[PATCH 3.10 120/268] apparmor: fix module parameters can be changed after policy is locked

Willy Tarreau
2017-06-19T18:40:40Z

From: John Johansen <john.johansen@canonical.com>

commit 58acf9d911c8831156634a44d0b022d683e1e50c upstream.

the policy_lock parameter is a one way switch that prevents policy
from being further modified. Unfortunately some of the module parameters
can effectively modify policy by turning off enforcement.

split policy_admin_capable into a view check and a full admin check,
and update the admin check to test the policy_lock parameter.

Signed-off-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: Willy Tarreau <w@1wt.eu>
---
security/apparmor/include/policy.h | 2 ++
security/apparmor/lsm.c | 22 ++++++++++------------
security/apparmor/policy.c | 18 +++++++++++++++++-
3 files changed, 29 insertions(+), 13 deletions(-)

diff --git a/security/apparmor/include/policy.h b/security/apparmor/include/policy.h
index bda4569..0c9d121 100644
--- a/security/apparmor/include/policy.h
+++ b/security/apparmor/include/policy.h
@@ -313,6 +313,8 @@ static inline int AUDIT_MODE(struct aa_profile *profile)
return profile->audit;
}

+bool policy_view_capable(void);
+bool policy_admin_capable(void);
bool aa_may_manage_policy(int op);

#endif /* __AA_POLICY_H */
diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index b21830e..6eeaab8 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -759,51 +759,49 @@ __setup("apparmor=", apparmor_enabled_setup);
/* set global flag turning off the ability to load policy */
static int param_set_aalockpolicy(const char *val, const struct kernel_param *kp)
{
- if (!capable(CAP_MAC_ADMIN))
+ if (!policy_admin_capable())
return -EPERM;
- if (aa_g_lock_policy)
- return -EACCES;
return param_set_bool(val, kp);
}

static int param_get_aalockpolicy(char *buffer, const struct kernel_param *kp)
{
- if (!capable(CAP_MAC_ADMIN))
+ if (!policy_view_capable())
return -EPERM;
return param_get_bool(buffer, kp);
}

static int param_set_aabool(const char *val, const struct kernel_param *kp)
{
- if (!capable(CAP_MAC_ADMIN))
+ if (!policy_admin_capable())
return -EPERM;
return param_set_bool(val, kp);
}

static int param_get_aabool(char *buffer, const struct kernel_param *kp)
{
- if (!capable(CAP_MAC_ADMIN))
+ if (!policy_view_capable())
return -EPERM;
return param_get_bool(buffer, kp);
}

static int param_set_aauint(const char *val, const struct kernel_param *kp)
{
- if (!capable(CAP_MAC_ADMIN))
+ if (!policy_admin_capable())
return -EPERM;
return param_set_uint(val, kp);
}

static int param_get_aauint(char *buffer, const struct kernel_param *kp)
{
- if (!capable(CAP_MAC_ADMIN))
+ if (!policy_view_capable())
return -EPERM;
return param_get_uint(buffer, kp);
}

static int param_get_audit(char *buffer, struct kernel_param *kp)
{
- if (!capable(CAP_MAC_ADMIN))
+ if (!policy_view_capable())
return -EPERM;

if (!apparmor_enabled)
@@ -815,7 +813,7 @@ static int param_get_audit(char *buffer, struct kernel_param *kp)
static int param_set_audit(const char *val, struct kernel_param *kp)
{
int i;
- if (!capable(CAP_MAC_ADMIN))
+ if (!policy_admin_capable())
return -EPERM;

if (!apparmor_enabled)
@@ -836,7 +834,7 @@ static int param_set_audit(const char *val, struct kernel_param *kp)

static int param_get_mode(char *buffer, struct kernel_param *kp)
{
- if (!capable(CAP_MAC_ADMIN))
+ if (!policy_admin_capable())
return -EPERM;

if (!apparmor_enabled)
@@ -848,7 +846,7 @@ static int param_get_mode(char *buffer, struct kernel_param *kp)
static int param_set_mode(const char *val, struct kernel_param *kp)
{
int i;
- if (!capable(CAP_MAC_ADMIN))
+ if (!policy_admin_capable())
return -EPERM;

if (!apparmor_enabled)
diff --git a/security/apparmor/policy.c b/security/apparmor/policy.c
index 8132003..c4780e1 100644
--- a/security/apparmor/policy.c
+++ b/security/apparmor/policy.c
@@ -1002,6 +1002,22 @@ static int audit_policy(int op, gfp_t gfp, const char *name, const char *info,
&sa, NULL);
}

+bool policy_view_capable(void)
+{
+ struct user_namespace *user_ns = current_user_ns();
+ bool response = false;
+
+ if (ns_capable(user_ns, CAP_MAC_ADMIN))
+ response = true;
+
+ return response;
+}
+
+bool policy_admin_capable(void)
+{
+ return policy_view_capable() && !aa_g_lock_policy;
+}
+
/**
* aa_may_manage_policy - can the current task manage policy
* @op: the policy manipulation operation being done
@@ -1016,7 +1032,7 @@ bool aa_may_manage_policy(int op)
return 0;
}

- if (!capable(CAP_MAC_ADMIN)) {
+ if (!policy_admin_capable()) {
audit_policy(op, GFP_KERNEL, NULL, "not policy admin", -EACCES);
return 0;
}
--
2.8.0.rc2.1.gbe9624a