fix: explicitly cache images to prevent unexpected behavior

backend/internal/controller/app_config_controller.go

@@ -3,6 +3,7 @@ package controller
 import (
 	"net/http"
 	"strconv"
+	"time"
 
 	"github.com/gin-gonic/gin"
 	"github.com/pocket-id/pocket-id/backend/internal/common"
@@ -247,6 +248,8 @@ func (acc *AppConfigController) getImage(c *gin.Context, name string, imageType
 	mimeType := utils.GetImageMimeType(imageType)
 
 	c.Header("Content-Type", mimeType)
+
+	utils.SetCacheControlHeader(c, 15*time.Minute, 24*time.Hour)
 	c.File(imagePath)
 }
 

backend/internal/controller/oidc_controller.go

@@ -6,6 +6,7 @@ import (
 	"net/http"
 	"net/url"
 	"strings"
+	"time"
 
 	"github.com/gin-gonic/gin"
 
@@ -545,6 +546,8 @@ func (oc *OidcController) getClientLogoHandler(c *gin.Context) {
 		return
 	}
 
+	utils.SetCacheControlHeader(c, 15*time.Minute, 12*time.Hour)
+
 	c.Header("Content-Type", mimeType)
 	c.File(imagePath)
 }

backend/internal/controller/user_controller.go

@@ -250,10 +250,7 @@ func (uc *UserController) getUserProfilePictureHandler(c *gin.Context) {
 		defer picture.Close()
 	}
 
-	_, ok := c.GetQuery("skipCache")
-	if !ok {
-		c.Header("Cache-Control", "public, max-age=900")
-	}
+	utils.SetCacheControlHeader(c, 15*time.Minute, 1*time.Hour)
 
 	c.DataFromReader(http.StatusOK, size, "image/png", picture, nil)
 }

backend/internal/utils/http_util.go

@@ -1,8 +1,11 @@
 package utils
 
 import (
+	"github.com/gin-gonic/gin"
 	"net/http"
+	"strconv"
 	"strings"
+	"time"
 )
 
 // BearerAuth returns the value of the bearer token in the Authorization header if present
@@ -16,3 +19,14 @@ func BearerAuth(r *http.Request) (string, bool) {
 
 	return "", false
 }
+
+// SetCacheControlHeader sets the Cache-Control header for the response.
+func SetCacheControlHeader(ctx *gin.Context, maxAge, staleWhileRevalidate time.Duration) {
+	_, ok := ctx.GetQuery("skipCache")
+	if !ok {
+		maxAgeSeconds := strconv.Itoa(int(maxAge.Seconds()))
+		staleWhileRevalidateSeconds := strconv.Itoa(int(staleWhileRevalidate.Seconds()))
+		ctx.Header("Cache-Control", "public, max-age="+maxAgeSeconds+", stale-while-revalidate="+staleWhileRevalidateSeconds)
+	}
+
+}