api: disallow virDomainGetHostname for read-only connections

The virDomainGetHostname API is fetching guest information and this may
involve use of an untrusted guest agent. As such its use must be
forbidden on a read-only connection to libvirt.

Fixes CVE-2019-3886
Reviewed-by: NJim Fehlig <jfehlig@suse.com>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

src/libvirt-domain.c

@@ -11031,6 +11031,8 @@ virDomainGetHostname(virDomainPtr domain, unsigned int flags)
     virCheckDomainReturn(domain, NULL);
     conn = domain->conn;
 
+    virCheckReadOnlyGoto(domain->conn->flags, error);
+
     if (conn->driver->domainGetHostname) {
         char *ret;
         ret = conn->driver->domainGetHostname(domain, flags);