From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_NONE autolearn=ham autolearn_force=no version=3.4.2 Received: from minnie.tuhs.org (minnie.tuhs.org [45.79.103.53]) by inbox.vuxu.org (OpenSMTPD) with ESMTP id 3c221424 for ; Thu, 1 Aug 2019 12:36:05 +0000 (UTC) Received: by minnie.tuhs.org (Postfix, from userid 112) id 2CCDB9BA2F; Thu, 1 Aug 2019 22:36:03 +1000 (AEST) Received: from minnie.tuhs.org (localhost [127.0.0.1]) by minnie.tuhs.org (Postfix) with ESMTP id 5EFC194903; Thu, 1 Aug 2019 22:35:32 +1000 (AEST) Received: by minnie.tuhs.org (Postfix, from userid 112) id 2767994903; Thu, 1 Aug 2019 22:35:29 +1000 (AEST) Received: from mail.cs.Dartmouth.EDU (mail.cs.dartmouth.edu [129.170.212.100]) by minnie.tuhs.org (Postfix) with ESMTPS id 867F2948EB for ; Thu, 1 Aug 2019 22:35:28 +1000 (AEST) Received: from tahoe.cs.Dartmouth.EDU (tahoe.cs.dartmouth.edu [129.170.212.20]) by mail.cs.Dartmouth.EDU (8.15.2/8.15.2) with ESMTPS id x71CZQdr007099 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO) for ; Thu, 1 Aug 2019 08:35:26 -0400 Received: from tahoe.cs.Dartmouth.EDU (localhost.localdomain [127.0.0.1]) by tahoe.cs.Dartmouth.EDU (8.15.2/8.14.3) with ESMTP id x71CZQjH035026 for ; Thu, 1 Aug 2019 08:35:26 -0400 Received: (from doug@localhost) by tahoe.cs.Dartmouth.EDU (8.15.2/8.15.2/Submit) id x71CZP2B035023 for tuhs@tuhs.org; Thu, 1 Aug 2019 08:35:26 -0400 From: Doug McIlroy Message-Id: <201908011235.x71CZP2B035023@tahoe.cs.Dartmouth.EDU> Date: Thu, 01 Aug 2019 08:35:25 -0400 To: tuhs@tuhs.org User-Agent: Heirloom mailx 12.5 7/5/10 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Subject: Re: [TUHS] Who's behind the UNIX filesystem permission X-BeenThere: tuhs@minnie.tuhs.org X-Mailman-Version: 2.1.26 Precedence: list List-Id: The Unix Heritage Society mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: tuhs-bounces@minnie.tuhs.org Sender: "TUHS" Read and write permission were common ideas--even part of the Atlas paging hardware that was described before 1960. The original concept of time-sharing was to give a virtual computer to each user. When it became clear that sharing was an equally important aspect, owner/other permissions arose. I believe that was the case with Multics. Owner/other permissions were in PDP-11 Unix from the start. Group permissions arose from the ferment of daily talk in the Unix lab. How might the usual protections be extended to collaborative projects? Ken and Dennis deserve credit for the final implementation. Yet clean as the idea of groups was, it has been used only sporadically (in my experience). Execute permission (much overloaded in Unix) also dates back to the dawn of paging. One Unix innovation, due to Dennis, was the suid bit--the only patented feature in the Research system. It was instantly adopted for maintaining the Moo (a game now sold under the name "Master Mind") league standings table. One trouble with full-blown ACLs as required by NSA's Orange Book, is obscurity. It is hard (possibly NP- complete) to analyze the actual security of an ACL configuration. A common failing of Unix administration was a proliferation of suid-root programs, e.g. mail(1). I recall one system that had a hundred such programs. Sudo provided a way station between suid and ACLs. Doug