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Date: Tue, 28 Mar 2023 15:27:39 +0200
From: Fabian =?iso-8859-1?q?Gr=FCnbichler?= <f.gruenbichler@proxmox.com>
To: Proxmox VE development discussion <pve-devel@lists.proxmox.com>
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Subject: Re: [pve-devel] [PATCH pve-storage 2/2] change regex to allow
subdirs
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On March 3, 2023 3:50 pm, Noel Ullreich wrote:
> change the regex in `parse_volname` and `get_subdir_files` to allow
> subdirectories.
>=20
> Signed-off-by: Noel Ullreich <n.ullreich@proxmox.com>
> ---
> PVE/Storage/Plugin.pm | 14 +++++++-------
> 1 file changed, 7 insertions(+), 7 deletions(-)
>=20
> diff --git a/PVE/Storage/Plugin.pm b/PVE/Storage/Plugin.pm
> index bf1d564..e8b2b95 100644
> --- a/PVE/Storage/Plugin.pm
> +++ b/PVE/Storage/Plugin.pm
> @@ -620,9 +620,9 @@ sub parse_volname {
> my ($vmid, $name) =3D ($1, $2);
> my (undef, $format, $isBase) =3D parse_name_dir($name);
> return ('images', $name, $vmid, undef, undef, $isBase, $format);
> - } elsif ($volname =3D~ m!^iso/([^/]+$PVE::Storage::ISO_EXT_RE_0)$!) =
{
> + } elsif ($volname =3D~ m!^iso/(.+$PVE::Storage::ISO_EXT_RE_0)$!) {
so this needs to forbid at least '..', else the following is possible
1. place symlink to sensitive, root-only host file somewhere writable by a =
user
(e.g., container volume on ZFS which has a host-visible mount point by defa=
ult,
but also something like an arbitrary container volume and tricking an admin=
into
running `pct mount` would work, or possible other similar scenarios)
2. qm set XXX -ide2 $storage:iso/../../../path/to/symlink,medium=3Dcdrom
3. (in VM) cat /dev/sr0
I am not sure whether that's the only thing that's bad, it might make sense=
to
start with a restricted set of allowed characters for the dirs in-between a=
nd
extend that as needed after evaluating.. if that route is taken, it obvious=
ly
also should be done for patch #1 to be consistent ;)
it might also make sense to limit the nesting here and in patch #1, and/or =
limit
the length of the resulting volume ID?
one problem we have here is that we only operate on a volume ID (or in sub =
path,
on a "hypothetical" path) so it's a bit hard to guard against certain types=
of
attacks that would require actually evaluating and analyzing the resulting =
path,
since we might be called in a context where the volume not yet existing is
totally fine :-/
all in all, this series is the kind of change that warrants close attention=
, and
IMHO, when in doubt, might benefit from a few restrictions that don't reall=
y
harm usability but make locking it down more easy.
> return ('iso', $1);
> - } elsif ($volname =3D~ m!^vztmpl/([^/]+$PVE::Storage::VZTMPL_EXT_RE_=
1)$!) {
> + } elsif ($volname =3D~ m!^vztmpl/(.+$PVE::Storage::VZTMPL_EXT_RE_1)$=
!) {
same here
> return ('vztmpl', $1);
> } elsif ($volname =3D~ m!^rootdir/(\d+)$!) {
> return ('rootdir', $1, $1);
> @@ -632,7 +632,7 @@ sub parse_volname {
> return ('backup', $fn, $2);
> }
> return ('backup', $fn);
> - } elsif ($volname =3D~ m!^snippets/([^/]+)$!) {
> + } elsif ($volname =3D~ m!^snippets/(.+)$!) {
and here! this would even allow directly including host files via cloud ini=
t I
think?
> return ('snippets', $1);
> }
> =20
> @@ -1214,12 +1214,12 @@ my $get_subdir_files =3D sub {
> my $info;
> =20
> if ($tt eq 'iso') {
> - next if $fn !~ m!/([^/]+$PVE::Storage::ISO_EXT_RE_0)$!i;
> + next if $fn !~ m!/.+\/template\/iso\/(.+$PVE::Storage::ISO_EXT_RE_0=
)$!i;
same applies here
> =20
> $info =3D { volid =3D> "$sid:iso/$1", format =3D> 'iso' };
> =20
> } elsif ($tt eq 'vztmpl') {
> - next if $fn !~ m!/([^/]+$PVE::Storage::VZTMPL_EXT_RE_1)$!;
> + next if $fn !~ m!/.+\/template\/cache\/(.+$PVE::Storage::VZTMPL_EXT=
_RE_1)$!;
and here
> =20
> $info =3D { volid =3D> "$sid:vztmpl/$1", format =3D> "t$2" };
> =20
> @@ -1251,9 +1251,9 @@ my $get_subdir_files =3D sub {
> =20
> $info->{protected} =3D 1 if -e PVE::Storage::protection_file_path($=
original);
> } elsif ($tt eq 'snippets') {
> -
> + next if $fn !~ m!/.+\/snippets/(.+)!;
and also here
> $info =3D {
> - volid =3D> "$sid:snippets/". basename($fn),
> + volid =3D> "$sid:snippets/$1",
> format =3D> 'snippet',
> };
> }
> --=20
> 2.30.2
>=20
>=20
>=20
> _______________________________________________
> pve-devel mailing list
> pve-devel@lists.proxmox.com
> https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel
>=20
>=20
>=20