108 lines
3.6 KiB
Markdown
108 lines
3.6 KiB
Markdown
---
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layout: "docs"
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page_title: "Audit Backends"
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sidebar_current: "docs-audit"
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description: |-
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Audit backends are mountable backends that log requests and responses in Vault.
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---
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# Audit Backends
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Audit backends are the components in Vault that keep a detailed log
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of all requests and response to Vault. Because _every_ operation with
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Vault is an API request/response, the audit log contains _every_ interaction
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with Vault, including errors.
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Vault ships with multiple audit backends, depending on the location you want
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the logs sent to. Multiple audit backends can be enabled and Vault will send
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the audit logs to both. This allows you to not only have a redundant copy,
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but also a second copy in case the first is tampered with.
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## Sensitive Information
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The audit logs contain the full request and response objects for every
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interaction with Vault. The request and response can be matched utilizing a
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unique identifier assigned to each request. The data in the request and the
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data in the response (including secrets and authentication tokens) will be
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hashed with a salt using HMAC-SHA256.
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The purpose of the hash is so that secrets aren't in plaintext within your
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audit logs. However, you're still able to check the value of secrets by
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generating HMACs yourself; this can be done with the audit backend's hash
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function and salt by using the `/sys/audit-hash` API endpoint (see the
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documentation for more details).
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## Enabling/Disabling Audit Backends
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When a Vault server is first initialized, no auditing is enabled. Audit
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backends must be enabled by a root user using `vault audit-enable`.
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When enabling an audit backend, options can be passed to it to configure it.
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For example, the command below enables the file audit backend:
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```
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$ vault audit-enable file file_path=/var/log/vault_audit.log
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...
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```
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In the command above, we passed the "file_path" parameter to specify the path
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where the audit log will be written to. Each audit backend has its own
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set of parameters. See the documentation to the left for more details.
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When an audit backend is disabled, it will stop receiving logs immediately.
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The existing logs that it did store are untouched.
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## Blocked Audit Backends
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If there are any audit backends enabled, Vault requires that at least
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one be able to persist the log before completing a Vault request.
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If you have only one audit backend enabled, and it is blocking (network
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block, etc.), then Vault will be _unresponsive_. Vault _will not_ complete
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any requests until the audit backend can write.
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If you have more than one audit backend, then Vault will complete the request
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as long as one audit backend persists the log.
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Vault will not respond to requests if audit backends are blocked because
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audit logs are critically important and ignoring blocked requests opens
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an avenue for attack. Be absolutely certain that your audit backends cannot
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block.
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## API
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### /sys/audit/[path]
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#### POST
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<dl class="api">
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<dt>Description</dt>
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<dd>
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Enables audit backend at the specified path.
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</dd>
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<dt>Method</dt>
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<dd>POST</dd>
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<dd>
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<ul>
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<li>
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<span class="param">type</span>
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<span class="param-flags">required</span>
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The path to where the audit log will be written. If this
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path exists, the audit backend will append to it.
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</li>
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<li>
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<span class="param">description</span>
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<span class="param-flags">optional</span>
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A description.
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</li>
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<li>
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<span class="param">options</span>
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<span class="param-flags">optional</span>
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Configuration options of the backend in JSON format.
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Refer to `syslog` and `file` audit backend options.
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</li>
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</ul>
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</dd>
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</dl>
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