
+
+
 @utils.register_interface(CipherBackend)
 @utils.register_interface(CMACBackend)
 @utils.register_interface(DERSerializationBackend)
@@ -1177,6 +1239,10 @@ class Backend(object):
                 pp, r = _encode_authority_information_access(
                     self, extension.value
                 )
+            elif isinstance(extension.value, x509.CRLDistributionPoints):
+                pp, r = _encode_crl_distribution_points(
+                    self, extension.value
+                )
             else:
                 raise NotImplementedError('Extension not yet supported.')
 
diff --git a/src/cryptography/hazmat/backends/openssl/x509.py b/src/cryptography/hazmat/backends/openssl/x509.py
index ee9a3bbf..564b2680 100644
--- a/src/cryptography/hazmat/backends/openssl/x509.py
+++ b/src/cryptography/hazmat/backends/openssl/x509.py
@@ -592,6 +592,10 @@ def _decode_extended_key_usage(backend, sk):
     return x509.ExtendedKeyUsage(ekus)
 
 
+_DISTPOINT_TYPE_FULLNAME = 0
+_DISTPOINT_TYPE_RELATIVENAME = 1
+
+
 def _decode_crl_distribution_points(backend, cdps):
     cdps = backend._ffi.cast("Cryptography_STACK_OF_DIST_POINT *", cdps)
     cdps = backend._ffi.gc(cdps, backend._lib.sk_DIST_POINT_free)
@@ -651,7 +655,7 @@ def _decode_crl_distribution_points(backend, cdps):
         # point so make sure it's not null.
         if cdp.distpoint != backend._ffi.NULL:
             # Type 0 is fullName, there is no #define for it in the code.
-            if cdp.distpoint.type == 0:
+            if cdp.distpoint.type == _DISTPOINT_TYPE_FULLNAME:
                 full_name = _decode_general_names(
                     backend, cdp.distpoint.name.fullname
                 )
diff --git a/src/cryptography/x509.py b/src/cryptography/x509.py
index ddb50608..45a302ba 100644
--- a/src/cryptography/x509.py
+++ b/src/cryptography/x509.py
@@ -1781,6 +1781,10 @@ class CertificateBuilder(object):
             )
         elif isinstance(extension, InhibitAnyPolicy):
             extension = Extension(OID_INHIBIT_ANY_POLICY, critical, extension)
+        elif isinstance(extension, CRLDistributionPoints):
+            extension = Extension(
+                OID_CRL_DISTRIBUTION_POINTS, critical, extension
+            )
         else:
             raise NotImplementedError('Unsupported X.509 extension.')