54 lines
2.7 KiB
Markdown
54 lines
2.7 KiB
Markdown
---
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layout: "docs"
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page_title: "Token Authentication"
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sidebar_current: "docs-internals-token"
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description: |-
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Learn about the client token authentication in Vault.
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---
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# Token Authentication
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The `token` authentication backend is built-in and is at the core of
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client authentication. Other authentication backends may be used to
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authenticate a client, but they eventually result in the generation of a client
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token managed by the `token` backend.
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Every token has a number of properties:
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* ID - The primary ID of a token is a randomly generated UUID
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* Display Name - Optionally, a human readable display name
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* Metadata - Metadata used for audit logging
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* Number of Uses - Optionally, a restricted use count
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* Parent ID - Optionally, a parent token which created this child token
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* Policies - An associated list of ACL policies
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* Source Path - The path at which the token was generated (e.g. `auth/github/login`)
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The properties of a token are immutable once created. The exception to this
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is the number of uses, which is decremented on each request. Each of these
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properties enable Vault to do a number of interesting things.
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Each token maintains the source path, or the login path, that was used
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to create the token. This is used to allow source based revocation. For example,
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if we believe our GitHub organization was compromised, we may want to revoke
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all tokens generated via `auth/github/login`. This would be done by using the
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`sys/revoke-prefix/` API with the `auth/github/` prefix. Revoking the
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prefix will revoke all client tokens generated at that path, as well as all
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dynamic secrets generated by those tokens. This provides a powerful "break glass"
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procedure during a potential compromise.
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If a token is created by another authentication backend, they do not have
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a parent token. However, any tokens created by the `auth/token/create` API
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have a parent token, namely the token used to make that request. By maintaining
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this parent-child relationship, Vault models token trees. Child tokens can
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be created with a subset of the parent policies, allowing for dropping of
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privileges. When a token is revoked, the entire sub-tree of tokens is revoked
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with it. This allows clients to safely generate child tokens and then revoke
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them all along with the root.
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Child tokens are very useful, especially when combined with limited use tokens.
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When a token is created, its use count can be optionally specified. Providing
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a use count of one makes a _one time token_. This means the token can be used
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for a single request before being automatically revoked. This can be generalized
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to any number of uses. Limited use tokens cannot be used to create sub-tokens,
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but they can be a powerful way to allow extremely limited access to Vault.
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