Bug 1567988 - dac_read_search AVC from pam_systemd
Summary: dac_read_search AVC from pam_systemd
Keywords:
Status: CLOSED EOL
Alias: None
Product: Fedora
Classification: Fedora
Component: selinux-policy
Version: 27
Hardware: Unspecified
OS: Unspecified
unspecified
unspecified
Target Milestone: ---
Assignee: Lukas Vrabec
QA Contact: Fedora Extras Quality Assurance
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2018-04-16 14:12 UTC by Pierre Ossman
Modified: 2018-11-30 22:49 UTC (History)
4 users (show)

Fixed In Version:
Doc Type: If docs needed, set a value
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Clone Of:
Environment:
Last Closed: 2018-11-30 22:49:20 UTC
Type: Bug
Embargoed:


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Description Pierre Ossman 2018-04-16 14:12:33 UTC
We've very recently started seeing these AVCs on login with ThinLinc:

type=AVC msg=audit(1523887506.616:384): avc:  denied  { dac_read_search } for  pid=4290 comm="tl-session" capability=2  scontext=system_u:system_r:thinlinc_session_t:s0 tcontext=system_u:system_r:thinlinc_session_t:s0 tclass=capability permissive=0

After a lot of digging it turns out that the issue is accessing /run/user/<uid>/bus in order to start or verify the user d-bus. I'm not sure what PAM module is responsible for this, but I guess it is pam_systemd.

This seems similar to the issues with unix_chkpwd that happened recently:

https://bugzilla.redhat.com/show_bug.cgi?id=1451379
https://danwalsh.livejournal.com/77140.html

ThinLinc has the following policy:

type thinlinc_session_exec_t;
corecmd_executable_file(thinlinc_session_exec_t)
type thinlinc_session_t;
domain_type(thinlinc_session_t)
domain_entry_file(thinlinc_session_t, thinlinc_session_exec_t)
auth_login_pgm_domain(thinlinc_session_t)

auth_write_login_records(thinlinc_session_t)

userdom_spec_domtrans_all_users(thinlinc_session_t)
userdom_signal_all_users(thinlinc_session_t)

allow thinlinc_session_t self:capability { kill chown dac_override fowner setgid setuid sys_resource };
allow thinlinc_session_t self:process { getcap setsched setexec setrlimit };
allow thinlinc_session_t self:fifo_file rw_fifo_file_perms;

miscfiles_read_localization(thinlinc_session_t)

kernel_read_kernel_sysctls(thinlinc_session_t)

logging_append_all_logs(thinlinc_session_t)

mcs_process_set_categories(thinlinc_session_t)
mcs_killall(thinlinc_session_t)


I would have hoped that auth_login_pgm_domain() would have set everything up, but perhaps another macro needs to be added?

Comment 1 Pierre Ossman 2018-04-16 14:21:10 UTC
I guess I didn't read our own policy carefully enough. I see that we were already forced to explicitly mention dac_override. And I see that upstream has added dac_read_search explicitly to a bunch of domains, so I guess that is the correct solution here?

Comment 2 Ben Cotton 2018-11-27 14:25:23 UTC
This message is a reminder that Fedora 27 is nearing its end of life.
On 2018-Nov-30  Fedora will stop maintaining and issuing updates for
Fedora 27. It is Fedora's policy to close all bug reports from releases
that are no longer maintained. At that time this bug will be closed as
EOL if it remains open with a Fedora  'version' of '27'.

Package Maintainer: If you wish for this bug to remain open because you
plan to fix it in a currently maintained version, simply change the 'version' 
to a later Fedora version.

Thank you for reporting this issue and we are sorry that we were not 
able to fix it before Fedora 27 is end of life. If you would still like 
to see this bug fixed and are able to reproduce it against a later version 
of Fedora, you are encouraged  change the 'version' to a later Fedora 
version prior this bug is closed as described in the policy above.

Although we aim to fix as many bugs as possible during every release's 
lifetime, sometimes those efforts are overtaken by events. Often a 
more recent Fedora release includes newer upstream software that fixes 
bugs or makes them obsolete.

Comment 3 Ben Cotton 2018-11-30 22:49:20 UTC
Fedora 27 changed to end-of-life (EOL) status on 2018-11-30. Fedora 27 is
no longer maintained, which means that it will not receive any further
security or bug fix updates. As a result we are closing this bug.

If you can reproduce this bug against a currently maintained version of
Fedora please feel free to reopen this bug against that version. If you
are unable to reopen this bug, please file a new report against the
current release. If you experience problems, please add a comment to this
bug.

Thank you for reporting this bug and we are sorry it could not be fixed.


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