From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752352AbdGMReC (ORCPT ); Thu, 13 Jul 2017 13:34:02 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:37577 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751153AbdGMReA (ORCPT ); Thu, 13 Jul 2017 13:34:00 -0400 Subject: Re: [PATCH v2] xattr: Enable security.capability in user namespaces To: "Eric W. Biederman" , "Theodore Ts'o" References: <1499785511-17192-1-git-send-email-stefanb@linux.vnet.ibm.com> <1499785511-17192-2-git-send-email-stefanb@linux.vnet.ibm.com> <87mv89iy7q.fsf@xmission.com> <20170712170346.GA17974@mail.hallyn.com> <877ezdgsey.fsf@xmission.com> <74664cc8-bc3e-75d6-5892-f8934404349f@linux.vnet.ibm.com> <20170713011554.xwmrgkzfwnibvgcu@thunk.org> <87y3rscz9j.fsf@xmission.com> <20170713164012.brj2flnkaaks2oci@thunk.org> <87k23cb6os.fsf@xmission.com> Cc: "Serge E. Hallyn" , containers@lists.linux-foundation.org, lkp@01.org, linux-kernel@vger.kernel.org, zohar@linux.vnet.ibm.com, tycho@docker.com, James.Bottomley@HansenPartnership.com, vgoyal@redhat.com, christian.brauner@mailbox.org, amir73il@gmail.com, linux-security-module@vger.kernel.org, casey@schaufler-ca.com From: Stefan Berger Date: Thu, 13 Jul 2017 13:33:53 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: <87k23cb6os.fsf@xmission.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 17071317-0056-0000-0000-000003A69BA8 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00007361; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000214; SDB=6.00887059; UDB=6.00442854; IPR=6.00667200; BA=6.00005470; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00016215; XFM=3.00000015; UTC=2017-07-13 17:33:57 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17071317-0057-0000-0000-000007DCAA01 Message-Id: <847ccb2a-30c0-a94c-df6f-091c8901eaa0@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-07-13_09:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1706020000 definitions=main-1707130274 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/13/2017 01:14 PM, Eric W. Biederman wrote: > Theodore Ts'o writes: > >> On Thu, Jul 13, 2017 at 07:11:36AM -0500, Eric W. Biederman wrote: >>> The concise summary: >>> >>> Today we have the xattr security.capable that holds a set of >>> capabilities that an application gains when executed. AKA setuid root exec >>> without actually being setuid root. >>> >>> User namespaces have the concept of capabilities that are not global but >>> are limited to their user namespace. We do not currently have >>> filesystem support for this concept. >> So correct me if I am wrong; in general, there will only be one >> variant of the form: >> >> security.foo@uid=15000 >> >> It's not like there will be: >> >> security.foo@uid=1000 >> security.foo@uid=2000 >> >> Except.... if you have an Distribution root directory which is shared >> by many containers, you would need to put the xattrs in the overlay >> inodes. Worse, each time you launch a new container, with a new >> subuid allocation, you will have to iterate over all files with >> capabilities and do a copy-up operations on the xattrs in overlayfs. >> So that's actually a bit of a disaster. >> >> So for distribution overlays, you will need to do things a different >> way, which is to map the distro subdirectory so you know that the >> capability with the global uid 0 should be used for the container >> "root" uid, right? >> >> So this hack of using security.foo@uid=1000 is *only* useful when the >> subcontainer root wants to create the privileged executable. You >> still have to do things the other way. >> >> So can we make perhaps the assertion that *either*: >> >> security.foo >> >> exists, *or* >> >> security.foo@uid=BAR >> >> exists, but never both? And there BAR is exclusive to only one >> instances? >> >> Otherwise, I suspect that the architecture is going to turn around and >> bite us in the *ss eventually, because someone will want to do >> something crazy and the solution will not be scalable. > Yep. That is what it looks like from here. > > Which is why I asked the question about scalability of the xattr > implementations. It looks like trying to accomodate the general > case just gets us in trouble, and sets unrealistic expectations. > > Which strongly suggests that Serge's previous version that > just reved the format of security.capable so that a uid field could > be added is likely to be the better approach. > > I want to see what Serge and Stefan have to say but the case looks > pretty clear cut at the moment. The approach of virtualizing the xattrs on the name-side, which is what this patch does, provides a more general approach than to virtualizing it on the value side, which is what Serge does in his other patch for security.capability alone. With the virtualizing on-the-value side virtualizing the xattr becomes an exercise that needs to be repeated for every xattr name that one would want to virtualize. With this patch you would just add another xattr name to a list, a one-line patch in the end. Xattr with prefixes like trusted.* need a bit more work but this can be woven in as well (https://github.com/stefanberger/linux/commit/397b1a3b24045c67405fc83465e544fc865d402f). For virtualizing the xattrs on the 'value' side I was looking for whether there's something like a 'wrapper' structure around the actual value of the xattr so that that wrapper could be extended to support different values at different uids and applied to any xattr. Unfortunately there's no such 'wrapper'. Stefan > > Eric > From mboxrd@z Thu Jan 1 00:00:00 1970 From: stefanb@linux.vnet.ibm.com (Stefan Berger) Date: Thu, 13 Jul 2017 13:33:53 -0400 Subject: [PATCH v2] xattr: Enable security.capability in user namespaces In-Reply-To: <87k23cb6os.fsf@xmission.com> References: <1499785511-17192-1-git-send-email-stefanb@linux.vnet.ibm.com> <1499785511-17192-2-git-send-email-stefanb@linux.vnet.ibm.com> <87mv89iy7q.fsf@xmission.com> <20170712170346.GA17974@mail.hallyn.com> <877ezdgsey.fsf@xmission.com> <74664cc8-bc3e-75d6-5892-f8934404349f@linux.vnet.ibm.com> <20170713011554.xwmrgkzfwnibvgcu@thunk.org> <87y3rscz9j.fsf@xmission.com> <20170713164012.brj2flnkaaks2oci@thunk.org> <87k23cb6os.fsf@xmission.com> Message-ID: <847ccb2a-30c0-a94c-df6f-091c8901eaa0@linux.vnet.ibm.com> To: linux-security-module@vger.kernel.org List-Id: linux-security-module.vger.kernel.org On 07/13/2017 01:14 PM, Eric W. Biederman wrote: > Theodore Ts'o writes: > >> On Thu, Jul 13, 2017 at 07:11:36AM -0500, Eric W. Biederman wrote: >>> The concise summary: >>> >>> Today we have the xattr security.capable that holds a set of >>> capabilities that an application gains when executed. AKA setuid root exec >>> without actually being setuid root. >>> >>> User namespaces have the concept of capabilities that are not global but >>> are limited to their user namespace. We do not currently have >>> filesystem support for this concept. >> So correct me if I am wrong; in general, there will only be one >> variant of the form: >> >> security.foo at uid=15000 >> >> It's not like there will be: >> >> security.foo at uid=1000 >> security.foo at uid=2000 >> >> Except.... if you have an Distribution root directory which is shared >> by many containers, you would need to put the xattrs in the overlay >> inodes. Worse, each time you launch a new container, with a new >> subuid allocation, you will have to iterate over all files with >> capabilities and do a copy-up operations on the xattrs in overlayfs. >> So that's actually a bit of a disaster. >> >> So for distribution overlays, you will need to do things a different >> way, which is to map the distro subdirectory so you know that the >> capability with the global uid 0 should be used for the container >> "root" uid, right? >> >> So this hack of using security.foo at uid=1000 is *only* useful when the >> subcontainer root wants to create the privileged executable. You >> still have to do things the other way. >> >> So can we make perhaps the assertion that *either*: >> >> security.foo >> >> exists, *or* >> >> security.foo at uid=BAR >> >> exists, but never both? And there BAR is exclusive to only one >> instances? >> >> Otherwise, I suspect that the architecture is going to turn around and >> bite us in the *ss eventually, because someone will want to do >> something crazy and the solution will not be scalable. > Yep. That is what it looks like from here. > > Which is why I asked the question about scalability of the xattr > implementations. It looks like trying to accomodate the general > case just gets us in trouble, and sets unrealistic expectations. > > Which strongly suggests that Serge's previous version that > just reved the format of security.capable so that a uid field could > be added is likely to be the better approach. > > I want to see what Serge and Stefan have to say but the case looks > pretty clear cut at the moment. The approach of virtualizing the xattrs on the name-side, which is what this patch does, provides a more general approach than to virtualizing it on the value side, which is what Serge does in his other patch for security.capability alone. With the virtualizing on-the-value side virtualizing the xattr becomes an exercise that needs to be repeated for every xattr name that one would want to virtualize. With this patch you would just add another xattr name to a list, a one-line patch in the end. Xattr with prefixes like trusted.* need a bit more work but this can be woven in as well (https://github.com/stefanberger/linux/commit/397b1a3b24045c67405fc83465e544fc865d402f). For virtualizing the xattrs on the 'value' side I was looking for whether there's something like a 'wrapper' structure around the actual value of the xattr so that that wrapper could be extended to support different values at different uids and applied to any xattr. Unfortunately there's no such 'wrapper'. Stefan > > Eric > -- To unsubscribe from this list: send the line "unsubscribe linux-security-module" in the body of a message to majordomo at vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html From mboxrd@z Thu Jan 1 00:00:00 1970 Content-Type: multipart/mixed; boundary="===============0565230737530811197==" MIME-Version: 1.0 From: Stefan Berger To: lkp@lists.01.org Subject: Re: [PATCH v2] xattr: Enable security.capability in user namespaces Date: Thu, 13 Jul 2017 13:33:53 -0400 Message-ID: <847ccb2a-30c0-a94c-df6f-091c8901eaa0@linux.vnet.ibm.com> In-Reply-To: <87k23cb6os.fsf@xmission.com> List-Id: --===============0565230737530811197== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable On 07/13/2017 01:14 PM, Eric W. Biederman wrote: > Theodore Ts'o writes: > >> On Thu, Jul 13, 2017 at 07:11:36AM -0500, Eric W. Biederman wrote: >>> The concise summary: >>> >>> Today we have the xattr security.capable that holds a set of >>> capabilities that an application gains when executed. AKA setuid root = exec >>> without actually being setuid root. >>> >>> User namespaces have the concept of capabilities that are not global but >>> are limited to their user namespace. We do not currently have >>> filesystem support for this concept. >> So correct me if I am wrong; in general, there will only be one >> variant of the form: >> >> security.foo(a)uid=3D15000 >> >> It's not like there will be: >> >> security.foo(a)uid=3D1000 >> security.foo(a)uid=3D2000 >> >> Except.... if you have an Distribution root directory which is shared >> by many containers, you would need to put the xattrs in the overlay >> inodes. Worse, each time you launch a new container, with a new >> subuid allocation, you will have to iterate over all files with >> capabilities and do a copy-up operations on the xattrs in overlayfs. >> So that's actually a bit of a disaster. >> >> So for distribution overlays, you will need to do things a different >> way, which is to map the distro subdirectory so you know that the >> capability with the global uid 0 should be used for the container >> "root" uid, right? >> >> So this hack of using security.foo(a)uid=3D1000 is *only* useful when the >> subcontainer root wants to create the privileged executable. You >> still have to do things the other way. >> >> So can we make perhaps the assertion that *either*: >> >> security.foo >> >> exists, *or* >> >> security.foo(a)uid=3DBAR >> >> exists, but never both? And there BAR is exclusive to only one >> instances? >> >> Otherwise, I suspect that the architecture is going to turn around and >> bite us in the *ss eventually, because someone will want to do >> something crazy and the solution will not be scalable. > Yep. That is what it looks like from here. > > Which is why I asked the question about scalability of the xattr > implementations. It looks like trying to accomodate the general > case just gets us in trouble, and sets unrealistic expectations. > > Which strongly suggests that Serge's previous version that > just reved the format of security.capable so that a uid field could > be added is likely to be the better approach. > > I want to see what Serge and Stefan have to say but the case looks > pretty clear cut at the moment. The approach of virtualizing the xattrs on the name-side, which is what = this patch does, provides a more general approach than to virtualizing = it on the value side, which is what Serge does in his other patch for = security.capability alone. With the virtualizing on-the-value side = virtualizing the xattr becomes an exercise that needs to be repeated for = every xattr name that one would want to virtualize. With this patch you = would just add another xattr name to a list, a one-line patch in the = end. Xattr with prefixes like trusted.* need a bit more work but this = can be woven in as well = (https://github.com/stefanberger/linux/commit/397b1a3b24045c67405fc83465e54= 4fc865d402f). For virtualizing the xattrs on the 'value' side I was looking for = whether there's something like a 'wrapper' structure around the actual = value of the xattr so that that wrapper could be extended to support = different values at different uids and applied to any xattr. = Unfortunately there's no such 'wrapper'. Stefan > > Eric > --===============0565230737530811197==--