[Nfd-dev] LINK spec discussion

Sun Sep 14 15:32:08 PDT 2014

An alternative failure scenario which benefits from delegation is that the owner of /ndnsim misconfigured its link and put another ISP's name (maybe it used to be the provider) there or just forgot to remove the ISP's name when it switches to a new ISP.   If we require that ISP explicitly delegates its subprefix to link to /ndnsim, then Interests won't flood to the wrong ISP, which is undesirable for both the ISP and /ndnsim.

Lan

On Sep 12, 2014, at 11:53 PM, Junxiao Shi <shijunxiao at email.arizona.edu<mailto:shijunxiao at email.arizona.edu>> wrote:

Dear folks

In the non-routable web hosting scenario, to achieve the same level of security as IP DNS, we only need redirection and encapsulation LINKs.
/ndnsim doesn't need /att's permission to host the website under /att/alex-ndnsim. This is similar to IP DNS: to setup an A/AAAA record to that IP address, you don't need IP address owner's permission.

The procedure of accessing /ndnsim contents is:

  1.  perform a NDNS lookup for /ndnsim, which would return a redirection LINK
sign[ndnsim](name=/ndnsim, content="redirect=/att/alex-ndnsim")
  2.  replace /ndnsim with /att/alex-ndnsim in all Interests
     *   to access /ndnsim/index.html, express Interest /att/alex-ndnsim/index.html
  3.  some router near end host or the end host itself or the producer application, must replace /att/alex-ndnsim back to /ndnsim
     *   to execute signed Interest /ndnsim/action.cgi/[sig], Interest Name across the network is /att/alex-ndnsim/action.cgi/[sig], but the signature is generated based on /ndnsim/action.cgi
  4.  Data is encapsulated in encapsulation LINK
sha256(name=/att/alex-ndnsim/index.html/segment0, content={sign[ndnsim](name=/ndnsim, content="redirect=/att/alex-ndnsim") | sign[ndnsim](name=/ndnsim/index.html/segment0, content=payload)})

If the owner of /ndnsim points the NDNS record to some bogus location such as /verizon/alex-ndnsim, those Interests would be dropped after reaching /verizon due to lack of Route.

Adding delegation to the mix could prevent an attack in IP DNS.
In IP DNS, if the owner of a large website points his A record to a smaller website, the large amount of traffic would cause denial of service in the smaller website, although doing so would make the large website itself inaccessible. (This happened once on BAIDU, a top search engine in China; an attacker hijacked BAIDU's Nameserver and pointed A record to a small server).
If the owner of (large website) /ndnsim points the NDNS record to another user's namespace such as /verizon/john-victim (small website), it's the same attack as described above.
Storing the delegation record instead of redirection record in NDNS would prevent this attack.

A drawback of delegation record is: it promotes content control by ISP.
In IP DNS, user has the freedom to host any website on the IP address (unless ISP deploys layer-7 filtering).
If a delegation record is needed, ISP could refuse to sign a delegation record if they don't want user to host a certain website.

Yours, Junxiao

On Fri, Sep 12, 2014 at 4:40 PM, Alex Afanasyev <alexander.afanasyev at ucla.edu<mailto:alexander.afanasyev at ucla.edu>> wrote:
Hi!

I want continue our discussion about LINK specification (named-data.net/downloads/memos/link.pdf<http://named-data.net/downloads/memos/link.pdf>).

Currently we preliminary defined three elements:

a) link for redirection:

    signA("nameA", content: "nameB")

b) link for delegation

    signA("nameA", content: signB("nameB", content: "prefixOfNameA"))

c) "link" for encapsulation

    sha256("nameB" | "nameA", content: ("delegation or redirection link", data("nameA"))

The option (b) is the latest addition and I have some reservations about it.  In particular, what exactly this delegation achieves?  What security problem we are solving with it.

Let me give some example of (b).  I own a "non-routable" namespace /ndnsim and my site is connected to /att and /ucla networks.  So, the (b) option would require:

- I will have to obtain a "redirection" links from /att and /ucla to /ndnsim (option (a)) = get a permission from /att and /ucla to host /ndnsim site

- Then I will create a delegation packet(s) that I can put in NDNS to tell others that my site is currently available through /att and /ucla.

The process looks ok, but the question I have is what significance is in the first permission.  What is the point of me of requesting permission from my provider to host a website?  What I would gain and what provider itself would gain?

I personally, do not yet see a clear benefit from this process, only that it would complicate the delegation process.  Only me is able to tell others that my site is available at different places, so there is no question about others claiming that my site is available somewhere else.   If I mistakenly put a wrong link, then I myself will be at loss: i wouldn't be able to serve my content and somebody else would receive my interests and could reply to them with some junk.

If I "maliciously" put somebody else's network as a link, then interests for my data would go there.  But what is the harm?  If nobody replies to them, then routers can start ignoring/pushing back such interests.  If somebody replying, then somebody serves data and from the network point of view nothing bad is happening.

In short, I want us have a deep discussion on what exactly we are protecting and from whom.  For me, even with only one signature (option a), only the owner of the original namespace (/ndnsim) is able to create a legitimate link to somewhere else.   Additional signature could protect "provider" (destination of the link), but is it really a problem?  Anybody could send any number of interests to that provider even without any link (erroneous or malicious).

---
Alex

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