Bug 1571247 - don't default to the jfif extension for image/jpeg files as suggested by the Windows registry, r=agashlin

Differential Revision: https://phabricator.services.mozilla.com/D87371

uriloader/exthandler/nsExternalHelperAppService.cpp

@@ -487,7 +487,7 @@ static const nsExtraMimeTypeEntry extraMimeEntries[] = {
     {IMAGE_BMP, "bmp", "BMP Image"},
     {IMAGE_GIF, "gif", "GIF Image"},
     {IMAGE_ICO, "ico,cur", "ICO Image"},
-    {IMAGE_JPEG, "jpeg,jpg,jfif,pjpeg,pjp", "JPEG Image"},
+    {IMAGE_JPEG, "jpg,jpeg,jfif,pjpeg,pjp", "JPEG Image"},
     {IMAGE_PNG, "png", "PNG Image"},
     {IMAGE_APNG, "apng", "APNG Image"},
     {IMAGE_TIFF, "tiff,tif", "TIFF Image"},
@@ -528,6 +528,9 @@ static const nsExtraMimeTypeEntry extraMimeEntries[] = {
     {AUDIO_MIDI, "mid", "Standard MIDI Audio"},
     {APPLICATION_WASM, "wasm", "WebAssembly Module"}};
 
+static const nsDefaultMimeTypeEntry sForbiddenPrimaryExtensions[] = {
+    {IMAGE_JPEG, "jfif"}};
+
 /**
  * File extensions for which decoding should be disabled.
  * NOTE: These MUST be lower-case and ASCII.
@@ -2631,6 +2634,17 @@ NS_IMETHODIMP nsExternalHelperAppService::GetFromTypeAndExtension(
     LOG(("Falling back to 'File' file description\n"));
   }
 
+  // Sometimes, OSes give us bad data. We have a set of forbidden extensions
+  // for some MIME types. If the primary extension is forbidden,
+  // overwrite it with a known-good one. See bug 1571247 for context.
+  nsAutoCString primaryExtension;
+  (*_retval)->GetPrimaryExtension(primaryExtension);
+  if (!primaryExtension.EqualsIgnoreCase(PromiseFlatCString(aFileExt).get())) {
+    if (MaybeReplacePrimaryExtension(primaryExtension, *_retval)) {
+      (*_retval)->GetPrimaryExtension(primaryExtension);
+    }
+  }
+
   // Finally, check if we got a file extension and if yes, if it is an
   // extension on the mimeinfo, in which case we want it to be the primary one
   if (!aFileExt.IsEmpty()) {
@@ -2642,6 +2656,7 @@ NS_IMETHODIMP nsExternalHelperAppService::GetFromTypeAndExtension(
       nsAutoCString fileExt;
       ToLowerCase(aFileExt, fileExt);
       (*_retval)->SetPrimaryExtension(fileExt);
+      primaryExtension = fileExt;
     }
   }
 
@@ -2649,9 +2664,7 @@ NS_IMETHODIMP nsExternalHelperAppService::GetFromTypeAndExtension(
   // type is in our list; these are file formats supported by Firefox and
   // we don't want other brands positioning themselves as the sole viewer
   // for a system.
-  nsAutoCString primaryExtension;
-  rv = (*_retval)->GetPrimaryExtension(primaryExtension);
-  if (NS_SUCCEEDED(rv)) {
+  if (!primaryExtension.IsEmpty()) {
     for (const char* ext : descriptionOverwriteExtensions) {
       if (primaryExtension.Equals(ext)) {
         nsCOMPtr<nsIStringBundleService> bundleService =
@@ -2680,10 +2693,8 @@ NS_IMETHODIMP nsExternalHelperAppService::GetFromTypeAndExtension(
     nsAutoCString type;
     (*_retval)->GetMIMEType(type);
 
-    nsAutoCString ext;
-    (*_retval)->GetPrimaryExtension(ext);
     LOG(("MIME Info Summary: Type '%s', Primary Ext '%s'\n", type.get(),
-         ext.get()));
+         primaryExtension.get()));
   }
 
   return NS_OK;
@@ -2890,6 +2901,26 @@ nsresult nsExternalHelperAppService::FillMIMEInfoForExtensionFromExtras(
   return FillMIMEInfoForMimeTypeFromExtras(type, true, aMIMEInfo);
 }
 
+bool nsExternalHelperAppService::MaybeReplacePrimaryExtension(
+    const nsACString& aPrimaryExtension, nsIMIMEInfo* aMIMEInfo) {
+  for (const auto& entry : sForbiddenPrimaryExtensions) {
+    if (aPrimaryExtension.LowerCaseEqualsASCII(entry.mFileExtension)) {
+      nsDependentCString mime(entry.mMimeType);
+      for (const auto& extraEntry : extraMimeEntries) {
+        if (mime.LowerCaseEqualsASCII(extraEntry.mMimeType)) {
+          nsDependentCString goodExts(extraEntry.mFileExtensions);
+          int32_t commaPos = goodExts.FindChar(',');
+          commaPos = commaPos == kNotFound ? goodExts.Length() : commaPos;
+          auto goodExt = Substring(goodExts, 0, commaPos);
+          aMIMEInfo->SetPrimaryExtension(goodExt);
+          return true;
+        }
+      }
+    }
+  }
+  return false;
+}
+
 bool nsExternalHelperAppService::GetTypeFromExtras(const nsACString& aExtension,
                                                    nsACString& aMIMEType) {
   NS_ASSERTION(!aExtension.IsEmpty(), "Empty aExtension parameter!");

uriloader/exthandler/nsExternalHelperAppService.h

@@ -143,6 +143,14 @@ class nsExternalHelperAppService : public nsIExternalHelperAppService,
   nsresult FillMIMEInfoForExtensionFromExtras(const nsACString& aExtension,
                                               nsIMIMEInfo* aMIMEInfo);
 
+  /**
+   * Replace the primary extension of the mimeinfo object if it's in our
+   * list of forbidden extensions. This fixes up broken information
+   * provided to us by the OS.
+   */
+  bool MaybeReplacePrimaryExtension(const nsACString& aPrimaryExtension,
+                                    nsIMIMEInfo* aMIMEInfo);
+
   /**
    * Searches the "extra" array for a MIME type, and gets its extension.
    * @param aExtension The extension to search for