[VOIPSEC] VoIP vulnerabilities summarization

[Brian Ford]

Sukery,

While I agree with others on list that your analysis is interesting I 
think you are wrong referring to the list as "vulnerabilities".  A more 
accurate description would be potential threat vectors.  The term 
"vulnerability" should be used to define a very specific threat vector 
so that an exploit can be constructed.  Specifically:

#1 - Your point seems to be that the underlying IP network is insecure 
and because of that a vulnerability exists.  If we follow your logic 
then all applications are insecure.  The reality is that in 
communications between humans there is no such thing as a completely 
secure transaction. Where is the potential exploit?

#2 - SIP implementations do have call setup requirements.  You did a 
fine job of describing many of those requirements.  You stated that the 
potential exists for abuse if many call were attempted.  You have 
ignored the additional logic and dependencies that already exists in the 
call setup process.  Different implementations may not commit the same 
resources.  As such the DoS might not always work.  I think you were 
close here.

#3 - Again, you seem to be pointing a a DoS where the affects would vary 
between implementation.  Not as close as your #2.

#4 - An unencrypted data stream does not qualify as a vulnerability.  If 
you talk on the phone you can be overheard.  Doesn't that make all calls 
insecure?

#5 -Any program has a code flow. Saying that a program has the potential 
to be broken is not a vulnerability.

#6 - So any "attack" or really nuisance that exists on the PSTN can 
impact VoIP users.  True.  Vulnerability?  No.

Again, the thought that is expressed here is great.  I would suggest you 
need to drill down on specifics before throwing around the word 
"vulnerability".

Liberty for All,

Brian Ford
 

>Message: 4
>Date: Tue, 13 Dec 2005 18:37:1 +0800
>From: "sukery" <sukerry at 126.com>
>Subject: [VOIPSEC] VoIP vulnerabilities summarization
>To: Voipsec at voipsa.org <Voipsec at voipsa.org>
>Message-ID:
>	<mailman.18.1134475203.18425.voipsec_voipsa.org at voipsa.org>
>Content-Type: text/plain;      charset="GB2312"
>
>
>here is the summarization of voip vulnerabilities, and we are proud to say that we have realized an attack system to validate almost all the vulnerabilities, and I think point 2 and point 3 is  due to the imperfection of SIP protocol itself
>
>1.traditional IP network is insecure,its data stream is open to the public,VoIP, which is based on IP network certainly inherits this insecurity,this situation brings lots of attacks , such as Man in middle attak,call termination, sip password violent crack ,etc.
>
>2.SIP reuses  authentication mechanism from HTTP protocol ,in fact Http authentication is totally imperfect when applied to SIP protocol,for that it is a single-direction authentication, which means that only the server authenticates the endpoints,the endpoints do not authenticate the server,this situation makes it easy to deceive endpoints because they do not authenticate any entity in the network. Pseudo call (call someone with a false user id) ,server impersontation are dangerous attacks due to this vulnerability
>
>3. SIP communication is based on message transaction, however sip transaction mechanism is quite complicated.for example, when  a stateful proxy server receives a sip request message, it firstly computes the transaction ID for this message,if the transaction ID is not existed before, this request message is regarded as  a new message, the server will do a lot things for this new message:  save this message, create a finite statemachine for this message, construct a provisional response message and send it back, save this response message,update the finite statemachine, decide the next hop of this request message basing on the complex routing rules,transfer the request message, create one or more client transactions for the request message ...these steps surely consume lots of CPU and memory resources.  as a result,the server is susceptible to DoS Attacks when a hacker continually sends large quantities of SIP request messages with different Call-ID
>
>4.Un-encrypted media stream such as RTP data is easy to be wiretapped
>
>5.almost all VoIP software has some code flows, in this case,even a malicious packet may bring down the server, we call this packet exception packet, in fact we have found exception packets againtst both sip servers and h.323 servers 
>
>6.voip endpoints are much more intellectualized than traditional PSTN terminals,however,when this capability is abused,a lot of  malicious network attacks appear:
>     disturbance call
>	 call leaflet 
>     voice broadcast
>     and more??
>

-- 
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