Add attachment option for Content-Disposition header (#887)

* Add attachment option for Content-Disposition header

Signed-off-by: Valentin Kiselev <mrexox@evilmartians.com>

* Add documentation to attachment option

Signed-off-by: Valentin Kiselev <mrexox@evilmartians.com>

* Add default attachment option value

Signed-off-by: Valentin Kiselev <mrexox@evilmartians.com>

* fix: Add default value to docs

Signed-off-by: Valentin Kiselev <mrexox@evilmartians.com>

* fix: Rename option attachment to return_attachment, add ENV-configuration

Signed-off-by: Valentin Kiselev <mrexox@evilmartians.com>

config/config.go

@@ -51,6 +51,7 @@ var (
 	StripColorProfile     bool
 	AutoRotate            bool
 	EnforceThumbnail      bool
+	ReturnAttachment      bool
 
 	EnableWebpDetection bool
 	EnforceWebp         bool
@@ -208,6 +209,7 @@ func Reset() {
 	StripColorProfile = true
 	AutoRotate = true
 	EnforceThumbnail = false
+	ReturnAttachment = false
 
 	EnableWebpDetection = false
 	EnforceWebp = false
@@ -356,6 +358,7 @@ func Configure() error {
 	configurators.Bool(&StripColorProfile, "IMGPROXY_STRIP_COLOR_PROFILE")
 	configurators.Bool(&AutoRotate, "IMGPROXY_AUTO_ROTATE")
 	configurators.Bool(&EnforceThumbnail, "IMGPROXY_ENFORCE_THUMBNAIL")
+	configurators.Bool(&ReturnAttachment, "IMGPROXY_RETURN_ATTACHMENT")
 
 	configurators.Bool(&EnableWebpDetection, "IMGPROXY_ENABLE_WEBP_DETECTION")
 	configurators.Bool(&EnforceWebp, "IMGPROXY_ENFORCE_WEBP")

docs/configuration.md

@@ -421,5 +421,6 @@ imgproxy can send logs to syslog, but this feature is disabled by default. To en
 * `IMGPROXY_STRIP_COLOR_PROFILE`: when `true`, imgproxy will transform the embedded color profile (ICC) to sRGB and remove it from the image. Otherwise, imgproxy will try to keep it as is. Default: `true`
 * `IMGPROXY_AUTO_ROTATE`: when `true`, imgproxy will automatically rotate images based on the EXIF Orientation parameter (if available in the image meta data). The orientation tag will be removed from the image in all cases. Default: `true`
 * `IMGPROXY_ENFORCE_THUMBNAIL`: when `true` and the source image has an embedded thumbnail, imgproxy will always use the embedded thumbnail instead of the main image. Currently, only thumbnails embedded in `heic` and `avif` are supported. Default: `false`
+* `IMGPROXY_RETURN_ATTACHMENT`: when `true`, response header `Content-Disposition` will include `attachment`. Default: `false`
 * `IMGPROXY_HEALTH_CHECK_MESSAGE`: <i class='badge badge-pro'></i> the content of the health check response. Default: `imgproxy is running`
 * `IMGPROXY_HEALTH_CHECK_PATH`: an additional path of the health check. Default: blank

docs/generating_the_url.md

@@ -529,6 +529,15 @@ eth:%enforce_thumbnail
 
 When set to `1`, `t` or `true` and the source image has an embedded thumbnail, imgproxy will always use the embedded thumbnail instead of the main image. Currently, only thumbnails embedded in `heic` and `avif` are supported. This is normally controlled by the [IMGPROXY_ENFORCE_THUMBNAIL](configuration.md#miscellaneous) configuration but this procesing option allows the configuration to be set for each request.
 
+### Return attachment
+
+```
+return_attachment:%return_attachment
+att:%return_attachment
+```
+
+When set to `1`, `t` or `true`, imgproxy will return `attachment` in the `Content-Disposition` header, and the browser will open a 'Save as' dialog. This is normally controlled by the [IMGPROXY_RETURN_ATTACHMENT](configuration.md#miscellaneous) configuration but this procesing option allows the configuration to be set for each request.
+
 ### Quality
 
 ```

imagetype/imagetype.go

@@ -54,16 +54,16 @@ var (
 	}
 
 	contentDispositionsFmt = map[Type]string{
-		JPEG: "inline; filename=\"%s.jpg\"",
-		PNG:  "inline; filename=\"%s.png\"",
-		WEBP: "inline; filename=\"%s.webp\"",
-		GIF:  "inline; filename=\"%s.gif\"",
-		ICO:  "inline; filename=\"%s.ico\"",
-		SVG:  "inline; filename=\"%s.svg\"",
-		HEIC: "inline; filename=\"%s.heic\"",
-		AVIF: "inline; filename=\"%s.avif\"",
-		BMP:  "inline; filename=\"%s.bmp\"",
-		TIFF: "inline; filename=\"%s.tiff\"",
+		JPEG: "%s; filename=\"%s.jpg\"",
+		PNG:  "%s; filename=\"%s.png\"",
+		WEBP: "%s; filename=\"%s.webp\"",
+		GIF:  "%s; filename=\"%s.gif\"",
+		ICO:  "%s; filename=\"%s.ico\"",
+		SVG:  "%s; filename=\"%s.svg\"",
+		HEIC: "%s; filename=\"%s.heic\"",
+		AVIF: "%s; filename=\"%s.avif\"",
+		BMP:  "%s; filename=\"%s.bmp\"",
+		TIFF: "%s; filename=\"%s.tiff\"",
 	}
 )
 
@@ -93,27 +93,33 @@ func (it Type) Mime() string {
 	return "application/octet-stream"
 }
 
-func (it Type) ContentDisposition(filename string) string {
+func (it Type) ContentDisposition(filename string, returnAttachment bool) string {
+	disposition := "inline"
+
+	if returnAttachment {
+		disposition = "attachment"
+	}
+
 	format, ok := contentDispositionsFmt[it]
 	if !ok {
-		return "inline"
+		return disposition
 	}
 
-	return fmt.Sprintf(format, strings.ReplaceAll(filename, `"`, "%22"))
+	return fmt.Sprintf(format, disposition, strings.ReplaceAll(filename, `"`, "%22"))
 }
 
-func (it Type) ContentDispositionFromURL(imageURL string) string {
+func (it Type) ContentDispositionFromURL(imageURL string, returnAttachment bool) string {
 	url, err := url.Parse(imageURL)
 	if err != nil {
-		return it.ContentDisposition(contentDispositionFilenameFallback)
+		return it.ContentDisposition(contentDispositionFilenameFallback, returnAttachment)
 	}
 
 	_, filename := filepath.Split(url.Path)
 	if len(filename) == 0 {
-		return it.ContentDisposition(contentDispositionFilenameFallback)
+		return it.ContentDisposition(contentDispositionFilenameFallback, returnAttachment)
 	}
 
-	return it.ContentDisposition(strings.TrimSuffix(filename, filepath.Ext(filename)))
+	return it.ContentDisposition(strings.TrimSuffix(filename, filepath.Ext(filename)), returnAttachment)
 }
 
 func (it Type) SupportsAlpha() bool {

options/processing_options.go

@@ -89,6 +89,7 @@ type ProcessingOptions struct {
 	StripColorProfile bool
 	AutoRotate        bool
 	EnforceThumbnail  bool
+	ReturnAttachment  bool
 
 	SkipProcessingFormats []imagetype.Type
 
@@ -140,6 +141,7 @@ func NewProcessingOptions() *ProcessingOptions {
 			StripColorProfile: config.StripColorProfile,
 			AutoRotate:        config.AutoRotate,
 			EnforceThumbnail:  config.EnforceThumbnail,
+			ReturnAttachment:  config.ReturnAttachment,
 
 			// Basically, we need this to update ETag when `IMGPROXY_QUALITY` is changed
 			defaultQuality: config.Quality,
@@ -859,6 +861,16 @@ func applyEnforceThumbnailOption(po *ProcessingOptions, args []string) error {
 	return nil
 }
 
+func applyReturnAttachmentOption(po *ProcessingOptions, args []string) error {
+	if len(args) > 1 {
+		return fmt.Errorf("Invalid return_attachment arguments: %v", args)
+	}
+
+	po.ReturnAttachment = parseBoolOption(args[0])
+
+	return nil
+}
+
 func applyURLOption(po *ProcessingOptions, name string, args []string) error {
 	switch name {
 	case "resize", "rs":
@@ -913,6 +925,8 @@ func applyURLOption(po *ProcessingOptions, name string, args []string) error {
 		return applyStripColorProfileOption(po, args)
 	case "enforce_thumbnail", "eth":
 		return applyEnforceThumbnailOption(po, args)
+	case "return_attachment", "att":
+		return applyReturnAttachmentOption(po, args)
 	// Saving options
 	case "quality", "q":
 		return applyQualityOption(po, args)

processing_handler.go

@@ -86,9 +86,9 @@ func setVary(rw http.ResponseWriter) {
 func respondWithImage(reqID string, r *http.Request, rw http.ResponseWriter, statusCode int, resultData *imagedata.ImageData, po *options.ProcessingOptions, originURL string, originData *imagedata.ImageData) {
 	var contentDisposition string
 	if len(po.Filename) > 0 {
-		contentDisposition = resultData.Type.ContentDisposition(po.Filename)
+		contentDisposition = resultData.Type.ContentDisposition(po.Filename, po.ReturnAttachment)
 	} else {
-		contentDisposition = resultData.Type.ContentDispositionFromURL(originURL)
+		contentDisposition = resultData.Type.ContentDispositionFromURL(originURL, po.ReturnAttachment)
 	}
 
 	rw.Header().Set("Content-Type", resultData.Type.Mime())