(Chilkat2-Python) SFTP Set Allowed Algorithms

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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.

Chilkat2 Python Downloads install with pip pip3 install chilkat2 or download... Python Module for Windows, Linux, Alpine Linux, MacOS, Solaris

import sys
import chilkat2

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

sftp = chilkat2.SFtp()

json = chilkat2.JsonObject()

# 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"

json.UpdateString("kex",allowed_kex)
json.UpdateString("hostKey",allowed_hostKey)
json.UpdateString("cipher",allowed_cipher)
json.UpdateString("mac",allowed_mac)
sftp.SetAllowedAlgorithms(json)

port = 22
success = sftp.Connect("example.com",port)
if (success != True):
    print(sftp.LastErrorText)
    sys.exit()

print("Connected.")

# ....
# ....