Allocation of Resources Without Limits or Throttling

Summary

The package grpc prior to 1.53.2, 1.54.x prior to 1.54.3, 1.55.x prior to 1.55.2, 1.56.x prior to 1.56.2 contains a vulnerability that allows "hpack" table accounting errors which could lead to unwanted disconnects between clients and servers in exceptional cases/ Three vectors were found that allow the following DOS (Denial of Service) attacks: - Unbounded memory buffering in the "HPACK" parser - Unbounded CPU consumption in the "HPACK" parser The unbounded CPU consumption is down to a copy that occurred per-input-block in the parser, and because that could be unbounded due to the memory copy bug we end up with an "O(n^2)" parsing loop, with "n" selected by the client. The unbounded memory buffering bugs: - The header size limit check was behind the string reading code, so we needed to first buffer up to a 4 gigabyte string before rejecting it as longer than 8 or 16kb. - "HPACK" varints have an encoding quirk whereby an infinite number of "0's" can be added at the start of an integer. gRPC's "hpack" parser needed to read all of them before concluding a parse. - gRPC's metadata overflow check was performed per frame, so that the following sequence of frames could cause infinite buffering: HEADERS: containing a: 1 CONTINUATION: containing a: 2 CONTINUATION: containing a: 3 etc...