[pve-devel] fix #5254: add separate Sys.AccessNetwork privilege

[Thomas Lamprecht <t.lamprecht@proxmox.com>]

Adds a new Sys.AccessNetwork privilege that can be used to guard API
endpoints that can do outgoing network requests with (some) user control
over said requests, like e.g. the "download URL to storage" one.

## Backstory:

This stems from an user request [0] w.r.t. the "download image through
and URL directly to a storage" functionality and their use case of that
through automation while wanting to adhere to the principle of least
privilege.

Because before this series the access to the required endpoints was
guarded by the more powerful Sys.Modify and Sys.Audit privilege
requirement on the / root ACL object path.
So, if anybody wants to set up an API token so that automation can
handle image downloads they'd need to give that API token very powerful
permissions to make it work.

A more specialized privilege seems warranted now, so add the
Sys.AccessNetwork one and adapt the /nodes/{node}/query-url-metadata and
the related /nodes/{node}/storage/{storage}/download-url API endpoints
for now.

## Testing:

Tested by creating a new custom role with the privileges
`Datastore.Audit,Datastore.AllocateTemplate,Sys.AccessNetwork`, then
created a user that gets a permission with above role for a specific
node and a storage and then try querying and downloading an image, with
and without this patch series applied.

## Future Work

We could this even re-use for other endpoints, like adding storages that
are accessed through the network, as that provides a (limited) side
channel too.

access-control:

Thomas Lamprecht (1):
      add Sys.AccessNetwork privilege

 src/PVE/AccessControl.pm | 1 +
 src/test/perm-test1.pl   | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

storage:

Thomas Lamprecht (1):
      fix #5254: api: allow usage of download-url with Sys.AccessNetwork

 src/PVE/API2/Storage/Status.pm | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

manager:

Thomas Lamprecht (2):
      api: nodes: allow usage of query url metadata with Sys.AccessNetwork
      ui: storage: enable download-url button with Sys.AccessNetwork capability

 PVE/API2/Nodes.pm               | 5 ++++-
 www/manager6/storage/Browser.js | 5 ++++-
 2 files changed, 8 insertions(+), 2 deletions(-)