[bug] Bad request when trying to use very small avatars/banners

[Craftplacer]

Describe the bug with a clear and concise description of what the bug is.

When trying to upload an image that's too small (1x1 image for example) as the avatar or banner the backend just returns Bad Request.

What's your GoToSocial Version?

v0.11.1 git-c7a46e0

GoToSocial Arch

arm64 binary

[igalic]

how big in bytes are these files?
what, exactly does the backend say, other than bad request?
what do the logs say?

[tsmethurst]

It's probably giving bad request because the image is too small for us to derive the type from the magic bytes. Not 100% sure though, logs would be helpful.

[Craftplacer]

The only output I see via journalctl is

func=server.glob..func1.Logger.func13.1 level=INFO latency="1.903055ms" method=PATCH statusCode=400 path=/api/v1/accounts/update_credentials msg="Bad Request: wrote 47B"

I used a one-pixel GIF this time, which is 35b.

[tsmethurst]

Could you check the response via the network tab (or equivalent for your browser) when doing an upload via the settings panel? That should give more information, i hope.

[Craftplacer]

The only "information" I could get from the failed request is this:

{"error":"Bad Request"}

[tsmethurst]

Alright, annoying that it gives no errors, but that's OK. I'm fairly sure it's here where it's going wrong:

gotosocial/internal/media/processingmedia.go

Lines 159 to 162 in 39e22a9

	// Byte buffer to read file header into.
	// See: https://en.wikipedia.org/wiki/File_format#File_header
	// and https://github.com/h2non/filetype
	hdrBuf := make([]byte, 261)

We use those first 261 bytes as the 'magic' bytes for working out what format a file is. So a 35b 1-pixel gif isn't gonna work there. An 8x8 pixel gif or something, on the other hand, would probably work.

[Craftplacer]

The problem with this use case of solid colors & efficient image codecs is that no matter what the resolution is, you won't exceed the necessary bytes until you introduce noise or just simply upload an actual complex image.

Reading the README of h2non/filetype: the buffer does not need to be filled, so maybe some kind of IO method is not being used correctly.

[tsmethurst]

Yes probably something like that. We'll take a better look at it when time allows.

[igalic]

Alright, annoying that it gives no errors, but that's OK. I'm fairly sure it's here where it's going wrong:

gotosocial/internal/media/processingmedia.go

Lines 159 to 162 in 39e22a9

	// Byte buffer to read file header into.
	// See: https://en.wikipedia.org/wiki/File_format#File_header
	// and https://github.com/h2non/filetype
	hdrBuf := make([]byte, 261)

We use those first 261 bytes as the 'magic' bytes for working out what format a file is. So a 35b 1-pixel gif isn't gonna work there. An 8x8 pixel gif or something, on the other hand, would probably work.

it's there a way to make this read graceful?
take what's there, even if it's less than 261 bytes?

[KEINOS]

it's there a way to make this read graceful?

I think io.ReadFull is causing the error of unexpected EOF.

gotosocial/internal/media/processingmedia.go

Lines 159 to 167 in 39e22a9

	// Byte buffer to read file header into.
	// See: https://en.wikipedia.org/wiki/File_format#File_header
	// and https://github.com/h2non/filetype
	hdrBuf := make([]byte, 261)
	// Read the first 261 header bytes into buffer.
	if _, err := io.ReadFull(rc, hdrBuf); err != nil {
	return gtserror.Newf("error reading incoming media: %w", err)
	}

How about using copy instead?

func Example() {
	// 1x1 px transparent GIF image
	imgBase64 := "R0lGODlhAQABAIABAP///wAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw=="

	imgBin, err := base64.StdEncoding.DecodeString(imgBase64)
	PanicOnErr(err)

	hdrBuf := make([]byte, 261)

	// rc := bytes.NewReader(imgBin)
	// _, err = io.ReadFull(rc, hdrBuf)
	// PanicOnErr(err)

	_ = copy(hdrBuf, imgBin)

	info, err := filetype.Match(hdrBuf)
	PanicOnErr(err)

	fmt.Printf("%s\n", info.MIME.Value)
	// Output:
	// image/gif
}

func PanicOnErr(err error) {
	if err != nil {
		log.Panic(err)
	}
}

• GoPlayground

If it sounds ok I shall PR.

[tsmethurst]

PR would be great! :)

[KEINOS]

@tsmethurst
PR would be great! :)

Done 👍 Hope it helps!

• [bugfix] allow store smaller PNG image than 261 bytes (#2263) #2298