gh-87868: Sort and remove duplicates in getenvironment() (GH-102731)

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
Co-authored-by: Pieter Eendebak <pieter.eendebak@gmail.com>
Co-authored-by: Erlend E. Aasland <erlend.aasland@protonmail.com>

3 files changed, 194 insertions, 4 deletions

diff --git a/Lib/test/test_subprocess.py b/Lib/test/test_subprocess.py
index 6d3228b..102e697 100644
--- a/Lib/test/test_subprocess.py
+++ b/Lib/test/test_subprocess.py
@@ -791,6 +791,19 @@ class ProcessTestCase(BaseTestCase):
             stdout, stderr = p.communicate()
             self.assertEqual(stdout, b"orange")
 
+    @unittest.skipUnless(sys.platform == "win32", "Windows only issue")
+    def test_win32_duplicate_envs(self):
+        newenv = os.environ.copy()
+        newenv["fRUit"] = "cherry"
+        newenv["fruit"] = "lemon"
+        newenv["FRUIT"] = "orange"
+        newenv["frUit"] = "banana"
+        with subprocess.Popen(["CMD", "/c", "SET", "fruit"],
+                              stdout=subprocess.PIPE,
+                              env=newenv) as p:
+            stdout, _ = p.communicate()
+            self.assertEqual(stdout.strip(), b"frUit=banana")
+
     # Windows requires at least the SYSTEMROOT environment variable to start
     # Python
     @unittest.skipIf(sys.platform == 'win32',
@@ -822,6 +835,17 @@ class ProcessTestCase(BaseTestCase):
                                if not is_env_var_to_ignore(k)]
             self.assertEqual(child_env_names, [])
 
+    def test_one_environment_variable(self):
+        newenv = {'fruit': 'orange'}
+        cmd = [sys.executable, '-c',
+                               'import sys,os;'
+                               'sys.stdout.write("fruit="+os.getenv("fruit"))']
+        if sys.platform == "win32":
+            cmd = ["CMD", "/c", "SET", "fruit"]
+        with subprocess.Popen(cmd, stdout=subprocess.PIPE, env=newenv) as p:
+            stdout, _ = p.communicate()
+            self.assertTrue(stdout.startswith(b"fruit=orange"))
+
     def test_invalid_cmd(self):
         # null character in the command name
         cmd = sys.executable + '\0'
@@ -862,6 +886,19 @@ class ProcessTestCase(BaseTestCase):
             stdout, stderr = p.communicate()
             self.assertEqual(stdout, b"orange=lemon")
 
+    @unittest.skipUnless(sys.platform == "win32", "Windows only issue")
+    def test_win32_invalid_env(self):
+        # '=' in the environment variable name
+        newenv = os.environ.copy()
+        newenv["FRUIT=VEGETABLE"] = "cabbage"
+        with self.assertRaises(ValueError):
+            subprocess.Popen(ZERO_RETURN_CMD, env=newenv)
+
+        newenv = os.environ.copy()
+        newenv["==FRUIT"] = "cabbage"
+        with self.assertRaises(ValueError):
+            subprocess.Popen(ZERO_RETURN_CMD, env=newenv)
+
     def test_communicate_stdin(self):
         p = subprocess.Popen([sys.executable, "-c",
                               'import sys;'
diff --git a/Misc/NEWS.d/next/Windows/2023-03-15-23-53-45.gh-issue-87868.4C36oQ.rst b/Misc/NEWS.d/next/Windows/2023-03-15-23-53-45.gh-issue-87868.4C36oQ.rst
new file mode 100644
index 0000000..37e8103
--- /dev/null
+++ b/Misc/NEWS.d/next/Windows/2023-03-15-23-53-45.gh-issue-87868.4C36oQ.rst
@@ -0,0 +1,2 @@
+Correctly sort and remove duplicate environment variables in
+:py:func:`!_winapi.CreateProcess`.
diff --git a/Modules/_winapi.c b/Modules/_winapi.c
index 8c48b6f..a26850e 100644
--- a/Modules/_winapi.c
+++ b/Modules/_winapi.c
@@ -774,12 +774,157 @@ gethandle(PyObject* obj, const char* name)
     return ret;
 }
 
+static PyObject *
+sortenvironmentkey(PyObject *module, PyObject *item)
+{
+    return _winapi_LCMapStringEx_impl(NULL, LOCALE_NAME_INVARIANT,
+                                      LCMAP_UPPERCASE, item);
+}
+
+static PyMethodDef sortenvironmentkey_def = {
+    "sortenvironmentkey", _PyCFunction_CAST(sortenvironmentkey), METH_O, "",
+};
+
+static int
+sort_environment_keys(PyObject *keys)
+{
+    PyObject *keyfunc = PyCFunction_New(&sortenvironmentkey_def, NULL);
+    if (keyfunc == NULL) {
+        return -1;
+    }
+    PyObject *kwnames = Py_BuildValue("(s)", "key");
+    if (kwnames == NULL) {
+        Py_DECREF(keyfunc);
+        return -1;
+    }
+    PyObject *args[] = { keys, keyfunc };
+    PyObject *ret = PyObject_VectorcallMethod(&_Py_ID(sort), args, 1, kwnames);
+    Py_DECREF(keyfunc);
+    Py_DECREF(kwnames);
+    if (ret == NULL) {
+        return -1;
+    }
+    Py_DECREF(ret);
+
+    return 0;
+}
+
+static int
+compare_string_ordinal(PyObject *str1, PyObject *str2, int *result)
+{
+    wchar_t *s1 = PyUnicode_AsWideCharString(str1, NULL);
+    if (s1 == NULL) {
+        return -1;
+    }
+    wchar_t *s2 = PyUnicode_AsWideCharString(str2, NULL);
+    if (s2 == NULL) {
+        PyMem_Free(s1);
+        return -1;
+    }
+    *result = CompareStringOrdinal(s1, -1, s2, -1, TRUE);
+    PyMem_Free(s1);
+    PyMem_Free(s2);
+    return 0;
+}
+
+static PyObject *
+dedup_environment_keys(PyObject *keys)
+{
+    PyObject *result = PyList_New(0);
+    if (result == NULL) {
+        return NULL;
+    }
+
+    // Iterate over the pre-ordered keys, check whether the current key is equal
+    // to the next key (ignoring case), if different, insert the current value
+    // into the result list. If they are equal, do nothing because we always
+    // want to keep the last inserted one.
+    for (Py_ssize_t i = 0; i < PyList_GET_SIZE(keys); i++) {
+        PyObject *key = PyList_GET_ITEM(keys, i);
+
+        // The last key will always be kept.
+        if (i + 1 == PyList_GET_SIZE(keys)) {
+            if (PyList_Append(result, key) < 0) {
+                Py_DECREF(result);
+                return NULL;
+            }
+            continue;
+        }
+
+        PyObject *next_key = PyList_GET_ITEM(keys, i + 1);
+        int compare_result;
+        if (compare_string_ordinal(key, next_key, &compare_result) < 0) {
+            Py_DECREF(result);
+            return NULL;
+        }
+        if (compare_result == CSTR_EQUAL) {
+            continue;
+        }
+        if (PyList_Append(result, key) < 0) {
+            Py_DECREF(result);
+            return NULL;
+        }
+    }
+
+    return result;
+}
+
+static PyObject *
+normalize_environment(PyObject *environment)
+{
+    PyObject *keys = PyMapping_Keys(environment);
+    if (keys == NULL) {
+        return NULL;
+    }
+
+    if (sort_environment_keys(keys) < 0) {
+        Py_DECREF(keys);
+        return NULL;
+    }
+
+    PyObject *normalized_keys = dedup_environment_keys(keys);
+    Py_DECREF(keys);
+    if (normalized_keys == NULL) {
+        return NULL;
+    }
+
+    PyObject *result = PyDict_New();
+    if (result == NULL) {
+        Py_DECREF(normalized_keys);
+        return NULL;
+    }
+
+    for (int i = 0; i < PyList_GET_SIZE(normalized_keys); i++) {
+        PyObject *key = PyList_GET_ITEM(normalized_keys, i);
+        PyObject *value = PyObject_GetItem(environment, key);
+        if (value == NULL) {
+            Py_DECREF(normalized_keys);
+            Py_DECREF(result);
+            return NULL;
+        }
+
+        int ret = PyObject_SetItem(result, key, value);
+        Py_DECREF(value);
+        if (ret < 0) {
+            Py_DECREF(normalized_keys);
+            Py_DECREF(result);
+            return NULL;
+        }
+    }
+
+    Py_DECREF(normalized_keys);
+
+    return result;
+}
+
 static wchar_t *
 getenvironment(PyObject* environment)
 {
     Py_ssize_t i, envsize, totalsize;
     wchar_t *buffer = NULL, *p, *end;
-    PyObject *keys, *values;
+    PyObject *normalized_environment = NULL;
+    PyObject *keys = NULL;
+    PyObject *values = NULL;
 
     /* convert environment dictionary to windows environment string */
     if (! PyMapping_Check(environment)) {
@@ -788,11 +933,16 @@ getenvironment(PyObject* environment)
         return NULL;
     }
 
-    keys = PyMapping_Keys(environment);
-    if (!keys) {
+    normalized_environment = normalize_environment(environment);
+    if (normalize_environment == NULL) {
         return NULL;
     }
-    values = PyMapping_Values(environment);
+
+    keys = PyMapping_Keys(normalized_environment);
+    if (!keys) {
+        goto error;
+    }
+    values = PyMapping_Values(normalized_environment);
     if (!values) {
         goto error;
     }
@@ -884,6 +1034,7 @@ getenvironment(PyObject* environment)
 
 cleanup:
 error:
+    Py_XDECREF(normalized_environment);
     Py_XDECREF(keys);
     Py_XDECREF(values);
     return buffer;