# documentação Django 2.0.8

# Código fonte para django.middleware.security

    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=None):
            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.xss_filter = settings.SECURE_BROWSER_XSS_FILTER
            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.get_response = get_response

        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(
                    "https://%s%s" % (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):
                sts_header = "max-age=%s" % self.sts_seconds
                if self.sts_include_subdomains:
                    sts_header = sts_header + "; includeSubDomains"
                if self.sts_preload:
                    sts_header = sts_header + "; preload"
                response["strict-transport-security"] = sts_header

            if self.content_type_nosniff and 'x-content-type-options' not in response:
                response["x-content-type-options"] = "nosniff"

            if self.xss_filter and 'x-xss-protection' not in response:
                response["x-xss-protection"] = "1; mode=block"

            return response