From 4886d0dd6c77d029209cc09a9e15a89ffb23b9fc Mon Sep 17 00:00:00 2001
From: Guilhem Moulin <guilhem@fripost.org>
Date: Wed, 17 Feb 2021 19:03:00 +0100
Subject: Sanitize environment when spawning children.

Set $HOME, $USER, $SHELL, $PATH, $LOGNAME to appropriate values (and
perserve $TERM), which matches the login(1) behavior.
---
 Changelog | 2 ++
 lacme     | 7 +++++++
 2 files changed, 9 insertions(+)

diff --git a/Changelog b/Changelog
index cda155f..019c076 100644
--- a/Changelog
+++ b/Changelog
@@ -28,6 +28,8 @@ lacme (0.7.1) upstream;
    useful for OCSP Must-Staple.
  + client: use "lacme-client/$VERSION" as User-Agent header.
  + Consolidate error messages for consistency.
+ + Sanitize environment when spawning the lacme client, webserver and
+   accountd.
  - lacme: delay webserver socket shutdown to after the process has
    terminated.
  - documentation: suggest to generate private key material with
diff --git a/lacme b/lacme
index f0beac1..a5ba9f4 100755
--- a/lacme
+++ b/lacme
@@ -234,6 +234,13 @@ sub drop_privileges($$$) {
         die "Couldn't setuid/seteuid" unless $< == $uid and $> == $uid; # safety check
     }
 
+    # sanitize environment
+    my $term = $ENV{TERM};
+    my @ent = getpwuid($>) or die "getpwuid($>): $!";
+    %ENV = ( USER => $ent[0], LOGNAME => $ent[0], HOME => $ent[7], SHELL => $ent[8] );
+    $ENV{PATH} = $> == 0 ? "/usr/sbin:/usr/bin:/sbin:/bin" : "/usr/bin:/bin";
+    $ENV{TERM} = $term if defined $term; # preserve $TERM
+
     chdir $dir or die "chdir($dir): $!";
 }
 
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