Access HashiCorp Vault Secrets

31 August 2020
vault

Access HashiCorp Vault Secrets

This is the fourth post in a series on Vault. For previous posts see, Getting Started, Secrets Engines, and Manage Policies.

Overview

Authentication is the process where users or automation provide credentials to gain a token. The tokens, similar to a session ID on a website, is then used to interact with Vault. The token itself states the policies and as a result the roles and access the user has. When using the development server, users are already familiar with using the hard-coded root token to get started.

Access Methods

Vault has a number of authentication methods to choose from. Allowing a user to choose the best method of any use case. These methods are how clients or users access Vault.

Here are a couple of options in more detail:

TLS Certificates

The TLS Certificate method allows for using SSL/TLS client certificates, signed by a CA or self-signed, for access.

The following enables the certificate auth method and adds a certificate for a “builder” policy. These builders are added to the test and build policies and places a one hour ttl to leases:

vault auth enable cert
vault write auth/cert/certs/builder \
    display_name=builder \
    policies=test,build \
    certificate=@node-cert.pem \
    ttl=3600

Then on the builder to login with the client cert:

vault login \
    -method=cert \
    -ca-cert=vault-ca.pem \
    -client-cert=cert.pem \
    -client-key=key.pem \
    name=builder

Userpass

The Userpass method allows users to access Vault using a username and password.

$ vault auth enable userpass
Success! Enabled userpass auth method at: userpass/
$ vault write auth/userpass/users/joe password=secret policies=admin
Success! Data written to: auth/userpass/users/joe

Then to login using the new access:

$ vault login -method=userpass username=joe password=secret
Success! You are now authenticated. The token information displayed below...

The user’s token string and TTY is printed along with the policies that apply to the user.

AppRole

The AppRole enables a variety of potential workflows focused around automation. A role could possibly be created for a specific app on a machine, a user, across a number of machines, or even something else.

The AppRole method uses a role ID and secret ID to login and fetch a token. The role ID could be shared across a variety of machines, while the secret ID is meant to be unique for one instance of an application. The uniqueness allows for better auditing and having finer-grained revocation.

To start an admin enables the AppRole method and adds a role with a variety of ttl, use restrictions, and policies:

vault auth enable approle
vault write auth/approle/role/builder \
    token_policies="test,build" \
    secret_id_ttl=10m \
    token_num_uses=10 \
    token_ttl=20m \
    token_max_ttl=30m \
    secret_id_num_uses=40

Then users, admins, or an orchestration mechanism can generate role and secret IDs as needed. This is done by the following:

$ vault read auth/approle/role/builder/role-id
Key        Value
---        -----
role_id    b7094758-f0b8-3148-97c1-2aa82cd627ff
$ vault write -f auth/approle/role/builder/secret-id
Key                   Value
---                   -----
secret_id             24cfaecf-a0c7-5381-541c-4e250d48e8d7
secret_id_accessor    171b256f-024a-a34b-3add-0d49648b2a20

Finally, to login using this mechanism is as easy as passing the role and secret IDs:

vault write auth/approle/login role_id=${ROLE_ID} secret_id=${SECRET_ID}

Clouds

There are also authentication methods that let a user get cloud credentials.

These exist for the following clouds:

Others

Finally, there are even more options that involve integration with other services:

See the authentication docs for the full list of support methods.

Next Steps

With secrets, policies, and access in place, it is time to look deeper into dynamic database secret generation.

Cloud Dynamic Secrets with HashiCorp Vault

02 September 2020
vault

Database Dynamic Secrets with HashiCorp Vault

01 September 2020
vault

Managing HashiCorp Vault Access Policies

30 August 2020
vault