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=-8.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham 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 D352CC54FCB for ; Tue, 21 Apr 2020 00:18:25 +0000 (UTC) Received: from us-smtp-delivery-1.mimecast.com (us-smtp-1.mimecast.com [207.211.31.81]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7FEC92082E for ; Tue, 21 Apr 2020 00:18:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Lsqz7zHw" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7FEC92082E Authentication-Results: mail.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linux-audit-bounces@redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1587428304; h=from:from:sender:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:list-id:list-help: list-unsubscribe:list-subscribe:list-post; bh=MU5xgoiQABGpWc1/3Qim8DCPbSvnhygnFzkE1RdxDcc=; b=Lsqz7zHwR0VIdlKb59M0cLsQbiYpPZTPX5GWep4RmreoNbtvpFjASbCWVZDKUVcNefljA8 +OqvxREFvw0FSIMktrsDLknXL72Wu2Uir8MGAYOG2GSUt1Ix02LCjDurWx1e4+XpmZps2c eZdCUSsG71LQx1wreGSLRF4O8jHc0TY= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-63-7pN8w3IYOdexUM_HbrGLKg-1; Mon, 20 Apr 2020 20:18:22 -0400 X-MC-Unique: 7pN8w3IYOdexUM_HbrGLKg-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 41F441853887; Tue, 21 Apr 2020 00:18:19 +0000 (UTC) Received: from colo-mx.corp.redhat.com (colo-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.21]) by smtp.corp.redhat.com (Postfix) with ESMTPS id DFBD976E73; Tue, 21 Apr 2020 00:18:18 +0000 (UTC) Received: from lists01.pubmisc.prod.ext.phx2.redhat.com (lists01.pubmisc.prod.ext.phx2.redhat.com [10.5.19.33]) by colo-mx.corp.redhat.com (Postfix) with ESMTP id 2A2F393902; Tue, 21 Apr 2020 00:18:18 +0000 (UTC) Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) by lists01.pubmisc.prod.ext.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id 03L0IG1i007199 for ; Mon, 20 Apr 2020 20:18:16 -0400 Received: by smtp.corp.redhat.com (Postfix) id 2C46B76E66; Tue, 21 Apr 2020 00:18:16 +0000 (UTC) Received: from madcap2.tricolour.ca (unknown [10.3.128.9]) by smtp.corp.redhat.com (Postfix) with ESMTPS id CA2EA76E76; Tue, 21 Apr 2020 00:18:08 +0000 (UTC) Date: Mon, 20 Apr 2020 20:18:06 -0400 From: Richard Guy Briggs To: Lenny Bruzenak Subject: Re: [PATCH] audit: check the length of userspace generated audit records Message-ID: <20200421001805.imgllrwuir7i4ry7@madcap2.tricolour.ca> References: <158741856073.246860.5955712228915579.stgit@chester> <20200420215615.chh4c5ytxumadtt7@madcap2.tricolour.ca> <728a2bfa-a5f2-4178-49f1-405adef62ee4@magitekltd.com> MIME-Version: 1.0 In-Reply-To: <728a2bfa-a5f2-4178-49f1-405adef62ee4@magitekltd.com> User-Agent: NeoMutt/20180716 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-loop: linux-audit@redhat.com Cc: linux-audit@redhat.com X-BeenThere: linux-audit@redhat.com X-Mailman-Version: 2.1.12 Precedence: junk List-Id: Linux Audit Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-audit-bounces@redhat.com Errors-To: linux-audit-bounces@redhat.com X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Content-Disposition: inline On 2020-04-20 17:56, Lenny Bruzenak wrote: > On 4/20/20 5:29 PM, Paul Moore wrote: > > > On Mon, Apr 20, 2020 at 5:56 PM Richard Guy Briggs wrote: > > > On 2020-04-20 17:36, Paul Moore wrote: > > > > Commit 756125289285 ("audit: always check the netlink payload length > > > > in audit_receive_msg()") fixed a number of missing message length > > > > checks, but forgot to check the length of userspace generated audit > > > > records. The good news is that you need CAP_AUDIT_WRITE to submit > > > > userspace audit records, which is generally only given to trusted > > > > processes, so the impact should be limited. > > > > > > > > Cc:stable@vger.kernel.org > > > > Fixes: 756125289285 ("audit: always check the netlink payload length in audit_receive_msg()") > > > > Reported-by:syzbot+49e69b4d71a420ceda3e@syzkaller.appspotmail.com > > > > Signed-off-by: Paul Moore > > > > --- > > > > kernel/audit.c | 3 +++ > > > > 1 file changed, 3 insertions(+) > > > > > > > > diff --git a/kernel/audit.c b/kernel/audit.c > > > > index b69c8b460341..87f31bf1f0a0 100644 > > > > --- a/kernel/audit.c > > > > +++ b/kernel/audit.c > > > > @@ -1326,6 +1326,9 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh) > > > > case AUDIT_FIRST_USER_MSG2 ... AUDIT_LAST_USER_MSG2: > > > > if (!audit_enabled && msg_type != AUDIT_USER_AVC) > > > > return 0; > > > > + /* exit early if there isn't at least one character to print */ > > > > + if (data_len < 2) > > > > + return -EINVAL; > > > Don't we want to issue the record even if the message is empty? If a > > > len of 1 is passed in, it will properly set str[0] = '\0' and str points > > > to a location with a null that prints nothing between the single quotes > > > of "msg=''". So, I think that should be "if (data_len < 1)". > > > > > > Am I missing something? > > I've got no problem with allowing an empty message so long as there is > > a valid use for such a message. Can anyone think of a valid reason > > for having an empty userspace generated record? > > Not really. Using the libaudit interface(s), even if an empty message string > is sent, and handled in the lib call(s), I believe it will have minimum > contextual info, e.g. "exe=... hostname=... ", etc. > > I can't think of a valid reason myself, assuming IIUC. But even with an empty message, there is still pid, uid, auid, ses, subj added by the kernel with its own message type. I could see a valid type of user message created that has no need for any of those fields added by audit_log_user_message(), calling audit_send_user_message() directly (but mind you, it appears to be deprecated to call it directly). > LCB - RGB -- Richard Guy Briggs Sr. S/W Engineer, Kernel Security, Base Operating Systems Remote, Ottawa, Red Hat Canada IRC: rgb, SunRaycer Voice: +1.647.777.2635, Internal: (81) 32635 -- Linux-audit mailing list Linux-audit@redhat.com https://www.redhat.com/mailman/listinfo/linux-audit