** Description changed: [Impact] When using syncrepl replication with openldap, the consumer needs to authenticate to the provider in order to perform the searches and fetch the data. When this authentication is a simple bind, a simple username/password pair is used and that can be easily supplied in a configuration file. When one wants to use a stronger authentication mechanism, like gssapi (kerberos), the authentication is based on keytab files and tickets. The consumer needs to obtain a ticket from the KDC, and use that ticket to authenticate itself with the provider. For users, it's a simple matter of running kinit(1) and providing a password. For services, the solution is to extract the key from the KDC and store it in a local keytab file, which is then used by the service to obtain the TGT. Problem is this TGT expires, and needs to be renewed periodically. Solutions have popped up for that issue, the most famous one being kstart (https://www.eyrie.org/~eagle/software/kstart/), but since the MIT kerberos 1.11 release, there is a simpler way. Via the default_client_keytab_name krb5.conf(5) option, one can specify the default location of a keytab file per local user. The kerberos library will then automatically use that file to obtain the TGT, and proceed as usual from there. The default value of that setting is /etc/krb5/user/<uid>/client.keytab. Turns out the openldap slapd apparmor profile doesn't account for that, and blocks attempts to read that file. It also blocks reading the TGT that is obtained and stored in /tmp/krb5cc_<uid>, resulting in such DENIED errors in the logs: apparmor="DENIED" operation="open" profile="/usr/sbin/slapd" name="/etc/krb5/user/389/client.keytab" pid=19080 comm="slapd" requested_mask="r" denied_mask="r" fsuid=389 ouid=389 apparmor="DENIED" operation="file_lock" profile="/usr/sbin/slapd" name="/tmp/krb5cc_389" pid=19080 comm="slapd" requested_mask="k" denied_mask="k" fsuid=389 ouid=389 Since the slapd apparmor is enabled by default, this blocks the usage of this very helpful feature. Also considering that kerberos/gssapi errors are usually hard to debug, it might take a while for an admin to figure out what is going on. The fix is to update the apparmor profile and allow access to those files. Unfortunately there are no rich globbing rules for paths in an apparmor profile, nothing like @{uid} of the current process yet, or a regexp rule like [0-9]+, so the rules have to be a bit accomodating. For this bug, I came up with these two new lines: - /etc/krb5/user/*/client.keytab kr, - owner /tmp/krb5cc_* rwk, + /etc/krb5/user/*/client.keytab kr, + owner /tmp/krb5cc_* rwk, One could relax the first one perhaps into something like /etc/krb5/**, but the above works with the default settings. + [Test Case] + Setting up openldap replication via gssapi can be complicated, so I wrote some scripts to help. + - setup-kdc.sh: sets up the KDC server + - setup-provider.sh: sets up the openldap provider + - setup-consumer.sh: sets up the openldap consumer - [Test Case] + The scripts expect LXD containers to be used, that have a working DNS + setup for a ".lxd" domain. In other words, if you do: - * detailed instructions how to reproduce the bug + lxc launch ubuntu-daily:bionic bionic-provider - * these should allow someone who is not familiar with the affected - package to reproduce the bug and verify that the updated package fixes - the problem. + The script expects the container to be reachable via "bionic- + provider.lxd". That is the default behavior of LXD, and changing the + scripts to work in a more generic case was deemed not worth it. + + So here we go. Here are the steps for a cosmic test, just replace + "cosmic" with the name of the ubuntu release you are testing. + + = KDC = + + * launch the KDC container and copy the setup-kdc.sh script into it: + lxc launch ubuntu-daily:cosmic cosmic-kdc + lxc file push ./setup-kdc.sh cosmic-kdc/root/ + + * Enter the container and run the setup-kdc.sh script: + lxc exec cosmic-kdc bash + bash ./setup-kdc.sh + + * The script will show two prompts: one from debconf, with just an "ok" + option, so hit ENTER there. The second prompt will be for a password. + Use any one you like, it won't be needed again. + + * The KDC is setup, you can exit the container. + + = PROVIDER = + * launch the provider and copy the setup-provider.sh script into it: + lxc launch ubuntu-daily:cosmic cosmic-provider + lxc file push ./setup-provider.sh cosmic-provider/root/ + + * Enter the container and run the setup-provider.sh script: + lxc exec cosmic-provider bash + bash ./setup-provider.sh + + * Leave a tail on the slapd logs, we will come back to this later: + tail -f /var/log/syslog|grep slapd + + + = CONSUMER = + * launch the consumer and copy the setup-consumer.sh script into it: + lxc launch ubuntu-daily:cosmic cosmic-consumer + lxc file push ./setup-consumer.sh cosmic-consumer/root/ + + * Enter the container and run the setup-consumer.sh script: + lxc exec cosmic-consumer bash + bash ./setup-consumer.sh + + * On the provider's log tail, you should soon see a connection and immediate disconnection like this: + Oct 23 17:37:18 cosmic-provider slapd[2396]: conn=1004 fd=12 ACCEPT from IP=10.0.100.93:35276 (IP=0.0.0.0:389) + Oct 23 17:37:18 cosmic-provider slapd[2396]: conn=1004 op=0 UNBIND + Oct 23 17:37:18 cosmic-provider slapd[2396]: conn=1004 fd=12 closed + + * On this consumer log, you should see an error like this: + tail /var/log/syslog |grep slapd + ... + Oct 23 17:37:18 cosmic-consumer slapd[2408]: do_syncrepl: rid=001 rc -1 retrying + + * On the host's log, dmesg will show an apparmor DENIED message like this: + [104159.081883] audit: type=1400 audit(1540316238.330:1881): apparmor="DENIED" operation="open" namespace="root//lxd-cosmic-consumer_<var-lib-lxd>" profile="/usr/sbin/slapd" name="/etc/krb5/user/110/client.keytab" pid=22385 comm="slapd" requested_mask="r" denied_mask="r" fsuid=165646 ouid=165536 + + This confirms the bug. + + The replication request from the consumer to the provider will be + repeated every 60s, so these messages will continue until the fixed + package is installed. + + To verify the fix, install the updated openldap packages on the consumer. Right after, the provider should log what is now a successful replication: + Oct 23 17:41:34 cosmic-provider slapd[2396]: conn=1009 fd=12 ACCEPT from IP=10.0.100.93:35332 (IP=0.0.0.0:389) + Oct 23 17:41:34 cosmic-provider slapd[2396]: conn=1009 op=0 BIND dn="" method=163 + Oct 23 17:41:39 cosmic-provider slapd[2396]: conn=1009 op=0 RESULT tag=97 err=14 text=SASL(0): successful result: + Oct 23 17:41:39 cosmic-provider slapd[2396]: conn=1009 op=1 BIND dn="" method=163 + Oct 23 17:41:39 cosmic-provider slapd[2396]: conn=1009 op=1 RESULT tag=97 err=14 text=SASL(0): successful result: + Oct 23 17:41:39 cosmic-provider slapd[2396]: conn=1009 op=2 BIND dn="" method=163 + Oct 23 17:41:39 cosmic-provider slapd[2396]: conn=1009 op=2 BIND authcid="consumer" authzid="consumer" + Oct 23 17:41:39 cosmic-provider slapd[2396]: conn=1009 op=2 BIND dn="uid=consumer,cn=gssapi,cn=auth" mech=GSSAPI sasl_ssf=56 ssf=56 + Oct 23 17:41:39 cosmic-provider slapd[2396]: conn=1009 op=2 RESULT tag=97 err=0 text= + Oct 23 17:41:39 cosmic-provider slapd[2396]: conn=1009 op=3 SRCH base="dc=lxd" scope=2 deref=0 filter="(objectClass=*)" + Oct 23 17:41:39 cosmic-provider slapd[2396]: conn=1009 op=3 SRCH attr=* + + + The consumer should also have a TGT file in /tmp, with the uid number of + the slapd process: + + root@cosmic-consumer:~# ll /tmp/krb5cc* + -rw------- 1 openldap openldap 1903 Oct 23 17:41 /tmp/krb5cc_110 + root@cosmic-consumer:~# id -u openldap + 110 + [Regression Potential] * discussion of how regressions are most likely to manifest as a result of this change. * It is assumed that any SRU candidate patch is well-tested before upload and has a low overall risk of regression, but it's important to make the effort to think about what ''could'' happen in the event of a regression. * This both shows the SRU team that the risks have been considered, and provides guidance to testers in regression-testing the SRU. [Other Info] * Anything else you think is useful to include * Anticipate questions from users, SRU, +1 maintenance, security teams and the Technical Board * and address these questions in advance [Original Description] Can we get /etc/krb5/** and /tmp/krb5cc_* added with the appropriate permissions to the slapd apparmor profile? I'm getting the following kinds of errors: apparmor="DENIED" operation="open" profile="/usr/sbin/slapd" name="/etc/krb5/user/389/client.keytab" pid=19080 comm="slapd" requested_mask="r" denied_mask="r" fsuid=389 ouid=389 apparmor="DENIED" operation="file_lock" profile="/usr/sbin/slapd" name="/tmp/krb5cc_389" pid=19080 comm="slapd" requested_mask="k" denied_mask="k" fsuid=389 ouid=389
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1783183 Title: apparmor profile denied for kerberos client keytab and credential cache files To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/openldap/+bug/1783183/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
