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
+}