Managing Secrets with Chef Vault

This post was originally published on jtimberman’s Code Blog

Two years ago, I wrote a post about using Chef encrypted data bags for SASL authentication with Postfix. At the time, my ISP didn’t allow non-authenticated SMTP, so I had to find a solution so I could get cronspam and other vital email from my servers at home. I’ve since switched ISPs to one that doesn’t care so much about this, so I’m not using any of that code anymore.

However, that doesn’t mean I don’t have secrets to manage! I actually don’t for my personal systems due to what I’m managing with Chef now, but we certainly do for Opscode’s hosted Enterprise Chef environment. The usual suspects for any web application are required: database passwords, SSL certificates, service API tokens, etc.

We’re evaluating chef-vault as a possible solution. This blog post will serve as notes for me so I can remember what I did when my terminal history is gone, and hopefully information for you to be able to use in your own environment.

Chef Vault

Chef Vault is an open source project published by Nordstrom. It is distributed as a RubyGem. You’ll need it installed on your local workstation so you can encrypt sensitive secrets, and on any systems that need to decrypt said secrets. Since the workstation is where we’re going to start, install the gem. I’ll talk about using this in a recipe later.

% gem install chef-vault

Use Cases

Now, for the use cases, I’m going to take two fairly simple examples, and explain how chef-vault works along the way.

  1. A username/password combination. The vaultuser will be created on the system with Chef’s built-in user resource.
  2. A file with sensitive content. In this case, I’m going to use a junk RSA private key for vaultuser.

Secrets are generally one of these things. Either a value passed into a command-line program (like useradd) or a file that should live on disk (like an SSL certificate or RSA key).

Command-line Structure

Chef Vault includes knife plugins to allow you to manage the secrets from your workstation, uploading them to the Chef Server just like normal data bags. The secrets themselves live in Data Bags on the Chef Server. The “bag” is called the “vault” for chef-vault.

After installation, the encrypt and decrypt sub-commands will be available for knife.

knife encrypt create [VAULT] [ITEM] [VALUES] --mode MODE --search SEARCH --admins ADMINS --json FILE
knife encrypt delete [VAULT] [ITEM] --mode MODE
knife encrypt remove [VAULT] [ITEM] [VALUES] --mode MODE --search SEARCH --admins ADMINS
knife rotate secret [VAULT] [ITEM] --mode MODE
knife encrypt update [VAULT] [ITEM] [VALUES] --mode MODE --search SEARCH --admins ADMINS --json FILE
knife decrypt [VAULT] [ITEM] [VALUES] --mode MODE

The README and Examples document these quite well.

Mode: Solo vs Client

I’m using Chef with a Chef Server (Enterprise Chef), so I’ll specify --mode client for the knife commands.

It is important to note the MODE in the chef-vault knife plugin commands affects where the encrypted data bags will be saved. Chef supports data bags with both Solo and Client/Server use. When using chef-solo, you’ll need to configure data_bag_path in your knife.rb. That is, even if you’re using Solo, since these are knife plugins, the configuration is for knife, not chef-solo. I’m using a Chef Server though, so I’m going to use --mode client.

Create a User with a Password

The user I’m going to create is the arbitrarily named vaultuser, with the super secret password, chef-vault. I’m going to use this on a Linux system with SHA512 hashing, so first I generate a password using mkpasswd:

% mkpasswd -m sha-512
Password: chef-vault

Note: This is the mkpasswd(1) command from the Ubuntu 10.04 mkpasswd package.

Create the Item

The command I’m going to use is knife encrypt create since this is a new secret. I’ll show two examples. First, I’ll pass in the raw JSON data as “values”. You would do this if you’re not going to store the unencrypted secret on disk or in a repository. Second, I’ll pass a JSON file. You would do this if you want to store the unencrypted secret on disk or in a repository.

% knife encrypt create secrets vaultuser \
  '{"vaultuser":"$6$VqEIDjsp$7NtPMhA9cnxvSMTE9l7DMmydJJEymi9b4t1Vhk475vrWlfxMgVb3bDLhpk/RZt0J3X7l5H8WnqFgvq3dIa9Kt/"}' \
  --search 'role:base' \
  --admins jtimberman --mode client

The [VALUES] in this command is raw JSON that will be created in the data bag item by chef-vault. The --search option tells chef-vault to use the public keys of the nodes matching the SOLR query for encrypting the value. Then during the Chef run, chef-vault uses those node’s private keys to decrypt the value. The --admins option tells chef-vault the list of users on the Chef Server who are also allowed to decrypt the secret. This is specified as a comma separated string for
multiple admins. Finally, as I mentioned, I’m using a Chef Server so I need to specify --mode client, since “solo” is the default.

Here’s the equivalent, using a JSON file named secrets_vaultuser.json. It has the content:


The command is:

% knife encrypt create secrets vaultuser \
  --json secrets_vaultuser.json
  --search 'role:base' \
  --admins jtimberman --mode client

Now, let’s see what has been created on the Chef Server. I’ll use the core Chef knife plugin, data bag item show for this.

% knife data bag show secrets

I now have a “secrets” data bag, with two items. The first, vaultuser is the one that contains the actual secret. Let’s see:

% knife data bag show secrets vaultuser
id:        vaultuser
  cipher:         aes-256-cbc
  encrypted_data: j+/fFM7ist6I7K360GNfzSgu6ix63HGyXN2ZAd99R6H4TAJ4pQKuFNpJXYnC
  iv:             cu2Ugw+RpTDVRu1QaaAfug==
  version:        1

As you can see, I have encrypted data. I also told chef-vault that my user can decrypt this. I need to use the knife plugin to do so:

% knife decrypt secrets vaultuser 'vaultuser' --mode client
  vaultuser: $6$VqEIDjsp$7NtPMhA9cnxvSMTE9l7DMmydJJEymi9b4t1Vhk475vrWlfxMgVb3bDLhpk/RZt0J3X7l5H8WnqFgvq3dIa9Kt/

The 'vaultuser' in quotes is the key from the hash of JSON data that I specified earlier. As you can see, the password is that which was generated from the mkpasswd command earlier.

But what nodes have access to decrypt this password? That’s what chef-vault stored in the vaultuser_keys item. Let’s look:

% knife data bag show secrets vaultuser_keys
admins:              jtimberman
id:                  vaultuser_keys
jtimberman:          0Q2bhw/kJl2aIVEwqY6wYhrrfdz9fdsf8tCiIrBih2ZORvV7EEIpzzKQggRX

os-2790002246935003: kGQLsxsFmBe9uPuWxZpKiNBnqJq55hQZJLgaKdjG2Vvivv98RrFGz1y8Xbwe

os-945926465950316:  XzTJrJ3TZZZ1u9L9p6DZledf3bo2ToH2yrLGZQKPV6/ANzElHXGcYrEdtP0q

As we can see, I have two nodes that are API clients with access to decrypt the data bag items. These values are all generated by chef-vault, and I’ll talk about how to update the list and rotate secrets later in this post.

Manage a User Password

Let’s manage a user resource with a password set to the value from our encrypted data bag using Chef Vault.

First, I created a cookbook named vault, and added it to the base role. It contains the following recipe:

chef_gem "chef-vault"
require "chef-vault"

vault = ChefVault::Item.load("secrets", "vaultuser")

user "vaultuser" do
  password vault['vaultuser']
  home "/home/vaultuser"
  supports :manage_home => true
  shell "/bin/bash"
  comment "Chef Vault User"

Let me break this down.

chef_gem "chef-vault"
require "chef-vault"

chef-vault is distributed as a RubyGem, and I want to use it in my recipe(s), so here I use the chef_gem resource. Then, I require it like any other Ruby library.

vault = ChefVault::Item.load("secrets", "vaultuser")

This is where the decryption happens. If I do this under a
chef-shell, I can see:

chef:recipe > vault = ChefVault::Item.load("secrets", "vaultuser")
 => data_bag_item["secrets", "vaultuser", {"id"=>"vaultuser", "vaultuser"=>"$6$VqEIDjsp$7NtPMhA9cnxvSMTE9l7DMmydJJEymi9b4t1Vhk475vrWlfxMgVb3bDLhpk/RZt0J3X7l5H8WnqFgvq3dIa9Kt/"}]

ChefVault::Item.load takes two arguments, the “vault” or data bag,
in this case secrets, and the “item”, in this case vaultuser. It returns a data bag item. Then in the user resource, I use the password:

user "vaultuser" do
  password vault['vaultuser']
  home "/home/vaultuser"
  supports :manage_home => true
  shell "/bin/bash"
  comment "Chef Vault User"

The important resource attribute here is password, where I’m using the local variable, vault and the vaultuser key from the item as decrypted by ChefVault::Item.load. When Chef runs, it will look like this:

Recipe: vault::default
  * chef_gem[chef-vault] action install
    - install version 2.0.1 of package chef-vault
  * chef_gem[chef-vault] action install (up to date)
  * user[vaultuser] action create
    - create user user[vaultuser]

Now, I can su to vaultuser using the password I created:

ubuntu@-2790002246935003:~$ su - vaultuser
Password: chef-vault
vaultuser@os-2790002246935003:~$ id
uid=1001(vaultuser) gid=1001(vaultuser) groups=1001(vaultuser)
vaultuser@os-2790002246935003:~$ pwd

Yay! To show that the user was created with the right password, here’s the DEBUG log output:

INFO: Processing user[vaultuser] action create ((irb#1) line 12)
DEBUG: user[vaultuser] user does not exist
DEBUG: user[vaultuser] setting comment to Chef Vault User
DEBUG: user[vaultuser] setting password to $6$VqEIDjsp$7NtPMhA9cnxvSMTE9l7DMmydJJEymi9b4t1Vhk475vrWlfxMgVb3bDLhpk/RZt0J3X7l5H8WnqFgvq3dIa9Kt/
DEBUG: user[vaultuser] setting shell to /bin/bash
INFO: user[vaultuser] created

Next, I’ll create a secret that is a file rendered on the system.

Create a Private SSH Key

Suppose this vaultuser is to be used for deploying code by cloning a repository. It will need a private SSH key to authenticate, so I’ll create one, with an empty passphrase in this case.

% ssh-keygen -b 4096 -t rsa -f vaultuser-ssh
Generating public/private rsa key pair.
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in vaultuser-ssh.
Your public key has been saved in

Get the SHA256 checksum of the private key. I use SHA256 because that’s what Chef uses for file content. We’ll use this to verify content later.

% sha256sum vaultuser-ssh
a83221c243c9d39d20761e87db6c781ed0729b8ff4c3b330214ebca26e2ea89d  vaultuser-ssh

Assume that I also created the SSH key on GitHub for this user.

In order to have a file’s contents be a JSON value for the data bag item, I’ll remove the newlines (\n), and generate the JSON:

ruby -rjson -e 'puts JSON.generate({"vaultuser-ssh-private" =>"vaultuser-ssh")})' \
  > secrets_vaultuser-ssh-private.json

Now, create the secret on the Chef Server:

knife encrypt create secrets vaultuser-ssh-private \
  --search 'role:base' \
  --json secrets_vaultuser-ssh-private.json \
  --admins jtimberman \
  --mode client

Let’s verify the server has what we need:

% knife data bag show secrets vaultuser-ssh-private
id:                    vaultuser-ssh-private
  cipher:         aes-256-cbc
  encrypted_data: mRRToM2N/0F+OyJxkYlHo/cUtHSIuy69ROAKuGoHIhX9Fr5vFTCM4RyWQSTN
  trimmed for brevity even though scrollbars
% knife decrypt secrets vaultuser-ssh-private 'vaultuser-ssh-private' --mode client
  vaultuser-ssh-private: -----BEGIN RSA PRIVATE KEY-----
trimmed for brevity even though scrollbars

Manage the Key File

Now, I’ll manage the private key file with the vault cookbook.

vault_ssh = ChefVault::Item.load("secrets", "vaultuser-ssh-private")

directory "/home/vaultuser/.ssh" do
  owner "vaultuser"
  group "vaultuser"
  mode 0700

file "/home/vaultuser/.ssh/id_rsa" do
  content vault_ssh["vaultuser-ssh-private"]
  owner "vaultuser"
  group "vaultuser"
  mode 0600

Again, let’s break this up a bit. First, load the item from the encrypted data bag like we did before.

vault_ssh = ChefVault::Item.load("secrets", "vaultuser-ssh-private")

Next, make sure that the vaultuser has an .ssh directory with the correct permissions.

directory "/home/vaultuser/.ssh" do
  owner "vaultuser"
  group "vaultuser"
  mode 0700

Finally, manage the content of the private key file with a file resource and the content resource attribute. The value of vault_ssh["vaultuser-ssh-private"] will be a string, with \n’s embedded, but when it’s rendered on disk, it will display properly.

file "/home/vaultuser/.ssh/id_rsa" do
  content vault_ssh["vaultuser-ssh-private"]
  owner "vaultuser"
  group "vaultuser"
  mode 0600

And now run chef on a target node:

Recipe: vault::default
  * chef_gem[chef-vault] action install (up to date)
  * user[vaultuser] action create (up to date)
  * directory[/home/vaultuser/.ssh] action create
    - create new directory /home/vaultuser/.ssh
    - change mode from '' to '0700'
    - change owner from '' to 'vaultuser'
    - change group from '' to 'vaultuser'

  * file[/home/vaultuser/.ssh/id_rsa] action create
    - create new file /home/vaultuser/.ssh/id_rsa with content checksum a83221
        --- /tmp/chef-tempfile20130909-1918-1v5hezo   2013-09-09 22:41:21.887239999 +0000
        +++ /tmp/chef-diff20130909-1918-xwbmsn    2013-09-09 22:41:21.883240065 +0000
        @@ -0,0 +1,51 @@
        +-----BEGIN RSA PRIVATE KEY-----
        output trimmed because its long even though scrollbars again

Note the content checksum, a83221. This will match the checksum of the source file from earlier (scroll up!), and the one rendered:

ubuntu@os-2790002246935003:~$ sudo sha256sum /home/vaultuser/.ssh/id_rsa
a83221c243c9d39d20761e87db6c781ed0729b8ff4c3b330214ebca26e2ea89d  /home/vaultuser/.ssh/id_rsa

Yay! Now, we can SSH to GitHub (note, this is fake GitHub for example purposes).

ubuntu@os-2790002246935003:~$ su - vaultuser
Password: chef-vault
vaultuser@os-2790002246935003:~$ ssh -i .ssh/id_rsa [email protected]
$ hostname
$ id
uid=1002(github) gid=1002(github) groups=1002(github)

Updating a Secret

What happens if we need to update a secret? For example, if an administrator leaves the organization, we will want to change the vaultuser password (and SSH private key).

% mkpasswd -m sha-512
Password: gone-user

The encrypt create command will return an error if the target already exists:

% knife encrypt create secrets vaultuser --search 'role:base' --json secrets_vaultuser.json --admins jtimberman --mode client
ERROR: ChefVault::Exceptions::ItemAlreadyExists: secrets/vaultuser already exists, use 'knife encrypt remove' and 'knife encrypt update' to make changes.

So, I need to use encrypt update. Note make sure that the
contents of the JSON file are valid JSON.

% knife encrypt update secrets vaultuser --search 'role:base' --json secrets_vaultuser.json --admins jtimberman --mode client

encrypt update only updates the things that change, so I can also shorten this:

% knife encrypt update secrets vaultuser --json secrets_vaultuser.json --mode client

Since the search and the admins didn’t change.

Verify it:

% knife decrypt secrets vaultuser 'vaultuser' --mode client
  vaultuser: $6$zM5STNtXdmsrOSm$svJr0tauijqqxTjnMIGJGJPv5V3ovMFCQo.ZDBleiL.yOxcngRqh9yAjpMAsMBA7RlKPv5DKFd1aPZm/wUoKs.

Now, just run Chef on any nodes affected.

Recipe: vault::default
  * chef_gem[chef-vault] action install (up to date)
  * user[vaultuser] action create
    - alter user user[vaultuser]

  * directory[/home/vaultuser/.ssh] action create (up to date)
  * file[/home/vaultuser/.ssh/id_rsa] action create (up to date)
Chef Client finished, 1 resources updated

And su to the vault user with the gone-user password:

ubuntu@os-2790002246935003:~$ su - vaultuser
Password: gone-user

Managing Access to Items

There are three common scenarios which require managing the access to an item in the vault.

  1. A system needs to be taken offline, or otherwise prevented from accessing the item(s).
  2. A new system comes online that needs access.
  3. An admin user has left the organization.
  4. A new admin user has joined the organization.

Suppose we have a system that we need to take offline for some reason, so we want to disable its access to a secret. Or, perhaps we have a user who has left the organization that was an admin. We can do that in a few ways.

Update the Vault Item

The most straightforward way to manage access to an item is to use the update or remove sub-commands.

Remove a System

Suppose I want to remove node DEADNODE, I can qualify the search to exclude the node named DEADNODE:

% knife encrypt update secrets vaultuser \
  --search 'role:base NOT name:DEADNODE' \
  --json secrets_vaultuser.json \
  --admins jtimberman --mode client

Note, as before, admins didn’t change so I don’t need to pass that argument.

Add a New System

If the node has run Chef and is indexed on the Chef Server already, simply rerun the update command with the search:

% knife encrypt update secrets vaultuser \
  --search 'role:base' \
  --json secrets_vaultuser.json \
  --admins jtimberman --mode client

There’s a bit of a “Chicken and Egg” problem here, in that a new node might not be indexed for search if it tried to load the secret during a bootstrap beforehand. For example, if I create an OpenStack instance with the base role in its run list, the node doesn’t exist for the search yet. A solution here is to create the node with an empty run list, allowing it to register with the Chef Server, and then use knife bootstrap to rerun Chef with the proper run list. This is annoying, but no one claimed that chef-vault would solve all problems with shared secret management :-).

Remove an Admin

The admins argument takes a list. Earlier, I only had my userid as an admin. Suppose I created the item with “bofh” as an admin too:

% knife encrypt create secrets vaultuser \
  --search 'role:base' \
  --json secrets_vaultuser.json \
  --admins "jtimberman,bofh" --mode client

To remove the bofh user, use the encrypt remove subcommand. In this case, the --admins argument is the list of admins to remove, rather than add.

% knife encrypt remove secrets vaultuser --admins bofh --mode client

Add a New Admin

I want to add “mandi” as an administrator because she’s awesome and will help manage our secrets. As above, I just pass a comma-separated string, "jtimberman,mandi" to the --admins argument.

% knife encrypt update secrets vaultuser \
  --search 'role:base' \
  --json secrets_vaultuser.json \
  --admins "jtimberman,mandi" --mode client

Regenerate the Client

The heavyhanded way to remove access is to regenerate the API client
on the Chef Server. For example, of my nodes, say I want to remove

% knife client reregister os-945926465950316
trim trim

If you’re familiar with Chef Server’s authentication cycle, you’ll
know that until that private key is copied to the node, it will
completely fail to authenticate. However, once the
/etc/chef/client.pem file is updated with the content from the knife
command, we’ll see that the node fails to read the Chef Vault item:

Recipe Compile Error in /var/chef/cache/cookbooks/vault/recipes/default.rb

padding check failed

Cookbook Trace:
  /var/chef/cache/cookbooks/vault/recipes/default.rb:4:in `from_file'

Relevant File Content:

  1:  chef_gem "chef-vault"
  2:  require "chef-vault"
  4>> vault = ChefVault::Item.load("secrets", "vaultuser")
  6:  user "vaultuser" do
  7:    password vault["vaultuser"]
  8:    home "/home/vaultuser"
  9:    supports :manage_home => true
 10:    shell "/bin/bash"
 11:    comment "Chef Vault User"
 12:  end

Note I say this is heavy-handed because if you make a mistake, you need to re-upload every single secret that this node needs access to.

Removing Users

We can also remove user access from Enterprise Chef simply by disassociating that user from the organization on the Chef Server. I won’t show an example of that here, since I’m using Opscode’s hosted Enterprise Chef server and I’m the only admin, however :-)./p>

Backing Up Secrets

To back up the secrets, as encrypted data from the Chef Server, use knife-essentials (comes with Chef 11+, available as a RubyGem for Chef 10).

% knife download data_bags/secrets/
Created data_bags/secrets/vaultuser_keys.json
Created data_bags/secrets/vaultuser.json
Created data_bags/secrets/vaultuser-ssh-private_keys.json
Created data_bags/secrets/vaultuser-ssh-private.json

For example, the vaultuser.json file looks like this:

  "id": "vaultuser",
  "vaultuser": {
    "encrypted_data": "3yREwInxdyKpf8nuTIivXAeuEzHt7o4vF4FsOwmVLHmMWol5nCBoMWF0YdaW\n3P3NpEAAAxYEYeJYdVkrdLqjjB2kTJdx0+ceh/RBHBWqmSeHOWFH9pCRGjV8\nfS5XaTueShb320b/+Ia8iqUJJWg6utnbJCDx+VMcGNggPXgPKC8=\n",
    "iv": "EI+y74Uj2uwq7EVaP+0K6Q==\n",
    "version": 1,
    "cipher": "aes-256-cbc"

Since these are encrypted using a strong cipher (AES 256), they should be safe to store in repository. Unless you think the NSA has access to that repository ;-).


Secrets management is hard! Especially when you need to store secrets that are used by multiple systems, services, and people. Chef’s encrypted data bag feature isn’t a panacea, but it certainly helps. Hopefully, this blog post was informative.

Joshua Timberman

Joshua Timberman is a Code Cleric at CHEF, where he Cures Technical Debt Wounds for 1d8+5 lines of code, casts Protection from Yaks, and otherwise helps continuously improve internal technical process.