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Subject[PATCH v3 2/4] Fix apparmor for PR_{GET,SET}_NO_NEW_PRIVS
Date
From: John Johansen <john.johansen@canonical.com>

Signed-off-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
---
security/apparmor/domain.c | 39 +++++++++++++++++++++++++++++++++++----
1 files changed, 35 insertions(+), 4 deletions(-)
diff --git a/security/apparmor/domain.c b/security/apparmor/domain.c
index fcfb610..7316d77 100644
--- a/security/apparmor/domain.c
+++ b/security/apparmor/domain.c
@@ -360,10 +360,6 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
if (bprm->cred_prepared)
return 0;

- /* XXX: no_new_privs is not usable with AppArmor yet */
- if (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)
- return -EPERM;
-
cxt = bprm->cred->security;
BUG_ON(!cxt);

@@ -399,6 +395,11 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
new_profile = find_attach(ns, &ns->base.profiles, name);
if (!new_profile)
goto cleanup;
+ /*
+ * NOTE: Domain transitions from unconfined are allowed
+ * even when no_new_privs is set because this aways results
+ * in a further reduction of permissions.
+ */
goto apply;
}

@@ -459,6 +460,16 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
/* fail exec */
error = -EACCES;

+ /*
+ * Policy has specified a domain transition, if no_new_privs then
+ * fail the exec.
+ */
+ if (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS) {
+ aa_put_profile(new_profile);
+ error = -EPERM;
+ goto cleanup;
+ }
+
if (!new_profile)
goto audit;

@@ -613,6 +624,14 @@ int aa_change_hat(const char *hats[], int count, u64 token, bool permtest)
const char *target = NULL, *info = NULL;
int error = 0;

+ /*
+ * Fail explicitly requested domain transitions if no_new_privs.
+ * There is no exception for unconfined as change_hat is not
+ * available.
+ */
+ if (current->no_new_privs)
+ return -EPERM;
+
/* released below */
cred = get_current_cred();
cxt = cred->security;
@@ -754,6 +773,18 @@ int aa_change_profile(const char *ns_name, const char *hname, bool onexec,
cxt = cred->security;
profile = aa_cred_profile(cred);

+ /*
+ * Fail explicitly requested domain transitions if no_new_privs
+ * and not unconfined.
+ * Domain transitions from unconfined are allowed even when
+ * no_new_privs is set because this aways results in a reduction
+ * of permissions.
+ */
+ if (current->no_new_privs && !unconfined(profile)) {
+ put_cred(cred);
+ return -EPERM;
+ }
+
if (ns_name) {
/* released below */
ns = aa_find_namespace(profile->ns, ns_name);
--
1.7.7.6


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