sharing an iOS Screenshot results in a PNG with e prepend bplist

[logitab]

Describe the bug
[edit: see below, sharing a just created iOS screenshot results in the same issue. It is not needed to use the X app to reproduce this]

Sharing an image from X/Twitter app results in an file with a prepend bplist before the PNG header/data. This does not happen with Monal e.g. . For some reason you sharing from e.g. nextcloud App doesn't have this problem. This startet to happen around the End of iOS 17 series.

To Reproduce
Steps to reproduce the behavior:

1. in X App tip on image to show it in fullscreen
2. longpress to show shareing menu
3. share it via siskin-im
4. the picture is not displayed as a picture
5. safe the "picture" and open it in a hex editor of your choice
6. you will find a bplist followed by an PNG

Expected behavior
There should be just a common PNG

Details (please complete the following information):

• Siskin Version: 7.3.3
• iOS version iOS 18.3.2
• iPhone model 13

example data:
00000000: 6270 6c69 7374 3030 d401 0203 0405 0607 bplist00........
00000010: 0a58 2476 6572 7369 6f6e 5924 6172 6368 .X$versionY$arch
00000020: 6976 6572 5424 746f 7058 246f 626a 6563 iverT$topX$objec
00000030: 7473 1200 0186 a05f 100f 4e53 4b65 7965 ts.......NSKeye
00000040: 6441 7263 6869 7665 72d1 0809 5472 6f6f dArchiver...Troo
00000050: 7480 01a9 0b0c 2e2f 3034 383f 4355 246e t....../048?CU$n
00000060: 756c 6cdf 1011 0d0e 0f10 1112 1314 1516 ull.............
00000070: 1718 191a 1b1c 1d1e 1f20 201f 231f 2526 ......... .#.%&
00000080: 2723 281f 2a2b 2c25 5b55 4949 6d61 6765 '#(.*+,%[UIImage
00000090: 4461 7461 5f10 1955 4949 6d61 6765 4163 Data..UIImageAc
000000a0: 6365 7373 6962 696c 6974 794c 6162 656c cessibilityLabel
000000b0: 5f10 1455 494b 6974 5761 6e74 7350 726f ..UIKitWantsPro
000000c0: 7065 7274 6965 735e 5549 4b69 7444 6964 perties^UIKitDid
000000d0: 456e 636f 6465 5f10 1161 6363 6573 7369 Encode..accessi
000000e0: 6269 6c69 7479 4869 6e74 5f10 0f55 4952 bilityHint_..UIR
000000f0: 656e 6465 7269 6e67 4d6f 6465 5f10 1c55 enderingMode_..U
00000100: 4949 6d61 6765 4163 6365 7373 6962 696c IImageAccessibil
00000110: 6974 794c 616e 6775 6167 655c 5549 4861 ityLanguage\UIHa
00000120: 7350 6174 7465 726e 5f10 1655 4949 6d61 sPattern_..UIIma
00000130: 6765 5472 6169 7443 6f6c 6c65 6374 696f geTraitCollectio
00000140: 6e56 2463 6c61 7373 5f10 1255 4949 6d61 nV$class_..UIIma
00000150: 6765 4f72 6965 6e74 6174 696f 6e5f 1014 geOrientation_..
00000160: 5549 496d 6167 6543 6f6e 6669 6775 7261 UIImageConfigura
00000170: 7469 6f6e 5f10 1261 6363 6573 7369 6269 tion_..accessibi
00000180: 6c69 7479 5661 6c75 6557 5549 5363 616c lityValueWUIScal
00000190: 655f 1013 5549 496d 6167 6553 697a 6549 e_..UIImageSizeI
000001a0: 6e50 6978 656c 735f 1014 5549 496d 6167 nPixels_..UIImag
000001b0: 6556 6172 6961 626c 6556 616c 7565 5f10 eVariableValue_.
000001c0: 1d55 4949 6d61 6765 4973 466c 6970 7065 .UIImageIsFlippe
000001d0: 6449 6e52 6967 6874 546f 4c65 6674 8002 dInRightToLeft..
000001e0: 8000 0909 8000 1000 8000 0880 0580 0880 ................
000001f0: 0480 0022 4000 0000 8003 237f f000 0000 ..."@.....#.....
00000200: 0000 0008 4f12 0010 546d 8950 4e47 0d0a ....O...Tm.PNG..
00000210: 1a0a 0000 000d 4948 4452 0000 0438 0000 ......IHDR...8..
00000220: 0438 0802 0000 0063 72fb d800 0000 0173 .8.....cr......s
00000230: 5247 4200 aece 1ce9 0000 0084 6558 4966 RGB.........eXIf
00000240: 4d4d 002a 0000 0008 0005 0112 0003 0000 MM.*............
[...]

[hantu85]

Have you seen this issue with any other app or just with X/Twitter?

[logitab]

I have seen this with other Apps besides X too, but I can't remeber which. IMO this behavior startet after an upgrade from some iOS 17.x to another iOS17.x+1, but it still remains to the current iOS 18. Also this behavior does not occur with monal on the same xmpp account.

There is a problem sharing a png from the Apple notes app too. If you try it, a message is displayed that it cant read "a representation of type public.png. Again it does work with monal.

[hantu85]

Could you check and tell me the value of image quality setting in Siskin IM (in Media)?

I was asking about other apps causing the issue as I no longer have X/Twitter account and I would prefer not to create one.

[logitab]

The image quality is set to "original" in Siskin. Trying it to set to something different ends up in a message "Feature not supported by XMPP server", while sharing with X/Twitter. Setting it back to "original" ends up in the same bevavior with the prepend bplist.

I tried setting image quality to original in monal and sharing from X, it ended up in a PNG with a file extension of .png. Setting it to som e smaller quality it ends up in a jpeg with a .jpg extention.

sharing an image in X to the apple notepad ends up in a jpeg with .jpeg extension.

I tried to find a different app with the same symptoms, no luck so far. The BlueSky app does share an image with file extention PNG but it really is an jpeg, which is a bit strange. (sent with "original" quality in siskin).

hope this helps

[logitab]

There is a much easier way to reproduce this bug. Just take a iOS screenshot and share it via siskin. The result is a .jpeg file, but in reality it is a PNG with a prepend bplist. Mediaquality set to "original".

[hantu85]

Thank you for taking time to find another way to reproduce this issue. I was able to resolve it, although I still think that is an Apple bug in the iOS method to return file representation of the shared item. If I ask for the image file, I should receive and image file.

The fix is part of the version 7.4.0-b2 that is available for testing using TestFlight.

Please note that we no longer are using Github issue tracker as Siskin IM has a separate bug tracker, see https://tigase.dev/tigase/_clients/siskin-im/~issues/598