Amavis

Amavis ist ein Content-Filter für Mailserver (z. B. Postfix). Amavis kann in Verbindung mit einem Antiviren-Programm (z. B. ClamAV) eingehende eMails automatisch überprüfen und entsprechend markieren. So kann z. B. jede SPAM-Mail mit einem Sternchen(*) im Betreff gekennzeichnet werden oder mit Hilfe von serverbasierten Filterregeln in einen Spam-Ordner verschoben werden.

Installation

Damit die Inhaltüberprüfung funktioniert, müssen folgende Pakete installiert werden:

• amavisd-new
• spamassassin
• clamav-daemon
• lha
• arj
• unrar
• zoo
• nomarch
• cpio
• lzop
• cabextract

Auf einem apt-get-basierenden System (z. B. Ubuntu) kann dies mit folgenden Befehlen erfolgen:

user@localhost:~# apt-get install amavisd-new spamassassin clamav-daemon lha arj unrar zoo nomarch cpio lzop cabextract

Amavis konfigurieren

Nun muss man die #50-user-Datei im Ordner /etc/amavis/conf.d/ anpassen. Hierfür kann auch das Beispiel aus diesem Wiki verwendet werden. Wenn man SPAM-Emails im Betreff mit "***** SPAM *****" kennzeichnen möchte, muss man den $sa_spam_subject_tag anpassen, z. B.

$sa_spam_subject_tag = '***** SPAM *****';

Im nächsten Step wird der Content-Filter scharf geschaltet, indem @bypass_virus_checks_maps und @bypass_spam_checks_maps in der Datei #15-content_filter_modeeinkommentiert werden:

user@localhost:~# vim /etc/amavis/conf.d/15-content_filter_mode

 @bypass_virus_checks_maps = (
   \%bypass_virus_checks, \@bypass_virus_checks_acl, \$bypass_virus_checks_re);

 @bypass_spam_checks_maps = (
   \%bypass_spam_checks, \@bypass_spam_checks_acl, \$bypass_spam_checks_re);

Jetzt muss man clamav noch der Gruppe amavis hinzufügen:

adduser clamav amavis

Postfix anpassen

So, Amavis ist nun bereit. Jetzt muss Postfix ihn nur noch verwenden. Hierfür muss die main.cf und die master.cf erweitert werden. Die main.cf kann mit folgenden Befehlen angepasst werden:

user@localhost:~# postconf -e content_filter=smtp-amavis:[127.0.0.1]:10024

user@localhost:~# postconf -e receive_override_options=no_address_mappings

Die #master.cf in /etc/postfix/master.cf muss manuell mit einem Editor bearbeitet werden. Folgenden Block oben einfügen:

 smtp-amavis unix -      -       n       -       2       smtp
    -o smtp_data_done_timeout=1200
    -o smtp_send_xforward_command=yes
    -o disable_dns_lookups=yes
    -o max_use=20

 127.0.0.1:10025 inet n  -       -     -       -  smtpd
    -o content_filter=
    -o local_recipient_maps=
    -o relay_recipient_maps=
    -o smtpd_restriction_classes=
    -o smtpd_delay_reject=no
    -o smtpd_client_restrictions=permit_mynetworks,reject
    -o smtpd_helo_restrictions=
    -o smtpd_sender_restrictions=
    -o smtpd_recipient_restrictions=permit_mynetworks,reject
    -o smtpd_data_restrictions=reject_unauth_pipelining
    -o smtpd_end_of_data_restrictions=
    -o mynetworks=127.0.0.0/8,46.4.175.32/28,192.168.100.10/24
    -o smtpd_error_sleep_time=0
    -o smtpd_soft_error_limit=1001
    -o smtpd_hard_error_limit=1000
    -o smtpd_client_connection_count_limit=0
    -o smtpd_client_connection_rate_limit=0
    -o receive_override_options=no_header_body_checks,no_unknown_recipient_checks
    -o local_header_rewrite_clients=

Und ganz unten folgenden Block erweitern:

 dovecot   unix  -       n       n       -       -       pipe
    flags=DRhu user=vmail:vmail argv=/usr/lib/dovecot/deliver -d ${recipient}

Anschließend Postfix neustarten

user@localhost:~# service postfix restart

und Content-Filter testen:

sendmail user@beispiel.de < /usr/share/doc/spamassassin/examples/sample-spam.txt

Anhang

50-user

 use strict;

#
# Place your configuration directives here.  They will override those in
# earlier files.
#
# See /usr/share/doc/amavisd-new/ for documentation and examples of
# the directives you can use in this file
#

$sa_spam_subject_tag = undef;
$spam_quarantine_to  = undef;
$sa_tag_level_deflt  = undef;
$final_spam_destiny  = D_PASS;

@lookup_sql_dsn = (
    ['DBI:mysql:database=postfix;host=127.0.0.1;port=3306',
     'postfix',
     'secret']);

$sql_select_policy = 'SELECT domain FROM domain WHERE CONCAT("@",domain) IN (%k)';


#------------ Do not modify anything below this line -------------
1;  # ensure a defined return

15-content_filter_mode

use strict;

# You can modify this file to re-enable SPAM checking through spamassassin
# and to re-enable antivirus checking.

#
# Default antivirus checking mode
# Please note, that anti-virus checking is DISABLED by 
# default.
# If You wish to enable it, please uncomment the following lines:


@bypass_virus_checks_maps = (
   \%bypass_virus_checks, \@bypass_virus_checks_acl, \$bypass_virus_checks_re);


#
# Default SPAM checking mode
# Please note, that anti-spam checking is DISABLED by 
# default.
# If You wish to enable it, please uncomment the following lines:


@bypass_spam_checks_maps = (
   \%bypass_spam_checks, \@bypass_spam_checks_acl, \$bypass_spam_checks_re);

1;  # ensure a defined return

master.cf

#
# Postfix master process configuration file.  For details on the format
# of the file, see the master(5) manual page (command: "man 5 master").
#
# Do not forget to execute "postfix reload" after editing this file.
#
# ==========================================================================
# service type  private unpriv  chroot  wakeup  maxproc command + args
#               (yes)   (yes)   (yes)   (never) (100)
# ==========================================================================
smtp      inet  n       -       -       -       -       smtpd

smtp-amavis unix -      -       n       -       2       smtp
    -o smtp_data_done_timeout=1200
    -o smtp_send_xforward_command=yes
    -o disable_dns_lookups=yes
    -o max_use=20

127.0.0.1:10025 inet n  -       -     -       -  smtpd
    -o content_filter=
    -o local_recipient_maps=
    -o relay_recipient_maps=
    -o smtpd_restriction_classes=
    -o smtpd_delay_reject=no
    -o smtpd_client_restrictions=permit_mynetworks,reject
    -o smtpd_helo_restrictions=
    -o smtpd_sender_restrictions=
    -o smtpd_recipient_restrictions=permit_mynetworks,reject
    -o smtpd_data_restrictions=reject_unauth_pipelining
    -o smtpd_end_of_data_restrictions=
    -o mynetworks=127.0.0.0/8,46.4.175.32/28,192.168.100.10/24
    -o smtpd_error_sleep_time=0
    -o smtpd_soft_error_limit=1001
    -o smtpd_hard_error_limit=1000
    -o smtpd_client_connection_count_limit=0
    -o smtpd_client_connection_rate_limit=0
    -o receive_override_options=no_header_body_checks,no_unknown_recipient_checks
    -o local_header_rewrite_clients=

#submission inet n       -       -       -       -       smtpd
#  -o smtpd_tls_security_level=encrypt
#  -o smtpd_sasl_auth_enable=yes
#  -o smtpd_client_restrictions=permit_sasl_authenticated,reject
#  -o milter_macro_daemon_name=ORIGINATING
#smtps     inet  n       -       -       -       -       smtpd
#  -o smtpd_tls_wrappermode=yes
#  -o smtpd_sasl_auth_enable=yes
#  -o smtpd_client_restrictions=permit_sasl_authenticated,reject
#  -o milter_macro_daemon_name=ORIGINATING
#628       inet  n       -       -       -       -       qmqpd
pickup    fifo  n       -       -       60      1       pickup
cleanup   unix  n       -       -       -       0       cleanup
qmgr      fifo  n       -       n       300     1       qmgr
#qmgr     fifo  n       -       -       300     1       oqmgr
tlsmgr    unix  -       -       -       1000?   1       tlsmgr
rewrite   unix  -       -       -       -       -       trivial-rewrite
bounce    unix  -       -       -       -       0       bounce
defer     unix  -       -       -       -       0       bounce
trace     unix  -       -       -       -       0       bounce
verify    unix  -       -       -       -       1       verify
flush     unix  n       -       -       1000?   0       flush
proxymap  unix  -       -       n       -       -       proxymap
proxywrite unix -       -       n       -       1       proxymap
smtp      unix  -       -       -       -       -       smtp
# When relaying mail as backup MX, disable fallback_relay to avoid MX loops
relay     unix  -       -       -       -       -       smtp
        -o smtp_fallback_relay=
#       -o smtp_helo_timeout=5 -o smtp_connect_timeout=5
showq     unix  n       -       -       -       -       showq
error     unix  -       -       -       -       -       error
retry     unix  -       -       -       -       -       error
discard   unix  -       -       -       -       -       discard
local     unix  -       n       n       -       -       local
virtual   unix  -       n       n       -       -       virtual
lmtp      unix  -       -       -       -       -       lmtp
anvil     unix  -       -       -       -       1       anvil
scache    unix  -       -       -       -       1       scache
#
# ====================================================================
# Interfaces to non-Postfix software. Be sure to examine the manual
# pages of the non-Postfix software to find out what options it wants.
#
# Many of the following services use the Postfix pipe(8) delivery
# agent.  See the pipe(8) man page for information about ${recipient}
# and other message envelope options.
# ====================================================================
#
# maildrop. See the Postfix MAILDROP_README file for details.
# Also specify in main.cf: maildrop_destination_recipient_limit=1
#
maildrop  unix  -       n       n       -       -       pipe
  flags=DRhu user=vmail argv=/usr/bin/maildrop -d ${recipient}
#
# ====================================================================
#
# Recent Cyrus versions can use the existing "lmtp" master.cf entry.
#
# Specify in cyrus.conf:
#   lmtp    cmd="lmtpd -a" listen="localhost:lmtp" proto=tcp4
#
# Specify in main.cf one or more of the following:
#  mailbox_transport = lmtp:inet:localhost
#  virtual_transport = lmtp:inet:localhost
#
# ====================================================================
#
# Cyrus 2.1.5 (Amos Gouaux)
# Also specify in main.cf: cyrus_destination_recipient_limit=1
#
#cyrus     unix  -       n       n       -       -       pipe
#  user=cyrus argv=/cyrus/bin/deliver -e -r ${sender} -m ${extension} ${user}
#
# ====================================================================
# Old example of delivery via Cyrus.
#
#old-cyrus unix  -       n       n       -       -       pipe
#  flags=R user=cyrus argv=/cyrus/bin/deliver -e -m ${extension} ${user}
#
# ====================================================================
#
# See the Postfix UUCP_README file for configuration details.
#
uucp      unix  -       n       n       -       -       pipe
  flags=Fqhu user=uucp argv=uux -r -n -z -a$sender - $nexthop!rmail ($recipient)
#
# Other external delivery methods.
#
ifmail    unix  -       n       n       -       -       pipe
  flags=F user=ftn argv=/usr/lib/ifmail/ifmail -r $nexthop ($recipient)
bsmtp     unix  -       n       n       -       -       pipe
  flags=Fq. user=bsmtp argv=/usr/lib/bsmtp/bsmtp -t$nexthop -f$sender $recipient
scalemail-backend unix  -       n       n       -       2       pipe
  flags=R user=scalemail argv=/usr/lib/scalemail/bin/scalemail-store ${nexthop} ${user} ${extension}
mailman   unix  -       n       n       -       -       pipe
  flags=FR user=list argv=/usr/lib/mailman/bin/postfix-to-mailman.py
  ${nexthop} ${user}
dovecot   unix  -       n       n       -       -       pipe
    flags=DRhu user=vmail:vmail argv=/usr/lib/dovecot/deliver -d ${recipient}