Red Hat Bugzilla – Bug 222172
Expired ticket => supposed DOS attempt on ISP
Last modified: 2008-04-04 09:21:05 EDT
Description of problem: If I have a kerberos ticket that needs to be re-keyed but my machine can't see the kerberos server, my ISP claims that my machine "DOSs" their DNS servers with attempts to resolve the kerberos server. They told me it was happening something like 20 times a second. I got my internet access shutoff for a week :( It happened to me because I used my laptop at the office and did a kinit and then took it home and used it after the ticket expired. It even happens over reboots if one isn't running something like tmpfs due to the keys being cached in /tmp. Version-Release number of selected component (if applicable): 1.5-7 How reproducible: Always Steps to Reproduce: 1. kinit 2. disconnect from RH VPN (or ssh or whatever) 3. wait for > 24 h Actual results: Rogers (rogers.com) either warns you (first time) or kicks you off for a day or a week. Expected results: No supposed DOS attack. Additional info: Is there something we can educate Rogers on? Is this a bug in my krb5.conf?
Is there a krb5-auth-dialog process running, and is it crunching lots of CPU? This sounds like it would be a duplicate of bug #188301.
I believe krb5-auth-dialog was running but I'm unable/unwilling to try this again as I can't afford another week without access. I know that will make it hard to track this down and I'm sorry about that :( If there's anything else I can do, please let me know, Nalin. Thanks. Would it be krb5-auth-dialog doing the DNS attempts?
I would expect so, yes. The dialog goes into a tight loop trying to acquire credentials, and the first thing libkrb5 does each time it's called to do so is attempt to resolve the names of your configured KDCs. Can you point your resolv.conf at another system, even itself? If krb5-auth-dialog is pinning your CPU, you'll be able to verify that even if resolv.conf lists a machine which isn't a DNS server.
(In reply to comment #3) > Can you point your resolv.conf at another system, even itself? If > krb5-auth-dialog is pinning your CPU, you'll be able to verify that even if > resolv.conf lists a machine which isn't a DNS server. I will try this tonight or tomorrow and report back.
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Sorry for never reporting back on this. Let's close it.