This is useful to easily distinguish missing files from corrupted keys.
All existing usage sites have been modified so there is no behavior
change in this commit.
Our current code should never write these, because we have an allowlist
of thumbnail sizes. None of the allowed sizes contain a 0xFF byte. We
have observed keys with a 0xFF in the thumbnail size a couple times on
real servers, and believe an early version of conduit wrote these before
the allowlist was added.
These keys were originally handled correctly, and were broken by
e2cba15ed2. Before that commit, we were
parsing media keys backwards, and never tried to read the thumbnail size
or mxc url.
Fixes a regression in e2cba15ed2 where the
Content-Type and Content-Disposition parts are extracted in the wrong
order.
Fixes a long-standing issue in b6d721374f
where the Content-Type part was allowed to be completely missing rather
than present and 0 bytes long.
Improves the error messages for various parsing failures to be unique
and more obvious.
On my HS I observed 5 instances of keys with the following format:
* MXC bytes.
* A 0xFF byte.
* 4 bytes where the width and height are supposed to be, which are
supposed to be 8 bytes in length.
* 3 consecutive 0xFF bytes. This means that the `content-type` and
`content-disposition` sections both parse as the empty string, and
there's an extra separator at the end too.
* Extra bytes, all of which were `image/png`.
The 4 bytes where the width and height are supposed to be were one of:
* 003ED000
* 003EE000
* 003EF001
Which seems to have some kind of pattern to it...
After much digging, we have absolutely no idea what could've caused
this. Cursed.
Leaving this private in `database::key_value::media` because the way
the metadata is encoded in media keys is a mess. I want to fix that in
the future, and want to limit the number of things that rely on it for
now.
This change is fully automated, except the `rustfmt.toml` changes and
a few clippy directives to allow specific functions with too many lines
because they are longer now.
