Fixed #1135 -- Changed django.core.mail functions not to allow newlines in headers

git-svn-id: http://code.djangoproject.com/svn/django/trunk@1795 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/core/mail.py

@@ -4,6 +4,13 @@ from django.conf.settings import DEFAULT_FROM_EMAIL, EMAIL_HOST, EMAIL_SUBJECT_P
 from email.MIMEText import MIMEText
 import smtplib
 
+class SafeMIMEText(MIMEText):
+    def __setitem__(self, name, val):
+        "Forbids multi-line headers, to prevent header injection."
+        if '\n' in val or '\r' in val:
+            raise ValueError, "Header values can't contain newlines (got %r for header %r)" % (val, name)
+        MIMEText.__setitem__(self, name, val)
+
 def send_mail(subject, message, from_email, recipient_list, fail_silently=False):
     """
     Easy wrapper for sending a single message to a recipient list. All members
@@ -29,7 +36,7 @@ def send_mass_mail(datatuple, fail_silently=False):
         if not recipient_list:
             continue
         from_email = from_email or DEFAULT_FROM_EMAIL
-        msg = MIMEText(message)
+        msg = SafeMIMEText(message)
         msg['Subject'] = subject
         msg['From'] = from_email
         msg['To'] = ', '.join(recipient_list)

docs/email.txt

@@ -114,3 +114,41 @@ receiving a separate e-mail::
         ('Subject', 'Message.', 'from@example.com', ['jane@example.com'],
     )
     send_mass_mail(datatuple)
+
+Preventing header injection
+===========================
+
+**New in Django development version.**
+
+`Header injection`_ is a security exploit in which an attacker inserts extra
+e-mail headers to control the "To:" and "From:" in e-mail messages that your
+scripts generate.
+
+The Django e-mail functions outlined above all protect against header injection
+by forbidding newlines in header values. If any ``subject``, ``from_email`` or
+``recipient_list`` contains a newline, the e-mail function (e.g.
+``send_mail()``) will raise ``ValueError`` and, hence, will not send the
+e-mail. It's your responsibility to validate all data before passing it to the
+e-mail functions.
+
+Here's an example view that takes a ``subject``, ``message`` and ``from_email``
+from the request's POST data, sends that to admin@example.com and redirects to
+"/contact/thanks/" when it's done::
+
+    from django.core.mail import send_mail
+
+    def send_email(request):
+        subject = request.POST.get('subject', '')
+        message = request.POST.get('message', '')
+        from_email = request.POST.get('from_email', '')
+        if subject and message and from_email \
+                and '\n' not in subject and '\n' not in message
+                and '\n' not in from_email:
+            send_mail(subject, message, from_email, ['admin@example.com'])
+            return HttpResponseRedirect('/contact/thanks/')
+        else:
+            # In reality we'd use a manipulator
+            # to get proper validation errors.
+            return HttpResponse('Make sure all fields are entered and valid.')
+
+.. _Header injection: http://securephp.damonkohler.com/index.php/Email_Injection