#36206: Issues in the Existing SecurityMiddleware Code 1. Incorrect use of
response.setdefault() instead of response.headers.setdefault() 2. In the
process_request() method, HTTPS redirection is done While this works,
%-formatting is less readable and slightly less performant than modern
alternatives like f-strings 3. Preventing Overwriting of Existing Headers
--------------------------------+-----------------------------------------
Reporter: Abhijeet Kumar | Type: Bug
Status: new | Component: Uncategorized
Version: 5.1 | Severity: Normal
Keywords: security.py | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
--------------------------------+-----------------------------------------
1. Incorrect use of response.setdefault() instead of
response.headers.setdefault()
Issue:
In the original code, the Cross-Origin-Opener-Policy (COOP) header is set
using:
response.setdefault("Cross-Origin-Opener-Policy",
self.cross_origin_opener_policy)
This is incorrect because:
a. response.setdefault() does not exist in Django’s HttpResponse class.
b. Headers should be set using response.headers.setdefault() to ensure
they are only added if they don’t already exist.
Suggested Modification:
Replace:
response.setdefault("Cross-Origin-Opener-Policy",
self.cross_origin_opener_policy)
With:
response.headers.setdefault("Cross-Origin-Opener-Policy",
self.cross_origin_opener_policy)
2. Improving String Formatting for Readability & Performance
Issue:
In the process_request() method, HTTPS redirection is done using:
return HttpResponsePermanentRedirect(
"https://%s%s"; % (host, request.get_full_path())
)
While this works, %-formatting is less readable and slightly less
performant than modern alternatives like f-strings.
Suggested Modification:
Change:
return HttpResponsePermanentRedirect(
"https://%s%s"; % (host, request.get_full_path())
)
To:
return
HttpResponsePermanentRedirect(f"https://{host}{request.get_full_path()}")
3. Preventing Overwriting of Existing Headers
Issue:
The original code unconditionally sets security headers like:
response.headers["Strict-Transport-Security"] = sts_header
response.headers["X-Content-Type-Options"] = "nosniff"
This could Override existing security policies set by other middleware or
custom responses &
Prevent flexibility in modifying security headers dynamically.
Suggested Modification:
Use setdefault() instead of direct assignment:
response.headers.setdefault("Strict-Transport-Security", sts_header)
response.headers.setdefault("X-Content-Type-Options", "nosniff")
Suggested Code:
import re
from django.conf import settings
from django.http import HttpResponsePermanentRedirect
from django.utils.deprecation import MiddlewareMixin
class SecurityMiddleware(MiddlewareMixin):
def __init__(self, get_response):
super().__init__(get_response)
self.sts_seconds = settings.SECURE_HSTS_SECONDS
self.sts_include_subdomains =
settings.SECURE_HSTS_INCLUDE_SUBDOMAINS
self.sts_preload = settings.SECURE_HSTS_PRELOAD
self.content_type_nosniff = settings.SECURE_CONTENT_TYPE_NOSNIFF
self.redirect = settings.SECURE_SSL_REDIRECT
self.redirect_host = settings.SECURE_SSL_HOST
self.redirect_exempt = [re.compile(r) for r in
settings.SECURE_REDIRECT_EXEMPT]
self.referrer_policy = settings.SECURE_REFERRER_POLICY
self.cross_origin_opener_policy =
settings.SECURE_CROSS_ORIGIN_OPENER_POLICY
def process_request(self, request):
path = request.path.lstrip("/")
if (
self.redirect
and not request.is_secure()
and not any(pattern.search(path) for pattern in
self.redirect_exempt)
):
host = self.redirect_host or request.get_host()
return
HttpResponsePermanentRedirect(f"https://{host}{request.get_full_path()}")
def process_response(self, request, response):
if (
self.sts_seconds
and request.is_secure()
and "Strict-Transport-Security" not in response.headers
):
sts_header = f"max-age={self.sts_seconds}"
if self.sts_include_subdomains:
sts_header += "; includeSubDomains"
if self.sts_preload:
sts_header += "; preload"
response.headers.setdefault("Strict-Transport-Security",
sts_header)
if self.content_type_nosniff:
response.headers.setdefault("X-Content-Type-Options",
"nosniff")
if self.referrer_policy:
# Support a comma-separated string or iterable of values to
allow fallback.
response.headers.setdefault(
"Referrer-Policy",
",".join(
[v.strip() for v in self.referrer_policy.split(",")]
if isinstance(self.referrer_policy, str)
else self.referrer_policy
),
)
if self.cross_origin_opener_policy:
response.headers.setdefault(
"Cross-Origin-Opener-Policy",
self.cross_origin_opener_policy,
)
return response
--
Ticket URL: <https://code.djangoproject.com/ticket/36206>
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