Re: [exim] listed at Backscatterer.org

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Szerző: Grant Peel
Dátum:  
Címzett: exim-users
Tárgy: Re: [exim] listed at Backscatterer.org
----- Original Message -----
From: "Ian Eiloart" <iane@???>
To: <exim.ml@???>
Cc: <exim-users@???>
Sent: Monday, June 28, 2010 6:48 AM
Subject: Re: [exim] listed at Backscatterer.org


>
>
> --On 25 June 2010 13:56:12 +0100 Ron White <exim.ml@???> wrote:
>
>> On Fri, 2010-06-25 at 11:28 +0100, Ian Eiloart wrote:
>>> --On 24 June 2010 09:43:40 +0000 Kebba Foon <kebba.foon@???> wrote:
>>>
>>> >
>>> > Backscatterer - Why it is abusive and how to stop your system doing so
>>> >
>>> > Email servers should be configured to provide Non-Delivery Reports
>>> > (bounces) to local users only.
>>> > Unacceptable email from anywhere else should be rejected.
>>> >
>>>
>>> This is silly advice. It should be quite acceptable to bounce email that
>>> has an SPF pass, or that has a valid DKIM signature (provided the return
>>> path domain matches a signed From header domain). In both cases, if
>>> you're creating collateral spam, then that's the fault of the domain
>>> operator.
>>>
>> There is probably a bit of a translation issue there as backscatter.org
>> is part of Dirk & Claus 'UCEProtect' stable of blocklists.
>>
>> My personal opinion is you should never accept mail that you cannot
>> deliver to a user and in such a scenario it should be rejected at SMTP
>> time - not after a 250 is given and (any/the) MTA decides it does not
>> want it for whatever reason. Exim is very flexible and its brilliant
>> ACL's can pretty much reduce backscatter to zero if configured
>> correctly.
>
> Well, the backscatter issue means that we have no choice but to try to do
> that. But that's a bad thing. It would be a much better world in which we
> were able to accept such messages, and then generate a bounce. Why?
> Because
> bounce messages have the potential to be more user-friendly.
>
> I believe that with improved email authentication (SPF, DKIM, etc), we'll
> one day be able to revive the bounce message.
>
>
> --
> Ian Eiloart
> IT Services, University of Sussex
> 01273-873148 x3148
> For new support requests, see http://www.sussex.ac.uk/its/help/
>
>
>
> --
> ## List details at http://lists.exim.org/mailman/listinfo/exim-users
> ## Exim details at http://www.exim.org/
> ## Please use the Wiki with this list - http://wiki.exim.org/
>
>


Hi all,

    I was happy to see someone else start this thread :-)


    I have been researching and tinkering to no avail on the backscatter 
issue. Trying to make sure I am not the source, or the recipient of 
backscatter. backscatterer.org has not helped as occasionally my server have 
been listed.


    I am attaching a copy of my configure script hoping someone might have 
some suggestions as to how to curb/eliminate backscatter.


    My server is a virtual setup, domains listed in /etc/domains, real unix 
user mapped to domains through /etc/domains_users, virtual users (for each 
domain) listed in a password file in /etc/virtual/<domain>/passwd, aliases 
listed in /home/<domain>/mail/aliases. The server is still sending mail 
through the base server name (FQDNS)


    Also, feel free to crituque the whole config:


######################################################################
#                    MAIN CONFIGURATION SETTINGS                     #
######################################################################
primary_hostname = <mydomain>
domainlist relay_to_domains =
domainlist local_domains = /etc/virtual/domains
domainlist filtered_domains = /etc/virtual/filtered_domains
hostlist filtering_hosts = /etc/virtual/filtering_hosts
hostlist relay_from_hosts = /etc/virtual/domains
hostlist blacklisted_domains = /etc/virtual/blacklist
hostlist spf_bypass = /etc/virtual/spf_bypass
hostlist whitelist = /etc/virtual/whitelist
acl_smtp_rcpt = acl_check_rcpt
trusted_users = mailnull:root:webmail:www
exim_user = mailnull
exim_group = mail
never_users =
host_lookup = *
rfc1413_hosts = *
rfc1413_query_timeout = 5s
ignore_bounce_errors_after = 0s
timeout_frozen_after = 0s
auto_thaw = 6h
return_path_remove
untrusted_set_sender = *
helo_allow_chars = _
daemon_smtp_ports = 25 : 109 : 587
bounce_message_file = /usr/local/etc/exim/bounce_message_file
warn_message_file = /usr/local/etc/exim/warn_message_file
return_size_limit = 10000
bounce_return_message = true
bounce_return_size_limit = 1000
delay_warning = 72h
smtp_accept_max = 100
smtp_accept_max_per_host = 10
smtp_return_error_details = yes
log_selector = +incoming_interface +deliver_time +delivery_size 
+received_sender \
+received_recipients +sender_on_delivery +subject +address_rewrite 
+all_parents
# log_selector = +all
message_logs = false



#
# My Attempt at greylisting
#

hide mysql_servers = localhost/exim_db/<exim_db>/<passwd>:

GREYLIST_TEST = SELECT IF(NOW() > block_expires, 2, 1) \
                FROM exim_greylist \
                WHERE relay_ip = '${quote_mysql:$sender_host_address}' \
                AND from_domain = '${quote_mysql:$sender_address_domain}' \
                AND record_expires > NOW()


GREYLIST_ADD  = INSERT INTO exim_greylist \
                SET relay_ip = '${quote_mysql:$sender_host_address}', \
                from_domain = '${quote_mysql:$sender_address_domain}', \
                block_expires = DATE_ADD(NOW(), INTERVAL 1 MINUTE), \
                record_expires = DATE_ADD(NOW(), INTERVAL 14 DAY), \
                origin_type = 'AUTO', \
                create_time = NOW()


GREYLIST_UPDATE = UPDATE exim_greylist \
                SET record_expires = DATE_ADD(now(), INTERVAL 14 DAY) \
                WHERE relay_ip = '${quote_mysql:$sender_host_address}' \
                AND from_domain = '${quote_mysql:$sender_address_domain}' \
                AND record_expires > NOW()


######################################################################
#                       ACL CONFIGURATION                            #
#         Specifies access control lists for incoming SMTP mail      #
######################################################################


begin acl

acl_check_rcpt:

        accept  hosts           = :
                logwrite        = ACL - ACCEPTED (EMPTY LIST)
        deny    local_parts     = ^.*[@%!/|] : ^\\.
                log_message     = ACL - DENIED (LOCAL PART SYNTAX)
        accept  authenticated   = *
                logwrite        = ACL - ACCEPTED (AUTHENTICATED)
                endpass
        accept  hosts           = +relay_from_hosts
                logwrite        = ACL - ACCEPTED (RELAY FROM HOST LIST)
                endpass


######################################################################
# Hello checks added November 1 2009.
######################################################################

# If the remote host greets with an IP address, then reject the mail.
        deny    message         = RATWARE - IP address.
                log_message     = ACL - DENIED - RATWARE remote host used IP 
address \
                                in HELO/EHLOgreeting
                condition       = ${if isip 
{$sender_helo_name}{true}{false}}


# Likewise if the peer greets with one of our own names
        deny    message         = RATWARE - Fake HELO Domain
                log_message     = ACL - DENIED - RATWARE remote host used 
our name in \
                                HELO/EHLO greeting.
                condition       = ${if match_domain{$sender_helo_name}\
                                {$primary_hostname:+local_domains:+relay_to_domains}\
                                {true}{false}}
        deny    message         = RATWARE - No HELO
                log_message     = ACL - DENIED - RATWARE remote host did not 
present \
                                HELO/EHLO greeting.
                condition       = ${if def:sender_helo_name {false}{true}}


# If HELO verification fails, we add a X-HELO-Warning: header in the 
message.
        warn    message         = X-HELO-Warning: Remote host 
$sender_host_address \
                                ${if def:sender_host_name 
{($sender_host_name) }}\
                                incorrectly presented itself as 
$sender_helo_name
                log_message     = ACL - WARN - UNVERIFIABLE HELO/EHLO 
greeting.
                !verify         = helo


#######################################################################
# Mail is being rejected on some hosts because the mail MX is only set to 
Reflexion
# and our server is rejecting it because some mail servers see the lesser 
priorty
# MX and try to oour server directly instead of going though Reflexion.
# UPDATE: All secondary MXs removed from DNS zones. Reenabled monday Oct 5 
2009.
        accept  domains         = +filtered_domains
                hosts           = +filtering_hosts
                verify          = recipient
                log_message     = ACL - ACCEPTED - MXTEXT
        deny    message         = Please use the public MX server for the 
domain $domain
                domains         = +filtered_domains
                hosts           = !+filtering_hosts
                log_message     = ACL - DENIED - MXTEST
######################################################################


######################################################################
# DNS checks
######################################################################
# The results of these checks are cached, so multiple recipients
# does not translate into multiple DNS lookups.
#
# If the connecting host is in one of a select few DNSbls, then
# reject the message.  Be careful when selecting these lists; many
# would cause a large number of false postives, and/or have no
# clear removal policy.
#
#       deny    dnslists        = dnsbl.sorbs.net : \
#               dnsbl.njabl.org : \
#               cbl.abuseat.org : \
#               bl.spamcop.net
#               message         = RBL - $sender_host_address is listed in 
$dnslist_domain\
#                               ${if def:dnslist_text { ($dnslist_text)}}
#####################################################################


        deny    senders         = :
                condition       = ${if > {$recipients_count}{2}{1}}
                message         = Bounces must have only a single recipient
                log_message     = ACL - DENIED - BACKSCATTER - RECIPIENTS 
$recipients_count
        deny    message         = rejected because $sender_host_address was 
\
                                found in our blacklist
                hosts           = +blacklisted_domains
                log_message     = ACL - DENIED - BLACKLISTED DOMAIN FOUND IN 
$blacklisted_domains
        deny
                ! condition    = ${lookup 
dnsdb{defer_never,ptr=$sender_host_address}{yes}}
                log_message    = ACL - DENIED - NO PTR [rDNS] FOUND FOR 
$sender_host_address
                message        = We do not accept mail from hosts with 
missing \
                                or incorrect rDNS.
        deny    senders         = :
                ! hosts         = +whitelist
                ! domains       = +local_domains
                dnslists        = ips.backscatterer.org
                message         = This message looks like a bounce, and your 
server is listed at \
                                ips.backscatterer.org, so I assume that this 
is "backscatter". \
                                Please configure your mail server to not 
send "backscatter \                                     spam". \
                                For advice, try 
http://www.dontbouncespam.org/
                log_message     = ACL - DENIED - BACKSCATTER - INCOMING
        warn    set acl_m2      = ${lookup mysql{GREYLIST_TEST}{$value}{0}}
        defer   ! hosts         = +whitelist
                ! hosts         = +relay_from_hosts
                ! authenticated = *
                condition       = ${if eq{$acl_m2}{0}{yes}}
                condition       = ${lookup mysql{GREYLIST_ADD}{yes}{no}}
                message         = Now greylisted - please try again in 1 
minute.
                log_message     = ACL - DEFERED - ADDING TO GREYLIST
        defer   ! hosts         = +whitelist
                ! hosts         = +relay_from_hosts
                ! authenticated = *
                condition       = ${if eq{$acl_m2}{1}{yes}}
                message         = Still greylisted - please try again in 1 
minute.
                log_message     = ACL - DEFERED - STILL GREYLISTED
        defer
                ! hosts         = +whitelist
                ! hosts         = +relay_from_hosts
                ! authenticated = *
                condition       = ${lookup mysql{GREYLIST_UPDATE}{no}{no}}
                message         = Greylist update failed
                log_message     = ACL - DEFERED - GREYLIST UPDATE FAILED
        require verify          = sender
        accept  hosts           = +spf_bypass
                spf             = fail
                logwrite        = SPF - REFLEXION $sender_host_address is OK 
for \
                                $sender_address_domain
        deny    message         = SPF - INCOMING $sender_host_address \
                                is not allowed to send mail from 
$sender_address_domain
                spf             = fail
                log_message     = ACL - DENIED - SPF Mismatch
        accept  domains         = +local_domains
                endpass
                message         = unknown user
                verify          = recipient
        accept  domains         = +relay_to_domains
                endpass
                message         = unrouteable address
                verify          = recipient


######################################################################
#                      ROUTERS CONFIGURATION                         #
#               Specifies how addresses are handled                  #
######################################################################
#     THE ORDER IN WHICH THE ROUTERS ARE DEFINED IS IMPORTANT!       #
# An address is passed to each router in turn until it is accepted.  #
######################################################################


begin routers

dnslookup_owm_www:
driver = dnslookup
domains = ! +local_domains
condition = ${if eq {$sender_host_address}{127.0.0.1} {yes}{no}}
transport = remote_smtp
ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
no_more

dnslookup_local:
driver = dnslookup
domains = ! +local_domains
condition = ${lookup {$sender_address_domain} lsearch
{/etc/virtual/domains} {yes}{no}}
transport = remote_smtp
ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
no_more

dnslookup_bounce:
driver = dnslookup
domains = ! +local_domains
condition = ${if eq {$sender_address_local_part}{} {yes}{no}}
transport = remote_smtp
ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
no_more

dnslookup_alias:
driver = dnslookup
domains = ! +local_domains
transport = remote_smtp
ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
no_more

spamcheck_router:
driver = accept
no_verify
condition = "${if and { {!def:h_X-Spam-Flag:} {!eq {$received_protocol}\
{spam-scanned}}} {1}{0}}"
transport = spamcheck

virtual_alias:
driver = redirect
allow_defer
allow_fail
data = ${lookup {$local_part} lsearch {/home/$domain/mail/aliases}}
domains = /etc/virtual/domains
require_files = /home/$domain/mail/aliases
condition = ${lookup {$local_part} lsearch {/home/$domain/mail/aliases}
{yes}{no}}
qualify_preserve_domain
retry_use_local_part
check_ancestor
one_time
file_transport = address_file
pipe_transport = address_pipe
reply_transport = address_reply

autoreply_router:
driver = accept
require_files = /home/$domain/mail/auto-replies/$local_part
transport = autoreply_transport
no_verify
unseen

virtual_localuser:
driver = accept
require_files = /etc/virtual/$domain/passwd
domains = /etc/virtual/domains
condition = ${lookup {$local_part} lsearch
{/etc/virtual/$domain/passwd}{$value}}
transport = virtual_localdelivery

virtual_catchall:
driver = redirect
allow_defer
allow_fail
data = ${lookup {catchall} lsearch {/home/$domain/mail/aliases}}
domains = /etc/virtual/domains
require_files = /home/$domain/mail/aliases
condition = ${lookup {catchall}lsearch{/home/$domain/mail/aliases}
{yes}{no}}
qualify_preserve_domain
retry_use_local_part
check_ancestor
one_time
file_transport = address_file
pipe_transport = address_pipe
reply_transport = address_reply

localuser:
driver = accept
check_local_user
condition = ${lookup {$sender_helo_name} lsearch
{/etc/virtual/domains}{YES}{NO}}
transport = local_delivery

######################################################################
#                      TRANSPORTS CONFIGURATION                      #
######################################################################
#                       ORDER DOES NOT MATTER                        #
#     Only one appropriate transport is called for each delivery.    #
######################################################################
begin transports


remote_smtp:
        driver = smtp
        return_path_add = true


autoreply_transport:
driver = pipe
command = /usr/local/bin/autoreply.pl
/home/$domain/mail/auto-replies/$local_part

spamcheck:
driver = pipe
command = /usr/local/sbin/exim -oMr spam-scanned -bS
use_bsmtp = true
transport_filter = /usr/local/bin/spamc -u
${lookup{$domain}lsearch{/etc/virtual/domains_users}}
home_directory = "/tmp"
current_directory = "/tmp"
# must use a privileged user to set $received_protocol on the way back in!
user = mailnull
group = mailnull
log_output = true
return_fail_output = false
return_path_add
message_prefix =
message_suffix =

virtual_localdelivery:
driver = appendfile
create_directory = true
directory_mode = 700
file = /var/spool/virtual/${domain}/${local_part}
headers_remove = "Bcc"
return_path_add
user = ${lookup{$domain}lsearch{/etc/virtual/domains_users}}
group = mail
mode = 660

local_delivery:
driver = appendfile
file = /$home/mail/$local_part
delivery_date_add
envelope_to_add
return_path_add
user = mailnull
group = mail
mode = 0660

address_pipe:
driver = pipe
return_output
user = <user>

address_file:
driver = appendfile
delivery_date_add
envelope_to_add
return_path_add

address_reply:
driver = autoreply

######################################################################
#                      RETRY CONFIGURATION                           #
######################################################################


begin retry

# Domain               Error       Retries
# ------               -----       -------
*                      quota_7d
*                      quota       F,72h,1h;
*                      *           F,30m,1m; F,90m,5m; F,22h,30m; F,144h,60m


######################################################################
#                      REWRITE CONFIGURATION                         #
######################################################################


# There are no rewriting specifications in this default configuration file.

begin rewrite

######################################################################
#                   AUTHENTICATION CONFIGURATION                     #
######################################################################


# There are no authenticator specifications in this default configuration
file.

begin authenticators

# For Netscape/Mozilla
plain:
  driver = plaintext
  public_name = PLAIN
  server_condition = "${if and{ {!eq{$2}{}}{!eq{$3}{}} \
   {crypteq {$3} {${lookup {${local_part:$2}} lsearch \
                            {/etc/virtual/${domain:$2}/passwd}\
                            {$value} {*:*}}}} } {1}{0}}"
  server_set_id = $2


# For Outlook/Outlook Express
login:
  driver = plaintext
  public_name = LOGIN
  server_prompts = "Username:: : Password::"
  server_condition = "${if and{ {!eq{$1}{}}{!eq{$2}{}} \
   {crypteq {$2} {${lookup {${local_part:$1}} lsearch \
                            {/etc/virtual/${domain:$1}/passwd}\
                            {$value} {*:*}}}} } {1}{0}}"
  server_set_id = $1


# End of Exim configuration file