Re: malicious requests?

Hi Alex,

There is no security implication adding 'example.com.' (with trailing
dot) to your ALLOWED_HOSTS setting. There is some more information in
the ALLOWED_HOSTS setting docs.

From https://docs.djangoproject.com/en/1.7/ref/settings/#allowed-hosts

> In previous [<= 1.6.X] versions of Django, if you wanted to also
> allow the fully qualified domain name (FQDN), which some browsers
> can send inthe Host header, you had to explicitly add another
> ALLOWED_HOSTS entry that included a trailing period.

> In Django 1.7, the trailing dot is stripped when performing host
> validation, thus an entry with a trailing dot isn't required.

cheers,
Alasdair



On 22/12/14 12:05, Alex Haylock wrote:
> Thanks Markus.
>
> So, as per the RFC, are 'example.com' and 'example.com.' considered to
> be the same domain, or two separate domains?
>
> Are there any security implications if I add 'example.com.' to
> ALLOWED_HOSTS to cater for these requests?
>
> Thanks,
>
> Alex.
>
> On 22/12/14 11:52, Markus Holtermann wrote:
>> Hey Alex,
>>
>> a trailing . in the host header is valid per RFC 3986:
>> http://tools.ietf.org/html/rfc3986#section-3.2.2:
>>
>> The rightmost domain label of a fully qualified domain name in DNS
>> may be followed by a single "."
>>
>>
>> /Markus
>>
>> On Monday, December 22, 2014 12:44:25 PM UTC+1, Alex Haylock wrote:
>>
>> Are there any known attack vectors that involve appending a period/
>> full-stop to a sites domain name?
>>
>> My Django application throws a handful of errors in production every
>> day:
>>
>> ERROR: Invalid HTTP_HOST header: 'www.example.com.'. You may need to
>> add
>> u'www.example.com <http://www.example.com>.' to ALLOWED_HOSTS.
>>
>> (note the trailing period)
>>
>> Is this malicious behaviour, or just users mistyping the URL?
>>
>> Also, browsers are clearly treating the final '.' as part of the path
>> (as these requests are reaching my application), but Django is treating
>> the '.' as part of the hostname. Which is right?
>>
>> --
>> Regards,
>>
>>
>> Alex
>>
>


--
Alasdair Nicol
Developer, MEMSET

mail: alasdair@memset.com
web: http://www.memset.com/

Memset Ltd., registration number 4504980.
Building 87, Dunsfold Park, Stovolds Hill, Cranleigh, Surrey, GU6 8TB, UK

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