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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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llSuccess = .F.

//  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.

loPkcs11 = createobject("CkPkcs11")

//  Use the PKCS#11 driver (.dll, .so, or .dylib) for your particular HSM.
loPkcs11.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.
lcPin = "0000"

//  Normal user = 1
lnUserType = 1

llSuccess = loPkcs11.QuickSession(lnUserType,lcPin)
if (llSuccess = .F.) then
    ? loPkcs11.LastErrorText
    release loPkcs11
    return
endif

//  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
loJsonTemplate = createobject("CkJsonObject")
loJsonTemplate.UpdateString("class","private_key")
loJsonTemplate.UpdateString("key_type","rsa")
loJsonTemplate.UpdateString("label","MySshKey")

lnPrivKeyHandle = loPkcs11.FindObject(loJsonTemplate)
if (lnPrivKeyHandle = 0) then
    ? loPkcs11.LastErrorText
    release loPkcs11
    release loJsonTemplate
    return
endif

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

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

lnPubKeyHandle = loPkcs11.FindObject(loJsonTemplate)
if (lnPubKeyHandle = 0) then
    ? loPkcs11.LastErrorText
    release loPkcs11
    release loJsonTemplate
    return
endif

? "public key handle: " + str(lnPubKeyHandle)

//  Create an empty SSH key object and tell it to use the PKCS#11 handles, indicating the key type.
loSshKey = createobject("CkSshKey")
llSuccess = loSshKey.UsePkcs11(loPkcs11,lnPrivKeyHandle,lnPubKeyHandle,"rsa")
if (llSuccess = .F.) then
    ? loSshKey.LastErrorText
    release loPkcs11
    release loJsonTemplate
    release loSshKey
    return
endif

loSsh = createobject("CkSsh")

lnPort = 22
llSuccess = loSsh.Connect("ssh.example.com",lnPort)
if (llSuccess = .F.) then
    ? loSsh.LastErrorText
    release loPkcs11
    release loJsonTemplate
    release loSshKey
    release loSsh
    return
endif

//  Authentication uses the existing PKCS#11 session.  The signing happens on the smart card --
//  the private key never leaves the device.
llSuccess = loSsh.AuthenticatePk("mySshLogin",loSshKey)
if (llSuccess = .F.) then
    ? loSsh.LastErrorText
    release loPkcs11
    release loJsonTemplate
    release loSshKey
    release loSsh
    return
endif

? "Public-key authentication successful."

//  ... use the authenticated SSH session ...

loSsh.Disconnect()

loPkcs11.Logout()
loPkcs11.CloseSession()


release loPkcs11
release loJsonTemplate
release loSshKey
release loSsh