HPACK decoder panics on invalid input

Due to insufficient checking of input data, decoding certain data sequences can lead to Decoder::decode panicking rather than returning an error.

Example code that triggers this vulnerability looks like this:

use hpack::Decoder;

pub fn main() {
  let input = &[0x3f];
  let mut decoder = Decoder::new();
  let _ = decoder.decode(input);
}

hpack is unmaintained. A crate with the panics fixed has been published as hpack-patched.

Also consider using fluke-hpack or httlib-huffman as an alternative.