Step by step: Expose ASP.NET Core over HTTPS with Docker

Table of Contents

This week I decided to modify the sample of my previous post: Step by step: Scale ASP.NET Core with Docker Swarm so you can add TLS to your ASP.NET Core applications and Dockerize it.

Let’s see how I changed the application in order to make it work:

Add HTTPS support for Kestrel
#

I added the following line to the dependencies in the project.json file.

    "Microsoft.AspNetCore.Server.Kestrel.Https": "1.0.1",

Configure Kestrel to use HTTPS
#

In the Main method I configured Kestrel to use HTTPS. Don’t worry about the cert.pfx certificate file because it will be created inside the docker container.

Note that in line 8 I also configured the application to use port 443.

    public static void Main(string[] args)
    {
        var host = new WebHostBuilder()
            .UseKestrel((o) => 
            {
                o.UseHttps(new X509Certificate2(@"cert.pfx", Configuration["certPassword"]));
            })
            .UseUrls("https://*:443")
            .UseContentRoot(Directory.GetCurrentDirectory())
            .UseStartup<Startup>()
            .Build();

        host.Run();
    }

Now It’s time to show you how to Dockerize the application:

Create a dockerfile
#

# We use the microsoft/dotnet image as a starting point.
FROM microsoft/dotnet 

# Install git
RUN apt-get install git -y

# Clone the source code
RUN git clone -b ssl https://github.com/cmendible/aspnet-core-helloworld.git

# Set our working folder
WORKDIR aspnet-core-helloworld/src/dotnetstarter

# Restore nuget packages
RUN dotnet restore

# Build the application using dotnet!!!
RUN dotnet build

# Set password for the certificate as 1234
# I'm using Environment Variable here to simplify the .NET Core sample.
ENV certPassword 1234

# Use opnssl to generate a self signed certificate cert.pfx with password $env:certPassword
RUN openssl genrsa -des3 -passout pass:${certPassword} -out server.key 2048
RUN openssl rsa -passin pass:${certPassword} -in server.key -out server.key
RUN openssl req -sha256 -new -key server.key -out server.csr -subj '/CN=localhost'
RUN openssl x509 -req -sha256 -days 365 -in server.csr -signkey server.key -out server.crt
RUN openssl pkcs12 -export -out cert.pfx -inkey server.key -in server.crt -certfile server.crt -passout pass:${certPassword}

# Expose port 443 for the application.
EXPOSE 443

# Start the application using dotnet!!!
ENTRYPOINT dotnet run

Create a Docker image
#

With the dockerfile in place run the following command

sudo docker build -t httpssample .

Now you have an image named httpssample with all the dependencies and code needed to run the application.

Test the Docker image
#

To test the Docker image run the following command

sudo docker run -it -p 443:443 httpssample

Browse to https://localhost Your browser will warn about the certificate because it’s self signed.

Run the Docker image as a daemon process
#

Now that you know that everything is working as expected use the following command to run the Docker image as a daemon process

docker run -t -d -p 443:443 httpssample

You can get a copy of the docker file here: https://github.com/cmendible/dotnetcore.samples/tree/main/docker.helloworld.https

Hope it helps!

Add HTTPS support for Kestrel#

Configure Kestrel to use HTTPS#

Create a dockerfile#

Create a Docker image#

Test the Docker image#

Run the Docker image as a daemon process#