CkPython

SSH HSM Public Key Authentication

Demonstrates SSH public-key authentication using a private key stored on an HSM — a USB token or smart card — accessed through PKCS#11. A session is opened with the vendor's driver, the key handles are located, and an SshKey object is bound to them with UsePkcs11.

Background: The point of an HSM is that the private key is generated on the device and cannot be exported: the signing operation happens on the hardware, so the key material never reaches your application's memory or disk. Even a fully compromised host cannot yield a copy of the key. PKCS#11 is the vendor-neutral interface to such devices, which is why the driver path and the object-finding template are the only vendor-specific parts of this example.

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import sys
import chilkat

success = False

#  This example requires the Chilkat API to have been previously unlocked.
#  See Global Unlock Sample for sample code.

#  Demonstrates SSH public-key authentication using a private key stored on an HSM (a USB token
#  or smart card) accessed through PKCS#11.
#  
#  Note: Chilkat's PKCS#11 implementation runs on Windows, Linux, macOS, and other supported
#  operating systems.

pkcs11 = chilkat.CkPkcs11()

#  The PKCS#11 driver supplied by your HSM vendor: a .dll on Windows, a .so on Linux, or a
#  .dylib on macOS.
pkcs11.put_SharedLibPath("C:/Program Files (x86)/Gemalto/IDGo 800 PKCS#11/IDPrimePKCS1164.dll")

#  The PIN should come from a secure source rather than being hard-coded.
pin = "0000"

#  Normal user = 1
userType = 1

success = pkcs11.QuickSession(userType,pin)
if (success == False):
    print(pkcs11.lastErrorText())
    sys.exit()

#  Describe the private key object to be located on the HSM.
json = chilkat.CkJsonObject()
json.UpdateString("class","private_key")
json.UpdateString("label","MySshKey")

priv_handle = pkcs11.FindObject(json)
if (priv_handle == 0):
    print(pkcs11.lastErrorText())
    sys.exit()

#  Find the corresponding public key by changing the class in the same template.
json.UpdateString("class","public_key")

pub_handle = pkcs11.FindObject(json)
if (pub_handle == 0):
    print(pkcs11.lastErrorText())
    sys.exit()

#  Create an SSH key object that uses the HSM handles.  The key type may be "rsa" or "ec".
key = chilkat.CkSshKey()
keyType = "rsa"
success = key.UsePkcs11(pkcs11,priv_handle,pub_handle,keyType)
if (success == False):
    print(key.lastErrorText())
    sys.exit()

ssh = chilkat.CkSsh()

port = 22
success = ssh.Connect("ssh.example.com",port)
if (success == False):
    print(ssh.lastErrorText())
    sys.exit()

#  The corresponding public key must already be installed on the SSH server for the account.
#  The signing operation happens on the HSM -- the private key never leaves the device.
success = ssh.AuthenticatePk("mySshLogin",key)
if (success == False):
    print(ssh.lastErrorText())
    sys.exit()

print("Public-key authentication successful.")

ssh.Disconnect()

pkcs11.Logout()
pkcs11.CloseSession()