Re: [Exim] spamassasin HOWTO hits bitbucket!

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Autor: Franz Georg Köhler
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A: exim-users
Assumpte: Re: [Exim] spamassasin HOWTO hits bitbucket!
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On Thu, May 29, 2003 at 09:01:50PM -0500, Kelv <kelv@???> wrote:
>
>> does anyone have a mirror address for the HOWTO at
>>
>> http://dman.ddts.net
>>
>> every google search returns that URL for a spamassassin_exim config, but
>> hte site is down
>
> The WayBackMachine is your friend.
>
> http://web.archive.org/web/20020608070600/http://dman.ddts.net/~dman/config_docs/exim4_spamassassin.html
> http://web.archive.org/web/20020712190948/http://dman.ddts.net/~dman/config_docs/exim3_spamassassin.html


For the archives:

(see attached files)

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[ Converted text/html to text/plain ]

Tackle the SPAM problem with exim[1] and spamassassin[2].

My platform of choice is Debian GNU/Linux[3]; in particular I run a mix of
"woody" and "sid".

This version of this document refers to :
package major version version specifics exim 3 3.33 , 3.34 spamassassin 1.5
2.01 2.11

Note:

I don't use the configuration documented here. I have since upgraded to exim
4. This document remains for those of you who are still using exim3 and wish
to read this.

Step 1 :

Edit /etc/exim/exim.conf to include scanning (filtering) by spamassassin in
the delivery of a message.
In the Transports section add the following (order is irrelevant) :

# Spam Assassin
spamcheck:
    driver = pipe


    command = /usr/sbin/exim -oMr spam-scanned -bS
    transport_filter = /usr/bin/spamc


    bsmtp = all


    home_directory = "/tmp"
    current_directory = "/tmp"


    # must use a privileged user to set $received_protocol on the way back in!
    user = mail
    group = mail


    return_path_add = false


    log_output = true
    return_fail_output = true


    prefix =
    suffix =




Notes :
This pipes the message to exim using the BSMTP (batched SMTP) protocol. This
avoids any nasties with shell metacharacters in addresses. Prior to giving the
message back to itself, exim will filter it through the 'spamc' command. As
the message returns to exim, the "received_protocol" set to "spam-scanned".
The main problems with this setup is that user's can't configure SA for
themselves since SA is run as user 'mail'

Insert the following at the top of the Directors section :

# Spam Assassin
spamcheck_director:

    # do not use this director when verifying a local-part at SMTP-time
    no_verify


    # When to scan a message :
    #   -   it isn't already flagged as spam
    #   -   it isn't already scanned
    #   -   it didn't originate locally (as long as I don't harbor spammers :-))
    condition = "${if and { {!def:h_X-Spam-Flag:} {!eq {$received_protocol}{spam-scanned}} {!eq {$received_protocol}{local}} } {1}{0}}"
    driver = smartuser
    transport = spamcheck



This director is used for any message that

wasn't received from spamassassin (determined by $received_protocol)
wasn't received via a pipe from a local user
isn't already flagged (this is safe because the only flag that is skipped is a
positive flag; spammers can tag their spam for you, but they can't tag it as
being clean).

Step 2:

Edit /etc/default/spamassassin to start 'spamd' at boot time and to not create
user preferences files automatically and not add a "From " header at the top
of the messages. The "From " header will really break your mail because the
"From " header is only for mbox mailboxes.

# Change to one to enable spamd
ENABLED=1
OPTIONS="-F 0"


(this will make sense when you read your copy of the file)

Step 3:

Start spamd as root :

# /etc/init.d/spamassassin start

Note:
Thus far the spam hasn't been dealt with; the messages have only been tagged
as to whether or not it is spam. Users must now decide what they want to do
with messages that have been tagged as spam. I use exim for filtering my mail
into various folders. In my filter file I added the following above the other
sorting rules :

if
    $h_X-Spam-Status: contains "Yes"
        or
    "${if def:h_X-Spam-Flag {def}{undef}}" is "def"
then
    logwrite "    => junk : SPAM"
    save $home/Mail/junk/spam/
    finish
endif



This dumps all messages tagged as spam into their own folder (and mentions it
in my logfile). At my leisure I can then check the messages for any
false-positives. Note that because I skip scanning on messages with an
X-Spam-Flag: header I must check for that in my filter. Otherwise a spammer
could put the X-Spam-Flag: header in but omit the X-Spam-Status: header and
slip past my filter.

If you find this info helpful or confusing or if you have any comments or
questions or if you have any other reason (besides sending spam ;-)), just
drop me a note : dman@???[4].

------------------------------------------------------------------------------

------------------------------------------------------------------------------

Comments from readers:

Here are some comments that readers of this page have sent me. They are
located here because it is not part of my setup, so I can't really vouch for
it, but I think it is good information to share anyways.

------------------------------------------------------------------------------

Couple of things which I do slightly differently (and I think better :-)

1) Put the director that delivers mail with the real- prefix before the spam
check director - this allows false positives to reply to you if they wish,
and therefore ...

2) .. my filter file bounces back a message thusly
========================== exim filter
# Exim Filter

if first_delivery and
   $h_X-Spam-Flag: contains "YES"
then
   logfile /var/log/exim/spamlog
   logwrite "$tod_log From: $h_From: Subject: $h_Subject: \n \t X-Spam-Status: $h_X-Spam-Status: Sender: $sender_address"
   if $h_From: is not ""
   then
      mail to $h_From: subject "Re: Your last message to me"
           expand file /etc/exim/spam-reply.txt
           once /var/log/exim/spamcount
           once_repeat 5d
   endif
   seen finish
endif
================== spam-reply.txt
Your mail with Subject: $h_Subject:
to domain <my_domain> appears to be unsolicited spam.


If you intended to contact a person at that email domain for
legitimate reasons then our apologies. Please would you resend to the
same address but add the prefix "real-" (without the quotes) to the
e-mail address and it will bypass the spam filter.

Thank you

postmaster@<my_domain>
=======================



------------------------------------------------------------------------------

------------------------------------------------------------------------------

You say that your setup has the drawback of users not being able to configure
their own SA's. That can be fixed very easy:

In the transport-filter section specify
transport_filter = /usr/bin/spamc -u ${local_part}

Your comment is wrong, spamc will be run as mail/mail, but since spamd runs as
root, it can drop into user/group, and access the necessary files.



------------------------------------------------------------------------------

Thanks

These people have helped me understand the system and correct some errors and
sup-optimality in the configuration discussed above. This list is by no means
exclusive. If you feel your name should be added here, drop me a line.

Nigel Metheringham
Kevin Fleming
Renee Brown

===References:===
1. http://www.exim.org/
2. http://spamassassin.taint.org/
3. http://www.debian.org/
4. mailto:dman@dman.ddts.net

--
[ Converted text/html to text/plain ]

Tackle the SPAM problem with exim[1] and spamassassin[2].

My platform of choice is Debian GNU/Linux[3]; in particular I run a mix of
"woody" and "sid".

This version of this document refers to :
exim 4 4.01 , 4.04 (not yet packaged) spamassassin 1.5 2.01 2.11 2.20
Other versions may or may not work the same. Usually the software works the
same at least for minor version changes.

Note:

I am not using the configuration documented here. I have since installed Marc
Merlin's sa-exim[4] local_scan() implementation on my system. Even though it
is still relatively new code it has been working quite well for me. This
document remains for those of you who still need/want it.

Step 1 :

Edit /etc/exim/exim.conf to include scanning (filtering) by spamassassin in
the delivery of a message.
In the Transports section add the following (order is insignificant) :

# Spam Assassin
spamcheck:
    driver = pipe
    command = /usr/local/bin/exim4 -oMr spam-scanned -bS
    use_bsmtp = true
    transport_filter = /usr/bin/spamc
    home_directory = "/tmp"
    current_directory = "/tmp"
    # must use a privileged user to set $received_protocol on the way back in!
    user = mail
    group = mail
    log_output = true
    return_fail_output = true
    return_path_add = false
    message_prefix =
    message_suffix =



Notes :
This pipes the message to exim using the BSMTP (batched SMTP) protocol. This
avoids any nasties with shell metacharacters in addresses. Prior to giving the
message back to itself, exim will filter it through the 'spamc' command. As
the message returns to exim, the "received_protocol" set to "spam-scanned".
The main problems with this setup is that user's can't configure SA for
themselves since SA is run as user 'mail'

Insert the following in the Routers section. The order matters. Put it after
any routers that should handle unscanned mail and before any routers that
should handle only scanned mail.

# Spam Assassin
spamcheck_router:
no_verify
check_local_user
# When to scan a message :
# - it isn't already flagged as spam
# - it isn't already scanned
condition = "${if and { {!def:h_X-Spam-Flag:} {!eq {$received_protocol}{spam-scanned}}} {1}{0}}"
driver = accept
transport = spamcheck


This director is used for any message that

wasn't received from spamassassin (determined by $received_protocol)
wasn't received via a pipe from a local user
isn't already flagged (this is safe because the only flag that is skipped is a
positive flag; spammers can tag their spam for you, but they can't tag it as
being clean).

Step 2:

Edit /etc/default/spamassassin to start 'spamd' at boot time and to not create
user preferences files automatically and not add a "From " header at the top
of the messages. The "From " header will really break your mail because the
"From " header is only for mbox mailboxes.

# Change to one to enable spamd
ENABLED=1
OPTIONS="-F 0"


(this will make sense when you read your copy of the file)

Step 3:

Start spamd as root :

# /etc/init.d/spamassassin start

Note:
Thus far the spam hasn't been dealt with; the messages have only been tagged
as to whether or not it is spam. Users must now decide what they want to do
with messages that have been tagged as spam. I use exim for filtering my mail
into various folders. In my filter file I added the following above the other
sorting rules :

if
    $h_X-Spam-Status: contains "Yes"
        or
    "${if def:h_X-Spam-Flag {def}{undef}}" is "def"
then
    logwrite "    => junk : SPAM"
    save $home/Mail/junk/spam/
    finish
endif



This dumps all messages tagged as spam into their own folder (and mentions it
in my logfile). At my leisure I can then check the messages for any
false-positives. Note that because I skip scanning on messages with an
X-Spam-Flag: header I must check for that in my filter. Otherwise a spammer
could put the X-Spam-Flag: header in but omit the X-Spam-Status: header and
slip past my filter.

If you find this info helpful or confusing or if you have any comments or
questions or if you have any other reason (besides sending spam ;-)), just
drop me a note : dman@???[5]. Unfortunately this host has some
connectivity problems at the moment. The address dsh8290@???[6] will work
until I graduate.

------------------------------------------------------------------------------

------------------------------------------------------------------------------

Comments from readers:

Here are some comments that readers of this page have sent me. They are
located here because it is not part of my setup, so I can't really vouch for
it, but I think it is good information to share anyways.
(Note: This comment was given for exim3. I have tweaked it to use correct
exim4 terminology.)

------------------------------------------------------------------------------

Couple of things which I do slightly differently (and I think better :-)

1) Put the router that delivers mail with the real- prefix before the spam
check router - this allows false positives to reply to you if they wish,
and therefore ...

2) .. my filter file bounces back a message thusly
========================== exim filter
# Exim Filter

if first_delivery and
   $h_X-Spam-Flag: contains "YES"
then
   logfile /var/log/exim/spamlog
   logwrite "$tod_log From: $h_From: Subject: $h_Subject: \n \t X-Spam-Status: $h_X-Spam-Status: Sender: $sender_address"
   if $h_From: is not ""
   then
      mail to $h_From: subject "Re: Your last message to me"
           expand file /etc/exim/spam-reply.txt
           once /var/log/exim/spamcount
           once_repeat 5d
   endif
   seen finish
endif
================== spam-reply.txt
Your mail with Subject: $h_Subject:
to domain <my_domain> appears to be unsolicited spam.


If you intended to contact a person at that email domain for
legitimate reasons then our apologies. Please would you resend to the
same address but add the prefix "real-" (without the quotes) to the
e-mail address and it will bypass the spam filter.

Thank you

postmaster@<my_domain>
=======================



------------------------------------------------------------------------------

Thanks

These people have helped me understand the system and correct some errors and
sup-optimality in the configuration discussed above. This list is by no means
exclusive. If you feel your name should be added here, drop me a line.

Nigel Metheringham
Kevin Fleming
Renee Brown

===References:===
1. http://www.exim.org/
2. http://spamassassin.taint.org/
3. http://www.debian.org/
4. http://marc.merlins.org/linux/exim/sa.html
5. mailto:dman@dman.ddts.net
6. mailto:dsh8290@rit.edu

--