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parser: bug fix do not change auditing information when applying deny

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The parser recently changed how/where deny information is applied.
commit 1fa45b7c1 ("parser: dfa minimization prepare for extended
permissions") removed the implicit filtering of explicit denies during
the minimization pass. The implicit clear allowed the explicit
information to be carried into the minimization pass and merged with
implicit denies. The end result being a minimized dfa with the explicit
deny information available to be applied post minimization, and
then dropped later at permission encoding in the accept entries.

Extended permission however enable carrying explicit deny information
into the kernel to fix certain bugs like complain mode not being
able to distinguish between implicit and explicit deny rules (ie.
deny rules get ignored in complain mode). However keeping explicit
deny information when unnecessary result in a larger state machine
than necessary and slower compiles.

commit 179c1c1ba ("parser: fix minimization check for filtering_deny")
Moved the explicit apply_and_clear_deny() pass to before minimization
to restore mnimization's ability to create a minimized dfa with
explicit and implicit deny information merged but this also cleared
the explicit deny information that used to be carried through
minimization. This meant that when the deny information was applied
post minimization it resulted in the audit and quiet information
being cleared.

This resulted in the query_label tests failing as they are checking
for the expected audit infomation in the permissions.

Fixes: 179c1c1ba ("parser: fix minimization check for filtering_deny")
Bug: https://gitlab.com/apparmor/apparmor/-/issues/461
Signed-off-by: John Johansen <john.johansen@canonical.com>
This commit is contained in:
John Johansen 2024-10-27 10:52:36 -06:00 • committed by John Johansen
parent 3d1a3493af
commit 9ea0d4f89b
2 changed files with 14 additions and 4 deletions
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1
parser/libapparmor_re/aare_rules.cc
View file

@ -270,7 +270,6 @@ CHFA *aare_rules::create_chfa(int *min_match_len,
if (opts.control & CONTROL_DFA_MINIMIZE) {
dfa.minimize(opts);
if (opts.dump & DUMP_DFA_MIN_UNIQ_PERMS)
dfa.dump_uniq_perms("minimized dfa");
}

17
parser/libapparmor_re/hfa.h
View file

@ -131,12 +131,23 @@ public:
*/
}
/* returns true if perm is no longer accept */
int apply_and_clear_deny(void)
{
if (deny) {
allow &= ~deny;
exact &= ~deny;
prompt &= ~deny;
quiet &= deny;
/* don't change audit or quiet based on clearing
* deny at this stage. This was made unique in
* accept_perms, and the info about whether
* we are auditing or quieting based on the explicit
* deny has been discarded and can only be inferred.
* But we know it is correct from accept_perms()
* audit &= deny;
* quiet &= deny;
*/
deny = 0;
return !is_accept();
}
@ -282,9 +293,9 @@ public:
{
accept1 = perms.allow;
if (prompt && prompt_compat_mode == PROMPT_COMPAT_DEV)
accept2 = PACK_AUDIT_CTL(perms.prompt, perms.quiet & perms.deny);
accept2 = PACK_AUDIT_CTL(perms.prompt, perms.quiet);
else
accept2 = PACK_AUDIT_CTL(perms.audit, perms.quiet & perms.deny);
accept2 = PACK_AUDIT_CTL(perms.audit, perms.quiet);
accept3 = perms.prompt;
}