On Mon, Apr 27, 2020 at 10:13 AM David Howells <dhowells@xxxxxxxxxx> wrote:
>
> Paul Moore <paul@xxxxxxxxxxxxxx> wrote:
>
> > Okay, can you send the next version of the patch to the SELinux list for
> > review?
>
> Here you go. Note that I did this a few days ago and I actually used EACCES
> rather than EPERM. Which one is one preferred for this?
>
> David
> ---
> 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.
Both function names in the above description are wrong.
> Fixes: d720024e94de ("[PATCH] selinux: add hooks for key subsystem")
> Reported-by: Paul Moore <paul@xxxxxxxxxxxxxx>
> Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
> ---
> security/selinux/hooks.c | 22 ++++++++++++++++++++--
> 1 file changed, 20 insertions(+), 2 deletions(-)
>
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 0b4e32161b77..6087955b49d8 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -6539,20 +6539,38 @@ 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:
Possibly WARN() or BUG() here? Or BUILD_BUG_ON(KEY_NEED_ALL != 0x3f)
to force an update here
whenever a new key permission is defined?
> + 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
> permission check. No serious, additional covert channels
> appear to be created. */
> - if (perm == 0)
> + if (need_perm == 0)
> return 0;
>
> + perm = selinux_keyperm_to_av(need_perm);
> + if (perm == 0)
> + return -EACCES;
We should log or audit some kind of message here, whether via WARN(),
audit_log(), or something, to avoid silent denials.
> sid = cred_sid(cred);
>
> key = key_ref_to_ptr(key_ref);
>
