[PATCH container v2] fix #7164: lxc: restore: apply password and ssh keys during container restore

[Elias Huhsovitz <e.huhsovitz@proxmox.com>]

When restoring a container with `pct restore`, the `--password` and
`--ssh-public-keys` options are silently ignored. Previously, the API
endpoint only invoked setup hooks during initial container creation or
cloning, skipping them entirely for restores.

Introduce a new `post_restore_hook` in the LXC setup plugin
architecture. This hook applies the provided credentials if they are
defined.

Add `check_systemd_nesting` to the `post_restore_hook`.

Move `template_fixup`from the API endpoint function to the
`post_restore_hook`, matching the `post_create_hook` logic.

Signed-off-by: Elias Huhsovitz <e.huhsovitz@proxmox.com>
---

v1: https://lore.proxmox.com/all/20260716153959.183045-1-e.huhsovitz@proxmox.com/

Changes made according to the feedback (big thanks):
https://lore.proxmox.com/all/95a38704-543e-4820-b36c-696cf192a684@proxmox.com/

changes v1->v2:
* move logic into new function `post_restore_hook`
* do not call `post_create_hook` unconditionally
* conditionally call functions to:
    - set password
    - set ssh keys
* call `check_systemd_nesting()` for pct restore

 src/PVE/API2/LXC.pm            | 2 +-
 src/PVE/LXC/Setup.pm           | 9 +++++++++
 src/PVE/LXC/Setup/Base.pm      | 9 +++++++++
 src/PVE/LXC/Setup/Plugin.pm    | 5 +++++
 src/PVE/LXC/Setup/Unmanaged.pm | 4 ++++
 5 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/src/PVE/API2/LXC.pm b/src/PVE/API2/LXC.pm
index 22320ba..ad3b635 100644
--- a/src/PVE/API2/LXC.pm
+++ b/src/PVE/API2/LXC.pm
@@ -590,7 +590,7 @@ __PACKAGE__->register_method({
                         );
                         PVE::LXC::create_ifaces_ipams_ips($conf, $vmid) if $unique;
                         my $lxc_setup = PVE::LXC::Setup->new($conf, $rootdir);
-                        $lxc_setup->template_fixup($conf);
+                        $lxc_setup->post_restore_hook($password, $ssh_keys);
                     } else {
                         my $lxc_setup = PVE::LXC::Setup->new($conf, $rootdir); # detect OS
                         PVE::LXC::Config->write_config($vmid, $conf); # safe config (after OS detection)
diff --git a/src/PVE/LXC/Setup.pm b/src/PVE/LXC/Setup.pm
index d936af2..58cadba 100644
--- a/src/PVE/LXC/Setup.pm
+++ b/src/PVE/LXC/Setup.pm
@@ -329,6 +329,15 @@ sub post_create_hook {
     $self->check_systemd_nesting();
 }
 
+sub post_restore_hook {
+    my ($self, $root_password, $ssh_keys) = @_;
+
+    $self->protected_call(sub {
+        $self->{plugin}->post_restore_hook($self->{conf}, $root_password, $ssh_keys);
+    });
+    $self->check_systemd_nesting();
+}
+
 sub unified_cgroupv2_support {
     my ($self) = @_;
 
diff --git a/src/PVE/LXC/Setup/Base.pm b/src/PVE/LXC/Setup/Base.pm
index 567f9d6..f0e1f01 100644
--- a/src/PVE/LXC/Setup/Base.pm
+++ b/src/PVE/LXC/Setup/Base.pm
@@ -735,6 +735,15 @@ sub post_create_hook {
     # fixme: what else ?
 }
 
+sub post_restore_hook {
+    my ($self, $conf, $root_password, $ssh_keys) = @_;
+
+    $self->template_fixup($conf);
+
+    $self->set_user_password($conf, 'root', $root_password) if defined($root_password);
+    $self->set_user_authorized_ssh_keys($conf, 'root', $ssh_keys) if defined($ssh_keys);
+}
+
 # File access wrappers for container setup code.
 # NOTE: those are not direct part of the Plugin API (yet), avoid using them outside the child plugins
 # For user-namespace support these might need to take uid and gid maps into account.
diff --git a/src/PVE/LXC/Setup/Plugin.pm b/src/PVE/LXC/Setup/Plugin.pm
index 95a633f..6ba656b 100644
--- a/src/PVE/LXC/Setup/Plugin.pm
+++ b/src/PVE/LXC/Setup/Plugin.pm
@@ -99,4 +99,9 @@ sub post_create_hook {
     croak "implement me in sub-class";
 }
 
+sub post_restore_hook {
+    my ($self, $conf, $root_password, $ssh_keys) = @_;
+    croak "implement me in sub-class";
+}
+
 1;
diff --git a/src/PVE/LXC/Setup/Unmanaged.pm b/src/PVE/LXC/Setup/Unmanaged.pm
index b51be55..0b440cf 100644
--- a/src/PVE/LXC/Setup/Unmanaged.pm
+++ b/src/PVE/LXC/Setup/Unmanaged.pm
@@ -84,4 +84,8 @@ sub post_create_hook {
     my ($self, $conf, $root_password, $ssh_keys) = @_;
 }
 
+sub post_restore_hook {
+    my ($self, $conf, $root_password, $ssh_keys) = @_;
+}
+
 1;
-- 
2.47.3