157 lines
6.5 KiB
Markdown
157 lines
6.5 KiB
Markdown
---
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reviewers:
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- erictune
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- lavalamp
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- deads2k
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- liggitt
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title: Using ABAC Authorization
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content_type: concept
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weight: 80
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---
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<!-- overview -->
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Attribute-based access control (ABAC) defines an access control paradigm whereby access rights are granted to users through the use of policies which combine attributes together.
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<!-- body -->
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## Policy File Format
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To enable `ABAC` mode, specify `--authorization-policy-file=SOME_FILENAME` and `--authorization-mode=ABAC` on startup.
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The file format is [one JSON object per line](https://jsonlines.org/). There
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should be no enclosing list or map, only one map per line.
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Each line is a "policy object", where each such object is a map with the following
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properties:
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- Versioning properties:
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- `apiVersion`, type string; valid values are "abac.authorization.kubernetes.io/v1beta1". Allows versioning and conversion of the policy format.
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- `kind`, type string: valid values are "Policy". Allows versioning and conversion of the policy format.
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- `spec` property set to a map with the following properties:
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- Subject-matching properties:
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- `user`, type string; the user-string from `--token-auth-file`. If you specify `user`, it must match the username of the authenticated user.
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- `group`, type string; if you specify `group`, it must match one of the groups of the authenticated user. `system:authenticated` matches all authenticated requests. `system:unauthenticated` matches all unauthenticated requests.
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- Resource-matching properties:
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- `apiGroup`, type string; an API group.
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- Ex: `extensions`
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- Wildcard: `*` matches all API groups.
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- `namespace`, type string; a namespace.
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- Ex: `kube-system`
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- Wildcard: `*` matches all resource requests.
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- `resource`, type string; a resource type
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- Ex: `pods`
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- Wildcard: `*` matches all resource requests.
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- Non-resource-matching properties:
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- `nonResourcePath`, type string; non-resource request paths.
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- Ex: `/version` or `/apis`
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- Wildcard:
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- `*` matches all non-resource requests.
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- `/foo/*` matches all subpaths of `/foo/`.
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- `readonly`, type boolean, when true, means that the Resource-matching policy only applies to get, list, and watch operations, Non-resource-matching policy only applies to get operation.
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{{< note >}}
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An unset property is the same as a property set to the zero value for its type
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(e.g. empty string, 0, false). However, unset should be preferred for
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readability.
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In the future, policies may be expressed in a JSON format, and managed via a
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REST interface.
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{{< /note >}}
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## Authorization Algorithm
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A request has attributes which correspond to the properties of a policy object.
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When a request is received, the attributes are determined. Unknown attributes
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are set to the zero value of its type (e.g. empty string, 0, false).
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A property set to `"*"` will match any value of the corresponding attribute.
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The tuple of attributes is checked for a match against every policy in the
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policy file. If at least one line matches the request attributes, then the
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request is authorized (but may fail later validation).
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To permit any authenticated user to do something, write a policy with the
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group property set to `"system:authenticated"`.
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To permit any unauthenticated user to do something, write a policy with the
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group property set to `"system:unauthenticated"`.
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To permit a user to do anything, write a policy with the apiGroup, namespace,
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resource, and nonResourcePath properties set to `"*"`.
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## Kubectl
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Kubectl uses the `/api` and `/apis` endpoints of api-server to discover
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served resource types, and validates objects sent to the API by create/update
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operations using schema information located at `/openapi/v2`.
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When using ABAC authorization, those special resources have to be explicitly
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exposed via the `nonResourcePath` property in a policy (see [examples](#examples) below):
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* `/api`, `/api/*`, `/apis`, and `/apis/*` for API version negotiation.
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* `/version` for retrieving the server version via `kubectl version`.
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* `/swaggerapi/*` for create/update operations.
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To inspect the HTTP calls involved in a specific kubectl operation you can turn
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up the verbosity:
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kubectl --v=8 version
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## Examples
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1. Alice can do anything to all resources:
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```json
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{"apiVersion": "abac.authorization.kubernetes.io/v1beta1", "kind": "Policy", "spec": {"user": "alice", "namespace": "*", "resource": "*", "apiGroup": "*"}}
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```
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2. The Kubelet can read any pods:
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```json
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{"apiVersion": "abac.authorization.kubernetes.io/v1beta1", "kind": "Policy", "spec": {"user": "kubelet", "namespace": "*", "resource": "pods", "readonly": true}}
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```
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3. The Kubelet can read and write events:
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```json
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{"apiVersion": "abac.authorization.kubernetes.io/v1beta1", "kind": "Policy", "spec": {"user": "kubelet", "namespace": "*", "resource": "events"}}
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```
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4. Bob can just read pods in namespace "projectCaribou":
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```json
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{"apiVersion": "abac.authorization.kubernetes.io/v1beta1", "kind": "Policy", "spec": {"user": "bob", "namespace": "projectCaribou", "resource": "pods", "readonly": true}}
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```
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5. Anyone can make read-only requests to all non-resource paths:
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```json
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{"apiVersion": "abac.authorization.kubernetes.io/v1beta1", "kind": "Policy", "spec": {"group": "system:authenticated", "readonly": true, "nonResourcePath": "*"}}
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{"apiVersion": "abac.authorization.kubernetes.io/v1beta1", "kind": "Policy", "spec": {"group": "system:unauthenticated", "readonly": true, "nonResourcePath": "*"}}
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```
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[Complete file example](https://releases.k8s.io/{{< param "githubbranch" >}}/pkg/auth/authorizer/abac/example_policy_file.jsonl)
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## A quick note on service accounts
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Every service account has a corresponding ABAC username, and that service account's user name is generated according to the naming convention:
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```shell
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system:serviceaccount:<namespace>:<serviceaccountname>
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```
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Creating a new namespace leads to the creation of a new service account in the following format:
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```shell
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system:serviceaccount:<namespace>:default
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```
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For example, if you wanted to grant the default service account (in the `kube-system` namespace) full
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privilege to the API using ABAC, you would add this line to your policy file:
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```json
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{"apiVersion":"abac.authorization.kubernetes.io/v1beta1","kind":"Policy","spec":{"user":"system:serviceaccount:kube-system:default","namespace":"*","resource":"*","apiGroup":"*"}}
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```
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The apiserver will need to be restarted to pickup the new policy lines.
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