In the beginning the was darkness and then there was a reverse proxy.

.drone.yml

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+---
+kind: pipeline
+name: test
+
+steps:
+- name: test-code
+  image: golang
+  commands:
+    - go get
+    - go test
+
+---
+kind: pipeline
+name: test-build
+
+steps:
+- name: prepare
+  image: golang
+  commands:
+    - go version
+
+- name: build-linux-amd64
+  image: golang
+  environment:
+    GOOS: linux
+    GOARCH: amd64
+  commands:
+    - go get
+    - go build -o sidoxy-linux-amd64-${DRONE_COMMIT_SHA:0:8}
+  depends_on:
+    - prepare
+
+depends_on:
+  - test
+
+---
+kind: pipeline
+name: build
+
+steps:
+- name: prepare
+  image: golang
+  commands:
+    - mkdir bin/
+
+- name: build-linux-amd64
+  image: golang
+  environment:
+    GOOS: linux
+    GOARCH: amd64
+  commands:
+    - go get
+    - go build -o bin/sidoxy-linux-amd64-${DRONE_TAG}
+  depends_on:
+    - prepare
+
+- name: generate-checksum
+  image: golang
+  commands:
+    - cd bin
+    - md5sum * > ../md5sums.txt
+    - sha512sum * > ../sha512sums.txt
+    - cp ../md5sums.txt .
+    - cp ../sha512sums.txt .
+  depends_on:
+    - build-linux-amd64
+
+- name: gitea_release
+  image: plugins/gitea-release
+  settings:
+    title: Release ${DRONE_TAG}
+    note: This is the cmw release of version ${DRONE_TAG}
+    api_key:
+      from_secret:
+        gitea_release
+    base_url: https://scm.project42.io
+    files: bin/*
+  depends_on:
+    - generate-checksum
+
+depends_on:
+  - test-build
+
+trigger:
+  event:
+    - tag

.gitignore

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+.envrc
+go.sum

README.md

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+Sidoxy
+======
+
+`Sidoxy` is a simple proxy written in [Go](https://go.dev/).

env.go

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+package main
+
+import (
+	"os"
+)
+
+func getEnvironmentVariables() (proxyHostURL, proxyServerURL, jwtKey string) {
+	proxyHostURL = os.Getenv("PROXY_HOST_URL")
+	proxyServerURL = os.Getenv("PROXY_SERVER_URL")
+	jwtKey = os.Getenv("PROXY_JWT_KEY")
+	return
+}

go.mod

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+module sidoxy
+
+go 1.20
+
+require github.com/golang-jwt/jwt/v5 v5.0.0

main.go

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+package main
+
+import (
+	"fmt"
+	"log"
+)
+
+func main() {
+
+	proxyHostURL, proxyServerURL, jwtKey := getEnvironmentVariables()
+
+	// define origin server URL
+	originServerURL := parse_url(proxyServerURL)
+	reverseProxy := &ReverseProxy{URL: originServerURL, jwtKey: jwtKey}
+
+	fmt.Printf("[sidoxy] Listening on \"%s\"\n", proxyHostURL)
+	fmt.Printf("[sidoxy] Forwarding to \"%s\"\n", proxyServerURL)
+	fmt.Printf("[sidoxy] jwtKey is \"%s\"\n", jwtKey)
+	log.Fatal(listen_and_serve(proxyHostURL, reverseProxy.reverseProxyHandlerFunc()))
+
+}

proxy.go

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+package main
+
+import (
+	"fmt"
+	"io"
+	"net"
+	"log"
+	"net/http"
+	"net/url"
+	"time"
+)
+
+type ReverseProxy struct {
+	URL    *url.URL
+	jwtKey string
+}
+
+func (rp *ReverseProxy) reverseProxyHandlerFunc() http.Handler {
+	return http.HandlerFunc(rp.reverseProxyHandler)
+}
+
+func (rp *ReverseProxy) reverseProxyHandler(rw http.ResponseWriter, req *http.Request) {
+	fmt.Printf("[sidoxy] Reverse proxy received request at: %s\n", time.Now())
+
+	// set req Host, URL and Request URI to forward a request to the origin server
+	req.Host = rp.URL.Host
+	req.URL.Host = rp.URL.Host
+	req.URL.Scheme = rp.URL.Scheme
+	req.RequestURI = ""
+
+	// set X-FORWARDED-FOR
+	xForwardedFor := req.Header.Get("X-Forwarded-For")
+	var remoteAddr string
+	if xForwardedFor != "" {
+		remoteAddr = xForwardedFor
+	} else {
+		remoteAddr, _, _ = net.SplitHostPort(req.RemoteAddr)
+	}
+	req.Header.Set("X-Forwarded-For", remoteAddr)
+	fmt.Printf("[sidoxy] Reverse proxy setting X-Forwarded-For to %s\n", remoteAddr)
+
+	// TODO: To be implemented
+	// decode JWT if key present
+	if rp.jwtKey != "" {
+		jwtDecode(rp.jwtKey, req.Header.Get("JWT_TOKEN"), req)
+	}
+
+	// save the response from the origin server
+	originServerResponse, err := http.DefaultClient.Do(req)
+	if err != nil {
+		rw.WriteHeader(http.StatusInternalServerError)
+		_, _ = fmt.Fprint(rw, err)
+		return
+	}
+
+	fmt.Printf("[sidoxy] Reverse proxy setting the following return headers\n")
+	// return Header response
+	for key, values := range originServerResponse.Header {
+		for _, value := range values {
+			fmt.Printf("[sidoxy] \t%v: %v\n", key, value)
+			rw.Header().Set(key, value)
+		}
+	}
+
+	// support stream
+	done := make(chan bool)
+	defer close(done)
+	go func() {
+		for {
+			select {
+			case <-time.Tick(10 * time.Millisecond):
+				rw.(http.Flusher).Flush()
+			case <-done:
+				return
+			}
+		}
+	}()
+
+	// return response to the client
+	rw.WriteHeader(http.StatusOK)
+	io.Copy(rw, originServerResponse.Body)
+}
+
+func parse_url(host_url string) *url.URL {
+	h_url, err := url.Parse(host_url)
+	if err != nil {
+		log.Fatal("[sidoxy] Invalid server URL: %v", host_url)
+	}
+	return h_url
+}
+
+func listen_and_serve(address string, handler http.Handler) error {
+	return http.ListenAndServe(address, handler)
+}

server.sh

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+docker run --rm -it -p 8080:80 strm/helloworld-http

token.go

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+package main
+
+import (
+	"fmt"
+	"log"
+	"net/http"
+
+	jwt "github.com/golang-jwt/jwt/v5"
+)
+
+func jwtDecode(jwtKey string, jwtToken string, req *http.Request) {
+	claims := jwt.MapClaims{}
+	token, err := jwt.ParseWithClaims(jwtToken, claims, func(token *jwt.Token) (interface{}, error) {
+		return []byte(jwtKey), nil
+	})
+	if err != nil {
+		log.Panic("Failed to parse JWT:\n", err, "\n")
+	}
+
+	if token != nil {
+		log.Panic("Failed to parse JWT token:\n", token, "\n")
+	}
+
+	// do something with decoded claims
+	for key, val := range claims {
+		req.Header.Set(key, fmt.Sprint(val))
+		fmt.Printf("Key: %v, value: %v\n", key, val)
+	}
+}