From ce9e3b3fa25a239f5c80989a1d05719bb2793fd4 Mon Sep 17 00:00:00 2001
From: John Johansen <john.johansen@canonical.com>
Date: Thu, 4 Jan 2024 09:00:49 -0800
Subject: [PATCH] apparmor: add ability to mediate caps with policy state
 machine

Currently the caps encoding is very limited and can't be used with
conditionals. Allow capabilities to be mediated by the state
machine. This will allow us to add conditionals to capabilities that
aren't possible with the current encoding.

This patch only adds support for using the state machine and retains
the old encoding lookup as part of the runtime mediation code to
support older policy abis. A follow on patch will move backwards
compatibility to a mapping function done at policy load time.

Signed-off-by: John Johansen <john.johansen@canonical.com>
---
 security/apparmor/capability.c         | 56 ++++++++++++++++++++++++++
 security/apparmor/include/capability.h |  1 +
 security/apparmor/lsm.c                | 11 +++--
 3 files changed, 62 insertions(+), 6 deletions(-)

diff --git a/security/apparmor/capability.c b/security/apparmor/capability.c
index 7ca489ee1054f..25b6219cdeb6b 100644
--- a/security/apparmor/capability.c
+++ b/security/apparmor/capability.c
@@ -27,6 +27,7 @@
 
 struct aa_sfs_entry aa_sfs_entry_caps[] = {
 	AA_SFS_FILE_STRING("mask", AA_SFS_CAPS_MASK),
+	AA_SFS_FILE_BOOLEAN("extended", 1),
 	{ }
 };
 
@@ -123,8 +124,31 @@ static int profile_capable(struct aa_profile *profile, int cap,
 {
 	struct aa_ruleset *rules = list_first_entry(&profile->rules,
 						    typeof(*rules), list);
+	aa_state_t state;
 	int error;
 
+	state = RULE_MEDIATES(rules, ad->class);
+	if (state) {
+		struct aa_perms perms = { };
+		u32 request;
+
+		/* caps broken into 256 x 32 bit permission chunks */
+		state = aa_dfa_next(rules->policy->dfa, state, cap >> 5);
+		request = 1 << (cap & 0x1f);
+		perms = *aa_lookup_perms(rules->policy, state);
+		aa_apply_modes_to_perms(profile, &perms);
+
+		if (opts & CAP_OPT_NOAUDIT) {
+			if (perms.complain & request)
+				ad->info = "optional: no audit";
+			else
+				ad = NULL;
+		}
+		return aa_check_perms(profile, &perms, request, ad,
+				      audit_cb);
+	}
+
+	/* fallback to old caps mediation that doesn't support conditionals */
 	if (cap_raised(rules->caps.allow, cap) &&
 	    !cap_raised(rules->caps.denied, cap))
 		error = 0;
@@ -168,3 +192,35 @@ int aa_capable(const struct cred *subj_cred, struct aa_label *label,
 
 	return error;
 }
+
+kernel_cap_t aa_profile_capget(struct aa_profile *profile)
+{
+	struct aa_ruleset *rules = list_first_entry(&profile->rules,
+						    typeof(*rules), list);
+	aa_state_t state;
+
+	state = RULE_MEDIATES(rules, AA_CLASS_CAP);
+	if (state) {
+		kernel_cap_t caps = CAP_EMPTY_SET;
+		int i;
+
+		/* caps broken into up to 256, 32 bit permission chunks */
+		for (i = 0; i < (CAP_LAST_CAP >> 5); i++) {
+			struct aa_perms perms = { };
+			aa_state_t tmp;
+
+			tmp = aa_dfa_next(rules->policy->dfa, state, i);
+			perms = *aa_lookup_perms(rules->policy, tmp);
+			aa_apply_modes_to_perms(profile, &perms);
+			caps.val |= ((u64)(perms.allow)) << (i * 5);
+			caps.val |= ((u64)(perms.complain)) << (i * 5);
+		}
+		return caps;
+	}
+
+	/* fallback to old caps */
+	if (COMPLAIN_MODE(profile))
+		return CAP_FULL_SET;
+
+	return rules->caps.allow;
+}
diff --git a/security/apparmor/include/capability.h b/security/apparmor/include/capability.h
index d6dcc604ec0cc..1ddcec2d1160d 100644
--- a/security/apparmor/include/capability.h
+++ b/security/apparmor/include/capability.h
@@ -36,6 +36,7 @@ struct aa_caps {
 
 extern struct aa_sfs_entry aa_sfs_entry_caps[];
 
+kernel_cap_t aa_profile_capget(struct aa_profile *profile);
 int aa_capable(const struct cred *subj_cred, struct aa_label *label,
 	       int cap, unsigned int opts);
 
diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index 72c3d1536f690..479bfea064af0 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -177,14 +177,13 @@ static int apparmor_capget(const struct task_struct *target, kernel_cap_t *effec
 
 		label_for_each_confined(i, label, profile) {
 			struct aa_ruleset *rules;
-			if (COMPLAIN_MODE(profile))
-				continue;
+			kernel_cap_t allowed;
+
 			rules = list_first_entry(&profile->rules,
 						 typeof(*rules), list);
-			*effective = cap_intersect(*effective,
-						   rules->caps.allow);
-			*permitted = cap_intersect(*permitted,
-						   rules->caps.allow);
+			allowed = aa_profile_capget(profile);
+			*effective = cap_intersect(*effective, allowed);
+			*permitted = cap_intersect(*permitted, allowed);
 		}
 	}
 	rcu_read_unlock();
-- 
2.47.2