libvirt: Audit log
Description: libvirt, virtualization, virtualization API

# Audit log

- Introduction
- Configuration
- Message types
  - VIRT_CONTROL
  - VIRT_MACHINE_ID
  - VIRT_RESOURCE
    - Virtual CPU
    - Memory
    - Disk
    - Network interface
    - Filesystem
    - Host device
    - TPM
    - RNG
    - console/serial/parallel/channel
    - smartcard
    - Redirected device
    - Control group
    - Shared memory

## 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

- `audit_level=0` - libvirt auditing is disabled regardless of host audit subsystem enablement.
- `audit_level=1` - libvirt auditing is enabled if the host audit subsystem is enabled, otherwise it is disabled. This is the default behaviour.
- `audit_level=2` - libvirt auditing is enabled regardless of host audit subsystem enablement. If the host audit subsystem is disabled, then libvirtd will refuse to complete startup and exit with an error.

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/libvirtd.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` or `tpm-emulator`
`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

#### console/serial/parallel/channel

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 `chardev`
`old-chardev`
  Original path of the backing character device for given emulated device
`new-chardev`
  Updated path of the backing character device for given emulated device

#### smartcard

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 `smartcard`
`old-smartcard`
  Original path of the backing character device, certificate store or "nss-smartcard-device" for host smartcard passthrough.
`new-smartcard`
  Updated path of the backing character device, certificate store or "nss-smartcard-device" for host smartcard passthrough.

#### 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

#### Shared memory

The `msg` field will include the following sub-fields

`resrc`
  The type of resource assigned. Set to `shmem`
`reason`
  The reason which caused the resource to be assigned to happen
`size`
  The size of the shared memory region
`shmem`
  Name of the shared memory region
`source`
  Path of the backing character device for given emulated device