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[209.85.219.176]) by smtp.gmail.com with ESMTPSA id v11-v6sm1429999ywb.13.2018.09.13.08.19.05 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 13 Sep 2018 08:19:05 -0700 (PDT) Received: by mail-yb1-f176.google.com with SMTP id y20-v6so3388904ybi.13 for ; Thu, 13 Sep 2018 08:19:05 -0700 (PDT) X-Received: by 2002:a25:f606:: with SMTP id t6-v6mr3786461ybd.141.1536851944587; Thu, 13 Sep 2018 08:19:04 -0700 (PDT) MIME-Version: 1.0 Received: by 2002:a25:5f04:0:0:0:0:0 with HTTP; Thu, 13 Sep 2018 08:19:03 -0700 (PDT) In-Reply-To: References: <99cb1ae7-8881-eb9a-a8cb-a787abe454e1@schaufler-ca.com> From: Kees Cook Date: Thu, 13 Sep 2018 08:19:03 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 10/10] LSM: Blob sharing support for S.A.R.A and LandLock To: Paul Moore Cc: Casey Schaufler , linux-security-module , James Morris , LKML , SE Linux , John Johansen , Tetsuo Handa , Stephen Smalley , "linux-fsdevel@vger.kernel.org" , Alexey Dobriyan , "Schaufler, Casey" Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 13, 2018 at 6:16 AM, Paul Moore wrote: > On Thu, Sep 13, 2018 at 12:19 AM Kees Cook wrote: >> On Tue, Sep 11, 2018 at 9:42 AM, Casey Schaufler wrote: >> > Two proposed security modules require the ability to >> > share security blobs with existing "major" security modules. >> > These modules, S.A.R.A and LandLock, provide significantly >> > different services than SELinux, Smack or AppArmor. Using >> > either in conjunction with the existing modules is quite >> > reasonable. S.A.R.A requires access to the cred blob, while >> > LandLock uses the cred, file and inode blobs. >> > >> > The use of the cred, file and inode blobs has been >> > abstracted in preceding patches in the series. This >> > patch teaches the affected security modules how to access >> > the part of the blob set aside for their use in the case >> > where blobs are shared. The configuration option >> > CONFIG_SECURITY_STACKING identifies systems where the >> > blobs may be shared. >> > >> > The mechanism for selecting which security modules are >> > active has been changed to allow non-conflicting "major" >> > security modules to be used together. At this time the >> > TOMOYO module can safely be used with any of the others. >> > The two new modules would be non-conflicting as well. >> > >> > Signed-off-by: Casey Schaufler >> > --- >> > Documentation/admin-guide/LSM/index.rst | 14 +++-- >> > include/linux/lsm_hooks.h | 2 +- >> > security/Kconfig | 81 +++++++++++++++++++++++++ >> > security/apparmor/include/cred.h | 8 +++ >> > security/apparmor/include/file.h | 9 ++- >> > security/apparmor/include/lib.h | 4 ++ >> > security/apparmor/lsm.c | 8 ++- >> > security/security.c | 30 ++++++++- >> > security/selinux/hooks.c | 3 +- >> > security/selinux/include/objsec.h | 18 +++++- >> > security/smack/smack.h | 19 +++++- >> > security/smack/smack_lsm.c | 17 +++--- >> > security/tomoyo/common.h | 12 +++- >> > security/tomoyo/tomoyo.c | 3 +- >> > 14 files changed, 200 insertions(+), 28 deletions(-) > > ... > >> > diff --git a/security/Kconfig b/security/Kconfig >> > index 22f7664c4977..ed48025ae9e0 100644 >> > --- a/security/Kconfig >> > +++ b/security/Kconfig >> > @@ -36,6 +36,28 @@ config SECURITY_WRITABLE_HOOKS >> > bool >> > default n >> > >> > +config SECURITY_STACKING >> > + bool "Security module stacking" >> > + depends on SECURITY >> > + help >> > + Allows multiple major security modules to be stacked. >> > + Modules are invoked in the order registered with a >> > + "bail on fail" policy, in which the infrastructure >> > + will stop processing once a denial is detected. Not >> > + all modules can be stacked. SELinux, Smack and AppArmor are >> > + known to be incompatible. User space components may >> > + have trouble identifying the security module providing >> > + data in some cases. >> > + >> > + If you select this option you will have to select which >> > + of the stackable modules you wish to be active. The >> > + "Default security module" will be ignored. The boot line >> > + "security=" option can be used to specify that one of >> > + the modules identifed for stacking should be used instead >> > + of the entire stack. >> > + >> > + If you are unsure how to answer this question, answer N. >> >> I don't see a good reason to make this a config. Why shouldn't this >> always be enabled? > > I do. From a user perspective it is sometimes difficult to determine > the reason behind a failed operation; its is a DAC based denial, the > LSM, or some other failure? Stacking additional LSMs has the > potential to make this worse. The boot time configuration adds to the > complexity. Let me try to convince you otherwise. :) The reason I think there's no need for this is because the only functional change here is how _TOMOYO_ gets stacked. And in my proposal, we can convert TOMOYO to be enabled/disabled like LoadPin. Given the configs I showed, stacking TOMOYO with the other major LSMs becomes a config (and/or boottime) option. The changes for TOMOYO are still needed even _with_ SECURITY_STACKING, and I argue that the other major LSMs remain the same. It's only infrastructure that has changed. So, I think having SECURITY_STACKING actually makes things more complex internally (all the ifdefs, weird enable logic) and for distros ("what's this stacking option", etc?) > I think we should leave this decision to the individual distros so > that they can make their own decision on LSM stacking based on the > savviness of their user base and the quality of their support > infrastructure. If we reach the "extreme" stacking case, then yes, I want to make sure we've got something that makes sense. But this first step doesn't get us there, so I'd prefer we avoid making it overly complex. I think everything else in this series _reduces_ complexity, except for this new config. -Kees -- Kees Cook Pixel Security From mboxrd@z Thu Jan 1 00:00:00 1970 From: keescook@chromium.org (Kees Cook) Date: Thu, 13 Sep 2018 08:19:03 -0700 Subject: [PATCH 10/10] LSM: Blob sharing support for S.A.R.A and LandLock In-Reply-To: References: <99cb1ae7-8881-eb9a-a8cb-a787abe454e1@schaufler-ca.com> Message-ID: To: linux-security-module@vger.kernel.org List-Id: linux-security-module.vger.kernel.org On Thu, Sep 13, 2018 at 6:16 AM, Paul Moore wrote: > On Thu, Sep 13, 2018 at 12:19 AM Kees Cook wrote: >> On Tue, Sep 11, 2018 at 9:42 AM, Casey Schaufler wrote: >> > Two proposed security modules require the ability to >> > share security blobs with existing "major" security modules. >> > These modules, S.A.R.A and LandLock, provide significantly >> > different services than SELinux, Smack or AppArmor. Using >> > either in conjunction with the existing modules is quite >> > reasonable. S.A.R.A requires access to the cred blob, while >> > LandLock uses the cred, file and inode blobs. >> > >> > The use of the cred, file and inode blobs has been >> > abstracted in preceding patches in the series. This >> > patch teaches the affected security modules how to access >> > the part of the blob set aside for their use in the case >> > where blobs are shared. The configuration option >> > CONFIG_SECURITY_STACKING identifies systems where the >> > blobs may be shared. >> > >> > The mechanism for selecting which security modules are >> > active has been changed to allow non-conflicting "major" >> > security modules to be used together. At this time the >> > TOMOYO module can safely be used with any of the others. >> > The two new modules would be non-conflicting as well. >> > >> > Signed-off-by: Casey Schaufler >> > --- >> > Documentation/admin-guide/LSM/index.rst | 14 +++-- >> > include/linux/lsm_hooks.h | 2 +- >> > security/Kconfig | 81 +++++++++++++++++++++++++ >> > security/apparmor/include/cred.h | 8 +++ >> > security/apparmor/include/file.h | 9 ++- >> > security/apparmor/include/lib.h | 4 ++ >> > security/apparmor/lsm.c | 8 ++- >> > security/security.c | 30 ++++++++- >> > security/selinux/hooks.c | 3 +- >> > security/selinux/include/objsec.h | 18 +++++- >> > security/smack/smack.h | 19 +++++- >> > security/smack/smack_lsm.c | 17 +++--- >> > security/tomoyo/common.h | 12 +++- >> > security/tomoyo/tomoyo.c | 3 +- >> > 14 files changed, 200 insertions(+), 28 deletions(-) > > ... > >> > diff --git a/security/Kconfig b/security/Kconfig >> > index 22f7664c4977..ed48025ae9e0 100644 >> > --- a/security/Kconfig >> > +++ b/security/Kconfig >> > @@ -36,6 +36,28 @@ config SECURITY_WRITABLE_HOOKS >> > bool >> > default n >> > >> > +config SECURITY_STACKING >> > + bool "Security module stacking" >> > + depends on SECURITY >> > + help >> > + Allows multiple major security modules to be stacked. >> > + Modules are invoked in the order registered with a >> > + "bail on fail" policy, in which the infrastructure >> > + will stop processing once a denial is detected. Not >> > + all modules can be stacked. SELinux, Smack and AppArmor are >> > + known to be incompatible. User space components may >> > + have trouble identifying the security module providing >> > + data in some cases. >> > + >> > + If you select this option you will have to select which >> > + of the stackable modules you wish to be active. The >> > + "Default security module" will be ignored. The boot line >> > + "security=" option can be used to specify that one of >> > + the modules identifed for stacking should be used instead >> > + of the entire stack. >> > + >> > + If you are unsure how to answer this question, answer N. >> >> I don't see a good reason to make this a config. Why shouldn't this >> always be enabled? > > I do. From a user perspective it is sometimes difficult to determine > the reason behind a failed operation; its is a DAC based denial, the > LSM, or some other failure? Stacking additional LSMs has the > potential to make this worse. The boot time configuration adds to the > complexity. Let me try to convince you otherwise. :) The reason I think there's no need for this is because the only functional change here is how _TOMOYO_ gets stacked. And in my proposal, we can convert TOMOYO to be enabled/disabled like LoadPin. Given the configs I showed, stacking TOMOYO with the other major LSMs becomes a config (and/or boottime) option. The changes for TOMOYO are still needed even _with_ SECURITY_STACKING, and I argue that the other major LSMs remain the same. It's only infrastructure that has changed. So, I think having SECURITY_STACKING actually makes things more complex internally (all the ifdefs, weird enable logic) and for distros ("what's this stacking option", etc?) > I think we should leave this decision to the individual distros so > that they can make their own decision on LSM stacking based on the > savviness of their user base and the quality of their support > infrastructure. If we reach the "extreme" stacking case, then yes, I want to make sure we've got something that makes sense. But this first step doesn't get us there, so I'd prefer we avoid making it overly complex. I think everything else in this series _reduces_ complexity, except for this new config. -Kees -- Kees Cook Pixel Security