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Add an authorization backend that talks to PAM to check whether the user
identity is allowed. This only uses the PAM account validation facility,
which is essentially just a check to see if the provided username is permitted
access. It doesn't use the authentication or session parts of PAM, since
that's dealt with by the relevant part of QEMU (eg VNC server).
Consider starting QEMU with a VNC server and telling it to use TLS with
x509 client certificates and configuring it to use an PAM to validate
the x509 distinguished name. In this example we're telling it to use PAM
for the QAuthZ impl with a service name of "qemu-vnc"
$ qemu-system-x86_64 \
-object tls-creds-x509,id=tls0,dir=/home/berrange/security/qemutls,\
endpoint=server,verify-peer=yes \
-object authz-pam,id=authz0,service=qemu-vnc \
-vnc :1,tls-creds=tls0,tls-authz=authz0
This requires an /etc/pam/qemu-vnc file to be created with the auth
rules. A very simple file based whitelist can be setup using
$ cat > /etc/pam/qemu-vnc <<EOF
account requisite pam_listfile.so item=user sense=allow file=/etc/qemu/vnc.allow
EOF
The /etc/qemu/vnc.allow file simply contains one username per line. Any
username not in the file is denied. The usernames in this example are
the x509 distinguished name from the client's x509 cert.
$ cat > /etc/qemu/vnc.allow <<EOF
CN=laptop.berrange.com,O=Berrange Home,L=London,ST=London,C=GB
EOF
More interesting would be to configure PAM to use an LDAP backend, so
that the QEMU authorization check data can be centralized instead of
requiring each compute host to have file maintained.
The main limitation with this PAM module is that the rules apply to all
QEMU instances on the host. Setting up different rules per VM, would
require creating a separate PAM service name & config file for every
guest. An alternative approach for the future might be to not pass in
the plain username to PAM, but instead combine the VM name or UUID with
the username. This requires further consideration though.
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
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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>
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Add a QAuthZList object type that implements the QAuthZ interface. This
built-in implementation maintains a trivial access control list with a
sequence of match rules and a final default policy. This replicates the
functionality currently provided by the qemu_acl module.
To create an instance of this object via the QMP monitor, the syntax
used would be:
{
"execute": "object-add",
"arguments": {
"qom-type": "authz-list",
"id": "authz0",
"props": {
"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.
It is not currently possible to create this via -object, since there is
no syntax supported to specify non-scalar properties for objects. This
is likely to be addressed by later support for using JSON with -object,
or an equivalent approach.
In any case the future "authz-listfile" object can be used from the
CLI and is likely a better choice, as it allows the ACL to be refreshed
automatically on change.
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
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In many cases a single VM will just need to whitelist a single identity
as the allowed user of network services. This is especially the case for
TLS live migration (optionally with NBD storage) where we just need to
whitelist the x509 certificate distinguished name of the source QEMU
host.
Via QMP this can be configured with:
{
"execute": "object-add",
"arguments": {
"qom-type": "authz-simple",
"id": "authz0",
"props": {
"identity": "fred"
}
}
}
Or via the command line
-object authz-simple,id=authz0,identity=fred
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
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The current qemu_acl module provides a simple access control list
facility inside QEMU, which is used via a set of monitor commands
acl_show, acl_policy, acl_add, acl_remove & acl_reset.
Note there is no ability to create ACLs - the network services (eg VNC
server) were expected to create ACLs that they want to check.
There is also no way to define ACLs on the command line, nor potentially
integrate with external authorization systems like polkit, pam, ldap
lookup, etc.
The QAuthZ object defines a minimal abstract QOM class that can be
subclassed for creating different authorization providers.
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
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