Red Hat Bugzilla – Bug 576093
ssh changes security context of /var/tmp/host_0
Last modified: 2011-10-21 15:09:18 EDT
Description of problem: After login with sshd using Kerberos authentication the security context of /var/tmp/host_0 may be set sshd_t, causing other login daemons to deny access. Version-Release number of selected component (if applicable): openssh-5.3p1-19.fc12.x86_64 How reproducible: Steps to Reproduce: 1. Remove /var/tmp/host_0 2. Restart sshd 3. Login with ssh using Kerberos authentication (without entering password) 4. Replay cache created OK 5. Wait till all tickets in cache are expired (12-24hours) 6. Login with ssh using Kerberos authentication (without entering password) 7. Security context of /var/tmp/host_0 is set to sshd_t Actual results: Security context of /var/tmp/host_0 is set to sshd_t Expected results: Security context of /var/tmp/host_0 is set to krb5_host_rcache_t Additional info: I am forced to enable restorecond...
The problem is caused by function krb5_rc_dfl_expunge_locked (rcache/rc_dfl.c) from krb5-libs. This function recreated replay cache when there is too many expired entries in it. It make a temporary file using pattern /var/tmp/krb5_RCXXXXXX and then renames it into /var/tmp/host_0. Please, note that not only /var/tmp/host_0 is recreated using this pattern, but all other replay caches for other local principals. SE Linux Policy Version: 3.6.32-99.fc12 I am moving this bug to selinux-policy-targeted, but it might be required to patch kerberos libraries to fix this problem as currently there is no way to distinguish temporary files created for host rcache from others.
Created attachment 402285 [details] Patch to krb5-1.7
The attachment contains a fix to krb5 rcache subsystem using setfscreatecon to ensure correct replay cache file context. Please, move this bug to krb5 if there is no solution changing only policy is possible.
Created attachment 406761 [details] Replay cache to reproduce bug In order for bug to reproduce replay cache must contain more than 30 expired entries. Such file is attached. To reproduce: 1. Copy file to /var/tmp/host_0 2. restorecon /var/tmp/host_0 2. Login through ssh using kerberos auth 3. ls --lcontext /var/tmp/host_0
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I think I've seen this in RHEL6 too. Will try to return with a bug report for that.
I can confirm that this issue applies to RHEL 6.1, though I see it in slightly different forms: Given a /var/tmp/host_0 file with enough expired entries, - after a local login the context is set to local_login_tmp_t, - after an SSH login the context is set to user_tmp_t, and - on an active mail server running Dovecot, the context is set to dovecot_auth_tmp_t, but note that we're using a custom-compiled Dovecot and adjusted SELinux policy.
krb5-1.8.4-2.fc14 has been submitted as an update for Fedora 14. https://admin.fedoraproject.org/updates/krb5-1.8.4-2.fc14
Package krb5-1.8.4-2.fc14: * should fix your issue, * was pushed to the Fedora 14 testing repository, * should be available at your local mirror within two days. Update it with: # su -c 'yum update --enablerepo=updates-testing krb5-1.8.4-2.fc14' as soon as you are able to. Please go to the following url: https://admin.fedoraproject.org/updates/krb5-1.8.4-2.fc14 then log in and leave karma (feedback).
krb5-1.8.4-2.fc14 has been pushed to the Fedora 14 stable repository. If problems still persist, please make note of it in this bug report.
I also see this on RHEL6.1. Is there a bug for it? Steve.
(In reply to comment #11) > I also see this on RHEL6.1. > > Is there a bug for it? That's bug #714217, which should be fixed in the 6.2 beta.