Message-ID: <5d675cbe-7837-e9ae-961d-be7d03201f3b@mit.edu>
Date: Tue, 19 Oct 2021 02:44:03 -0700
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Subject: Re: [PATCH] Prefer getenv("HOME") to find the UNIX home directory
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To: Kyotaro Horiguchi <horikyota.ntt@gmail.com>, alvherre@alvh.no-ip.org
Cc: pgsql-hackers@lists.postgresql.org
References: <1634252654444.90107@mit.edu>
 <202110182223.zeze33l55qa5@alvherre.pgsql>
 <20211019.173422.706584612464055211.horikyota.ntt@gmail.com>
From: Anders Kaseorg <andersk@mit.edu>
In-Reply-To: <20211019.173422.706584612464055211.horikyota.ntt@gmail.com>
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On 10/19/21 01:34, Kyotaro Horiguchi wrote:
> I tend to agree to this, but seeing ssh ignoring $HOME, I'm not sure
> it's safe that we follow the variable at least when accessing
> confidentiality(?) files.  Since I don't understand the exact
> reasoning for the ssh's behavior so it's just my humbole opinion.

According to https://bugzilla.mindrot.org/show_bug.cgi?id=3048#c1, it 
used to be supported to install the ssh binary as setuid.  A 
setuid/setgid binary needs to treat all environment variables with 
suspicion: if it can be convinced to write a file to $HOME with root 
privileges, then a user who modifies $HOME before invoking the binary 
could cause it to write to a file that the user normally couldn’t.

There’s no such concern for a binary that isn’t setuid/setgid.  Anyone 
with the ability to modify $HOME can be assumed to already have full 
control of the user account.

Anders