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Date: Tue, 13 Sep 2022 09:37:29 +0200
From: Fabian =?iso-8859-1?q?Gr=FCnbichler?= <f.gruenbichler@proxmox.com>
To: Leo Nunner <l.nunner@proxmox.com>, Proxmox VE development discussion
<pve-devel@lists.proxmox.com>, Thomas Lamprecht <t.lamprecht@proxmox.com>
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Subject: Re: [pve-devel] [PATCH v2 container] fix #4192: revamp check for
systemd version
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On September 12, 2022 4:01 pm, Thomas Lamprecht wrote:
> Am 12/09/2022 um 14:41 schrieb Fabian Gr=C3=BCnbichler:
>>> Instead of iterating through several folders, it might just be easier t=
o
>>> check the ldd output of /sbin/init and getting the version from there.
>>> Furthermore, the regex for checking the version has been adapted so tha=
t
>>> it's more precise.
>> ldd is not suited for this purpose for security reasons, since /sbin/ini=
t=20
>> is a user/attacker-controlled binary in this case and we are only in a=20
>> chroot while doing the setup, not really containerized. given a crafted=20
>> container template/backup archive/.. this could execute arbitrary code.
>>=20
>> it's manpage suggests using
>>=20
>> objdump -p /path/to/binary
>>=20
>> and looking at the lines with "NEEDED", which seems to me should be fine=
=20
>> for what we want to achieve here =F0=9F=98=84
>>=20
>=20
> tbf, I suggested using something like ldd here, but I mostly meant if we =
actually
> need to further extend this than simply checking three instead of two pat=
hs.
>=20
> But I actually like the much shorter code, so from that POV it could be a=
nicer
> option, but it makes us dependent on actually executing code from the CT =
archive,
> which also assumes the availability of something like ldd or objdump, whi=
ch may
> not be the case in all templates?
yeah, objdump from the host would need to be used (else we'd be back to=20
square one and execute code from the container template/backup=20
archive/.. without adequate protection). probably needs additional=20
safeguards like resolving /sbin/init from the system with checks to=20
prevent escape from the container /.
> Two small nits w.r.t. to the v2 still inline.
>=20
> Am 12/09/2022 um 14:25 schrieb Leo Nunner:
>> + my $version =3D undef;
>> + PVE::Tools::run_command(
>> + [
>> + 'ldd',
>> + '/sbin/init'
>> + ],
>=20
> you can put the array ref in one line, e.g., with Fabian relayed manpage
> suggestion it'd be fine to do:
>=20
> [ 'objdump', '-p', '/sbin/init' ],
see above ;) the whole thing would need to be revamped to no longer=20
happen in "protected_call" context, but instead in host context without=20
chroot, except for the symlink resolve part. at that point it might not=20
be nicer anymoe than the original approach of checking a few paths,=20
although it would have the benefit of being much more future-proof=20
w.r.t. distros/upstream/.. deciding on new funny places to put that=20
library ;)
>> + outfunc =3D> sub {
>> + my $line =3D shift;
>> + if ($line =3D~ /^\s*libsystemd-shared-(\d+)(?:\.[a-zA-Z0-9]*)?\.so=
/) {
>> + $version =3D $1;
>> + }},
>> + errmsg =3D> "ldd on /sbin/init failed"
>=20
> above is missing a trailing comma, which would ensure that any possible a=
ddition of an
> option in the future won't need to touch an unrelated line.
>=20
>> + );
>> +
>> + return $version;
>> }
>=20
>=20