164 lines
7.4 KiB
Plaintext
164 lines
7.4 KiB
Plaintext
---
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layout: docs
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page_title: Seal/Unseal
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sidebar_title: Seal/Unseal
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description: >-
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A Vault must be unsealed before it can access its data. Likewise, it can be
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sealed to lock it down.
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---
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# Seal/Unseal
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When a Vault server is started, it starts in a _sealed_ state. In this
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state, Vault is configured to know where and how to access the physical
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storage, but doesn't know how to decrypt any of it.
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_Unsealing_ is the process of constructing the master key necessary to
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read the decryption key to decrypt the data, allowing access to the Vault.
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Prior to unsealing, almost no operations are possible with Vault. For
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example authentication, managing the mount tables, etc. are all not possible.
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The only possible operations are to unseal the Vault and check the status
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of the unseal.
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## Why?
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The data stored by Vault is stored encrypted. Vault needs the
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_encryption key_ in order to decrypt the data. The encryption key is
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also stored with the data, but encrypted with another encryption key
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known as the _master key_. The master key isn't stored anywhere.
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Therefore, to decrypt the data, Vault must decrypt the encryption key
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which requires the master key. Unsealing is the process of reconstructing
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this master key.
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Instead of distributing this master key as a single key to an operator,
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Vault uses an algorithm known as
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[Shamir's Secret Sharing](https://en.wikipedia.org/wiki/Shamir%27s_Secret_Sharing)
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to split the key into shards. A certain threshold of shards is required to
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reconstruct the master key.
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This is the _unseal_ process: the shards are added one at a time (in any
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order) until enough shards are present to reconstruct the key and
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decrypt the data.
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## Unsealing
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The unseal process is done by running `vault operator unseal` or via the API.
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This process is stateful: each key can be entered via multiple mechanisms
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on multiple computers and it will work. This allows each shard of the master
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key to be on a distinct machine for better security.
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Once a Vault is unsealed, it remains unsealed until one of two things happens:
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1. It is resealed via the API (see below).
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2. The server is restarted.
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-> **Note:** Unsealing makes the process of automating a Vault install
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difficult. Automated tools can easily install, configure, and start Vault,
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but unsealing it is a very manual process. We have plans in the future to
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make it easier. For the time being, the best method is to manually unseal
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multiple Vault servers in [HA mode](/docs/concepts/ha). Use a tool such
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as Consul to make sure you only query Vault servers that are unsealed.
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## Sealing
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There is also an API to seal the Vault. This will throw away the master
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key and require another unseal process to restore it. Sealing only requires
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a single operator with root privileges.
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This way, if there is a detected intrusion, the Vault data can be locked
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quickly to try to minimize damages. It can't be accessed again without
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access to the master key shards.
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## Auto Unseal
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Auto Unseal was developed to aid in reducing the operational complexity of
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keeping the master key secure. This feature delegates the responsibility of
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securing the master key from users to a trusted device or service. Instead of
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only constructing the key in memory, the master key is encrypted with one of
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these services or devices and then stored in the storage backend allowing Vault
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to decrypt the master key at startup and unseal automatically.
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When using Auto Unseal there are certain operations in Vault that still
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require a quorum of users to perform an operation such as generating a root token.
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During the initialization process, a set of Shamir keys are generated that are called
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Recovery Keys and are used for these operations.
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For a list of examples and supported providers, please see the
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[seal documentation](/docs/configuration/seal).
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## Seal Migration
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The seal can be migrated from Shamir keys to Auto Unseal, Auto Unseal to Shamir
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keys and Auto Unseal to another Auto Unseal.
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~> **NOTE**: The migration operation will require both seals to be available
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during the migration. For example, a migration from a cloud KMS seal to
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Shamir will require that the cloud KMS be accessible during the migration.
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### Migration From Shamir to Auto Unseal
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To migrate from Shamir keys to Auto Unseal, take your server cluster offline and update
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the [seal configuration](/docs/configuration/seal) with the appropriate seal
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configuration. Bring your server back up and leave the rest of the nodes offline if
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using multi-server mode, then run the unseal process with the `-migrate` flag and bring
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the rest of the cluster online.
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All unseal commands must specify the `-migrate` flag. Once the required threshold of
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unseal keys are entered, unseal keys will be migrated to recovery keys.
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```
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$ vault operator unseal -migrate
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```
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### Migration From Auto Unseal to Shamir
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~> **NOTE**: Migration to Shamir seal is not currently supported when using
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Vault Enterprise. We plan to support this officially in a future release.
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To migrate from Auto Unseal to Shamir keys, take your server cluster offline and update
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the [seal configuration](/docs/configuration/seal) and add `disabled = "true"`
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to the seal block. This allows the migration to use this information to decrypt the key
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but will not unseal Vault. When you bring your server back up, run the unseal process
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with the `-migrate` flag and use the Recovery Keys to perform the migration. All unseal
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commands must specify the `-migrate` flag. Once the required threshold of recovery keys
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are entered, the recovery keys will be migrated to be used as unseal keys.
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### Migration From Auto Unseal to Auto Unseal
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~> **NOTE**: Migration between same Auto Unseal types is not currently
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supported. We plan to support this officially in a future release.
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To migrate from Auto Unseal to a different Auto Unseal configuration, take your server
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cluster offline and update the existing [seal configuration](/docs/configuration/seal)
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and add `disabled = "true"` to the seal block. Then add another seal block to describe
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the new seal.
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When you bring your server back up, run the unseal process with the `-migrate` flag and
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use the Recovery Keys to perform the migration. All unseal commands must specify
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the `-migrate` flag. Once the required threshold of recovery keys are entered,
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the recovery keys will be kept and used as recovery keys in the new seal.
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### Migration with Integrated Storage
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Integrated Storage uses the Raft protocol underneath, which requires a quorum of
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servers to be online before the cluster is functional. Therefore, bring the
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cluster back up one node at a time with the seal configuration updated, will not
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work in this case. Follow the same steps for each kind of migration described
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above with the exception that after the cluster is taken offline, update the
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seal configurations of all the nodes appropriately and bring them all back up.
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When the quorum of nodes are back up, Raft will elect a leader and the leader
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node will perform the migration. The migrated information will be replicated to
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all other cluster peers and when the peers eventually become the leader,
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migration will not happen again on the peer nodes.
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## Recovery Key Rekeying
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During Auto Seal initialization process, a set of Shamir keys called Recovery Keys are
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generated which are used for operations that still require a quorum of users.
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Recovery Keys can be rekeyed to change the number of shares or thresholds. When using the
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Vault CLI, this is performed by using the `-target=recovery` flag to `vault operator rekey`.
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