KDC/kadmind may fail to start on IPv4-only systems
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
krb5 (Debian) |
Fix Released
|
Unknown
|
|||
krb5 (Ubuntu) |
Fix Released
|
High
|
Unassigned | ||
Zesty |
Fix Released
|
High
|
Andreas Hasenack |
Bug Description
This is fixed in artful in krb5 1.15-2
- upstream: http://
- debian: conflated into https:/
- debian patch: 0011-Fix-
[Impact]
getaddrinfo() called on a wildcard address might return the IPv6 "::1" address. On machines without IPv6 support, binding to it will most likely fail and the kdc/kadmin services won't start.
The provided patch is applied upstream and in Debian testing.
[Test Case]
Steps to reproduce the problem on zesty:
a) install krb5-kdc krb5-admin-server
$ sudo apt install krb5-kdc krb5-admin-server
when prompted, use EXAMPLE.ORG (all caps) as the default realm
when prompted, use the IP of this machine for the KDC and the Admin servers
b) configure a new realm called EXAMPLE.ORG
$ sudo krb5_newrealm
use any password of your liking when prompted
c) confirm the kdc and admin services are running.
$ ps faxw|grep -E "(krb5kdc|
4275 ? Ss 0:00 /usr/sbin/krb5kdc -P /var/run/
4306 ? Ss 0:00 /usr/sbin/kadmind -nofork
d) create a principal and obtain a ticket to confirm kerberos is working properly:
$ sudo kadmin.local addprinc -pw ubuntu +requires_preauth ubuntu
$ kinit
Password for <email address hidden>:
$ klist
Ticket cache: FILE:/tmp/
Default principal: <email address hidden>
Valid starting Expires Service principal
05/04/2017 14:20:17 05/05/2017 00:20:17 <email address hidden>
renew until 05/05/2017 14:20:13
e) Confirm the kerberos services are bound to IPv6 local sockets:
$ sudo netstat -anp|grep -E "^(tcp|
tcp6 0 0 :::88 :::* LISTEN 1078/krb5kdc
tcp6 0 0 :::749 :::* LISTEN 1065/kadmind
tcp6 0 0 :::464 :::* LISTEN 1065/kadmind
udp6 0 0 :::88 :::* 1078/krb5kdc
udp6 0 0 :::464 :::* 1065/kadmind
udp6 0 0 :::750 :::* 1078/krb5kdc
f) configure the system to not support IPv6. There are probably many ways to do this, but the one sure way is to reboot it with ipv6.disable=1 in the kernel command line:
e.1) edit /etc/default/grub
e.2) add "ipv6.disable=1" to GRUB_CMDLINE_LINUX and save
e.3) run sudo update-grub
e.4) reboot
f) Confirm the kdc and admin services are NOT running:
$ ps faxw|grep -E "(krb5kdc|
$
g) /var/log/auth.log will contain the reason:
$ sudo grep -E "(kadmind|
May 4 14:11:54 22-96 krb5kdc[1087]: Failed setting up a UDP socket (for ::.750)
May 4 14:11:54 22-96 kadmind[1085]: Failed setting up a UDP socket (for ::.464)
May 4 14:15:36 22-96 krb5kdc[1510]: Failed setting up a UDP socket (for ::.750)
May 4 14:16:36 22-96 krb5kdc[1652]: Failed setting up a UDP socket (for ::.750)
May 4 14:25:54 22-96 kadmind[1085]: Failed setting up a UDP socket (for ::.464)
May 4 14:25:54 22-96 krb5kdc[1079]: Failed setting up a UDP socket (for ::.750)
With the updated packages, krb5-kdc and krb5-admin-server will startup just fine in the same conditions.
[Regression Potential]
We now tolerate a EAFNOSUPPORT error as long as at least one socket was bound to correctly. Maybe there could be a scenario when this one bound socket is useless, or unexpected: in that case, bailing out because of the EAFNOSUPPORT error could be seen as a more robust approach because it's immediately visible, instead of silently listening on the useless socket.
That being said, I believe single stack systems (only IPv4, or only IPv6) take an extra configuration effort and most systems are dual stack. Zesty certainly is, out of the box.
Changed in krb5 (Ubuntu): | |
assignee: | Andreas Hasenack (ahasenack) → nobody |
status: | In Progress → Fix Released |
Changed in krb5 (Ubuntu Zesty): | |
status: | New → In Progress |
assignee: | nobody → Andreas Hasenack (ahasenack) |
Changed in krb5 (Debian): | |
status: | Unknown → Fix Released |
description: | updated |
description: | updated |
Changed in krb5 (Ubuntu): | |
importance: | Undecided → High |
Changed in krb5 (Ubuntu Zesty): | |
importance: | Undecided → High |
tags: | added: verification-done |
Hello Andreas, or anyone else affected,
Accepted krb5 into zesty-proposed. The package will build now and be available at https:/ /launchpad. net/ubuntu/ +source/ krb5/1. 15-1ubuntu0. 1 in a few hours, and then in the -proposed repository.
Please help us by testing this new package. See https:/ /wiki.ubuntu. com/Testing/ EnableProposed for documentation on how to enable and use -proposed.Your feedback will aid us getting this update out to other Ubuntu users.
If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, and change the tag from verification-needed to verification-done. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification- failed. In either case, details of your testing will help us make a better decision.
Further information regarding the verification process can be found at https:/ /wiki.ubuntu. com/QATeam/ PerformingSRUVe rification . Thank you in advance!