CkPython

SSH Authenticate using a Smart Card Private Key

Demonstrates using a private key stored on an HSM (smart card or token) for SSH public-key authentication. A JSON template locates the private and public key objects by class, key type, and label, and the returned handles are bound to an SshKey object.

Background: PKCS#11 objects are found by attribute rather than by name alone, which is why a template describing the class, key type, and label is used. An important practical detail is that the returned handles are valid only for the lifetime of the PKCS#11 session — they cannot be cached and reused later, so a subsequent session must locate the objects again. Logging out and closing the session when finished releases the device for other applications.

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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 using a private key stored on an HSM (smart card or token) for SSH public-key
#  authentication.  Public-key authentication means the client uses the private key, while the
#  corresponding public key is installed on the server under the SSH account.
#  
#  Note: Chilkat's PKCS#11 implementation runs on Windows, Linux, macOS, and other supported
#  operating systems.

pkcs11 = chilkat.CkPkcs11()

#  Use the PKCS#11 driver (.dll, .so, or .dylib) for your particular HSM.
pkcs11.put_SharedLibPath("C:/Program Files (x86)/Gemalto/IDGo 800 PKCS#11/IDPrimePKCS11.dll")

#  The HSM 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()

#  Provide a template describing the PKCS#11 object to find: an RSA private key labeled
#  "MySshKey".  For how such a key is originally imported, see
#  PKCS11 Import SSH Key
jsonTemplate = chilkat.CkJsonObject()
jsonTemplate.UpdateString("class","private_key")
jsonTemplate.UpdateString("key_type","rsa")
jsonTemplate.UpdateString("label","MySshKey")

privKeyHandle = pkcs11.FindObject(jsonTemplate)
if (privKeyHandle == 0):
    print(pkcs11.lastErrorText())
    sys.exit()

#  The handle is only valid for the duration of this PKCS#11 session.  To use the key in a
#  later session, find it again.
print("private key handle: " + str(privKeyHandle))

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

pubKeyHandle = pkcs11.FindObject(jsonTemplate)
if (pubKeyHandle == 0):
    print(pkcs11.lastErrorText())
    sys.exit()

print("public key handle: " + str(pubKeyHandle))

#  Create an empty SSH key object and tell it to use the PKCS#11 handles, indicating the key type.
sshKey = chilkat.CkSshKey()
success = sshKey.UsePkcs11(pkcs11,privKeyHandle,pubKeyHandle,"rsa")
if (success == False):
    print(sshKey.lastErrorText())
    sys.exit()

ssh = chilkat.CkSsh()

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

#  Authentication uses the existing PKCS#11 session.  The signing happens on the smart card --
#  the private key never leaves the device.
success = ssh.AuthenticatePk("mySshLogin",sshKey)
if (success == False):
    print(ssh.lastErrorText())
    sys.exit()

print("Public-key authentication successful.")

#  ... use the authenticated SSH session ...

ssh.Disconnect()

pkcs11.Logout()
pkcs11.CloseSession()