Transit secrets re-wrapping

In addition to being able to store secrets, Vault can encrypt/decrypt data that is stored elsewhere. The primary use of this is to allow applications to encrypt their data while still storing it in their primary data store. Vault does not store the data.

The transit secrets engine handles cryptographic functions on data-in-transit, and often referred to as Encryption as a Service (EaaS). Both small amounts of arbitrary data, and large files such as images, can be protected with the transit engine. This EaaS function can augment or eliminate the need for Transparent Data Encryption (TDE) with databases to encrypt the contents of a bucket, volume, and disk, etc.

Encryption Key Rotation

One of the benefits of using the Vault EaaS is its ability to easily rotate the encryption keys. Keys can be rotated manually by a human, or an automated process which invokes the key rotation API endpoint through cron, a CI pipeline, a periodic Nomad batch job, Kubernetes Job, etc.

The goal of this tutorial is to demonstrate an example for re-wrapping data after rotating an encryption key in the transit engine in Vault.

Personas

The end-to-end scenario described in this tutorial involves two personas:

• security engineer with privileged permissions to manage the encryption keys
• app with un-privileged permissions rewraps secrets via API

Challenge

Vault maintains the versioned keyring and the operator can decide the minimum version allowed for decryption operations. When data is encrypted using Vault, the resulting ciphertext is prepended with the version of the key used to encrypt it.

The following example shows data that was encrypted using the fourth version of a particular encryption key:

vault:v4:ueizdCqCJ/YhowQSvmJyucnLfIUMd4S/nLTpGTcz64HXoY69dwOrqerFzOlhqg==

For example, an organization could decide that a key should be rotated once a week, and that the minimum version allowed to decrypt records is the current version as well as the previous two versions. If the current version is five, then Vault would decrypt records that were sent to it with the following prefixes:

• vault:v5:lkjasfdlkjafdlkjsdflajsdf==
• vault:v4:asdfas9pirapirteradr33vvv==
• vault:v3:ouoiujarontoiue8987sdjf^1==

In this example, what would happen if you send Vault data that was encrypted with the first or second version of the key (vault:v1:... or vault:v2:...)?

Vault would refuse to decrypt the data as the key used is less than the minimum key version allowed.

Solution

Luckily, Vault provides an easy way of re-wrapping encrypted data when a key is rotated. Using the rewrap API endpoint, a non-privileged Vault entity can send data encrypted with an older version of the key to have it re-encrypted with the latest version. The application performing the re-wrapping never interacts with the decrypted data. The process of rotating the encryption key and rewrapping records could (and should) be completely automated. Records could be updated slowly over time to lessen database load, or all at once at the time of rotation. The exact implementation will depend heavily on the needs of each particular organization or application.

Prerequisites

This lab was tested on macOS using an x86_64 based processor. If you are running macOS on an Apple silicon-based processor, use a x86_64 based Linux virtual machine in your preferred cloud provider.

• Vault Vault
• Docker to run a MySQL container
• jq installed
• .NET Core SDK

Policy requirements

Each persona require a different set of capabilities. These are expressed in policies. If you are not familiar with policies, complete the policies tutorial.

The security engineer tasks require these capabilities.

# Manage the transit secrets engine
path "transit/keys/*" {
  capabilities = [ "create", "read", "update", "delete", "list", "sudo" ]
}

# Enable the transit secrets engine
path "sys/mounts/transit" {
  capabilities = [ "create", "update" ]
}

# Write ACL policies
path "sys/policies/acl/*" {
  capabilities = [ "create", "read", "update", "delete", "list" ]
}

# Create tokens for verification & test
path "auth/token/create" {
  capabilities = [ "create", "update", "sudo" ]
}

The app tasks require these capabilities.

# rewrap_example.hcl
path "transit/keys/my_app_key" {
  capabilities = ["read"]
}

path "transit/rewrap/my_app_key" {
  capabilities = ["update"]
}

# This last policy is needed to seed the database as part of the example.
# It can be omitted if seeding is not required
path "transit/encrypt/my_app_key" {
  capabilities = ["update"]
}

Lab setup

Clone GitHub repository

Download the sample application code from learn-vault-eaas-transit-rewrap repository to perform the steps described in this tutorial.

1. Clone the learn-vault-eaas-transit-rewrap repository.

   $ git clone git@github.com:hashicorp/learn-vault-eaas-transit-rewrap.git
   

   Or download the repository:

   

   This repository contains supporting content for this Vault tutorial.

2. Go into the learn-vault-eaas-transit-rewrap directory.

   $ cd learn-vault-eaas-transit-rewrap
   

   Working directory

   This tutorial assumes that the remainder of commands are executed within this directory.

Start Vault

1. In another terminal, start a Vault dev server with root as the root token.

   $ vault server -dev -dev-root-token-id root
   

   The Vault dev server defaults to running at 127.0.0.1:8200. The server is initialized and unsealed.

   Insecure operation

   Do not run a Vault dev server in production. This approach starts a Vault server with an in-memory database and runs in an insecure way.

2. Switch back to the terminal you cloned the GitHub repository in. Export an environment variable for the vault CLI to address the Vault server.

   $ export VAULT_ADDR=http://127.0.0.1:8200
   

3. Export an environment variable for the vault CLI to authenticate with the Vault server.

   $ export VAULT_TOKEN=root
   

   Note

   For these tasks, you can use Vault's root token. However, it is recommended that root tokens are only used for enough initial setup or in emergencies. As a best practice, use an authentication method or token that meets the policy requirements.

The Vault server is ready.

Start MySQL database in Docker

The application requires a MySQL database. Docker provides a MySQL server image that satisfies the application's requirements

1. Pull a MySQL server image with docker.

   $ docker pull mysql/mysql-server:5.7
   

2. Create a directory for the demo data.

   $ mkdir ~/rewrap-data
   

3. Create a database named my_app that sets the root user password to root and adds a user named vault.

   $ docker run --name mysql-rewrap \
           --publish 3306:3306 \
           --volume ~/rewrap-data:/var/lib/mysql \
           --env MYSQL_ROOT_PASSWORD=root \
           --env MYSQL_ROOT_HOST=% \
           --env MYSQL_DATABASE=my_app \
           --env MYSQL_USER=vault \
           --env MYSQL_PASSWORD=vaultpw \
           --detach mysql/mysql-server:5.7
   

The database is available.

Enable the transit secrets engine

(Persona: security engineer)

Generate a new token for the sample app

(Persona: security engineer)

Before generating a token, create a limited scope policy named rewrap_example for the sample application.

Review the limited scope policy stored in rewrap_example.hcl.

$ cat rewrap_example.hcl

# rewrap_example.hcl
path "transit/keys/my_app_key" {
  capabilities = ["read"]
}

path "transit/rewrap/my_app_key" {
  capabilities = ["update"]
}

# This last policy is needed to seed the database as part of the example.
# It can be omitted if seeding is not required
path "transit/encrypt/my_app_key" {
  capabilities = ["update"]
}

Run the sample application

(Persona: app)

The application stores data within the database. The data contains a field that require encryption. Vault provides that encryption through the transit secrets engine.

1. Run the sample application with the Vault server address, the transit key, and the generated token.

   $ VAULT_TOKEN=$APP_TOKEN \
        VAULT_ADDR=$VAULT_ADDR \
        VAULT_TRANSIT_KEY=my_app_key \
        SHOULD_SEED_USERS=true \
        dotnet run
   

   Example output:

   Connecting to Vault server...
   Created (if not exist) my_app DB
   Create (if not exist) user_data table
   Seeded the database...
   Moving rewrap...
   Current Key Version: 1
   Found 0 records to rewrap.
   

   The application finishes after it generates several database entries.

2. Connect to the database with the root credentials.

   $ docker exec -it mysql-rewrap mysql -uroot -proot
   

3. Within the mysql shell, connect to the my_app table.

   $ CONNECT my_app;
   

4. Within the mysql shell, display 10 rows from the user_data table where the city starts with a Vault transit key.

   $ SELECT * FROM user_data WHERE city LIKE "vault:v1%" limit 10;
   
   +---------+-----------------+------------+-----------+-------------------------------------------------------------------+-------------+---------------+----------+---------------------------------------------------------------------------------------+
   | user_id | user_name       | first_name | last_name | city                                                              | state       | country       | postcode | email                                                                                 |
   +---------+-----------------+------------+-----------+-------------------------------------------------------------------+-------------+---------------+----------+---------------------------------------------------------------------------------------+
   |       1 | sadfrog482      | Bella      | Gonzalez  | vault:v1:umJ81VPMsg8vhPVeNvdr2v1AM4EBPwHauwLEHhVidH/bXFyFbA==     | Georgia     | United States | 93220    | vault:v1:cvtg4xH/rOIPO2vSFmvrxSTMAKzC1dhr6zUF/WranhlL/6qNk9ifaz6dVEc5ZKATuvC1ftSQ     |
   |       2 | organictiger615 | Hugh       | Richards  | vault:v1:1Ov8PGK1itiJAdtvoV9CrYKzmwPQDFUZAyPKYG8luhxqRP/iOLKI     | Minnesota   | United States | 13652    | vault:v1:8gPJgOQB4/bq36IA6291mpG3szbNR6GxbWQylwJX8UlZXvNWr849nESyYAwBx2YtanJXFio=     |
   |       3 | orangefish367   | Grace      | Stephens  | vault:v1:HMqtwuqH7LOjpBcUbn1pRC/9EYEIRQu0frUX/ROldnTK             | Alaska      | United States | 48923    | vault:v1:jYmJLyYwMeti3aqQ3+QjvJWyg5MEnlY5BV/d5gIoMf+Uj1LyKOByh+6u/4t6ybP1h2CWRZn0     |
   |       4 | bluekoala754    | Stacy      | Grant     | vault:v1:IzjRTrwX8zqgCCM2ZB86/T+tI9d4A1EI4IVUH9O86D2M0PdrsC0=     | Connecticut | United States | 97712    | vault:v1:E4gBEE2jh0ohYMjZu2fCABy0IG7MB3Jr3Jm4KIU5c/hub4sALyYahIV9nAqVXFFRRw/f         |
   |       5 | silverfrog747   | Salvador   | Barrett   | vault:v1:FLPCNxuJn9J5nnctKFROCwlcWaw/Yvq/y1Y5buefSytGExIglVGnMmQ= | Washington  | United States | 26448    | vault:v1:QBra8YwJ1d1Lxu9TukU8qTe9PjxEqUff0fAPzDdSMU/1c/yNC7LNIJx0BsYoJoszcC+vnVyo1no= |
   |       6 | organicfrog759  | Gavin      | Price     | vault:v1:LOJAibVMBbagasMkCvmpdd1ss5R7LTPkShBMfvh/kDye7oxa         | Minnesota   | United States | 25360    | vault:v1:2rY9H15ejMXdumgpOxJXgjXbwoN9U8gk/+Xk+2otKhVV/23zTvxfDctxAXWUXOvsqcsM         |
   |       7 | smallostrich963 | Kurt       | May       | vault:v1:CYLkwI2lIQ/dYcMEUhd/cwAxwwFXwS8/k//KSUu+xIQh2kDp         | Minnesota   | United States | 97820    | vault:v1:uC8rNyb8ju++0bhC6jQdYIct7j2OYeX58TqsVMmI/e7aNL2Oe76ruJ1IVgSk7u2a             |
   |       8 | lazyostrich623  | Kristen    | King      | vault:v1:DsafGtaKOeM6qeruDB2Tl6YcV1xjgjsi3HyDigUVFYjzbmI=         | Mississippi | United States | 28583    | vault:v1:01ZXSUMIJUFx2u7ftgl+8tsfNmU1x89h9i5DUY+SiJ2vry+6ne8O0gELG4wE50XZzide3Q==     |
   |       9 | angryzebra522   | Robert     | Williams  | vault:v1:+I4mFByIoEzQs2ZqYTK/OlsT14S1bo5F6cpRVukBNxhr04jAQ/BU     | Alaska      | United States | 90033    | vault:v1:lszAwKpWp6ij+dILeybir/Enoge3ArsIUh1bHNl+CqHn2RzhcTNJrr6ZoqG8YQvxQWJ+DiU9Qw== |
   |      10 | blueleopard693  | Morris     | Rivera    | vault:v1:vuy1qNHQdLjaCB0tqUOCv3NMbr0Leep0B/5pXgpdGJw=             | Alabama     | United States | 11206    | vault:v1:qSuvWlyb6Ik/gY1t+Z23BBfT8KbVN6RxehOfSRDop9fymAS25X9BH3ljLUvmmow6cusqpyw=     |
   +---------+-----------------+------------+-----------+-------------------------------------------------------------------+-------------+---------------+----------+---------------------------------------------------------------------------------------+
   10 rows in set (0.00 sec)
   

   The results display 10 rows that match this query. The city field is encrypted with the Vault transit key.

5. Drop the connection to the database.

   $ exit
   

   The application used the Vault server through the application token to encrypt these fields.

Rotate the encryption key

(Persona: security engineer)

The encryption key my_app_key can be rotated.

Programmatically re-wrap the data

(Persona: app)

The application's database contains fields encrypted with the first version of the transit key.

1. Run the application again to re-wrap the encrypted fields.

   $ VAULT_TOKEN=$APP_TOKEN \
       VAULT_ADDR=$VAULT_ADDR \
       VAULT_TRANSIT_KEY=my_app_key \
       SHOULD_SEED_USERS=true \
       dotnet run
   

   Example output:

   Connecting to Vault server...
   Created (if not exist) my_app DB
   Create (if not exist) user_data table
   Seeded the database...
   Current Key Version: 2
   Found 3500 records to rewrap.
   Wrapped another 10 records: 10 so far...
   Wrapped another 10 records: 20 so far...
   Wrapped another 10 records: 30 so far...
   ...
   

   The application finishes after it re-wraps the encrypted fields in the existing entries.

2. Connect to the database with the root credentials.

   $ docker exec -it mysql-rewrap mysql -uroot -proot
   

3. Within the mysql shell, connect to the my_app table.

   $ CONNECT my_app;
   

4. Within the mysql shell, display 10 rows from the user_data table where the city starts with a Vault transit key version v1.

   $ SELECT * FROM user_data WHERE city LIKE "vault:v1%" limit 10;
   Empty set (0.00 sec)
   

   The results of this query are an empty set.

5. Within the mysql shell, display 10 rows from the user_data table where the city starts with a Vault transit key version v2.

   $ SELECT * FROM user_data WHERE city LIKE "vault:v2%" limit 10;
   
   +---------+---------------+------------+-----------+-----------------------------------------------------------------------+---------------+---------------+----------+---------------------------------------------------------------------------------------+
   | user_id | user_name     | first_name | last_name | city                                                                  | state         | country       | postcode | email                                                                                 |
   +---------+---------------+------------+-----------+-----------------------------------------------------------------------+---------------+---------------+----------+---------------------------------------------------------------------------------------+
   |       1 | sadbird321    | Steven     | Armstrong | vault:v2:ImEDuJXesH0dN7pWwgTQ1Fnhv/w8HrA9lN4o3ct7+qj0SRNXMfc=         | Utah          | United States | 48605    | vault:v2:HDFbwc365OALVRd+jEIGL4leGIAqAWBBTnvXnBxiLiJx/yUoJxU5FdnllIClNzFoqTbuqoNugJ0= |
   |       2 | lazycat275    | Leah       | Mendoza   | vault:v2:fUK7ca8n/Ji2WfZJR+2YgDI0aQf3+7kIKBLUnOqoyjEQ2NSRWg==         | Iowa          | United States | 54102    | vault:v2:HqkEwJqsGbmFstQ7vRriWf3qrgLGgIgdmS4ubIti079xILbOvbi6qGJkLFBj6H3ulwzmWQ==     |
   |       3 | bigwolf912    | Dean       | Henry     | vault:v2:/mpTDv+Q/NuAfJlS0oeUIXIOfgztr9GapAGsW2m2iXEZoE5nnw==         | Ohio          | United States | 49932    | vault:v2:qbGXgUj4SYPNsXF8jG5jCIhh6SJOFbDFqaBSV3hMB+B7k0UQMxkVlBTOnYgo3rmVh2M=         |
   ...
   10 rows in set (0.00 sec)
   

   The results display 10 rows that match this query. The city field is encrypted with the second version of the Vault transit key.

6. Drop the connection to the database.

   $ exit
   

Clean up

1. Stop and remove the MySQL container.

   $ docker rm mysql-rewrap --force
   

2. Remove the rewrap-data directory

   $ rm -rf ~/rewrap-data
   

3. Remove the local git repository

   $ cd .. && rm -rf learn-vault-eaas-transit-rewrap
   

Conclusion

An application similar to this could be scheduled via cron, run periodically as a Nomad batch job, or executed in a variety of other ways. You could also modify it to re-wrap a limited number of records at a time so as to not put undue strain on the database. The final implementation should be based upon the needs and design goals specific to each organization or application.

Help and Reference

• Transit Secrets Engine
• Transit Secrets Engine API
• Transparent Data Encryption in the Modern Datacenter