[pve-devel] [PATCH v2 qemu-server] remote migration: fix online migration via API clients

[Fabian Grünbichler]

On August 13, 2024 10:42 am, Fiona Ebner wrote:
> As reported in the community forum [0], when a remote migration
> request comes in via an API client, the -T flag for Perl is set, so an
> insecure dependency in a call like unlink() in forward_unix_socket()
> will fail with:
> 
>> failed to write forwarding command - Insecure dependency in unlink while running with -T switch
> 
> To fix it, untaint the problematic socket addresses coming from the
> remote side. Require that all sockets are below '/run/qemu-server/'
> and end with '.migrate'. This allows extensions in the future while
> still being quite strict.
> 
> [0]: https://forum.proxmox.com/threads/123048/post-691958
> 
> Signed-off-by: Fiona Ebner <f.ebner at proxmox.com>
> ---
> 
> Changes in v2:
> * rule out '../' in path
> 
>  PVE/QemuMigrate.pm | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/PVE/QemuMigrate.pm b/PVE/QemuMigrate.pm
> index e71face4..d31589e7 100644
> --- a/PVE/QemuMigrate.pm
> +++ b/PVE/QemuMigrate.pm
> @@ -1095,7 +1095,10 @@ sub phase2 {
>  	die "only UNIX sockets are supported for remote migration\n"
>  	    if $tunnel_info->{proto} ne 'unix';
>  
> -	my $remote_socket = $tunnel_info->{addr};
> +	# untaint
> +	my ($remote_socket) =
> +	    $tunnel_info->{addr} =~ m|^(/run/qemu-server/(?:(?!\.\./).)+\.migrate)$|;

should we just switch to `\d+`, like we do for regular migration? in
phase2_start_local_cluster we have:

	elsif ($line =~ m!^migration listens on (unix):(/run/qemu-server/(\d+)\.migrate)$!) {
	    $tunnel_info->{addr} = $2;
	    die "Destination UNIX sockets VMID does not match source VMID" if $vmid ne $3;
	    $tunnel_info->{proto} = $1;
	}

and I don't really see a reason to deviate from that scheme any time
soon?

> +	die "unexpected socket address '$tunnel_info->{addr}'\n" if !$remote_socket;
>  	my $local_socket = $remote_socket;
>  	$local_socket =~ s/$remote_vmid/$vmid/g;
>  	$tunnel_info->{addr} = $local_socket;
> @@ -1104,6 +1107,9 @@ sub phase2 {
>  	PVE::Tunnel::forward_unix_socket($self->{tunnel}, $local_socket, $remote_socket);
>  
>  	foreach my $remote_socket (@{$tunnel_info->{unix_sockets}}) {
> +	    # untaint
> +	    ($remote_socket) = $remote_socket =~ m|^(/run/qemu-server/(?:(?!\.\./).)+\.migrate)$|
> +		or die "unexpected socket address '$remote_socket'\n";
>  	    my $local_socket = $remote_socket;
>  	    $local_socket =~ s/$remote_vmid/$vmid/g;
>  	    next if $self->{tunnel}->{forwarded}->{$local_socket};
> -- 
> 2.39.2
> 
> 
> 
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