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Web eID ASP.NET example

European Regional Development Fund

This project is an example ASP.NET web application that shows how to implement strong authentication and digital signing with electronic ID smart cards using Web eID.

More information about the Web eID project is available on the project website.

The ASP.NET web application makes use of the following technologies:

Quickstart

Complete the steps below to run the example application in order to test authentication and digital signing with Web eID.

1. Configure the origin URL

One crucial step of the Web eID authentication token validation algorithm is verifying the token signature. The value that is signed contains the site origin URL (the URL serving the web application) to protect against man-in-the-middle attacks. Hence the site origin URL must be configured in application settings.

To configure the origin URL, add OriginUrl field in the application settings file appsettings.json as follows:

{
  "OriginUrl": "https://example.org"
}

Note that the URL must not end with a slash /.

2. Configure the trusted certificate authority certificates

The algorithm, which performs the validation of the Web eID authentication token, needs to know which intermediate certificate authorities (CA) are trusted to issue the eID authentication certificates. CA certificates are loaded from .cer files in the profile-specific subdirectory of the Certificates resource directory. By default, Estonian eID test CA certificates are included in the Development profile and production CA certificates in the Production profile.

In case you need to provide your own CA certificates, add the .cer files to the src/WebEid.AspNetCore.Example/Certificates/{Dev,Prod} profile-specific directory.

3. Setup the libdigidocpp library for signing

libdigidocpp is a library for creating, signing and verifying digitally signed documents according to XAdES and XML-DSIG standards. It is a C++ library that has SWIG bindings for C#.

Set up the libdigidocpp library as follows:

  1. Install the libdigidocpp-3.14.4.msi package or higher. The installation packages are available from https://github.com/open-eid/libdigidocpp/releases.
  2. Copy the C# source files from the libdigidocpp installation folder include\digidocpp_csharp to the src\WebEid.AspNetCore.Example\DigiDoc folder.
  3. Copy all files from either the x64 subfolder of the libdigidocpp installation folder to the example application build output folder bin\...\net60 (after building, see next step). When building custom applications, choose x64 if your application is 64-bit and x86 if it is 32-bit.
  4. When running in the Development profile, create an empty file named EE_T.xml for TSL cache as described in the Using test TSL lists section of the libdigidocpp wiki.

Further information is available in the libdigidocpp example C# application and in the libdigidocpp wiki.

4. Build the application

You need to have the .NET 6.0 SDK installed for building the application package. Build the application by running the following command in a terminal window under the src directory:

dotnet build

5. Choose either the Development or Production profile

If you have a test eID card, use the Development profile. In this case access to paid services is not required, but you need to upload the authentication and signing certificates of the test card to the test OCSP responder database as described in section Using DigiDoc4j in test mode with the dev profile of the Web eID Java example application documentation. TheDevelopment profile is activated by default.

If you only have a production eID card, use the Production profile. You can still test authentication without further configuration; however, for digital signing to work, you need access to a paid timestamping service as described in section Using DigiDoc4j in production mode with the prod profile of the Web eID Java example documentation.

You can specify the profile as an environment variable ASPNETCORE_ENVIRONMENT when running the application. To set the profile for the current session before starting the app using dotnet run, use the following command:

set ASPNETCORE_ENVIRONMENT=Production

6. Run the application

Run the application with the following command in a terminal window under the src directory:

dotnet run --project WebEid.AspNetCore.Example

This will activate the default Development profile and launch the built-in kestrel web server on HTTPS port 5001.

When the application has started, open https://localhost:5001 in your preferred web browser and follow instructions on the front page.

Overview of the source code

The src\WebEid.AspNetCore.Example directory contains the ASP.NET application source code and resources. The subdirectories therein have the following purpose:

  • wwwroot: web server static content, including CSS and JavaScript files,
  • Certificates: CA certificates in profile-specific subdirectories,
  • Controllers: ASP.NET MVC controller for the welcome page and Web API controllers that provide endpoints for
    • getting the challenge nonce used by the authentication token validation library,
    • logging in,
    • digital signing,
  • DigiDoc: contains the C# binding files of the libdigidocpp library; these files must be copied from the libdigidocpp installation directory \include\digidocpp_csharp,
  • Pages: Razor pages,
  • Services: Web eID signing service implementation that uses libdigidocpp.

More information

See the Web eID Java example application documentation for more information, including answers to questions not answered below.

Frequently asked questions

Why do I get the System.ApplicationException: Failed to verify OCSP Responder certificate error during signing?

You are running in the Development profile, but you have not created an empty file named EE_T.xml for TSL cache. Creating the file is mandatory and is described in more detail in the Using test TSL lists section of the libdigidocpp wiki.

Why do I get the System.BadImageFormatException: An attempt was made to load a program with an incorrect format error during signing?

You are using libdigidocpp DLLs for the wrong architecture. Copy files from the x64 subfolder of the libdigidocpp installation folder to right place as described in the section 3. Setup the libdigidocpp library for signing above. In case you get this error while developing a custom 32-bit application, copy files from the x86 subfolder instead.

Building and running with Docker on Ubuntu Linux

This section covers the steps required to build the application on an Ubuntu Linux environment and run it using Docker.

Prerequisites

Before you begin, ensure you have the following installed on your system:

  • .NET SDK 7.0
  • libdigidocpp-csharp

You can install them using the following command:

sudo apt install dotnet-sdk-7.0 libdigidocpp-csharp

Building the application

To build the application, follow these steps:

  1. Navigate to the src directory:

    cd src
  2. Copy the necessary DigiDoc C# library files into your project:

    cp /usr/include/digidocpp_csharp/* WebEid.AspNetCore.Example/DigiDoc/
  3. Publish the application with the Release configuration:

    dotnet publish --configuration Release WebEid.AspNetCore.Example.sln
  4. Update the OriginUrl in the appsettings.json to match your production environment:

    sed -i 's#"OriginUrl": "https://localhost:44391"#"OriginUrl": "https://example.com"#' WebEid.AspNetCore.Example/bin/Release/net6.0/publish/appsettings.json

Building the Docker image

After successfully building the application, you can create a Docker image:

docker build -t web-eid-asp-dotnet-example .

This command builds a Docker image named web-eid-asp-dotnet-example using the Dockerfile in the current directory.

Running the Docker container with HTTPS support

To enable HTTPS support for the .NET application, you have two primary options:

  1. Directly configure Kestrel to use HTTPS by setting up the necessary certificate information in the app's configuration files. This method is detailed in the ASP.NET Core documentation.

  2. Employ a reverse proxy that manages TLS termination and forwards requests to the application over HTTP. This is a common pattern in production environments due to its flexibility.

In this project, we assume the application is running behind a reverse proxy.

First, the proxy server must pass the Host: line from the incoming request to the proxied application and set the X-Forwarded-* headers to inform the application that it runs behind a reverse proxy. Here is example configuration for the Apache web server:

<Location />
    ProxyPreserveHost On
    ProxyPass http://localhost:8480/
    ProxyPassReverse http://localhost:8480/
    RequestHeader set X-Forwarded-Proto https
    RequestHeader set X-Forwarded-Port 443
</Location>

Next, the .NET application must be configured to recognize and honor the X-Forwarded-* headers. This can be done by configuring the Forwarded Headers middleware in Startup.cs:

app.UseForwardedHeaders(new ForwardedHeadersOptions
{
    ForwardedHeaders = ForwardedHeaders.XForwardedFor | ForwardedHeaders.XForwardedProto
});

By default, this middleware is already enabled in the application.

A Docker Compose configuration file docker-compose.yml is available in the src directory for running the Docker image web-eid-asp-dotnet-example on port 8480 behind a reverse proxy.

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Example ASP.NET web application that uses Web eID for secure authentication and digital signing with electronic ID smart cards

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