feat: add x-tinyauth-location to nginx response

Solves #773. Normally you let Nginx handle the login URL creation but with this "hack"
we can set an arbitary header with where Tinyauth wants the user to go to. Later the
Nginx error page can get this header and redirect accordingly.

internal/controller/proxy_controller.go

@@ -131,14 +131,6 @@ func (controller *ProxyController) proxyHandler(c *gin.Context) {
 	}
 
 	if !controller.auth.CheckIP(acls.IP, clientIP) {
-		if !controller.useBrowserResponse(proxyCtx) {
-			c.JSON(401, gin.H{
-				"status":  401,
-				"message": "Unauthorized",
-			})
-			return
-		}
-
 		queries, err := query.Values(config.UnauthorizedQuery{
 			Resource: strings.Split(proxyCtx.Host, ".")[0],
 			IP:       clientIP,
@@ -146,11 +138,22 @@ func (controller *ProxyController) proxyHandler(c *gin.Context) {
 
 		if err != nil {
 			tlog.App.Error().Err(err).Msg("Failed to encode unauthorized query")
-			c.Redirect(http.StatusTemporaryRedirect, fmt.Sprintf("%s/error", controller.config.AppURL))
+			controller.handleError(c, proxyCtx)
 			return
 		}
 
-		c.Redirect(http.StatusTemporaryRedirect, fmt.Sprintf("%s/unauthorized?%s", controller.config.AppURL, queries.Encode()))
+		redirectURL := fmt.Sprintf("%s/unauthorized?%s", controller.config.AppURL, queries.Encode())
+
+		if !controller.useBrowserResponse(proxyCtx) {
+			c.Header("x-tinyauth-location", redirectURL)
+			c.JSON(401, gin.H{
+				"status":  401,
+				"message": "Unauthorized",
+			})
+			return
+		}
+
+		c.Redirect(http.StatusTemporaryRedirect, redirectURL)
 		return
 	}
 
@@ -175,21 +178,13 @@ func (controller *ProxyController) proxyHandler(c *gin.Context) {
 		if !userAllowed {
 			tlog.App.Warn().Str("user", userContext.Username).Str("resource", strings.Split(proxyCtx.Host, ".")[0]).Msg("User not allowed to access resource")
 
-			if !controller.useBrowserResponse(proxyCtx) {
-				c.JSON(403, gin.H{
-					"status":  403,
-					"message": "Forbidden",
-				})
-				return
-			}
-
 			queries, err := query.Values(config.UnauthorizedQuery{
 				Resource: strings.Split(proxyCtx.Host, ".")[0],
 			})
 
 			if err != nil {
 				tlog.App.Error().Err(err).Msg("Failed to encode unauthorized query")
-				c.Redirect(http.StatusTemporaryRedirect, fmt.Sprintf("%s/error", controller.config.AppURL))
+				controller.handleError(c, proxyCtx)
 				return
 			}
 
@@ -199,7 +194,18 @@ func (controller *ProxyController) proxyHandler(c *gin.Context) {
 				queries.Set("username", userContext.Username)
 			}
 
-			c.Redirect(http.StatusTemporaryRedirect, fmt.Sprintf("%s/unauthorized?%s", controller.config.AppURL, queries.Encode()))
+			redirectURL := fmt.Sprintf("%s/unauthorized?%s", controller.config.AppURL, queries.Encode())
+
+			if !controller.useBrowserResponse(proxyCtx) {
+				c.Header("x-tinyauth-location", redirectURL)
+				c.JSON(403, gin.H{
+					"status":  403,
+					"message": "Forbidden",
+				})
+				return
+			}
+
+			c.Redirect(http.StatusTemporaryRedirect, redirectURL)
 			return
 		}
 
@@ -215,14 +221,6 @@ func (controller *ProxyController) proxyHandler(c *gin.Context) {
 			if !groupOK {
 				tlog.App.Warn().Str("user", userContext.Username).Str("resource", strings.Split(proxyCtx.Host, ".")[0]).Msg("User groups do not match resource requirements")
 
-				if !controller.useBrowserResponse(proxyCtx) {
-					c.JSON(403, gin.H{
-						"status":  403,
-						"message": "Forbidden",
-					})
-					return
-				}
-
 				queries, err := query.Values(config.UnauthorizedQuery{
 					Resource: strings.Split(proxyCtx.Host, ".")[0],
 					GroupErr: true,
@@ -230,7 +228,7 @@ func (controller *ProxyController) proxyHandler(c *gin.Context) {
 
 				if err != nil {
 					tlog.App.Error().Err(err).Msg("Failed to encode unauthorized query")
-					c.Redirect(http.StatusTemporaryRedirect, fmt.Sprintf("%s/error", controller.config.AppURL))
+					controller.handleError(c, proxyCtx)
 					return
 				}
 
@@ -240,7 +238,18 @@ func (controller *ProxyController) proxyHandler(c *gin.Context) {
 					queries.Set("username", userContext.Username)
 				}
 
-				c.Redirect(http.StatusTemporaryRedirect, fmt.Sprintf("%s/unauthorized?%s", controller.config.AppURL, queries.Encode()))
+				redirectURL := fmt.Sprintf("%s/unauthorized?%s", controller.config.AppURL, queries.Encode())
+
+				if !controller.useBrowserResponse(proxyCtx) {
+					c.Header("x-tinyauth-location", redirectURL)
+					c.JSON(403, gin.H{
+						"status":  403,
+						"message": "Forbidden",
+					})
+					return
+				}
+
+				c.Redirect(http.StatusTemporaryRedirect, redirectURL)
 				return
 			}
 		}
@@ -266,7 +275,20 @@ func (controller *ProxyController) proxyHandler(c *gin.Context) {
 		return
 	}
 
+	queries, err := query.Values(config.RedirectQuery{
+		RedirectURI: fmt.Sprintf("%s://%s%s", proxyCtx.Proto, proxyCtx.Host, proxyCtx.Path),
+	})
+
+	if err != nil {
+		tlog.App.Error().Err(err).Msg("Failed to encode redirect URI query")
+		controller.handleError(c, proxyCtx)
+		return
+	}
+
+	redirectURL := fmt.Sprintf("%s/login?%s", controller.config.AppURL, queries.Encode())
+
 	if !controller.useBrowserResponse(proxyCtx) {
+		c.Header("x-tinyauth-location", redirectURL)
 		c.JSON(401, gin.H{
 			"status":  401,
 			"message": "Unauthorized",
@@ -274,17 +296,7 @@ func (controller *ProxyController) proxyHandler(c *gin.Context) {
 		return
 	}
 
-	queries, err := query.Values(config.RedirectQuery{
+	c.Redirect(http.StatusTemporaryRedirect, redirectURL)
-		RedirectURI: fmt.Sprintf("%s://%s%s", proxyCtx.Proto, proxyCtx.Host, proxyCtx.Path),
-	})
-
-	if err != nil {
-		tlog.App.Error().Err(err).Msg("Failed to encode redirect URI query")
-		c.Redirect(http.StatusTemporaryRedirect, fmt.Sprintf("%s/error", controller.config.AppURL))
-		return
-	}
-
-	c.Redirect(http.StatusTemporaryRedirect, fmt.Sprintf("%s/login?%s", controller.config.AppURL, queries.Encode()))
 }
 
 func (controller *ProxyController) setHeaders(c *gin.Context, acls config.App) {
@@ -306,7 +318,10 @@ func (controller *ProxyController) setHeaders(c *gin.Context, acls config.App) {
 }
 
 func (controller *ProxyController) handleError(c *gin.Context, proxyCtx ProxyContext) {
+	redirectURL := fmt.Sprintf("%s/error", controller.config.AppURL)
+
 	if !controller.useBrowserResponse(proxyCtx) {
+		c.Header("x-tinyauth-location", redirectURL)
 		c.JSON(500, gin.H{
 			"status":  500,
 			"message": "Internal Server Error",
@@ -314,7 +329,7 @@ func (controller *ProxyController) handleError(c *gin.Context, proxyCtx ProxyCon
 		return
 	}
 
-	c.Redirect(http.StatusTemporaryRedirect, fmt.Sprintf("%s/error", controller.config.AppURL))
+	c.Redirect(http.StatusTemporaryRedirect, redirectURL)
 }
 
 func (controller *ProxyController) getHeader(c *gin.Context, header string) (string, bool) {

internal/controller/proxy_controller_test.go

@@ -116,8 +116,7 @@ func TestProxyController(t *testing.T) {
 
 				assert.Equal(t, 307, recorder.Code)
 				location := recorder.Header().Get("Location")
-				assert.Contains(t, location, "https://tinyauth.example.com/login?redirect_uri=")
+				assert.Equal(t, location, "https://tinyauth.example.com/login?redirect_uri=https%3A%2F%2Ftest.example.com%2F")
-				assert.Contains(t, location, "https%3A%2F%2Ftest.example.com%2F")
 			},
 		},
 		{
@@ -129,6 +128,8 @@ func TestProxyController(t *testing.T) {
 				req.Header.Set("user-agent", browserUserAgent)
 				router.ServeHTTP(recorder, req)
 				assert.Equal(t, 401, recorder.Code)
+				location := recorder.Header().Get("x-tinyauth-location")
+				assert.Equal(t, location, "https://tinyauth.example.com/login?redirect_uri=https%3A%2F%2Ftest.example.com%2F")
 			},
 		},
 		{
@@ -142,8 +143,7 @@ func TestProxyController(t *testing.T) {
 				router.ServeHTTP(recorder, req)
 				assert.Equal(t, 307, recorder.Code)
 				location := recorder.Header().Get("Location")
-				assert.Contains(t, location, "https://tinyauth.example.com/login?redirect_uri=")
+				assert.Equal(t, location, "https://tinyauth.example.com/login?redirect_uri=https%3A%2F%2Ftest.example.com%2Fhello")
-				assert.Contains(t, location, "https%3A%2F%2Ftest.example.com%2Fhello")
 			},
 		},
 		{
@@ -159,8 +159,7 @@ func TestProxyController(t *testing.T) {
 
 				assert.Equal(t, 307, recorder.Code)
 				location := recorder.Header().Get("Location")
-				assert.Contains(t, location, "https://tinyauth.example.com/login?redirect_uri=")
+				assert.Equal(t, location, "https://tinyauth.example.com/login?redirect_uri=https%3A%2F%2Ftest.example.com%2F")
-				assert.Contains(t, location, "https%3A%2F%2Ftest.example.com%2F")
 			},
 		},
 		{
@@ -174,6 +173,8 @@ func TestProxyController(t *testing.T) {
 				req.Header.Set("user-agent", browserUserAgent)
 				router.ServeHTTP(recorder, req)
 				assert.Equal(t, 401, recorder.Code)
+				location := recorder.Header().Get("x-tinyauth-location")
+				assert.Equal(t, location, "https://tinyauth.example.com/login?redirect_uri=https%3A%2F%2Ftest.example.com%2F")
 			},
 		},
 		{
@@ -189,8 +190,7 @@ func TestProxyController(t *testing.T) {
 				router.ServeHTTP(recorder, req)
 				assert.Equal(t, 307, recorder.Code)
 				location := recorder.Header().Get("Location")
-				assert.Contains(t, location, "https://tinyauth.example.com/login?redirect_uri=")
+				assert.Equal(t, location, "https://tinyauth.example.com/login?redirect_uri=https%3A%2F%2Ftest.example.com%2Fhello")
-				assert.Contains(t, location, "https%3A%2F%2Ftest.example.com%2Fhello")
 			},
 		},
 		{