128 lines
4.6 KiB
Markdown
128 lines
4.6 KiB
Markdown
---
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layout: "docs"
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page_title: "Auth Backend: TLS Certificates"
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sidebar_current: "docs-auth-cert"
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description: |-
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The "cert" auth backend allows users to authenticate with Vault using TLS client certificates.
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---
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# Auth Backend: TLS Certificates
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Name: `cert`
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The "cert" auth backend allows authentication using SSL/TLS client certificates
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which are either signed by a CA or self-signed.
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The trusted certificates and CAs are configured directly to the auth backend
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using the `certs/` path. This backend cannot read trusted certificates from an
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external source.
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CA certs are associated with a role; role names and CRL names are normalized to
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lower-case.
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## Revocation Checking
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Since Vault 0.4, the backend supports revocation checking.
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An authorised user can submit PEM-formatted CRLs identified by a given name;
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these can be updated or deleted at will. (Note: Vault **does not** fetch CRLs;
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the CRLs themselves and any updates must be pushed into Vault when desired,
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such as via a `cron` job that fetches them from the source and pushes them into
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Vault.)
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When there are CRLs present, at the time of client authentication:
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* If the client presents any chain where no certificate in the chain matches a
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revoked serial number, authentication is allowed
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* If there is no chain presented by the client without a revoked serial number,
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authentication is denied
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This method provides good security while also allowing for flexibility. For
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instance, if an intermediate CA is going to be retired, a client can be
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configured with two certificate chains: one that contains the initial
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intermediate CA in the path, and the other that contains the replacement. When
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the initial intermediate CA is revoked, the chain containing the replacement
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will still allow the client to successfully authenticate.
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**N.B.**: Matching is performed by *serial number only*. For most CAs,
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including Vault's `pki` backend, multiple CRLs can successfully be used as
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serial numbers are globally unique. However, since RFCs only specify that
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serial numbers must be unique per-CA, some CAs issue serial numbers in-order,
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which may cause clashes if attempting to use CRLs from two such CAs in the same
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mount of the backend. The workaround here is to mount multiple copies of the
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`cert` backend, configure each with one CA/CRL, and have clients connect to the
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appropriate mount.
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In addition, since the backend does not fetch the CRLs itself, the CRL's
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designated time to next update is not considered. If a CRL is no longer in use,
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it is up to the administrator to remove it from the backend.
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## Authentication
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### Via the CLI
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The below requires Vault to present a certificate signed by `ca.pem` and
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presents `cert.pem` (using `key.pem`) to authenticate against the `web` cert
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role. If a certificate role name is not specified, the auth backend will try to
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authenticate against all trusted certificates.
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```
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$ vault auth -method=cert \
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-ca-cert=ca.pem -client-cert=cert.pem -client-key=key.pem \
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name=web
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```
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### Via the API
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The endpoint for the login is `/login`. The client simply connects with their TLS
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certificate and when the login endpoint is hit, the auth backend will determine
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if there is a matching trusted certificate to authenticate the client. Optionally,
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you may specify a single certificate role to authenticate against.
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```
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$ curl --cacert ca.pem --cert cert.pem --key key.pem -d name=web \
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$VAULT_ADDR/v1/auth/cert/login -XPOST
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```
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## Configuration
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First, you must enable the certificate auth backend:
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```
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$ vault auth-enable cert
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Successfully enabled 'cert' at 'cert'!
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```
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Now when you run `vault auth -methods`, the certificate backend is available:
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```
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Path Type Description
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cert/ cert
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token/ token token based credentials
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```
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To use the "cert" auth backend, an operator must configure it with
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trusted certificates that are allowed to authenticate. An example is shown below.
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Use `vault path-help` for more details.
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```
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$ vault write auth/cert/certs/web \
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display_name=web \
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policies=web,prod \
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certificate=@web-cert.pem \
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ttl=3600
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...
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```
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The above creates a new trusted certificate "web" with same display name
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and the "web" and "prod" policies. The certificate (public key) used to verify
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clients is given by the "web-cert.pem" file. Lastly, an optional `ttl` value
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can be provided in seconds to limit the lease duration.
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#### Via the API
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The token is set directly as a header for the HTTP API. The name
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of the header should be "X-Vault-Token" and the value should be the token.
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## API
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The TLS Certificate authentication backend has a full HTTP API. Please see the
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[TLS Certificate API](/api/auth/cert/index.html) for more details. |