Ensure auditd Unauthorized Access Attempts To open_by_handle_at Are Ordered Correctly

Description

The audit system should collect detailed unauthorized file accesses for all users and root. To correctly identify unsuccessful creation, unsuccessful modification and unsuccessful access of files via open_by_handle_at syscall the audit rules collecting these events need to be in certain order. The more specific rules need to come before the less specific rules. The reason for that is that more specific rules cover a subset of events covered in the less specific rules, thus, they need to come before to not be overshadowed by less specific rules, which match a bigger set of events. Make sure that rules for unsuccessful calls of open_by_handle_at syscall are in the order shown below. If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), check the order of rules below in a file with suffix .rules in the directory /etc/audit/rules.d. If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, check the order of rules below in /etc/audit/audit.rules file.

-a always,exit -F arch=b32 -S open_by_handle_at -F a2&0100 -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccesful-create
-a always,exit -F arch=b32 -S open_by_handle_at -F a2&0100 -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccesful-create
-a always,exit -F arch=b32 -S open_by_handle_at -F a2&01003 -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccesful-modification
-a always,exit -F arch=b32 -S open_by_handle_at -F a2&01003 -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccesful-modification
-a always,exit -F arch=b32 -S open_by_handle_at -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccesful-access
-a always,exit -F arch=b32 -S open_by_handle_at -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccesful-access

-a always,exit -F arch=b64 -S open_by_handle_at -F a2&0100 -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccesful-create
-a always,exit -F arch=b64 -S open_by_handle_at -F a2&0100 -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccesful-create
-a always,exit -F arch=b64 -S open_by_handle_at -F a2&01003 -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccesful-modification
-a always,exit -F arch=b64 -S open_by_handle_at -F a2&01003 -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccesful-modification
-a always,exit -F arch=b64 -S open_by_handle_at -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccesful-access
-a always,exit -F arch=b64 -S open_by_handle_at -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccesful-access

Rationale

The more specific rules cover a subset of events covered by the less specific rules. By ordering them from more specific to less specific, it is assured that the less specific rule will not catch events better recorded by the more specific rule.