Don't use os.system() in compilemessages.

Fixes #19584.

This implies stop storing file path command line arguments in envvars as
a security measure to start relying on with Popen's shell=False instead,
and addition of an 'utils' module.

Thanks kmichel_wgs for the report.

django/core/management/commands/compilemessages.py

@@ -2,9 +2,10 @@ from __future__ import unicode_literals
 
 import codecs
 import os
-import sys
 from optparse import make_option
+
 from django.core.management.base import BaseCommand, CommandError
+from django.core.management.utils import popen_wrapper
 from django.utils._os import npath
 
 def has_bom(fn):
@@ -41,18 +42,15 @@ def compile_messages(stderr, locale=None):
                     if has_bom(fn):
                         raise CommandError("The %s file has a BOM (Byte Order Mark). Django only supports .po files encoded in UTF-8 and without any BOM." % fn)
                     pf = os.path.splitext(fn)[0]
-                    # Store the names of the .mo and .po files in an environment
-                    # variable, rather than doing a string replacement into the
-                    # command, so that we can take advantage of shell quoting, to
-                    # quote any malicious characters/escaping.
-                    # See http://cyberelk.net/tim/articles/cmdline/ar01s02.html
-                    os.environ['djangocompilemo'] = npath(pf + '.mo')
-                    os.environ['djangocompilepo'] = npath(pf + '.po')
-                    if sys.platform == 'win32': # Different shell-variable syntax
-                        cmd = 'msgfmt --check-format -o "%djangocompilemo%" "%djangocompilepo%"'
-                    else:
-                        cmd = 'msgfmt --check-format -o "$djangocompilemo" "$djangocompilepo"'
-                    os.system(cmd)
+                    program = 'msgfmt'
+                    args = [program, '--check-format', '-o', npath(pf + '.mo'), npath(pf + '.po')]
+                    output, errors, status = popen_wrapper(args)
+                    if status:
+                        if errors:
+                            msg = "Execution of %s failed: %s" % (program, errors)
+                        else:
+                            msg = "Execution of %s failed" % program
+                        raise CommandError(msg)
 
 
 class Command(BaseCommand):

django/core/management/utils.py

@@ -0,0 +1,14 @@
+import os
+from subprocess import PIPE, Popen
+
+
+def popen_wrapper(args):
+    """
+    Friendly wrapper around Popen.
+
+    Returns stdout output, stderr output and OS status code.
+    """
+    p = Popen(args, shell=False, stdout=PIPE, stderr=PIPE,
+              close_fds=os.name != 'nt', universal_newlines=True)
+    output, errors = p.communicate()
+    return output, errors, p.returncode

tests/i18n/commands/compilation.py

@@ -99,3 +99,22 @@ class MultipleLocaleCompilationTests(MessageCompilationTests):
 
         self.assertTrue(os.path.exists(self.MO_FILE_HR))
         self.assertTrue(os.path.exists(self.MO_FILE_FR))
+
+
+class CompilationErrorHandling(MessageCompilationTests):
+
+    LOCALE='ja'
+    MO_FILE='locale/%s/LC_MESSAGES/django.mo' % LOCALE
+
+    def setUp(self):
+        super(CompilationErrorHandling, self).setUp()
+        self.addCleanup(self._rmfile, os.path.join(test_dir, self.MO_FILE))
+
+    def _rmfile(self, filepath):
+        if os.path.exists(filepath):
+            os.remove(filepath)
+
+    def test_error_reported_by_msgfmt(self):
+        os.chdir(test_dir)
+        with self.assertRaises(CommandError):
+            call_command('compilemessages', locale=self.LOCALE, stderr=StringIO())

tests/i18n/commands/locale/ja/LC_MESSAGES/django.po

@@ -0,0 +1,21 @@
+# SOME DESCRIPTIVE TITLE.
+# Copyright (C) YEAR THE PACKAGE'S COPYRIGHT HOLDER
+# This file is distributed under the same license as the PACKAGE package.
+# FIRST AUTHOR <EMAIL@ADDRESS>, YEAR.
+#
+msgid ""
+msgstr ""
+"Project-Id-Version: PACKAGE VERSION\n"
+"Report-Msgid-Bugs-To: \n"
+"POT-Creation-Date: 2011-12-04 04:59-0600\n"
+"PO-Revision-Date: 2013-02-26 21:29-0300\n"
+"Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
+"Language-Team: LANGUAGE <LL@li.org>\n"
+"Language: ja\n"
+"MIME-Version: 1.0\n"
+"Content-Type: text/plain; charset=UTF-8\n"
+"Content-Transfer-Encoding: 8bit\n"
+"Plural-Forms: nplurals=1; plural=0;\n"
+
+#, brainfuck-format
+msgwhat!? "This is an invalid PO file. GNU msgfmt should reject it."

tests/i18n/tests.py

@@ -41,7 +41,8 @@ if can_run_extraction_tests:
         MultipleLocaleExtractionTests)
 if can_run_compilation_tests:
     from .commands.compilation import (PoFileTests, PoFileContentsTests,
-        PercentRenderingTests, MultipleLocaleCompilationTests)
+        PercentRenderingTests, MultipleLocaleCompilationTests,
+        CompilationErrorHandling)
 from .contenttypes.tests import ContentTypeTests
 from .forms import I18nForm, SelectDateForm, SelectDateWidget, CompanyForm
 from .models import Company, TestModel