VB.NET
VB.NET
SFTP Set Allowed SSH Algorithms
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Demonstrates the Chilkat SFtp.SetAllowedAlgorithms method, which configures the exact set of SSH algorithms permitted for the connection. A JsonObject supplies comma-separated allow-lists for the kex, hostKey, cipher, and mac categories. It must be called before Connect.
Important: You typically should not set allowed algorithms explicitly. By default Chilkat orders algorithms according to best practices and accounts for known vulnerabilities.
Background: SSH negotiates a mutually supported algorithm from each category at connection time, and pinning that choice makes an application brittle: if a server later drops a weak algorithm or you point the code at a different server, the two sides may fail to agree and the connection breaks. The legitimate reasons to override are a security policy mandating specific algorithms, or a compatibility problem with an old server. Otherwise the safer default is to let the library's ordering evolve as guidance changes.
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Dim success As Boolean = False
' Demonstrates the SFtp.SetAllowedAlgorithms method, which configures the exact set of SSH
' algorithms permitted for the connection. The only argument is a JsonObject. It must be
' called before Connect.
'
' -------------------------------------------------------------------------------------------
' Note: You typically should NOT explicitly set allowed algorithms.
' By default, Chilkat orders algorithms according to best practices and accounts for known
' vulnerabilities such as the "Terrapin Attack". Hard-coding algorithms can make an
' application brittle over time: if a server later changes its allowed algorithms, or if you
' connect to a different server, the client and server may fail to agree on a mutually
' supported set.
' -------------------------------------------------------------------------------------------
Dim sftp As New Chilkat.SFtp
Dim json As New Chilkat.JsonObject
' The algorithms supported by Chilkat, by category:
'
' Key-exchange:
' 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
'
' Host key:
' ssh-ed25519
' ecdsa-sha2-nistp256
' ecdsa-sha2-nistp384
' ecdsa-sha2-nistp521
' rsa-sha2-256
' rsa-sha2-512
' ssh-rsa
' ssh-dss
'
' Cipher (encryption):
' 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
'
' MAC (hash):
' 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
' List the allowed key-exchange, host-key, cipher (encryption), and mac (hash) algorithms, in
' order of preference.
Dim allowed_kex As String = "curve25519-sha256@libssh.org,ecdh-sha2-nistp256"
Dim allowed_hostKey As String = "ssh-ed25519,ecdsa-sha2-nistp256"
Dim allowed_cipher As String = "chacha20-poly1305@openssh.com,aes256-ctr"
Dim allowed_mac As String = "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)
' Apply the allow-list before connecting.
success = sftp.SetAllowedAlgorithms(json)
If (success = False) Then
Debug.WriteLine(sftp.LastErrorText)
Exit Sub
End If
Dim port As Integer = 22
success = sftp.Connect("sftp.example.com",port)
If (success = False) Then
Debug.WriteLine(sftp.LastErrorText)
Exit Sub
End If
Debug.WriteLine("Connected.")
sftp.Disconnect()