open-vault/website/source/guides/policies.html.md

layout	page_title	sidebar_current	description
guides	Policies - Guides	guides-governance	Policies in Vault control what a user can access.

Policies

In Vault, use policies to govern the behavior of clients and instrument Role-Based Access Control (RBAC) by specifying access privileges (authorization).

When you first initialize Vault, the root policy gets created by default. The root policy is a special policy that gives superuser access to everything in Vault. This allows the superuser to set up initial policies, tokens, etc.

In addition, there is another build-in policy, default gets created. The default policy is attached to all tokens and provides common permissions.

Everything in Vault is path based, and write policies to grant or forbid access to certain paths and operations in Vault. Vault operates on a secure by default standard, and as such an empty policy grants no permission in the system.

HashiCorp Configuration Language (HCL)

Policies written in HCL format are often referred as ACL Policies. Sentinel is another framework for policy which is available in Vault Enterprise. Since Sentinel is an enterprise-only feature, this guide focuses on writing ACL policies.

NOTE: HCL is JSON compatible; therefore, JSON can be used as completely valid input.

Reference Material

• Policies documentation
• Policy API documentation
• Getting Started guide on policies

Estimated Time to Complete

10 minutes

Personas

The scenario described in this guide introduces the following personas:

• root sets up initial policies for admin
• admin is empowered with managing a Vault infrastructure for a team or organizations
• provisioner configures secret backends as well as creating policies for client apps

Challenge

Since Vault centrally secure, store, and access control secrets across distributed infrastructure and applications, it is critical to control permissions before any user or machine can gain access.

Solution

Restrict the use of root policy, and write fine-grained policies to practice least privileged. For example, if an app gets AWS credentials from Vault, write policy grants to read from AWS secret backend but not to delete, etc.

Policies are attached to tokens and roles to enforce client permissions on Vault.

Prerequisites

To perform the tasks described in this guide, you need to have a Vault environment. Refer to the Getting Started guide to install Vault. Make sure that your Vault server has been initialized and unsealed.

Policy requirements

Since this guide demonstrates the creation of an admin policy, log in with root token if possible. Otherwise, make sure that you have the following permissions:

# To perform Step 2 & 3
path "sys/policy/*"
{
  capabilities = ["create", "read", "update", "delete", "list"]
}

# To perform Step 4
path "auth/token/create"
{
  capabilities = ["create", "update"]
}

# To perform Step 4
path "sys/capabilities"
{
  capabilities = ["create", "update"]
}

# To perform Step 4
path "sys/capabilities-self"
{
  capabilities = ["create", "update"]
}

Steps

The basic workflow of creating policies is:

This guide demonstrates basic policy authoring and management tasks.

1. Write ACL policies in HCL format
2. Create policies
3. View existing policies
4. Check capabilities of a token

Step 1: Write ACL policies in HCL format

Remember, empty policy grants no permission in the system. Therefore, ACL policies are defined for each path.

path "<PATH>" {
  capabilities = [ "<LIST_OF_CAPABILITIES>" ]
}

-> The path can have a wildcard ("*") specifying at the end to allow for namespacing. For example, "secret/training_*" grants permissions on any path starts with "secret/training_" (e.g. secret/training_vault).

Define one or more capabilities on each path to control operations that are permitted.

Capability	Associated HTTP verbs
create	POST/PUT
read	GET
update	POST/PUT
delete	DELETE
list	LIST

Policy requirements

First step in creating policies is to gather policy requirements.

Example:

admin is a type of user empowered with managing a Vault infrastructure for a team or organizations. Empowered with sudo, the Administrator is focused on configuring and maintaining the health of Vault cluster(s) as well as providing bespoke support to Vault users.

admin must be able to:

• Mount and manage auth backends broadly across Vault
• Mount and manage secret backends broadly across Vault
• Create and manage ACL policies broadly across Vault
• Read system health check

provisioner is a type of user or service that will be used by an automated tool (e.g. Terraform) to provision and configure a namespace within a Vault secret backend for a new Vault user to access and write secrets.

provisioner must be able to:

• Mount and manage auth backends
• Mount and manage secret backends
• Create and manage ACL policies

Now, you are ready to author policies to fulfill the requirements.

Example policy for admin

admin-policy.hcl

# Manage auth backends broadly across Vault
path "auth/*"
{
  capabilities = ["create", "read", "update", "delete", "list", "sudo"]
}

# List, create, update, and delete auth backends
path "sys/auth/*"
{
  capabilities = ["create", "read", "update", "delete", "sudo"]
}

# Create and manage ACL policies broadly across Vault
path "sys/policy/*"
{
  capabilities = ["create", "read", "update", "delete", "list", "sudo"]
}

# List, create, update, and delete key/value secrets
path "secret/*"
{
  capabilities = ["create", "read", "update", "delete", "list", "sudo"]
}

# Manage and manage secret backends broadly across Vault.
path "sys/mounts/*"
{
  capabilities = ["create", "read", "update", "delete", "list", "sudo"]
}

# Read health checks
path "sys/health"
{
  capabilities = ["read", "sudo"]
}

Example policy for provisioner

provisioner-policy.hcl

# Manage auth backends broadly across Vault
path "auth/*"
{
  capabilities = ["create", "read", "update", "delete", "list"]
}

# List, create, update, and delete auth backends
path "sys/auth/*"
{
  capabilities = ["create", "read", "update", "delete"]
}

# Create and manage ACL policies
path "sys/policy/*"
{
  capabilities = ["create", "read", "update", "delete", "list"]
}

# List, create, update, and delete key/value secrets
path "secret/*"
{
  capabilities = ["create", "read", "update", "delete", "list"]
}

Step 2: Create policies

Now, create admin and provisioner policies in Vault.

CLI command

To create policies:

$ vault policy-write <POLICY_NAME> <POLICY_FILE>

Example:

# Create admin policy
$ vault write admin admin-policy.hcl

# Create provisioner policy
$ vault write provisioner provisioner-policy.hcl

NOTE: To update an existing policy, simply re-run the same command by passing your modified policy (*.hcl).

API call using cURL

To create a policy, use /sys/policy endpoint:

$ curl --header "X-Vault-Token: <TOKEN>" \
       --request PUT \
       --data <PAYLOAD> \
       <VAULT_ADDRESS>/v1/sys/policy/<POLICY_NAME>

Where <TOKEN> is your valid token, and <PAYLOAD> includes policy name and stringfied policy.

Example:

Now, create admin and provisioner policies:

# Create admin policy
$ curl --request PUT --header "X-Vault-Token: ..." --data @admin-payload.json \
    https://vault.rocks/v1/sys/policy/admin

$ cat admin-payload.json
{
  "policy": "path \"auth/*\" { capabilities = [\"create\", \"read\", \"update\", ... }"
}

# Create provisioner policy
$ curl --request PUT --header "X-Vault-Token: ..." --data @provisioner-payload.json \
    https://vault.rocks/v1/sys/policy/provisioner

$ cat provisioner-payload.json
{
  "policy": "path \"auth/*\" { capabilities = [\"create\", \"read\", \"update\", ... }"
}

-> NOTE: You can also use /sys/policies endpoint which is used to manage ACL, RGP, and EGP policies in Vault (RGP and EGP policies are enterprise-only features). To list policies, invoke /sys/policies/acl endpoint.

NOTE: To update an existing policy, simply re-run the same command by passing your modified policy in the request payload (*.json).

Step 3: View existing policies

Make sure that you see the policies you created in Step 2.

CLI command

The following command lists existing policies:

$ vault policies

To view a specific policy:

$ vault read sys/policy/<POLICY_NAME>

Example:

# Read admin policy
$ vault read sys/policy/admin
Key  	Value
---  	-----
name 	admin
rules	# Mount and manage auth backends broadly across Vault
path "auth/*"
{
  capabilities = ["create", "read", "update", "delete", "list", "sudo"]
}

path "sys/auth/*"
{
  capabilities = ["create", "read", "update", "delete", "sudo"]
}

# Create and manage ACL policies broadly across Vault
path "sys/policy/*"
{
  capabilities = ["create", "read", "update", "delete", "list", "sudo"]
}
...

API call using cURL

To list existing ACL policies, use the /sys/policy endpoint.

$ curl --request LIST --header "X-Vault-Token: ..." https://vault.rocks/v1/sys/policy | jq

To read a specific policy, the endpoint path should be /sys/policy/<POLICY_NAME>.

Example:

Read the admin policy:

$ curl --request GET --header "X-Vault-Token: ..." https://vault.rocks/v1/sys/policy/admin | jq
{
  "name": "admin",
  "rules": "# Mount and manage auth backends broadly across Vault\npath \"auth/*\"\n{\n  ...",
  "request_id": "e8151bf3-8136-fef9-428b-1506042350cf",
  "lease_id": "",
  "renewable": false,
  "lease_duration": 0,
  "data": {
  ...

Step 4: Check capabilities of a token

Use the /sys/capabilities endpoint to fetch the capabilities of a token on a given path. This helps to verify what operations are granted based on the policies attached to the token.

CLI command

The command is:

$ vault capabilities <TOKEN> <PATH>

Example:

First, create a token attached to admin policy:

$ vault token-create -policy="admin"
Key            	Value
---            	-----
token          	79ecdd41-9bac-1ac7-1ee4-99fbce796221
token_accessor 	39b5e8b5-7bbf-6c6d-c536-ba79d3a80dd5
token_duration 	768h0m0s
token_renewable	true
token_policies 	[admin default]

Now, fetch the capabilities of this token on sys/auth/approle path.

$ vault capabilities 79ecdd41-9bac-1ac7-1ee4-99fbce796221 sys/auth/approle
Capabilities: [create delete read sudo update]

The result should match the policy rule you wrote on sys/auth/* path. You can repeat the steps to generate a token for provisioner and check its capabilities on paths.

In the absence of token, it returns capabilities of current token invoking this command.

$ vault capabilities sys/auth/approle
Capabilities: [root]

API call using cURL

Use the sys/capabilities endpoint.

Example:

First, create a token attached to admin policy:

$ curl --request POST --header "X-Vault-Token: ..." --data '{ "policies":"admin" }' \
       https://vault.rocks/v1/auth/token/create
{
 "request_id": "870ef38c-1401-7beb-633c-ff09cca3db68",
 "lease_id": "",
 "renewable": false,
 "lease_duration": 0,
 "data": null,
 "wrap_info": null,
 "warnings": null,
 "auth": {
   "client_token": "9f3a9fbb-4e1a-87c3-9d4d-ee4d96d40af1",
   "accessor": "f8a269c0-153a-c1ea-ae97-e7e964814392",
   "policies": [
     "root"
   ],
   "metadata": null,
   "lease_duration": 0,
   "renewable": false,
   "entity_id": ""
 }
}

Now, fetch the capabilities of this token on sys/auth/approle path.

# Request payload
$ cat payload.json
{
  "token": "9f3a9fbb-4e1a-87c3-9d4d-ee4d96d40af1",
  "path": "sys/auth/approle"
}

$ curl --request POST --header "X-Vault-Token: ..." --data @payload.json \
    https://vault.rocks/v1/sys/capabilities
{
  "capabilities": [
    "create",
    "delete",
    "read",
    "sudo",
    "update"
  ],
  "request_id": "03f9d5e2-7e8a-4cd3-b9e9-034c058d3d06",
  "lease_id": "",
  "renewable": false,
  "lease_duration": 0,
  "data": {
    "capabilities": [
      "create",
      "delete",
      "read",
      "sudo",
      "update"
    ]
  },
  "wrap_info": null,
  "warnings": null,
  "auth": null
}

The result should match the policy rule you wrote on sys/auth/* path. You can repeat the steps to generate a token for provisioner and check its capabilities on paths.

To check current token's capabilities permitted on a path, use sys/capabilities-self endpoint.

$ curl --request POST --header "X-Vault-Token: ..." --data '{"path":"sys/auth/approle"}' \
    https://vault.rocks/v1/sys/capabilities-self

Next steps

In this guide, you learned how to write policies based on given policy requirements. Next, AppRole Pull Authentication guide demonstrates how to associate policies to a role.