Merging FTP Extensibility Walkthroughs

Thursday, July 23, 2009

FTP

Over the past several months I’ve been publishing a series of walkthroughs that use the extensibility in FTP 7.5 to create a several custom providers for a variety of scenarios, and today I posted my most recent entry in the series:

How to Use Managed Code to Create an FTP Authentication Provider using an XML Database

As a piece of behind-the-scenes trivia, some of these walkthroughs were based off custom providers that I had actually written for my FTP servers, and I used the samples that I wrote for some of the other walkthroughs as a starting point for custom providers that I currently use. With that in mind, I’d like to use today’s blog to talk about some of the ways that I combine what you see in a few of these walkthroughs into some useful scenarios.

One of the common providers that I use is a combination of the code that you see in these two walkthroughs:

Here's the way that I create the provider - I start with a single provider class that implements the IFtpHomeDirectoryProvider, IFtpAuthenticationProvider, and IFtpRoleProvider interfaces, and I create a few global variables that I'll use later.

public class FtpXmlAuthentication : BaseProvider,
    IFtpHomeDirectoryProvider,
    IFtpAuthenticationProvider,
    IFtpRoleProvider
{
    private string _XmlFileName;

    private string _HomeDirectory;

    private Dictionary<string, XmlUserData> _XmlUserData =
        new Dictionary<string, XmlUserData>(
            StringComparer.InvariantCultureIgnoreCase);
}

I add an Initialize() method to the class, where I load the values named xmlFileName and homeDirectory from the configuration settings.

protected override void Initialize(StringDictionary config)
{
    _XmlFileName = config["xmlFileName"];
    _HomeDirectory = config["homeDirectory"];
    if (string.IsNullOrEmpty(_XmlFileName))
    {
        throw new ArgumentException("Missing xmlFileName value in configuration.");
    }
}

I recycle the provider across a bunch of different FTP sites, and I don't always use the custom home directory feature, so my GetUserHomeDirectoryData() method has to accommodate for that. (Note: this means that your FTP site has to use a method of User Isolation other than "Custom". You can find more information about User Isolation on the FTP User Isolation Page.)

string IFtpHomeDirectoryProvider.GetUserHomeDirectoryData(
    string sessionId,
    string siteName,
    string userName)
{
    if (string.IsNullOrEmpty(_HomeDirectory))
    {
        throw new ArgumentException("Missing homeDirectory value in configuration.");
    }
    return _HomeDirectory;
}
(Note: While it may seem that I could throw the ArgumentException() in the Initialize() method, since I don't always need this value for providers that don't implement the home directory lookup it's best to throw the exception in the GetUserHomeDirectoryData() method.)

The last thing that I do for the provider is to copy the AuthenticateUser(), IsUserInRole(), ReadXmlDataStore(), GetInnerText() methods and XmlUserData class from the How to Use Managed Code to Create an FTP Authentication Provider using an XML Database walkthrough. This gives me a custom FTP authentication provider that provides user, role, and home directory lookups. This means the XML file for the provider registration has to vary a little from the walkthroughs in order to define settings for the xmlFileName and homeDirectory values. Here's an example of that that might look like:

<system.ftpServer>
    <providerDefinitions>
        <add name="ContosoXmlAuthentication" type="FtpXmlAuthentication,FtpXmlAuthentication,version=1.0.0.0,Culture=neutral,PublicKeyToken=426f62526f636b73" />
        <activation>
            <providerData name="ContosoXmlAuthentication">
                <add key="xmlFileName" value="C:\Inetpub\www.contoso.com\Users.xml" />
                <add key="homeDirectory" value="C:\Inetpub\www.contoso.com\ftproot" />
            </providerData>
        </activation>
    </providerDefinitions>

    <!-- Other XML goes here -->

</system.ftpServer>

The last thing that you need to do is to create the XML file that contains the usernames and passwords, which you can copy from the How to Use Managed Code to Create an FTP Authentication Provider using an XML Database walkthrough.

I use this provider on multiple FTP sites, so I simply re-register the provider under a different name and specify different values for the xmlFileName and homeDirectory values:

<system.ftpServer>
    <providerDefinitions>
        <add name="ContosoXmlAuthentication" type="FtpXmlAuthentication,FtpXmlAuthentication,version=1.0.0.0,Culture=neutral,PublicKeyToken=426f62526f636b73" />
        <add name="FabrikamXmlAuthentication" type="FtpXmlAuthentication,FtpXmlAuthentication,version=1.0.0.0,Culture=neutral,PublicKeyToken=426f62526f636b73" />
        <add name="WingTipToysXmlAuthentication" type="FtpXmlAuthentication,FtpXmlAuthentication,version=1.0.0.0,Culture=neutral,PublicKeyToken=426f62526f636b73" />
        <activation>
            <providerData name="ContosoXmlAuthentication">
                <add key="xmlFileName" value="C:\Inetpub\www.Contoso.com\Users.xml" />
                <add key="homeDirectory" value="C:\Inetpub\www.Contoso.com\ftproot" />
            </providerData>
            <providerData name="FabrikamXmlAuthentication">
                <add key="xmlFileName" value="C:\Inetpub\www.Fabrikam.com\Users.xml" />
                <add key="homeDirectory" value="C:\Inetpub\www.Fabrikam.com\ftproot" />
            </providerData>
            <providerData name="WingTipToysXmlAuthentication">
                <add key="xmlFileName" value="C:\Inetpub\www.WingTipToys.com\Users.xml" />
                <add key="homeDirectory" value="C:\Inetpub\www.WingTipToys.com\ftproot" />
            </providerData>
        </activation>
    </providerDefinitions>

    <!-- Other XML goes here -->

</system.ftpServer>

So in the end I have a provider that provides unique users, roles, and home directory for each FTP site. I point the FTP root to a path that is outside of the HTTP root, so my users can upload files for an application like a photo gallery that I provide them, but they can't access the actual ASP.NET files for the application. Since they're using accounts from the XML file, I don't have to hand out physical accounts on my servers or my domain. (The security-paranoid side of my personality really likes that.)

For some sites I use the XML file for ASP.NET membership by following the instructions in the How to use the Sample Read-Only XML Membership and Role Providers with IIS 7.0 walkthrough. In those cases, I move the XML file into the App_Data folder of the web site. Once again, since the FTP root is different than the HTTP root, this prevents any of my FTP users from accessing the XML file and making changes to it. (Although you could do that if you wanted to allow one of your users to update the list of FTP users for their site. But as you can imagine, the security-paranoid side of my personality really does not like that.)

All that being said, I hope that this helps you to get an idea for other ways that you can use some of the walkthroughs that I've been writing. I have several additional providers and walkthroughs that I’m working on for the IIS.NET web site, but I’ll keep those as a secret for now. ;-]

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