Set correct KU and EKU extensions

tests/test_trustme.py

@@ -38,7 +38,27 @@ def assert_is_ca(ca_cert):
     assert ku.value.crl_sign is True
     assert ku.critical is True
 
-    eku = ca_cert.extensions.get_extension_for_class(x509.ExtendedKeyUsage)
+    try:
+        ca_cert.extensions.get_extension_for_class(x509.ExtendedKeyUsage)
+    except x509.ExtensionNotFound:
+        pass
+    else:
+        pytest.fail("ca cert has an EKU")
+
+
+def assert_is_leaf(leaf_cert):
+    bc = leaf_cert.extensions.get_extension_for_class(x509.BasicConstraints)
+    assert bc.value.ca is False
+    assert bc.critical is True
+
+    ku = leaf_cert.extensions.get_extension_for_class(x509.KeyUsage)
+    assert ku.value.digital_signature is True
+    assert ku.value.key_encipherment is True
+    assert ku.value.key_cert_sign is False
+    assert ku.value.crl_sign is False
+    assert ku.critical is True
+
+    eku = leaf_cert.extensions.get_extension_for_class(x509.ExtendedKeyUsage)
     assert eku.value == x509.ExtendedKeyUsage([
         x509.oid.ExtendedKeyUsageOID.CLIENT_AUTH,
         x509.oid.ExtendedKeyUsageOID.SERVER_AUTH,
@@ -88,6 +108,7 @@ def test_basics():
 
     assert server_cert.not_valid_before <= today <= server_cert.not_valid_after
     assert server_cert.issuer == ca_cert.subject
+    assert_is_leaf(server_cert)
 
     san = server_cert.extensions.get_extension_for_class(x509.SubjectAlternativeName)
     hostnames = san.value.get_values_for_type(x509.DNSName)
@@ -177,6 +198,7 @@ def test_intermediate():
     child_server_cert = x509.load_pem_x509_certificate(
         child_server.cert_chain_pems[0].bytes(), default_backend())
     assert child_server_cert.issuer == child_ca_cert.subject
+    assert_is_leaf(child_server_cert)
 
 
 def test_path_length():
@@ -422,6 +444,7 @@ def test_identity_variants():
         san = cert.extensions.get_extension_for_class(
             x509.SubjectAlternativeName
         )
+        assert_is_leaf(cert)
         got = san.value[0]
         assert got == expected
 

trustme/__init__.py

@@ -240,25 +240,17 @@ def __init__(
             )
             .add_extension(
                 x509.KeyUsage(
-                    digital_signature=False,
+                    digital_signature=True,  # OCSP
                     content_commitment=False,
                     key_encipherment=False,
                     data_encipherment=False,
                     key_agreement=False,
-                    key_cert_sign=True,
-                    crl_sign=True,
+                    key_cert_sign=True,  # sign certs
+                    crl_sign=True,  # sign revocation lists
                     encipher_only=False,
                     decipher_only=False),
                 critical=True
             )
-            .add_extension(
-                x509.ExtendedKeyUsage([
-                    ExtendedKeyUsageOID.CLIENT_AUTH,
-                    ExtendedKeyUsageOID.SERVER_AUTH,
-                    ExtendedKeyUsageOID.CODE_SIGNING,
-                ]),
-                critical=True
-            )
             .sign(
                 private_key=sign_key,
                 algorithm=hashes.SHA256(),
@@ -402,6 +394,27 @@ def issue_cert(self, *identities, **kwargs):
                 ),
                 critical=True,
             )
+            .add_extension(
+                x509.KeyUsage(
+                    digital_signature=True,
+                    content_commitment=False,
+                    key_encipherment=True,
+                    data_encipherment=False,
+                    key_agreement=False,
+                    key_cert_sign=False,
+                    crl_sign=False,
+                    encipher_only=False,
+                    decipher_only=False),
+                critical=True
+            )
+            .add_extension(
+                x509.ExtendedKeyUsage([
+                    ExtendedKeyUsageOID.CLIENT_AUTH,
+                    ExtendedKeyUsageOID.SERVER_AUTH,
+                    ExtendedKeyUsageOID.CODE_SIGNING,
+                ]),
+                critical=True
+            )
             .sign(
                 private_key=self._private_key,
                 algorithm=hashes.SHA256(),