basic django security key elements worthy noting

Notes on security

XXE injection:
To use these parsers safely, you have to explicitly disable referencing of external entities in the 
SAX parser implementation you use.
problem: 
from django.http import HttpResponse
from lxml import etree
parser = etree.XMLParser(resolve_entities=True)
        try:
            document = etree.fromstring(content, parser)
        except etree.XMLSyntaxError:
            return None
 solution:
 set parser = etree.XMLParser(resolve_entities=False) -- set it to False
 
 disallowing inline DTD is a good defense against this type of attack, 
 but implementing this is specific to the XML parsing engine being used.
 
 Command Injection:
 Should any non alphanumeric characters be encountered, the re.match() method will automatically escape the input,
 preventing malicious control shell characters from being passed to the statlab program.
 
 Although the proposed fix is sufficient to remediate our vulnerable example, 
 the overall logic and security design for os.popen() method can be significantly 
 improved by not accepting user supplied myUid value through the request.GET['username'] parameter.
 
import os
from django.http import HttpResponse
import re

def executeCommand(request):
    myUid = request.GET['username']
    matchResult = re.match(r"[0-9A-Za-z]+$", myUid)
    if not matchResult:
        return HttpResponse("Inva
    out = os.popen("/usr/bin/statlab " + "-" + myUid).read()

    return HttpResponse(out)Copy-paste code here to remove the line numbers.
    
 Session Fixation:
    1. Ensure that only server generated session values are accepted by the application.

    2. Upon a successful login, invalidate the original session value, and re-issue a new session value.

    3. Prevent the application from accepting session values via GET or POST requests and 
    instead store session values within HTTP Cookies only.
    
    def authenticate(request, username, password):
    user = verify_uname_password(username, password)
    if user and user.is_active:
        request.session.flush()
        request.session.cycle_key()

content_length = self.headers.getheaders('content-length')
length = int(content_length[0]) if content_length else 0

pickledError = self.rfile.read(length)

exceptionRecord = cPickle.loads(base64.b64decode(pickledError))

self._set_headers()
jsonRecordError = self.rfile.read(length)
exceptionRecordJson = json.loads(jsonRecordError)
try:
exceptionRecord = ExceptionRecord(exceptionRecordJson["version"], exceptionRecordJson["log"], exceptionRecordJson["userID"])
saveError(exceptionRecord)
self._set_headers()
self.wfile.write(createJSONSuccess(exceptionRecord));
except (ValueError, TypeError, NameError) as e:
log_error(e, exceptionRecord)
self._set_error_headers()
self.wfile.write(createJSONError(e,exceptionRecord));