Protecting credentials used for automation

In script, you can replace actual credentials with reference to environment variables. You can then call WinSCP from a batch file that sets these variables. The batch file itself then serves as a “configuration file”.

For example, the following script (example.txt)2:

open -username=%USERNAME% -password=%PASSWORD% sftp://example.com/
...

can be called from this batch file (“configuration file”):

@echo off
set USERNAME=martin
set PASSWORD=mypassword
winscp.com /script=example.txt

Another way is to store the password to a separate file and use -passwordsfromfiles:

open -password=C:\path\password.txt -passwordsfromfiles sftp://username@example.com/

In .NET projects (C#, VB.NET) an application configuration file (App.config) is used to store the settings. Though this file contains other configuration that needs to be shared and/or stored in a revision control system. To separate the credentials from other settings, you can link another configuration file like shown below.

Use the file attribute of appSettings element in the primary application configuration file (App.config):

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <startup> 
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5.2" />
  </startup>
  <appSettings file="ProtectedConfig.config">
    <!-- other settings -->
  </appSettings>
</configuration>

Add a new XML file to the project and name it ProtectedConfig.config:

<?xml version="1.0" encoding="utf-8" ?>
<appSettings>
  <add key="UserName" value="martin" />
  <add key="Password" value="test" />
</appSettings>

Set the Copy to Output Directory property of the file to Copy if newer and the Build Action to Content to have the new configuration file correctly deployed.

To read the settings from the configuration file use ConfigurationManager.AppSettings:3

SessionOptions sessionOptions = new SessionOptions
{
    Protocol = Protocol.Sftp,
    HostName = "example.com",
    UserName = ConfigurationManager.AppSettings["UserName"],
    Password = ConfigurationManager.AppSettings["Password"],
};

You can also leverage Windows Data Protection API to encrypt the password in the XML file.

If you want to encrypt the password within the configuration file, you can use use PowerShell ConvertFrom-SecureString cmdlet:

powershell.exe -Command "& Read-Host -AsSecureString | ConvertFrom-SecureString"

A password encrypted this way can be decrypted by the same Windows account only.

Store the encrypted password to the XML file instead of the plain-text one:

<?xml version="1.0" encoding="utf-8" ?>
<appSettings>
  <add key="UserName" value="martin" />
  <add key="Password" value="01000000d08c9ddf0115d1118c7a00c04fc297eb01000000cf6dbc52515..." />
</appSettings>

To decrypt the password, use ProtectedData.Unprotect:4

string hex = ConfigurationManager.AppSettings["Password"];
byte[] bytes =
    Enumerable.Range(0, hex.Length / 2).
        Select(x => Convert.ToByte(hex.Substring(x * 2, 2), 16)).ToArray();
byte[] decrypted = ProtectedData.Unprotect(bytes, null, DataProtectionScope.CurrentUser);
sessionOptions.Password = Encoding.Unicode.GetString(decrypted);

In SSIS, you can configure script variables in SSIS > Variables. To make them accessible from the script task, in the context menu of the task, choose Edit. On the Script task editor on Script page, select ReadOnlyVariables, and tick the below properties.

See SSIS example.

Instead of storing credentials (username and password) individually, you can use a single string, the session URL (a kind of “connection string”). This gives you an additional flexibility of changing even protocol by mere configuration.

Use the SessionOptions.ParseUrl to parse the URL into individual components.

You can change the above PowerShell example as below.

The configuration file:

<Configuration>
  <SessionUrl>sftp://martin:mypassword@example.com/</SessionUrl>
</Configuration>

The code:

# Read XML configuration file
[xml]$config = Get-Content ".\config.xml"
 
# Use read credentials
$sessionOptions = New-Object WinSCP.SessionOptions
$sessionOptions.ParseUrl($config.Configuration.SessionUrl)
 
...

You can apply the same technique to the above C# example.

Only if you want to encrypt the password as shown in the previous sections, you need to separate the password from the rest of the session URL. First call the SessionOptions.ParseUrl and then separately set the SessionOptions.Password.