full-disclosure - [FD] getenv("=A") works (no particular vulnerability)

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Message-ID: <1643992186.462126538@f427.i.mail.ru>
Date: Fri, 04 Feb 2022 19:29:46 +0300
From: Askar Safin via Fulldisclosure
 <fulldisclosure@...lists.org>
To: fulldisclosure@...lists.org
Subject: [FD] getenv("=A") works (no particular vulnerability)

TL;DR: this mail doesn't contain any actual vulnerability, just an idea.

Consider this C code for Linux and glibc:

---------
#define _GNU_SOURCE 1
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
char *new_env[] = {"=A=B", 0};
int
main ()
{
  environ = new_env;
  printf("%s\n", getenv("=A")); // prints "B"
  return 0;
}
---------

This code prints "B". I. e. glibc allows variables starting with "=". It is quite possible such behavior can lead to various vulnerabilities.

It is possible this list is inappropriate for such message. If so, please, say, where I should post such message next time.

==
Askar Safin
http://safinaskar.com
https://sr.ht/~safinaskar
https://github.com/safinaskar

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