Factor out the case of privileged root from the function
cap_bprm_set_creds() to make the latter easier to read and analyse.
Suggested-by: Serge Hallyn <se...@hallyn.com>
Signed-off-by: Richard Guy Briggs <r...@redhat.com>
Reviewed-by: Serge Hallyn <se...@hallyn.com>
Acked-by: James Morris <james.l.mor...@oracle.com>
Acked-by: Kees Cook <keesc...@chromium.org>
Okay-ished-by: Paul Moore <p...@paul-moore.com>
---
security/commoncap.c | 76 +++++++++++++++++++++++++++++++++-------------------
1 file changed, 48 insertions(+), 28 deletions(-)
diff --git a/security/commoncap.c b/security/commoncap.c
index c25e0d2..be9bca5 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -695,6 +695,52 @@ static int get_file_caps(struct linux_binprm *bprm, bool
*effective, bool *has_c
return rc;
}
+/*
+ * handle_privileged_root - Handle case of privileged root
+ * @bprm: The execution parameters, including the proposed creds
+ * @has_fcap: Are any file capabilities set?
+ * @effective: Do we have effective root privilege?
+ * @root_uid: This namespace' root UID WRT initial USER namespace
+ *
+ * Handle the case where root is privileged and hasn't been neutered by
+ * SECURE_NOROOT. If file capabilities are set, they won't be combined with
+ * set UID root and nothing is changed. If we are root, cap_permitted is
+ * updated. If we have become set UID root, the effective bit is set.
+ */
+static void handle_privileged_root(struct linux_binprm *bprm, bool has_cap,
+ bool *effective, kuid_t root_uid)
+{
+ const struct cred *old = current_cred();
+ struct cred *new = bprm->cred;
+
+ if (issecure(SECURE_NOROOT))
+ return;
+ /*
+ * If the legacy file capability is set, then don't set privs
+ * for a setuid root binary run by a non-root user. Do set it
+ * for a root user just to cause least surprise to an admin.
+ */
+ if (has_cap && !uid_eq(new->uid, root_uid) && uid_eq(new->euid,
root_uid)) {
+ warn_setuid_and_fcaps_mixed(bprm->filename);
+ return;
+ }
+ /*
+ * To support inheritance of root-permissions and suid-root
+ * executables under compatibility mode, we override the
+ * capability sets for the file.
+ */
+ if (uid_eq(new->euid, root_uid) || uid_eq(new->uid, root_uid)) {
+ /* pP' = (cap_bset & ~0) | (pI & ~0) */
+ new->cap_permitted = cap_combine(old->cap_bset,
+ old->cap_inheritable);
+ }
+ /*
+ * If only the real uid is 0, we do not set the effective bit.
+ */
+ if (uid_eq(new->euid, root_uid))
+ *effective = true;
+}
+
/**
* cap_bprm_set_creds - Set up the proposed credentials for execve().
* @bprm: The execution parameters, including the proposed creds
@@ -707,46 +753,20 @@ int cap_bprm_set_creds(struct linux_binprm *bprm)
{
const struct cred *old = current_cred();
struct cred *new = bprm->cred;
- bool effective, has_cap = false, is_setid;
+ bool effective = false, has_cap = false, is_setid;
int ret;
kuid_t root_uid;
if (WARN_ON(!cap_ambient_invariant_ok(old)))
return -EPERM;
- effective = false;
ret = get_file_caps(bprm, &effective, &has_cap);
if (ret < 0)
return ret;
root_uid = make_kuid(new->user_ns, 0);
- if (!issecure(SECURE_NOROOT)) {
- /*
- * If the legacy file capability is set, then don't set privs
- * for a setuid root binary run by a non-root user. Do set it
- * for a root user just to cause least surprise to an admin.
- */
- if (has_cap && !uid_eq(new->uid, root_uid) && uid_eq(new->euid,
root_uid)) {
- warn_setuid_and_fcaps_mixed(bprm->filename);
- goto skip;
- }
- /*
- * To support inheritance of root-permissions and suid-root
- * executables under compatibility mode, we override the
- * capability sets for the file.
- *
- * If only the real uid is 0, we do not set the effective bit.
- */
- if (uid_eq(new->euid, root_uid) || uid_eq(new->uid, root_uid)) {
- /* pP' = (cap_bset & ~0) | (pI & ~0) */
- new->cap_permitted = cap_combine(old->cap_bset,
- old->cap_inheritable);
- }
- if (uid_eq(new->euid, root_uid))
- effective = true;
- }
-skip:
+ handle_privileged_root(bprm, has_cap, &effective, root_uid);
/* if we have fs caps, clear dangerous personality flags */
if (!cap_issubset(new->cap_permitted, old->cap_permitted))
--
1.8.3.1
