python · serhiy-storchaka · Jun 24, 2017 · Jun 23, 2017
diff --git a/Lib/test/test_subprocess.py b/Lib/test/test_subprocess.py
@@ -385,6 +385,46 @@ def test_env(self):
        self.addCleanup(p.stdout.close)
        self.assertEqual(p.stdout.read(), "orange")

+    def test_invalid_cmd(self):
+        # null character in the command name
+        cmd = sys.executable + '\0'
+        with self.assertRaises(TypeError):
+            subprocess.Popen([cmd, "-c", "pass"])
+
+        # null character in the command argument
+        with self.assertRaises(TypeError):
+            subprocess.Popen([sys.executable, "-c", "pass#\0"])
+
+    def test_invalid_env(self):
+        # null character in the enviroment variable name
+        newenv = os.environ.copy()
+        newenv["FRUIT\0VEGETABLE"] = "cabbage"
+        with self.assertRaises(TypeError):
+            subprocess.Popen([sys.executable, "-c", "pass"], env=newenv)
+
+        # null character in the enviroment variable value
+        newenv = os.environ.copy()
+        newenv["FRUIT"] = "orange\0VEGETABLE=cabbage"
+        with self.assertRaises(TypeError):
+            subprocess.Popen([sys.executable, "-c", "pass"], env=newenv)
+
+        # equal character in the enviroment variable name
+        newenv = os.environ.copy()
+        newenv["FRUIT=ORANGE"] = "lemon"
+        with self.assertRaises(ValueError):
+            subprocess.Popen([sys.executable, "-c", "pass"], env=newenv)
+
+        # equal character in the enviroment variable value
+        newenv = os.environ.copy()
+        newenv["FRUIT"] = "orange=lemon"
+        p = subprocess.Popen([sys.executable, "-c",
+                              'import sys, os;'
+                              'sys.stdout.write(os.getenv("FRUIT"))'],
+                             stdout=subprocess.PIPE,
+                             env=newenv)
+        stdout, stderr = p.communicate()
+        self.assertEqual(stdout, "orange=lemon")
+
    def test_communicate_stdin(self):
        p = subprocess.Popen([sys.executable, "-c",
                              'import sys;'

diff --git a/Misc/NEWS b/Misc/NEWS
@@ -52,6 +52,9 @@ Extension Modules
 Library
 -------

+- [Security] bpo-30730: Prevent environment variables injection in subprocess on
+  Windows.  Prevent passing other environment variables and command arguments.
+
 - [Security] bpo-30694: Upgrade expat copy from 2.2.0 to 2.2.1 to get fixes
  of multiple security vulnerabilities including: CVE-2017-9233 (External
  entity infinite loop DoS), CVE-2016-9063 (Integer overflow, re-fix),

diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
@@ -3315,6 +3315,12 @@ posix_execve(PyObject *self, PyObject *args)
        {
            goto fail_2;
        }
+        /* Search from index 1 because on Windows starting '=' is allowed for
+           defining hidden environment variables. */
+        if (*k == '\0' || strchr(k + 1, '=') != NULL) {
+            PyErr_SetString(PyExc_ValueError, "illegal environment variable name");
+            goto fail_2;
+        }

 #if defined(PYOS_OS2)
        /* Omit Pseudo-Env Vars that Would Confuse Programs if Passed On */

diff --git a/PC/_subprocess.c b/PC/_subprocess.c
@@ -352,7 +352,7 @@ getenvironment(PyObject* environment)
    p = PyString_AS_STRING(out);

    for (i = 0; i < envsize; i++) {
-        int ksize, vsize, totalsize;
+        size_t ksize, vsize, totalsize;
        PyObject* key = PyList_GET_ITEM(keys, i);
        PyObject* value = PyList_GET_ITEM(values, i);

@@ -363,10 +363,22 @@ getenvironment(PyObject* environment)
        }
        ksize = PyString_GET_SIZE(key);
        vsize = PyString_GET_SIZE(value);
+        if (strlen(PyString_AS_STRING(key)) != ksize ||
+            strlen(PyString_AS_STRING(value)) != vsize)
+        {
+            PyErr_SetString(PyExc_TypeError, "embedded null character");
+            goto error;
+        }
+        /* Search from index 1 because on Windows starting '=' is allowed for
+           defining hidden environment variables. */
+        if (ksize == 0 || strchr(PyString_AS_STRING(key) + 1, '=') != NULL) {
+            PyErr_SetString(PyExc_ValueError, "illegal environment variable name");
+            goto error;
+        }
        totalsize = (p - PyString_AS_STRING(out)) + ksize + 1 +
                                                     vsize + 1 + 1;
        if (totalsize > PyString_GET_SIZE(out)) {
-            int offset = p - PyString_AS_STRING(out);
+            size_t offset = p - PyString_AS_STRING(out);
            if (_PyString_Resize(&out, totalsize + 1024))
                goto exit;
            p = PyString_AS_STRING(out) + offset;