confighttp: Ensure that auth errors use provided error handler (#12714)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description
OTLP/HTTP receiver does not encode authentication errors into a `Status`
object, and as such not expose a developer facing error message in the
`Status.mesage` field. -
https://opentelemetry.io/docs/specs/otlp/#failures-1

Resolves this issue by handling authentication errors with the same
error handler provided to the Server.

<!-- Issue number if applicable -->
#### Link to tracking issue
Fixes
#12666
<!--Describe what testing was performed and which tests were added.-->
#### Testing
Unit tests for handling errors with and without a server error handler
<!--Please delete paragraphs that you did not use before submitting.-->

---------

Co-authored-by: Pablo Baeyens <[email protected]>

Author: noctchillin

.chloggen/fix-confighttp-auth-error.yaml

@@ -0,0 +1,25 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: bug_fix
+
+# The name of the component, or a single word describing the area of concern, (e.g. otlpreceiver)
+component: confighttp
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: "Ensure http authentication server failures are handled by the provided error handler"
+
+# One or more tracking issues or pull requests related to the change
+issues: [12666]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [user]

config/confighttp/confighttp.go

@@ -441,7 +441,7 @@ func (hss *ServerConfig) ToServer(_ context.Context, host component.Host, settin
 			return nil, err
 		}
 
-		handler = authInterceptor(handler, server, hss.Auth.RequestParameters)
+		handler = authInterceptor(handler, server, hss.Auth.RequestParameters, serverOpts)
 	}
 
 	if hss.CORS != nil && len(hss.CORS.AllowedOrigins) > 0 {
@@ -537,7 +537,7 @@ func NewDefaultCORSConfig() *CORSConfig {
 	return &CORSConfig{}
 }
 
-func authInterceptor(next http.Handler, server extensionauth.Server, requestParams []string) http.Handler {
+func authInterceptor(next http.Handler, server extensionauth.Server, requestParams []string, serverOpts *internal.ToServerOptions) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		sources := r.Header
 		query := r.URL.Query()
@@ -548,7 +548,12 @@ func authInterceptor(next http.Handler, server extensionauth.Server, requestPara
 		}
 		ctx, err := server.Authenticate(r.Context(), sources)
 		if err != nil {
-			http.Error(w, http.StatusText(http.StatusUnauthorized), http.StatusUnauthorized)
+			if serverOpts.ErrHandler != nil {
+				serverOpts.ErrHandler(w, r, err.Error(), http.StatusUnauthorized)
+			} else {
+				http.Error(w, err.Error(), http.StatusUnauthorized)
+			}
+
 			return
 		}
 

config/confighttp/confighttp_test.go

@@ -1212,7 +1212,7 @@ func TestFailedServerAuth(t *testing.T) {
 	host := &mockHost{
 		ext: map[component.ID]component.Component{
 			mockID: newMockAuthServer(func(ctx context.Context, _ map[string][]string) (context.Context, error) {
-				return ctx, errors.New("Settings failed")
+				return ctx, errors.New("invalid authorization")
 			}),
 		},
 	}
@@ -1229,6 +1229,44 @@ func TestFailedServerAuth(t *testing.T) {
 	assert.Equal(t, fmt.Sprintf("%v %s", http.StatusUnauthorized, http.StatusText(http.StatusUnauthorized)), response.Result().Status)
 }
 
+func TestFailedServerAuthWithErrorHandler(t *testing.T) {
+	// prepare
+	hss := ServerConfig{
+		Endpoint: "localhost:0",
+		Auth: &AuthConfig{
+			Authentication: configauth.Authentication{
+				AuthenticatorID: mockID,
+			},
+		},
+	}
+	host := &mockHost{
+		ext: map[component.ID]component.Component{
+			mockID: newMockAuthServer(func(ctx context.Context, _ map[string][]string) (context.Context, error) {
+				return ctx, errors.New("invalid authorization")
+			}),
+		},
+	}
+
+	eh := func(w http.ResponseWriter, _ *http.Request, err string, statusCode int) {
+		assert.Equal(t, http.StatusUnauthorized, statusCode)
+		// custom error handler uses real error string
+		assert.Equal(t, "invalid authorization", err)
+		// custom error handler changes returned status code
+		http.Error(w, err, http.StatusInternalServerError)
+	}
+
+	srv, err := hss.ToServer(context.Background(), host, componenttest.NewNopTelemetrySettings(), http.HandlerFunc(func(http.ResponseWriter, *http.Request) {}), WithErrorHandler(eh))
+	require.NoError(t, err)
+
+	// tt
+	response := &httptest.ResponseRecorder{}
+	srv.Handler.ServeHTTP(response, httptest.NewRequest(http.MethodGet, "/", nil))
+
+	// verify
+	assert.Equal(t, http.StatusInternalServerError, response.Result().StatusCode)
+	assert.Equal(t, fmt.Sprintf("%v %s", http.StatusInternalServerError, http.StatusText(http.StatusInternalServerError)), response.Result().Status)
+}
+
 func TestServerWithErrorHandler(t *testing.T) {
 	// prepare
 	hss := ServerConfig{