Xojo Plugin

SSH Host Key Fingerprint

Demonstrates getting the SSH server's host key fingerprint after connecting. The HostKeyFingerprint property returns the classic MD5 form, while GetHostKeyFP returns a fingerprint using a chosen hash algorithm, with optional inclusion of the key type and hash name.

Background: The host key fingerprint identifies the server, and comparing it against a known-good value is how a client implements host-key pinning — detecting a man-in-the-middle or a server whose key has changed. This is the same fingerprint an SSH client shows on first connection when it asks whether to trust the host. Prefer SHA256, which is the modern standard; MD5 fingerprints still appear in older tooling but are cryptographically weak.

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Xojo Plugin

Dim success As Boolean
success = False

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

//  Demonstrates getting the SSH server's host key fingerprint after connecting.

Dim ssh As New Chilkat.Ssh

Dim hostname As String
hostname = "ssh.example.com"
Dim port As Int32
port = 22
success = ssh.Connect(hostname,port)
If (success = False) Then
    System.DebugLog(ssh.LastErrorText)
    Return
End If

//  The classic MD5 fingerprint is available as a property.
Dim md5_fingerprint As String
md5_fingerprint = ssh.HostKeyFingerprint
System.DebugLog(md5_fingerprint)
//  For example:  ssh-rsa 3072 21:b0:d8:41:4e:ef:78:10:20:af:01:b7:71:5d:eb:94

//  GetHostKeyFP returns a fingerprint using the hash algorithm of your choice, such as SHA256,
//  SHA384, or SHA512.  The 2nd and 3rd arguments control whether the key type and the hash name
//  are included in the returned string.
Dim includeKeyType As Boolean
includeKeyType = True
Dim includeHashName As Boolean
includeHashName = True
Dim sha256_fingerprint As String
sha256_fingerprint = ssh.GetHostKeyFP("SHA256",includeKeyType,includeHashName)
If (ssh.LastMethodSuccess = False) Then
    System.DebugLog(ssh.LastErrorText)
    Return
End If

System.DebugLog(sha256_fingerprint)
//  ssh-rsa SHA256:Ufgj480OsdsCZRjj9sSNM6fpgIcSJ61RsIG8usndUIY=

includeKeyType = False
includeHashName = True
sha256_fingerprint = ssh.GetHostKeyFP("SHA256",includeKeyType,includeHashName)
If (ssh.LastMethodSuccess = False) Then
    System.DebugLog(ssh.LastErrorText)
    Return
End If

System.DebugLog(sha256_fingerprint)
//  SHA256:Ufgj480OsdsCZRjj9sSNM6fpgIcSJ61RsIG8usndUIY=

includeKeyType = True
includeHashName = False
sha256_fingerprint = ssh.GetHostKeyFP("SHA256",includeKeyType,includeHashName)
If (ssh.LastMethodSuccess = False) Then
    System.DebugLog(ssh.LastErrorText)
    Return
End If

System.DebugLog(sha256_fingerprint)
//  ssh-rsa Ufgj480OsdsCZRjj9sSNM6fpgIcSJ61RsIG8usndUIY=

includeKeyType = False
includeHashName = False
sha256_fingerprint = ssh.GetHostKeyFP("SHA256",includeKeyType,includeHashName)
If (ssh.LastMethodSuccess = False) Then
    System.DebugLog(ssh.LastErrorText)
    Return
End If

System.DebugLog(sha256_fingerprint)
//  Ufgj480OsdsCZRjj9sSNM6fpgIcSJ61RsIG8usndUIY=

ssh.Disconnect