Hello,
On the system I'm using to get refpolicy working with Arch Linux, I have
these lines in audit.log:
type=AVC msg=audit(1451041210.334:794): avc: denied { read } for
pid=28829 comm="(ostnamed)" dev="nsfs" ino=4026532544
scontext=system_u:system_r:init_t
tcontext=system_u:object_r:unlabeled_t tclass=file permissive=1
type=AVC msg=audit(1451041210.334:794): avc: denied { open } for
pid=28829 comm="(ostnamed)" path="net:[4026532544]" dev="nsfs"
ino=4026532544 scontext=system_u:system_r:init_t
tcontext=system_u:object_r:unlabeled_t tclass=file permissive=1
These accesses are caused by open("/proc/self/ns/net"...) in systemd
setup_netns() function [1]. Indeed /proc/PID/ns/* symlinks target a
special filesystem named nsfs which is used for setns() syscall [2]. As
this filesystem is not defined in refpolicy, its files are currently
unlabeled, which explains the audit records.
To fix this, I see two options:
* "fs_use_task nsfs gen_context(system_u:object_r:fs_t,s0);", so that
programs already allowed to access the /proc/PID tree of a process can
also open /proc/PID/ns/* files.
* "genfscon nsfs / gen_context(system_u:object_r:nsfs_t,s0))", with a
new fs type. Programs using setns() will then need to be granted
opening and reading nsfs_t files, in addition to be allowed using
/proc/PID/ files of the target process.
To my mind both options have benefits and drawbacks, and I am fine with
both. If it matters, I have not found anything related to nsfs in
Fedora policy nor in Gentoo policy. The only policy I have found using
nsfs is https://github.com/doverride/cilpolicy/ and it uses the first
option [4].
Which option should be considered for refpolicy?
Thanks,
Nicolas
PS: if anyone wonders what is this init_t process with a pid which is
not one and a weird comm field, it is actually the process which will
become systemd-hostnamed. Its comm got modified by
rename_process_from_path() function [5].
[1] https://github.com/systemd/systemd/blob/v228/src/core/namespace.c#L682
[2] http://man7.org/linux/man-pages/man2/setns.2.html
[3]
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/fs/proc/namespaces.c?h=v4.3#n45
[4]
https://github.com/doverride/cilpolicy/blob/v0.1/sources/modules/base/fs/contexts.cil#L37
[5]
https://github.com/systemd/systemd/blob/v228/src/core/execute.c#L1003-L1032
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256
On Wed, Jan 06, 2016 at 07:37:10PM +0100, Nicolas Iooss wrote:
> Hello,
>
> On the system I'm using to get refpolicy working with Arch Linux, I have
> these lines in audit.log:
>
> type=AVC msg=audit(1451041210.334:794): avc: denied { read } for
> pid=28829 comm="(ostnamed)" dev="nsfs" ino=4026532544
> scontext=system_u:system_r:init_t
> tcontext=system_u:object_r:unlabeled_t tclass=file permissive=1
>
> type=AVC msg=audit(1451041210.334:794): avc: denied { open } for
> pid=28829 comm="(ostnamed)" path="net:[4026532544]" dev="nsfs"
> ino=4026532544 scontext=system_u:system_r:init_t
> tcontext=system_u:object_r:unlabeled_t tclass=file permissive=1
>
> These accesses are caused by open("/proc/self/ns/net"...) in systemd
> setup_netns() function [1]. Indeed /proc/PID/ns/* symlinks target a
> special filesystem named nsfs which is used for setns() syscall [2]. As
> this filesystem is not defined in refpolicy, its files are currently
> unlabeled, which explains the audit records.
>
> To fix this, I see two options:
>
> * "fs_use_task nsfs gen_context(system_u:object_r:fs_t,s0);", so that
> programs already allowed to access the /proc/PID tree of a process can
> also open /proc/PID/ns/* files.
>
> * "genfscon nsfs / gen_context(system_u:object_r:nsfs_t,s0))", with a
> new fs type. Programs using setns() will then need to be granted
> opening and reading nsfs_t files, in addition to be allowed using
> /proc/PID/ files of the target process.
Have you tried this option? I recall having tried it, and not getting
this to work.
>
> To my mind both options have benefits and drawbacks, and I am fine with
> both. If it matters, I have not found anything related to nsfs in
> Fedora policy nor in Gentoo policy. The only policy I have found using
> nsfs is https://github.com/doverride/cilpolicy/ and it uses the first
> option [4].
>
> Which option should be considered for refpolicy?
>
> Thanks,
> Nicolas
>
> PS: if anyone wonders what is this init_t process with a pid which is
> not one and a weird comm field, it is actually the process which will
> become systemd-hostnamed. Its comm got modified by
> rename_process_from_path() function [5].
>
> [1] https://github.com/systemd/systemd/blob/v228/src/core/namespace.c#L682
> [2] http://man7.org/linux/man-pages/man2/setns.2.html
> [3]
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/fs/proc/namespaces.c?h=v4.3#n45
> [4]
> https://github.com/doverride/cilpolicy/blob/v0.1/sources/modules/base/fs/contexts.cil#L37
> [5]
> https://github.com/systemd/systemd/blob/v228/src/core/execute.c#L1003-L1032
> _______________________________________________
> refpolicy mailing list
> refpolicy at oss.tresys.com
> http://oss.tresys.com/mailman/listinfo/refpolicy
- --
Key fingerprint = 5F4D 3CDB D3F8 3652 FBD8 02D5 3B6C 5F1D 2C7B 6B02
https://sks-keyservers.net/pks/lookup?op=get&search=0x3B6C5F1D2C7B6B02
Dominick Grift
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On Wed, Jan 06, 2016 at 07:44:28PM +0100, Dominick Grift wrote:
> On Wed, Jan 06, 2016 at 07:37:10PM +0100, Nicolas Iooss wrote:
> > Hello,
> >
> > On the system I'm using to get refpolicy working with Arch Linux, I have
> > these lines in audit.log:
> >
> > type=AVC msg=audit(1451041210.334:794): avc: denied { read } for
> > pid=28829 comm="(ostnamed)" dev="nsfs" ino=4026532544
> > scontext=system_u:system_r:init_t
> > tcontext=system_u:object_r:unlabeled_t tclass=file permissive=1
> >
> > type=AVC msg=audit(1451041210.334:794): avc: denied { open } for
> > pid=28829 comm="(ostnamed)" path="net:[4026532544]" dev="nsfs"
> > ino=4026532544 scontext=system_u:system_r:init_t
> > tcontext=system_u:object_r:unlabeled_t tclass=file permissive=1
> >
> > These accesses are caused by open("/proc/self/ns/net"...) in systemd
> > setup_netns() function [1]. Indeed /proc/PID/ns/* symlinks target a
> > special filesystem named nsfs which is used for setns() syscall [2]. As
> > this filesystem is not defined in refpolicy, its files are currently
> > unlabeled, which explains the audit records.
> >
> > To fix this, I see two options:
> >
> > * "fs_use_task nsfs gen_context(system_u:object_r:fs_t,s0);", so that
> > programs already allowed to access the /proc/PID tree of a process can
> > also open /proc/PID/ns/* files.
> >
> > * "genfscon nsfs / gen_context(system_u:object_r:nsfs_t,s0))", with a
> > new fs type. Programs using setns() will then need to be granted
> > opening and reading nsfs_t files, in addition to be allowed using
> > /proc/PID/ files of the target process.
>
> Have you tried this option? I recall having tried it, and not getting
> this to work.
>
> >
> > To my mind both options have benefits and drawbacks, and I am fine with
> > both. If it matters, I have not found anything related to nsfs in
> > Fedora policy nor in Gentoo policy. The only policy I have found using
> > nsfs is https://github.com/doverride/cilpolicy/ and it uses the first
> > option [4].
Yes and the superseding github.com/defensec/dssp
I ended up using fs_use_task
> >
> > Which option should be considered for refpolicy?
> >
> > Thanks,
> > Nicolas
> >
> > PS: if anyone wonders what is this init_t process with a pid which is
> > not one and a weird comm field, it is actually the process which will
> > become systemd-hostnamed. Its comm got modified by
> > rename_process_from_path() function [5].
> >
> > [1] https://github.com/systemd/systemd/blob/v228/src/core/namespace.c#L682
> > [2] http://man7.org/linux/man-pages/man2/setns.2.html
> > [3]
> > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/fs/proc/namespaces.c?h=v4.3#n45
> > [4]
> > https://github.com/doverride/cilpolicy/blob/v0.1/sources/modules/base/fs/contexts.cil#L37
> > [5]
> > https://github.com/systemd/systemd/blob/v228/src/core/execute.c#L1003-L1032
> > _______________________________________________
> > refpolicy mailing list
> > refpolicy at oss.tresys.com
> > http://oss.tresys.com/mailman/listinfo/refpolicy
>
> --
> Key fingerprint = 5F4D 3CDB D3F8 3652 FBD8 02D5 3B6C 5F1D 2C7B 6B02
> https://sks-keyservers.net/pks/lookup?op=get&search=0x3B6C5F1D2C7B6B02
> Dominick Grift
- --
Key fingerprint = 5F4D 3CDB D3F8 3652 FBD8 02D5 3B6C 5F1D 2C7B 6B02
https://sks-keyservers.net/pks/lookup?op=get&search=0x3B6C5F1D2C7B6B02
Dominick Grift
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On 01/06/2016 07:44 PM, Dominick Grift wrote:
> On Wed, Jan 06, 2016 at 07:37:10PM +0100, Nicolas Iooss wrote:
>> Hello,
>
>> On the system I'm using to get refpolicy working with Arch Linux, I have
>> these lines in audit.log:
>
>> type=AVC msg=audit(1451041210.334:794): avc: denied { read } for
>> pid=28829 comm="(ostnamed)" dev="nsfs" ino=4026532544
>> scontext=system_u:system_r:init_t
>> tcontext=system_u:object_r:unlabeled_t tclass=file permissive=1
>
>> type=AVC msg=audit(1451041210.334:794): avc: denied { open } for
>> pid=28829 comm="(ostnamed)" path="net:[4026532544]" dev="nsfs"
>> ino=4026532544 scontext=system_u:system_r:init_t
>> tcontext=system_u:object_r:unlabeled_t tclass=file permissive=1
>
>> These accesses are caused by open("/proc/self/ns/net"...) in systemd
>> setup_netns() function [1]. Indeed /proc/PID/ns/* symlinks target a
>> special filesystem named nsfs which is used for setns() syscall [2]. As
>> this filesystem is not defined in refpolicy, its files are currently
>> unlabeled, which explains the audit records.
>
>> To fix this, I see two options:
>
>> * "fs_use_task nsfs gen_context(system_u:object_r:fs_t,s0);", so that
>> programs already allowed to access the /proc/PID tree of a process can
>> also open /proc/PID/ns/* files.
>
>> * "genfscon nsfs / gen_context(system_u:object_r:nsfs_t,s0))", with a
>> new fs type. Programs using setns() will then need to be granted
>> opening and reading nsfs_t files, in addition to be allowed using
>> /proc/PID/ files of the target process.
>
> Have you tried this option? I recall having tried it, and not getting
> this to work.
Yes, in permissive mode only though. I first added this to
kernel/filesystem.te:
type nsfs_t;
fs_type(nsfs_t)
genfscon nsfs / gen_context(system_u:object_r:nsfs_t,s0)
Then (after rebooting) audit.log showed:
type=AVC msg=audit(1452106332.300:1811): avc: denied { read } for
pid=11125 comm="(ostnamed)" dev="nsfs" ino=4026532618
scontext=system_u:system_r:init_t tcontext=system_u:object_r:nsfs_t
tclass=file permissive=1
type=AVC msg=audit(1452106332.300:1811): avc: denied { open } for
pid=11125 comm="(ostnamed)" path="net:[4026532618]" dev="nsfs"
ino=4026532618 scontext=system_u:system_r:init_t
tcontext=system_u:object_r:nsfs_t tclass=file permissive=1
Adding the following lines to system/init.te in the
ifdef(`init_systemd') block made these messages disappear when running
"systemctl restart systemd-hostnamed.service":
optional_policy(`
gen_require(`
type nsfs_t;
')
allow init_t nsfs_t:file read_file_perms;
')
Could you please describe the problem you had, so that I can see if I
also have it?
Nicolas
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256
On Wed, Jan 06, 2016 at 08:42:37PM +0100, Nicolas Iooss wrote:
> On 01/06/2016 07:44 PM, Dominick Grift wrote:
> > On Wed, Jan 06, 2016 at 07:37:10PM +0100, Nicolas Iooss wrote:
> >> Hello,
> >
> >> On the system I'm using to get refpolicy working with Arch Linux, I have
> >> these lines in audit.log:
> >
> >> type=AVC msg=audit(1451041210.334:794): avc: denied { read } for
> >> pid=28829 comm="(ostnamed)" dev="nsfs" ino=4026532544
> >> scontext=system_u:system_r:init_t
> >> tcontext=system_u:object_r:unlabeled_t tclass=file permissive=1
> >
> >> type=AVC msg=audit(1451041210.334:794): avc: denied { open } for
> >> pid=28829 comm="(ostnamed)" path="net:[4026532544]" dev="nsfs"
> >> ino=4026532544 scontext=system_u:system_r:init_t
> >> tcontext=system_u:object_r:unlabeled_t tclass=file permissive=1
> >
> >> These accesses are caused by open("/proc/self/ns/net"...) in systemd
> >> setup_netns() function [1]. Indeed /proc/PID/ns/* symlinks target a
> >> special filesystem named nsfs which is used for setns() syscall [2]. As
> >> this filesystem is not defined in refpolicy, its files are currently
> >> unlabeled, which explains the audit records.
> >
> >> To fix this, I see two options:
> >
> >> * "fs_use_task nsfs gen_context(system_u:object_r:fs_t,s0);", so that
> >> programs already allowed to access the /proc/PID tree of a process can
> >> also open /proc/PID/ns/* files.
> >
> >> * "genfscon nsfs / gen_context(system_u:object_r:nsfs_t,s0))", with a
> >> new fs type. Programs using setns() will then need to be granted
> >> opening and reading nsfs_t files, in addition to be allowed using
> >> /proc/PID/ files of the target process.
> >
> > Have you tried this option? I recall having tried it, and not getting
> > this to work.
>
> Yes, in permissive mode only though. I first added this to
> kernel/filesystem.te:
>
> type nsfs_t;
> fs_type(nsfs_t)
> genfscon nsfs / gen_context(system_u:object_r:nsfs_t,s0)
>
> Then (after rebooting) audit.log showed:
>
> type=AVC msg=audit(1452106332.300:1811): avc: denied { read } for
> pid=11125 comm="(ostnamed)" dev="nsfs" ino=4026532618
> scontext=system_u:system_r:init_t tcontext=system_u:object_r:nsfs_t
> tclass=file permissive=1
> type=AVC msg=audit(1452106332.300:1811): avc: denied { open } for
> pid=11125 comm="(ostnamed)" path="net:[4026532618]" dev="nsfs"
> ino=4026532618 scontext=system_u:system_r:init_t
> tcontext=system_u:object_r:nsfs_t tclass=file permissive=1
>
> Adding the following lines to system/init.te in the
> ifdef(`init_systemd') block made these messages disappear when running
> "systemctl restart systemd-hostnamed.service":
>
> optional_policy(`
> gen_require(`
> type nsfs_t;
> ')
> allow init_t nsfs_t:file read_file_perms;
> ')
>
> Could you please describe the problem you had, so that I can see if I
> also have it?
The problem i had was that i was not seeing these "read" file
events. The AVC denials above prove me wrong. I must have overlooked
something.
>
> Nicolas
> _______________________________________________
> refpolicy mailing list
> refpolicy at oss.tresys.com
> http://oss.tresys.com/mailman/listinfo/refpolicy
- --
Key fingerprint = 5F4D 3CDB D3F8 3652 FBD8 02D5 3B6C 5F1D 2C7B 6B02
https://sks-keyservers.net/pks/lookup?op=get&search=0x3B6C5F1D2C7B6B02
Dominick Grift
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On Wed, Jan 06, 2016 at 08:42:37PM +0100, Nicolas Iooss wrote:
> On 01/06/2016 07:44 PM, Dominick Grift wrote:
> > On Wed, Jan 06, 2016 at 07:37:10PM +0100, Nicolas Iooss wrote:
> >> Hello,
> >
> >> On the system I'm using to get refpolicy working with Arch Linux, I have
> >> these lines in audit.log:
> >
> >> type=AVC msg=audit(1451041210.334:794): avc: denied { read } for
> >> pid=28829 comm="(ostnamed)" dev="nsfs" ino=4026532544
> >> scontext=system_u:system_r:init_t
> >> tcontext=system_u:object_r:unlabeled_t tclass=file permissive=1
> >
> >> type=AVC msg=audit(1451041210.334:794): avc: denied { open } for
> >> pid=28829 comm="(ostnamed)" path="net:[4026532544]" dev="nsfs"
> >> ino=4026532544 scontext=system_u:system_r:init_t
> >> tcontext=system_u:object_r:unlabeled_t tclass=file permissive=1
> >
> >> These accesses are caused by open("/proc/self/ns/net"...) in systemd
> >> setup_netns() function [1]. Indeed /proc/PID/ns/* symlinks target a
> >> special filesystem named nsfs which is used for setns() syscall [2]. As
> >> this filesystem is not defined in refpolicy, its files are currently
> >> unlabeled, which explains the audit records.
> >
> >> To fix this, I see two options:
> >
> >> * "fs_use_task nsfs gen_context(system_u:object_r:fs_t,s0);", so that
> >> programs already allowed to access the /proc/PID tree of a process can
> >> also open /proc/PID/ns/* files.
> >
> >> * "genfscon nsfs / gen_context(system_u:object_r:nsfs_t,s0))", with a
> >> new fs type. Programs using setns() will then need to be granted
> >> opening and reading nsfs_t files, in addition to be allowed using
> >> /proc/PID/ files of the target process.
> >
> > Have you tried this option? I recall having tried it, and not getting
> > this to work.
>
> Yes, in permissive mode only though. I first added this to
> kernel/filesystem.te:
>
> type nsfs_t;
> fs_type(nsfs_t)
> genfscon nsfs / gen_context(system_u:object_r:nsfs_t,s0)
>
> Then (after rebooting) audit.log showed:
>
> type=AVC msg=audit(1452106332.300:1811): avc: denied { read } for
> pid=11125 comm="(ostnamed)" dev="nsfs" ino=4026532618
> scontext=system_u:system_r:init_t tcontext=system_u:object_r:nsfs_t
> tclass=file permissive=1
> type=AVC msg=audit(1452106332.300:1811): avc: denied { open } for
> pid=11125 comm="(ostnamed)" path="net:[4026532618]" dev="nsfs"
> ino=4026532618 scontext=system_u:system_r:init_t
> tcontext=system_u:object_r:nsfs_t tclass=file permissive=1
>
> Adding the following lines to system/init.te in the
> ifdef(`init_systemd') block made these messages disappear when running
> "systemctl restart systemd-hostnamed.service":
>
> optional_policy(`
> gen_require(`
> type nsfs_t;
> ')
> allow init_t nsfs_t:file read_file_perms;
> ')
>
> Could you please describe the problem you had, so that I can see if I
> also have it?
>
> Nicolas
I wonder if the flexibility that fs_use_tasks provides is a real benefit
over the "all-or-nothing" genfscon.
If it ends up all-or-nothing anyway's then fs_use_task is way too
expensive, if not then fs_use_task adds some neat controls over who can
access what.
> _______________________________________________
> refpolicy mailing list
> refpolicy at oss.tresys.com
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Dominick Grift
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On Wed, Jan 06, 2016 at 08:47:22PM +0100, Dominick Grift wrote:
> On Wed, Jan 06, 2016 at 08:42:37PM +0100, Nicolas Iooss wrote:
> > On 01/06/2016 07:44 PM, Dominick Grift wrote:
> > > On Wed, Jan 06, 2016 at 07:37:10PM +0100, Nicolas Iooss wrote:
> > >> Hello,
> > >
> > >> On the system I'm using to get refpolicy working with Arch Linux, I have
> > >> these lines in audit.log:
> > >
> > >> type=AVC msg=audit(1451041210.334:794): avc: denied { read } for
> > >> pid=28829 comm="(ostnamed)" dev="nsfs" ino=4026532544
> > >> scontext=system_u:system_r:init_t
> > >> tcontext=system_u:object_r:unlabeled_t tclass=file permissive=1
> > >
> > >> type=AVC msg=audit(1451041210.334:794): avc: denied { open } for
> > >> pid=28829 comm="(ostnamed)" path="net:[4026532544]" dev="nsfs"
> > >> ino=4026532544 scontext=system_u:system_r:init_t
> > >> tcontext=system_u:object_r:unlabeled_t tclass=file permissive=1
> > >
> > >> These accesses are caused by open("/proc/self/ns/net"...) in systemd
> > >> setup_netns() function [1]. Indeed /proc/PID/ns/* symlinks target a
> > >> special filesystem named nsfs which is used for setns() syscall [2]. As
> > >> this filesystem is not defined in refpolicy, its files are currently
> > >> unlabeled, which explains the audit records.
> > >
> > >> To fix this, I see two options:
> > >
> > >> * "fs_use_task nsfs gen_context(system_u:object_r:fs_t,s0);", so that
> > >> programs already allowed to access the /proc/PID tree of a process can
> > >> also open /proc/PID/ns/* files.
> > >
> > >> * "genfscon nsfs / gen_context(system_u:object_r:nsfs_t,s0))", with a
> > >> new fs type. Programs using setns() will then need to be granted
> > >> opening and reading nsfs_t files, in addition to be allowed using
> > >> /proc/PID/ files of the target process.
> > >
> > > Have you tried this option? I recall having tried it, and not getting
> > > this to work.
> >
> > Yes, in permissive mode only though. I first added this to
> > kernel/filesystem.te:
> >
> > type nsfs_t;
> > fs_type(nsfs_t)
> > genfscon nsfs / gen_context(system_u:object_r:nsfs_t,s0)
> >
> > Then (after rebooting) audit.log showed:
> >
> > type=AVC msg=audit(1452106332.300:1811): avc: denied { read } for
> > pid=11125 comm="(ostnamed)" dev="nsfs" ino=4026532618
> > scontext=system_u:system_r:init_t tcontext=system_u:object_r:nsfs_t
> > tclass=file permissive=1
> > type=AVC msg=audit(1452106332.300:1811): avc: denied { open } for
> > pid=11125 comm="(ostnamed)" path="net:[4026532618]" dev="nsfs"
> > ino=4026532618 scontext=system_u:system_r:init_t
> > tcontext=system_u:object_r:nsfs_t tclass=file permissive=1
> >
> > Adding the following lines to system/init.te in the
> > ifdef(`init_systemd') block made these messages disappear when running
> > "systemctl restart systemd-hostnamed.service":
> >
> > optional_policy(`
> > gen_require(`
> > type nsfs_t;
> > ')
> > allow init_t nsfs_t:file read_file_perms;
> > ')
> >
> > Could you please describe the problem you had, so that I can see if I
> > also have it?
>
> The problem i had was that i was not seeing these "read" file
> events. The AVC denials above prove me wrong. I must have overlooked
> something.
I faced this issue with "machinectl login", as i recall i was unable to
log into the container with machinectl login $container using genfscon
(i was using fs_t instead of nsfs_t), and i was not seeing the read
events. This prompted me to try other things and what caused me to
end up with fs_use_task
>
> >
> > Nicolas
> > _______________________________________________
> > refpolicy mailing list
> > refpolicy at oss.tresys.com
> > http://oss.tresys.com/mailman/listinfo/refpolicy
>
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> Dominick Grift
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Dominick Grift
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