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package headers
import (
"mime"
"net/http"
"regexp"
svg "github.com/h2non/go-is-svg"
)
var (
ImageTypeRegex = regexp.MustCompile(`^image/*`)
SvgMimeTypeRegex = regexp.MustCompile(`^image/svg\+xml$`)
TextTypeRegex = regexp.MustCompile(`^text/*`)
VideoTypeRegex = regexp.MustCompile(`^video/*`)
AttachmentRegex = regexp.MustCompile(`^attachment`)
)
// Mime types that can't be inlined. Usually subtypes of main types
var forbiddenInlineTypes = []*regexp.Regexp{SvgMimeTypeRegex}
// Mime types that can be inlined. We can add global types like "image/" or
// specific types like "text/plain". If there is a specific type inside a global
// allowed type that can't be inlined we must add it to the forbiddenInlineTypes var.
// One example of this is the mime type "image". We allow all images to be
// inlined except for SVGs.
var allowedInlineTypes = []*regexp.Regexp{ImageTypeRegex, TextTypeRegex, VideoTypeRegex}
func SafeContentHeaders(data []byte, contentDisposition string) (string, string) {
contentType := safeContentType(data)
contentDisposition = safeContentDisposition(contentType, contentDisposition)
return contentType, contentDisposition
}
func safeContentType(data []byte) string {
// Special case for svg because DetectContentType detects it as text
if svg.Is(data) {
return "image/svg+xml"
}
// Override any existing Content-Type header from other ResponseWriters
contentType := http.DetectContentType(data)
// If the content is text type, we set to plain, because we don't
// want to render it inline if they're html or javascript
if isType(contentType, TextTypeRegex) {
return "text/plain; charset=utf-8"
}
return contentType
}
func safeContentDisposition(contentType string, contentDisposition string) string {
existingDisposition, file := extractContentDispositionFile(contentDisposition)
// If the existing disposition is attachment we return that. This allow us
// to force a download from GitLab (ie: RawController)
if AttachmentRegex.MatchString(existingDisposition) {
return attachmentDisposition(file)
}
// Checks for mime types that are forbidden to be inline
for _, element := range forbiddenInlineTypes {
if isType(contentType, element) {
return attachmentDisposition(file)
}
}
// Checks for mime types allowed to be inline
for _, element := range allowedInlineTypes {
if isType(contentType, element) {
return inlineDisposition(file)
}
}
// Anything else is set to attachment
return attachmentDisposition(file)
}
func extractContentDispositionFile(disposition string) (string, string) {
if disposition == "" {
return "", ""
}
existingDisposition, params, err := mime.ParseMediaType(disposition)
if err != nil {
return "", ""
}
return existingDisposition, params["filename"]
}
func attachmentDisposition(file string) string {
return disposition("attachment", file)
}
func inlineDisposition(file string) string {
return disposition("inline", file)
}
func disposition(disposition string, file string) string {
params := map[string]string{}
if file != "" {
params["filename"] = file
}
return mime.FormatMediaType(disposition, params)
}
func isType(contentType string, mimeType *regexp.Regexp) bool {
return mimeType.MatchString(contentType)
}
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