postfwd - postfix firewall daemon

NAME SYNOPSIS DESCRIPTION INTRODUCTION CONFIGURATION ITEMS FILES ACTIONS MACROS/ACLS DYNAMIC GROUPS PLUGINS COMMAND LINE REFRESH EXAMPLES PARSER SETTINGS DEBUGGING INTEGRATION TESTING PERFORMANCE SEE ALSO DONATIONS LICENSE AUTHOR

SYNOPSIS

postfwd3 [ OPTIONS ] [ COMMAND ]

postfwd3 [ OPTIONS ] −−cmd [ SOURCE1, SOURCE2, ... ]

Ruleset: (at least one, multiple use is allowed):
−f, −−file <file> reads rules from <file>
−r, −−rule <rule> adds <rule> to config
−s, −−scores <v>=<r> returns <r> when score exceeds <v>
Settings: (multiple use allowed)
−F, −−loadsettings <file> loads program settings from <file>
−−savesettings <file> saves program settings to <file>
−−showsettings exports program settings to stdout
Server:
−i, −−interface <dev> listen on interface <dev>
−p, −−port <port> listen on port <port>
−−proto <proto> socket type (tcp or unix)
−−server_socket <sock> e.g. tcp:127.0.0.1:10045
−u, −−user <name> set uid to user <name>
−g, −−group <name> set gid to group <name>
−−umask <mask> umask for master filepermissions
−−server_umask <mask> umask for server filepermissions
−−pidfile <path> create pidfile under <path>
−−min_servers spawn at least children
−−max_servers do not spawn more than children
−−min_spare_servers minimum idle children
−−max_spare_servers maximum idle children
Cache:
−c, −−cache <int> sets the request−cache timeout to <int> seconds
−−cleanup−requests <int> cleanup interval in seconds for request cache
−−cache_interface <dev> listen on interface <dev>
−−cache_port <port> listen on port <port>
−−cache_proto <proto> socket type (tcp or unix)
−−cache_socket <sock> e.g. tcp:127.0.0.1:10043
−−cache_umask <mask> umask for cache filepermissions
−−cacheid <list> list of request items for cache−id
−−cacheid_md5 cacheid => md5sum(request)
−−cache−rdomain−only skip recipient localpart for cache−id
−−cache−no−sender skip sender address for cache−id
−−cache−no−size skip size for cache−id
−−no_parent_request_cache disable parent request cache
−−no_parent_rate_cache disable parent rate cache
−−no_parent_dns_cache disable parent dns cache (default)
−−no_parent_group_cache disable parent group cache
−−no_parent_cache disable all parent caches
Groups:
−−default_group_ttl default group TTL
−−group_maxitems max items per group
−−cleanup−groups <int> cleanup interval in seconds for group objects
Rates:
−−cleanup−rates <int> cleanup interval in seconds for rate cache
Control:
−k, −−kill, −−stop terminate postfwd3
−−reload, −−hup reload postfwd3
−−watchdog <w> watchdog timer in seconds
−−respawn <r> respawn delay in seconds
−−failures <f> max respawn failure counter
−d, −−daemon execute program in background
−−nodaemon execute program in foreground
−−daemons <list> list of daemons to start
−−personality <type> type of policy server, allows 'PreFork' or 'Multiplex'
−−autopersonality determine personality by program name (see manpage)
−−noautopersonality don't do it (see above :)
−−v1 set personality to 'Multiplex'
−−v2 set personality to 'PreFork'
−−dumpcache show cache contents
−−dumpstats show statistics
−R, −−chroot <path> chroot to <path> before start
−−delcache <item> removes an item from the request cache
−−delrate <item> removes an item from the rate cache
DNS:
−n, −−nodns skip any dns based test
−−dns_timeout dns query timeout in seconds
−−dns_timeout_max disable dnsbl after timeouts
−−dns_timeout_interval reenable dnsbl after seconds
−−cache−rbl−timeout default dns ttl if not specified in ruleset
−−cache−rbl−default <s> default dns pattern if not specified in ruleset
−−cleanup−rbls cleanup old dns cache items every seconds
−−dns_async_txt perform dnsbl A and TXT lookups simultaneously
−−dns_max_ns_lookups max names to look up with sender_ns_addrs
−−dns_max_mx_lookups max names to look up with sender_mx_addrs
−−ipv6_dnsbl enables dnsbl checks for IPv6 addresses
Optional:
−t, −−test testing, always returns "dunno"
−S, −−summary show stats every seconds
−−noidlestats disables statistics when idle
−−norulestats disables per rule statistics
−I, −−instantcfg reloads ruleset on every new request
−−config_timeout parser timeout in seconds
−−keep_groups do not clear group cache on reload
−−save_groups <file> save and load group cache on disk
−−keep_rates do not clear rate limit counters on reload
−−save_rates <file> save and load rate limits on disk
−A, −−aggregate_addrs pre−compute ip address lists to subnets
−−no_netaddr don't use NetAddr::IP functions
−−no_netcidr don't use Net::CIDR::Lite functions
−−cidr_method=s use method <s> for network checks
Plugins:
−−plugins <file> loads postfwd plugins from file
Logging:
−l, −−logname <label> label for syslog messages
−−facility <s> use syslog facility <s>
−−socktype <s> use syslog socktype <s>
−−nodnslog do not log dns results
−−anydnslog log any dns (even cached) results
−−norulelog do not log rule actions
−−nolog|−−perfmon no logging at all
−v, −−verbose verbose logging, use twice to increase
−−debug <s> list of debugging classes
−−debugclasses shows all available debug classes
and exits the program
Information (use only at command−line!):
−h, −−help display this help and exit
−m, −−manual shows program manual
−V, −−version output version information and exit
−D, −−defaults show postfwd3 settings and exit
−C, −−showconfig show postfwd3 ruleset and exit (−v allowed)
−L, −−stdout redirect syslog messages to stdout (−−stdoutlog works for compatibility)
−−stdin pull request from stdin instead of a network socket
−−cmd shorthand form of −−stdin, −−stdout and −−nodaemon
−q, −−quiet no syslogging, no stdout (−P works for compatibility)
Commands:
start start the program [default]
stop same as −−stop
reload same as −−reload
dumpcache same as −−dumpcache
dumpstats same as −−dumpstats
defaults same as −−defaults
showsettings same as −−showsettings
delcache <item> same as −−delcache <item>
delrate <item> same as −−delrate <item>
Obsolete (only for compatibility with postfwd v1):
−−shortlog, −−dns_queuesize, −−dns_retries

DESCRIPTION

INTRODUCTION

postfwd3 is written to combine complex postfix restrictions in a ruleset similar to those of the most firewalls. The program uses the postfix policy delegation protocol to control access to the mail system before a message has been accepted (please visit <http://www.postfix.org/SMTPD_POLICY_README.html> for more information).

postfwd3 allows you to choose an action (e.g. reject, dunno) for a combination of several smtp parameters (like sender and recipient address, size or the client’s TLS fingerprint). Also it offers simple macros/acls which should allow straightforward and easy-to-read configurations.

Features:

* Complex combinations of smtp parameters

* Combined RBL/RHSBL lookups with arbitrary actions depending on results

* Scoring system

* Date/time based rules

* Macros/ACLs, Dynamic groups, Negation

* Compare request attributes (e.g. client_name and helo_name)

* Internal caching for requests and dns lookups

* Built in statistics for rule efficiency analysis

CONFIGURATION

A configuration line consists of optional item=value pairs, separated by semicolons (‘;‘) and the appropriate desired action:

[ <item1>=<value>; <item2>=<value>; ... ] action=<result>

Example:

client_address=192.168.1.1 ; [email protected] ; action=REJECT

This will deny all mail from 192.168.1.1 with envelope sender [email protected]. The order of the elements is not important. So the following would lead to the same result as the previous example:

action=REJECT ; client_address=192.168.1.1 ; [email protected]

The way how request items are compared to the ruleset can be influenced in the following way:

====================================================================
ITEM == VALUE true if ITEM equals VALUE
ITEM => VALUE true if ITEM >= VALUE
ITEM =< VALUE true if ITEM <= VALUE
ITEM > VALUE true if ITEM > VALUE
ITEM < VALUE true if ITEM < VALUE
ITEM =˜ VALUE true if ITEM ˜= /ˆVALUE$/i
ITEM != VALUE false if ITEM equals VALUE
ITEM !> VALUE false if ITEM >= VALUE
ITEM !< VALUE false if ITEM <= VALUE
ITEM !˜ VALUE false if ITEM ˜= /ˆVALUE$/i
ITEM = VALUE default behaviour (see ITEMS section)
====================================================================

To identify single rules in your log files, you may add an unique identifier for each of it:

id=R_001 ; action=REJECT ; client_address=192.168.1.1 ; [email protected]

You may use these identifiers as target for the ‘jump()‘ command (see ACTIONS section below). Leading or trailing whitespace characters will be ignored. Use ’#’ to comment your configuration. Others will appreciate.

A ruleset consists of one or multiple rules, which can be loaded from files or passed as command line arguments. Please see the COMMAND LINE section below for more information on this topic.

Since postfwd version 1.30 rules spanning span multiple lines can be defined by prefixing the following lines with one or multiple whitespace characters (or ’}’ for macros):

id=RULE001
client_address=192.168.1.0/24
[email protected]
action=REJECT no access

postfwd versions prior to 1.30 require trailing ’;’ and ’\’−characters:

id=RULE001; \
client_address=192.168.1.0/24; \
[email protected]; \
action=REJECT no access

ITEMS

id − a unique rule id, which can be used for log analysis
ids also serve as targets for the "jump" command.
date, time − a time or date range within the specified rule shall hit
# FORMAT:
# Feb, 29th
date=29.02.2008
# Dec, 24th − 26th
date=24.12.2008−26.12.2008
# from today until Nov, 23rd
date=−23.09.2008
# from April, 1st until today
date=01.04.2008−
days, months − a range of weekdays (Sun−Sat) or months (Jan−Dec)
within the specified rule shall hit
score − when the specified score is hit (see ACTIONS section)
the specified action will be returned to postfix
scores are set global until redefined!
request_score − this value allows to access a request's score. it
may be used as variable ($$request_score).
rbl, rhsbl, − query the specified RBLs/RHSBLs, possible values are:
rhsbl_client, <name>[/<reply>/<maxcache>, <name>/<reply>/<maxcache>]
rhsbl_sender, (defaults: reply=ˆ127\.0\.0\.\d+$ maxcache=3600)
rhsbl_reverse_client the results of all rhsbl_* queries will be combined
in rhsbl_count (see below).
rblcount, rhsblcount − minimum RBL/RHSBL hitcounts to match. if not specified
a single RBL/RHSBL hit will match the rbl/rhsbl items.
you may specify 'all' to evaluate all items, and use
it as variable in an action (see ACTIONS section)
(default: 1)
sender_localpart, − the local−/domainpart of the sender address
sender_domain
recipient_localpart, − the local−/domainpart of the recipient address
recipient_domain
helo_address − postfwd3 tries to look up the helo_name. use
helo_address=!!(0.0.0.0/0) to check for unknown.
Please do not use this for positive access control
(whitelisting), as it might be forged.
sender_ns_names, − postfwd3 tries to look up the names/ip addresses
sender_ns_addrs of the nameservers for the sender domain part.
Please do not use this for positive access control
(whitelisting), as it might be forged.
sender_mx_names, − postfwd3 tries to look up the names/ip addresses
sender_mx_addrs of the mx records for the sender domain part.
Please do not use this for positive access control
(whitelisting), as it might be forged.
version − postfwd3 version, contains "postfwd3 n.nn"
this enables version based checks in your rulesets
(e.g. for migration). works with old versions too,
because a non−existing item always returns false:
# version >= 1.10
id=R01; version˜=1\.[1−9][0−9]; sender_domain==some.org \
; action=REJECT sorry no access
postfwd_port − postfwd server port, allows to use the same ruleset different
instances:
# rule only hits for instance at port 10045
id=PORT10045; postfwd_port==10045; action=DUNNO
postfwd_interface − postfwd server initerface, see postfwd_port
ratecount − only available for rate(), size() and rcpt() actions.
contains the actual limit counter:
id=R01; action=rate(sender/200/600/REJECT limit of 200 exceeded [$$ratecount hits])
id=R02; action=rate(sender/100/600/WARN limit of 100 exceeded [$$ratecount hits])

Besides these you can specify any attribute of the postfix policy delegation protocol. Feel free to combine them the way you need it (have a look at the EXAMPLES section below).

Most values can be specified as regular expressions ( PCRE ). Please see the table below for details:

# ==========================================================
# ITEM=VALUE TYPE
# ==========================================================
id=something mask = string
date=01.04.2007−22.04.2007 mask = date (DD.MM.YYYY−DD.MM.YYYY)
time=08:30:00−17:00:00 mask = time (HH:MM:SS−HH:MM:SS)
days=Mon−Wed mask = weekdays (Mon−Wed) or numeric (1−3)
months=Feb−Apr mask = months (Feb−Apr) or numeric (1−3)
score=5.0 mask = maximum floating point value
rbl=zen.spamhaus.org mask = <name>/<reply>/<maxcache>[,...]
rblcount=2 mask = numeric, will match if rbl hits >= 2
helo_address=<a.b.c.d/nn> mask = CIDR[,CIDR,...]
sender_ns_names=some.domain.tld mask = PCRE
sender_mx_names=some.domain.tld mask = PCRE
sender_ns_addrs=<a.b.c.d/nn> mask = CIDR[,CIDR,...]
sender_mx_addrs=<a.b.c.d/nn> mask = CIDR[,CIDR,...]
# −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
# Postfix version 2.1 and later:
# −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
client_address=<a.b.c.d/nn> mask = CIDR[,CIDR,...]
client_name=another.domain.tld mask = PCRE
reverse_client_name=another.domain.tld mask = PCRE
helo_name=some.domain.tld mask = PCRE
[email protected] mask = PCRE
[email protected] mask = PCRE
recipient_count=5 mask = numeric, will match if recipients >= 5
# −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
# Postfix version 2.2 and later:
# −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
sasl_method=plain mask = PCRE
sasl_username=you mask = PCRE
sasl_sender= mask = PCRE
size=12345 mask = numeric, will match if size >= 12345
ccert_subject=blackhole.nowhere.local mask = PCRE (only if tls verified)
ccert_issuer=John+20Doe mask = PCRE (only if tls verified)
ccert_fingerprint=AA:BB:CC:DD:EE:... mask = PCRE (do NOT use "..." here)
# −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
# Postfix version 2.3 and later:
# −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
encryption_protocol=TLSv1/SSLv3 mask = PCRE
encryption_cipher=DHE−RSA−AES256−SHA mask = PCRE
encryption_keysize=256 mask = numeric, will match if keysize >= 256
...

the current list can be found at <http://www.postfix.org/SMTPD_POLICY_README.html>. Please read carefully about which attribute can be used at which level of the smtp transaction (e.g. size will only work reliably at END-OF-MESSAGE level). Pattern matching is performed case insensitive.

Multiple use of the same item is allowed and will compared as logical OR, which means that this will work as expected:

id=TRUST001; action=OK; encryption_keysize=64
ccert_fingerprint=11:22:33:44:55:66:77:88:99
ccert_fingerprint=22:33:44:55:66:77:88:99:00
ccert_fingerprint=33:44:55:66:77:88:99:00:11
sender=@domain\.local$

client_address, rbl and rhsbl items may also be specified as whitespace-or-comma-separated values:

id=SKIP01; action=dunno
client_address=192.168.1.0/24, 172.16.254.23
id=SKIP02; action=dunno
client_address= 10.10.3.32 10.216.222.0/27

The following items must be unique:

id, minimum and maximum values, rblcount and rhsblcount

Any item can be negated by preceeding ’!!’ to it, e.g.:

id=HOST001 ; hostname == !!secure.trust.local ; action=REJECT only secure.trust.local please

or using the right compare operator:

id=HOST001 ; hostname != secure.trust.local ; action=REJECT only secure.trust.local please

To avoid confusion with regexps or simply for better visibility you can use ’!!(...)’:

id=USER01 ; sasl_username =˜ !!( /ˆ(bob|alice)$/ ) ; action=REJECT who is that?

Request attributes can be compared by preceeding ’$$’ characters, e.g.:

id=R−003 ; client_name = !! $$helo_name ; action=WARN helo does not match DNS
# or
id=R−003 ; client_name = !!($$(helo_name)) ; action=WARN helo does not match DNS

This is only valid for PCRE values (see list above). The comparison will be performed as case insensitive exact match. Use the ’−vv’ option to debug.

These special items will be reset for any new rule:

rblcount − contains the number of RBL answers
rhsblcount − contains the number of RHSBL answers
matches − contains the number of matched items
dnsbltext − contains the dns TXT part of all RBL and RHSBL replies in the form
rbltype:rblname:<txt>; rbltype:rblname:<txt>; ...

These special items will be changed for any matching rule:

request_hits − contains ids of all matching rules

This means that it might be necessary to save them, if you plan to use these values in later rules:

# set vals
id=RBL01 ; rhsblcount=all; rblcount=all
action=set(HIT_rhls=$$rhsblcount,HIT_rbls=$$rblcount,HIT_txt=$$dnsbltext)
rbl=list.dsbl.org, bl.spamcop.net, dnsbl.sorbs.net, zen.spamhaus.org
rhsbl_client=rddn.dnsbl.net.au, rhsbl.ahbl.org, rhsbl.sorbs.net
rhsbl_sender=rddn.dnsbl.net.au, rhsbl.ahbl.org, rhsbl.sorbs.net
# compare
id=RBL02 ; HIT_rhls>=1 ; HIT_rbls>=1 ; action=554 5.7.1 blocked using $$HIT_rhls RHSBLs and $$HIT_rbls RBLs [INFO: $$HIT_txt]
id=RBL03 ; HIT_rhls>=2 ; action=554 5.7.1 blocked using $$HIT_rhls RHSBLs [INFO: $$HIT_txt]
id=RBL04 ; HIT_rbls>=2 ; action=554 5.7.1 blocked using $$HIT_rbls RBLs [INFO: $$HIT_txt]

FILES

Since postfwd1 v1.15 and postfwd3 v0.18 long item lists can be stored in separate files:

id=R001 ; ccert_fingerprint==file:/etc/postfwd/wl_ccerts ; action=DUNNO

postfwd3 will read a list of items (one item per line) from /etc/postfwd/wl_ccerts. comments are allowed:

# client1
11:22:33:44:55:66:77:88:99
# client2
22:33:44:55:66:77:88:99:00
# client3
33:44:55:66:77:88:99:00:11

To use existing tables in key=value format, you can use:

id=R001 ; ccert_fingerprint==table:/etc/postfwd/wl_ccerts ; action=DUNNO

This will ignore the right-hand value. Items can be mixed:

id=R002 ; action=REJECT
client_name==unknown
client_name==file:/etc/postfwd/blacklisted

and for non pcre (comma separated) items:

id=R003 ; action=REJECT
client_address==10.1.1.1, file:/etc/postfwd/blacklisted
id=R004 ; action=REJECT
rbl=myrbl.home.local, zen.spamhaus.org, file:/etc/postfwd/rbls_changing

You can check your configuration with the −−show_config option at the command line:

# postfwd3 −−showconfig −−rule='action=DUNNO; client_address=10.1.0.0/16, file:/etc/postfwd/wl_clients, 192.168.2.1'

should give something like:

Rule 0: id−>"R−0"; action−>"DUNNO"; client_address−>"=;10.1.0.0/16, =;194.123.86.10, =;186.4.6.12, =;192.168.2.1"

If a file can not be read, it will be ignored:

# postfwd3 −−showconfig −−rule='action=DUNNO; client_address=10.1.0.0/16, file:/etc/postfwd/wl_clients, 192.168.2.1'
[LOG warning]: error: file /etc/postfwd/wl_clients not found − file will be ignored ?
Rule 0: id−>"R−0"; action−>"DUNNO"; client_address−>"=;10.1.0.0/16, =;192.168.2.1"

File items are evaluated at configuration stage. Therefore postfwd3 needs to be reloaded if a file has changed

If you want to specify a file, that will be reloaded for each request, you can use lfile: and ltable:

id=R001; client_address=lfile:/etc/postfwd/client_whitelist; action=dunno

This will check the modification time of /etc/postfwd/client_whitelist every time the rule is evaluated and reload it as necessary. Of course this might increase the system load, so please use it with care.

The −−showconfig option illustrates the difference:

## evaluated at configuration stage
# postfwd3 −−nodaemon −L −−rule='client_address=table:/etc/postfwd/clients; action=dunno' −C
Rule 0: id−>"R−0"; action−>"dunno"; client_address−>"=;1.1.1.1, =;1.1.1.2, =;1.1.1.3"
## evaluated for any rulehit
# postfwd3 −−nodaemon −L −−rule='client_address=ltable:/etc/postfwd/clients; action=dunno' −C
Rule 0: id−>"R−0"; action−>"dunno"; client_address−>"=;ltable:/etc/postfwd/clients"

Files can refer to other files. The following is valid.

−− FILE /etc/postfwd/rules.cf −−
id=R01; client_address=file:/etc/postfwd/clients_master.cf; action=DUNNO
−− FILE /etc/postfwd/clients_master.cf −−
192.168.1.0/24
file:/etc/postfwd/clients_east.cf
file:/etc/postfwd/clients_west.cf
−− FILE /etc/postfwd/clients_east.cf −−
192.168.2.0/24
−− FILE /etc/postfwd/clients_west.cf −−
192.168.3.0/24

Note that there is currently no loop detection (/a/file calls /a/file) and that this feature is only available with postfwd1 v1.15 and postfwd3 v0.18 and higher.

ACTIONS

General

Actions will be executed, when all rule items have matched a request (or at least one of any item list). You can refer to request attributes by preceeding $$ characters, like:

id=R−003; client_name = !!$$helo_name; action=WARN helo '$$helo_name' does not match DNS '$$client_name'
# or
id=R−003; client_name = !!$$helo_name; action=WARN helo '$$(helo_name)' does not match DNS '$$(client_name)'

postfix actions

Actions will be replied to postfix as result to policy delegation requests. Any action that postfix understands is allowed − see "man 5 access" or <http://www.postfix.org/access.5.html> for a description. If no action is specified, the postfix WARN action which simply logs the event will be used for the corresponding rule.

postfwd3 will return dunno if it has reached the end of the ruleset and no rule has matched. This can be changed by placing a last rule containing only an action statement:

...
action=dunno ; [email protected] # sender is ok
action=reject # default deny

postfwd3 actions

postfwd3 actions control the behaviour of the program. Currently you can specify the following:

jump (<id>)
jumps to rule with id <id>, use this to skip certain rules.
you can jump backwards − but remember that there is no loop
detection at the moment! jumps to non−existing ids will be skipped.
score (<score>)
the request's score will be modified by the specified <score>,
which must be a floating point value. the modificator can be either
+n.nn adds n.nn to current score
−n.nn sustracts n.nn from the current score
*n.nn multiplies the current score by n.nn
/n.nn divides the current score through n.nn
=n.nn sets the current score to n.nn
if the score exceeds the maximum set by `−−scores` option (see
COMMAND LINE) or the score item (see ITEMS section), the action
defined for this case will be returned (default: 5.0=>"REJECT postfwd3 score exceeded").
set (<item>=<value>,<item>=<value>,...)
this command allows you to insert or override request attributes, which then may be
compared to your further ruleset. use this to speed up repeated comparisons to large item lists.
please see the EXAMPLES section for more information. you may separate multiple key=value pairs
by "," characters.
rate (<item>/<max>/<time>/<action>)
this command creates a counter for the given <item>, which will be increased any time a request
containing it arrives. if it exceeds <max> within <time> seconds it will return <action> to postfix.
rate counters are very fast as they are executed before the ruleset is parsed.
please note that <action> was limited to postfix actions (no postfwd actions) for postfwd versions <1.33!
# no more than 3 requests per 5 minutes
# from the same "unknown" client
id=RATE01 ; client_name==unknown
action=rate(client_address/3/300/450 4.7.1 sorry, max 3 requests per 5 minutes)
size (<item>/<max>/<time>/<action>)
this command works similar to the rate() command with the difference, that the rate counter is
increased by the request's size attribute. to do this reliably you should call postfwd3 from
smtpd_end_of_data_restrictions. if you want to be sure, you could check it within the ruleset:
# size limit 1.5mb per hour per client
id=SIZE01 ; protocol_state==END−OF−MESSAGE ; client_address==!!(10.1.1.1)
action=size(client_address/1572864/3600/450 4.7.1 sorry, max 1.5mb per hour)
rcpt (<item>/<max>/<time>/<action>)
this command works similar to the rate() command with the difference, that the rate counter is
increased by the request's recipient_count attribute. to do this reliably you should call postfwd
from smtpd_data_restrictions or smtpd_end_of_data_restrictions. if you want to be sure, you could
check it within the ruleset:
# recipient count limit 3 per hour per client
id=RCPT01 ; protocol_state==END−OF−MESSAGE ; client_address==!!(10.1.1.1)
action=rcpt(client_address/3/3600/450 4.7.1 sorry, max 3 recipients per hour)
rate5321,size5321,rcpt5321 (<item>/<max>/<time>/<action>)
same as the corresponding non−5321 functions, with the difference that the localpart of
sender oder recipient addresses are evaluated case−sensitive according to rfc5321. That
means that requests from [email protected] and [email protected] will be treated differently
groupadd(<groupname>/<item>[/<ttl>])
saves <item> to dynamic group <group> for later use. the object will be removed from that
group after ttl seconds. if not set, postfwd3 will use the default −−default_group_ttl [3600s].
Please read the chapter about dynamic groups before use!
# add client_address to group %%blacklisted_hosts
id=ADDGROUP
rbl=zen.spamhaus.org,bl.spamcop.net,ix.dnsbl.manitu.net
action=groupadd(%%blacklisted_hosts/client_address/86400)
groupdel(<groupname>/<item>)
removes <item> from dynamic group <group>. Please read the chapter about dynamic groups before use!
# remove a client_address from group %%blacklisted_hosts
id=DELGROUP
rbl=lists.dnswl.org
action=groupdel(%%blacklisted_hosts/client_address)
ask (<addr>:<port>[:<ignore>])
allows to delegate the policy decision to another policy service (e.g. postgrey). the first
and the second argument (address and port) are mandatory. a third optional argument may be
specified to tell postfwd3 to ignore certain answers and go on parsing the ruleset:
# example1: query postgrey and return it's answer to postfix
id=GREY; client_address==10.1.1.1; action=ask(127.0.0.1:10031)
# example2: query postgrey but ignore it's answer, if it matches 'DUNNO'
# and continue parsing postfwd's ruleset
id=GREY; client_address==10.1.1.1; action=ask(127.0.0.1:10031:ˆdunno$)
mail(server/helo/from/to/subject/body)
This command is deprecated. You should try to use the sendmail() action instead.
Very basic mail command, that sends a message with the given arguments. LIMITATIONS:
This basically performs a telnet. No authentication or TLS are available. Additionally it does
not track notification state and will notify you any time, the corresponding rule hits.
sendmail(sendmail−path::from::to::subject::body)
Mail command, that uses an existing sendmail binary and sends a message with the given arguments.
LIMITATIONS: The command does not track notification state and will notify you any time, the
corresponding rule hits (which could mean 100 mails for a mail with 100 recipients at RCPT stage).
wait (<delay>)
pauses the program execution for <delay> seconds. use this for
delaying or throtteling connections.
note (<string>)
just logs the given string and continues parsing the ruleset.
if the string is empty, nothing will be logged (noop).
quit (<code>)
terminates the program with the given exit−code. postfix doesn`t
like that too much, so use it with care.

You can reference to request attributes, like

id=R−HELO ; helo_name=ˆ[ˆ\.]+$ ; action=REJECT invalid helo '$$helo_name'

Since postfwd3 version 2.00 a rule can have multiple postfwd actions, like

# if client is found on list.dnswl.org,
# 1. send a note
# 2. add it's ip to group %%WHITELISTED
# 3. permit the request
id=ADDR01
rbl=list.dnswl.org
action=note(adding $$client_address to WHITELIST)
action=groupadd(%%WHITELISTED/client_address)
action=PERMIT_AUTH_DESTINATION

MACROS/ACLS

Multiple use of long items or combinations of them may be abbreviated by macros. Those must be prefixed by ’&&’ (two ’&’ characters). First the macros have to be defined as follows:

&&RBLS { rbl=zen.spamhaus.org,list.dsbl.org,bl.spamcop.net,dnsbl.sorbs.net,ix.dnsbl.manitu.net; };

Then these may be used in your rules, like:

&&RBLS ; client_name=ˆunknown$ ; action=REJECT
&&RBLS ; client_name=(\d+[\.−_]){4} ; action=REJECT
&&RBLS ; client_name=[\.−_](adsl|dynamic|ppp|)[\.−_] ; action=REJECT

Macros can contain actions, too:

# definition
&&GONOW { action=REJECT your request caused our spam detection policy to reject this message. More info at http://www.domain.local; };
# rules
&&GONOW ; &&RBLS ; client_name=ˆunknown$
&&GONOW ; &&RBLS ; client_name=(\d+[\.−_]){4}
&&GONOW ; &&RBLS ; client_name=[\.−_](adsl|dynamic|ppp|)[\.−_]

Macros can contain macros, too:

# definition
&&RBLS{
rbl=zen.spamhaus.org
rbl=list.dsbl.org
rbl=bl.spamcop.net
rbl=dnsbl.sorbs.net
rbl=ix.dnsbl.manitu.net
};
&&DYNAMIC{
client_name=ˆunknown$
client_name=(\d+[\.−_]){4}
client_name=[\.−_](adsl|dynamic|ppp|)[\.−_]
};
&&GOAWAY { &&RBLS; &&DYNAMIC; };
# rules
&&GOAWAY ; action=REJECT dynamic client and listed on RBL

Basically macros are simple text substitutions − see the " PARSER" section for more information.

DYNAMIC GROUPS

Dynamic groups are list objects. You can add or remove items and compare request items to their content within your ruleset. Groups are saved persistant for further requests. This way you can save information for later use. Every item of a group has a time-to-live value.

Group-names have to be preceeded by double ’%’−characters, like %%GROUPNAME:

# add client_address to group %%BLACKLISTED, if sent to spamtrap
id=SPAMTRAP; [email protected]; action=groupadd(%%BLACKLISTED/client_address)
# reject any request from client_address in group %%BLACKLISTED
id=BLACKLISTED; client_address=%%BLACKLISTED; action=REJECT

The groupadd() function receives the following arguments. The <ttl> value is optional. If not specified, postfwd3 will use the default −−default_group_ttl [300s]:

groupadd ( <Groupname> / <item> [ / <ttl> ] )

postfwd will save this data in the following structure:

%Group_Cache −> %<Groupname> −> $<item> = <ttl>

The groupdel() function removes an item from a group:

groupdel ( <Groupname> / <item> )

Expired members will be removed at cleanup stage after −−cleanup_groups seconds.

To compare requests with dynamic groups, these must be refered by preceeding ’%%’−characters:

Empty groups always compare false. The following ruleset is possible:

# allow any request from client_address in group %%WHITELISTED
id=WHITEGROUP; client_address=%%WHITELISTED; action=DUNNO
# reject any request from client_address in group %%BLACKLISTED
id=BLACKGROUP; client_address=%%BLACKLISTED; action=REJECT
# ... other rules ...
# ... whitelist file ...
id=W_TRUST; action=set(WHITE=1)
client_address=file:/etc/postfwd/whitelist_networks
# ... whitelist dns ...
id=W_DNSWL; action=set(WHITE=1)
rbl=list.dnswl.org
# ... −> add it to whitelist for a day and allow request
id=W_GROUP; WHITE==1
action=groupadd(%%WHITELISTED/client_address/86400)
action=DUNNO
# ... or blacklist by sending to spamtrap ...
id=B_SPAMTRAP; action=set(BLACK=1)
[email protected]
# ... or blacklisted by dns ...
id=B_DNSBL; action=set(BLACK=1)
rbl=zen.spamhaus.org
# ... −> add it to group BLACKLISTED for 1 hour and reject
id=B_GROUP; BLACK==1
action=groupadd(%%BLACKLISTED/client_address/3600)
action=REJECT

Limitations

Currently dynamic groups are kept in memory. By default postfwd3 will only accept a maximum of 999999 members in a group. To deactivate this limit set −−group_maxitems to ’−1’.

With PreFork personality, you should be aware that this information must be shared through the cache daemon.

In short: Don’t let these lists get excessively big unless you have enough system capacity to do so. If necessary tune your config by setting the <ttl> and −−group_maxitems.

PLUGINS

Description

The plugin interface allow you to define your own checks and enhance postfwd’s functionality. Feel free to share useful things!

Warning

Note that the plugin interface is still at devel stage. Please test your plugins carefully, because errors may cause postfwd to break! It is also allowed to override attributes or built-in functions, but be sure that you know what you do because some of them are used internally.

Please keep security in mind, when you access sensible ressources and never, ever run postfwd as privileged user! Also never trust your input (especially hostnames, and e−mail addresses).

ITEMS

Item plugins are perl subroutines which integrate additional attributes to requests before they are evaluated against postfwd’s ruleset like any other item of the policy delegation protocol. This allows you to create your own checks.

plugin-items can not be used selective. these functions will be executed for every request postfwd receives, so keep performance in mind.

SYNOPSIS: postfwd_items_plugin{<name>}($request)

means that your subroutine, called <name>, has access to a hash-reference called $request, which contains all request attributes, like $request−>{client_name} and saves values in the following form:

save: $result−>{<item>} = <value>

this creates the new item <item> containing <value>, which will be integrated in the policy delegation request and therefore may be used in postfwd’s ruleset.

# do NOT remove the next line
%postfwd_items_plugin = (
# EXAMPLES − integrated in postfwd. no need to activate them here.
# allows to check postfwd version in ruleset
"version" => sub {
my($request) = shift;
$request−>{version} => $NAME." ".$VERSION,
},
# sender_domain and recipient_domain
"address_parts" => sub {
my($request) = shift;
$request−>{sender} =˜ /@([ˆ@]*)$/;
$request−>{sender_domain} = ($1 || '');
$request−>{recipient} =˜ /@([ˆ@]*)$/;
$request−>{recipient_domain} = ($1 || '');
},
# do NOT remove the next line
);

COMPARE

Compare plugins allow you to define how your new items should be compared to the ruleset. These are optional. If you don’t specify one, the default (== for exact match, =˜ for PCRE, ... ) will be used.

SYNOPSIS: <item> => sub { return &{$postfwd_compare{<type>}}(@_); },
# do NOT remove the next line
%postfwd_compare_plugin = (
EXAMPLES − integrated in postfwd. no need to activate them here.
# Simple example
# SYNOPSIS: <result> = <item> (return &{$postfwd_compare{<type>}}(@_))
"client_address" => sub { return &{$postfwd_compare{cidr}}(@_); },
"size" => sub { return &{$postfwd_compare{numeric}}(@_); },
"recipient_count" => sub { return &{$postfwd_compare{numeric}}(@_); },
# Complex example
# SYNOPSIS: <result> = <item>(<operator>, <ruleset value>, <request value>, <request>)
"numeric" => sub {
my($cmp,$val,$myitem,$request) = @_;
my($myresult) = undef; $myitem ||= "0"; $val ||= "0";
if ($cmp eq '==') {
$myresult = ($myitem == $val);
} elsif ($cmp eq '=<') {
$myresult = ($myitem <= $val);
} elsif ($cmp eq '=>') {
$myresult = ($myitem >= $val);
} elsif ($cmp eq '<') {
$myresult = ($myitem < $val);
} elsif ($cmp eq '>') {
$myresult = ($myitem > $val);
} elsif ($cmp eq '!=') {
$myresult = not($myitem == $val);
} elsif ($cmp eq '!<') {
$myresult = not($myitem <= $val);
} elsif ($cmp eq '!>') {
$myresult = not($myitem >= $val);
} else {
$myresult = ($myitem >= $val);
};
return $myresult;
},
# do NOT remove the next line
);

ACTIONS

Action plugins allow to define new postfwd actions. By setting the $stop−flag you can decide to continue or to stop parsing the ruleset.

SYNOPSIS: (<stop rule parsing>, <next rule index>, <return action>, <logprefix>) =
<action> (<current rule index>, <current time>, <command name>, <argument>, <logprefix>, <request>)
# do NOT remove the next line
%postfwd_actions_plugin = (
# EXAMPLES − integrated in postfwd. no need to activate them here.
# note(<logstring>) command
"note" => sub {
my($index,$now,$mycmd,$myarg,$myline,$request) = @_;
my($myaction) = 'dunno'; my($stop) = 0;
log_info "[RULES] ".$myline." − note: ".$myarg if $myarg;
return ($stop,$index,$myaction,$myline);
},
# skips next <myarg> rules
"skip" => sub {
my($index,$now,$mycmd,$myarg,$myline,$request) = @_;
my($myaction) = 'dunno'; my($stop) = 0;
$index += $myarg if ( $myarg and not(($index + $myarg) > $#Rules) );
return ($stop,$index,$myaction,$myline);
},
# dumps current request contents to syslog
"dumprequest" => sub {
my($index,$now,$mycmd,$myarg,$myline,$request) = @_;
my($myaction) = 'dunno'; my($stop) = 0;
map { log_info "[DUMP] rule=$index, Attribute: $_=$request{$_}" } (keys %{$request});
return ($stop,$index,$myaction,$myline);
},
# do NOT remove the next line
);

COMMAND LINE

Ruleset

The following arguments are used to specify the source of the postfwd3 ruleset. This means that at least one of the following is required for postfwd3 to work.

−f, −−file <file>
Reads rules from <file>. Please see the CONFIGURATION section
for more information.
−r, −−rule <rule>
Adds <rule> to ruleset. Remember that you might have to quote
strings that contain whitespaces or shell characters.

Settings

−F, −−loadsettings <file>
Loads program settings from <file>. data must be in Data::Dumper format.
Please read the SETTINGS section for more information.
−−savesettings <file>
Saves program settings to <file> in Data::Dumper format.
Please read the SETTINGS section for more information.
−−showsettings
Exports program settings in Data::Dumper format to stdout. This output
can be saved to a file and later used with the −−loadsettings option.

Scoring

−s, −−scores <val>=<action>
Returns <action> to postfix, when the request's score exceeds <val>

Multiple usage is allowed. Just chain your arguments, like:

postfwd3 −r "<item>=<value>;action=<result>" −f <file> −f <file> ...
or
postfwd3 −−scores 4.5="WARN high score" −−scores 5.0="REJECT postfwd3 score too high" ...

In case of multiple scores, the highest match will count. The order of the arguments will be reflected in the postfwd3 ruleset.

Networking

postfwd3 can be run as daemon so that it listens on the network for incoming requests. The following arguments will control it’s behaviour in this case.

−d, −−daemon, −−nodaemon
postfwd3 will run as daemon and listen on the network for incoming
queries (default 127.0.0.1:10045). Use −−nodaemon to keep postfwd3
running in foreground.
−i, −−interface <dev>
Bind postfwd3 to the specified interface (default 127.0.0.1).
−p, −−port <port>
postfwd3 listens on the specified port (default tcp/10045).
−−proto <type>
The protocol type for postfwd's socket. Currently you may use 'tcp' or 'unix' here.
To use postfwd3 with a unix domain socket, run it as follows:
postfwd3 −−proto=unix −−port=/somewhere/postfwd.socket
−u, −−user <name>
Changes real and effective user to <name>.
−g, −−group <name>
Changes real and effective group to <name>.
−−personality <type>
Type of policy server, allows 'PreFork' or 'Multiplex'.
This option overrides −−autopersonality.
−−v1
set personality to 'Multiplex'
This option overrides −−autopersonality.
−−v2
set personality to 'PreFork'
This option overrides −−autopersonality.
−−autopersonality
postfwd3 determines the personality by program name:
* 'Multiplex' for 'postfwd' or 'postfwd1'
* 'PreFork' for 'postfwd2'
you can disable this by using −−noautopersonality or
explicitly using −−personality, −−v1 or −−v2
−−umask <mask>
Changes the umask for filepermissions of the master process (pidfile).
Attention: This is umask, not chmod − you have to specify the bits that
should NOT apply. E.g.: umask 077 equals to chmod 700.
−−cache_umask <mask>
Changes the umask for filepermissions of the cache process (unix domain socket).
−−server_umask <mask>
Changes the umask for filepermissions of the server process (unix domain socket).
−R, −−chroot <path>
Chroot the process to the specified path.
Please look at http://postfwd.org/postfwd3−chroot.html before use!
−−pidfile <path>
The process id will be saved in the specified file.
−−facility <f>
sets the syslog facility, default is 'mail'
−−socktype <s>
sets the Sys::Syslog socktype to 'native', 'inet' or 'unix'.
Default is to auto−detect this depening on module version and os.
−l, −−logname <label>
Labels the syslog messages. Useful when running multiple
instances of postfwd.
−−loglen <int>
Truncates any syslog message after <int> characters.

Plugins

−−plugins <file>
Loads postfwd plugins from file. Please see http://postfwd.org/postfwd.plugins
or the plugins.postfwd.sample that is available from the tarball for more info.

Optional arguments

These parameters influence the way postfwd3 is working. Any of them can be combined.

−v, −−verbose
Verbose logging displays a lot of useful information but can cause
your logfiles to grow noticeably. So use it with caution. Set the option
twice (−vv) to get more information (logs all request attributes).
−c, −−cache <int> (default=600)
Timeout for request cache, results for identical requests will be
cached until config is reloaded or this time (in seconds) expired.
A setting of 0 disables this feature.
−−cache−no−size
Ignores size attribute for cache comparisons which will lead to better
cache−hit rates. You should set this option, if you don't use the size
item in your ruleset.
−−cache−no−sender
Ignores sender address for cache comparisons which will lead to better
cache−hit rates. You should set this option, if you don't use the sender
item in your ruleset.
−−cache−rdomain−only
This will strip the localpart of the recipient's address before filling the
cache. This may considerably increase cache−hit rates.
−−cache−rbl−timeout <timeout> (default=3600)
This default value will be used as timeout in seconds for rbl cache items,
if not specified in the ruleset.
−−cache−rbl−default <pattern> (default=ˆ127\.0\.0\.\d+$)
Matches <pattern> to rbl/rhsbl answers (regexp) if not specified in the ruleset.
−−cacheid <item>, <item>, ...
This csv−separated list of request attributes will be used to construct
the request cache identifier. Use this only, if you know exactly what you
are doing. If you, for example, use postfwd3 only for RBL/RHSBL control,
you may set this to
postfwd3 −−cache=3600 −−cacheid=client_name,client_address
This increases efficiency of caching and improves postfwd's performance.
Warning: You should list all items here, which are used in your ruleset!
−−cacheid_md5, −−nocacheid_md5 (default=1)
The cacheid will be created with a md5sum of the request items.
−−cleanup−requests <interval> (default=600)
The request cache will be searched for timed out items after this <interval> in
seconds. It is a minimum value. The cleanup process will only take place, when
a new request arrives.
−−cleanup−rbls <interval> (default=600)
The rbl cache will be searched for timed out items after this <interval> in
seconds. It is a minimum value. The cleanup process will only take place, when
a new request arrives.
−−cleanup−rates <interval> (default=600)
The rate cache will be searched for timed out items after this <interval> in
seconds. It is a minimum value. The cleanup process will only take place, when
a new request arrives.
−S, −−summary <int> (default=600)
Shows some usage statistics (program uptime, request counter, matching rules)
every <int> seconds. This option is included by the −v switch.
This feature uses the alarm signal, so you can force postfwd3 to dump the stats
using `kill −ALRM <pid>` (where <pid> is the process id of postfwd).
Example:
Aug 19 12:39:45 mail1 postfwd[666]: [STATS] Counters: 213000 seconds uptime, 39 rules
Aug 19 12:39:45 mail1 postfwd[666]: [STATS] Requests: 71643 overall, 49 last interval, 62.88% cache hits
Aug 19 12:39:45 mail1 postfwd[666]: [STATS] Averages: 20.18 overall, 4.90 last interval, 557.30 top
Aug 19 12:39:45 mail1 postfwd[666]: [STATS] Contents: 44 cached requests, 239 cached dnsbl results
Aug 19 12:39:45 mail1 postfwd[666]: [STATS] Rule ID: R−001 matched: 2704 times
Aug 19 12:39:45 mail1 postfwd[666]: [STATS] Rule ID: R−002 matched: 9351 times
Aug 19 12:39:45 mail1 postfwd[666]: [STATS] Rule ID: R−003 matched: 3116 times
...
−−no−rulestats
Disables per rule statistics. Keeps your log clean, if you do not use them.
This option has no effect without −−summary or −−verbose set.
−L, −−stdout
Redirects all syslog messages to stdout for debugging. Do not use this in daemon mode!
−−stdin
Tells postfwd to get the request data from STDIN instead of a network socket. This
may be used to test rulesets at the command−line:
Example:
postfwd −f /etc/postfwd/postfwd.cf −−stdin −−stdout −−nodaemon ../tools/request.sample
−−cmd
Shorthand for the combination −−stdin, −−stdout and −−nodaemon
Example:
postfwd −f /etc/postfwd/postfwd.cf −−cmd ../tools/request.sample
−t, −−test
In test mode postfwd3 always returns "dunno", but logs according
to it`s ruleset. −v will be set automatically with this option.
−n, −−nodns
Disables all DNS based checks like RBL checks. Rules containing
such elements will be ignored.
−n, −−nodnslog
Disables logging of dns events.
−−dns_timeout (default: 14)
Sets the timeout for asynchonous dns queries in seconds. This value will apply to
all dns items in a rule.
−−dns_timeout_max (default: 10)
Sets the maximum timeout counter for dnsbl lookups. If the timeouts exceed this value
the corresponding dnsbl will be deactivated for a while (see −−dns_timeout_interval).
−−dns_timeout_interval (default=1200)
The dnsbl timeout counter will be cleaned after this interval in seconds. Use this
in conjunction with the −−dns_timeout_max parameter.
−−dns_async_txt
Perform dnsbl A and TXT lookups simultaneously (otherwise only for listings with at
least one A record). This needs more network bandwidth due to increased queries but
might increase throughput because the lookups can be parallelized.
−−dns_max_ns_lookups (default=0)
maximum ns names to lookup up with sender_ns_addrs item. use 0 for no maximum.
−−dns_max_mx_lookups (default=0)
maximum mx names to lookup up with sender_mx_addrs item. use 0 for no maximum.
−−ipv6_dnsbl (default=0)
enables dnsbl checks for IPv6 addresses
−I, −−instantcfg
The config files, specified by −f will be re−read for every request
postfwd3 receives. This enables on−the−fly configuration changes
without restarting. Though files will be read only if necessary
(which means their access times changed since last read) this might
significantly increase system load.
−−config_timeout (default=3)
timeout in seconds to parse a single configuration line. if exceeded, the rule will
be skipped. this is used to prevent problems due to large files or loops.
−−keep_groups (default=0)
With this option set postfwd3 does not clear the group cache on reload. Please
note that you have to restart (not reload) postfwd with this option if you change
any group based rules.
−−save_groups (default=none)
With this option postfwd saves existing groups to disk and reloads them on program
start. This allows persistent rate limits across program restarts or reboots.
Please note that postfwd needs read and write access to the specified file.
−−keep_rates (default=0)
With this option set postfwd3 does not clear the rate limit counters on reload. Please
note that you have to restart (not reload) postfwd with this option if you change
any rate limit rules.
−−save_rates (default=none)
With this option postfwd saves existing rate limit counters to disk and reloads them
on program start. This allows persistent rate limits across program restarts or reboots.
Please note that postfwd needs read and write access to the specified file.
−A, −−aggregate_addrs, −−noaggregate_addrs
Pre−computes ip address lists to subnets, so that e.g.:
client_address=10.0.0.0/24, 10.0.1.0/24, 10.0.2.0/24, 10.0.3.0/24
will result in
client_address=10.0.0.0/22
This increases the performance of cidr−matching
−−no_netaddr
Do not use functions from module NetAddr::IP, even if it was found
on the system. This option implicitly disables −−aggregate_addrs.
−−no_netcidr
Do not use functions from module Net::CIDR::Lite, even if it was found
on the system.
−−cidr_method=s (default=autodetect)
Use method <s> for network checks. Valid arguments are:
netcidr − compare networks using Net::CIDR::Lite Module (v4 and v6 cidr)
netaddr − compare networks using NetAddr::IP Module (v4 and v6 cidr)
postfwd − old but very fast method (v4=cidr, v6=regex)
If not specified postfwd tries to load modules in the above order and falls back
to 'postfwd' if nothing found.

Informational arguments

These arguments are for command line usage only. Never ever use them with postfix!

−C, −−showconfig
Displays the current ruleset. Use −v for verbose output.
−V, −−version
Displays the program version.
−h, −−help
Shows program usage.
−m, −−manual
Displays the program manual.
−D, −−defaults
displays complete postfwd3 settings.
−P, −−perfmon
This option turns of any syslogging and output. It is included
for performance testing.
−−dumpstats
Displays program usage statistics.
−−dumpcache
Displays cache contents.
−−delcache <item>
Removes an item from the request cache. Use −−dumpcache to identify objects.
E.g.:
# postfwd −−dumpcache
...
%rate_cache −> %[email protected] −> %RATE002+2_600 −> @count −> '1'
%rate_cache −> %[email protected] −> %RATE002+2_600 −> @maxcount −> '2'
...
# postfwd −−delrate="[email protected]"
rate cache item '[email protected]' removed
−−delrate <item>
Removes an item from the rate cache. Use −−dumpcache to identify objects.

REFRESH

In daemon mode postfwd3 reloads it’s ruleset after receiving a HUP signal. Please see the description of the ’−I’ switch to have your configuration refreshed for every request postfwd3 receives.

EXAMPLES

## whitelisting
# 1. networks 192.168.1.0/24, 192.168.2.4
# 2. client_names *.gmx.net and *.gmx.de
# 3. sender *@someshop.tld from 11.22.33.44
id=WL001; action=dunno ; client_address=192.168.1.0/24, 192.168.2.4
id=WL002; action=dunno ; client_name=\.gmx\.(net|de)$
id=WL003; action=dunno ; sender=@someshop\.tld$ ; client_address=11.22.33.44
## TLS control
# 1. *@authority.tld only with correct TLS fingerprint
# 2. *@secret.tld only with keysizes >=64
id=TL001; action=dunno ; sender=@authority\.tld$ ; ccert_fingerprint=AA:BB:CC..
id=TL002; action=REJECT wrong TLS fingerprint ; sender=@authority\.tld$
id=TL003; action=REJECT tls keylength < 64 ; sender=@secret\.tld$ ; encryption_keysize=64
## Combined RBL checks
# This will reject mail if
# 1. listed on ix.dnsbl.manitu.net
# 2. listed on zen.spamhaus.org (sbl and xbl, dns cache timeout 1200s instead of 3600s)
# 3. listed on min 2 of bl.spamcop.net, list.dsbl.org, dnsbl.sorbs.net
# 4. listed on bl.spamcop.net and one of rhsbl.ahbl.org, rhsbl.sorbs.net
id=RBL01 ; action=REJECT listed on ix.dnsbl.manitu.net ; rbl=ix.dnsbl.manitu.net
id=RBL02 ; action=REJECT listed on zen.spamhaus.org ; rbl=zen.spamhaus.org/127.0.0.[2−8]/1200
id=RBL03 ; action=REJECT listed on too many RBLs ; rblcount=2 ; rbl=bl.spamcop.net, list.dsbl.org, dnsbl.sorbs.net
id=RBL04 ; action=REJECT combined RBL+RHSBL check ; rbl=bl.spamcop.net ; rhsbl=rhsbl.ahbl.org, rhsbl.sorbs.net
## Message size (requires message_size_limit to be set to 30000000)
# 1. 30MB for systems in *.customer1.tld
# 2. 20MB for SASL user joejob
# 3. 10MB default
id=SZ001; protocol_state==END−OF−MESSAGE; action=DUNNO; size<=30000000 ; client_name=\.customer1.tld$
id=SZ002; protocol_state==END−OF−MESSAGE; action=DUNNO; size<=20000000 ; sasl_username==joejob
id=SZ002; protocol_state==END−OF−MESSAGE; action=DUNNO; size<=10000000
id=SZ100; protocol_state==END−OF−MESSAGE; action=REJECT message too large
## Selective Greylisting
##
## Note that postfwd does not include greylisting. This setup requires a running postgrey service
## at port 10031 and the following postfix restriction class in your main.cf:
##
## smtpd_restriction_classes = check_postgrey, ...
## check_postgrey = check_policy_service inet:127.0.0.1:10031
#
# 1. if listed on zen.spamhaus.org with results 127.0.0.10 or .11, dns cache timeout 1200s
# 2. Client has no rDNS
# 3. Client comes from several dialin domains
id=GR001; action=check_postgrey ; rbl=dul.dnsbl.sorbs.net, zen.spamhaus.org/127.0.0.1[01]/1200
id=GR002; action=check_postgrey ; client_name=ˆunknown$
id=GR003; action=check_postgrey ; client_name=\.(t−ipconnect|alicedsl|ish)\.de$
## Date Time
date=24.12.2007−26.12.2007 ; action=450 4.7.1 office closed during christmas
time=04:00:00−05:00:00 ; action=450 4.7.1 maintenance ongoing, try again later
time=−07:00:00 ; sasl_username=jim ; action=450 4.7.1 to early for you, jim
time=22:00:00− ; sasl_username=jim ; action=450 4.7.1 to late now, jim
months=−Apr ; action=450 4.7.1 see you in may
days=!!Mon−Fri ; action=check_postgrey
## Usage of jump
# The following allows a message size of 30MB for different
# users/clients while others will only have 10MB.
id=R001 ; action=jump(R100) ; sasl_username=ˆ(Alice|Bob|Jane)$
id=R002 ; action=jump(R100) ; client_address=192.168.1.0/24
id=R003 ; action=jump(R100) ; ccert_fingerprint=AA:BB:CC:DD:...
id=R004 ; action=jump(R100) ; ccert_fingerprint=AF:BE:CD:DC:...
id=R005 ; action=jump(R100) ; ccert_fingerprint=DD:CC:BB:DD:...
id=R099 ; protocol_state==END−OF−MESSAGE; action=REJECT message too big (max. 10MB); size=10000000
id=R100 ; protocol_state==END−OF−MESSAGE; action=REJECT message too big (max. 30MB); size=30000000
## Usage of score
# The following rejects a mail, if the client
# − is listed on 1 RBL and 1 RHSBL
# − is listed in 1 RBL or 1 RHSBL and has no correct rDNS
# − other clients without correct rDNS will be greylist−checked
# − some whitelists are used to lower the score
id=S01 ; score=2.6 ; action=check_postgrey
id=S02 ; score=5.0 ; action=REJECT postfwd score too high
id=R00 ; action=score(−1.0) ; rbl=exemptions.ahbl.org,list.dnswl.org,query.bondedsender.org,spf.trusted−forwarder.org
id=R01 ; action=score(2.5) ; rbl=bl.spamcop.net, list.dsbl.org, dnsbl.sorbs.net
id=R02 ; action=score(2.5) ; rhsbl=rhsbl.ahbl.org, rhsbl.sorbs.net
id=N01 ; action=score(−0.2) ; client_name==$$helo_name
id=N02 ; action=score(2.7) ; client_name=ˆunknown$
...
## Usage of rate and size
# The following temporary rejects requests from "unknown" clients, if they
# 1. exceeded 30 requests per hour or
# 2. tried to send more than 1.5mb within 10 minutes
id=RATE01 ; client_name==unknown ; protocol_state==RCPT
action=rate(client_address/30/3600/450 4.7.1 sorry, max 30 requests per hour)
id=SIZE01 ; client_name==unknown ; protocol_state==END−OF−MESSAGE
action=size(client_address/1572864/600/450 4.7.1 sorry, max 1.5mb per 10 minutes)
## Macros
# definition
&&RBLS { rbl=zen.spamhaus.org,list.dsbl.org,bl.spamcop.net,dnsbl.sorbs.net,ix.dnsbl.manitu.net; };
&&GONOW { action=REJECT your request caused our spam detection policy to reject this message. More info at http://www.domain.local; };
# rules
&&GONOW ; &&RBLS ; client_name=ˆunknown$
&&GONOW ; &&RBLS ; client_name=(\d+[\.−_]){4}
&&GONOW ; &&RBLS ; client_name=[\.−_](adsl|dynamic|ppp|)[\.−_]
## Groups
# definition
&&RBLS{
rbl=zen.spamhaus.org
rbl=list.dsbl.org
rbl=bl.spamcop.net
rbl=dnsbl.sorbs.net
rbl=ix.dnsbl.manitu.net
};
&&RHSBLS{
...
};
&&DYNAMIC{
client_name==unknown
client_name˜=(\d+[\.−_]){4}
client_name˜=[\.−_](adsl|dynamic|ppp|)[\.−_]
...
};
&&BAD_HELO{
helo_name==my.name.tld
helo_name˜=ˆ([ˆ\.]+)$
helo_name˜=\.(local|lan)$
...
};
&&MAINTENANCE{
date=15.01.2007
date=15.04.2007
date=15.07.2007
date=15.10.2007
time=03:00:00 − 04:00:00
};
# rules
id=COMBINED ; &&RBLS ; &&DYNAMIC ; action=REJECT dynamic client and listed on RBL
id=MAINTENANCE ; &&MAINTENANCE ; action=DEFER maintenance time − please try again later
# now with the set() command, note that long item
# lists don't have to be compared twice
id=RBL01 ; &&RBLS ; action=set(HIT_rbls=1)
id=HELO01 ; &&BAD_HELO ; action=set(HIT_helo=1)
id=DYNA01 ; &&DYNAMIC ; action=set(HIT_dyna=1)
id=REJECT01 ; HIT_rbls==1 ; HIT_helo==1 ; action=REJECT please see http://some.org/info?reject=01 for more info
id=REJECT02 ; HIT_rbls==1 ; HIT_dyna==1 ; action=REJECT please see http://some.org/info?reject=02 for more info
id=REJECT03 ; HIT_helo==1 ; HIT_dyna==1 ; action=REJECT please see http://some.org/info?reject=03 for more info
## combined with enhanced rbl features
#
id=RBL01 ; rhsblcount=all ; rblcount=all ; &&RBLS ; &&RHSBLS
action=set(HIT_dnsbls=$$rhsblcount,HIT_dnsbls+=$$rblcount,HIT_dnstxt=$$dnsbltext)
id=RBL02 ; HIT_dnsbls>=2 ; action=554 5.7.1 blocked using $$HIT_dnsbls DNSBLs [INFO: $$HIT_dnstxt]

PARSER

Configuration

The postfwd3 ruleset can be specified at the commandline (−r option) or be read from files (−f). The order of your arguments will be kept. You should check the parser with the −C | −−showconfig switch at the command line before applying a new config. The following call:

postfwd3 −−showconfig \
−r "id=TEST; recipient_count=100; action=WARN mail with 100+ recipients" \
−f /etc/postfwd.cf \
−r "id=DEFAULT; action=dunno";

will produce the following output:

Rule 0: id−>"TEST" action−>"WARN mail with 100+ recipients"; recipient_count−>"100"
...
... <content of /etc/postfwd.cf> ...
...
Rule <n>: id−>"DEFAULT" action−>"dunno"

Multiple items of the same type will be added to lists (see the " ITEMS" section for more info):

postfwd3 −−showconfig \
−r "client_address=192.168.1.0/24; client_address=172.16.26.32; action=dunno"

will result in:

Rule 0: id−>"R−0"; action−>"dunno"; client_address−>"192.168.1.0/24, 172.16.26.32"

Macros are evaluated at configuration stage, which means that

postfwd3 −−showconfig \
−r "&&RBLS { rbl=bl.spamcop.net; client_name=ˆunknown$; };" \
−r "id=RBL001; &&RBLS; action=REJECT listed on spamcop and bad rdns";

will result in:

Rule 0: id−>"RBL001"; action−>"REJECT listed on spamcop and bad rdns"; rbl−>"bl.spamcop.net"; client_name−>"ˆunknown$"

Request processing

When a policy delegation request arrives it will be compared against postfwd‘s ruleset. To inspect the processing in detail you should increase verbority using use the "−v" or "−vv" switch. "−L" redirects log messages to stdout.

Keeping the order of the ruleset in general, items will be compared in random order, which basically means that

id=R001; action=dunno; client_address=192.168.1.1; [email protected]

equals to

id=R001; [email protected]; client_address=192.168.1.1; action=dunno

Lists will be evaluated in the specified order. This allows to place faster expressions at first:

postfwd3 −vv −−cmd −r "id=RBL001; rbl=localrbl.local zen.spamhaus.org; action=REJECT" /some/where/request.sample

produces the following

[LOGS info]: compare rbl: "remotehost.remote.net[68.10.1.7]" −> "localrbl.local"
[LOGS info]: count1 rbl: "2" −> "0"
[LOGS info]: query rbl: localrbl.local 7.1.10.68 (7.1.10.68.localrbl.local)
[LOGS info]: count2 rbl: "2" −> "0"
[LOGS info]: match rbl: FALSE
[LOGS info]: compare rbl: "remotehost.remote.net[68.10.1.7]" −> "zen.spamhaus.org"
[LOGS info]: count1 rbl: "2" −> "0"
[LOGS info]: query rbl: zen.spamhaus.org 7.1.10.68 (7.1.10.68.zen.spamhaus.org)
[LOGS info]: count2 rbl: "2" −> "0"
[LOGS info]: match rbl: FALSE
[LOGS info]: Action: dunno

The negation operator !!(<value>) has the highest priority and therefore will be evaluated first. Then variable substitutions are performed:

postfwd3 −vv −−cmd −r "id=TEST; action=REJECT; client_name=!!($$heloname)" /some/where/request.sample

will give

[LOGS info]: compare client_name: "unknown" −> "!!($$helo_name)"
[LOGS info]: negate client_name: "unknown" −> "$$helo_name"
[LOGS info]: substitute client_name: "unknown" −> "english−breakfast.cloud8.net"
[LOGS info]: match client_name: TRUE
[LOGS info]: Action: REJECT

Ruleset evaluation

A rule hits when all items (or at least one element of a list for each item) have matched. As soon as one item (or all elements of a list) fails to compare against the request attribute the parser will jump to the next rule in the postfwd3 ruleset.

If a rule matches, there are two options:

* Rule returns postfix action (dunno, reject, ...) The parser stops rule processing and returns the action to postfix. Other rules will not be evaluated.

* Rule returns postfwd3 action (jump(), note(), ...) The parser evaluates the given action and continues with the next rule (except for the jump() or quit() actions − please see the " ACTIONS" section for more information). Nothing will be sent to postfix.

If no rule has matched and the end of the ruleset is reached postfwd3 will return dunno without logging anything unless in verbose mode. You may place a last catch-all rule to change that behaviour:

... <your rules> ...
id=DEFAULT ; action=dunno

will log any request that passes the ruleset without having hit a prior rule.

SETTINGS

Since version postfwd3 2.00−pre6 the program settings can be retrieved from a file. The information must be parseable by perl eval() function. Comments are allowed:

# example settings for postfwd3
{
# enable verbose logging
verbose => 1,
# user and group for postfwd
base => {
group => 'postfw',
user => 'postfw'
},
# server settings
server => {
proto => 'tcp',
host => '127.0.0.1',
port => '10099'
}
}

postfwd3 can also export the program settings in that format using Data::Dumper.

# show configuration
postfwd3 −−showsettings
# save configuration to file
postfwd3 −−savesettings=/path/to/file
# read configuration from file
postfwd3 −−loadsettings=/path/to/file

Multiple usage of −−loadsettings or the short form −F is allowed. The order will be kept. Commandline arguments override the settings retrieved from a file.

# load base settings, override with node settings and set port and verbose logging
postfwd3 −v −p 10050 −F /path/to/basefile −F /path/to/nodefile

Samples for settings files are distributed in the etc/−folder of the postfwd3 tarball.

DEBUGGING

To debug special steps of the parser the ’−−debug’ switch takes a list of debug classes. Since postfwd3 2.00 the list of available debug classes can be retrieved by running:

postfwd3 −−debugclasses

INTEGRATION

Integration via daemon mode

The common way to use postfwd3 is to start it as daemon, listening at a specified tcp port. postfwd3 will spawn multiple child processes which communicate with a parent cache. This is the prefered way to use postfwd3 in high volume environments. Start postfwd3 with the following parameters:

postfwd3 −d −f /etc/postfwd.cf −i 127.0.0.1 −p 10045 −u nobody −g nobody −S

For efficient caching you should check if you can use the options −−cacheid, −−cache−rdomain−only, −−cache−no−sender and −−cache−no−size.

Now check your syslogs (default facility "mail") for a line like:

Aug 9 23:00:24 mail postfwd[5158]: postfwd3 n.nn ready for input

and use ‘netstat −an|grep 10045‘ to check for something like

tcp 0 0 127.0.0.1:10045 0.0.0.0:* LISTEN

If everything works, open your postfix main.cf and insert the following

127.0.0.1:10045_time_limit = 3600 <−−− integration
smtpd_recipient_restrictions = permit_mynetworks <−−− recommended
reject_unauth_destination <−−− recommended
check_policy_service inet:127.0.0.1:10045 <−−− integration

Reload your configuration with ‘postfix reload‘ and watch your logs. In it works you should see lines like the following in your mail log:

Aug 9 23:01:24 mail postfwd[5158]: rule=22, id=ML_POSTFIX, client=english−breakfast.cloud9.net[168.100.1.7], sender=owner−postfix−[email protected], [email protected], helo=english−breakfast.cloud9.net, proto=ESMTP, state=RCPT, action=dunno

If you want to check for size or rcpt_count items you must integrate postfwd3 in smtp_data_restrictions or smtpd_end_of_data_restrictions. Of course you can also specify a restriction class and use it in your access tables. First create a file /etc/postfix/policy containing:

domain1.local postfwdcheck
domain2.local postfwdcheck
...

Then postmap that file (‘postmap hash:/etc/postfix/policy‘), open your main.cf and enter

# Restriction Classes
smtpd_restriction_classes = postfwdcheck, <some more>... <−−− integration
postfwdcheck = check_policy_service inet:127.0.0.1:10045 <−−− integration
127.0.0.1:10045_time_limit = 3600 <−−− integration
smtpd_recipient_restrictions = permit_mynetworks, <−−− recommended
reject_unauth_destination, <−−− recommended
... <−−− optional
check_recipient_access hash:/etc/postfix/policy, <−−− integration
... <−−− optional

Reload postfix and watch your logs.

Integration via docker

postfwd can be run in a docker container. The relevant options are −−nodaemon and −−stdout. More information can be found in the included doc/docker.html or at <http://postfwd.org/docker>.

TESTING

First you have to create a ruleset (see Configuration section). Check it with

postfwd3 −f /etc/postfwd.cf −C

There is an example policy request distributed with postfwd, called ’request.sample’. Simply change it to meet your requirements and use

postfwd3 −−cmd −f /etc/postfwd.cf request.sample

You should get an answer like

action=<whateveryouconfigured>

For network tests I use netcat:

nc 127.0.0.1 10045 <request.sample

to send a request to postfwd. If you receive nothing, make sure that postfwd3 is running and listening on the specified network settings.

PERFORMANCE

Some of these proposals might not match your environment. Please check your requirements and test new options carefully!

− use caching options
− use the correct match operator ==, <=, >=
− use ˆ and/or $ in regular expressions
− use item lists (faster than single rules)
− use set() action on repeated item lists
− use jumps and rate limits
− use a pre−lookup rule for rbl/rhsbls with empty note() action

DONATIONS

Development, testing and hosting of postfwd consumes time and ressources. It is and will stay free software (see " LICENSE" below). If you want to support this, consider a donation at https://www.paypal.me/postfwd.

LICENSE

postfwd3 is free software and released under BSD license, which basically means that you can do what you want as long as you keep the copyright notice:

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the
distribution.
* Neither the name of the authors nor the names of his contributors
may be used to endorse or promote products derived from this
software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY ME ‘‘ AS IS ’’ AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES ( INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES ; LOSS OF USE, DATA, OR PROFITS ; OR BUSINESS INTERRUPTION ) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT ( INCLUDING NEGLIGENCE OR OTHERWISE ) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

AUTHOR

Jan Peter Kessler <info ( AT ) postfwd ( DOT ) org>. Let me know, if you have any suggestions.

Updated 2024-01-29 - jenkler.se | uex.se