From 6e0da9cea7c2ed652ec645cbbfedaf423b474af9 Mon Sep 17 00:00:00 2001
From: Faelysse <L0g1n@outlook.cz>
Date: Thu, 6 Sep 2018 14:46:07 +0200
Subject: [PATCH] HTTP header date made independent of locale, fixes #1997

---
 gluon/main.py     |  5 ++---
 gluon/streamer.py |  3 ++-
 gluon/utils.py    | 48 +++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 52 insertions(+), 4 deletions(-)

diff --git a/gluon/main.py b/gluon/main.py
index 9867c87b..e634de37 100644
--- a/gluon/main.py
+++ b/gluon/main.py
@@ -31,7 +31,7 @@ from gluon._compat import Cookie, urllib2
 
 from gluon.fileutils import abspath, write_file
 from gluon.settings import global_settings
-from gluon.utils import web2py_uuid
+from gluon.utils import web2py_uuid, unlocalised_http_header_date
 from gluon.admin import add_path_first, create_missing_folders, create_missing_app_folders
 from gluon.globals import current
 
@@ -199,8 +199,7 @@ def serve_controller(request, response, session):
         ('Content-Type', contenttype('.' + request.extension)),
         ('Cache-Control',
          'no-store, no-cache, must-revalidate, post-check=0, pre-check=0'),
-        ('Expires', time.strftime('%a, %d %b %Y %H:%M:%S GMT',
-                                  time.gmtime())),
+        ('Expires', unlocalised_http_header_date(time.gmtime())),
         ('Pragma', 'no-cache')]
     for key, value in default_headers:
         response.headers.setdefault(key, value)
diff --git a/gluon/streamer.py b/gluon/streamer.py
index 288c71b3..2872f7a5 100644
--- a/gluon/streamer.py
+++ b/gluon/streamer.py
@@ -16,6 +16,7 @@ import time
 import re
 import errno
 from gluon.http import HTTP
+from gluon.utils import unlocalised_http_header_date
 from gluon.contenttype import contenttype
 from gluon._compat import PY2
 
@@ -74,7 +75,7 @@ def stream_file_or_304_or_206(
     stat_file = os.stat(static_file)
     fsize = stat_file[stat.ST_SIZE]
     modified = stat_file[stat.ST_MTIME]
-    mtime = time.strftime('%a, %d %b %Y %H:%M:%S GMT', time.gmtime(modified))
+    mtime = unlocalised_http_header_date(time.gmtime(modified))
     headers.setdefault('Content-Type', contenttype(static_file))
     headers.setdefault('Last-Modified', mtime)
     headers.setdefault('Pragma', 'cache')
diff --git a/gluon/utils.py b/gluon/utils.py
index ea738047..c3e5207f 100644
--- a/gluon/utils.py
+++ b/gluon/utils.py
@@ -462,3 +462,51 @@ def local_html_escape(data, quote=False):
             data = data.replace(b'"', b"&quot;")
             data = data.replace(b'\'', b"&#x27;")
         return data
+
+
+def unlocalised_http_header_date(data):
+    """
+    Converts input datetime to format defined by RFC 7231, section 7.1.1.1
+
+    Previously, %a and %b formats were used for weekday and month names, but
+    those are not locale-safe. uWSGI requires latin1-encodable headers and
+    for example in cs_CS locale, fourth day in week is not encodable in latin1,
+    as it's "Čt".
+
+    Example output: Sun, 06 Nov 1994 08:49:37 GMT
+    """
+
+    short_weekday = {
+        "0": "Sun",
+        "1": "Mon",
+        "2": "Tue",
+        "3": "Wed",
+        "4": "Thu",
+        "5": "Fri",
+        "6": "Sat",
+    }.get(time.strftime("%w", data))
+
+    day_of_month = time.strftime("%d", data)
+
+    short_month = {
+        "01": "Jan",
+        "02": "Feb",
+        "03": "Mar",
+        "04": "Apr",
+        "05": "May",
+        "06": "Jun",
+        "07": "Jul",
+        "08": "Aug",
+        "09": "Sep",
+        "10": "Oct",
+        "11": "Nov",
+        "12": "Dec",
+    }.get(time.strftime("%m", data))
+
+    year_and_time = time.strftime("%Y %H:%M:%S GMT")
+
+    return "{}, {} {} {}".format(
+        short_weekday,
+        day_of_month,
+        short_month,
+        year_and_time)