when is dual ARCH required in audit.rules?

Steve Grubb sgrubb at redhat.com
Tue Oct 27 15:29:21 UTC 2015


On Tuesday, October 27, 2015 10:00:07 AM Robert Jacobson wrote:
> I've recently been trying to reconcile the audit.rules on my systems vs.
> the scap-security-guide, and I'm confused about the ARCH rules.

Right. I sent feedback internally to the project to tell them that what is 
written is not efficient and not clear. That section is being re-written.

> When is it required to check both 32- and 64-bit architectures?

Whenever you have a system that is bi-arch. That would commonly be 64 bit 
systems. But it is possible to compile 64 bit kernels that have no 32 bit ABI.


> e.g. the guide says both 32- and 64-bit rules are required to check for
> unauthorized access attempts:

That is a fact. The stig.rules shipped in the audit package is an accurate 
starting point for 64 bit systems needing stig compliance.

 
> # Unauthorized Access attempts (audit_rules_unsuccessful_file_modification)
> -a always,exit -F arch=b32 -S creat -S open -S openat -S
> open_by_handle_at -S truncate -S ftruncate -F exit=-EACCES -F auid>=500
> -F auid!=4294967295 -k access
> -a always,exit -F arch=b32 -S creat -S open -S openat -S
> open_by_handle_at -S truncate -S ftruncate -F exit=-EPERM -F auid>=500
> -F auid!=4294967295 -k access
> -a always,exit -F arch=b64 -S creat -S open -S openat -S
> open_by_handle_at -S truncate -S ftruncate -F exit=-EACCES -F auid>=500
> -F auid!=4294967295 -k access
> -a always,exit -F arch=b64 -S creat -S open -S openat -S
> open_by_handle_at -S truncate -S ftruncate -F exit=-EPERM -F auid>=500
> -F auid!=4294967295 -k access

This looks correct assuming that real users start at 500. That number needs 
adjusting up if you start users at a higher number.

> But for modifying the network environment, only the 64-bit rule is required:
> 
> # Network changes ( audit_rules_networkconfig_modification )
> -a always,exit -F arch=b64 -S sethostname -S setdomainname -k
> audit_rules_networkconfig_modification

A 32 bit rule is also needed.

> I don't understand why the 32-bit check is required for open() calls but
> not sethostname() calls?

Its a mistake. I am working with them to correct the SSG and it has problems 
beyond auditing. But its being patched quickly and should be ready to use 
soon.

-Steve


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