Systemd Journald and audit logging causing journal issues

[Steve Grubb]

On Wednesday, October 18, 2017 12:32:15 PM EDT Brad Zynda wrote:
> On 10/18/2017 12:26 PM, Steve Grubb wrote:
> > On Wednesday, October 18, 2017 12:13:13 PM EDT Brad Zynda wrote:
> >> So now you have to comment out a rule at a time and watch for
> >> usage/count to fall?
> > 
> > Well, I am certain that commenting out that rule will drop the count. But
> > the question more is why is that rule being triggered. One thing you
> > could do is post the rule to the mail list if you think it might be
> > formed wrong. But you might also want to see whay its being triggered by
> > doing something like
> > 
> > ausearch --start today -k perm_mod --raw | aureport --summary --file -i
> > 
> > ausearch --start today -k perm_mod --raw | aureport --summary -x -i
> > 
> > ausearch --start today -k perm_mod --raw | aureport --summary --syscall -i
> > 
> >> Also if I wanted to grep and compare those numbers and alert with an
> >> email what would be the magic number to threshold with in a gt statement
> >> (500, 1000, etc.)?
> > 
> > That's a bit harder. You'd want a sliding window of time. Assuming your
> > cron job runs once an hour and a US locale, you'd do something like this:
> > 
> > aureport --start `date -d '1 hour ago' "+%m/%d/%Y %H:%M:%S"` --key
> > --summary --input-logs
> > 
> > I don't know what the best threshold would be because its workload
> > dependent. If you wanted to see things visualized, I'd try playing with
> > the data in R.
> > 
> > http://security-plus-data-science.blogspot.com/2017/03/bar-charts.html
> > http://security-plus-data-science.blogspot.com/2017/03/heatmaps.html
> > 
> > That assumes you have a recent audit package (2.7 or higher) and RStudio.
> > 
> > -Steve
> 
> Here are the rules:
> 
> grep perm_mod /etc/audit/audit.rules
> -a always,exit -F arch=b64 -S chmod -S fchmod -S fchmodat -F auid>=1000
> -F auid!=4294967295 -k perm_mod
> -a always,exit -F arch=b32 -S chmod -S fchmod -S fchmodat -F auid>=1000
> -F auid!=4294967295 -k perm_mod
> -a always,exit -F arch=b64 -S chown -S fchown -S fchownat -S lchown -F
> auid>=1000 -F auid!=4294967295 -k perm_mod
> -a always,exit -F arch=b32 -S chown -S fchown -S fchownat -S lchown -F
> auid>=1000 -F auid!=4294967295 -k perm_mod
> -a always,exit -F arch=b64 -S setxattr -S lsetxattr -S fsetxattr -S
> removexattr -S lremovexattr -S fremovexattr -F auid>=1000 -F
> auid!=4294967295 -k perm_mod
> -a always,exit -F arch=b32 -S setxattr -S lsetxattr -S fsetxattr -S
> removexattr -S lremovexattr -S fremovexattr -F auid>=1000 -F
> auid!=4294967295 -k perm_mod
> 
> grep delete /etc/audit/audit.rules
> -a always,exit -F arch=b64 -S unlink -S unlinkat -S rename -S renameat
> -F auid>=1000 -F auid!=4294967295 -k delete
> -a always,exit -F arch=b32 -S unlink -S unlinkat -S rename -S renameat
> -F auid>=1000 -F auid!=4294967295 -k delete
> -a always,exit -F arch=b64 -S init_module -S delete_module -k modules
> -a always,exit -F arch=b32 -S init_module -S delete_module -k modules

These rules are well formed. Meaning no obvious holes that would cause 
unintended events. The other ausearch/aureport commands I gave you should show 
you what is causing the events and to which files. This information may be 
used to create some kind of "never" rule that limits what gets audited. If you 
do create some exclusion rule, it needs to be above the perm_mod rules because 
audit is a "first match wins" system.

-Steve

-Steve