On Mon, May 01, 2023 at 03:41:37PM -0400, Jon LaBadie via Postfix-users wrote:
> I've been getting a lot of spam with Date: headers
> containing future dates, typically 1 year.
>
> I don't find any header checks that would look for
> this type of message. Have I over looked it?
>
> In the meantime I've implemented a script and procmail
> rule to examine my messages. But that is post-delivery
> and per-user.
I have a Python milter that defers some future-dated messages.
...
def __init__(self):
self.__id = Milter.uniqueID()
self.__ipname = None
self.__ip = None
self.__port = None
self.__from = None
self.__now = time.time()
...
...
def header(self, name, hval):
"""header callback gets called for each header
"""
if config.debug:
print("%s: %s" % (name, hval))
lc = name.lower()
# ...
if ... selection criteria ... :
if lc == "date":
tm = email.utils.parsedate_tz(hval)
if tm is not None:
try:
t = email.utils.mktime_tz(tm)
dt = t - self.__now
if config.debug:
print("Then %f, now %f, delta %f" % (t, self.__now,
dt))
if ... no extenuating circumstances ...:
floor = -... allowance for clock drift ...
else:
floor = ... minimum delay penalty ...
if dt > floor:
self.setreply("454", xcode="4.7.0", msg="No thanks")
return Milter.TEMPFAIL
except Exception as _: pass
return Milter.CONTINUE
Some messages have to arrive some time after the implied date, some can
arrive a short time before, and some are not restricted at all. No
message is refused if the remote MTA is willing to retry long enough.
The logic is narrowly targetted at a particular pattern of abuse.
--
Viktor.
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