B4X

SFTP Authenticate with a Private Key

Demonstrates the Chilkat SFtp.AuthenticatePk method, which authenticates the connected session using public-key authentication. The first argument is the username and the second is an SshKey private key. The matching public key must already be authorized for the account on the server.

Note: The private-key path is relative to the application's current working directory. Supply the path to your own key file.

Background: Public-key authentication is the standard for unattended SFTP transfers: the private key stays on the client, the server trusts the corresponding public key, and no reusable password crosses the wire. The SshKey object imports keys in several formats — this example loads an OpenSSH private key. For an encrypted key, set its Password property before importing.

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Dim success As Boolean = False

'  Demonstrates the SFtp.AuthenticatePk method, which authenticates the connected session using
'  public-key authentication.  The 1st argument is the username and the 2nd is an SshKey private
'  key.  The matching public key must already be authorized for the account on the server.

Dim sftp As ChilkatSFtp
sftp.Initialize("sftp")

'  Step 1: Connect the SSH transport.  Port 22 is the usual port.
Dim port As Int = 22
success = sftp.Connect("sftp.example.com", port)
If success = False Then
    Log(sftp.LastErrorText)
    Return
End If


'  Load the SSH private key.  LoadText reads the file's text, which is then imported.
Dim privKey As ChilkatSshKey
privKey.Initialize
Dim keyText As String = privKey.LoadText("qa_data/id_rsa")
If privKey.LastMethodSuccess = False Then
    Log(privKey.LastErrorText)
    Return
End If

success = privKey.FromOpenSshPrivateKey(keyText)
If success = False Then
    Log(privKey.LastErrorText)
    Return
End If


success = sftp.AuthenticatePk("mySshLogin", privKey)
If success = False Then
    Log(sftp.LastErrorText)
    Return
End If


'  Step 3: Open the SFTP subsystem.  This must be done after authentication and before any
'  file or directory operations.
success = sftp.InitializeSftp
If success = False Then
    Log(sftp.LastErrorText)
    Return
End If


Log("Authenticated with a private key.")

sftp.Disconnect