refactor: rewrite auth handler code (!89)

* Rewrite the code handling basic auth to make it easier to extend for other types of auth.
* The behaviour of the existing code is maintained.
* No changes to how basic auth is configured from a user's perspective.

https://gitlab.com/hectorjsmith/fail2ban-prometheus-exporter/-/merge_requests/89

auth/basic.go

@@ -0,0 +1,29 @@
+package auth
+
+import (
+	"fmt"
+	"net/http"
+)
+
+func NewBasicAuthProvider(username, password string) AuthProvider {
+	return &basicAuthProvider{
+		hashedAuth: encodeBasicAuth(username, password),
+	}
+}
+
+type basicAuthProvider struct {
+	hashedAuth string
+}
+
+func (p *basicAuthProvider) IsAllowed(request *http.Request) bool {
+	username, password, ok := request.BasicAuth()
+	if !ok {
+		return false
+	}
+	requestAuth := encodeBasicAuth(username, password)
+	return p.hashedAuth == requestAuth
+}
+
+func encodeBasicAuth(username, password string) string {
+	return HashString(fmt.Sprintf("%s:%s", username, password))
+}

auth/basic_test.go

@@ -0,0 +1,53 @@
+package auth
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+func Test_GIVEN_BasicAuthSet_WHEN_CallingIsAllowedWithCorrectCreds_THEN_TrueReturned(t *testing.T) {
+	// assemble
+	username := "u1"
+	password := HashString("abc")
+	request := httptest.NewRequest(http.MethodGet, "http://example.com", nil)
+	request.SetBasicAuth(username, password)
+	provider := NewBasicAuthProvider(username, password)
+
+	// act
+	result := provider.IsAllowed(request)
+
+	// assert
+	if !result {
+		t.Errorf("expected request to be allowed, but failed")
+	}
+}
+
+func Test_GIVEN_BasicAuthSet_WHEN_CallingIsAllowedWithoutCreds_THEN_FalseReturned(t *testing.T) {
+	// assemble
+	request := httptest.NewRequest(http.MethodGet, "http://example.com", nil)
+	provider := NewBasicAuthProvider("u1", "p1")
+
+	// act
+	result := provider.IsAllowed(request)
+
+	// assert
+	if result {
+		t.Errorf("expected request to be denied, but was allowed")
+	}
+}
+
+func Test_GIVEN_BasicAuthSet_WHEN_CallingIsAllowedWithWrongCreds_THEN_FalseReturned(t *testing.T) {
+	// assemble
+	request := httptest.NewRequest(http.MethodGet, "http://example.com", nil)
+	request.SetBasicAuth("wrong", "pw")
+	provider := NewBasicAuthProvider("u1", "p1")
+
+	// act
+	result := provider.IsAllowed(request)
+
+	// assert
+	if result {
+		t.Errorf("expected request to be denied, but was allowed")
+	}
+}

auth/empty.go

@@ -0,0 +1,14 @@
+package auth
+
+import "net/http"
+
+func NewEmptyAuthProvider() AuthProvider {
+	return &emptyAuthProvider{}
+}
+
+type emptyAuthProvider struct {
+}
+
+func (p *emptyAuthProvider) IsAllowed(request *http.Request) bool {
+	return true
+}

auth/empty_test.go

@@ -0,0 +1,36 @@
+package auth
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+func Test_GIVEN_EmptyAuth_WHEN_CallingIsAllowedWithoutAuth_THEN_TrueReturned(t *testing.T) {
+	// assemble
+	request := httptest.NewRequest(http.MethodGet, "http://example.com", nil)
+	provider := NewEmptyAuthProvider()
+
+	// act
+	response := provider.IsAllowed(request)
+
+	// assert
+	if !response {
+		t.Errorf("expected request to be allowed, but failed")
+	}
+}
+
+func Test_GIVEN_EmptyAuth_WHEN_CallingIsAllowedWithAuth_THEN_TrueReturned(t *testing.T) {
+	// assemble
+	request := httptest.NewRequest(http.MethodGet, "http://example.com", nil)
+	request.SetBasicAuth("user", "pass")
+	provider := NewEmptyAuthProvider()
+
+	// act
+	response := provider.IsAllowed(request)
+
+	// assert
+	if !response {
+		t.Errorf("expected request to be allowed, but failed")
+	}
+}

auth/hash.go

@@ -5,7 +5,7 @@ import (
 	"encoding/hex"
 )
 
-func Hash(data []byte) []byte {
+func hash(data []byte) []byte {
 	if len(data) == 0 {
 		return []byte{}
 	}
@@ -14,5 +14,5 @@ func Hash(data []byte) []byte {
 }
 
 func HashString(data string) string {
-	return hex.EncodeToString(Hash([]byte(data)))
+	return hex.EncodeToString(hash([]byte(data)))
 }

auth/middleware.go

@@ -1,31 +0,0 @@
-package auth
-
-import (
-	"net/http"
-)
-
-type BasicAuthProvider interface {
-	Enabled() bool
-	DoesBasicAuthMatch(username, password string) bool
-}
-
-func BasicAuthMiddleware(handlerFunc http.HandlerFunc, basicAuthProvider BasicAuthProvider) http.HandlerFunc {
-	if basicAuthProvider.Enabled() {
-		return func(w http.ResponseWriter, r *http.Request) {
-			if doesBasicAuthMatch(r, basicAuthProvider) {
-				handlerFunc.ServeHTTP(w, r)
-			} else {
-				w.WriteHeader(http.StatusUnauthorized)
-			}
-		}
-	}
-	return handlerFunc
-}
-
-func doesBasicAuthMatch(r *http.Request, basicAuthProvider BasicAuthProvider) bool {
-	rawUsername, rawPassword, ok := r.BasicAuth()
-	if ok {
-		return basicAuthProvider.DoesBasicAuthMatch(rawUsername, rawPassword)
-	}
-	return false
-}

auth/middleware_test.go

@@ -1,58 +0,0 @@
-package auth
-
-import (
-	"net/http"
-	"net/http/httptest"
-	"testing"
-)
-
-type testAuthProvider struct {
-	enabled bool
-	match   bool
-}
-
-func (p testAuthProvider) Enabled() bool {
-	return p.enabled
-}
-
-func (p testAuthProvider) DoesBasicAuthMatch(username, password string) bool {
-	return p.match
-}
-
-func newTestRequest() *http.Request {
-	return httptest.NewRequest(http.MethodGet, "http://example.com", nil)
-}
-
-func executeBasicAuthMiddlewareTest(t *testing.T, authEnabled bool, authMatches bool, expectedCode int, expectedCallCount int) {
-	callCount := 0
-	testHandler := func(w http.ResponseWriter, r *http.Request) {
-		callCount++
-	}
-
-	handler := BasicAuthMiddleware(testHandler, testAuthProvider{enabled: authEnabled, match: authMatches})
-	recorder := httptest.NewRecorder()
-	request := newTestRequest()
-	if authEnabled {
-		request.SetBasicAuth("test", "test")
-	}
-	handler.ServeHTTP(recorder, request)
-
-	if recorder.Code != expectedCode {
-		t.Errorf("statusCode = %v, want %v", recorder.Code, expectedCode)
-	}
-	if callCount != expectedCallCount {
-		t.Errorf("callCount = %v, want %v", callCount, expectedCallCount)
-	}
-}
-
-func Test_GIVEN_DisabledBasicAuth_WHEN_MethodCalled_THEN_RequestProcessed(t *testing.T) {
-	executeBasicAuthMiddlewareTest(t, false, false, http.StatusOK, 1)
-}
-
-func Test_GIVEN_EnabledBasicAuth_WHEN_MethodCalledWithCorrectCredentials_THEN_RequestProcessed(t *testing.T) {
-	executeBasicAuthMiddlewareTest(t, true, true, http.StatusOK, 1)
-}
-
-func Test_GIVEN_EnabledBasicAuth_WHEN_MethodCalledWithIncorrectCredentials_THEN_RequestRejected(t *testing.T) {
-	executeBasicAuthMiddlewareTest(t, true, false, http.StatusUnauthorized, 0)
-}

auth/provider.go

@@ -0,0 +1,9 @@
+package auth
+
+import (
+	"net/http"
+)
+
+type AuthProvider interface {
+	IsAllowed(*http.Request) bool
+}

cfg/basicAuth.go

@@ -1,25 +0,0 @@
-package cfg
-
-import "gitlab.com/hectorjsmith/fail2ban-prometheus-exporter/auth"
-
-type hashedBasicAuth struct {
-	username string
-	password string
-}
-
-func newHashedBasicAuth(rawUsername, rawPassword string) *hashedBasicAuth {
-	return &hashedBasicAuth{
-		username: auth.HashString(rawUsername),
-		password: auth.HashString(rawPassword),
-	}
-}
-
-func (p *hashedBasicAuth) Enabled() bool {
-	return len(p.username) > 0 && len(p.password) > 0
-}
-
-func (p *hashedBasicAuth) DoesBasicAuthMatch(rawUsername, rawPassword string) bool {
-	username := auth.HashString(rawUsername)
-	password := auth.HashString(rawPassword)
-	return username == p.username && password == p.password
-}

cfg/basicAuth_test.go

@@ -1,60 +0,0 @@
-package cfg
-
-import "testing"
-
-func Test_hashedBasicAuth_DoesBasicAuthMatch(t *testing.T) {
-	type args struct {
-		username string
-		password string
-	}
-	type fields struct {
-		username string
-		password string
-	}
-	tests := []struct {
-		name   string
-		fields fields
-		args   args
-		want   bool
-	}{
-		{"Happy test #1", fields{username: "1234", password: "1234"}, args{username: "1234", password: "1234"}, true},
-		{"Happy test #2", fields{username: "test", password: "1234"}, args{username: "test", password: "1234"}, true},
-		{"Happy test #3", fields{username: "TEST", password: "1234"}, args{username: "TEST", password: "1234"}, true},
-		{"Non match #1", fields{username: "test", password: "1234"}, args{username: "1234", password: "1234"}, false},
-		{"Non match #2", fields{username: "1234", password: "test"}, args{username: "1234", password: "1234"}, false},
-		{"Non match #3", fields{username: "1234", password: "test"}, args{username: "1234", password: "TEST"}, false},
-	}
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			basicAuth := newHashedBasicAuth(tt.fields.username, tt.fields.password)
-			if got := basicAuth.DoesBasicAuthMatch(tt.args.username, tt.args.password); got != tt.want {
-				t.Errorf("DoesBasicAuthMatch() = %v, want %v", got, tt.want)
-			}
-		})
-	}
-}
-
-func Test_hashedBasicAuth_Enabled(t *testing.T) {
-	type fields struct {
-		username string
-		password string
-	}
-	tests := []struct {
-		name   string
-		fields fields
-		want   bool
-	}{
-		{"Both blank", fields{username: "", password: ""}, false},
-		{"Single blank #1", fields{username: "test", password: ""}, false},
-		{"Single blank #1", fields{username: "", password: "test"}, false},
-		{"Both populated", fields{username: "test", password: "test"}, true},
-	}
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			basicAuth := newHashedBasicAuth(tt.fields.username, tt.fields.password)
-			if got := basicAuth.Enabled(); got != tt.want {
-				t.Errorf("Enabled() = %v, want %v", got, tt.want)
-			}
-		})
-	}
-}

cfg/cfg.go

@@ -2,9 +2,11 @@ package cfg
 
 import (
 	"fmt"
+	"log"
 	"os"
 
 	"github.com/alecthomas/kong"
+	"gitlab.com/hectorjsmith/fail2ban-prometheus-exporter/auth"
 )
 
 var cliStruct struct {
@@ -36,11 +38,22 @@ func Parse() *AppSettings {
 		Fail2BanSocketPath:    cliStruct.F2bSocketPath,
 		FileCollectorPath:     cliStruct.TextFileExporterPath,
 		ExitOnSocketConnError: cliStruct.ExitOnSocketError,
-		BasicAuthProvider:     newHashedBasicAuth(cliStruct.BasicAuthUser, cliStruct.BasicAuthPass),
+		AuthProvider:          createAuthProvider(),
 	}
 	return settings
 }
 
+func createAuthProvider() auth.AuthProvider {
+	username := cliStruct.BasicAuthUser
+	password := cliStruct.BasicAuthPass
+
+	if len(username) == 0 && len(password) == 0 {
+		return auth.NewEmptyAuthProvider()
+	}
+	log.Print("basic auth enabled")
+	return auth.NewBasicAuthProvider(username, password)
+}
+
 func validateFlags(cliCtx *kong.Context) {
 	var flagsValid = true
 	var messages = []string{}

cfg/settings.go

@@ -1,10 +1,12 @@
 package cfg
 
+import "gitlab.com/hectorjsmith/fail2ban-prometheus-exporter/auth"
+
 type AppSettings struct {
 	VersionMode           bool
 	MetricsAddress        string
 	Fail2BanSocketPath    string
 	FileCollectorPath     string
-	BasicAuthProvider     *hashedBasicAuth
+	AuthProvider          auth.AuthProvider
 	ExitOnSocketConnError bool
 }

exporter.go

@@ -2,17 +2,18 @@ package main
 
 import (
 	"fmt"
-	"github.com/prometheus/client_golang/prometheus"
-	"github.com/prometheus/client_golang/prometheus/promhttp"
-	"gitlab.com/hectorjsmith/fail2ban-prometheus-exporter/auth"
-	"gitlab.com/hectorjsmith/fail2ban-prometheus-exporter/cfg"
-	"gitlab.com/hectorjsmith/fail2ban-prometheus-exporter/collector/f2b"
-	"gitlab.com/hectorjsmith/fail2ban-prometheus-exporter/collector/textfile"
 	"log"
 	"net/http"
 	"os"
 	"os/signal"
 	"syscall"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	"gitlab.com/hectorjsmith/fail2ban-prometheus-exporter/cfg"
+	"gitlab.com/hectorjsmith/fail2ban-prometheus-exporter/collector/f2b"
+	"gitlab.com/hectorjsmith/fail2ban-prometheus-exporter/collector/textfile"
+	"gitlab.com/hectorjsmith/fail2ban-prometheus-exporter/server"
 )
 
 const (
@@ -66,17 +67,14 @@ func main() {
 		textFileCollector := textfile.NewCollector(appSettings)
 		prometheus.MustRegister(textFileCollector)
 
-		http.HandleFunc("/", auth.BasicAuthMiddleware(rootHtmlHandler, appSettings.BasicAuthProvider))
-		http.HandleFunc(metricsPath, auth.BasicAuthMiddleware(
+		http.HandleFunc("/", server.BasicAuthMiddleware(rootHtmlHandler, appSettings.AuthProvider))
+		http.HandleFunc(metricsPath, server.BasicAuthMiddleware(
 			func(w http.ResponseWriter, r *http.Request) {
 				metricHandler(w, r, textFileCollector)
 			},
-			appSettings.BasicAuthProvider,
+			appSettings.AuthProvider,
 		))
 		log.Printf("metrics available at '%s'", metricsPath)
-		if appSettings.BasicAuthProvider.Enabled() {
-			log.Printf("basic auth enabled")
-		}
 
 		svrErr := make(chan error)
 		go func() {

server/middleware.go

@@ -0,0 +1,17 @@
+package server
+
+import (
+	"net/http"
+
+	"gitlab.com/hectorjsmith/fail2ban-prometheus-exporter/auth"
+)
+
+func BasicAuthMiddleware(handlerFunc http.HandlerFunc, authProvider auth.AuthProvider) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		if authProvider.IsAllowed(r) {
+			handlerFunc.ServeHTTP(w, r)
+		} else {
+			w.WriteHeader(http.StatusUnauthorized)
+		}
+	}
+}

server/middleware_test.go

@@ -0,0 +1,46 @@
+package server
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+type testAuthProvider struct {
+	match bool
+}
+
+func (p testAuthProvider) IsAllowed(request *http.Request) bool {
+	return p.match
+}
+
+func newTestRequest() *http.Request {
+	return httptest.NewRequest(http.MethodGet, "http://example.com", nil)
+}
+
+func executeBasicAuthMiddlewareTest(t *testing.T, authMatches bool, expectedCode int, expectedCallCount int) {
+	callCount := 0
+	testHandler := func(w http.ResponseWriter, r *http.Request) {
+		callCount++
+	}
+
+	handler := BasicAuthMiddleware(testHandler, testAuthProvider{match: authMatches})
+	recorder := httptest.NewRecorder()
+	request := newTestRequest()
+	handler.ServeHTTP(recorder, request)
+
+	if recorder.Code != expectedCode {
+		t.Errorf("statusCode = %v, want %v", recorder.Code, expectedCode)
+	}
+	if callCount != expectedCallCount {
+		t.Errorf("callCount = %v, want %v", callCount, expectedCallCount)
+	}
+}
+
+func Test_GIVEN_MatchingBasicAuth_WHEN_MethodCalled_THEN_RequestProcessed(t *testing.T) {
+	executeBasicAuthMiddlewareTest(t, true, http.StatusOK, 1)
+}
+
+func Test_GIVEN_NonMatchingBasicAuth_WHEN_MethodCalled_THEN_RequestRejected(t *testing.T) {
+	executeBasicAuthMiddlewareTest(t, false, http.StatusUnauthorized, 0)
+}