[pve-devel] [PATCH storage v5 04/12] ovf: improve and simplify path checking code

[Fiona Ebner]

On 14.11.24 10:32 AM, Dominik Csapak wrote:
> @@ -244,22 +235,31 @@ ovf:Item[rasd:InstanceID='%s']/rasd:ResourceType", $controller_id);
>  	my $adress_on_controller = $xpc->findvalue('rasd:AddressOnParent', $item_node);
>  	my $pve_disk_address = id_to_pve($controller_type) . $adress_on_controller;
>  
> +	# from Disk Node, find corresponding filepath
> +	my $xpath_find_filepath = sprintf("/ovf:Envelope/ovf:References/ovf:File[\@ovf:id='%s']/\@ovf:href", $fileref);
> +	my $filepath = $xpc->findvalue($xpath_find_filepath);
> +	if (!$filepath) {
> +	    warn "invalid file reference $fileref, skipping\n";
> +	    next;
> +	}
> +	print "file path: $filepath\n" if $debug;
> +	my $original_filepath = $filepath;
> +	($filepath) = $filepath =~ m|^(${PVE::Storage::SAFE_CHAR_CLASS_RE}+)$|; # untaint & check no sub/parent dirs
> +	die "referenced path '$original_filepath' is invalid\n" if !$filepath || $filepath eq "." || $filepath eq "..";
> +
>  	# resolve symlinks and relative path components
>  	# and die if the diskimage is not somewhere under the $ovf path
> -	my $ovf_dir = realpath(dirname(File::Spec->rel2abs($ovf)));
> -	my $backing_file_path = realpath(join ('/', $ovf_dir, $filepath));
> -	if ($backing_file_path !~ /^\Q${ovf_dir}\E/) {
> -	    die "error parsing $filepath, are you using a symlink ?\n";
> -	}

Don't we still need this check against symlinks?

> +	my $ovf_dir = realpath(dirname(File::Spec->rel2abs($ovf)))
> +	    or die "could not get absolute path of $ovf: $!\n";
> +	my $backing_file_path = realpath(join ('/', $ovf_dir, $filepath))
> +	    or die "could not get absolute path of $filepath: $!\n";
> +
> +	($backing_file_path) = $backing_file_path =~ m|^(/.*)|; # untaint
>  
>  	if (!-e $backing_file_path && !$isOva) {
>  	    die "error parsing $filepath, file seems not to exist at $backing_file_path\n";
>  	}
>  
> -	($backing_file_path) = $backing_file_path =~ m|^(/.*)|; # untaint
> -	($filepath) = $filepath =~ m|^(${PVE::Storage::SAFE_CHAR_CLASS_RE}+)$|; # untaint & check no sub/parent dirs
> -	die "invalid path\n" if !$filepath;
> -
>  	if (!$isOva) {
>  	    my $size = PVE::Storage::file_size_info($backing_file_path);
>  	    die "error parsing $backing_file_path, cannot determine file size\n"