[SR-Users] Kamailio vulnerable to header smuggling possible due to bypass of remove_hf
jbrower at signalogic.com
jbrower at signalogic.com
Wed Sep 23 04:39:25 CEST 2020
Sandro-
I think your blog post on Kamailio security is well organized and well
written. Thanks for your effort and time to both document and cover
several perspectives.
What I have seen in formalized open source -- e.g. groups run by Linux
Foundation -- is the community will form a security subcommittee,
which has some measure of independence. Typically a "Technical
Steering Committee" or similar, with elected members, will vet
proposals and settle on one, and then authorize the security
subcommittee to implement. Proposals typically include reporting
methods, rules and timeframes on publishing / updating advisories, and
keeping things up organized and up to date on a centralized website.
There may also be security review and sign-off on mods or bug fixes in
certain code areas. Something like Atlassian confluence, with Wiki
pages that can be updated at any time by both developers and users is
typical (it looks like the Kamailio wiki could be used). From what
I've seen, in larger, formalized open sources the general idea is to
be open and transparent about anything related to security --
proactive rather than reactive. It's reasonable to say that's because
sub groups working in one part of the community don't want to be
caught off guard by surprise vulnerabilities caused by another sub
group. They want to trust the larger community is looking out for them.
I'm not saying Kamailio needs to be, or should be, this formalized --
some of the LF groups are hundreds of membes wiwth dozens of active
projects -- but the "independent subcommittee" (or semi-independent)
concept might be something to consider.
-Jeff
Quoting Sandro Gauci <sandro at enablesecurity.com>:
> I know I am waking up an old debate by replying to this thread.
> Deeply sorry :-)
>
> Finally got around to writing up a blog post about this very
> thread where I (think) I spared absolutely no one, not even myself.
>
> My post is called "The great Kamailio security debate and some
> misconceptions debunked" and can be read here:
>
>
> https://www.rtcsec.com/2020/09/02-kamailio-security-debate-and-misconceptions/
>
> The ToC:
>
>
> * Introduction
> * A bit of background before diving in
> * Claim: this issue does not affect many organisations
> * Claim: custom headers are only known to internal users
> * Claim: if it’s an 18 year old bug, it can’t have been high risk
> * Claim: this should have been found if people were doing proper testing
> * Claim: infrequent advisories = project is not serious about security
> * Claim: limited number of advisories = project is more secure
> * Claim: if you’re serious about security, monitor the mailing lists
> * Claim: security experts should decide what is a security vulnerability
> * Discussion: when should the project publish an advisory?
> * Discussion: educational security role
> * Moving forward
> Hope that it is at least interesting and perhaps even constructive!
>
> Best wishes,
>
> --
>
> Sandro Gauci, CEO at Enable Security GmbH
>
> Register of Companies: AG Charlottenburg HRB 173016 B
> Company HQ: Pappelallee 78/79, 10437
> Berlin, Germany
> PGP/Encrypted comms: https://keybase.io/sandrogauci
> Our blog: https://www.rtcsec.com
> Other points of contact: https://enablesecurity.com/#contact-us
>
>
>
>
> On Thu, 3 Sep 2020, at 10:34 AM, Olle E. Johansson wrote:
>
>> Well, you have defined one definitive line between being stupid and
>> following some current practise :-)
>>
>> I like to think we as a project have an educational role as
>> well. In this case explaining the bug we had and what it can cause.
>> We should definitely add a warning along the lines you write too
>> - relying on headers alone is bad and not best current practise.
>>
>> /O
>>
>>
>>> On 3 Sep 2020, at 10:14, davy van de moere
>>> <davy.van.de.moere at gmail.com> wrote:
>>>
>>> After 20 years in voip, my 2 cents on this,
>>> if you succeed in creating a voip system where the security of the
>>> whole relies on the ability to remove (or only keep specific)
>>> custom sip headers, you will wake up one morning realizing a bunch
>>> of people in Palestine made a gazillion calls over your system to
>>> expensive destinations, bringing you to or over the edge of
>>> bankruptcy.
>>>
>>> Security should be multilayered, one header sneaking
>>> through should not give any big problems.
>>>
>>> From a security point of view, this could be
>>> called a 'normal' security risk, I think. It's a bit more than low
>>> as you can do more than just get some info, but it's not high, as
>>> you would need to have many other factors going wrong to get to a
>>> successful exploit.
>>>
>>>
>>>
>>>
>>>
>>> Op do 3 sep. 2020 om 09:18 schreef Olle E.
>>> Johansson <oej at edvina.net>:
>>>
>>>> One thought - we may have to separate security vulnerability
>>>> reporting from security advisory documents. I think in some
>>>> cases, where a common use of a product can lead to issues (but it
>>>> is not clearly a bug that cause crashes in our code) we may have
>>>> to send out an advisory and publish it in the same way. The
>>>> problem with that is where the border is between just doing
>>>> stupid things like taking SQL statements from SIP headers and
>>>> issues like this that are harder to catch.
>>>>
>>>> We had a long and hard discussion about this in the
>>>> Asterisk project many years ago - a very common dialplan
>>>> construct (that was documented in many places) was indeed very
>>>> dangerous. It wasn’t any code in asterisk that caused the issue,
>>>> just a common dialplan construct that existed in many, many
>>>> production systems. In the end, if I remember correctly, the
>>>> project issued an advisory and added a README about it.
>>>>
>>>> Maybe that’s a way forward.
>>>>
>>>> /O
>>>>
>>>>
>>>>> On 2 Sep 2020, at 21:25, Henning Westerholt <hw at skalatan.de> wrote:
>>>>>
>>>>> Hello Maxim,
>>>>> ___ ___
>>>>> ___have a look to the first sentence:___
>>>>> ____ ____
>>>>> ___“A security vulnerability is (for example)
>>>>> when a user of Kamailio can cause Kamailio to crash or lock up
>>>>> by sending messages to the server process.”___
>>>>> ____ ____
>>>>> ___So there is some limitation regarding
>>>>> vulnerability criticality defined in there. But of course (as I
>>>>> already mentioned), it might be improved to e.g. use CVSS
>>>>> scoring instead.___
>>>>> ____ ____
>>>>> ___Cheers,___
>>>>> ____ ____
>>>>> ___Henning___
>>>>> ____ ____
>>>>> ___FROM: Maxim Sobolev
>>>>> <sobomax at sippysoft.com>
>>>>> SENT: Wednesday, September 2, 2020 9:15 PM
>>>>> TO: Henning Westerholt <hw at skalatan.de>
>>>>> CC: Daniel-Constantin Mierla
>>>>> <miconda at gmail.com>; yufei.tao at gmail.com; Olle E. Johansson
>>>>> <oej at edvina.net>; Gerry | Rigatta <gjacobsen at rigatta.com>;
>>>>> Kamailio (SER) - Users Mailing List
>>>>> <sr-users at lists.kamailio.org>; jbrower at signalogic.com
>>>>> SUBJECT: Re: [SR-Users] Kamailio vulnerable to header smuggling
>>>>> possible due to bypass of remove_hf___
>>>>>
>>>>> ____ ____
>>>>> ___On Wed, Sep
>>>>> 2, 2020 at 11:30 AM Henning Westerholt <hw at skalatan.de> wrote:___
>>>>>
>>>>>
>>>>>> ___Hello Maxim,___
>>>>>> ___ ___
>>>>>> ___thank you for the clarification, appreciated.___
>>>>>
>>>>> ____ ____
>>>>>
>>>>> ___No worries, hope to have a
>>>>> civilized discussion.___
>>>>>
>>>>> ___ ___
>>>>>
>>>>>> ___Just one clarification, my comment regarding the advisory
>>>>>> from 2018 was not meant as advertisement etc..___
>>>>>
>>>>> ____ ____
>>>>>
>>>>> ___Point taken, I dramatized
>>>>> of course to underline my point. ___
>>>>>
>>>>> ____ ____
>>>>>
>>>>>> ___One suggestion to objectify the whole discussion, there
>>>>>> exists a well-known and accepted metric for vulnerabilities:
>>>>>> CVSS [1]___
>>>>>> ___If I calculate the CVSS score for this
>>>>>> issue, it results in a medium level with score 5.8. But this is
>>>>>> of course again (at least somewhat) influenced from my point of
>>>>>> view to this bug.___
>>>>>> ___ ___
>>>>>> ___Some projects have a policy to only do a
>>>>>> security announcement for vulnerabilities with score high and
>>>>>> critical. For Kamailio this is not yet defined in a detailed
>>>>>> way, due to the size of the project and other factors.___
>>>>>> ___ ___
>>>>>> ___So, If people in this discussion (or
>>>>>> other people on the list) are interested in improving the
>>>>>> project security processes – this wiki page with the current
>>>>>> process might be a good starting
>>>>>> point:https://www.kamailio.org/wiki/security/policy___
>>>>>> ___ ___
>>>>>> ___Please suggest your improvements to the
>>>>>> existing process (preferable in a new discussion thread) on the
>>>>>> sr-dev list. If you want to do it in private, feel free contact
>>>>>> the management list.___
>>>>>
>>>>> ____ ____
>>>>>
>>>>> ___Well, first suggestion
>>>>> after having read it: to start actually following what's
>>>>> documented before any improvements are made. ;-) The policy says
>>>>> plain and simple (quote):___
>>>>>
>>>>> ____ ____
>>>>>
>>>>>> ___Publishing Security Vulnerabilities___
>>>>>
>>>>>> ___Kamailio will publish security vulnerabilities, including an
>>>>>> CVE ID, on the kamailio-business mailing list, sr-dev, sr-users
>>>>>> as well as related lists. The advisories will also be published
>>>>>> on the kamailio.org[1] web site. ___
>>>>>>
>>>>>> ___ ___
>>>>>>
>>>>>> ___CVE
>>>>>> entries should be created for vulnerabilities in the core and
>>>>>> major modules, for rarely used modules this is not necessary.
>>>>>> If there are several security issues together in one release,
>>>>>> they should be announced together. ___
>>>>>
>>>>> ___ ___
>>>>>
>>>>> ___I might be missing
>>>>> something obvious, but there is no "if" or "maybe" or "it
>>>>> depends". Any module that has been 18 years with the project
>>>>> qualifies to be a "major module" to me... ___
>>>>>
>>>>> ____ ____
>>>>>
>>>>> ___-Max___
>>>>
>>>>
>>>>
>>>> _____________________________________________________
>>>> ___Kamailio (SER) - Users Mailing List___
>>>> ___sr-users at lists.kamailio.org___
>>>>
>>>> ___https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users___
>>>
>>> _____________________________________________________
>>> ___Kamailio (SER) - Users Mailing List___
>>> ___sr-users at lists.kamailio.org___
>>> ___https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users___
>>
>> _____________________________________________________
>> ___Kamailio (SER) - Users Mailing List___
>> ___sr-users at lists.kamailio.org___
>> ___https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users___
>>
>
>
Links:
------
[1] http://kamailio.org/
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