[PATCH] selinux-policy: update to version v2.0

[Dominick Grift]

Dominick Grift <dominick.grift at defensec.nl> writes:

> Stefan Hellermann <stefan at the2masters.de> writes:
>
>> Hi! Thank you for your really fast changes!
>
> Thank you for your feedback. It is appreciated. Comments below:
>
>>
>> With your last commit f86def7e there are 3 new errors for /dev/urandom:
>>
>> [...]
>> [    1.749370] init: - preinit -
>> [    2.437887] audit: type=1400 audit(1736810585.360:3): avc: denied 
>> { getattr } for  pid=886 comm="jshn" path="/dev/urandom" dev="tmpfs"
>> ino=31 scontext=sys.id:sys.role:jshn.subj
>> tcontext=sys.id:sys.role:random.nodedev tclass=chr_file permissive=1
>> [    2.438371] audit: type=1400 audit(1736810585.360:4): avc: denied 
>> { read } for  pid=886 comm="jshn" name="urandom" dev="tmpfs" ino=31
>> scontext=sys.id:sys.role:jshn.subj
>> tcontext=sys.id:sys.role:random.nodedev tclass=chr_file permissive=1
>> [    2.439138] audit: type=1400 audit(1736810585.360:5): avc: denied 
>> { open } for  pid=886 comm="jshn" path="/dev/urandom" dev="tmpfs"
>> ino=31 scontext=sys.id:sys.role:jshn.subj
>> tcontext=sys.id:sys.role:random.nodedev tclass=chr_file permissive=1
>> [    4.994969] random: crng init done
>> [...]
>
> I will add this.
>
>>
>> And I cannot login on ttyAMA0:
>>
>> Please press Enter to activate this console.
>>
>> login: can't get SID for root
>
> This is a bug in busybox-selinux. A fix for this was posted:
> http://lists.busybox.net/pipermail/busybox/2022-July/089800.html but it
> was never adopted. The aformentioned patch is tested and reviewed. It
> address this bug.
>
> Maybe OpenWrt can carry this patch or maybe someone with sway in the
> busybox community can figure out why it was not committed and get it
> in. I tried and failed. So unless something gets done this is going to
> linger on forever.
>
>>
>>
>> Login with ssh is ok. There is already a bug report for this, it's
>> working fine without selinux:
>> https://github.com/openwrt/openwrt/issues/17038
>
> Here is the fix:
> http://lists.busybox.net/pipermail/busybox/2022-July/089800.html
>
> I just needs to be applied.
>
>>
>>
>> After sysupgrade the "sysupgrade.tgz" error remains the same:
>>
>> [   12.155085] audit: type=1400 audit(1736811933.100:6): avc: denied 
>> { associate } for  pid=1006 comm="mv" name="sysupgrade.tgz"
>> scontext=sys.id:sys.role:dos.fs tcontext=sys.id:sys.role:xattr.fs
>> tclass=filesystem permissive=1
>>
>
> This is not something I can fix in the policy. Whatever does this needs
> to be asked not to and to use cp instead of mv. Fortunately this does
> not happen in a stock system because it involves fat.
>
>>
>> And while doing sysupgrade from a local file in /tmp I get a bunch
>> more (no luci here, just scp file to /tmp and start sysupgrade from
>> ssh):

I added limited support for scp -O with firmware images and
backups. Untested but the pre-requisite for this to work is that that
you scp -O the files with the names specified in the commit:

https://git.defensec.nl/?p=selinux-policy.git;a=commitdiff;h=20cd42a573762ada41077c91fd14ad77c6aac6f3

Still, my advice is to move away from scp -O. Its a dead end.

>
> Its comlicated and theres quite a bit involved but let me touch on some
> of it:
>
> Youre using scp -O. This is legacy scp and it should be killed. If you
> dont want to install the openssh-sftp-server package then use:
>
> `cat openwrt-armsr-armv8-generic-squashfs-combined.img.gz | ssh
> root at 192.168.1.1 "cat > /tmp/sysupgrade.img"`
>
> dropbear uses /tmp to generate its hostkey and the way it does it is
> selinux unfriendly. It means that if you use scp -O and you transfer a
> file to /tmp that it ends up with the ssh hostkey label because usually
> dropbear creates its hostkey in /tmp and then it moves it to
> /etc/dropbear (again that stupid mv issue). Anyway I had to make do but
> the gist is this: don't use scp -O. its dead and it needs to be burried.
>
> I was expecting this and I documented it in the README and I will also
> document it elsewhere. I will also think about this some more but I kind
> of like this implementation so far. Anyway:
>
> Youve scp'd the file as-is (with name
> openwrt-armsr-armv8-generic-squashfs-combined.img.gz) and this caused
> the file to be copied with a context that validate-firmware-image cannot
> validate (read).
>
> The solution is to either use LuCI (I worked on it yesterday) or to scp
> the file with one of these names: firmware.bin sysupgrade.img
> sysupgrade.bin. for example:
>
> cat openwrt-ipq40xx-generic-linksys_mr8300-squashfs-sysupgrade.bin | ssh
> root at openwrt "cat > /tmp/sysupgrade.bin"
>
> I know its a bit fragile but I kind of like it and Luci and sysupgrade
> https://... both do something like that so I figured that if i would
> just clearly document this requirement it would be fine
>
> https://git.defensec.nl/?p=selinux-policy.git;a=blob;f=src/file/tmpfile/sysupgradetmpfile.cil;h=325e12c7a4d014ca7ee1af6786d00b532846dac7;hb=HEAD
>
> Long story short:
> 1. don't use scp -O
> 2. if you use openssh-sftp-server (scp without -O) then make sure that
> you transfer the image as either firmware.bin, sysupgrade.bin or sysupgrade.img
> 3. if you just use plain `ssh` in a pipe (example) then you get full access so
> that is the most flexible way to use ssh (and you dont need
> openssh-sftp-server for it either).
> 4. you can also use sysupgrade online if you have a local webserver:
>
> root at OpenWrt:~# getenforce && sysupgrade -v --test
> http://192.168.1.192/~kcinimod/stuff/openwrt-ipq40xx-generic-linksys_mr8300-squashfs-sysupgrade.bin
> Enforcing
> Downloading 'http://192.168.1.192/~kcinimod/stuff/openwrt-ipq40xx-generic-linksys_mr8300-squashfs-sysupgrade.bin'
> Connecting to 192.168.1.192:80
> Writing to '/tmp/sysupgrade.img'
> /tmp/sysupgrade.img  100% |*******************************| 13111k  0:00:00 ETA
> Download completed (13426016 bytes)
> root at OpenWrt:~# echo $?
> 0
>
> Yes, quite a bit to digest any I will consider supporting firmware
> images with random names but eventually it is still fragile when people
> try to use scp -O ...
>
>>
>> [   74.345700] audit: type=1400 audit(1736811834.460:6): avc: denied 
>> { read write } for  pid=2854 comm="fwtool"
>> name="openwrt-armsr-armv8-generic-squashfs-combined.img.gz"
>> dev="tmpfs" ino=93 scontext=sys.id:sys.role:fwtool.subj
>> tcontext=sys.id:sys.role:ssh.server.hostkey.file tclass=file
>> permissive=1
>> [   74.347589] audit: type=1400 audit(1736811834.460:7): avc: denied 
>> { open } for  pid=2854 comm="fwtool"
>> path="/tmp/openwrt-armsr-armv8-generic-squashfs-combined.img.gz"
>> dev="tmpfs" ino=93 scontext=sys.id:sys.role:fwtool.subj
>> tcontext=sys.id:sys.role:ssh.server.hostkey.file tclass=file
>> permissive=1
>> [   74.349106] audit: type=1400 audit(1736811834.460:8): avc: denied 
>> { ioctl } for  pid=2854 comm="fwtool"
>> path="/tmp/openwrt-armsr-armv8-generic-squashfs-combined.img.gz"
>> dev="tmpfs" ino=93 ioctlcmd=0x5413
>> scontext=sys.id:sys.role:fwtool.subj
>> tcontext=sys.id:sys.role:ssh.server.hostkey.file tclass=file
>> permissive=1
>> [   74.770422] audit: type=1400 audit(1736811834.890:9): avc: denied 
>> { read } for  pid=2864 comm="cat" name="cmdline" dev="proc"
>> ino=4026531972 scontext=sys.id:sys.role:validatefirmwareimage.subj
>> tcontext=sys.id:sys.role:cmdline.procfile tclass=file permissive=1
>> [   74.771728] audit: type=1400 audit(1736811834.890:10): avc: denied 
>> { open } for  pid=2864 comm="cat" path="/proc/cmdline" dev="proc"
>> ino=4026531972 scontext=sys.id:sys.role:validatefirmwareimage.subj
>> tcontext=sys.id:sys.role:cmdline.procfile tclass=file permissive=1
>> [   74.800695] audit: type=1400 audit(1736811834.920:11): avc: denied 
>> { read } for  pid=2865 comm="find" name="/" dev="tmpfs" ino=1
>> scontext=sys.id:sys.role:validatefirmwareimage.subj
>> tcontext=sys.id:sys.role:tmp.fs tclass=dir permissive=1
>> [   74.801449] audit: type=1400 audit(1736811834.920:12): avc: denied 
>> { open } for  pid=2865 comm="find" path="/dev" dev="tmpfs" ino=1
>> scontext=sys.id:sys.role:validatefirmwareimage.subj
>> tcontext=sys.id:sys.role:tmp.fs tclass=dir permissive=1
>> [   74.807108] audit: type=1400 audit(1736811834.930:13): avc: denied 
>> { getattr } for  pid=2865 comm="find" path="/dev/pts" dev="devpts"
>> ino=1 scontext=sys.id:sys.role:validatefirmwareimage.subj
>> tcontext=sys.id:sys.role:devpts.fs tclass=dir permissive=1
>> [   74.807988] audit: type=1400 audit(1736811834.930:14): avc: denied 
>> { read } for  pid=2865 comm="find" name="/" dev="devpts" ino=1
>> scontext=sys.id:sys.role:validatefirmwareimage.subj
>> tcontext=sys.id:sys.role:devpts.fs tclass=dir permissive=1
>> [   74.808726] audit: type=1400 audit(1736811834.930:15): avc: denied 
>> { open } for  pid=2865 comm="find" path="/dev/pts" dev="devpts" ino=1
>> scontext=sys.id:sys.role:validatefirmwareimage.subj
>> tcontext=sys.id:sys.role:devpts.fs tclass=dir permissive=1
>> [   80.140951] kauditd_printk_skb: 35 callbacks suppressed
>> [   80.140985] audit: type=1400 audit(1736811840.260:51): avc: denied 
>> { remove_name } for  pid=3459 comm="rm" name="image.bs" dev="tmpfs"
>> ino=96 scontext=sys.id:sys.role:validatefirmwareimage.subj
>> tcontext=sys.id:sys.role:tmp.fs tclass=dir permissive=1
>> [   80.141666] audit: type=1400 audit(1736811840.260:52): avc: denied 
>> { unlink } for  pid=3459 comm="rm" name="image.bs" dev="tmpfs" ino=96
>> scontext=sys.id:sys.role:validatefirmwareimage.subj
>> tcontext=sys.id:sys.role:tmp.fs tclass=file permissive=1
>> [   87.255570] audit: type=1400 audit(1736811847.370:53): avc: denied 
>> { getattr } for  pid=3955 comm="find" path="/dev/hwrng" dev="tmpfs"
>> ino=14 scontext=sys.id:sys.role:validatefirmwareimage.subj
>> tcontext=sys.id:sys.role:hwrng.nodedev tclass=chr_file permissive=1
>
> I will look into adding rules for some of these validate-firmware-image
> related events. Not sure what is happening there with "image.bs" ...
>
> Thanks
>
>>
>> This is all done on a fresh openwrt checkout, I added your selinux
>> updates and build the image with this config:
>>
>> CONFIG_TARGET_armsr=y
>> CONFIG_TARGET_armsr_armv8=y
>> CONFIG_TARGET_armsr_armv8_DEVICE_generic=y
>> CONFIG_PACKAGE_qemu-ga=y
>> CONFIG_SELINUX=y
>>
>> I can send you the compressed image file, if you want to try it
>> yourself with qemu/virt-manager.
>
> No thanks. All the events you pasted above are either normal rough edges
> or issues that I am aware of but that are only documented in my
> policy/repository. Eventually I am going to write a wiki page that
> summarizes all the "gotches".
>
> Thanks!
>
>>
>> Regards,
>> Stefan Hellermann
>>
>>
>> Am 13.01.25 um 18:52 schrieb Dominick Grift:
>>> Dominick Grift <dominick.grift at defensec.nl> writes:
>>>
>>>> Dominick Grift <dominick.grift at defensec.nl> writes:
>>>>
>>>>> Hi, Thank you for feedback. Comments inline below:
>>>>>
>>>>> Stefan Hellermann <stefan at the2masters.de> writes:
>>>>>
>>>> <snip>
>>>>
>>>>>> audit(1736704702.290:4): avc:  denied  { associate } for  pid=1010
>>>>>> comm="mv" name="sysupgrade.tgz" scontext=sys.id:sys.role:dos.fs
>>>>>> tcontext=sys.id:sys.role:xattr.fs tclass=filesystem permissive=1
>>>>> This is caused by mv'ing the file from a fat filesystem (fat does not
>>>>> support extended attributes) to an extended attribute file system. When
>>>>> you mv a file you also mv its associated context with it.
>>>>>
>>>>> This should not be allowed. Instead you should use cp. mv does not make
>>>>> much sense anyway cross filesystem.
>>>>>
>>>> This bothered me so I would like to explain why I object to this.
>>>>
>>>> mv and cp are more complicated than some think. I see this all the time
>>>> where people for example use `cp -a` without realizing the consequences.
>>>>
>>>> But regardless of this, coreutils has extensive support for SELinux and
>>>> `mv -Z` would have addressed the above challenge. The issue is that
>>>> busybox' `mv` does not support -Z and so eventually I will have to draw
>>>> the line somewhere anyway. This seems like a good place to start.
>>>>
>>>>>> Sun Jan 12 17:58:25 2025 user.warn kernel: urandom-seed: Seed file not
>>>>>> found (/etc/urandom.seed)
>>>>>> Sun Jan 12 17:58:25 2025 user.info kernel: procd: - early -
>>>>>> Sun Jan 12 17:58:25 2025 kern.notice kernel: audit: type=1400
>>>>>> audit(1736704702.590:5): avc:  denied  { write } for  pid=1166
>>>>>> comm="mkdir" name="/" dev="tmpfs" ino=1
>>>>>> scontext=sys.id:sys.role:hotplug.call.subj
>>>>>> tcontext=sys.id:sys.role:tmp.fs tclass=dir permissive=1
>>>>>> Sun Jan 12 17:58:25 2025 kern.notice kernel: audit: type=1400
>>>>>> audit(1736704702.590:6): avc:  denied  { add_name } for  pid=1166
>>>>>> comm="mkdir" name="virtio-ports"
>>>>>> scontext=sys.id:sys.role:hotplug.call.subj
>>>>>> tcontext=sys.id:sys.role:tmp.fs tclass=dir permissive=1
>>>>>> Sun Jan 12 17:58:25 2025 kern.notice kernel: audit: type=1400
>>>>>> audit(1736704702.590:7): avc:  denied  { create } for  pid=1166
>>>>>> comm="mkdir" name="virtio-ports"
>>>>>> scontext=sys.id:sys.role:hotplug.call.subj
>>>>>> tcontext=sys.id:sys.role:tmp.fs tclass=dir permissive=1
>>>>>> Sun Jan 12 17:58:25 2025 kern.notice kernel: audit: type=1400
>>>>>> audit(1736704702.590:8): avc:  denied  { create } for  pid=1167
>>>>>> comm="ln" name="org.qemu.guest_agent.0"
>>>>>> scontext=sys.id:sys.role:hotplug.call.subj
>>>>>> tcontext=sys.id:sys.role:tmp.fs tclass=lnk_file permissive=1
>>>>>> Sun Jan 12 17:58:25 2025 user.info kernel: procd: - ubus -
>>>>>> Sun Jan 12 17:58:25 2025 user.info kernel: procd: - init -
>>> I added support for this. We'll see where this leads. I might end up
>>> reverting it later.
>>>
>>> https://git.defensec.nl/?p=selinux-policy.git;a=commitdiff;h=32c0cc897f679b6d2b204bc2935d9de3b7006944
>>>
>>>>> This seems like an 'exotic hotplug script'. I have an accomodation for
>>>>> this. see if this comment helps:
>>>>> https://git.defensec.nl/?p=selinux-policy.git;a=blob;f=src/agent/sysagent/hotplugsysagent.cil;h=3987b8540ae537d174a74cceb2c89ce26ef3c813;hb=HEAD#l115
>>>> We'll have to see how this will work out practically. I am open to
>>>> suggestions for alternative approaches but this seems like a fair
>>>> approach.
>>>>
>>>> There are also challenges here. For example in the above event, the
>>>> script is trying to create a dir and symlink in /dev. In OpenWrt there
>>>> is no (easy) way to make a distinction between devtmpfs and and a common
>>>> tmpfs. If I we're to allow this then that would later potentially
>>>> present challenges when another script wants to create a dir or symlink in /tmp.
>>>>
>>>> Again, eventually I would have to draw the line somewhere as to what
>>>> should be allowed by default and what is to be considered exotic. This
>>>> looks like a good place.
>>>>
>>>> Just trying to explain some of the rationale because I am open to better
>>>> alternatives. I just don't see any.
>>

-- 
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Dominick Grift
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