Hardware Security Module support for JSON Web Key Sets
The PKCS#11 Cryptographic Token Interface Standard, also known as Cryptoki, is one of the Public Key Cryptography Standards developed by RSA Security. PKCS#11 defines the interface between an application and a cryptographic device.
note
If a key is not found in the Hardware Security Module, the regular Software Key Manager with AES-GCM software encryption will be used as a fallback. Storing keys will always use the Software Key Manager as it is not possible to add keys to a Hardware Security Module.
PKCS#11 is used as a low-level interface to perform cryptographic operations without the need for the application to directly interface a device through its driver. PKCS#11 represents cryptographic devices using a common model referred to simply as a token. An application can therefore perform cryptographic operations on any device or token, using the same independent command set.
Hardware Security Module configuration​
Ory Hydra can be configured using environment variables as well as a configuration file. For more information on configuration options, open the configuration documentation:
>> https://www.ory.sh/hydra/docs/reference/configuration <<
HSM_ENABLED=true
HSM_LIBRARY=/path/to/hsm-vendor/library.so
HSM_TOKEN_LABEL=hydra
HSM_SLOT=0
HSM_PIN=1234
Token that is denoted by environment variables HSM_TOKEN_LABEL or HSM_SLOT
must preexist and optionally contain RSA or ECDSA key pairs with labels
hydra.openid.id-token and hydra.jwt.access-token depending on configuration.
If keys with these labels don't exist, they will be generated upon
startup. If both HSM_TOKEN_LABEL and HSM_SLOT are set, HSM_TOKEN_LABEL
takes preference over HSM_SLOT. In this case first slot that contains this
label is used. HSM_LIBRARY must point to vendor specific PKCS#11 library or
SoftHSM library if you want to test HSM support.
PKCS#11 attribute mappings to JSON Web Key Set attributes​
When key pair is generated or requested from HSM, the CKA_LABEL attribute is
used as JSON Web Key Set name, CKA_ID attribute as kid. Key usage is
determined by private key attributes, where CKA_SIGN and CKA_DECRYPT are
mapped to sig and enc respectively and set as key use attribute.
Furthermore, CKA_ID's of key pair private/public handles must be identical.
Attribute alg is determined from CKA_KEY_TYPE and CKA_ECDSA_PARAMS.
Supported key algorithms​
Ory Hydra supports generating 4096 bit RSA, ECDSA keys with curves secp256r1 or secp521r1. As of now PKCS#11 v2.4 doesn't support EdDSA keys using curve Ed25519. However, PKCS#11 v3.0 contains support for EdDSA and therefore can be supported in upcoming versions. Symmetric key algorithms are not supported because it would imply, that shared HSM is used between server and authenticating client.
Generating key pairs​
Initializing token​
Different policies can apply for tokens, therefore HSM configuration expects,
that token where to find or generate keys already exists. Depending on HSM
vendor, tools initializing tokens and generating keys vary. To demonstrate key
pair generation we first initialize token using pkcs11-tool (see how to
setup SoftHSM and OpenSC)
$ pkcs11-tool --module /usr/lib/softhsm/libsofthsm2.so --slot 0 --init-token --so-pin 0000 --pin 1234 --init-pin --label hydra
Using slot 0 with a present token (0x2763db07)
Token successfully initialized
User PIN successfully initialized
Corresponding Ory Hydra configuration to access this token would be
HSM_ENABLED=true
HSM_LIBRARY=/usr/lib/softhsm/libsofthsm2.so
HSM_TOKEN_LABEL=hydra
HSM_SLOT=0
HSM_PIN=1234
Generating key pair​
Generating RSA keypair for JSON Web Key hydra.openid.id-token
$ pkcs11-tool --module /usr/lib/softhsm/libsofthsm2.so \
--pin 1234 --token-label hydra \
--keypairgen --key-type rsa:4096 --usage-sign \
--label hydra.openid.id-token --id 746573742d6b65792d6964
Key pair generated:
Private Key Object; RSA
label: hydra.openid.id-token
ID: 746573742d6b65792d6964
Usage: sign
Public Key Object; RSA 4096 bits
label: hydra.openid.id-token
ID: 746573742d6b65792d6964
Usage: verify
| Parameter | Description |
|---|---|
--module | Points to vendor specific PKCS#11 library or SoftHSM library when testing. |
--pin 1234 | Pin that was used in token initialization to perform token operations. |
--token-label hydra | Performs key generation on first slot with label hydra. Use --slot option instead if you want to specify specific slot. |
--label hydra.openid.id-token | Sets key pair label attribute CKA_LABEL and is used as JSON Web Key Set name. |
--id 746573742d6b65792d6964 | Sets key pair id attribute CKA_ID and is used as JSON Web Key Set kid. It must be set as a big-endian hexadecimal integer value. StringToHex("test-key-id") == 746573742d6b65792d6964 |
--keypairgen | Perform key pair generation on token |
--key-type rsa:4096 | Type and length of the key to generate. Supported values are rsa:4096, EC:secp256r1 or EC:secp521r1. Sets CKA_KEY_TYPE,CKA_ECDSA_PARAMS attributes and is used to determine JSON Web Key Set alg attribute. |
--usage-sign or --usage-decrypt | Sets private key attribute CKA_SIGN or CKA_DECRYPT respectively. Used to determine JSON Web Key Set use attribute. |
Key type mappings​
| Key type | JWT signing algorithm |
|---|---|
| rsa:4096 | RS256 |
| EC:secp256r1 | ES256 |
| EC:secp521r1 | ES512 |
Testing with SoftHSM​
SoftHSM is an implementation of a cryptographic store accessible through a PKCS #11 interface. You can use it to explore PKCS#11 without having a Hardware Security Module. It is being developed as a part of the OpenDNSSEC project.
Follow these instructions to build SoftHSM from source.
Install SoftHSM/OpenSC on Mac OSX​
$ ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)" 2> /dev/null
$ brew install softhsm
$ ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)" 2> /dev/null
$ brew install opensc
Install SoftHSM/OpenSC on Ubuntu​
$ sudo apt update
$ sudo apt install softhsm opensc
Install SoftHSM/OpenSC on Windows​
Follow these instructions to install SoftHSM and OpenSC on windows.
Run Ory Hydra with HSM using Docker​
Alternatively you can use quickstart docker container that setups SoftHSM/OpenSC, builds and runs Ory Hydra with HSM configuration enabled. You need to have the latest Docker and Docker Compose version installed. To run quickstart HSM change into the directory with the Hydra source code and run the following command:
$ docker-compose -f quickstart-hsm.yml up --build
Following is logged on startup if Hardware Security Module is successfully configured:
$ docker logs ory-hydra-example--hydra
time="2021-07-07T12:51:23Z" level=info msg="Hardware Security Module is configured."
time="2021-07-07T12:51:23Z" level=info msg="JSON Web Key Set 'hydra.openid.id-token' does not exist yet, generating new key pair..."
Run Tests with HSM enabled using Docker​
$ make quicktest-hsm