On Tue, May 12, 2020 at 6:33 PM David Howells <dhowells@xxxxxxxxxx> wrote:
> Since the meaning of combining the KEY_NEED_* constants is undefined, make
> it so that you can't do that by turning them into an enum.
>
> The enum is also given some extra values to represent special
> circumstances, such as:
>
> (1) The '0' value is reserved and causes a warning to trap the parameter
> being unset.
>
> (2) The key is to be unlinked and we require no permissions on it, only
> the keyring, (this replaces the KEY_LOOKUP_FOR_UNLINK flag).
>
> (3) An override due to CAP_SYS_ADMIN.
>
> (4) An override due to an instantiation token being present.
>
> (5) The permissions check is being deferred to later key_permission()
> calls.
>
> The extra values give the opportunity for LSMs to audit these situations.
>
> Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
> cc: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
> cc: Paul Moore <paul@xxxxxxxxxxxxxx>
> cc: Stephen Smalley <stephen.smalley.work@xxxxxxxxx>
> cc: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
> cc: keyrings@xxxxxxxxxxxxxxx
> cc: selinux@xxxxxxxxxxxxxxx
> ---
>
> include/linux/key.h | 30 ++++++++++++++++-----------
> include/linux/security.h | 6 +++--
> security/keys/internal.h | 8 ++++---
> security/keys/keyctl.c | 16 ++++++++-------
> security/keys/permission.c | 31 ++++++++++++++++++++++------
> security/keys/process_keys.c | 46 ++++++++++++++++++++----------------------
> security/security.c | 6 +++--
> security/selinux/hooks.c | 25 ++++++++++++++++-------
> security/smack/smack_lsm.c | 31 +++++++++++++++++++++-------
> 9 files changed, 124 insertions(+), 75 deletions(-)
Thanks for clarifying this, it helps a lot.
My comments below are nitpicky, but take them into account, the style
of the SELinux code changes makes my eyes hurt.
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 0b4e32161b77..3ff6b6dfc5ca 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -6541,20 +6541,31 @@ static void selinux_key_free(struct key *k)
>
> static int selinux_key_permission(key_ref_t key_ref,
> const struct cred *cred,
> - unsigned perm)
> + enum key_need_perm need_perm)
> {
> struct key *key;
> struct key_security_struct *ksec;
> - u32 sid;
> + u32 perm, sid;
>
> - /* if no specific permissions are requested, we skip the
> - permission check. No serious, additional covert channels
> - appear to be created. */
> - if (perm == 0)
> + switch (need_perm) {
> + case KEY_NEED_UNLINK:
> + case KEY_SYSADMIN_OVERRIDE:
> + case KEY_AUTHTOKEN_OVERRIDE:
> + case KEY_DEFER_PERM_CHECK:
> return 0;
> + default:
> + WARN_ON(1);
> + return -EPERM;
Please move the default case to the bottom of the switch statement.
> - sid = cred_sid(cred);
> + case KEY_NEED_VIEW: perm = KEY__VIEW; break;
> + case KEY_NEED_READ: perm = KEY__READ; break;
> + case KEY_NEED_WRITE: perm = KEY__WRITE; break;
> + case KEY_NEED_SEARCH: perm = KEY__SEARCH; break;
> + case KEY_NEED_LINK: perm = KEY__LINK; break;
> + case KEY_NEED_SETATTR: perm = KEY__SETATTR; break;
Please don't put the case statements all on one line, use the more
traditional multi-line format. For example:
case KEY_NEED_SETATTR:
perm = KEY__SETATTR;
break;
> + }
>
> + sid = cred_sid(cred);
> key = key_ref_to_ptr(key_ref);
> ksec = key->security;
--
paul moore
www.paul-moore.com
