vault-plugin-auth-templated-aws

vault-plugin-auth-templated-aws is a vault plugin to dynamically create roles and policies based on the identity of the EC2 instance requesting a vault token. It is implemented as a fork of vault's awsauth backend, with a templating system added.

To build:

$ dep ensure
$ go build

To run:

Add plugin_directory = "/etc/vault/plugins" to vault config.

Copy binary into plugin directory:

$ mkdir -p /etc/vault/plugins/
$ cp vault-plugin-auth-templated-aws /etc/vault/plugins/vault-plugin-auth-templated-aws

Calculate hash of plugin:

$ export SHA256=$(shasum -a 256 "/etc/vault/plugins/vault-plugin-auth-templated-aws" | cut -d' ' -f1)

$ vault write sys/plugins/catalog/vault-plugin-auth-templated-aws sha_256="${SHA256}" command="vault-plugin-auth-templated-aws"

Enable it as an auth method:

$ vault auth enable -path="tarmak" -plugin-name="vault-plugin-auth-templated-aws" plugin

Check it appears in auth list:

$ vault auth list

Disable it with:

$ vault auth disable tarmak

Configuring

Set the vault token and address to use for writing new policies:

vault write auth/tarmak/config/vault token=7459a4df-1e18-6b08-5c0a-f0106badc284 address=http://127.0.0.1:8200

Optionally set the aws credentials for talking to the ec2 api:

vault write auth/tarmak/config/client secret_key=something access_key=something_else

Create role:

vault write auth/tarmak/role/vault-test bound_iam_role_arn=arn:aws:iam::228615251467:role/tarmak-vault base_path="/"

Create some templates (see the section below for more information):

vault write auth/tarmak/template/vault-test/test-policy template='path "secret/*" { capabilities = ["create"] } path "secret/foo" { capabilities = ["read"] }' type=policy path="sys/policy"
vault write auth/tarmak/template/vault-test/test-pki template='{"allowed_domains": ["{{ .FQDN }}"], "allow_subdomains": true}' type=generic path="pki/roles"

Get a token:

vault write auth/tarmak/login pkcs7="$(curl -s http://169.254.169.254/latest/dynamic/instance-identity/pkcs7)" role=vault-test

Templates

Templates are processed using go's templating langauge, with the following variables supported:

{{ .InstanceHash }}: the ID of the requesting instance (e.g i-0f7ebb331c89ed78c)
{{ .FQDN }}: the private DNS name of the requesting instance (e.g. ip-172-31-19-213.eu-west-1.compute.internal)
{{ .InternalIPv4 }}: the private IP address of the requesting instance
{{ .BasePath }}: the base_path set on the role used
{{ .OutputPath }}: the path set on the template
{{ .TemplateName }}: the name of the template

These templates will be rendered to {{.BasePath}}/{{.OutputPath}}/{{.TemplateName}}-{{.InstanceHash}} in vault.

policy

Templates with type=policy are parsed and processed in HCL. See this page for details.

generic

Templates with type=generic are specified in JSON format, and are processed as generic vault secrets. Although being intended to configure PKI roles, they could be used for other purposes.

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