authorization middleware

.gitignore

@@ -1,3 +1,3 @@
-vendor
-panelcli
-userpanel
+/vendor
+/panelcli
+/userpanel

Dockerfile

@@ -2,7 +2,7 @@ FROM golang:1.11-alpine as builder
 RUN apk --no-cache add git gcc musl-dev
 WORKDIR /go/src/git.lattuga.net/boyska/feedpanel/
 COPY ./ /go/src/git.lattuga.net/boyska/feedpanel/
-RUN CGO_ENABLED=0 GOOS=linux go install -v ./...
+RUN CGO_ENABLED=0 GOOS=linux go install ./...
 
 FROM busybox
 WORKDIR /usr/bin/

cmd/userpanel/main.go

@@ -3,13 +3,25 @@ package main
 import (
 	"fmt"
 	"net/http"
+
+	"github.com/urfave/negroni"
 )
 
 func main() {
-	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
-		w.WriteHeader(501)
-		fmt.Fprintf(w, "Nothing has been implemented. Just cross your fingers.\n")
+	mux := http.NewServeMux()
+	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+		user := r.Context().Value(keyUser)
+		if user == nil {
+			panic("Authentication middleware failed!")
+		}
+		w.WriteHeader(200)
+		fmt.Fprintf(w, "Hello, %s\n", user)
 	})
 
-	http.ListenAndServe(":8000", nil)
+	ha := HeaderAuth{AllowedNames: []string{"feedati-fe"}, RequireUser: true}
+	n := negroni.New(negroni.NewRecovery(), negroni.NewLogger(), ha)
+	n.UseHandler(mux)
+	addr := ":8000"
+	fmt.Println("Listening on", addr)
+	http.ListenAndServe(addr, n)
 }

cmd/userpanel/middleware.go

@@ -0,0 +1,76 @@
+package main
+
+import (
+	"context"
+	"net"
+	"net/http"
+)
+
+type ctxKey int
+
+const (
+	keyUser = iota
+)
+
+//HeaderAuth is a Negroni-compatible Middleware
+type HeaderAuth struct {
+	AllowedNames []string
+	AllowedIPs   []net.IP
+	RequireUser  bool
+}
+
+func _getSourceIP(req *http.Request) (net.IP, error) {
+	ip, _, err := net.SplitHostPort(req.RemoteAddr)
+	if err != nil {
+		return net.IP{}, err
+	}
+
+	userIP := net.ParseIP(ip)
+	if userIP == nil {
+		return net.IP{}, err
+	}
+	return userIP, nil
+}
+
+func (ha HeaderAuth) ServeHTTP(rw http.ResponseWriter, r *http.Request, next http.HandlerFunc) {
+	srcIP, err := _getSourceIP(r)
+	if err != nil {
+		rw.WriteHeader(501)
+		return
+	}
+	found := false
+	if len(ha.AllowedNames) == 0 && len(ha.AllowedIPs) == 0 {
+		found = true
+	}
+	if !found && len(ha.AllowedIPs) > 0 {
+		for _, allowedIP := range ha.AllowedIPs {
+			if allowedIP.Equal(srcIP) {
+				found = true
+				break
+			}
+		}
+	}
+	if !found && len(ha.AllowedNames) > 0 {
+		for _, name := range ha.AllowedNames {
+			nameips, err := net.LookupIP(name)
+			if err != nil {
+				continue
+			}
+			for _, allowedIP := range nameips {
+				if allowedIP.Equal(srcIP) {
+					found = true
+					break
+				}
+			}
+		}
+	}
+	user := r.Header.Get("X-Forwarded-User")
+	if !found || (ha.RequireUser && user == "") {
+		rw.WriteHeader(http.StatusUnauthorized)
+		return
+	}
+	ctx := r.Context()
+	ctx = context.WithValue(ctx, keyUser, user)
+	next(rw, r.WithContext(ctx))
+	return
+}

go.mod

@@ -7,6 +7,7 @@ require (
 	github.com/kr/pretty v0.1.0 // indirect
 	github.com/onsi/gomega v1.4.2 // indirect
 	github.com/pkg/errors v0.8.0
+	github.com/urfave/negroni v1.0.0
 	github.com/vmihailenco/sasl v0.0.0-20180913092844-58bfd2104008 // indirect
 	golang.org/x/crypto v0.0.0-20180910181607-0e37d006457b
 	gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127 // indirect

go.sum

@@ -21,6 +21,8 @@ github.com/onsi/gomega v1.4.2 h1:3mYCb7aPxS/RU7TI1y4rkEn1oKmPRjNJLNEXgw7MH2I=
 github.com/onsi/gomega v1.4.2/go.mod h1:ex+gbHU/CVuBBDIJjb2X0qEXbFg53c61hWP/1CpauHY=
 github.com/pkg/errors v0.8.0 h1:WdK/asTD0HN+q6hsWO3/vpuAkAr+tw6aNJNDFFf0+qw=
 github.com/pkg/errors v0.8.0/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
+github.com/urfave/negroni v1.0.0 h1:kIimOitoypq34K7TG7DUaJ9kq/N4Ofuwi1sjz0KipXc=
+github.com/urfave/negroni v1.0.0/go.mod h1:Meg73S6kFm/4PpbYdq35yYWoCZ9mS/YSx+lKnmiohz4=
 github.com/vmihailenco/sasl v0.0.0-20180913092844-58bfd2104008 h1:QvUVTr/4BCSyk46CIcYxDh5qQJbV65nWcMlv6whzm1Y=
 github.com/vmihailenco/sasl v0.0.0-20180913092844-58bfd2104008/go.mod h1:PL3B2VvrDEUUKvagXPKVvvmulVvRE2DWIJovqpdpHwI=
 golang.org/x/crypto v0.0.0-20180910181607-0e37d006457b h1:2b9XGzhjiYsYPnKXoEfL7klWZQIt8IfyRCz62gCqqlQ=