open-vault/website/source/docs/concepts/policies.html.md

layout	page_title	sidebar_current	description
docs	Policies	docs-concepts-policies	Policies are how authorization is done in Vault, allowing you to restrict which parts of Vault a user can access.

Access Control Policies

After authenticating with Vault, the next step is authorization. This is the process of determining what a user is allowed to do. Authorization is unified in Vault in the form of policies.

Policies are HCL or JSON documents that describe what parts of Vault a user is allowed to access. An example of a policy is shown below:

path "sys/*" {
  policy = "deny"
}

path "secret/*" {
  policy = "write"
}

path "secret/foo" {
  policy = "read"
  capabilities = ["create", "sudo"]
}

path "secret/super-secret" {
  capabilities = ["deny"]
}

Policies use path based matching to apply rules. A policy may be an exact match, or might be a glob pattern which uses a prefix. Vault operates in a whitelisting mode, so if a path isn't explicitly allowed, Vault will reject access to it. This works well due to Vault's architecture of being like a filesystem: everything has a path associated with it, including the core configuration mechanism under "sys".

~> Policy paths are matched using the most specific defined policy. This may be an exact match or the longest-prefix match of a glob. This means if you define a policy for "secret/foo*", the policy would also match "secret/foobar". The glob character is only supported at the end of the path specification.

Capabilities and Policies

Paths have an associated set of capabilities that provide fine-grained control over operations. The capabilities are:

• create - Create a value at a path. (At present, few parts of Vault distinguish between create and update, so most operations require update. Parts of Vault that provide such a distinction, such as the generic backend, are noted in documentation.)

• read - Read the value at a path.

• update - Change the value at a path. In most parts of Vault, this also includes the ability to create the initial value at the path.

• delete - Delete the value at a path.

• list - List values at a path.

• sudo - Gain access to paths that are root-protected. This is additive to other capabilities, so a path that requires sudo access will also require read, update, etc. as appropriate.

• deny - No access allowed. This always takes precedence regardless of any other defined capabilities, including sudo.

The only non-obvious capability is sudo. Some routes within Vault and mounted backends are marked as root-protected paths. Clients aren't allowed to access root paths unless they are a root user (have the special policy "root" attached to their token) or have access to that path with 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 is done via root paths. Only root or sudo privilege users are allowed to do this.

Prior to Vault 0.5, the policy keyword was used per path rather than a set of capabilities. In Vault 0.5+ these are still supported as shorthand and to maintain backwards compatibility, but internally they map to a set of capabilities. These mappings are as follows:

• deny - ["deny"]

• sudo - ["create", "read", "update", "delete", "list", "sudo"]

• write - ["create", "read", "update", "delete", "list"]

• read - ["read", "list"]

Root Policy

The "root" policy is a special policy that can not be modified or removed. Any user associated with the "root" policy becomes a root user. A root user can do anything within Vault.

There always exists at least one root user (associated with the token when initializing a new server). After this root user, it is recommended to create more strictly controlled users. The original root token should be protected accordingly.

Managing Policies

Policy management can be done via the API or CLI. The CLI commands are vault policies and vault policy-write. Please see the help associated with these commands for more information. They are very easy to use.

Associating Policies

To associate a policy with a user, you must consult the documentation for the authentication backend you're using.

For tokens, they are associated at creation time with vault token-create and the -policy flags. Child tokens can be associated with a subset of a parent's policies. Root users can assign any policies.

There is no way to modify the policies associated with an active identity. The identity must be revoked and reauthenticated to receive the new policy list.

If an existing policy is modified, the modifications propagate to all associated users instantly. The above paragraph is more specifically stating that you can't add new or remove policies associated with an active identity.

Changes from 0.1

In Vault versions prior to 0.2, the ACL policy language had a slightly different specification and semantics. The current specification requires that glob behavior explicitly be specified by adding the * character to the end of a path. Previously, all paths were glob based matches and no exact match could be specified.

The other change is that deny had the lowest precedence. This meant if there were two policies being merged (e.g. "ops" and "prod") and they had a conflicting policy like:

path "sys/seal" {
    policy = "deny"
}

path "sys/seal" {
    policy = "read"
}

The merge would previously give the "read" higher precedence. The current version of Vault prioritizes the explicit deny, so that the "deny" would take precedence.

To make all Vault 0.1 policies compatible with Vault 0.2+, the explicit glob character must be added to all the path prefixes.