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open-vault/website/content/docs/concepts/policies.mdx
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Vault documentation: added info about new policy flag (#16244) 
* added info about new policy flag

* updated wording
2022-07-07 12:54:27 -07:00

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---
layout: docs
page_title: Policies
description: >-
Policies are how authorization is done in Vault, allowing you to restrict
which parts of Vault a user can access.
---
# Policies
Everything in Vault is path-based, and policies are no exception. Policies
provide a declarative way to grant or forbid access to certain paths and
operations in Vault. This section discusses policy workflows and syntaxes.
Policies are **deny by default**, so an empty policy grants no permission in the
system.
## Policy-Authorization Workflow
Before a human or machine can gain access, an administrator must configure Vault
with an [auth method](/docs/concepts/auth). Authentication is
the process by which human or machine-supplied information is verified against
an internal or external system.
Consider the following diagram, which illustrates the steps a security team
would take to configure Vault to authenticate using a corporate LDAP or
ActiveDirectory installation. Even though this example uses LDAP, the concept
applies to all auth methods.
[![Vault Auth Workflow](/img/vault-policy-workflow.svg)](/img/vault-policy-workflow.svg)
1. The security team configures Vault to connect to an auth method.
This configuration varies by auth method. In the case of LDAP, Vault
needs to know the address of the LDAP server and whether to connect using TLS.
It is important to note that Vault does not store a copy of the LDAP database -
Vault will delegate the authentication to the auth method.
1. The security team authors a policy (or uses an existing policy) which grants
access to paths in Vault. Policies are written in HCL in your editor of
preference and saved to disk.
1. The policy's contents are uploaded and stored in Vault and referenced by name.
You can think of the policy's name as a pointer or symlink to its set of rules.
1. Most importantly, the security team maps data in the auth method to a policy.
For example, the security team might create mappings like:
> Members of the OU group "dev" map to the Vault policy named "readonly-dev".
or
> Members of the OU group "ops" map to the Vault policies "admin" and "auditor".
Now Vault has an internal mapping between a backend authentication system and
internal policy. When a user authenticates to Vault, the actual authentication
is delegated to the auth method. As a user, the flow looks like:
[![Vault Auth Workflow](/img/vault-auth-workflow.svg)](/img/vault-auth-workflow.svg)
1. A user attempts to authenticate to Vault using their LDAP credentials,
providing Vault with their LDAP username and password.
1. Vault establishes a connection to LDAP and asks the LDAP server to verify the
given credentials. Assuming this is successful, the LDAP server returns the
information about the user, including the OU groups.
1. Vault maps the result from the LDAP server to policies inside Vault using the
mapping configured by the security team in the previous section. Vault then
generates a token and attaches the matching policies.
1. Vault returns the token to the user. This token has the correct policies
assigned, as dictated by the mapping configuration that was setup by the
security team in advance.
The user then uses this Vault token for future operations. If the user performs
the authentication steps again, they will get a _new_ token. The token will have
the same permissions, but the actual token will be different. Authenticating a
second time does not invalidate the original token.
## Policy Syntax
Policies are written in [HCL][hcl] or JSON and describe which paths in Vault a
user or machine is allowed to access.
[hcl]: https://github.com/hashicorp/hcl
Here is a very simple policy which grants read capabilities to the path
`"secret/foo"`:
```ruby
path "secret/foo" {
capabilities = ["read"]
}
```
When this policy is assigned to a token, the token can read from `"secret/foo"`.
However, the token cannot update or delete `"secret/foo"`, since the
capabilities do not allow it. Because policies are **deny by default**, the
token would have no other access in Vault.
Here is a more detailed policy, and it is documented inline:
```ruby
# This section grants all access on "secret/*". Further restrictions can be
# applied to this broad policy, as shown below.
path "secret/*" {
capabilities = ["create", "read", "update", "patch", "delete", "list"]
}
# Even though we allowed secret/*, this line explicitly denies
# secret/super-secret. This takes precedence.
path "secret/super-secret" {
capabilities = ["deny"]
}
# Policies can also specify allowed, disallowed, and required parameters. Here
# the key "secret/restricted" can only contain "foo" (any value) and "bar" (one
# of "zip" or "zap").
path "secret/restricted" {
capabilities = ["create"]
allowed_parameters = {
"foo" = []
"bar" = ["zip", "zap"]
}
}
```
Policies use path-based matching to test the set of capabilities against a
request. A policy `path` may specify an exact path to match, or it could specify
a glob pattern which instructs Vault to use a prefix match:
```ruby
# Permit reading only "secret/foo". An attached token cannot read "secret/food"
# or "secret/foo/bar".
path "secret/foo" {
capabilities = ["read"]
}
# Permit reading everything under "secret/bar". An attached token could read
# "secret/bar/zip", "secret/bar/zip/zap", but not "secret/bars/zip".
path "secret/bar/*" {
capabilities = ["read"]
}
# Permit reading everything prefixed with "zip-". An attached token could read
# "secret/zip-zap" or "secret/zip-zap/zong", but not "secret/zip/zap
path "secret/zip-*" {
capabilities = ["read"]
}
```
In addition, a `+` can be used to denote any number of characters bounded
within a single path segment (this appeared in Vault 1.1):
```ruby
# Permit reading the "teamb" path under any top-level path under secret/
path "secret/+/teamb" {
capabilities = ["read"]
}
# Permit reading secret/foo/bar/teamb, secret/bar/foo/teamb, etc.
path "secret/+/+/teamb" {
capabilities = ["read"]
}
```
Vault's architecture is similar to a filesystem. Every action in Vault has a
corresponding path and capability - even Vault's internal core configuration
endpoints live under the `"sys/"` path. Policies define access to these paths and
capabilities, which controls a token's access to credentials in Vault.
~> **Note:** The policy rules that Vault applies are determined by the most-specific match
available, using the priority rules described below. This may be an exact match
or the longest-prefix match of a glob. If the same pattern appears in multiple
policies, we take the union of the capabilities. If different patterns appear in
the applicable policies, we take only the highest-priority match from those
policies.
This means if you define a policy for `"secret/foo*"`, the policy would
also match `"secret/foobar"`. Specifically, when there are potentially multiple
matching policy paths, `P1` and `P2`, the following matching criteria is applied:
1. If the first wildcard (`+`) or glob (`*`) occurs earlier in `P1`, `P1` is lower priority
2. If `P1` ends in `*` and `P2` doesn't, `P1` is lower priority
3. If `P1` has more `+` (wildcard) segments, `P1` is lower priority
4. If `P1` is shorter, it is lower priority
5. If `P1` is smaller lexicographically, it is lower priority
For example, given the two paths, `"secret/*"` and `"secret/+/+/foo/*"`, the first
wildcard appears in the same place, both end in `*` and the latter has two wildcard
segments while the former has zero. So we end at rule (3), and give `"secret/+/+/foo/*"`
_lower_ priority.
!> **Informational:**The glob character referred to in this documentation is the asterisk (`*`).
It _is not a regular expression_ and is only supported **as the last character of the path**!
When providing `list` capability, it is important to note that since listing
always operates on a prefix, policies must operate on a prefix because Vault
will sanitize request paths to be prefixes.
### Capabilities
Each path must define one or more capabilities which provide fine-grained
control over permitted (or denied) operations. As shown in the examples above,
capabilities are always specified as a list of strings, even if there is only
one capability.
To determine the capabilities needed to perform a specific operation, the `-output-policy` flag can be added to the CLI subcommand. For an example, refer to the [Print Policy Requirements](/docs/commands#print-policy-requirements) document section.
The list of capabilities include the following:
- `create` (`POST/PUT`) - Allows creating data at the given path. Very few
parts of Vault distinguish between `create` and `update`, so most operations
require both `create` and `update` capabilities. Parts of Vault that
provide such a distinction are noted in documentation.
- `read` (`GET`) - Allows reading the data at the given path.
- `update` (`POST/PUT`) - Allows changing the data at the given path. In most
parts of Vault, this implicitly includes the ability to create the initial
value at the path.
- `patch` (`PATCH`) - Allows partial updates to the data at a given path.
- `delete` (`DELETE`) - Allows deleting the data at the given path.
- `list` (`LIST`) - Allows listing values at the given path. Note that the
keys returned by a `list` operation are _not_ filtered by policies. Do not
encode sensitive information in key names. Not all backends support listing.
In the list above, the associated HTTP verbs are shown in parenthesis next to
the capability. When authoring policy, it is usually helpful to look at the HTTP
API documentation for the paths and HTTP verbs and map them back onto
capabilities. While the mapping is not strictly 1:1, they are often very
similarly matched.
In addition to the standard set, there are some capabilities that do not map to
HTTP verbs.
- `sudo` - Allows access to paths that are _root-protected_. Tokens are not
permitted to interact with these paths unless they have the `sudo`
capability (in addition to the other necessary capabilities for performing
an operation against that path, such as `read` or `delete`).
For example, modifying the audit log backends requires a token with `sudo`
privileges.
- `deny` - Disallows access. This always takes precedence regardless of any
other defined capabilities, including `sudo`.
~> **Note:** Capabilities usually map to the HTTP verb, and not the underlying
action taken. This can be a common source of confusion. Generating database
credentials _creates_ database credentials, but the HTTP request is a GET which
corresponds to a `read` capability. Thus, to grant access to generate database
credentials, the policy would grant `read` access on the appropriate path.
## Templated Policies
The policy syntax allows for doing variable replacement in some policy strings
with values available to the token. Currently `identity` information can be
injected, and currently the `path` keys in policies allow injection.
### Parameters
| Name | Description |
| :------------------------------------------------------------------------------- | :------------------------------------------------------------------------------------- |
| `identity.entity.id` | The entity's ID |
| `identity.entity.name` | The entity's name |
| `identity.entity.metadata.<metadata key>` | Metadata associated with the entity for the given key |
| `identity.entity.aliases.<mount accessor>.id` | Entity alias ID for the given mount |
| `identity.entity.aliases.<mount accessor>.name` | Entity alias name for the given mount |
| `identity.entity.aliases.<mount accessor>.metadata.<metadata key>` | Metadata associated with the alias for the given mount and metadata key |
| `identity.entity.aliases.<mount accessor>.custom_metadata.<custom_metadata key>` | Custom metadata associated with the alias for the given mount and custom metadata key |
| `identity.groups.ids.<group id>.name` | The group name for the given group ID |
| `identity.groups.names.<group name>.id` | The group ID for the given group name |
| `identity.groups.ids.<group id>.metadata.<metadata key>` | Metadata associated with the group for the given key |
| `identity.groups.names.<group name>.metadata.<metadata key>` | Metadata associated with the group for the given key |
### Examples
The following policy creates a section of the KVv2 Secret Engine to a specific user
```ruby
path "secret/data/{{identity.entity.id}}/*" {
capabilities = ["create", "update", "patch", "read", "delete"]
}
path "secret/metadata/{{identity.entity.id}}/*" {
capabilities = ["list"]
}
```
If you wanted to create a shared section of KV that is associated with entities that are in a
group.
```ruby
# In the example below, the group ID maps a group and the path
path "secret/data/groups/{{identity.groups.ids.fb036ebc-2f62-4124-9503-42aa7A869741.name}}/*" {
capabilities = ["create", "update", "patch", "read", "delete"]
}
path "secret/metadata/groups/{{identity.groups.ids.fb036ebc-2f62-4124-9503-42aa7A869741.name}}/*" {
capabilities = ["list"]
}
```
~> **Note:** When developing templated policies, use IDs wherever possible. Each ID is
unique to the user, whereas names can change over time and can be reused. This
ensures that if a given user or group name is changed, the policy will be
mapped to the intended entity or group.
If you want to use the metadata associated with an authentication plugin in your
templates, you will need to get its _mount accessor_ and access it via the
`aliases` key.
You can get the mount accessor value using the following command:
```shellsession
$> vault auth list
Path Type Accessor Description
---- ---- -------- -----------
kubernetes/ kubernetes auth_kubernetes_xxxx n/a
token/ token auth_token_yyyy token based credentials
```
The following templated policy allow to read the path associated with the
Kubernetes service account namespace of the identity:
```ruby
path "secret/data/{{identity.entity.aliases.auth_kubernetes_xxxx.metadata.service_account_namespace}}/*" {
capabilities = ["read"]
}
```
## Fine-Grained Control
In addition to the standard set of capabilities, Vault offers finer-grained
control over permissions at a given path. The capabilities associated with a
path take precedence over permissions on parameters.
### Parameter Constraints
~> **Note:**: The `allowed_parameters`, `denied_parameters`, and `required_parameters` fields are not supported for policies used with the version 2 kv store.
See the [API Specification](/api-docs/secret/kv/kv-v2) for more information.
Policies can take into account HTTP request parameters to further
constrain requests, using the following options:
- `required_parameters` - A list of parameters that must be specified.
```ruby
# This requires the user to create "secret/foo" with a parameter named
# "bar" and "baz".
path "secret/foo" {
capabilities = ["create"]
required_parameters = ["bar", "baz"]
}
```
- `allowed_parameters` - A list of keys and values that are
permitted on the given path.
- Setting a parameter with a value of the empty list allows the parameter to
contain any value.
```ruby
# This allows the user to create "secret/foo" with a parameter named
# "bar". It cannot contain any other parameters, but "bar" can contain
# any value.
path "secret/foo" {
capabilities = ["create"]
allowed_parameters = {
"bar" = []
}
}
```
- Setting a parameter with a value of a populated list allows the parameter
to contain only those values.
```ruby
# This allows the user to create "secret/foo" with a parameter named
# "bar". It cannot contain any other parameters, and "bar" can only
# contain the values "zip" or "zap".
path "secret/foo" {
capabilities = ["create"]
allowed_parameters = {
"bar" = ["zip", "zap"]
}
}
```
- If any keys are specified, all non-specified parameters will be denied
unless the parameter `"*"` is set to an empty array, which will
allow all other parameters to be modified. Parameters with specific values
will still be restricted to those values.
```ruby
# This allows the user to create "secret/foo" with a parameter named
# "bar". The parameter "bar" can only contain the values "zip" or "zap",
# but any other parameters may be created with any value.
path "secret/foo" {
capabilities = ["create"]
allowed_parameters = {
"bar" = ["zip", "zap"]
"*" = []
}
}
```
- It's important to note that the use of globbing may result in surprising
or unexpected behavior.
```ruby
# This allows the user to create, update, or patch "secret/foo" with a parameter
# named "bar". The values passed to parameter "bar" must start with "baz/"
# so values like "baz/quux" are fine. However, values like
# "baz/quux,wibble,wobble,wubble" would also be accepted. The API that
# underlies "secret/foo" might allow comma delimited values for the "bar"
# parameter, and if it did, specifying a value like
# "baz/quux,wibble,wobble,wubble" would result in 4 different values getting
# passed along. Seeing values like "wibble" or "wobble" getting passed to
# "secret/foo" might surprise someone that expected the allowed_parameters
# constraint to only allow values starting with "baz/".
path "secret/foo" {
capabilities = ["create", "update", "patch"]
allowed_parameters = {
"bar" = ["baz/*"]
}
}
```
- `denied_parameters` - Blacklists a list of parameter and values. Any values
specified here take precedence over `allowed_parameters`.
- Setting a parameter with a value of the empty list denies any changes to
that parameter.
```ruby
# This allows the user to create "secret/foo" with any parameters not
# named "bar".
path "secret/foo" {
capabilities = ["create"]
denied_parameters = {
"bar" = []
}
}
```
- Setting a parameter with a value of a populated list denies any parameter
containing those values.
```ruby
# This allows the user to create "secret/foo" with a parameter named
# "bar". It can contain any other parameters, but "bar" cannot contain
# the values "zip" or "zap".
path "secret/foo" {
capabilities = ["create"]
denied_parameters = {
"bar" = ["zip", "zap"]
}
}
```
- Setting to `"*"` will deny any parameter.
```ruby
# This allows the user to create "secret/foo", but it cannot have any
# parameters.
path "secret/foo" {
capabilities = ["create"]
denied_parameters = {
"*" = []
}
}
```
- If any parameters are specified, all non-specified parameters are allowed,
unless `allowed_parameters` is also set, in which case normal rules apply.
Parameter values also support prefix/suffix globbing. Globbing is enabled by
prepending or appending or prepending a splat (`*`) to the value:
```ruby
# Only allow a parameter named "bar" with a value starting with "foo-*".
path "secret/foo" {
capabilities = ["create"]
allowed_parameters = {
"bar" = ["foo-*"]
}
}
```
~> **Note:** the only value that can be used with the `*` parameter is `[]`.
### Required Response Wrapping TTLs
These parameters can be used to set minimums/maximums on TTLs set by clients
when requesting that a response be
[wrapped](/docs/concepts/response-wrapping), with a granularity of a
second. These use [duration format strings](/docs/concepts/duration-format).
In practice, setting a minimum TTL of one second effectively makes response
wrapping mandatory for a particular path.
- `min_wrapping_ttl` - The minimum allowed TTL that clients can specify for a
wrapped response. In practice, setting a minimum TTL of one second
effectively makes response wrapping mandatory for a particular path. It can
also be used to ensure that the TTL is not too low, leading to end targets
being unable to unwrap before the token expires.
- `max_wrapping_ttl` - The maximum allowed TTL that clients can specify for a
wrapped response.
```ruby
# This effectively makes response wrapping mandatory for this path by setting min_wrapping_ttl to 1 second.
# This also sets this path's wrapped response maximum allowed TTL to 90 seconds.
path "auth/approle/role/my-role/secret-id" {
capabilities = ["create", "update"]
min_wrapping_ttl = "1s"
max_wrapping_ttl = "90s"
}
```
If both are specified, the minimum value must be less than the maximum. In
addition, if paths are merged from different stanzas, the lowest value
specified for each is the value that will result, in line with the idea of
keeping token lifetimes as short as possible.
## Built-in Policies
Vault has two built-in policies: `default` and `root`. This section describes
the two builtin policies.
### Default Policy
The `default` policy is a built-in Vault policy that cannot be removed. By
default, it is attached to all tokens, but may be explicitly excluded at token
creation time by supporting authentication methods.
The policy contains basic functionality such as the ability for the token to
look up data about itself and to use its cubbyhole data. However, Vault is not
prescriptive about its contents. It can be modified to suit your needs; Vault
will never overwrite your modifications. If you want to stay up-to-date with
the latest upstream version of the `default` policy, simply read the contents
of the policy from an up-to-date `dev` server, and write those contents into
your Vault's `default` policy.
To view all permissions granted by the default policy on your Vault
installation, run:
```shell-session
$ vault read sys/policy/default
```
To disable attachment of the default policy:
```shell-session
$ vault token create -no-default-policy
```
or via the API:
```shell-session
$ curl \
--request POST \
--header "X-Vault-Token: ..." \
--data '{"no_default_policy": "true"}' \
https://vault.hashicorp.rocks/v1/auth/token/create
```
### Root Policy
The `root` policy is a built-in Vault policy that can not be modified or removed.
Any user associated with this policy becomes a root user. A root user can do
_anything_ within Vault. As such, it is **highly recommended** that you revoke
any root tokens before running Vault in production.
When a Vault server is first initialized, there always exists one root user.
This user is used to do the initial configuration and setup of Vault. After
configured, the initial root token should be revoked and more strictly
controlled users and authentication should be used.
To revoke a root token, run:
```shell-session
$ vault token revoke "<token>"
```
or via the API:
```shell-session
$ curl \
--request POST \
--header "X-Vault-Token: ..." \
--data '{"token": "<token>"}' \
https://vault.hashicorp.rocks/v1/auth/token/revoke
```
For more information, please read:
- [Production Hardening](/guides/operations/production)
- [Generating a Root Token](/guides/operations/generate-root)
## Managing Policies
Policies are authored (written) in your editor of choice. They can be authored
in HCL or JSON, and the syntax is described in detail above. Once saved,
policies must be uploaded to Vault before they can be used.
### Listing Policies
To list all registered policies in Vault:
```shell-session
$ vault read sys/policy
```
or via the API:
```shell-session
$ curl \
--header "X-Vault-Token: ..." \
https://vault.hashicorp.rocks/v1/sys/policy
```
~> **Note:** You may also see the CLI command `vault policies`. This is a convenience
wrapper around reading the sys endpoint directly. It provides the same
functionality but formats the output in a special manner.
### Creating Policies
Policies may be created (uploaded) via the CLI or via the API. To create a new
policy in Vault:
```shell-session
$ vault policy write policy-name policy-file.hcl
```
or via the API:
```shell-session
$ curl \
--request POST \
--header "X-Vault-Token: ..." \
--data '{"policy":"path \"...\" {...} "}' \
https://vault.hashicorp.rocks/v1/sys/policy/policy-name
```
In both examples, the name of the policy is "policy-name". You can think of this
name as a pointer or symlink to the policy ACLs. Tokens are attached policies by
name, which are then mapped to the set of rules corresponding to that name.
### Updating Policies
Existing policies may be updated to change permissions via the CLI or via the
API. To update an existing policy in Vault, follow the same steps as creating a
policy, but use an existing policy name:
```shell-session
$ vault write sys/policy/my-existing-policy policy=@updated-policy.json
```
or via the API:
```shell-session
$ curl \
--request POST \
--header "X-Vault-Token: ..." \
--data '{"policy":"path \"...\" {...} "}' \
https://vault.hashicorp.rocks/v1/sys/policy/my-existing-policy
```
### Deleting Policies
Existing policies may be deleted via the CLI or API. To delete a policy:
```shell-session
$ vault delete sys/policy/policy-name
```
or via the API:
```shell-session
$ curl \
--request DELETE \
--header "X-Vault-Token: ..." \
https://vault.hashicorp.rocks/v1/sys/policy/policy-name
```
This is an idempotent operation. Vault will not return an error when deleting a
policy that does not exist.
## Associating Policies
Vault can automatically associate a set of policies to a token based on an
authorization. This configuration varies significantly between authentication
backends. For simplicity, this example will use Vault's built-in userpass
auth method.
A Vault administrator or someone from the security team would create the user in
Vault with a list of associated policies:
```shell-session
$ vault write auth/userpass/users/sethvargo \
password="s3cr3t!" \
policies="dev-readonly,logs"
```
This creates an authentication mapping to the policy such that, when the user
authenticates successfully to Vault, they will be given a token which has the list
of policies attached.
The user wishing to authenticate would run
```shell-session
$ vault login -method="userpass" username="sethvargo"
Password (will be hidden): ...
```
If the provided information is correct, Vault will generate a token, assign the
list of configured policies to the token, and return that token to the
authenticated user.
### Tokens
Tokens have two sets of policies: identity policies, which are computed
based on the entity and its groups, and token policies, which are either defined
based on the login method or, in the case of explicit token creates via the API,
are an input to the token creation. What follows concerns token policies
exclusively: a token's identity policies cannot be controlled except by modifying
the underlying entities, groups, and group memberships.
Tokens are associated with their policies at creation time. For example:
```shell-session
$ vault token create -policy=dev-readonly -policy=logs
```
Normally the only policies that may be specified are those which are present
in the current token's (i.e. the new token's parent's) token policies.
However, root users can assign any policies.
There is no way to modify the policies associated with a token once the token
has been issued. The token must be revoked and a new one acquired to receive a
new set of policies.
However, the _contents_ of policies are parsed in real-time whenever the token is used.
As a result, if a policy is modified, the modified rules will be in force the
next time a token, with that policy attached, is used to make a call to Vault.
## Tutorial
Refer to the following tutorials for further learning:
- [Vault Policies](https://learn.hashicorp.com/vault/identity-access-management/iam-policies)
- [ACL Policy Path Templating](https://learn.hashicorp.com/vault/identity-access-management/policy-templating)
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