authz: add QAuthZListFile object type for a file access control list

Add a QAuthZListFile object type that implements the QAuthZ interface. This
built-in implementation is a proxy around the QAuthZList object type,
initializing it from an external file, and optionally, automatically
reloading it whenever it changes.

To create an instance of this object via the QMP monitor, the syntax
used would be:

      {
        "execute": "object-add",
        "arguments": {
          "qom-type": "authz-list-file",
          "id": "authz0",
          "props": {
            "filename": "/etc/qemu/vnc.acl",
	    "refresh": true
          }
        }
      }

If "refresh" is "yes", inotify is used to monitor the file,
automatically reloading changes. If an error occurs during reloading,
all authorizations will fail until the file is next successfully
loaded.

The /etc/qemu/vnc.acl file would contain a JSON representation of a
QAuthZList object

    {
      "rules": [
         { "match": "fred", "policy": "allow", "format": "exact" },
         { "match": "bob", "policy": "allow", "format": "exact" },
         { "match": "danb", "policy": "deny", "format": "glob" },
         { "match": "dan*", "policy": "allow", "format": "exact" },
      ],
      "policy": "deny"
    }

This sets up an authorization rule that allows 'fred', 'bob' and anyone
whose name starts with 'dan', except for 'danb'. Everyone unmatched is
denied.

The object can be loaded on the comand line using

   -object authz-list-file,id=authz0,filename=/etc/qemu/vnc.acl,refresh=yes

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

1 files changed, 46 insertions, 0 deletions

diff --git a/qemu-options.hx b/qemu-options.hx
index 6d93447..217662a 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -4389,6 +4389,52 @@ would look like:
 Note the use of quotes due to the x509 distinguished name containing
 whitespace, and escaping of ','.
 
+@item -object authz-listfile,id=@var{id},filename=@var{path},refresh=@var{yes|no}
+
+Create an authorization object that will control access to network services.
+
+The @option{filename} parameter is the fully qualified path to a file
+containing the access control list rules in JSON format.
+
+An example set of rules that match against SASL usernames might look
+like:
+
+@example
+  @{
+    "rules": [
+       @{ "match": "fred", "policy": "allow", "format": "exact" @},
+       @{ "match": "bob", "policy": "allow", "format": "exact" @},
+       @{ "match": "danb", "policy": "deny", "format": "glob" @},
+       @{ "match": "dan*", "policy": "allow", "format": "exact" @},
+    ],
+    "policy": "deny"
+  @}
+@end example
+
+When checking access the object will iterate over all the rules and
+the first rule to match will have its @option{policy} value returned
+as the result. If no rules match, then the default @option{policy}
+value is returned.
+
+The rules can either be an exact string match, or they can use the
+simple UNIX glob pattern matching to allow wildcards to be used.
+
+If @option{refresh} is set to true the file will be monitored
+and automatically reloaded whenever its content changes.
+
+As with the @code{authz-simple} object, the format of the identity
+strings being matched depends on the network service, but is usually
+a TLS x509 distinguished name, or a SASL username.
+
+An example authorization object to validate a SASL username
+would look like:
+@example
+ # $QEMU \
+     ...
+     -object authz-simple,id=auth0,filename=/etc/qemu/vnc-sasl.acl,refresh=yes
+     ...
+@end example
+
 @end table
 
 ETEXI