Paul Moore <paul@xxxxxxxxxxxxxx> wrote:
> ... in particular it is the fifth argument to avc_has_perm(),
> "KEY_NEED_VIEW" which is a problem. KEY_NEED_VIEW is not a SELinux
> permission and would likely result in odd behavior when passed to
> avc_has_perm().
I think it works because KEY_NEED_VIEW happens to coincide with KEY__VIEW. It
should just use KEY__VIEW instead.
> it probably makes the most sense to pull the permission mapping in
> selinux_key_permission() out into a separate function, e.g.
> key_perm_to_av(...)
Agreed. How about the attached patch? I wonder if I should do bit-by-bit
translation rather than using a switch? But then it's difficult to decide
what it means if someone passes in two KEY_NEED_* flags OR'd together - is it
either or both?
> and then use this newly created mapping function in [...]
> selinux_watch_key()
No, I think I should just hard-code KEY__VIEW there.
David
---
commit 70d1d82aa014ae4511976b4d80c17138006dddec
Author: David Howells <dhowells@xxxxxxxxxx>
Date: Tue Apr 21 13:15:16 2020 +0100
selinux: Fix use of KEY_NEED_* instead of KEY__* perms
selinux_key_getsecurity() is passing the KEY_NEED_* permissions to
security_sid_to_context() instead of the KEY__* values. It happens to work
because the values are all coincident.
Fixes: d720024e94de ("[PATCH] selinux: add hooks for key subsystem")
Reported-by: Paul Moore <paul@xxxxxxxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 0b4e32161b77..32f7fa538c5f 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -6539,12 +6539,27 @@ static void selinux_key_free(struct key *k)
kfree(ksec);
}
+static unsigned int selinux_keyperm_to_av(unsigned int need_perm)
+{
+ switch (need_perm) {
+ case KEY_NEED_VIEW: return KEY__VIEW;
+ case KEY_NEED_READ: return KEY__READ;
+ case KEY_NEED_WRITE: return KEY__WRITE;
+ case KEY_NEED_SEARCH: return KEY__SEARCH;
+ case KEY_NEED_LINK: return KEY__LINK;
+ case KEY_NEED_SETATTR: return KEY__SETATTR;
+ default:
+ return 0;
+ }
+}
+
static int selinux_key_permission(key_ref_t key_ref,
const struct cred *cred,
- unsigned perm)
+ unsigned need_perm)
{
struct key *key;
struct key_security_struct *ksec;
+ unsigned int perm;
u32 sid;
/* if no specific permissions are requested, we skip the
@@ -6553,6 +6568,7 @@ static int selinux_key_permission(key_ref_t key_ref,
if (perm == 0)
return 0;
+ perm = selinux_keyperm_to_av(need_perm);
sid = cred_sid(cred);
key = key_ref_to_ptr(key_ref);
