Audit log

Introduction

A number of the libvirt virtualization drivers (QEMU/KVM and LXC) include support for logging details of important operations to the host's audit subsystem. This provides administrators / auditors with a canonical historical record of changes to virtual machines' / containers' lifecycle states and their configuration. On hosts which are running the Linux audit daemon, the logs will usually end up in /var/log/audit/audit.log

Configuration

The libvirt audit integration is enabled by default on any host which has the Linux audit subsystem active, and disabled otherwise. It is possible to alter this behaviour in the /etc/libvirt/libvirtd.conf configuration file, via the audit_level parameter

In addition to have formal messages sent to the audit subsystem it is possible to tell libvirt to inject messages into its own logging layer. This will result in messages ending up in the systemd journal or /var/log/libvirt/libivrtd.log on non-systemd hosts. This is disabled by default, but can be requested by setting the audit_logging=1 configuration parameter in the same file mentioned above.

Message types

Libvirt defines three core audit message types each of which will be described below. There are a number of common fields that will be reported for all message types.

pid
Process ID of the libvirtd daemon generating the audit record.
uid
User ID of the libvirtd daemon process generating the audit record.
subj
Security context of the libvirtd daemon process generating the audit record.
msg
String containing a list of key=value pairs specific to the type of audit record being reported.

Some fields in the msg string are common to audit records

virt
Type of virtualization driver used. One of qemu or lxc
vm
Host driver unique name of the guest
uuid
Globally unique identifier for the guest
exe
Path of the libvirtd daemon
hostname
Currently unused
addr
Currently unused
terminal
Currently unused
res
Result of the action, either success or failed

VIRT_CONTROL

Reports change in the lifecycle state of a virtual machine. The msg field will include the following sub-fields

op
Type of operation performed. One of start, stop or init
reason
The reason which caused the operation to happen
vm-pid
ID of the primary/leading process associated with the guest
init-pid
ID of the init process in a container. Only if op=init and virt=lxc
pid-ns
Namespace ID of the init process in a container. Only if op=init and virt=lxc

VIRT_MACHINE_ID

Reports the association of a security context with a guest. The msg field will include the following sub-fields

model
The security driver type. One of selinux or apparmor
vm-ctx
Security context for the guest process
img-ctx
Security context for the guest disk images and other assigned host resources

VIRT_RESOURCE

Reports the usage of a host resource by a guest. The fields include will vary according to the type of device being reported. When the guest is initially booted records will be generated for all assigned resources. If any changes are made to the running guest configuration, for example hotplug devices, or adjust resources allocation, further records will be generated.

Virtual CPU

The msg field will include the following sub-fields

reason
The reason which caused the resource to be assigned to happen
resrc
The type of resource assigned. Set to vcpu
old-vcpu
Original vCPU count, or 0
new-vcpu
Updated vCPU count

Memory

The msg field will include the following sub-fields

reason
The reason which caused the resource to be assigned to happen
resrc
The type of resource assigned. Set to mem
old-mem
Original memory size in bytes, or 0
new-mem
Updated memory size in bytes

Disk

The msg field will include the following sub-fields

reason
The reason which caused the resource to be assigned to happen
resrc
The type of resource assigned. Set to disk
old-disk
Original host file or device path acting as the disk backing file
new-disk
Updated host file or device path acting as the disk backing file

Network interface

The msg field will include the following sub-fields

reason
The reason which caused the resource to be assigned to happen
resrc
The type of resource assigned. Set to net
old-net
Original MAC address of the guest network interface
new-net
Updated MAC address of the guest network interface

If there is a host network interface associated with the guest NIC then further records may be generated

reason
The reason which caused the resource to be assigned to happen
resrc
The type of resource assigned. Set to net
net
MAC address of the host network interface
rdev
Name of the host network interface

Filesystem

The msg field will include the following sub-fields

reason
The reason which caused the resource to be assigned to happen
resrc
The type of resource assigned. Set to fs
old-fs
Original host directory, file or device path backing the filesystem
new-fs
Updated host directory, file or device path backing the filesystem

Host device

The msg field will include the following sub-fields

reason
The reason which caused the resource to be assigned to happen
resrc
The type of resource assigned. Set to hostdev or dev
dev
The unique bus identifier of the USB, PCI or SCSI device, if resrc=dev
disk
The path of the block device assigned to the guest, if resrc=hostdev
chardev
The path of the character device assigned to the guest, if resrc=hostdev

TPM

The msg field will include the following sub-fields

reason
The reason which caused the resource to be assigned to happen
resrc
The type of resource assigned. Set to tpm
device
The path of the host TPM device assigned to the guest

RNG

The msg field will include the following sub-fields

reason
The reason which caused the resource to be assigned to happen
resrc
The type of resource assigned. Set to rng
old-rng
Original path of the host entropy source for the RNG
new-rng
Updated path of the host entropy source for the RNG

Redirected device

The msg field will include the following sub-fields

reason
The reason which caused the resource to be assigned to happen
resrc
The type of resource assigned. Set to redir
bus
The bus type, only usb allowed
device
The device type, only USB redir allowed

Control group

The msg field will include the following sub-fields

reason
The reason which caused the resource to be assigned to happen
resrc
The type of resource assigned. Set to cgroup
cgroup
The name of the cgroup controller