fix: Treat and send images that can't be decoded as Viewtype::File

Otherwise unsupported and corrupted images are displayed in the "Images" tab in UIs and that looks
as a Delta Chat bug. This should be a rare case though, so log it as error and let the user know
that metadata isn't removed from the image at least.

Author: iequidoo

src/blob.rs

@@ -21,6 +21,7 @@ use crate::constants::{self, MediaQuality};
 use crate::context::Context;
 use crate::events::EventType;
 use crate::log::LogExt;
+use crate::message::Viewtype;
 use crate::tools::sanitize_filename;
 
 /// Represents a file in the blob directory.
@@ -267,15 +268,11 @@ impl<'a> BlobObject<'a> {
                 }
             };
 
-        let maybe_sticker = &mut false;
+        let viewtype = &mut Viewtype::Image;
         let is_avatar = true;
         self.recode_to_size(
-            context,
-            None, // The name of an avatar doesn't matter
-            maybe_sticker,
-            img_wh,
-            max_bytes,
-            is_avatar,
+            context, None, // The name of an avatar doesn't matter
+            viewtype, img_wh, max_bytes, is_avatar,
         )?;
 
         Ok(())
@@ -284,15 +281,14 @@ impl<'a> BlobObject<'a> {
     /// Recodes an image pointed by a [BlobObject] so that it fits into limits on the image width,
     /// height and file size specified by the config.
     ///
-    /// On some platforms images are passed to the core as [`crate::message::Viewtype::Sticker`] in
-    /// which case `maybe_sticker` flag should be set. We recheck if an image is a true sticker
-    /// assuming that it must have at least one fully transparent corner, otherwise this flag is
-    /// reset.
+    /// On some platforms images are passed to Core as [`Viewtype::Sticker`]. We recheck if the
+    /// image is a true sticker assuming that it must have at least one fully transparent corner,
+    /// otherwise `*viewtype` is set to `Viewtype::Image`.
     pub async fn recode_to_image_size(
         &mut self,
         context: &Context,
         name: Option<String>,
-        maybe_sticker: &mut bool,
+        viewtype: &mut Viewtype,
     ) -> Result<String> {
         let (img_wh, max_bytes) =
             match MediaQuality::from_i32(context.get_config_int(Config::MediaQuality).await?)
@@ -305,10 +301,7 @@ impl<'a> BlobObject<'a> {
                 MediaQuality::Worse => (constants::WORSE_IMAGE_SIZE, constants::WORSE_IMAGE_BYTES),
             };
         let is_avatar = false;
-        let new_name =
-            self.recode_to_size(context, name, maybe_sticker, img_wh, max_bytes, is_avatar)?;
-
-        Ok(new_name)
+        self.recode_to_size(context, name, viewtype, img_wh, max_bytes, is_avatar)
     }
 
     /// Recodes the image so that it fits into limits on width/height and byte size.
@@ -326,7 +319,7 @@ impl<'a> BlobObject<'a> {
         &mut self,
         context: &Context,
         name: Option<String>,
-        maybe_sticker: &mut bool,
+        viewtype: &mut Viewtype,
         mut img_wh: u32,
         max_bytes: usize,
         is_avatar: bool,
@@ -337,6 +330,7 @@ impl<'a> BlobObject<'a> {
         let no_exif_ref = &mut no_exif;
         let mut name = name.unwrap_or_else(|| self.name.clone());
         let original_name = name.clone();
+        let vt = &mut *viewtype;
         let res: Result<String> = tokio::task::block_in_place(move || {
             let mut file = std::fs::File::open(self.to_abs_path())?;
             let (nr_bytes, exif) = image_metadata(&file)?;
@@ -360,16 +354,19 @@ impl<'a> BlobObject<'a> {
             let orientation = exif.as_ref().map(|exif| exif_orientation(exif, context));
             let mut encoded = Vec::new();
 
-            if *maybe_sticker {
+            if *vt == Viewtype::Sticker {
                 let x_max = img.width().saturating_sub(1);
                 let y_max = img.height().saturating_sub(1);
-                *maybe_sticker = img.in_bounds(x_max, y_max)
-                    && (img.get_pixel(0, 0).0[3] == 0
+                if !img.in_bounds(x_max, y_max)
+                    || !(img.get_pixel(0, 0).0[3] == 0
                         || img.get_pixel(x_max, 0).0[3] == 0
                         || img.get_pixel(0, y_max).0[3] == 0
-                        || img.get_pixel(x_max, y_max).0[3] == 0);
+                        || img.get_pixel(x_max, y_max).0[3] == 0)
+                {
+                    *vt = Viewtype::Image;
+                }
             }
-            if *maybe_sticker && exif.is_none() {
+            if *vt == Viewtype::Sticker && exif.is_none() {
                 return Ok(name);
             }
 
@@ -504,10 +501,11 @@ impl<'a> BlobObject<'a> {
             Ok(_) => res,
             Err(err) => {
                 if !is_avatar && no_exif {
-                    warn!(
+                    error!(
                         context,
                         "Cannot recode image, using original data: {err:#}.",
                     );
+                    *viewtype = Viewtype::File;
                     Ok(original_name)
                 } else {
                     Err(err)

src/blob/blob_tests.rs

@@ -140,9 +140,9 @@ async fn test_add_white_bg() {
 
         let mut blob = BlobObject::create_and_deduplicate(&t, &avatar_src, &avatar_src).unwrap();
         let img_wh = 128;
-        let maybe_sticker = &mut false;
+        let viewtype = &mut Viewtype::Image;
         let strict_limits = true;
-        blob.recode_to_size(&t, None, maybe_sticker, img_wh, 20_000, strict_limits)
+        blob.recode_to_size(&t, None, viewtype, img_wh, 20_000, strict_limits)
             .unwrap();
         tokio::task::block_in_place(move || {
             let img = ImageReader::open(blob.to_abs_path())
@@ -188,9 +188,9 @@ async fn test_selfavatar_outside_blobdir() {
     );
 
     let mut blob = BlobObject::create_and_deduplicate(&t, avatar_path, avatar_path).unwrap();
-    let maybe_sticker = &mut false;
+    let viewtype = &mut Viewtype::Image;
     let strict_limits = true;
-    blob.recode_to_size(&t, None, maybe_sticker, 1000, 3000, strict_limits)
+    blob.recode_to_size(&t, None, viewtype, 1000, 3000, strict_limits)
         .unwrap();
     let new_file_size = file_size(&blob.to_abs_path()).await;
     assert!(new_file_size <= 3000);
@@ -400,7 +400,7 @@ async fn test_recode_image_balanced_png() {
     .await
     .unwrap();
 
-    // This will be sent as Image, see [`BlobObject::maybe_sticker`] for explanation.
+    // This will be sent as Image, see [`BlobObject::recode_to_image_size()`] for explanation.
     SendImageCheckMediaquality {
         viewtype: Viewtype::Sticker,
         media_quality_config: "0",

src/chat.rs

@@ -2791,26 +2791,26 @@ async fn prepare_msg_blob(context: &Context, msg: &mut Message) -> Result<()> {
         if msg.viewtype == Viewtype::Vcard {
             msg.try_set_vcard(context, &blob.to_abs_path()).await?;
         }
-
-        let mut maybe_sticker = msg.viewtype == Viewtype::Sticker;
         if !send_as_is
             && (msg.viewtype == Viewtype::Image
-                || maybe_sticker && !msg.param.exists(Param::ForceSticker))
+                || msg.viewtype == Viewtype::Sticker && !msg.param.exists(Param::ForceSticker))
         {
             let new_name = blob
-                .recode_to_image_size(context, msg.get_filename(), &mut maybe_sticker)
+                .recode_to_image_size(context, msg.get_filename(), &mut msg.viewtype)
                 .await?;
             msg.param.set(Param::Filename, new_name);
             msg.param.set(Param::File, blob.as_name());
-
-            if !maybe_sticker {
-                msg.viewtype = Viewtype::Image;
-            }
         }
 
         if !msg.param.exists(Param::MimeType) {
-            if let Some((_, mime)) = message::guess_msgtype_from_suffix(msg) {
-                msg.param.set(Param::MimeType, mime);
+            if let Some((viewtype, mime)) = message::guess_msgtype_from_suffix(msg) {
+                // If we unexpectedly didn't recognize the file as image, don't send it as such,
+                // either the format is unsupported or the image is corrupted.
+                if viewtype != Viewtype::Image
+                    || matches!(msg.viewtype, Viewtype::Image | Viewtype::Sticker)
+                {
+                    msg.param.set(Param::MimeType, mime);
+                }
             }
         }
 

src/chat/chat_tests.rs

@@ -3457,6 +3457,25 @@ async fn test_jpeg_with_png_ext() -> Result<()> {
     Ok(())
 }
 
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn test_nonimage_with_png_ext() -> Result<()> {
+    let alice = TestContext::new_alice().await;
+    let bob = TestContext::new_bob().await;
+
+    let bytes = include_bytes!("../../test-data/message/thunderbird_with_autocrypt.eml");
+    let file = alice.get_blobdir().join("screenshot.png");
+    tokio::fs::write(&file, bytes).await?;
+    let mut msg = Message::new(Viewtype::Image);
+    msg.set_file_and_deduplicate(&alice, &file, Some("screenshot.png"), None)?;
+
+    let alice_chat = alice.create_chat(&bob).await;
+    let sent_msg = alice.send_msg(alice_chat.get_id(), &mut msg).await;
+    assert_eq!(msg.viewtype, Viewtype::File);
+    let msg_bob = bob.recv_msg(&sent_msg).await;
+    assert_eq!(msg_bob.viewtype, Viewtype::File);
+    Ok(())
+}
+
 /// Tests that info message is ignored when constructing `In-Reply-To`.
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn test_info_not_referenced() -> Result<()> {

src/mimeparser.rs

@@ -2123,6 +2123,9 @@ fn get_mime_type(
             mime::OCTET_STREAM => match filename {
                 Some(filename) => {
                     match message::guess_msgtype_from_path_suffix(Path::new(&filename)) {
+                        // Delta Chat sends images as "application/octet-stream" if cannot decode
+                        // them. Behavior of other clients may vary, so keep it simple.
+                        Some((Viewtype::Image, _)) => Viewtype::File,
                         Some((viewtype, _)) => viewtype,
                         None => Viewtype::File,
                     }