This tutorial will cover:
Basic YubiHSM 2 setup
Connecting to YubiHSM 2
Generating an Authkey on the device
Generating an Asymmetric Object
Generate a Wrapkey
Exporting/Importing an Object under wrap
The purpose of this tutorial is to demonstrate basic functionalities of different key types: Authentication Key, Asymmetric Key and Wrap Key. We start with a fresh YubiHSM 2 configuration and we will proceed in generating a new Authentication Key. Then we generate an Asymmetric Key for signing purposes. We will sign an arbitrary amount of data and verify that our signature is correct. Part of this documentation is to demonstrate how to back up a key on a second YubiHSM 2. We will do so by wrapping the Asymmetric Key and re-importing it into the same device.
Before reading this document you should be familiar with concepts such as: Sessions, Domains, Capabilities described in the Concepts Section.
Get the latest binaries from SDK download
Install all libraries
Make sure your device is accessible by the connector. This is accomplished either by running the connector as a superuser or by using an appropriate udev_rule.
To physically reset the YubiHSM 2 insert the device while holding the touch sensor for 10 seconds.
Start the connector
yubihsm-connector -d
Check the status of your connector and device by visiting http://127.0.0.1:12345/connector/status with a browser
Start yubihsm-shell
yubihsm-shell
Connect to YubiHSM 2
yubihsm> connect
Enable keepalive to facilitate usability during first time use (keepalive is enabled by default). Remember that this will consume one session
yubihsm> keepalive on
Enable debug
yubihsm> debug all
Many commands require a Session ID to be specified. To obtain a Session ID use the session open command followed by an Authentication Key ID and a derivation password.
By default the YubiHSM 2 comes with a pre-installed Authentication Key with Object ID 1 and derivation password password. To open a Session with this Authentication Key use
yubihsm> session open 1 password Created session 0
The Session ID is the number found in the line directly below a session open command. In the example above the Session ID is 0. This value will be used to address the newly created Session.
To close a Session use the command session close followed by the Session ID
yubihsm> session close 0
To list the objects in the device use
yubihsm> list objects 0
Note that if you have closed Session 0, the above command will not work. Open a new Session in that case and use the new Session ID in the command above.
Before moving on, make sure you are familiar with concepts of Capabilities and Domains.
For our example we are going to generate an Authentication Key with selected Capabilities and Domains. Learn more about existing key Types here.
yubihsm> put authkey 0 2 yubico 1,2,3 generate-asymmetric-key,export-wrapped,get-pseudo-random,put-wrap-key,import-wrapped,delete-asymmetric-key,sign-ecdsa sign-ecdsa,exportable-under-wrap,export-wrapped,import-wrapped password
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Important
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export-wrapped allows to create Objects that can perform the Export Wrapped command. exportable-under-wrap allows to create Objects that can be exported under wrap. |
Note how the command above has two distinct sets of Capabilities, separated by a space. This is because Authentication Keys, besides having regular Capabilities, also have Delegated Capabilities.
List all Objects to see the newly created Authentication Key
yubihsm> list objects 0
Next, let’s start using our newly created Authentication Key to establish a Session
yubihsm> session open 2 password Created session 1
The new Session has been assigned Session ID 1. We will use this Session ID for most of the commands below.
If at any time the Session is closed or expires because of inactivity, open a new one and use the correct Session ID.
We now proceed to generate a new Asymmetric Key. In our example we will use this key to sign some data. We will also export the key under wrap to another YubiHSM, for backup purposes.
Specifically, we will ask the device to generate an Asymmetric Key with ID 100 and a given set of Domains and Capabilities. We will also specify the kind of Asymmetric Key that we would like to generate, an EC key using the NIST P-256 curve in this case.
The command is
yubihsm> generate asymmetric 1 100 label_ecdsa_sign 1,2,3 exportable-under-wrap,sign-ecdsa ecp256
On success, we will see the message
Generated Asymmetric key 0x0064
signifying that an Asymmetric Key with ID 0x0064 (hexadecimal for 100) was generated.
Assuming we have a file called data.txt containing the data we would like to sign, we will sign it using ECDSA with the Asymmetric Key we generated in the previous step
yubihsm> sign ecdsa 1 100 ecdsa-sha256 data.txt
By default the output is printed to the standard output and consists of a Base64-encoded signature like the one below
MEUCIQDrBqS04LN5YdyWGiD4iaEjfl1dn+W4cl97uMMXDpoaiQIgEBe/G/FgP4cumnO3K2XWToAnPvnuVDOnqHPiuUS0q5g=
This behavior can be changed by using the set outformat and set informat commands, and by specifying an additional output parameter to the sign command.
For now we will store the signature as it is in a temporary file so that we will be able to verify it later
echo MEUCIQDrBqS04LN5YdyWGiD4iaEjfl1dn+W4cl97uMMXDpoaiQIgEBe/G/FgP4cumnO3K2XWToAnPvnuVDOnqHPiuUS0q5g= >signature.b64
Next, we will extract the public key from the Asymmetric Key on the device and write it to the file asymmetric_key.pub, so that we can use it to verify the signature we just created
yubihsm> get pubkey 1 100 asymmetric_key.pub
We are going to use OpenSSL for the verification process. Since the signature that we created before is in Base64 format, we need to convert it first. Do so with
base64 -d signature.b64 >signature.bin
It is now possible to verify the signature with OpenSSL
openssl dgst -sha256 -signature signature.bin -verify asymmetric_key.pub data.txt Verified OK
Time to export the Asymmetric Key under wrap to a second YubiHSM 2 (in this example, we will export to the same YubiHSM for convenience)
To do that we need a Wrap Key, which fundamentally is an AES key. We will use the random number generator built into the YubiHSM to generate the 16 bytes needed for an AES-128 key
yubihsm> get random 1 16 9207653411df91fd36c12faa6886d5c4
The result of this command (the bytes) is considered sensitive data and should be stored safely.
We can now store the Wrap Key on the device with ID 200 by doing
yubihsm> put wrapkey 1 200 label_wrapkey 1,2,3 import-wrapped,export-wrapped sign-ecdsa,exportable-under-wrap 9207653411df91fd36c12faa6886d5c4
Note that for the upcoming export command to be successful, the Delegated Capabilities of the Wrap Key have to include the Capabilities of the Object being exported. Similarly, for the import command to succeed the Delegated Capabilities of the Wrap Key have to include the Capabilities of the Object being imported.
We can now export the Asymmetric Key with ID 100 using the Wrap Key with ID 200 and save it to a file called wrapped_asymmetric.key
yubihsm> get wrapped 1 200 asymmetric-key 100 wrapped_asymmetric.key
We are going to re-import the Asymmetric Key on the same device so we need to first delete the existing one
yubihsm> delete 1 100 asymmetric-key
To import the wrapped EC key back into the YubiHSM use
yubihsm> put wrapped 1 200 wrapped_asymmetric.key