support delta crl indicator extension (#3936)

This is an extension for CRLs

3 files changed, 33 insertions, 2 deletions

diff --git a/src/cryptography/x509/__init__.py b/src/cryptography/x509/__init__.py
index 176ed8ca..e168adb7 100644
--- a/src/cryptography/x509/__init__.py
+++ b/src/cryptography/x509/__init__.py
@@ -18,8 +18,8 @@ from cryptography.x509.extensions import (
     AccessDescription, AuthorityInformationAccess,
     AuthorityKeyIdentifier, BasicConstraints, CRLDistributionPoints,
     CRLNumber, CRLReason, CertificateIssuer, CertificatePolicies,
-    DistributionPoint, DuplicateExtension, ExtendedKeyUsage, Extension,
-    ExtensionNotFound, ExtensionType, Extensions, GeneralNames,
+    DeltaCRLIndicator, DistributionPoint, DuplicateExtension, ExtendedKeyUsage,
+    Extension, ExtensionNotFound, ExtensionType, Extensions, GeneralNames,
     InhibitAnyPolicy, InvalidityDate, IssuerAlternativeName, KeyUsage,
     NameConstraints, NoticeReference, OCSPNoCheck, PolicyConstraints,
     PolicyInformation, PrecertificateSignedCertificateTimestamps, ReasonFlags,
@@ -119,6 +119,7 @@ __all__ = [
     "load_der_x509_crl",
     "random_serial_number",
     "InvalidVersion",
+    "DeltaCRLIndicator",
     "DuplicateExtension",
     "ExtensionNotFound",
     "UnsupportedGeneralNameType",
diff --git a/src/cryptography/x509/extensions.py b/src/cryptography/x509/extensions.py
index 442000e3..beb20bad 100644
--- a/src/cryptography/x509/extensions.py
+++ b/src/cryptography/x509/extensions.py
@@ -376,6 +376,34 @@ class BasicConstraints(object):
 
 
 @utils.register_interface(ExtensionType)
+class DeltaCRLIndicator(object):
+    oid = ExtensionOID.DELTA_CRL_INDICATOR
+
+    def __init__(self, crl_number):
+        if not isinstance(crl_number, six.integer_types):
+            raise TypeError("crl_number must be an integer")
+
+        self._crl_number = crl_number
+
+    crl_number = utils.read_only_property("_crl_number")
+
+    def __eq__(self, other):
+        if not isinstance(other, DeltaCRLIndicator):
+            return NotImplemented
+
+        return self.crl_number == other.crl_number
+
+    def __ne__(self, other):
+        return not self == other
+
+    def __hash__(self):
+        return hash(self.crl_number)
+
+    def __repr__(self):
+        return "<DeltaCRLIndicator(crl_number={0.crl_number})>".format(self)
+
+
+@utils.register_interface(ExtensionType)
 class CRLDistributionPoints(object):
     oid = ExtensionOID.CRL_DISTRIBUTION_POINTS
 
diff --git a/src/cryptography/x509/oid.py b/src/cryptography/x509/oid.py
index 7f8c9031..fedea310 100644
--- a/src/cryptography/x509/oid.py
+++ b/src/cryptography/x509/oid.py
@@ -87,6 +87,7 @@ class ExtensionOID(object):
     OCSP_NO_CHECK = ObjectIdentifier("1.3.6.1.5.5.7.48.1.5")
     TLS_FEATURE = ObjectIdentifier("1.3.6.1.5.5.7.1.24")
     CRL_NUMBER = ObjectIdentifier("2.5.29.20")
+    DELTA_CRL_INDICATOR = ObjectIdentifier("2.5.29.27")
     PRECERT_SIGNED_CERTIFICATE_TIMESTAMPS = (
         ObjectIdentifier("1.3.6.1.4.1.11129.2.4.2")
     )
@@ -256,6 +257,7 @@ _OID_NAMES = {
     ExtensionOID.SUBJECT_INFORMATION_ACCESS: "subjectInfoAccess",
     ExtensionOID.OCSP_NO_CHECK: "OCSPNoCheck",
     ExtensionOID.CRL_NUMBER: "cRLNumber",
+    ExtensionOID.DELTA_CRL_INDICATOR: "deltaCRLIndicator",
     ExtensionOID.TLS_FEATURE: "TLSFeature",
     AuthorityInformationAccessOID.OCSP: "OCSP",
     AuthorityInformationAccessOID.CA_ISSUERS: "caIssuers",