Josh Bressers wrote:
We'd need to push repo verification data for both the latest and previous repo information. MirrorManager would have to be updated with new data as part of the updates/rawhide push so that it's always up to date with the mirror. We'll have to revise mirrormanager's caching model so that it always has access to the latest repository verification information.On 25 July 2008, Matt Domsch wrote:On Fri, Jul 25, 2008 at 01:52:26PM -0400, Josh Bressers wrote:That's a lot of IPs though. Can I request multiple /16s, or only one?As many as you like. And recall, such changes are made using your FAS credentials.Are these ever checked? Does say a mail get generated every time someone adds one of these? My fear would be that someone could blanket quite a large IP space without anyone noticing. Granted that would no doubt generate a huge volume of traffic, but if they're serving up a frozen repo, they probably won't be pushing all that much data.How many mirrors are doing this?374 total Hosts 185 have at least 1 netblock entry 94 of these are "private" - don't serve the publicwow, that's quite a few. I wasn't expecting numbers this high honestly.Does the mirror have to be part of the /16 to request it?no. Take for example Dell's mirrors. Netblock 143.166/16 is Dell US, but the mirror IPs are located inside the 10/8 private space.OK, so here is the problem the way I see it, signing the repository won't fix it. I'll try to explain this clearly, Justin can yell at me if I've gotten any of this wrong. So let's say Mallory (the bad guy) decides that he wants to host a malicious mirror and wait for a nasty security flaw. He sets up his mirror and even claims some IP subnets to serve. Bob and Alice are happily installing valid updates from him for some period of time. Since Mallory has claimed to serve a specific subnet, he has a rather impressive view of what Bob and Alice have installed. Now let's say there is a horrible security bug found in a mail server. Mallory knows for a fact that Bob and Alice both have it installed as he's been their mirror for a while. Mallory stops updating his mirror, so none of the users being served will get the mail server updates. Mallory also knows the IP address of the vulnerable clients and can easily break into their systems. So from what I understand MirrorManager will check on the mirrors to ensure they're not out of date. Mallory knows this and makes sure that when MirrorManager connects to his mirror, it lies and serves up current metadata. So here is the problem. The repodata was valid. The packages are signed. Even if we sign the repodata, this attack works. Being able to acquire an IP block simply makes this attack easier to do. It's still very possible that a bad mirror will wait for users to connect, serve up old content then use this knowledge to break into their system. What this problem boils down to, is we need a way for clients to ask MirrorManager what the current valid repo data is. Ideally we want the results to be signed in some manner so it can't be spoofed. Some thoughts I've had are: 1) Have MirrorManager use https and return some repo verification data.
This is going to have to have some policy attached to it. Do we continue to sign the repo data for EOL releases because people use them even though we tell people they're EOL?2) Sign the repo data, and if it's older than X, don't use it (I don't like this solution, but it's probably the easiest, just push out a new signed repo file once a day, even if nothing changes.)
This is the easiest to implement. It means the small repomd.xml file always comes from our server. But the rest of the metadata can come from the individual mirrors. However, it does mean that *very* large swaths of the mirrors will be unable to serve packages to users at any time because their metadata won't match with ours for some period after we have an update pushed. Maybe we could do this with versioned repodata and the client can decide how far back in time or how many past revisions it is willing to accept.3) Always get repo data from fedoraproject.org (probably not practical due to resource issues)
4) use DNS, have the client query <repodata sha1sum>.repo.fedoraproject.org if the lookup fails, the repo is invalid. (this is really cheap from a resource standpoint, but hard to do technically)
I don't know enough about implementing this one to comment.Also, all of these solutions need client-side support. That being the case, it should be generic enough that other repomd consuming clients and distributions will be willing to use it. Otherwise we'll be securing our updates and mirror infrastructure with the default package manager but doing nothing for the ecosystem as a whole.
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