postfwd - postfix firewall daemon

- NAME
- SYNOPSIS
- DESCRIPTION

- INTRODUCTION
- CONFIGURATION
- ITEMS
- ACTIONS
- MACROS/ACLS
- COMMAND LINE
- REFRESH
- EXAMPLES
- PARSER
- INTEGRATION
- TESTING
- SEE ALSO

- LICENSE
- AUTHOR

# NAME

postfwd - postfix firewall daemon

# SYNOPSIS

postfwd [OPTIONS] SOURCE1, SOURCE2, ...

            Ruleset: (at least one, multiple use is allowed):
            -f, --file <file>         reads rules from <file>
            -r, --rule <rule>         adds <rule> to config

            Scoring:
            -s, --scores <v>=<r>      returns <r> when score exceeds <v>

            Networking:
            -d, --daemon              run postfwd as daemon
            -i, --interface <dev>     listen on interface <dev>
            -p, --port <port>         listen on port <port>
            -u, --user <name>         set uid to user <name>
            -g, --group <name>        set gid to group <name>
            -R, --chroot <path>       chroot the daemon to <path>
            -l, --logname <label>     label for syslog messages
                --pidfile <path>      create pidfile under <path>

            optional:
            -v, --verbose             verbose logging, use twice (-vv) to increase level
            -c, --cache <int>         sets the request-cache timeout to <int> seconds
                --cache-no-size       ignores size attribute for caching
                --cache-rdomain-only  ignores localpart of recipient address in cache
            -S, --summary <int>       show some usage statistics every <int> seconds
            -L, --stdoutlog           redirect syslog messages to stdout
            -t, --test                testing, always returns "dunno"
            -n, --nodns               disable dns
            -I, --instantcfg          re-reads rulefiles for every new request

            informational (use only at command-line!):
            -C, --showconfig          shows config, -v for verbose
            -P, --perfmon             no syslogging, no stdout
            -V, --version             shows program version
            -h, --help                shows usage
            -m, --manual              shows program manual

# DESCRIPTION

## INTRODUCTION

postfwd 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).

postfwd 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, 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 ; sender=no@bad.local ; action=REJECT

This will deny all mail from 192.168.1.1 with envelope sender no@bad.local. 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 ; sender=no@bad.local

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 ; sender=no@bad.local

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.

Rules can span multiple lines by adding a trailing backslash ``\'' character:

            id=R_001 ;  client_address=192.168.1.0/24; sender=no@bad.local; \
                        action=REJECT please use your relay from there

## 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

            score                   - when the specified score is hit (see ACTIONS section)
                                      the specified action will be returned to postfix
                                      scores are set global until redefined!

            rbl, rhsbl              - query the specified RBLs/RHSBLs, possible values are:
                                      <name>[/<reply>/<maxcache>, <name>/<reply>/<maxcache>]

            rblcount, rhsblcount    - minimum RBL/RHSBL hitcounts to match if not specified
                                      a single RBL/RHSBL hit will match the rbl/rhsbl items

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)
            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
            # ------------------------------
            # 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
            sender=foo@bar.tld                      mask = PCRE
            recipient=bar@foo.tld                   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_DATA 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 currently have to be unique:

            id, minimum and maximum values, rblcount and rhsblcount

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

            id=TLS001 ;  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=!!( (bob|alice) )  ;  action=REJECT who is that?

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

            id=R-003 ;  client_name = !! $$helo_name      ;  action=REJECT helo does not match DNS
            # or
            id=R-003 ;  client_name = !!($$(helo_name))   ;  action=REJECT 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.

## ACTIONS

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.

postfwd 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 ; sender=@domain.local     # sender is ok
            action=reject                           # default deny

postfwd actions

postfwd 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!

            score (<score>)
            the request's score will be increased by the specified <score>,
            which must be a floating point value. 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=REJECT). negative values are allowed.
            Anything else than +/-nnnn.nn will be ignored.

            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.

            quit (<code>)
            terminates the program with the given exit-code. postfix doesn`t
            like that too much, so use it with care.

## 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=^unknown$                         ; 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=^unknown$
            &&GONOW ;  &&RBLS ;  client_name=(\d+[\.-_]){4}
            &&GONOW ;  &&RBLS ;  client_name=[\.-_](adsl|dynamic|ppp|)[\.-_]

Macros can contain macros, too:

            # definition (note the trailing "\" characters)
            &&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=^unknown$ ;                         \
                    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.

## COMMAND LINE

Ruleset

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

            -f, --file <file>
            Reads rules from <file>. Please see the CONFIGURATION section
            below for more information.

            -r, --rule <rule>
            Adds <rule> to ruleset. Remember that you might have to quote
            strings that contain whitespaces or shell characters.

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:

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

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

Networking

postfwd 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
            postfwd will run as daemon and listen on the network for incoming
            queries (default 127.0.0.1:10040).

            -i, --interface <dev>
            Bind postfwd to the specified interface (default 127.0.0.1).

            -p, --port <port>
            postfwd listens on the specified port (default tcp/10040).

            -u, --user <name>
            Changes real and effective user to <name>.

            -g, --group <name>
            Changes real and effective group to <name>.

            -R, --chroot <path>
            Chroot the process to the specified path.
            Test this before using - you might need some libs there.

            -l, --logname <label>
            Labels the syslog messages. Useful when running multiple
            instances of postfwd.

            --pidfile <path>
            The process id will be saved in the specified file.

Optional arguments

These parameters influence the way postfwd 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>
            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-rdomain-only
            This will strip the localpart of the recipient's address before filling the
            cache. This may considerably increase cache-hit rates.

            -S, --summary <int>
            Shows some usage statistics (program uptime, request counter, matching rules)
            every <int> seconds (default: 600). This option is included by the -v switch.

            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
            ...

            -L, --stdoutlog
            Redirects all syslog messages to stdout for debugging. Never use this with postfix!

            -t, --test
            In test mode postfwd 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.

            -I, --instantcfg
            The config files, specified by -f will be re-read for every request
            postfwd 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.

Informational arguments

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

            -C, --showconfig
            Displays the current ruleset. Use -v for verbose output.

            -P, --perfmon
            This option turns of any syslogging and output. It is included
            for performance testing.

            -V, --version
            Displays the program version.

            -h, --help
            Shows program usage.

            -m, --manual
            Displays the program manual.

## REFRESH

In daemon mode postfwd 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 postfwd 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 600s)
            # 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; action=REJECT message too large ; size=30000000 ; client_name=\.customer1.tld$
            id=SZ002; action=REJECT message too large ; size=20000000 ; sasl_username=^joejob$
            id=SZ003; action=REJECT message too large ; size=10000000

            ## Selective Greylisting
            # 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=greylisting ; rbl=dul.dnsbl.sorbs.net, zen.spamhaus.org/127.0.0.1[01]/1200
            id=GR002; action=greylisting ; client_name=^unknown$
            id=GR003; action=greylisting ; 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

            ## 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=^(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 ; action=REJECT message too big (max. 10MB); size=10000000
            id=R100 ; 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=greylisting
            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(2.7)      ; client_name=^unknown$
            ...

            ## 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=^unknown$
            &&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 ;       \
            };
            &&DYNAMIC { \
                    client_name=^unknown$ ;                         \
                    client_name=(\d+[\.-_]){4} ;                    \
                    client_name=[\.-_](adsl|dynamic|ppp|)[\.-_] ;   \
            };
            &&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

## PARSER

Configuration

The postfwd 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:

            postfwd --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):

            postfwd --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

            postfwd --showconfig \
                    -r "&&RBLS { rbl=bl.spamcop.net; client_name=^unknown$; };" \
                    -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->"^unknown$"

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; sender=bob@alice.local

equals to

            id=R001; sender=bob@alice.local; client_address=192.168.1.1; action=dunno

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

            postfwd -vv -L -r "id=RBL001; rbl=localrbl.local zen.spamhaus.org; action=REJECT" /root/request.small

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:

            postfwd -vv -L -r "id=TEST; action=REJECT; client_name=!!($$heloname)" /root/request.small

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 postfwd 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 postfwd 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 postfwd will return dunno without logging anything unless in verbose mode. You may simply place a last `catch-allī 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.

## INTEGRATION

Integration via daemon mode

The common way to use postfwd is to start it as daemon, listening at a specified tcp port. As postfwd will run in a single instance (multiplexing mode), it will take most benefit of it`s internal caching in that case. Start postfwd with the following parameters:

            postfwd -d -f /etc/postfwd.cf -i 127.0.0.1 -p 10040 -u nobody -g nobody -S

For efficient caching you should check if you can use the options --cache-rdomain-only and --cache-no-size.

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

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

and use `netstat -an|grep 10040` to check for something like

            tcp  0  0  127.0.0.1:10040  0.0.0.0:*  LISTEN

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

            127.0.0.1:10040_time_limit      = 3600                                          <--- integration
            smtpd_recipient_restrictions    = permit_mynetworks                             <--- recommended
                                              reject_unauth_destination                     <--- recommended
                                              check_policy_service inet:127.0.0.1:10040     <--- 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-users@postfix.tld, recipient=someone@domain.local, 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 postfwd 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:127.0.0.1:10040             <--- integration

            127.0.0.1:10040_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 xinetd

There might be several reasons for you to use postfwd via a tcp wrapper package like xinetd (see http://www.xinetd.org/). I won`t discuss that here. If you plan to do so, just add the following line to your /etc/services file:

            # postfwd port
            postfwd     10040/tcp

Then create a file '/etc/xinetd.d/postfwd':

            {
                    interface       = 127.0.0.1
                    socket_type     = stream
                    protocol        = tcp
                    wait            = no
                    user            = nobody
                    server          = /usr/local/bin/postfwd
                    server_args     = -f /etc/postfwd.cf
                    disable         = no
            }

and restart the xinetd daemon (usually a SIGHUP should be fine). If you experience problems you might want to check your system's log for xinetd errors like ``socket already in use''.

The integration with postfix is similar to the Integration via daemon mode section above. Reload postfix and watch your logs to see if everything works.

## TESTING

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

            postfwd -f /etc/postfwd.cf -C

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

            postfwd -f /etc/postfwd.cf <request.small

You should get an answer like

            action=<whateveryouconfigured>

For network tests I use netcat:

            nc 127.0.0.1 10040 <request.small

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

## SEE ALSO

See http://www.postfix.org/SMTPD_POLICY_README.html for a description of how Postfix policy servers work.

# LICENSE

postfwd 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:

Copyright (c) 2007, Jan Peter Kessler All rights reserved.

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.