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update audit document with advanced audit features added in 1.7
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@chenopis
chenopis authored Jun 27, 2017
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257 changes: 237 additions & 20 deletions docs/tasks/debug-application-cluster/audit.md
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Expand Up @@ -2,6 +2,7 @@
assignees:
- soltysh
- sttts
- ericchiang
title: Auditing
redirect_from:
- "/docs/admin/audit/"
Expand All @@ -17,6 +18,7 @@ Kubernetes Audit provides a security-relevant chronological set of records docum
the sequence of activities that have affected system by individual users, administrators
or other components of the system. It allows cluster administrator to
answer the following questions:

- what happened?
- when did it happen?
- who initiated it?
Expand All @@ -25,36 +27,27 @@ answer the following questions:
- from where was it initiated?
- to where was it going?

NOTE: Currently, Kubernetes provides only basic audit capabilities, there is still a lot
of work going on to provide fully featured auditing capabilities (see [this issue](https://github.com/kubernetes/features/issues/22)).
## Audit logs

Kubernetes audit is part of [kube-apiserver](/docs/admin/kube-apiserver) logging all requests
coming to the server. Each audit log contains two entries:
Kubernetes audit is part of [Kube-apiserver][kube-apiserver] logging all requests
processed by the server. Each audit log entry contains two lines:

1. The request line containing:
- unique id allowing to match the response line (see 2)
- source ip of the request
- HTTP method being invoked
- original user invoking the operation
- original user's groups info
- impersonated user for the operation
- impersonated groups info
- namespace of the request or <none>
- URI as requested
2. The response line containing:
- the unique id from 1
- response code
1. The request line containing a unique ID to match the response and request metadata, such as the source IP, requesting user, impersonation information, resource being requested, etc.
2. The response line containing a unique ID matching the request line and the response code.

Example output for user `admin` asking for a list of pods:
Example output for `admin` user listing pods in the `default` namespace:

```
2017-03-21T03:57:09.106841886-04:00 AUDIT: id="c939d2a7-1c37-4ef1-b2f7-4ba9b1e43b53" ip="127.0.0.1" method="GET" user="admin" groups="\"system:masters\",\"system:authenticated\"" as="<self>" asgroups="<lookup>" namespace="default" uri="/api/v1/namespaces/default/pods"
2017-03-21T03:57:09.108403639-04:00 AUDIT: id="c939d2a7-1c37-4ef1-b2f7-4ba9b1e43b53" response="200"
```

## Configuration
Note that this format changes when enabling the `AdvancedAuditing` feature discussed
later in this document.

### Configuration

[Kube-apiserver](/docs/admin/kube-apiserver) provides following options which are responsible
[Kube-apiserver][kube-apiserver] provides the following options which are responsible
for configuring where and how audit logs are handled:

- `audit-log-path` - enables the audit log pointing to a file where the requests are being logged to.
Expand All @@ -70,3 +63,227 @@ the file name (before the file extension) and create a new audit log file.
Kubernetes may delete old log files when creating a new log file; you can configure
how many files are retained and how old they can be by specifying the `audit-log-maxbackup`
and `audit-log-maxage` options.

## Advanced audit

Kubernetes 1.7 expands auditing with experimental functionality such as event
filtering and a webhook for integration with external systems. The rest of this
document covers features that are __alpha__ and may change in backward incompatible
ways.

Enable the alpha auditing features using the `AdvancedAuditing` feature gate on
the [kube-apiserver][kube-apiserver]:

```
--feature-gates=AdvancedAuditing=true
```

`AdvancedAuditing`is customizeable in two ways. Policy, which determines what's recorded,
and backends, which persist records. Backend implementations include logs files and
webhooks.

The structure of audit events changes when enabling the `AdvancedAuditing` feature
flag. This includes some cleanups, such as the `method` reflecting the verb evaluated
by the [authoriation layer](/docs/admin/authorization/) instead of the HTTP verb
("create" instead of "POST"). Also, instead of always generating two events per
request, events are recorded with an associated "stage." The known stages are:

- `RequestReceived` - The stage for events generated as soon as the audit handler receives the request.
- `ResponseStarted` - Once the response headers are sent, but before the response body is sent. This stage is only generated for long-running requests (e.g. watch).
- `ResponseComplete` - Once the response body has been completed.
- `Panic` - Events generated when a panic occured.

### Audit Policy

Audit policy is a document defining rules about what events should be recorded.
The policy is passed to the [kube-apiserver][kube-apiserver] using the
`--audit-policy-file` flag.

```
--audit-policy-file=/etc/kubernetes/audit-policy.yaml
```

If `AdvancedAuditing` is enabled and this flag is omitted, no events are logged.

The policy file holds rules that determine the level of an event. Known audit levels are:

- `None` - don't log events that match this rule.
- `Metadata` - log request metadata (requesting user, timestamp, resource, verb, etc.) but not request or response body.
- `Request` - log event metadata and request body but not response body.
- `RequestResponse` - log event metadata, request and response bodies.

When an event is processed it's compared against the list of rules in order.
The first matching rule sets the audit level of the event. The audit policy is
defined by the [`audit.k8s.io` API group][audit-api].

An example audit policy file:

```yaml
rules:
# Don't log watch requests by the "system:kube-proxy" on endpoints or services
- level: None
users: ["system:kube-proxy"]
verbs: ["watch"]
resources:
- group: "" # core API group
resources: ["endpoints", "services"]

# Don't log authenticated requests to certain non-resource URL paths.
- level: None
userGroups: ["system:authenticated"]
nonResourceURLs:
- "/api*" # Wildcard matching.
- "/version"

# Log the request body of configmap changes in kube-system.
- level: Request
resources:
- group: "" # core API group
resources: ["configmaps"]
# This rule only applies to resources in the "kube-system" namespace.
# The empty string "" can be used to select non-namespaced resources.
namespaces: ["kube-system"]

# Log configmap and secret changes in all other namespaces at the Metadata level.
- level: Metadata
resources:
- group: "" # core API group
resources: ["secrets", "configmaps"]

# Log all other resources in core and extensions at the Request level.
- level: Request
resources:
- group: "" # core API group
- group: "extensions" # Version of group should NOT be included.

# A catch-all rule to log all other requests at the Metadata level.
- level: Metadata
```
You can use a minimal audit policy file to log all requests at the `Metadata` level:

```yaml
# Log all requests at the Metadata level.
rules:
- level: Metadata
```

The [audit profile used by GCE][gce-audit-profile] should be used as reference by
admins constructing their own audit profiles.

### Audit backends

Audit backends implement strategies for emitting events. The [kube-apiserver][kube-apiserver]
provides a logging and webhook backend.

Each request to the API server can generate multiple events, one when the request is received,
another when the response is sent, and additional events for log running requests (such as
watches). The ID of events will be the same if they were generated from the same request.

The event format is defined by the `audit.k8s.io` API group. The `v1alpha1` format of this
API can be found [here][audit-api] with more details about the exact fields captured.

#### Log backend

The behavior of the `--audit-log-path` flag changes when enabling the `AdvancedAuditing`
feature flag. This includes the cleanups discussed above, such as changes to the `method`
values and the introduction of a "stage" for each event. As before, the `id` field of
the log line indicates which events were generated from the same request. Events are
formatted as follows:

```
2017-06-15T21:50:50.259470834Z AUDIT: id="591e9fde-6a98-46f6-b7bc-ec8ef575696d" stage="RequestReceived" ip="10.2.1.3" method="update" user="system:serviceaccount:kube-system:default" groups="\"system:serviceaccounts\",\"system:serviceaccounts:kube-system\",\"system:authenticated\"" as="<self>" asgroups="<lookup>" namespace="kube-system" uri="/api/v1/namespaces/kube-system/endpoints/kube-controller-manager" response="<deferred>"
2017-06-15T21:50:50.259470834Z AUDIT: id="591e9fde-6a98-46f6-b7bc-ec8ef575696d" stage="ResponseComplete" ip="10.2.1.3" method="update" user="system:serviceaccount:kube-system:default" groups="\"system:serviceaccounts\",\"system:serviceaccounts:kube-system\",\"system:authenticated\"" as="<self>" asgroups="<lookup>" namespace="kube-system" uri="/api/v1/namespaces/kube-system/endpoints/kube-controller-manager" response="200"
```

Logged evens omit the request and response bodies. The `Request` and
`RequestResponse` levels are equivalent to `Metadata` for this backend.

#### Webhook backend

The audit webhook backend can be used to have [kube-apiserver][kube-apiserver]
send audit events to a remote service. The webhook requires the `AdvancedAuditing`
feature flag and is configured using the following command line flags:

```
--audit-webhook-config-file=/etc/kubernetes/audit-webhook-kubeconfig
--audit-webhook-mode=batch
```

`audit-webhook-mode` controls buffering strategies used by the webhook. Known modes are:

- `batch` - buffer events and asynchronously send the set of events to the external service.
- `blocking` - block API server responses on sending each event to the external service.

The webhook config file uses the kubeconfig format to specify the remote address of
the service and credentials used to connect to it.

```
# clusters refers to the remote service.
clusters:
- name: name-of-remote-audit-service
cluster:
certificate-authority: /path/to/ca.pem # CA for verifying the remote service.
server: https://audit.example.com/audit # URL of remote service to query. Must use 'https'.

# users refers to the API server's webhook configuration.
users:
- name: name-of-api-server
user:
client-certificate: /path/to/cert.pem # cert for the webhook plugin to use
client-key: /path/to/key.pem # key matching the cert

# kubeconfig files require a context. Provide one for the API server.
current-context: webhook
contexts:
- context:
cluster: name-of-remote-audit-service
user: name-of-api-sever
name: webhook
```
Events are POSTed as a JSON serialized `EventList`. An example payload:
```json
{
"kind": "EventList",
"apiVersion": "audit.k8s.io/v1alpha1",
"items": [
{
"metadata": {
"creationTimestamp": null
},
"level": "Metadata",
"timestamp": "2017-06-15T23:07:40Z",
"auditID": "4faf711a-9094-400f-a876-d9188ceda548",
"stage": "ResponseComplete",
"requestURI": "/apis/rbac.authorization.k8s.io/v1beta1/namespaces/kube-public/rolebindings/system:controller:bootstrap-signer",
"verb": "get",
"user": {
"username": "system:apiserver",
"uid": "97a62906-e4d7-4048-8eda-4f0fb6ff8f1e",
"groups": [
"system:masters"
]
},
"sourceIPs": [
"127.0.0.1"
],
"objectRef": {
"resource": "rolebindings",
"namespace": "kube-public",
"name": "system:controller:bootstrap-signer",
"apiVersion": "rbac.authorization.k8s.io/v1beta1"
},
"responseStatus": {
"metadata": {},
"code": 200
}
}
]
}
```

[audit-api]: https://github.com/kubernetes/kubernetes/blob/v1.7.0-rc.1/staging/src/k8s.io/apiserver/pkg/apis/audit/v1alpha1/types.go
[kube-apiserver]: /docs/admin/kube-apiserver
[gce-audit-profile]: https://github.com/kubernetes/kubernetes/blob/v1.7.0-rc.1/cluster/gce/gci/configure-helper.sh#L490

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