Add CORS tests

Author: code-asher

Diff for: api/api.go

@@ -7,7 +7,6 @@ import (
 
 	"github.com/go-chi/chi/v5"
 	"github.com/go-chi/chi/v5/middleware"
-	"github.com/go-chi/cors"
 
 	"cdr.dev/slog"
 	"github.com/coder/code-marketplace/api/httpapi"
@@ -74,16 +73,8 @@ func New(options *Options) *API {
 
 	r := chi.NewRouter()
 
-	cors := cors.New(cors.Options{
-		AllowedOrigins:   []string{"*"},
-		AllowedMethods:   []string{"POST", "GET", "OPTIONS"},
-		AllowedHeaders:   []string{"*"},
-		AllowCredentials: true,
-		MaxAge:           300,
-	})
-
 	r.Use(
-		cors.Handler,
+		httpmw.Cors(),
 		httpmw.RateLimitPerMinute(options.RateLimit),
 		middleware.GetHead,
 		httpmw.AttachRequestID,

Diff for: api/httpmw/cors.go

@@ -0,0 +1,38 @@
+package httpmw
+
+import (
+	"net/http"
+
+	"github.com/go-chi/cors"
+)
+
+const (
+	// Server headers.
+	AccessControlAllowOriginHeader      = "Access-Control-Allow-Origin"
+	AccessControlAllowCredentialsHeader = "Access-Control-Allow-Credentials"
+	AccessControlAllowMethodsHeader     = "Access-Control-Allow-Methods"
+	AccessControlAllowHeadersHeader     = "Access-Control-Allow-Headers"
+	VaryHeader                          = "Vary"
+
+	// Client headers.
+	OriginHeader                      = "Origin"
+	AccessControlRequestMethodHeader  = "Access-Control-Request-Method"
+	AccessControlRequestHeadersHeader = "Access-Control-Request-Headers"
+)
+
+func Cors() func(next http.Handler) http.Handler {
+	return cors.Handler(cors.Options{
+		AllowedOrigins: []string{"*"},
+		AllowedMethods: []string{
+			http.MethodHead,
+			http.MethodGet,
+			http.MethodPost,
+			http.MethodPut,
+			http.MethodPatch,
+			http.MethodDelete,
+		},
+		AllowedHeaders:   []string{"*"},
+		AllowCredentials: true,
+		MaxAge:           300,
+	})
+}

Diff for: api/httpmw/cors_test.go

@@ -0,0 +1,123 @@
+package httpmw_test
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/coder/code-marketplace/api/httpmw"
+)
+
+func TestCors(t *testing.T) {
+	t.Parallel()
+
+	methods := []string{
+		http.MethodOptions,
+		http.MethodHead,
+		http.MethodGet,
+		http.MethodPost,
+		http.MethodPut,
+		http.MethodPatch,
+		http.MethodDelete,
+	}
+
+	tests := []struct {
+		name           string
+		origin         string
+		allowedOrigin  string
+		headers        string
+		allowedHeaders string
+	}{
+		{
+			name:          "LocalHTTP",
+			origin:        "http://localhost:3000",
+			allowedOrigin: "*",
+		},
+		{
+			name:          "LocalHTTPS",
+			origin:        "https://localhost:3000",
+			allowedOrigin: "*",
+		},
+		{
+			name:          "HTTP",
+			origin:        "http://code-server.domain.tld",
+			allowedOrigin: "*",
+		},
+		{
+			name:          "HTTPS",
+			origin:        "https://code-server.domain.tld",
+			allowedOrigin: "*",
+		},
+		{
+			// VS Code appears to use this origin.
+			name:          "VSCode",
+			origin:        "vscode-file://vscode-app",
+			allowedOrigin: "*",
+		},
+		{
+			name:          "NoOrigin",
+			allowedOrigin: "",
+		},
+		{
+			name:           "Headers",
+			origin:         "foobar",
+			allowedOrigin:  "*",
+			headers:        "X-TEST,X-TEST2",
+			allowedHeaders: "X-Test, X-Test2",
+		},
+	}
+
+	for _, test := range tests {
+		test := test
+		t.Run(test.name, func(t *testing.T) {
+			t.Parallel()
+
+			for _, method := range methods {
+				method := method
+				t.Run(method, func(t *testing.T) {
+					t.Parallel()
+
+					r := httptest.NewRequest(method, "http://dev.coder.com", nil)
+					if test.origin != "" {
+						r.Header.Set(httpmw.OriginHeader, test.origin)
+					}
+
+					// OPTIONS requests need to know what method will be requested, or
+					// go-chi/cors will error.  Both request headers and methods should be
+					// ignored for regular requests even if they are set, although that is
+					// not tested here.
+					if method == http.MethodOptions {
+						r.Header.Set(httpmw.AccessControlRequestMethodHeader, http.MethodGet)
+						if test.headers != "" {
+							r.Header.Set(httpmw.AccessControlRequestHeadersHeader, test.headers)
+						}
+					}
+
+					rw := httptest.NewRecorder()
+					handler := httpmw.Cors()(http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
+						rw.WriteHeader(http.StatusNoContent)
+					}))
+					handler.ServeHTTP(rw, r)
+
+					// Should always set some kind of allowed origin, if allowed.
+					require.Equal(t, test.allowedOrigin, rw.Header().Get(httpmw.AccessControlAllowOriginHeader))
+
+					// OPTIONS should echo back the request method and headers and we
+					// should never get to our handler as the middleware short-circuits
+					// with a 200.
+					if method == http.MethodOptions {
+						require.Equal(t, http.MethodGet, rw.Header().Get(httpmw.AccessControlAllowMethodsHeader))
+						require.Equal(t, test.allowedHeaders, rw.Header().Get(httpmw.AccessControlAllowHeadersHeader))
+						require.Equal(t, http.StatusOK, rw.Code)
+					} else {
+						require.Equal(t, "", rw.Header().Get(httpmw.AccessControlAllowMethodsHeader))
+						require.Equal(t, "", rw.Header().Get(httpmw.AccessControlAllowHeadersHeader))
+						require.Equal(t, http.StatusNoContent, rw.Code)
+					}
+				})
+			}
+		})
+	}
+}