Verify checksum of a remote file against a local file over SFTP/FTP protocol

The following example uses WinSCP .NET assembly from a PowerShell script. If you have another preferred language, you can easily translate it.

In the latest beta version, the example is distributed in WinSCP installer as a WinSCP extension.

You can use the script (e.g. VerifyFileChecksum.ps1) from WinSCP GUI as a local custom command:

powershell.exe -File C:\path\VerifyFileChecksum.ps1 -sessionUrl "!S" -localPath "!^!" -remotePath "!/!" -pause

Make sure you check Use remote files option.

Note that calculation of remote file checksum is supported with SFTP and FTP protocols only, subject to support of respective protocol extension.

# @name         Verify &Checksum
# @command      powershell.exe -ExecutionPolicy Bypass -File "%EXTENSION_PATH%" -sessionUrl "!S" -localPath "!^!" -remotePath "!/!" -pause
# @description  Compares checksums of the selected local and remote file
# @flag         RemoteFiles
# @version      1
 
param (
    # Use Generate URL function to obtain a value for -sessionUrl parameter.
    $sessionUrl = "sftp://user:mypassword;fingerprint=ssh-rsa-xx-xx-xx@example.com/",
    [Parameter(Mandatory)]
    $localPath,
    [Parameter(Mandatory)]
    $remotePath,
    [Switch]
    $pause = $False
)
 
try
{
    Write-Host $localPath
 
    # Calculate local file checksum
    $sha1 = [System.Security.Cryptography.SHA1]::Create()
    $localStream = [System.IO.File]::OpenRead($localPath)
    $localChecksum = [System.BitConverter]::ToString($sha1.ComputeHash($localStream))
 
    Write-Host $localChecksum
    
    # Load WinSCP .NET assembly
    $assemblyPath = if ($env:WINSCP_PATH) { $env:WINSCP_PATH } else { $PSScriptRoot }
    Add-Type -Path (Join-Path $assemblyPath "WinSCPnet.dll")
 
    # Setup session options
    $sessionOptions = New-Object WinSCP.SessionOptions
    $sessionOptions.ParseUrl($sessionUrl)
 
    $session = New-Object WinSCP.Session
 
    try
    {
        # Connect
        $session.Open($sessionOptions)
        
        Write-Host $remotePath
 
        # Calculate remote file checksum
        $remoteChecksum = [System.BitConverter]::ToString($session.CalculateFileChecksum("sha-1", $remotePath))
        Write-Host $remoteChecksum
    }
    finally
    {
        # Disconnect, clean up
        $session.Dispose()
    }
 
    # Compare cheksums
    if ($localChecksum -eq $remoteChecksum)
    {
        Write-Host "Match"
        $result = 0
    }
    else
    {
        Write-Host "Does NOT match"
        $result = 1
    }
}
catch [Exception]
{
    Write-Host $_.Exception.Message
    $result = 1
}
 
# Pause if -pause switch was used
if ($pause)
{
    Write-Host "Press any key to exit..."
    [System.Console]::ReadKey() | Out-Null
}
 
exit $result