Lua Requires Chilkat v9.5.0.99+
SFTP Set Allowed Algorithms

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

Lua
local chilkat = require("chilkat")

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

local sftp = chilkat.SFtp.new()

local json = chilkat.JsonObject.new()

-- 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.
-- -------------------------------------------------------------------------------------------------------------------------------------------
local allowed_kex = "curve25519-sha256@libssh.org,ecdh-sha2-nistp256"
local allowed_hostKey = "ssh-ed25519,ecdsa-sha2-nistp256"
local allowed_cipher = "chacha20-poly1305@openssh.com,aes256-ctr"
local allowed_mac = "hmac-sha2-256,hmac-sha2-512"

json:update_string("kex", allowed_kex)
json:update_string("hostKey", allowed_hostKey)
json:update_string("cipher", allowed_cipher)
json:update_string("mac", allowed_mac)
sftp:set_allowed_algorithms(json)

local port = 22
local success = sftp:connect("example.com", port)
if not success then
    print(sftp.last_error_text)
    return
end

print("Connected.")

-- ....
-- ....