Implement partial support for GSSAPI extension GGF

GGF provides extended credential and security context inquiry that allows
application to retrieve more information about the client's credentials and
security context. One common use case is to use gss_inquire_sec_context_by_oid
to retrieve the "session" key that is required by the SMB protocol for signing
and encrypting a message. These calls are provided as a part of the raw
interface and are not exposed in the high-level interface.

Thanks to @vm86 for his work on the gss_inquire_sec_context_by_oid.

Draft IETF document for these extensions can be found at
https://tools.ietf.org/html/draft-engert-ggf-gss-extensions-00

gssapi/raw/__init__.py

@@ -119,3 +119,9 @@
     from gssapi.raw.ext_rfc6680_comp_oid import *  # noqa
 except ImportError:
     pass
+
+# optional Global Grid Forum support
+try:
+    from gssapi.raw.ext_ggf import *  # noqa
+except ImportError:
+    pass

gssapi/raw/ext_ggf.pyx

@@ -0,0 +1,114 @@
+GSSAPI="BASE"  # This ensures that a full module is generated by Cython
+
+from gssapi.raw.cython_types cimport *
+from gssapi.raw.ext_buffer_sets cimport *
+from gssapi.raw.cython_converters cimport c_get_mech_oid_set
+from gssapi.raw.misc import GSSError
+from gssapi.raw.oids cimport OID
+from gssapi.raw.creds cimport Creds
+from gssapi.raw.sec_contexts cimport SecurityContext
+
+cdef extern from "python_gssapi_ext.h":
+
+    OM_uint32 gss_inquire_cred_by_oid(OM_uint32 *minor_status,
+                                      const gss_cred_id_t cred_handle,
+                                      const gss_OID desired_object,
+                                      gss_buffer_set_t *data_set) nogil
+
+    OM_uint32 gss_inquire_sec_context_by_oid(OM_uint32 *minor_status,
+                                             const gss_ctx_id_t context_handle,
+                                             const gss_OID desired_object,
+                                             gss_buffer_set_t *data_set) nogil
+
+
+def inquire_cred_by_oid(Creds cred_handle not None, OID mech not None):
+    """
+    inquire_cred_by_oid(cred_handle, mech)
+
+    This method inspects a :class:`Creds` object for information
+    specific to a particular mechanism.
+
+    Args:
+        cred_handle (Creds): the security context to query
+        mech (OID): the desired mechanism
+
+    Returns:
+        list: A list of zero or more pieces of data corresponding to the
+            OID set
+
+    Raises:
+        GSS_ERROR
+    """
+
+    cdef gss_buffer_set_t *data_set_ptr = NULL
+    cdef gss_buffer_set_t data_set = GSS_C_NO_BUFFER_SET
+    cdef OM_uint32 maj_stat, min_stat
+
+    data_set_ptr = &data_set
+
+    with nogil:
+        maj_stat = gss_inquire_cred_by_oid(&min_stat, cred_handle.raw_creds,
+                                           &mech.raw_oid, data_set_ptr)
+
+    if maj_stat == GSS_S_COMPLETE:
+        py_tokens = []
+
+        if data_set != GSS_C_NO_BUFFER_SET:
+            for i in range(data_set.count):
+                token = data_set.elements[i]
+                py_tokens.append(token.value[:token.length])
+
+            gss_release_buffer_set(&min_stat, &data_set)
+
+        return py_tokens
+    else:
+        raise GSSError(maj_stat, min_stat)
+
+
+def inquire_sec_context_by_oid(SecurityContext context not None,
+                               OID mech not None):
+    """
+    inquire_sec_context_by_oid(context, mech)
+
+    This method inspects a :class:`SecurityContext` object for information
+    specific to a particular mechanism.
+
+    This method can be used with the GSS_KRB5_INQ_SSPI_SESSION_KEY_OID OID to
+    retrieve the required key that is used to derive the SMB/SAMBA signing and
+    encryption keys.
+
+    Args:
+        context (SecurityContext): the security context to query
+        mech (OID): the desired mechanism
+
+    Returns:
+        list: A list of zero or more pieces of data corresponding to the
+            OID set
+
+    Raises:
+        GSS_ERROR
+    """
+
+    cdef gss_buffer_set_t *data_set_ptr = NULL
+    cdef gss_buffer_set_t data_set = GSS_C_NO_BUFFER_SET
+    cdef OM_uint32 maj_stat, min_stat
+
+    data_set_ptr = &data_set
+
+    with nogil:
+        maj_stat = gss_inquire_sec_context_by_oid(&min_stat, context.raw_ctx,
+                                                  &mech.raw_oid, data_set_ptr)
+
+    if maj_stat == GSS_S_COMPLETE:
+        py_tokens = []
+
+        if data_set != GSS_C_NO_BUFFER_SET:
+            for i in range(data_set.count):
+                token = data_set.elements[i]
+                py_tokens.append(token.value[:token.length])
+
+            gss_release_buffer_set(&min_stat, &data_set)
+
+        return py_tokens
+    else:
+        raise GSSError(maj_stat, min_stat)

gssapi/tests/test_raw.py

@@ -760,6 +760,93 @@ def test_sasl_names(self):
             cmp_mech.shouldnt_be_none()
             cmp_mech.should_be(mech)
 
+    @ktu.gssapi_extension_test('ggf', 'Global Grid Forum')
+    @ktu.gssapi_extension_test('s4u', 'S4U')
+    @ktu.krb_minversion_test('1.16',
+                             'querying impersonator name of krb5 GSS '
+                             'Credential using the '
+                             'GSS_KRB5_GET_CRED_IMPERSONATOR OID')
+    def test_inquire_cred_by_oid_impersonator(self):
+        svc_princ = SERVICE_PRINCIPAL.decode("UTF-8")
+        self.realm.kinit(svc_princ, flags=['-k', '-f'])
+
+        target_name = gb.import_name(TARGET_SERVICE_NAME,
+                                     gb.NameType.hostbased_service)
+
+        client_token = gb.init_sec_context(target_name).token
+
+        # if our acceptor creds have a usage of both, we get
+        # s4u2proxy delegated credentials
+        server_creds = gb.acquire_cred(None, usage='both').creds
+        server_ctx_resp = gb.accept_sec_context(client_token,
+                                                acceptor_creds=server_creds)
+
+        server_ctx_resp.shouldnt_be_none()
+        server_ctx_resp.delegated_creds.shouldnt_be_none()
+        server_ctx_resp.delegated_creds.should_be_a(gb.Creds)
+
+        # GSS_KRB5_GET_CRED_IMPERSONATOR
+        oid = gb.OID.from_int_seq("1.2.840.113554.1.2.2.5.14")
+        info = gb.inquire_cred_by_oid(server_ctx_resp.delegated_creds, oid)
+
+        info.should_be_a(list)
+        info.shouldnt_be_empty()
+        info[0].should_be_a(bytes)
+        info[0].should_be(b"%s@%s" % (SERVICE_PRINCIPAL,
+                                      self.realm.realm.encode('utf-8')))
+
+    @ktu.gssapi_extension_test('ggf', 'Global Grid Forum')
+    def test_inquire_sec_context_by_oid(self):
+        target_name = gb.import_name(TARGET_SERVICE_NAME,
+                                     gb.NameType.hostbased_service)
+        ctx_resp1 = gb.init_sec_context(target_name)
+
+        server_name = gb.import_name(SERVICE_PRINCIPAL,
+                                     gb.NameType.kerberos_principal)
+        server_creds = gb.acquire_cred(server_name)[0]
+        server_resp = gb.accept_sec_context(ctx_resp1[3],
+                                            acceptor_creds=server_creds)
+        server_ctx = server_resp[0]
+        server_tok = server_resp[3]
+
+        client_resp2 = gb.init_sec_context(target_name,
+                                           context=ctx_resp1[0],
+                                           input_token=server_tok)
+        client_ctx = client_resp2[0]
+
+        # GSS_C_INQ_SSPI_SESSION_KEY
+        session_key_oid = gb.OID.from_int_seq("1.2.840.113554.1.2.2.5.5")
+
+        client_key = gb.inquire_sec_context_by_oid(client_ctx, session_key_oid)
+        server_key = gb.inquire_sec_context_by_oid(server_ctx, session_key_oid)
+
+        client_key.should_be_a(list)
+        client_key.shouldnt_be_empty()
+        server_key.should_be_a(list)
+        server_key.shouldnt_be_empty()
+        client_key.should_have_same_items_as(server_key)
+
+    @ktu.gssapi_extension_test('ggf', 'Global Grid Forum')
+    def test_inquire_sec_context_by_oid_should_raise_error(self):
+        target_name = gb.import_name(TARGET_SERVICE_NAME,
+                                     gb.NameType.hostbased_service)
+        ctx_resp1 = gb.init_sec_context(target_name)
+
+        server_name = gb.import_name(SERVICE_PRINCIPAL,
+                                     gb.NameType.kerberos_principal)
+        server_creds = gb.acquire_cred(server_name)[0]
+        server_resp = gb.accept_sec_context(ctx_resp1[3],
+                                            acceptor_creds=server_creds)
+
+        client_resp2 = gb.init_sec_context(target_name,
+                                           context=ctx_resp1[0],
+                                           input_token=server_resp[3])
+        client_ctx = client_resp2[0]
+
+        invalid_oid = gb.OID.from_int_seq("1.2.3.4.5.6.7.8.9")
+        gb.inquire_sec_context_by_oid.should_raise(gb.GSSError, client_ctx,
+                                                   invalid_oid)
+
 
 class TestIntEnumFlagSet(unittest.TestCase):
     def test_create_from_int(self):

setup.py

@@ -264,6 +264,7 @@ def gssapi_modules(lst):
         extension_file('cred_imp_exp', 'gss_import_cred'),
         extension_file('dce', 'gss_wrap_iov'),
         extension_file('iov_mic', 'gss_get_mic_iov'),
+        extension_file('ggf', 'gss_inquire_sec_context_by_oid'),
 
         # see ext_rfc6680_comp_oid for more information on this split
         extension_file('rfc6680', 'gss_display_name_ext'),