From: "Alejandro Colomar (man-pages)" <alx.manpages@gmail.com>
To: Dave Chupreev <cdn.dev@yandex.ru>
Cc: linux-man <linux-man@vger.kernel.org>,
GNU C Library <libc-alpha@sourceware.org>,
"Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>,
Roland McGrath <roland@hack.frob.com>
Subject: Re: Bug reporting
Date: Thu, 6 May 2021 00:37:33 +0200 [thread overview]
Message-ID: <9068beb3-70a7-ad96-e260-f53a886d622c@gmail.com> (raw)
In-Reply-To: <1621111620246345@mail.yandex.ru>
[ added a few CCs ]
Hello Dave,
On 5/5/21 10:30 PM, Dave Chupreev wrote:
> Hello, Alejandro.
>
> On page 138
I guess you refer to TLPI, written by Michael.
>
> 1.
>
> Your version of /unsetenv() /should check to see whether there
> are multiple definitions of an environment variable, and remove
> them all.
>
> How can I add such variables which have many definitions? According to
> *putenv* and *setenv* functions, variables with the same names are
> replaced if encountered.
I haven't read that part of the book yet, so I ignore the context. But
AFAIK, that can't happen on Linux, as you pointed out (probably neither
on Unix systems in general, but I don't know for sure, probably Michael
does). I guess the only possibility is if an attacker somehow modified
your environment and inserted multiple copies of an env variable.
The book (TLPI) states that glibc does check that, so I digged into the
sources and found that in <stdlib/setenv.c>, around line 290
(<https://sourceware.org/git?p=glibc.git;a=blob;f=stdlib/setenv.c;h=893f081af6b5a21b999a4056757fd69d1386c0d4;hb=HEAD#l290>).
That behavior was introduced by Roland in commit
196980f5117c8d38f10d64bf67eeb0924651675f
(<https://sourceware.org/git/?p=glibc.git;a=commit;h=196980f5117c8d38f10d64bf67eeb0924651675f>),
so maybe he can better explain the reasons behind the change (the commit
msg is quite unexplicative) if he still remembers (that goes back to 1995).
Regards,
Alex
--
Alejandro Colomar
Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/
http://www.alejandro-colomar.es/
next parent reply other threads:[~2021-05-05 22:37 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1621111620246345@mail.yandex.ru>
2021-05-05 22:37 ` Alejandro Colomar (man-pages) [this message]
[not found] ` <1492841620310804@mail.yandex.ru>
2021-05-09 16:40 ` Michael Kerrisk (man-pages)
2021-05-09 17:20 ` Alexander Monakov
2021-05-09 17:58 ` Michael Kerrisk (man-pages)
2004-08-09 23:38 Benno
2004-08-09 23:47 ` Roland McGrath
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