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Undocumented capacity limit for HeaderMap #603
Description
HeaderMap has a capacity limit of 24576 headers. Adding any more headers triggers a panic when reserving more capacity.
I can't see any way to prevent the panic when handling incoming headers, except to hard-wire a check for this value into calling code.
It would be useful to expose this value as a public constant.
At the very least it should be documented. Currently HeaderMap::reserve says "Panics if the new allocation size overflows usize." This should be "Panics if the new allocation size is greater than 24576."
Activity
seanmonstar commentedon Apr 28, 2023
Good catch, thanks for reporting this! I'd propose a few improvements:
reserveto say "panicks if the new size is larger than the internal max. See struct docs for more."try_reservemethod. This changes the task from a docs fix to a feature request, so perhaps that should be a separate ticket if anyone wants this method.DDtKey commentedon Jul 18, 2023
I believe the correct way to fix that is to introduce fallible
try_appendmethod.It's too fragile to rely on reservation methods & documentation only and easy to miss the handling.
It's clearly vulnerability right now, because all usages like this one will cause a panic
cc @seanmonstar
seanmonstar commentedon Jul 18, 2023
Yea, I think the three bullet points I listed above would be a great addition. Want to submit a PR?