Add resize validation logic to prevent image upscaling.

handler/remote.go

@@ -113,14 +113,14 @@ func fetchRemoteImg(url string, subdir string) (metaContent config.MetaFile) {
 			// remote file has changed
 			log.Info("Remote file changed, updating metadata and fetching image source...")
 			helper.DeleteMetadata(url, subdir)
-			helper.WriteMetadata(url, etag, subdir)
+			metadata = helper.WriteMetadata(url, etag, subdir)
 		} else {
 			// local file not exists
 			log.Info("Remote file not found in remote-raw, re-fetching...")
 		}
 		_ = downloadFile(localRawImagePath, url)
 		// Update metadata with newly downloaded file
-		helper.WriteMetadata(url, etag, subdir)
+		metadata = helper.WriteMetadata(url, etag, subdir)
 	}
 	return metadata
 }

handler/router.go

@@ -136,10 +136,12 @@ func Convert(c *fiber.Ctx) error {
 		// this is proxyMode, we'll have to use this url to download and save it to local path, which also gives us rawImageAbs
 		// https://test.webp.sh/mypic/123.jpg?someother=200&somebugs=200
 
+		helper.SetMetedataProxyMode(true)
 		metadata = fetchRemoteImg(realRemoteAddr, targetHostName)
 		rawImageAbs = path.Join(config.Config.RemoteRawPath, targetHostName, metadata.Id) + path.Ext(realRemoteAddr)
 	} else {
 		// not proxyMode, we'll use local path
+		helper.SetMetedataProxyMode(false)
 		metadata = helper.ReadMetadata(reqURIwithQuery, "", targetHostName)
 		if !mapMode {
 			// by default images are hosted in ImgPath
@@ -150,7 +152,7 @@ func Convert(c *fiber.Ctx) error {
 		// detect if source file has changed
 		if metadata.Checksum != helper.HashFile(rawImageAbs) {
 			log.Info("Source file has changed, re-encoding...")
-			helper.WriteMetadata(reqURIwithQuery, "", targetHostName)
+			metadata = helper.WriteMetadata(reqURIwithQuery, "", targetHostName)
 			cleanProxyCache(path.Join(config.Config.ExhaustPath, targetHostName, metadata.Id))
 		}
 	}
@@ -168,6 +170,15 @@ func Convert(c *fiber.Ctx) error {
 		})
 	}
 
+	if config.Config.EnableExtraParams && helper.HasResizeParams(extraParams) {
+		if err := helper.ValidateNoUpscale(metadata.ImageMeta, extraParams); err != nil {
+			log.Warnf("Blocked resize request for %s: %v", reqURIwithQuery, err)
+			c.Status(http.StatusBadRequest)
+			_ = c.SendString(err.Error())
+			return nil
+		}
+	}
+
 	supportedFormats := helper.GuessSupportedFormat(reqHeader)
 	// resize itself and return if only raw(jpg,jpeg,png,gif) is supported
 	if supportedFormats["jpg"] == true &&

helper/helper.go

@@ -1,6 +1,7 @@
 package helper
 
 import (
+	"errors"
 	"fmt"
 	"os"
 	"path"
@@ -25,6 +26,7 @@ import (
 var (
 	boolFalse   vips.BoolParameter
 	intMinusOne vips.IntParameter
+	ErrUpscaleNotAllowed = errors.New("requested resize exceeds source dimensions")
 )
 
 var _ = filetype.AddMatcher(filetype.NewType("svg", "image/svg+xml"), svgMatcher)
@@ -229,3 +231,23 @@ func HashFile(filepath string) string {
 	buf, _ := os.ReadFile(filepath)
 	return fmt.Sprintf("%x", xxhash.Sum64(buf))
 }
+
+func HasResizeParams(extra config.ExtraParams) bool {
+	return extra.Width > 0 || extra.Height > 0 || extra.MaxWidth > 0 || extra.MaxHeight > 0
+}
+
+func ValidateNoUpscale(meta config.ImageMeta, extra config.ExtraParams) error {
+	if !HasResizeParams(extra) || meta.Width == 0 || meta.Height == 0 {
+		return nil
+	}
+
+	if extra.Width > 0 && extra.Width > meta.Width {
+		return fmt.Errorf("%w: requested width %d exceeds source width %d", ErrUpscaleNotAllowed, extra.Width, meta.Width)
+	}
+
+	if extra.Height > 0 && extra.Height > meta.Height {
+		return fmt.Errorf("%w: requested height %d exceeds source height %d", ErrUpscaleNotAllowed, extra.Height, meta.Height)
+	}
+
+	return nil
+}

helper/helper_test.go

@@ -164,3 +164,79 @@ func TestGuessSupportedFormat(t *testing.T) {
 		})
 	}
 }
+
+func TestHasResizeParams(t *testing.T) {
+	if HasResizeParams(config.ExtraParams{}) {
+		t.Fatalf("expected empty params to report no resize request")
+	}
+
+	params := config.ExtraParams{Width: 100}
+	if !HasResizeParams(params) {
+		t.Fatalf("expected Width to trigger resize detection")
+	}
+
+	params = config.ExtraParams{MaxHeight: 80}
+	if !HasResizeParams(params) {
+		t.Fatalf("expected MaxHeight to trigger resize detection")
+	}
+}
+
+func TestValidateNoUpscale(t *testing.T) {
+	meta := config.ImageMeta{Width: 200, Height: 100}
+
+	tests := []struct {
+		params    config.ExtraParams
+		wantError bool
+	}{
+		// Tests for no resize params 
+		{
+			params:    config.ExtraParams{},
+			wantError: false,
+		},
+		// Tests for shrink Width only
+		{
+			params:    config.ExtraParams{Width: 150},
+			wantError: false,
+		},
+		// Tests for shrink Height only
+		{
+			params:    config.ExtraParams{Height: 80},
+			wantError: false,
+		},
+		// Tests for shrink both Width and Height
+		{
+			params:    config.ExtraParams{Width: 150, Height: 80},
+			wantError: false,
+		},
+		// Tests for upscale Width only
+		{
+			params:    config.ExtraParams{Width: 250},
+			wantError: true,
+		},
+		// Tests for upscale Height only
+		{
+			params:    config.ExtraParams{Height: 150},
+			wantError: true,
+		},
+		// Tests for upscale both Width and Height
+		{
+			params:    config.ExtraParams{Width: 300, Height: 200},
+			wantError: true,
+		},
+		// Tests for MaxWidth and MaxHeight 
+		{
+			params:    config.ExtraParams{MaxWidth: 300, MaxHeight: 400},
+			wantError: false,
+		},
+	}
+
+	for _, tc := range tests {
+		err := ValidateNoUpscale(meta, tc.params)
+		if tc.wantError && err == nil {
+			t.Fatalf("TestValidateNoUpscale failed with error %s", err)
+		}
+		if !tc.wantError && err != nil {
+			t.Fatalf("TestValidateNoUpscale failed with error %s", err)
+		}
+	}
+}

helper/metadata.go

@@ -12,10 +12,14 @@ import (
 	log "github.com/sirupsen/logrus"
 )
 
+var (
+	ProxyMode = false
+)
 // Get ID and filepath
 // For ProxyMode, pass in p the remote-raw path
+
 func getId(p string, subdir string) (id string, filePath string, santizedPath string) {
-	if config.ProxyMode {
+	if ProxyMode {
 		fileID := HashString(p)
 		return fileID, path.Join(config.Config.RemoteRawPath, subdir, fileID) + path.Ext(p), ""
 	}
@@ -71,7 +75,9 @@ func WriteMetadata(p, etag string, subdir string) config.MetaFile {
 	}
 
 	// Only get image metadata if the file has image extension
-	if CheckImageExtension(filepath) {
+	// extract path from URL
+	parsedURL, _ := url.Parse(filepath)
+	if CheckImageExtension(parsedURL.Path) {
 		imageMeta := getImageMeta(filepath)
 		data.ImageMeta = imageMeta
 	}
@@ -179,3 +185,7 @@ func DeleteMetadata(p string, subdir string) {
 		log.Warnln("failed to delete metadata", err)
 	}
 }
+
+func SetMetedataProxyMode(proxy bool) {
+	ProxyMode = proxy
+}

helper/metadata_test.go

@@ -12,7 +12,7 @@ func TestGetId(t *testing.T) {
 
 	t.Run("proxy mode", func(t *testing.T) {
 		// Test case 1: Proxy mode
-		config.ProxyMode = true
+		SetMetedataProxyMode(true)
 		id, jointPath, santizedPath := getId(p, "")
 
 		// Verify the return values
@@ -26,7 +26,7 @@ func TestGetId(t *testing.T) {
 	})
 	t.Run("non-proxy mode", func(t *testing.T) {
 		// Test case 2: Non-proxy mode
-		config.ProxyMode = false
+		SetMetedataProxyMode(false)
 		p = "/image.jpg?width=400&height=500"
 		id, jointPath, santizedPath := getId(p, "")