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How to set up ASP.NET Core Web API using Nginx as reverse proxy for SSL termination
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Anthony Sneed
Anthony Sneed Add SSL to Nginx
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ReadMe.md

ASP.NET Core 3.0 Web API with Nginx Reverse Proxy for SSL

Prerequisites

Web API Application

  • Create a new Web API application.
mkdir HelloAspNetCore3 && cd HelloAspNetCore3
dotnet new sln --name HelloAspNetCore3
dotnet new webapi --name HelloAspNetCore3.Api
dotnet sln add HelloAspNetCore3.Api/HelloAspNetCore3.Api.csproj
  • Insert the following code in the Configure method of Startup, after app.UseDeveloperExceptionPage.
app.UseForwardedHeaders(new ForwardedHeadersOptions
{
    ForwardedHeaders = ForwardedHeaders.XForwardedFor | ForwardedHeaders.XForwardedProto
});

Web API Container

  • Add Api.Dockerfile to the Web API project.
FROM mcr.microsoft.com/dotnet/core/aspnet:3.0-alpine AS base
WORKDIR /app

FROM mcr.microsoft.com/dotnet/core/sdk:3.0-alpine AS build
WORKDIR /src
COPY ["HelloAspNetCore3.Api.csproj", "./"]
RUN dotnet restore "./HelloAspNetCore3.Api.csproj"
COPY . .
WORKDIR "/src/."
RUN dotnet build "HelloAspNetCore3.Api.csproj" -c Release -o /app/build

FROM build AS publish
RUN dotnet publish "HelloAspNetCore3.Api.csproj" -c Release -o /app/publish

FROM base AS final
WORKDIR /app
COPY --from=publish /app/publish .
ENV ASPNETCORE_URLS http://*:5000
ENTRYPOINT ["dotnet", "HelloAspNetCore3.Api.dll"]
  • Open terminal at Web API project folder, build then run the container image.
docker build -t hello-aspnetcore3 -f Api.Dockerfile .
docker run -d -p 5000:5000 --name hello-aspnetcore3  hello-aspnetcore3
  • Browse to: http://localhost:5000/weatherforecast

Note: You need to build and run individual containers only to validate the image and application. The container and image can then me removed.

  • Stop and remove the container and image.
docker rm -f hello-aspnetcore3
docker rmi hello-aspnetcore3

Nginx Container

  • Add Nginx folder at the solution level.
  • Add nginx.conf file.
worker_processes 1;

events { worker_connections 1024; }

http {

    sendfile on;

    upstream web-api {
        server api:5000;
    }

    server {
        listen 80;
        server_name $hostname;
        location / {
            proxy_pass         http://web-api;
            proxy_redirect     off;
            proxy_http_version 1.1;
            proxy_cache_bypass $http_upgrade;
            proxy_set_header   Upgrade $http_upgrade;
            proxy_set_header   Connection keep-alive;
            proxy_set_header   Host $host;
            proxy_set_header   X-Real-IP $remote_addr;
            proxy_set_header   X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header   X-Forwarded-Proto $scheme;
            proxy_set_header   X-Forwarded-Host $server_name;
        }
    }
}
  • Add Nginx.Dockerfile file.
FROM nginx:latest

COPY nginx.conf /etc/nginx/nginx.conf

Docker Compose

  • Add docker-compose.yml at the solution level.
version: "3.7"

services:

  reverseproxy:
    build:
      context: ./Nginx
      dockerfile: Nginx.Dockerfile
    ports:
      - "80:80"
    restart: always

  api:
    depends_on:
      - reverseproxy
    build:
      context: ./HelloAspNetCore3.Api
      dockerfile: Api.Dockerfile
    expose:
      - "5000"
    restart: always

Note: Specifying depends_on for the api service places it in the same bridge network as reverseproxy, so that nginx can forward requests to it via proxy_pass. For this to work, the api service name must match the upstream server specified in the nginx.conf file. While reverseproxy is exposed to the host via ports, api is only exposed to reverseproxy.

  • Build api and reverseproxy images.
docker-compose build
  • Run the containers via docker-compose.
docker-compose up -d
  • Browse to http://localhost/weatherforecast
  • Stop the containers.
docker-compose down

SSL Setup

  • Add localhost.conf to Nginx folder.
[req]
default_bits       = 2048
default_keyfile    = localhost.key
distinguished_name = req_distinguished_name
req_extensions     = req_ext
x509_extensions    = v3_ca

[req_distinguished_name]
countryName                 = Country Name (2 letter code)
countryName_default         = US
stateOrProvinceName         = State or Province Name (full name)
stateOrProvinceName_default = Texas
localityName                = Locality Name (eg, city)
localityName_default        = Dallas
organizationName            = Organization Name (eg, company)
organizationName_default    = localhost
organizationalUnitName      = organizationalunit
organizationalUnitName_default = Development
commonName                  = Common Name (e.g. server FQDN or YOUR name)
commonName_default          = localhost
commonName_max              = 64

[req_ext]
subjectAltName = @alt_names

[v3_ca]
subjectAltName = @alt_names

[alt_names]
DNS.1   = localhost
DNS.2   = 127.0.0.1
  • Open terminal at Nginx folder to create certificate using OpenSSL.
    • Enter Strong@Passw0rd when prompted for export password.
sudo openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout localhost.key -out localhost.crt -config localhost.conf -passin pass:Strong@Passw0rd
sudo openssl pkcs12 -export -out localhost.pfx -inkey localhost.key -in localhost.crt
  • Add the certificate to the trusted CA root store.
    • Open the KeyChain Access app (spotlight on MacOS).
    • Select System in the Keychains pane, and drag your .pfx certificate into the certificate list pane.
    • Double-click your certificate, and under the trust section select Always Trust.
  • Update Nginx.Dockerfile to copy public and private key files.
COPY localhost.crt /etc/ssl/certs/localhost.crt
COPY localhost.key /etc/ssl/private/localhost.key
  • Update nginx.conf to load certificate key pair.
worker_processes 1;

events { worker_connections 1024; }

http {

    sendfile on;

    upstream web-api {
        server api:5000;
    }

    server {
        listen 80;
        server_name localhost;

        location / {
            return 301 https://$host$request_uri;
        }
    }

    server {
        listen 443 ssl;
        server_name localhost;

        ssl_certificate /etc/ssl/certs/localhost.crt;
        ssl_certificate_key /etc/ssl/private/localhost.key;

        location / {
            proxy_pass         http://web-api;
            proxy_redirect     off;
            proxy_http_version 1.1;
            proxy_cache_bypass $http_upgrade;
            proxy_set_header   Upgrade $http_upgrade;
            proxy_set_header   Connection keep-alive;
            proxy_set_header   Host $host;
            proxy_set_header   X-Real-IP $remote_addr;
            proxy_set_header   X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header   X-Forwarded-Proto $scheme;
            proxy_set_header   X-Forwarded-Host $server_name;
        }
    }
}
  • Edit docker-compose.yml to map reverseproxy to port 443.
ports:
  - "80:80"
  - "443:443"
  • Build images and run containers.
docker-compose build
docker-compose up -d
docker-compose down
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