Date: Tue, 27 Jan 2015 16:08:28 -0800 From: Devin Teske <dteske@FreeBSD.org> To: Baptiste Daroussin <bapt@FreeBSD.org> Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, Bruce Evans <brde@optusnet.com.au>, Slawa Olhovchenkov <slw@zxy.spb.ru>, svn-src-head@freebsd.org, Devin Teske <dteske@FreeBSD.org> Subject: Re: svn commit: r277652 - in head/usr.sbin/pw: . tests Message-ID: <AD40C8A5-3ACC-468C-8BB0-A0B466098328@FreeBSD.org> In-Reply-To: <20150127234420.GB84622@ivaldir.etoilebsd.net> References: <201501241913.t0OJD4xT039188@svn.freebsd.org> <20150125155254.V1007@besplex.bde.org> <20150125142148.GA76051@zxy.spb.ru> <20150126014336.P2572@besplex.bde.org> <5D58B34B-8647-4B69-8D90-E7D37C98D4AD@FreeBSD.org> <20150127234420.GB84622@ivaldir.etoilebsd.net>
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> On Jan 27, 2015, at 3:44 PM, Baptiste Daroussin <bapt@FreeBSD.org> wrote: > > On Mon, Jan 26, 2015 at 01:20:28PM -0800, Devin Teske wrote: >> >>> On Jan 25, 2015, at 7:31 AM, Bruce Evans <brde@optusnet.com.au> wrote: >>> >>> On Sun, 25 Jan 2015, Slawa Olhovchenkov wrote: >>> >>>> On Sun, Jan 25, 2015 at 04:56:24PM +1100, Bruce Evans wrote: >>>> >>>>> Negative ids have historical abuses in places like mountd. >> >> Which paves the way for the “accepted practice” argument >> and backed up by “in-the-field usage” statement(s). >> >> >> >>>>> mountd still >>>>> hard-codes -2 and -2 for the default uid and gid of an unprivileged user. >>>>> It at least casts these values to uid_t and gid_t before using them. >>>>> This gives the ids the non-random values of UINT32_MAX-1 if uid_t and >>>>> gid_t are uint32_t. (If uid_t and gid_t were signed, then it would >>>>> leave the values as negative, so invalid.) These magic values may work >>>>> better than when ids were 16 bits, since there is less risk of them >>>>> conflicting with a normal id. However, the non-conflict is probably >>>>> a bug. FreeBSD uses the magic ids of 65534 for user nobody: group >>>>> nobody. These would have been (id_t)-2 with 16-bit ids. They no >>>>> longer match, so ls displays (id_t)-2 numerically. FreeBSD also has >>>>> a group nogroup = 65553 that doesn't match the nfs usage. However2, >>>>> in FreeBSD-1 wher ids were 16-bits, nobody was 32767 and nogroup was >>>>> 32766. so they didn't match nfs for other reasons. The 2 non-groups >>>>> now seem to be just a bug -- FreeBSD-1 didn't have group nobody. >>>>> 4.4BSD-Lite2 has the same values as FreeBSD-1. >>>> >>>> This is not full true for ZFS case. >>>> On ZFS nobody is 2^32-2. >>> >>> File systems don't get to decide this. >> >> +1 (and thanks for the historical account, bruce — sincerely) >> >> However, I still want to make the argument that: >> >> a. Because we’ve supported mapping negative inputs to unsigned values in pw *for over a decade*, that… >> >> b. We should either revert or make a relnotes submission to note that we’re changing the long-standing accepted practice. >> >> Changing the accepted practice broke code internally, it would have likely broken some external code as well — and people deserve to know about said change else we should continue to support accepted practice that is decade(s) old. > > It has never been accepted by pw(8) it was just not checked Those are indistinguishable from each other by an end-user (someone not reading the code; and even still there is the “spirit” of the code and the “letter of the code"). > as a result it was > accepting *anything* and passed it unchecked directly to atoi(3) resulting in > for example pw groupdel -u plop removing wheel... or pw userdel -u something > trying to delete root. (was this an accepted behaviour for a decade as well?) > The erroneous deletion was inherently wrong. I do not want to see that bug resurface (and I thank you very much for fixing it). However, I’m sure you know that said erroneous deletion was a side-effect of lacking error-checks. Again, thank you fixing the PR itemizing the erroneous deletion of users/groups. Please note that Bruce sent me a private e-mail with some historical background, to which I replied and we’re working out some logic on the side. There shouldn’t be much more to this thread — I envision that we’ll be approaching a solid agree- meant that should lead to some commits (can’t say yet what direction it will go as I’m looking forward to Bruce’s touch-points). — Devin
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