Reading on uninitialized buffer may cause UB

[JOE1994]

Hello 🦀 ,
we (Rust group @sslab-gatech) found a memory-safety/soundness issue in this crate while scanning Rust code on crates.io for potential vulnerabilities.

Issue Description

cassandra-proto/src/frame/parser_async.rs

Lines 46 to 51 in 9bdbc91

	let mut body_bytes = Vec::with_capacity(length);
	unsafe {
	body_bytes.set_len(length);
	}
	proceed_if_filled!(cursor.read(&mut body_bytes), length);

cassandra-proto/src/frame/parser_async.rs

Lines 65 to 69 in 9bdbc91

	let mut tracing_bytes = Vec::with_capacity(UUID_LEN);
	unsafe {
	tracing_bytes.set_len(UUID_LEN);
	}
	body_cursor.read_exact(&mut tracing_bytes)?;

We found two cases where an uninitialized buffer is created (body_bytes & tracing_bytes) and passed to user-provided Read implementation. This is unsound, because it allows safe Rust code to exhibit an undefined behavior (read from uninitialized memory).

This part from the Read trait documentation explains the issue:

It is your responsibility to make sure that buf is initialized before calling read. Calling read with an uninitialized buf (of the kind one obtains via MaybeUninit<T>) is not safe, and can lead to undefined behavior.

Suggested Fix

It is safe to zero-initialize the newly allocated u8 buffer before read(), in order to prevent user-provided Read from accessing old contents of the newly allocated heap memory.

Thank you for checking out this issue 👍

[AlexPikalov]

Thank you @JOE1994