From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B4C1DC433DF for ; Thu, 9 Jul 2020 19:54:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9227020720 for ; Thu, 9 Jul 2020 19:54:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="WUO7OAm/" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726323AbgGITyp (ORCPT ); Thu, 9 Jul 2020 15:54:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40878 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726324AbgGITyb (ORCPT ); Thu, 9 Jul 2020 15:54:31 -0400 Received: from mail-ot1-x342.google.com (mail-ot1-x342.google.com [IPv6:2607:f8b0:4864:20::342]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A1F45C08C5DC; Thu, 9 Jul 2020 12:54:30 -0700 (PDT) Received: by mail-ot1-x342.google.com with SMTP id 72so2562746otc.3; Thu, 09 Jul 2020 12:54:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=hVmQvgceNuE9gUqdw2DsWEuHafaDdw4hAjlnC4YG72Y=; b=WUO7OAm/JvOW4KqGTnvLba/3moYHZm+U0elK80Kg/jIZ2sy6WupncyOA8VWFoJqDfv fNLS57kO0agV+2pxUCakNB8gRibz+JJKKh96mlEjgjd2MrqqHzMwDI/E6uUYMNp8mKfQ Hdk+r02QnRnZ4jPba7mhvgW7jOBMIAGMODpvZ96jbyapUd03KaoeUsh0X3c/TT6yjaev 7ldr6anw0uuZ6QsX5aiiingcdRT9Ua96whnpamWVqzeUVft3LiJ9QCKWqBW/rmbqqI8D WW363pHnF24DgmufyI2wX/Hpn+zaVL22RHaOU0LQg72qFZXGHgA3BV/JbZ1EO2vQ3baT Et/w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=hVmQvgceNuE9gUqdw2DsWEuHafaDdw4hAjlnC4YG72Y=; b=tfWr0u8e5VHbdE8mdxsPbEuU9z6cYpW+NHXO+6RXSw6ymeyYPAqdtW/KLZdeG7GNVC 41mawUUstNfFXokCkAwj0rTnlp6pWDMEY9ziZ5vhATQ9KDANwm3q+KnclTaaTE21pTmH VVk3/IE4rSARGWSne8HhD5XMpXXU2e/VTxVdE+3g30czJwNLUHo+T4JIV6dlBuj7sHb0 GePcaPQ5QWN15+YsLH3KBoydZE+bU48cbDOBmegweHcHS4/TsEMYStOyNzuWqRm26XPD Bjxbt2Kt1lckRGH8qqomhcbZz8UYtGgrqMSUGfF4vYav9dmr/F1mkfMAN1um6ho4PXju nbLg== X-Gm-Message-State: AOAM533MkNrhTIApxNWmlQ/e2Fdo4AFVbu8JJad0a/Tad1GhCSrSZZm5 vRu85AuZ3UFYiClbcjUbsz9sP6IXRXj8OXf3PpI= X-Google-Smtp-Source: ABdhPJxLRHXxRYPjMXMuu7fmQF2k7SyAJfy80oyydcFchNTduoj/UXX0VNfiX9z74zqibft67E/O9oKBned2Vg51NM4= X-Received: by 2002:a05:6830:1db5:: with SMTP id z21mr41453019oti.162.1594324470006; Thu, 09 Jul 2020 12:54:30 -0700 (PDT) MIME-Version: 1.0 References: <20200709001234.9719-1-casey@schaufler-ca.com> <20200709001234.9719-6-casey@schaufler-ca.com> <8a5a243f-e991-ad55-0503-654cc2587133@canonical.com> In-Reply-To: <8a5a243f-e991-ad55-0503-654cc2587133@canonical.com> From: Stephen Smalley Date: Thu, 9 Jul 2020 15:54:19 -0400 Message-ID: Subject: Re: [PATCH v18 05/23] net: Prepare UDS for security module stacking To: John Johansen Cc: Casey Schaufler , Casey Schaufler , James Morris , LSM List , SElinux list , Kees Cook , Tetsuo Handa , Paul Moore , Stephen Smalley , netdev@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: On Thu, Jul 9, 2020 at 12:28 PM John Johansen wrote: > > On 7/9/20 9:11 AM, Stephen Smalley wrote: > > On Wed, Jul 8, 2020 at 8:23 PM Casey Schaufler wrote: > >> > >> Change the data used in UDS SO_PEERSEC processing from a > >> secid to a more general struct lsmblob. Update the > >> security_socket_getpeersec_dgram() interface to use the > >> lsmblob. There is a small amount of scaffolding code > >> that will come out when the security_secid_to_secctx() > >> code is brought in line with the lsmblob. > >> > >> The secid field of the unix_skb_parms structure has been > >> replaced with a pointer to an lsmblob structure, and the > >> lsmblob is allocated as needed. This is similar to how the > >> list of passed files is managed. While an lsmblob structure > >> will fit in the available space today, there is no guarantee > >> that the addition of other data to the unix_skb_parms or > >> support for additional security modules wouldn't exceed what > >> is available. > >> > >> Reviewed-by: Kees Cook > >> Signed-off-by: Casey Schaufler > >> Cc: netdev@vger.kernel.org > >> --- > > > >> diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c > >> index 3385a7a0b231..d246aefcf4da 100644 > >> --- a/net/unix/af_unix.c > >> +++ b/net/unix/af_unix.c > >> @@ -138,17 +138,23 @@ static struct hlist_head *unix_sockets_unbound(void *addr) > >> #ifdef CONFIG_SECURITY_NETWORK > >> static void unix_get_secdata(struct scm_cookie *scm, struct sk_buff *skb) > >> { > >> - UNIXCB(skb).secid = scm->secid; > >> + UNIXCB(skb).lsmdata = kmemdup(&scm->lsmblob, sizeof(scm->lsmblob), > >> + GFP_KERNEL); > >> } > >> > >> static inline void unix_set_secdata(struct scm_cookie *scm, struct sk_buff *skb) > >> { > >> - scm->secid = UNIXCB(skb).secid; > >> + if (likely(UNIXCB(skb).lsmdata)) > >> + scm->lsmblob = *(UNIXCB(skb).lsmdata); > >> + else > >> + lsmblob_init(&scm->lsmblob, 0); > >> } > >> > >> static inline bool unix_secdata_eq(struct scm_cookie *scm, struct sk_buff *skb) > >> { > >> - return (scm->secid == UNIXCB(skb).secid); > >> + if (likely(UNIXCB(skb).lsmdata)) > >> + return lsmblob_equal(&scm->lsmblob, UNIXCB(skb).lsmdata); > >> + return false; > >> } > > > > I don't think that this provides sensible behavior to userspace. On a > > transient memory allocation failure, instead of returning an error to > > the sender and letting them handle it, this will just proceed with > > sending the message without its associated security information, and > > potentially split messages on arbitrary boundaries because it cannot > > tell whether the sender had the same security information. I think > > you instead need to change unix_get_secdata() to return an error on > > allocation failure and propagate that up to the sender. Not a fan of > > this change in general both due to extra overhead on this code path > > and potential for breakage on allocation failures. I know it was > > motivated by paul's observation that we won't be able to fit many more > > secids into the cb but not sure we have to go there prematurely, > > especially absent its usage by upstream AA (no unix_stream_connect > > hook implementation upstream). Also not sure how the whole bpf local > > I'm not sure how premature it is, I am running late for 5.9 but would > like to land apparmor unix mediation in 5.10 Sorry I think I mischaracterized the condition under which this support needs to be stacked. It seems to only be needed if using SO_PASSSEC and SCM_SECURITY (i.e. datagram labeling), not just for unix mediation or SO_PEERSEC IIUC. So not sure if that applies even for downstream.