csr_attributes.yaml: Certificate extensions

Location

The csr_attributes.yaml file is located at $confdir/csr_attributes.yaml by default. Its location is configurable with the csr_attributes setting.

The location of the confdir depends on your operating system. See the confdir documentation for details.

Example

---
custom_attributes:
  1.2.840.113549.1.9.7: 342thbjkt82094y0uthhor289jnqthpc2290
extension_requests:
  pp_uuid: ED803750-E3C7-44F5-BB08-41A04433FE2E
  pp_image_name: my_ami_image
  pp_preshared_key: 342thbjkt82094y0uthhor289jnqthpc2290

Format

The csr_attributes file must be a YAML hash containing one or both of the following keys:

• custom_attributes

• extension_requests

The value of each key must also be a hash, where:

• Each key is a valid object identifier (OID). Note that Puppet-specific OIDs can optionally be referenced by short name instead of by numeric ID. In the example above, pp_uuid is a short name for a Puppet-specific OID.

• Each value is an object that can be cast to a string. That is, numbers are allowed but arrays are not.

Allowed OIDs for custom attributes

Custom attributes can use any public or site-specific OID, with the exception of the OIDs used for core X.509 functionality. This means you can’t re-use existing OIDs for things like subject alternative names.

One useful OID is the “challengePassword” attribute — 1.2.840.113549.1.9.7. This is a rarely-used corner of X.509 which can be repurposed to hold a pre-shared key. The benefit of using this instead of an arbitrary OID is that it appears by name when using OpenSSL to dump the CSR to text; OIDs that openssl req can’t recognize are displayed as numerical strings.

Also note that the Puppet-specific OIDs listed below can also be used in CSR attributes.

Allowed OIDs for extension requests

Extension request OIDs must be under the “ppRegCertExt” (1.3.6.1.4.1.34380.1.1) or “ppPrivCertExt” (1.3.6.1.4.1.34380.1.2) OID arcs.

Puppet provides several registered OIDs (under “ppRegCertExt”) for the most common kinds of extension information, as well as a private OID range (“ppPrivCertExt”) for site-specific extension information. The benefits of using the registered OIDs are:

• They can be referenced in csr_attributes.yaml using their short names instead of their numeric IDs.

• When using Puppet tools to print certificate info, they appear using their descriptive names instead of their numeric IDs.

The private range is available for any information you want to embed into a certificate that isn’t already in wide use elsewhere. It is completely unregulated, and its contents are expected to be different in every Puppet deployment.