smack: fix access permissions for keyring

BugLink: https://bugs.launchpad.net/bugs/1837664
[ Upstream commit 5b841bfab695e3b8ae793172a9ff7990f99cc3e2 ]

Function smack_key_permission() only issues smack requests for the
following operations:
 - KEY_NEED_READ (issues MAY_READ)
 - KEY_NEED_WRITE (issues MAY_WRITE)
 - KEY_NEED_LINK (issues MAY_WRITE)
 - KEY_NEED_SETATTR (issues MAY_WRITE)
A blank smack request is issued in all other cases, resulting in
smack access being granted if there is any rule defined between
subject and object, or denied with -EACCES otherwise.

Request MAY_READ access for KEY_NEED_SEARCH and KEY_NEED_VIEW.
Fix the logic in the unlikely case when both MAY_READ and
MAY_WRITE are needed. Validate access permission field for valid
contents.

Signed-off-by: Zoran Markovic <zmarkovic@sierrawireless.com>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Cc: Casey Schaufler <casey@schaufler-ca.com>
Cc: James Morris <jmorris@namei.org>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 2b1186b8d13a5cb958a6cc98299c266cf8d32772..0d45c7884f50627f3849041ab65b28150cac40ea 100644 (file)
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -4156,6 +4156,12 @@ static int smack_key_permission(key_ref_t key_ref,
        int request = 0;
        int rc;
 
+       /*
+        * Validate requested permissions
+        */
+       if (perm & ~KEY_NEED_ALL)
+               return -EINVAL;
+
        keyp = key_ref_to_ptr(key_ref);
        if (keyp == NULL)
                return -EINVAL;
@@ -4177,10 +4183,10 @@ static int smack_key_permission(key_ref_t key_ref,
        ad.a.u.key_struct.key = keyp->serial;
        ad.a.u.key_struct.key_desc = keyp->description;
 #endif
-       if (perm & KEY_NEED_READ)
-               request = MAY_READ;
+       if (perm & (KEY_NEED_READ | KEY_NEED_SEARCH | KEY_NEED_VIEW))
+               request |= MAY_READ;
        if (perm & (KEY_NEED_WRITE | KEY_NEED_LINK | KEY_NEED_SETATTR))
-               request = MAY_WRITE;
+               request |= MAY_WRITE;
        rc = smk_access(tkp, skp, request, &ad);
        rc = smk_bu_note("key access", tkp, skp, request, rc);
        return rc;