Re: Sycall Rules vs Watch Rules

From: Amjad Gabbar <amjadgabbar11@gmail.com>
To: Steve Grubb <sgrubb@redhat.com>
Cc: Richard Guy Briggs <rgb@redhat.com>, linux-audit@redhat.com
Subject: Re: Sycall Rules vs Watch Rules
Date: Fri, 29 Sep 2023 11:39:51 -0500	[thread overview]
Message-ID: <CAJcJf=Ss2Fz3932cE+Fxf4rGMUrbNOPEZ1i3xAQmz_x+XbVbGg@mail.gmail.com> (raw)
In-Reply-To: <3262512.44csPzL39Z@x2>

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Sounds good. I will test this out.

Regards
Ali Adnan

On Thu, Sep 28, 2023 at 11:30 AM Steve Grubb <sgrubb@redhat.com> wrote:

> On Thursday, September 28, 2023 11:53:26 AM EDT Steve Grubb wrote:
> > On Thursday, September 21, 2023 4:02:49 PM EDT Amjad Gabbar wrote:
> > > > The best solution would be a kernel modification so that there are no
> > > > mismatched lists.
> > >
> > > I agree as well....This would be the cleanest solution. This would also
> > > solve the userspace problem of maintaining different lists which can
> get
> > > out of hand fairly quickly.
> >
> > After looking into this, a kernel patch would also not work well. It has
> to
> > be arch specific
> >
> > > > I guess we can warn on that to rewrite in syscall notation.
> > >
> > > We certainly should. I think the user should know that there is a
> > > performance cost associated with watches and we should explicitly
> mention
> > > how it can be optimized in the manpages also. The reason being I am
> > > pretty sure, numerous users/repos still do make use of the -w notation
> > > and we do want to let them know the issue here. We also need to make
> > > quite a few changes to the manpages also regarding this. Because,
> > > initially even I was  very confused when reading the man pages and
> seeing
> > > the actual implementation of and results were not quite in sync.
> >
> > I have made the changes to the master and audit-3.1-maint branches.
> Please
> > everyone concerned give them tests. The short of it is that if you use
> the
> > '- w' notation for watches, it will remain the same and slower.
>
> Actually, ths is the one that draws the warning to urge people to migrate.
>
> > If you use
> > the syscall notation without "-F arch", you will get a warning that it
> > cannot be optimized without adding "-Farch".
>
> Actually, you won't in order to preserve intentional behavior.
>
> > If you add "-F arch", you
> > will possibly need one for both arches which means doubling the rules. If
> > you do not want to double the rules, you might place a syscall rule for
> > any 32 system call (21-no32bit.rules). Or you can leave it as is and not
> > care. The sample rules and all man pages have been updated.
>
> I should have provided an example of what this means. If you have this kind
> of rule:
>
> -w /etc/shadow -p wa -k shadow
>
> And when applied draws a warning:
>
> # auditctl -w /etc/shadow -p wa -k shadow
> Old style watch rules are slower
>
> It should be rewritten as
>
> -a always,exit -F arch=b64 -F path=/etc/shadow -F perm=wa -F key=shadow
>
> Then it looks like this when loaded:
>
> #auditctl -l
> -a always,exit -F arch=b64 -S
> open,bind,truncate,ftruncate,rename,mkdir,rmdir,creat,link,unlink,symlink,chmod,fchmod,chown,fchown,lchown,mknod,acct,swapon,quotactl,setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr,openat,mkdirat,mknodat,fchownat,unlinkat,renameat,linkat,symlinkat,fchmodat,fallocate,renameat2,openat2
> -F path=/etc/shadow -F perm=wa -F key=shadow
>
> And to delete  the rule,
> auditctl -d always,exit -F arch=b64 -F path=/etc/shadow -F perm=wa -F
> key=shadow
>
> or the long way
>
> auditctl -d always,exit -F arch=b64 -S
> open,bind,truncate,ftruncate,rename,mkdir,rmdir,creat,link,unlink,symlink,chmod,fchmod,chown,fchown,lchown,mknod,acct,swapon,quotactl,setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr,openat,mkdirat,mknodat,fchownat,unlinkat,renameat,linkat,symlinkat,fchmodat,fallocate,renameat2,openat2
> -F path=/etc/shadow -F perm=wa -F key=shadow
>
> Hopefully this is clearer what the change is.
>
> -Steve
>
>
>
>

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