Images sent via Matrix not viewable in Signal App

[jaller94]

Images I send to a bridged room are often not visible in my Signal Android App.

Steps to reproduce

1. Connect the Signal bridge and open a group room.
2. Send an image from Element Web.

Expected

In the Signal App on Android, the images are visible both as a preview and when clicking on them.

Actual

In the Signal App on Android, the images don't have previews and may not even be visible when clicking on them (which displays them fullscreen).

Files (please pin if you want to keep them after 2022-01-01)

https://gateway.pinata.cloud/ipfs/Qmeu51MUY5UfY3cPCC7moiMvt5ttFnfxqniqug9uthGQvf

File	Description	Preview visible	Visible after click
IMG_20210926_141515.jpg	3,8 MB JPG photo 4608x3456	no	:heavy_check_mark:
Rectangle-mask.png	27 KB PNG 1024x1024	no	no
watercooler.jpg	42 KB JPG 851x851	no	no

Software

Signal bridge: 0.2.0 Element Web: 1.9.2 Signal on Android 10: 5.24.17

[freaktechnik]

I have only noticed this since enabling e2be, though that may be coincidental.

[freaktechnik]

example event (decrypted by element web) that has this issue:

{
  "content": {
    "msgtype": "m.image",
    "body": "img_20211212_170044.jpg",
    "filename": "img_20211212_170044.jpg",
    "file": {
      "url": "mxc://humanoids.be/<mid>",
      "mimetype": "image/jpeg",
      "v": "v2",
      "key": {
        "alg": "A256CTR",
        "ext": true,
        "k": "<key>",
        "key_ops": [
          "encrypt",
          "decrypt"
        ],
        "kty": "oct"
      },
      "iv": "<iv>",
      "hashes": {
        "sha256": "<sha256>"
      }
    },
    "info": {
      "mimetype": "image/jpeg",
      "size": 2261375,
      "thumbnail_file": {
        "url": "mxc://humanoids.be/<tid>",
        "mimetype": "image/jpeg",
        "v": "v2",
        "key": {
          "alg": "A256CTR",
          "ext": true,
          "k": "<key>",
          "key_ops": [
            "encrypt",
            "decrypt"
          ],
          "kty": "oct"
        },
        "iv": "<iv>",
        "hashes": {
          "sha256": "<sha256>"
        }
      },
      "thumbnail_info": {
        "mimetype": "image/jpeg",
        "size": 45438,
        "xyz.amorgan.blurhash": "<bh>"
      }
    }
  },
  "type": "m.room.message",
  "room_id": "!<id>:humanoids.be"
}

The event was created by fluffychat and is flawlessly decrypted (including the image) by element web. The original event was encrypted with m.megolm.v1.aes-sha2. I wonder if it might be an issue where the bridge doesn't immediately have the key to decrypt or similar? When I looked at the media handling code a while ago it seemed like that should be properly decrypting the image, since my suspicion was that images were sent encrypted to Signal.

[tulir]

@freaktechnik Encrypted files sent by FluffyChat are not spec-compliant, so they'll fail to decrypt.

[freaktechnik]

It works fine with the whatsapp bridge though?