B4X

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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Dim success As Boolean = 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.

Dim pkcs11 As ChilkatPkcs11
pkcs11.Initialize

'  Use the PKCS#11 driver (.dll, .so, or .dylib) for your particular HSM.
pkcs11.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.
Dim pin As String = "0000"

'  Normal user = 1
Dim userType As Int = 1

success = pkcs11.QuickSession(userType, pin)
If success = False Then
    Log(pkcs11.LastErrorText)
    Return
End If


'  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
Dim jsonTemplate As ChilkatJsonObject
jsonTemplate.Initialize
jsonTemplate.UpdateString("class", "private_key")
jsonTemplate.UpdateString("key_type", "rsa")
jsonTemplate.UpdateString("label", "MySshKey")

Dim privKeyHandle As Long = pkcs11.FindObject(jsonTemplate)
If privKeyHandle = 0 Then
    Log(pkcs11.LastErrorText)
    Return
End If


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

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

Dim pubKeyHandle As Long = pkcs11.FindObject(jsonTemplate)
If pubKeyHandle = 0 Then
    Log(pkcs11.LastErrorText)
    Return
End If


Log("public key handle: " & pubKeyHandle)

'  Create an empty SSH key object and tell it to use the PKCS#11 handles, indicating the key type.
Dim sshKey As ChilkatSshKey
sshKey.Initialize
success = sshKey.UsePkcs11(pkcs11, privKeyHandle, pubKeyHandle, "rsa")
If success = False Then
    Log(sshKey.LastErrorText)
    Return
End If


Dim ssh As ChilkatSsh
ssh.Initialize("ssh")

Dim port As Int = 22
success = ssh.Connect("ssh.example.com", port)
If success = False Then
    Log(ssh.LastErrorText)
    Return
End If


'  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 Then
    Log(ssh.LastErrorText)
    Return
End If


Log("Public-key authentication successful.")

'  ... use the authenticated SSH session ...

ssh.Disconnect

pkcs11.Logout
pkcs11.CloseSession