Hello, On Tuesday, September 12, 2023 5:20:54 PM EDT Amjad Gabbar wrote: > Based on this and some experiments I have been performing, I would suggest > changing how a lot of the FileSystem rules are written and illustrated. > Ex - > https://github.com/linux-audit/audit-userspace/blob/master/rules/30-pci-dss > -v31.rules#L34-L35 > > The rule in the repository is > -a always,exit -F path=/etc/sudoers -F perm=wa -F > key=10.2.2-priv-config-changes > > My suggestion is to instead change the rule based on the permissions > defined. The above rule would change to the following based on the kernel > being used. > -a always,exit -S <list of syscalls in audit_write.h and audit_read.h > +open,openat> -F path=/etc/sudoers -F perm=wa -F > key=10.2.2-priv-config-changes
That should be exactly what the kernel does with the perm fields. The perm fields select the right system calls that should be reported on. > This is higher performance because we are limiting the syscalls instead of > making use of -S all which has more paths of evaluation for each and every > syscall. > > Same thing for watches. Watches are inherently -S all rules which are very > performance intensive. > https://github.com/linux-audit/audit-userspace/blob/1482cec74f2d9472f81dd4f > 0533484bd0c26decd/lib/libaudit.c#L805 There should be no difference in performance between watches and syscall based file auditing. > Ideally we should limit the syscalls based on the permissions being used. > > I have implemented the same in my environment rules and have noticed a > massive performance difference with no difference in the events being > logged since we anyways filter eventually based on the permissions. > > Let me know what you all think. I'm looking into this more. I see a 1 line change that I am testing. -Steve > On Wed, Sep 6, 2023 at 2:58 PM Richard Guy Briggs <r...@redhat.com> wrote: > > On 2023-09-06 10:56, Amjad Gabbar wrote: > > > Hi, > > > > > > I have done some analysis and digging into how both the watch rules and > > > syscall rules are translated. > > > > > > From my understanding, in terms of logging, both the below rules are > > > similar. There is no difference in either of the rules. > > > > > > 1. -w /etc -p wa -k ETC_WATCH > > > > They are similar in this case. > > -w behaves differently depending on the existance of the watched entity > > and the presence of a trailing "/". This is why the form above is > > deprecated. > > > > > 2. -a always,exit -F arch=b64 -S <all syscalls part of the write and > > > attr > > > classes> -F dir=/etc -F perm=wa -k ETC_WATCH > > > > > > The write and attr classes consist of syscalls in > > > “include/asm-generic/audit_*.h“. > > > > > > The perm flag is needed in the second case for including open/openat > > > > > > syscalls which are not a part of the write and attr syscall list. > > > > > > I'd like to verify if what I mentioned earlier is accurate, and I have > > > an > > > additional point but depends on whether this is accurate. > > > > > > Ali > > > > - RGB > > > > -- > > Richard Guy Briggs <r...@redhat.com> > > Sr. S/W Engineer, Kernel Security, Base Operating Systems > > Remote, Ottawa, Red Hat Canada > > Upstream IRC: SunRaycer > > Voice: +1.613.860 2354 SMS: +1.613.518.6570 -- Linux-audit mailing list Linux-audit@redhat.com https://listman.redhat.com/mailman/listinfo/linux-audit