This patch provides Python ucred support.  It may be contributed upstream at
some point, but the suitability (or lack thereof) has not yet been determined.

diff --git Python-2.6.4/Modules/ucred.c Python-2.6.4/Modules/ucred.c
new file mode 100644
--- Python-3.9.1/Modules/ucred.c
+++ Python-3.9.1/Modules/ucred.c
@@ -0,0 +1,404 @@
+/*
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ *
+ * Copyright (c) 2011, Oracle and/or its affiliates. All rights reserved.
+ */
+
+#include <Python.h>
+
+#include <stdio.h>
+#include <priv.h>
+#include <ucred.h>
+#include <ctype.h>
+#include <tsol/label.h>
+
+typedef struct {
+	PyObject_HEAD
+	ucred_t *ucred;
+} pyucred_t;
+
+#define pyucred_getlongid(name, type)				\
+	static PyObject *					\
+	pyucred_get##name(pyucred_t *uc)			\
+	{ 							\
+		type val;					\
+								\
+		if (uc->ucred == NULL) {			\
+			errno = EINVAL;				\
+			PyErr_SetFromErrno(PyExc_OSError);	\
+			return (NULL);				\
+		}						\
+								\
+		if ((val = ucred_get##name(uc->ucred)) == -1) {	\
+			PyErr_SetFromErrno(PyExc_OSError);	\
+			return (NULL);				\
+		}						\
+								\
+		return (Py_BuildValue("l", (long)val));		\
+	}
+
+pyucred_getlongid(euid, uid_t)
+pyucred_getlongid(ruid, uid_t)
+pyucred_getlongid(suid, uid_t)
+pyucred_getlongid(egid, gid_t)
+pyucred_getlongid(rgid, gid_t)
+pyucred_getlongid(sgid, gid_t)
+pyucred_getlongid(pid, pid_t)
+pyucred_getlongid(projid, projid_t)
+pyucred_getlongid(zoneid, zoneid_t)
+
+static PyObject *
+pyucred_getgroups(pyucred_t *uc)
+{
+	const gid_t *groups;
+	PyObject *list;
+	int len;
+	int i;
+
+	if (uc->ucred == NULL) {
+		errno = EINVAL;
+		PyErr_SetFromErrno(PyExc_OSError);
+		return (NULL);
+	}
+
+	if ((len = ucred_getgroups(uc->ucred, &groups)) == -1) {
+		PyErr_SetFromErrno(PyExc_OSError);
+		return (NULL);
+	}
+
+	if ((list = PyList_New(len)) == NULL)
+		return (NULL);
+
+	for (i = 0; i < len; i++) {
+		PyObject *gid = Py_BuildValue("l", (long)groups[i]);
+		if (PyList_SetItem(list, i, gid) == -1)
+			return (NULL);
+	}
+
+	return (list);
+}
+
+static PyObject *
+pyucred_getlabel(pyucred_t *uc)
+{
+	m_label_t *label;
+	PyObject *ret;
+	char *str;
+
+	if (uc->ucred == NULL) {
+		errno = EINVAL;
+		PyErr_SetFromErrno(PyExc_OSError);
+		return (NULL);
+	}
+
+	label = ucred_getlabel(uc->ucred);
+	if (label == NULL)
+		return (Py_BuildValue("s", ""));
+
+	if (label_to_str(label, &str, M_LABEL, DEF_NAMES) == -1) {
+		PyErr_SetFromErrno(PyExc_OSError);
+		return (NULL);
+	}
+
+	ret = Py_BuildValue("s", str);
+	free(str);
+	return (ret);
+}
+
+static PyObject *
+pyucred_getpflags(pyucred_t *uc, PyObject *args, PyObject *kwargs)
+{
+	static char *kwlist[] = { "flags", NULL };
+	uint_t flags;
+
+	if (uc->ucred == NULL) {
+		errno = EINVAL;
+		PyErr_SetFromErrno(PyExc_OSError);
+		return (NULL);
+	}
+
+	if (!PyArg_ParseTupleAndKeywords(args, kwargs, "i", kwlist,
+	    &flags))
+		return (NULL);
+
+	if ((flags = ucred_getpflags(uc->ucred, flags)) == (uint_t)-1) {
+		PyErr_SetFromErrno(PyExc_OSError);
+		return (NULL);
+	}
+
+	return (Py_BuildValue("i", flags));
+}
+
+static PyObject *
+pyucred_has_priv(pyucred_t *uc, PyObject *args, PyObject *kwargs)
+{
+	static char *kwlist[] = { "set", "priv", NULL };
+	const priv_set_t *privs;
+	const char *set;
+	const char *priv;
+
+	if (uc->ucred == NULL) {
+		errno = EINVAL;
+		PyErr_SetFromErrno(PyExc_OSError);
+		return (NULL);
+	}
+
+	if (!PyArg_ParseTupleAndKeywords(args, kwargs, "ss", kwlist,
+	    &set, &priv))
+		return (NULL);
+
+	if ((privs = ucred_getprivset(uc->ucred, set)) == NULL) {
+		PyErr_SetFromErrno(PyExc_OSError);
+		return (NULL);
+	}
+
+	if (priv_ismember(privs, priv)) {
+		Py_INCREF(Py_True);
+		return Py_True;
+	}
+
+	Py_INCREF(Py_False);
+	return Py_False;
+}
+
+PyDoc_STRVAR(pyucred_getlabel_doc,
+    "getlabel() -> string\n"
+    "\n"
+    "Return the Trusted Extensions label string, or an "
+    "empty string if not available. The label string is "
+    "converted using the default name and M_LABEL (human-readable). "
+    "Raises OSError. See label_to_str(3TSOL).");
+PyDoc_STRVAR(pyucred_getpflags_doc,
+    "getpflags(flags) -> int\n"
+    "\n"
+    "Return the values of the specified privilege flags.");
+PyDoc_STRVAR(pyucred_has_priv_doc,
+    "has_priv(set, priv) -> bool\n"
+    "\n"
+    "Return true if the given privilege is set in the "
+    "specified set. Raises OSError if the set or privilege is "
+    "invalid, or a problem occurs.\n"
+    "\n"
+    "Currently, the following privilege sets are defined, as "
+    "described in privileges(5):\n"
+    "\n"
+    "Effective\n"
+    "Permitted\n"
+    "Inheritable\n"
+    "Limit\n");
+
+static PyMethodDef pyucred_methods[] = {
+	{ "geteuid", (PyCFunction)pyucred_geteuid, METH_NOARGS,
+	    "Return the effective user ID." },
+	{ "getruid", (PyCFunction)pyucred_getruid, METH_NOARGS,
+	    "Return the real user ID." },
+	{ "getsuid", (PyCFunction)pyucred_getsuid, METH_NOARGS,
+	    "Return the saved user ID." },
+	{ "getegid", (PyCFunction)pyucred_getegid, METH_NOARGS,
+	    "Return the effective group ID." },
+	{ "getrgid", (PyCFunction)pyucred_getrgid, METH_NOARGS,
+	    "Return the real group ID." },
+	{ "getsgid", (PyCFunction)pyucred_getsgid, METH_NOARGS,
+	    "Return the saved group ID." },
+	{ "getpid", (PyCFunction)pyucred_getpid, METH_NOARGS,
+	    "Return the effective user ID." },
+	{ "getprojid", (PyCFunction)pyucred_getprojid, METH_NOARGS,
+	    "Return the project ID." },
+	{ "getzoneid", (PyCFunction)pyucred_getzoneid, METH_NOARGS,
+	    "Return the zone ID." },
+	{ "getgroups", (PyCFunction)pyucred_getgroups, METH_NOARGS,
+	    "Return a list of group IDs." },
+	{ "getlabel", (PyCFunction)pyucred_getlabel, METH_NOARGS,
+	    pyucred_getlabel_doc },
+	{ "getpflags", (PyCFunction)pyucred_getpflags,
+	    METH_VARARGS|METH_KEYWORDS, pyucred_getpflags_doc },
+	{ "has_priv", (PyCFunction)pyucred_has_priv,
+	    METH_VARARGS|METH_KEYWORDS, pyucred_has_priv_doc },
+	{ NULL, NULL }
+};
+
+static int
+pyucred_init(PyObject *self, PyObject *args, PyObject *kwargs)
+{
+	pyucred_t *uc = (pyucred_t *)self;
+	uc->ucred = NULL;
+	return (0);
+}
+
+static void
+pyucred_dealloc(PyObject *self)
+{
+	pyucred_t *uc = (pyucred_t *)self;
+	if (uc->ucred != NULL)
+		ucred_free(uc->ucred);
+	Py_TYPE(self)->tp_free(self);
+}
+
+static PyTypeObject pyucred_type = {
+	PyVarObject_HEAD_INIT(NULL, 0)
+	"ucred.ucred",             /*tp_name*/
+	sizeof (pyucred_t),        /*tp_basicsize*/
+	0,                         /*tp_itemsize*/
+	pyucred_dealloc,           /*tp_dealloc*/
+	0,                         /*tp_print*/
+	0,                         /*tp_getattr*/
+	0,                         /*tp_setattr*/
+	0,                         /*tp_reserved*/
+	0,                         /*tp_repr*/
+	0,                         /*tp_as_number*/
+	0,                         /*tp_as_sequence*/
+	0,                         /*tp_as_mapping*/
+	0,                         /*tp_hash */
+	0,                         /*tp_call*/
+	0,                         /*tp_str*/
+	0,                         /*tp_getattro*/
+	0,                         /*tp_setattro*/
+	0,                         /*tp_as_buffer*/
+	Py_TPFLAGS_DEFAULT,        /*tp_flags*/
+	"user credentials",        /*tp_doc */
+	0,		           /* tp_traverse */
+	0,		           /* tp_clear */
+	0,		           /* tp_richcompare */
+	0,		           /* tp_weaklistoffset */
+	0,		           /* tp_iter */
+	0,		           /* tp_iternext */
+	pyucred_methods,           /* tp_methods */
+	0,                         /* tp_members */
+	0,                         /* tp_getset */
+	0,                         /* tp_base */
+	0,                         /* tp_dict */
+	0,                         /* tp_descr_get */
+	0,                         /* tp_descr_set */
+	0,                         /* tp_dictoffset */
+	(initproc)pyucred_init,    /* tp_init */
+	0,                         /* tp_alloc */
+	0,                         /* tp_new */
+	0,                         /* tp_free */
+	0,                         /* tp_is_gc */
+};
+
+static PyObject *
+pyucred_new(const ucred_t *uc)
+{
+	pyucred_t *self;
+
+	self = (pyucred_t *)PyObject_CallObject((PyObject *)&pyucred_type, NULL);
+
+	if (self == NULL)
+		return (NULL);
+
+	self->ucred = (ucred_t *)uc;
+
+	return ((PyObject *)self);
+}
+
+static PyObject *
+pyucred_get(PyObject *o, PyObject *args, PyObject *kwargs)
+{
+	static char *kwlist[] = { "pid", NULL };
+	ucred_t *ucred = NULL;
+	int pid;
+
+	if (!PyArg_ParseTupleAndKeywords(args, kwargs, "i", kwlist,
+	    &pid))
+		return (NULL);
+
+	ucred = ucred_get(pid);
+
+	if (ucred == NULL) {
+		PyErr_SetFromErrno(PyExc_OSError);
+		return (NULL);
+	}
+
+	return (pyucred_new(ucred));
+}
+
+static PyObject *
+pyucred_getpeer(PyObject *o, PyObject *args, PyObject *kwargs)
+{
+	static char *kwlist[] = { "fd", NULL };
+	ucred_t *ucred = NULL;
+	int fd;
+
+	if (!PyArg_ParseTupleAndKeywords(args, kwargs, "i", kwlist,
+	    &fd))
+		return (NULL);
+
+	if (getpeerucred(fd, &ucred) == -1) {
+		PyErr_SetFromErrno(PyExc_OSError);
+		return (NULL);
+	}
+
+	return (pyucred_new(ucred));
+}
+
+PyDoc_STRVAR(pyucred_get_doc,
+    "get(pid) -> ucred\n"
+    "\n"
+    "Return the credentials of the specified process ID. "
+    "Raises OSError. See ucred_get(3C).");
+PyDoc_STRVAR(pyucred_getpeer_doc,
+    "getpeer(fd) -> ucred\n"
+    "\n"
+    "Return the credentials of the peer endpoint of a "
+    "connection-oriented socket (SOCK_STREAM) or STREAM fd "
+    "at the time the endpoint was created or the connection "
+    "was established. Raises OSError. See getpeerucred(3C).");
+
+static struct PyMethodDef pyucred_module_methods[] = {
+	{ "get", (PyCFunction) pyucred_get,
+	  METH_VARARGS|METH_KEYWORDS, pyucred_get_doc },
+	{ "getpeer", (PyCFunction) pyucred_getpeer,
+	  METH_VARARGS|METH_KEYWORDS, pyucred_getpeer_doc },
+	{ NULL, NULL, 0, NULL }
+};
+
+PyDoc_STRVAR(pyucred_module_doc,
+    "This module provides an interface to the user credential access "
+    "methods, obtainable either by process ID or file descriptor.");
+
+PyMODINIT_FUNC
+PyInit_ucred (void)
+{
+	PyObject *m;
+
+	static struct PyModuleDef moduledef = {
+	    PyModuleDef_HEAD_INIT,
+	    "ucred",
+	    pyucred_module_doc,
+	    -1,
+	    pyucred_module_methods,
+	    NULL,
+	    NULL,
+	    NULL,
+	    NULL,
+	};
+
+	m = PyModule_Create(&moduledef);
+
+	pyucred_type.tp_new = PyType_GenericNew;
+	if (PyType_Ready(&pyucred_type) < 0)
+		return NULL;
+
+	Py_INCREF(&pyucred_type);
+
+	PyModule_AddObject(m, "ucred", (PyObject *)&pyucred_type);
+
+	return m;
+}
--- Python-3.9.1/setup.py
+++ Python-3.9.1/setup.py
@@ -1814,6 +1814,13 @@ class PyBuildExt(build_ext):
         else:
             self.missing.append('_uuid')
 
+    def detect_ucred(self):
+        # ucred module (Solaris)
+        ucred_inc = find_file('ucred.h', [], self.inc_dirs)
+        tsol_inc = find_file('tsol/label.h', [], self.inc_dirs)
+        if ucred_inc is not None and tsol_inc is not None:
+            self.add(Extension('ucred', ['ucred.c'], libraries=['tsol']))
+
     def detect_modules(self):
         self.configure_compiler()
         self.init_inc_lib_dirs()
@@ -1834,6 +1841,7 @@ class PyBuildExt(build_ext):
         self.detect_expat_elementtree()
         self.detect_multibytecodecs()
         self.detect_decimal()
+        self.detect_ucred()
         self.detect_ctypes()
         self.detect_multiprocessing()
         if not self.detect_tkinter():
--- Python-3.9.1/Lib/test/ucredtest.py
+++ Python-3.9.1/Lib/test/ucredtest.py
@@ -0,0 +1,45 @@
+#!/usr/bin/python3.9
+
+import ucred
+import os
+
+uc = ucred.get(os.getpid())
+
+print("pid = %d" % uc.getpid())
+print("euid = %d" % uc.geteuid())
+print("ruid = %d" % uc.getruid())
+print("suid = %d" % uc.getsuid())
+print("egid = %d" % uc.getegid())
+print("rgid = %d" % uc.getrgid())
+print("sgid = %d" % uc.getsgid())
+print("zoneid = %d" % uc.getzoneid())
+print("projid = %d" % uc.getprojid())
+print("groups = %s" % uc.getgroups())
+print("label = %s" % uc.getlabel())
+
+print("getpflags(0x1) = %d" % uc.getpflags(0x1))
+print("getpflags(0x2) = %d" % uc.getpflags(0x2))
+print("has_priv(Effective, proc_fork) = %d" % uc.has_priv("Effective", "proc_fork"))
+print("has_priv(Permitted, proc_fork) = %d" % uc.has_priv("Permitted", "proc_fork"))
+print("has_priv(Inheritable, proc_fork) = %d" % uc.has_priv("Inheritable", "proc_fork"))
+print("has_priv(Limit, file_setid) = %d" % uc.has_priv("Limit", "file_setid"))
+print("has_priv(Effective, file_setid) = %d" % uc.has_priv("Effective", "file_setid"))
+try:
+    uc.has_priv("Effective", "proc_bork")
+except OSError as e:
+    print(e)
+try:
+    uc.has_priv("Defective", "proc_fork")
+except OSError as e:
+    print(e)
+try:
+    uc.has_priv("Defective", "proc_bork")
+except OSError as e:
+    print(e)
+
+del uc
+uc = ucred.ucred()
+try:
+    uc.getpid()
+except OSError as e:
+    print(e)