Re: [RFC PATCH 22/27] KEYS: Replace uid/gid/perm permissions checking with an ACL

David Howells
2019-02-15T17:39:41Z

Stephen Smalley <sds@tycho.nsa.gov> wrote:

> > --- a/security/selinux/hooks.c
> > +++ b/security/selinux/hooks.c
> > @@ -6560,6 +6560,7 @@ static int selinux_key_permission(key_ref_t key_ref,
> > {
> > struct key *key;
> > struct key_security_struct *ksec;
> > + unsigned oldstyle_perm;
> > u32 sid;
> > /* if no specific permissions are requested, we skip the
> > @@ -6568,13 +6569,26 @@ static int selinux_key_permission(key_ref_t key_ref,
> > if (perm == 0)
> > return 0;
> > + oldstyle_perm = perm & (KEY_NEED_VIEW | KEY_NEED_READ | KEY_NEED_WRITE
> > |
> > + KEY_NEED_SEARCH | KEY_NEED_LINK);
> > + if (perm & KEY_NEED_SETSEC)
> > + oldstyle_perm |= OLD_KEY_NEED_SETATTR;
> > + if (perm & KEY_NEED_INVAL)
> > + oldstyle_perm |= KEY_NEED_SEARCH;
> > + if (perm & KEY_NEED_REVOKE && !(perm & OLD_KEY_NEED_SETATTR))
> > + oldstyle_perm |= KEY_NEED_WRITE;
> > + if (perm & KEY_NEED_JOIN)
> > + oldstyle_perm |= KEY_NEED_SEARCH;
> > + if (perm & KEY_NEED_CLEAR)
> > + oldstyle_perm |= KEY_NEED_WRITE;
> > +
> > sid = cred_sid(cred);
> > key = key_ref_to_ptr(key_ref);
> > ksec = key->security;
> > return avc_has_perm(&selinux_state,
> > - sid, ksec->sid, SECCLASS_KEY, perm, NULL);
> > + sid, ksec->sid, SECCLASS_KEY, oldstyle_perm, NULL);
>
> This might be ok temporarily for compatibility but we'll want to ultimately
> define the new permissions in SELinux and switch over to using them if a new
> policy capability bit is set to indicate that the policy supports them. We
> should probably decouple the SELinux permission bits from the KEY_NEED_*
> values and explicitly map them all at the same time.

Sounds reasonable. I should probably detach the first two ACL patches from
the set and push them separately.

David