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Vault documentation: created new identity concepts page (hashicorp#12825
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* created draft PR for identity doc

* relocated identity page

* fixed error in side nav

* Fix table format

* Add Learn tutorial link

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* Removed duplicated description about entity (hashicorp#12861)

Co-authored-by: Yoko Hyakuna <yoko@hashicorp.com>
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---
layout: docs
page_title: 'Identity'
description: >-
Vault provides an identify management solution to maintain clients who are recognized by Vault.
---

# Identity

This document contains conceptual information about **Identity** along with an
overview of the various terminologies and their concepts. The idea of Identity
is to maintain the clients who are recognized by Vault. As such, Vault provides
an identity management solution through the **Identity secrets engine**. For
more information about the Identify secrets engine and how it is used, refer to
the [Identify Secrets Engine](/docs/secrets/identity) documentation.

## Entities and Aliases

Each user may have multiple accounts with various identity providers, and Vault
supports many of those providers to authenticate with Vault. Vault Identity can
tie authentications from various auth methods to a single representation. This representation of a consolidated identity is called an **Entity** and their
corresponding accounts with authentication providers can be mapped as
**Aliases**. In essence, each entity is made up of zero or more aliases.

For example, a user with accounts in both GitHub and LDAP can be mapped to a
single entity in Vault with two aliases, one of type GitHub and one of type
LDAP.

![Entity overview](/img/vault-identity-doc-1.png)

When a client authenticates via any credential backend (except the Token
backend), Vault creates a new entity. It attaches a new alias to it if a
corresponding entity does not already exist. The entity identifier will be tied
to the authenticated token. When such tokens are used, their entity identifiers
are audit logged, marking a trail of actions performed by specific users.

~> Vault Entity is used to count the number of Vault clients. To learn more
about client count, refer to the [Client Count](/docs/concepts/client-count)
documentation.

## Entity Management

Entities in Vault **do not** automatically pull identity information from
anywhere. It needs to be explicitly managed by operators. This way, it is
flexible in terms of administratively controlling the number of entities to be
synced against Vault. In some sense, Vault will serve as a _cache_ of
identities and not as a _source_ of identities.

## Entity Policies

Vault policies can be assigned to entities which will grant _additional_
permissions to the token on top of the existing policies on the token. If the
token presented on the API request contains an identifier for the entity and if
that entity has a set of policies on it, then the token will be capable of
performing actions allowed by the policies on the entity as well.

![Entity policies](/img/vault-identity-doc-2.png)

This is a paradigm shift in terms of _when_ the policies of the token get
evaluated. Before identity, the policy names on the token were immutable (not
the contents of those policies though). But with entity policies, along with
the immutable set of policy names on the token, the evaluation of policies
applicable to the token through its identity will happen at request time. This
also adds enormous flexibility to control the behavior of already issued
tokens.

It is important to note that the policies on the entity are only a means to grant
_additional_ capabilities and not a replacement for the policies on the token.
To know the full set of capabilities of the token with an associated entity
identifier, the policies on the token should be taken into account.

~> **NOTE:** Be careful in granting permissions to non-readonly identity endpoints.
If a user can modify an entity, they can grant it additional privileges through
policies. If a user can modify an alias they can login with, they can bind it to
an entity with higher privileges. If a user can modify group membership, they
can add their entity to a group with higher privileges.


## Mount Bound Aliases

Vault supports multiple authentication backends and also allows enabling the
same type of authentication backend on different mount paths. The alias name of
the user will be unique within the backend's mount. But identity store needs to
uniquely distinguish between conflicting alias names across different mounts of
these identity providers. Hence, the alias name in combination with the
authentication backend mount's accessor, serve as the unique identifier of an
alias.

The table below shows what information each of the supported auth methods uses
to form the alias name. This is the identifying information that is used to match or create
an entity. If no entities are explicitly created or merged, then one [entity will be implicitly created](#implicit-entities)
for each object on the right-hand side of the table, when it is used to authenticate on
a particular auth mount point.

| Auth method | Name reported by auth method |
| ------------------- | ------------------------------------------------------------------------------------ |
| AliCloud | Principal ID |
| AppRole | Role ID |
| AWS IAM | Configurable via `iam_alias` to one of: Role ID (default), IAM unique ID, Full ARN |
| AWS EC2 | Configurable via `ec2_alias` to one of: Role ID (default), EC2 instance ID, AMI ID |
| Azure | Subject (from JWT claim) |
| Cloud Foundry | App ID |
| GitHub | User login name associated with token |
| Google Cloud | Configurable via `iam_alias` to one of: Role ID (default), Service account unique ID |
| JWT/OIDC | Configurable via `user_claim` to one of the presented claims (no default value) |
| Kerberos | Username |
| Kubernetes | Service account UID |
| LDAP | Username |
| OCI | Role name |
| Okta | Username |
| RADIUS | Username |
| TLS Certificate | Subject CommonName |
| Token | `entity_alias`, if provided |
| Username (userpass) | Username |

## Local Auth Methods

**Vault Enterpris:** If a login is performed using an auth method that was
mounted locally (using `local=true`), no entities or groups will be associated
with the resulting token.

## Implicit Entities

Operators can create entities for all the users of an auth mount beforehand and
assign policies to them, so that when users login, the desired capabilities to
the tokens via entities are already assigned. But if that's not done, upon a
successful user login from any of the authentication backends, Vault will
create a new entity and assign an alias against the login that was successful.

Note that the tokens created using the token authentication backend will not
normally have any associated identity information. An existing or new implicit
entity can be assigned by using the `entity_alias` parameter, when creating a
token using a token role with a configured list of `allowed_entity_aliases`.

## Identity Auditing

If the token used to make API calls has an associated entity identifier, it
will be audit logged as well. This leaves a trail of actions performed by
specific users.

## Identity Groups

Vault identity has support for **groups**. A group can contain multiple entities
as its members. A group can also have subgroups. Policies set on the group are
granted to all members of the group. During request time, when the token's
entity ID is being evaluated for the policies that it has access to, policies
that are inherited due to group memberships are granted along with the policies
on the entity itself.

![Identity overview](/img/vault-identity-doc-3.png)

## Group Hierarchical Permissions

Entities can be direct members of groups, in which case they inherit the
policies of the groups they belong to. Entities can also be indirect members of
groups. For example, if a GroupA has GroupB as subgroup, then members of GroupB
are indirect members of GroupA. Hence, the members of GroupB will have access
to policies on both GroupA and GroupB.

## External vs Internal Groups

By default, the groups created in identity store are called the internal
groups. The membership management of these groups should be carried out
manually. A group can also be created as an external group. In this case, the
entity membership in the group is managed semi-automatically. An external group
serves as a mapping to a group that is outside of the identity store. External
groups can have one (and only one) alias. This alias should map to a notion of
a group that is outside of the identity store. For example, groups in LDAP and
teams in GitHub. A username in LDAP belonging to a group in LDAP can get its
entity ID added as a member of a group in Vault automatically during _logins_
and _token renewals_. This works only if the group in Vault is an external
group and has an alias that maps to the group in LDAP. If the user is removed
from the group in LDAP, that change gets reflected in Vault only upon the
subsequent login or renewal operation.

For information about Identity Secrets Engine, refer to [Identity Secrets Engine](/docs/secrets/identity).


## Learn

Refer to the [Identity: Entities and
Groups](https://learn.hashicorp.com/tutorials/vault/identity) tutorial for a
step-by-step tutorial.

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