From: Paul Moore <paul@paul-moore.com>
To: David Howells <dhowells@redhat.com>
Cc: Stephen Smalley <stephen.smalley.work@gmail.com>,
Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
Casey Schaufler <casey@schaufler-ca.com>,
keyrings@vger.kernel.org, selinux@vger.kernel.org,
linux-security-module@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] keys: Make the KEY_NEED_* perms an enum rather than a mask
Date: Tue, 12 May 2020 21:04:29 -0400 [thread overview]
Message-ID: <CAHC9VhQhYz8xZ6MGv0S9q2D-gReb0Pqqb=2+oX=NVuxb_F5WfA@mail.gmail.com> (raw)
In-Reply-To: <158932282880.2885325.2688622278854566047.stgit@warthog.procyon.org.uk>
On Tue, May 12, 2020 at 6:33 PM David Howells <dhowells@redhat.com> 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@redhat.com>
> cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
> cc: Paul Moore <paul@paul-moore.com>
> cc: Stephen Smalley <stephen.smalley.work@gmail.com>
> cc: Casey Schaufler <casey@schaufler-ca.com>
> cc: keyrings@vger.kernel.org
> cc: selinux@vger.kernel.org
> ---
>
> 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
next prev parent reply other threads:[~2020-05-13 1:04 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAEjxPJ6pFdDfm55pv9bT3CV5DTFF9VqzRmG_Xi5bKNxPaGuOLg@mail.gmail.com>
2020-05-12 22:33 ` [PATCH] keys: Make the KEY_NEED_* perms an enum rather than a mask David Howells
2020-05-13 1:04 ` Paul Moore [this message]
2020-05-13 12:58 ` Stephen Smalley
2020-05-13 15:25 ` Casey Schaufler
2020-05-13 23:13 ` David Howells
2020-05-14 12:08 ` Stephen Smalley
2020-05-14 14:45 ` Stephen Smalley
2020-05-13 23:16 ` David Howells
2020-05-13 23:25 ` David Howells
2020-05-14 11:00 ` Jarkko Sakkinen
2020-05-14 16:58 ` [PATCH] keys: Move permissions checking decisions into the checking code David Howells
2020-05-14 17:06 ` Casey Schaufler
2020-05-15 15:06 ` Stephen Smalley
2020-05-15 16:45 ` David Howells
2020-05-15 18:55 ` Stephen Smalley
2020-05-15 19:10 ` Casey Schaufler
2020-05-15 22:27 ` David Howells
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