Unique audit record type ranges for individual LSMs

[Tyler Hicks]

Hello - The AppArmor project would like for AppArmor audit records to be
supported by the audit-userspace tools, such as ausearch, but it
requires some coordination between the linux-security-module and
linux-audit lists. This was raised as a feature request years ago in
Ubuntu and more recently in Debian:

  https://launchpad.net/bugs/1117804
  https://bugs.debian.org/872726

The quick summary of the problem at hand is that the audit-userspace
project requires that each LSM use a unique record type range for audit
records while the kernel's common_lsm_audit() function uses the same
record type (1400) for all records. SELinux, AppArmor, and SMACK are all
using common_lsm_audit() today and, therefore, the 1400-1499 range.

While it will be potentially painful to switch, the AppArmor project is
considering to use a unique range in order for audit-userspace to
support AppArmor audit records. IMHO, SMACK would be free to continue
using 1400-1499 as long as they don't need audit-userspace support and
SELinux would continue using 1400-1499.

Steve Grubb previously told me that he intends 1500-1599 to be used by
AppArmor:

  https://www.redhat.com/archives/linux-audit/2014-May/msg00119.html


John Johansen tells me that AppArmor previously used the 1500-1599 range
before AppArmor was upstreamed.

There's a conflicting comment in the kernel stating that 1500-1599 is to
by used by kernel LSPP events. As far as I can tell, there were never
any kernel LSPP events that used the range. Steve is the one that added
that comment so I think it is a safe range for AppArmor to use:

  https://git.kernel.org/linus/90d526c074ae5db484388da56c399acf892b6c17

Considering audit-userspace's stance, does the LSM community agree that
common_lsm_audit() should be modified to accept an audit record type
parameter to pass on to audit_log_start()?

If so, does everyone agree that 1500-1599 would be acceptable for
AppArmor to use?

Tyler

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