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To my surprise, the postfix package is not setup in a chroot jail by default. For example, in Ubuntu if we use the mail-stack-delivery package, most of postfix is setup in a chroot. Just comparing the two master.cf files shows (snippet):
# ==========================================================================
# service type private unpriv chroot wakeup maxproc command + args
# (yes) (yes) (no) (never) (100)
# ==========================================================================
smtp inet n - n - - smtpd
#smtp inet n - n - 1 postscreen
#smtpd pass - - n - - smtpd
#dnsblog unix - - n - 0 dnsblog
#tlsproxy unix - - n - 0 tlsproxy
#submission inet n - n - - smtpdCompared to Ubuntu's master.cf file:
# ==========================================================================
# service type private unpriv chroot wakeup maxproc command + args
# (yes) (yes) (yes) (never) (100)
# ==========================================================================
smtp inet n - - - - smtpd
#smtp inet n - - - 1 postscreen
#smtpd pass - - - - - smtpd
#dnsblog unix - - - - 0 dnsblog
#tlsproxy unix - - - - 0 tlsproxy
#submission inet n - - - - smtpdThe postfix documentation briefly describes how to setup a chroot. Looking at examples/chroot in the source code of postfix gives us the commands to successfully set up chroot for Linux "tested on SuSE Linux 5.3 (libc5) and 7.0 (glibc2.1)". I'm not a Arch Linux pro yet that I can assess whether these commands can be directly copied to Arch LInux and will lead to a successful chroot.
Could someone help me figure this out? If there is enough interest I'd also like to suggest to add this to the Arch wiki entry for postfix.
For completeness, these are the suggested commands:
#! /bin/sh
# LINUX2 - shell script to set up a Postfix chroot jail for Linux
# Tested on SuSE Linux 5.3 (libc5) and 7.0 (glibc2.1)
# Other testers reported as working:
#
# 2001-01-15 Debian sid (unstable)
# Christian Kurz <shorty@getuid.de>
# Copyright (c) 2000 - 2001 by Matthias Andree
# Redistributable unter the MIT-style license that follows:
# Abstract: "do whatever you want except hold somebody liable or change
# the copyright information".
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to
# deal in the Software without restriction, including without limitation the
# rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
# sell copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
# IN THE SOFTWARE.
# 2000-09-29
# v0.1: initial release
# 2000-12-05
# v0.2: copy libdb.* for libnss_db.so
# remove /etc/localtime in case it's a broken symlink
# restrict find to maxdepth 1 (faster)
# Revision 1.4 2001/01/15 09:36:35 emma
# add note it was successfully tested on Debian sid
#
# 20060101 /lib64 support by Keith Owens.
#
CP="cp -p"
cond_copy() {
# find files as per pattern in $1
# if any, copy to directory $2
dir=`dirname "$1"`
pat=`basename "$1"`
lr=`find "$dir" -maxdepth 1 -name "$pat"`
if test ! -d "$2" ; then exit 1 ; fi
if test "x$lr" != "x" ; then $CP $1 "$2" ; fi
}
set -e
umask 022
POSTFIX_DIR=${POSTFIX_DIR-/var/spool/postfix}
cd ${POSTFIX_DIR}
mkdir -p etc lib usr/lib/zoneinfo
test -d /lib64 && mkdir -p lib64
# find localtime (SuSE 5.3 does not have /etc/localtime)
lt=/etc/localtime
if test ! -f $lt ; then lt=/usr/lib/zoneinfo/localtime ; fi
if test ! -f $lt ; then lt=/usr/share/zoneinfo/localtime ; fi
if test ! -f $lt ; then echo "cannot find localtime" ; exit 1 ; fi
rm -f etc/localtime
# copy localtime and some other system files into the chroot's etc
$CP -f $lt /etc/services /etc/resolv.conf /etc/nsswitch.conf etc
$CP -f /etc/host.conf /etc/hosts /etc/passwd etc
ln -s -f /etc/localtime usr/lib/zoneinfo
# copy required libraries into the chroot
cond_copy '/lib/libnss_*.so*' lib
cond_copy '/lib/libresolv.so*' lib
cond_copy '/lib/libdb.so*' lib
if test -d /lib64; then
cond_copy '/lib64/libnss_*.so*' lib64
cond_copy '/lib64/libresolv.so*' lib64
cond_copy '/lib64/libdb.so*' lib64
fi
postfix reload Offline
I've looked a bit more into the code and by modifying it a bit the required libraries can be copied. Since Arch Linux uses a symlink for /lib to /usr/lib, the last couple of lines of the script have to be changed to search in the /usr/lib directory instead of /lib (or /lib64)
Restarting postfix seems to work, there are no errors, but I'm still not a 100% sure if the chroot jail is fully functional. Is there a method to test this?
The last thing that worries me is the following line on the postfix website:
"Additionally, you almost certainly need to configure syslogd so that it listens on a socket inside the Postfix queue directory.
Examples of syslogd command line options that achieve this for specific systems.
Linux, OpenBSD: syslogd -a /var/spool/postfix/dev/log."
How would I achieve this using journald?
Last edited by pietje_puk (2016-01-27 16:58:12)
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