HTTP proxy written in Go to replace Tinyproxy (#269)

internal/httpproxy/auth.go

@@ -0,0 +1,33 @@
+package httpproxy
+
+import (
+	"encoding/base64"
+	"net/http"
+	"strings"
+)
+
+func isAuthorized(responseWriter http.ResponseWriter, request *http.Request,
+	username, password string) (authorized bool) {
+	basicAuth := request.Header.Get("Proxy-Authorization")
+	if len(basicAuth) == 0 {
+		responseWriter.WriteHeader(http.StatusProxyAuthRequired)
+		return false
+	}
+	b64UsernamePassword := strings.TrimPrefix(basicAuth, "Basic ")
+	b, err := base64.StdEncoding.DecodeString(b64UsernamePassword)
+	if err != nil {
+		responseWriter.WriteHeader(http.StatusUnauthorized)
+		return false
+	}
+	usernamePassword := strings.Split(string(b), ":")
+	const expectedFields = 2
+	if len(usernamePassword) != expectedFields {
+		responseWriter.WriteHeader(http.StatusBadRequest)
+		return false
+	}
+	if username != usernamePassword[0] && password != usernamePassword[1] {
+		responseWriter.WriteHeader(http.StatusUnauthorized)
+		return false
+	}
+	return true
+}