Implement remaining GGF extensions

This commit implements the remaining GGF extensions that provides extended
support for managing security contexts and credentials. This commit adds the
functions gss_set_sec_context_option and gss_set_cred_option. A common use
case for gss_set_sec_context_option is with NTLM to reset the crypto handles
using the GSS_NTLMSSP_RESET_CRYPTO_OID_LENGTH OID.

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

Draft IETF document for the gss_set_cred_option can be found at
https://tools.ietf.org/html/draft-williams-kitten-channel-bound-flag-00

README.txt

@@ -156,6 +156,8 @@ In addition to RFC 2743/2744, Python-GSSAPI also has support for:
 
 * `acquire_cred_with_password` and `add_cred_with_password`
 
+* GGF Extensions
+
 The Team
 ========
 

gssapi/raw/ext_ggf.pyx

@@ -9,6 +9,9 @@ required by the SMB protocol for signing and encrypting a message.
 
 Draft IETF document for these extensions can be found at
 https://tools.ietf.org/html/draft-engert-ggf-gss-extensions-00
+
+Draft IETF document for the gss_set_cred_option can be found at
+https://tools.ietf.org/html/draft-williams-kitten-channel-bound-flag-00
 """
 GSSAPI="BASE"  # This ensures that a full module is generated by Cython
 
@@ -32,6 +35,17 @@ cdef extern from "python_gssapi_ext.h":
                                              const gss_OID desired_object,
                                              gss_buffer_set_t *data_set) nogil
 
+    # not in GGF draft but usually lumped together with the others
+    OM_uint32 gss_set_cred_option(OM_uint32 *minor_status,
+                                  gss_cred_id_t *cred,
+                                  const gss_OID desired_object,
+                                  const gss_buffer_t value) nogil
+
+    OM_uint32 gss_set_sec_context_option(OM_uint32 *minor_status,
+                                         gss_ctx_id_t *context_handle,
+                                         const gss_OID desired_object,
+                                         const gss_buffer_t value) nogil
+
 
 def inquire_cred_by_oid(Creds cred_handle not None,
                         OID desired_aspect not None):
@@ -93,7 +107,7 @@ def inquire_sec_context_by_oid(SecurityContext context not None,
 
     Args:
         context (SecurityContext): the Security Context to query
-        desired_aspect (OID): the desired aspected of the Security Context to
+        desired_aspect (OID): the desired aspect of the Security Context to
             inquire about.
 
     Returns:
@@ -127,3 +141,113 @@ def inquire_sec_context_by_oid(SecurityContext context not None,
         return py_tokens
     else:
         raise GSSError(maj_stat, min_stat)
+
+
+def set_cred_option(OID desired_aspect not None, Creds creds=None, value=None):
+    """
+    set_cred_option(desired_aspect, creds=None, value=None)
+
+    This method is used to set options of a :class:`Creds` object based on
+    an OID key. The options that can be set depends on the mech the credentials
+    were created with.
+
+    An example of how this can be used would be to set the
+    GSS_KRB5_CRED_NO_CI_FLAGS_X on a Kerberos credential. The OID string for
+    this flag is '1.2.752.43.13.29' and it requires no value to be set. This
+    must be set before the SecurityContext was initialised with the
+    credentials.
+
+    Args:
+        desired_aspect (OID): the desired aspect of the Credential to set.
+        cred_handle (Creds): the Credentials to set, or None to create a new
+            credential.
+        value (bytes): the value to set on the desired aspect of the Credential
+            or None to send GSS_C_EMPTY_BUFFER.
+
+    Returns:
+        Creds: The output credential.
+
+    Raises:
+        GSS_ERROR
+    """
+
+    cdef gss_buffer_desc value_buffer
+    if value is not None:
+        value_buffer = gss_buffer_desc(len(value), value)
+    else:
+        # GSS_C_EMPTY_BUFFER
+        value_buffer = gss_buffer_desc(0, NULL)
+
+    cdef Creds output_creds = creds
+    if output_creds is None:
+        output_creds = Creds()
+
+
+    cdef OM_uint32 maj_stat, min_stat
+
+    with nogil:
+        maj_stat = gss_set_cred_option(&min_stat,
+                                       &output_creds.raw_creds,
+                                       &desired_aspect.raw_oid,
+                                       &value_buffer)
+
+    if maj_stat == GSS_S_COMPLETE:
+        return output_creds
+    else:
+        raise GSSError(maj_stat, min_stat)
+
+
+def set_sec_context_option(OID desired_aspect not None,
+                           SecurityContext context=None,
+                           value=None):
+    """
+    set_sec_context_option(desired_aspect, context=None, value=None)
+
+    This method is used to set a value for a specific OID of a
+    :class:`SecurityContext` object. The OID and value to pass in depends on
+    the mech the SecurityContext backs.
+
+    An example of how this can be used would be to reset the NTLM crypto engine
+    used in gss-ntlmssp. The OID that controls this value is
+    '1.3.6.1.4.1.7165.655.1.3' and it takes it a byte value that represents
+    an int32 where 1 reset's the verifier handle and any other int resets the
+    sender handle.
+
+    Args:
+        desired_aspect (OID): the desired aspect of the Security Context to set
+            the value for.
+        context (SecurityContext): the Security Context to set, or None to
+            create a new context.
+        value (bytes): the value to set on the desired aspect of the Security
+            Context or None to send GSS_C_EMPTY_BUFFER.
+
+    Returns:
+        SecurityContext: The output security context.
+
+    Raises:
+        GSS_ERROR
+    """
+
+    cdef gss_buffer_desc value_buffer
+    if value is not None:
+        value_buffer = gss_buffer_desc(len(value), value)
+    else:
+        # GSS_C_EMPTY_BUFFER
+        value_buffer = gss_buffer_desc(0, NULL)
+
+    cdef SecurityContext output_context = context
+    if output_context is None:
+        output_context = SecurityContext()
+
+    cdef OM_uint32 maj_stat, min_stat
+
+    with nogil:
+        maj_stat = gss_set_sec_context_option(&min_stat,
+                                              &output_context.raw_ctx,
+                                              &desired_aspect.raw_oid,
+                                              &value_buffer)
+
+    if maj_stat == GSS_S_COMPLETE:
+        return output_context
+    else:
+        raise GSSError(maj_stat, min_stat)

gssapi/tests/test_raw.py

@@ -847,6 +847,67 @@ def test_inquire_sec_context_by_oid_should_raise_error(self):
         gb.inquire_sec_context_by_oid.should_raise(gb.GSSError, client_ctx,
                                                    invalid_oid)
 
+    @ktu.gssapi_extension_test('ggf', 'Global Grid Forum')
+    @ktu.krb_minversion_test('1.14',
+                             'GSS_KRB5_CRED_NO_CI_FLAGS_X was added in MIT '
+                             'krb5 1.14')
+    def test_set_cred_option(self):
+        name = gb.import_name(SERVICE_PRINCIPAL,
+                              gb.NameType.kerberos_principal)
+        # GSS_KRB5_CRED_NO_CI_FLAGS_X
+        no_ci_flags_x = gb.OID.from_int_seq("1.2.752.43.13.29")
+        orig_cred = gb.acquire_cred(name).creds
+
+        # nothing much we can test here apart from it doesn't fail and the
+        # id of the return cred is the same as the input one
+        output_cred = gb.set_cred_option(no_ci_flags_x, creds=orig_cred)
+        id(orig_cred).should_be(id(output_cred))
+
+    @ktu.gssapi_extension_test('ggf', 'Global Grid Forum')
+    def test_set_cred_option_should_raise_error(self):
+        name = gb.import_name(SERVICE_PRINCIPAL,
+                              gb.NameType.kerberos_principal)
+        orig_cred = gb.acquire_cred(name).creds
+
+        # this is a fake OID and shouldn't work at all
+        invalid_oid = gb.OID.from_int_seq("1.2.3.4.5.6.7.8.9")
+        gb.set_cred_option.should_raise(gb.GSSError, invalid_oid, orig_cred,
+                                        b"\x00")
+
+    # TODO: get these tests to detect gss-ntlmssp once it is installed
+    """
+    @ktu.gssapi_extension_test('ggf', 'Global Grid Forum')
+    @ktu.gssapi_extension_test('password', 'Add Credential with Password')
+    def test_set_sec_context_option(self):
+        # TODO: skip the test if gss-ntlmssp is not installed, MIT krb5 has not
+        # implemented any OID options for set_sec_context_option
+        ntlm_mech = gb.OID.from_int_seq("1.3.6.1.4.1.311.2.2.10")
+        reset_mech = gb.OID.from_int_seq("1.3.6.1.4.1.7165.655.1.3")
+
+        username = gb.import_name(name=b"user",
+                                  name_type=gb.NameType.user)
+        server = gb.import_name(name=b"server",
+                                name_type=gb.NameType.hostbased_service)
+        cred = gb.acquire_cred_with_password(name=username,
+                                             password=b"password",
+                                             mechs=[ntlm_mech])
+        orig_context = gb.init_sec_context(server, creds=cred.creds,
+                                           mech=ntlm_mech)[0]
+
+        out_context = gb.set_sec_context_option(reset_mech,
+                                                context=orig_context,
+                                                value=b"\x00" * 4)
+        id(orig_context).should_be(id(out_context))
+    """
+
+    @ktu.gssapi_extension_test('ggf', 'Global Grid Forum')
+    def test_set_sec_context_option_fail(self):
+        # because MIT krb5 doesn't implement any OID's for
+        # gss_set_sec_context_option, we just need to query any OID and it will
+        # raise an exception
+        gb.set_sec_context_option.should_raise(gb.GSSError,
+                                               gb.OID.from_int_seq("1.2.3.4"))
+
 
 class TestIntEnumFlagSet(unittest.TestCase):
     def test_create_from_int(self):