7.3.5. Searching For and Viewing Denials
This section assumes the
setroubleshoot,
setroubleshoot-server, and
audit packages are installed, and that the
auditd,
rsyslogd, and
setroubleshootd daemons are running. Refer to
Section 5.2, “Which Log File is Used” for information about starting these daemons. A number of tools are available for searching for and viewing SELinux denials, such as
ausearch,
aureport, and
sealert.
The audit package provides ausearch. From the
ausearch(8) manual page: "ausearch is a tool that can query the audit daemon logs based for events based on different search criteria"[]. The ausearch tool accesses /var/log/audit/audit.log, and as such, must be run as the Linux root user:
| Searching For |
Command |
| all denials |
/sbin/ausearch -m avc
|
| denials for that today |
/sbin/ausearch -m avc -ts today
|
| denials from the last 10 minutes |
/sbin/ausearch -m avc -ts recent
|
To search for SELinux denials for a particular service, use the -c
comm-name
option, where
comm-name
"is the executable’s name"[], for example, httpd for the Apache HTTP Server, and smbd for Samba:
/sbin/ausearch -m avc -c httpd
/sbin/ausearch -m avc -c smbd
Refer to the
ausearch(8) manual page for further ausearch options.
The audit package provides aureport. From the
aureport(8) manual page: "aureport is a tool that produces summary reports of the audit system logs"[]. The aureport tool accesses /var/log/audit/audit.log, and as such, must be run as the Linux root user. To view a list of SELinux denials and how often each one occurred, run the aureport -a command. The following is example output that includes two denials:
# /sbin/aureport -a
AVC Report
========================================================
# date time comm subj syscall class permission obj event
========================================================
1. 05/01/2009 21:41:39 httpd unconfined_u:system_r:httpd_t:s0 195 file getattr system_u:object_r:samba_share_t:s0 denied 2
2. 05/03/2009 22:00:25 vsftpd unconfined_u:system_r:ftpd_t:s0 5 file read unconfined_u:object_r:cifs_t:s0 denied 4
Refer to the
aureport(8) manual page for further aureport options.
The setroubleshoot-server package provides sealert, which reads denial messages translated by setroubleshoot-server. Denials are assigned IDs, as seen in /var/log/messages. The following is an example denial from messages:
setroubleshoot: SELinux is preventing httpd (httpd_t) "getattr" to /var/www/html/file1 (samba_share_t). For complete SELinux messages. run sealert -l 84e0b04d-d0ad-4347-8317-22e74f6cd020
In this example, the denial ID is 84e0b04d-d0ad-4347-8317-22e74f6cd020. The -l option takes an ID as an argument. Running the sealert -l 84e0b04d-d0ad-4347-8317-22e74f6cd020 command presents a detailed analysis of why SELinux denied access, and a possible solution for allowing access.
If you are running the X Window System, have the setroubleshoot and setroubleshoot-server packages installed, and the setroubleshootd and auditd daemons are running, a yellow star and a warning are displayed when access is denied by SELinux. Clicking on the star launches the sealert GUI, and displays denials in HTML output:
-
Run the sealert -b command to launch the sealert GUI.
-
Run the sealert -l \* command to view a detailed analysis of all denials.
-
As the Linux root user, run the sealert -a /var/log/audit/audit.log -H > audit.html command to create a HTML version of the sealert analysis, as seen with the sealert GUI.
Refer to the
sealert(8) manual page for further sealert options.
