(Delphi DLL) SFTP Set Allowed Algorithms

See more SFTP Examples

Demonstrates how to explicitly set the algorithms allowed in the SSH connection protocol for SFTP.

Note: This example requires Chilkat v9.5.0.99 or greater.

Chilkat for Delphi Downloads Chilkat non-ActiveX DLL for Delphi Chilkat ActiveX DLL for Delphi * The examples here use the non-ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, SFtp, JsonObject;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
sftp: HCkSFtp;
json: HCkJsonObject;
allowed_kex: PWideChar;
allowed_hostKey: PWideChar;
allowed_cipher: PWideChar;
allowed_mac: PWideChar;
port: Integer;

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

sftp := CkSFtp_Create();

json := CkJsonObject_Create();

// Here are the algorithms supported by Chilkat at the time this example was written (14-June-2024)

// ---------------------------
// SSH Key-Exchange Algorithms
// ---------------------------
// curve25519-sha256
// curve25519-sha256@libssh.org
// ecdh-sha2-nistp256
// ecdh-sha2-nistp384
// ecdh-sha2-nistp521
// diffie-hellman-group14-sha256
// diffie-hellman-group16-sha512
// diffie-hellman-group18-sha512
// diffie-hellman-group-exchange-sha256
// diffie-hellman-group1-sha1
// diffie-hellman-group14-sha1
// diffie-hellman-group-exchange-sha1

// ---------------------------
// SSH Host Key Algorithms
// ---------------------------
// ssh-ed25519
// ecdsa-sha2-nistp256
// ecdsa-sha2-nistp384
// ecdsa-sha2-nistp521
// rsa-sha2-256
// rsa-sha2-512
// ssh-rsa
// ssh-dss

// ---------------------------
// SSH Cipher Algorithms
// ---------------------------
// chacha20-poly1305@openssh.com
// aes128-ctr
// aes256-ctr
// aes192-ctr
// aes128-cbc
// aes256-cbc
// aes192-cbc
// aes128-gcm@openssh.com
// aes256-gcm@openssh.com
// twofish256-cbc
// twofish128-cbc
// blowfish-cbc

// ---------------------------
// SSH MAC Algorithms
// ---------------------------
// hmac-sha2-256
// hmac-sha2-512
// hmac-sha2-256-etm@openssh.com
// hmac-sha2-512-etm@openssh.com
// hmac-sha1-etm@openssh.com
// hmac-sha1
// hmac-ripemd160
// hmac-sha1-96
// hmac-md5

// Specify the allowed key-exchange, host-key, cipher (i.e. encryption), and mac (i.e. hash) algorithms allowed, in the order of preference.
// -------------------------------------------------------------------------------------------------------------------------------------------
// Note: You typically should NOT explicitly set allowed algorithms.
// By default, Chilkat orders algorithms according to best practices, and pays attention to vulnerabilities such as the "Terrapin Attack".
// Hard-coding algorthims can make your application brittle and prone to breaking over a long period of time,
// if a server (at some point in the future) changes its allowed algorithms, or if you connect to a different server,
// such that the client (Chilkat) and server cannot find a set of mutually agreed-upon algorithms.
// -------------------------------------------------------------------------------------------------------------------------------------------
allowed_kex := 'curve25519-sha256@libssh.org,ecdh-sha2-nistp256';
allowed_hostKey := 'ssh-ed25519,ecdsa-sha2-nistp256';
allowed_cipher := 'chacha20-poly1305@openssh.com,aes256-ctr';
allowed_mac := 'hmac-sha2-256,hmac-sha2-512';

CkJsonObject_UpdateString(json,'kex',allowed_kex);
CkJsonObject_UpdateString(json,'hostKey',allowed_hostKey);
CkJsonObject_UpdateString(json,'cipher',allowed_cipher);
CkJsonObject_UpdateString(json,'mac',allowed_mac);
CkSFtp_SetAllowedAlgorithms(sftp,json);

port := 22;
success := CkSFtp_Connect(sftp,'example.com',port);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkSFtp__lastErrorText(sftp));
    Exit;
  end;

Memo1.Lines.Add('Connected.');

// ....
// ....

CkSFtp_Dispose(sftp);
CkJsonObject_Dispose(json);

end;