SnertSoft: We Serve Your Server

milter-siq/0.21
«He shoots! He scores!»


Description & Usage ° Installation & Notes ° License & Support

WARNING

THIS IS MAIL FILTERING SOFTWARE AND WILL BLOCK MAIL THAT FAILS TO PASS A GIVEN SET OF TESTS. SNERTSOFT AND THE AUTHOR DO NOT ACCEPT ANY RESPONSIBLITY FOR MAIL REJECTED OR POSSIBLE LOSS OF BUSINESSS THROUGH THE USE OF THIS SOFTWARE. BY INSTALLING THIS SOFTWARE THE CLIENT UNDERSTANDS AND ACCEPTS THE RISKS INVOLVED.

Description

This Sendmail mail filter will tag, reject, and/or discard email according to a score returned by a SIQ Protocol server that grades IP/domain pairs based on the server's reputation criteria.

Third-party SIQ servers can provide facts about the reputation of an outbound mail server IP and/or MAIL FROM: domain including: stability, longevity, identifiability, SPF match, RHS type grouping, verified PTR record matching, et al. One such service is already available from Outbound Index. Please check with the service(s) available before using them as some require registration before they will answer queries.

There is also the OpenSIQServer project for those who want to start their own reputation service using SIQ (see also BLS Consu lting for more info about OpenSIQServer).

The following headers are always added:

X-milter-siq-Pass      Boolean "YES" or "NO" as to whether the message is acceptable or not according to the mail server's SIQ score threshold of acceptance.
X-milter-siq-Report The report summary states whether the message is acceptable, the query made, which SIQ server responded, and the server's response score and text. The score can be -1 for unknown or a value between 0 and 100.
X-Scanned-By This is a trace header with a mail filter name, version number, host name, host IP, and timestamp. There may be multiple instances of this header, one for each participating mail scanner from one or more mail servers, in which case they represent the most recent to oldest, similar to the way Received: headers are added. This ordering is handled by Sendmail and not configurable.

Usage

milter-siq [options ...][arguments ...]

Options can be expressed in four different ways. Boolean options are expressed as +option or -option to turn the option on or off respectively. Options that required a value are expressed as option=value or option+=value for appending to a value list. Note that the +option and -option syntax are equivalent to option=1 and option=0 respectively. Option names are case insensitive.

Some options, like +help or -help, are treated as immediate actions or commands. Unknown options are ignored. The first command-line argument is that which does not adhere to the above option syntax. The special command-line argument -- can be used to explicitly signal an end to the list of options.

The default options, as shown below, can be altered by specifying them on the command-line or within an option file, which simply contains command-line options one or more per line and/or on multiple lines. Comments are allowed and are denoted by a line starting with a hash (#) character. If the file option is defined and not empty, then it is parsed first followed by the command-line options.

Note that there may be additional options that are listed in the option summary given by +help or -help that are not described here.

access-db=/etc/mail/access.db
The type and location of the read-only access key-value map. It provides a centralised means to black and white list hosts, domains, mail addresses, etc. The following methods are supported:
text!/path/map.txtR/O text file, memory hash
/path/map.dbBerkeley DB hash format
db!/path/map.dbBerkeley DB hash format
db!btree!/path/map.dbBerkeley DB btree format
sql!/path/databaseAn SQLite3 database
socketmap!host:portSendmail style socket-map
socketmap!/path/local/socketSendmail style socket-map
socketmap!123.45.67.89:portSendmail style socket-map
socketmap![2001:0DB8::1234]:portSendmail style socket-map

If :port is omitted, the default is 7953.

The access-db contains key-value pairs. Lookups are performed from most to least specific, stopping on the first entry found. Keys are case-insensitive.

An IPv4 lookup is repeated several times reducing the IP address by one octet from right to left until a match is found.

tag:192.0.2.9
tag:192.0.2
tag:192.0
tag:192

An IPv6 lookup is repeated several times reducing the IP address by one 16-bit word from right to left until a match is found.

tag:2001:0DB8:0:0:0:0:1234:5678
tag:2001:0DB8:0:0:0:0:1234
tag:2001:0DB8:0:0:0:0
tag:2001:0DB8:0:0:0
tag:2001:0DB8:0:0
tag:2001:0DB8:0:0
tag:2001:0DB8:0
tag:2001:0DB8
tag:2001

A domain lookup is repeated several times reducing the domain by one label from left to right until a match is found.

tag:[ipv6:2001:0DB8::1234:5678]
tag:[192.0.2.9]
tag:sub.domain.tld
tag:domain.tld
tag:tld
tag:

An email lookup is similar to a domain lookup, the exact address is first tried, then the address's domain, and finally the local part of the address.

tag:account@sub.domain.tld
tag:sub.domain.tld
tag:domain.tld
tag:tld
tag:account@
tag:

If a key is found and is a milter specific tag (ie. milter-siq-Connect, milter-siq-From, milter-siq-Auth, milter-siq-To), then the value is processed as a pattern list and the result returned. The Sendmail variants cannot have a pattern list. A pattern list is a whitespace separated list of pattern-action pairs followed by an optional default action. The supported patterns are:

[network/cidr]actionClassless Inter-Domain Routing
!pattern!actionSimple fast text matching.
/regex/actionPOSIX Extended Regular Expressions

The CIDR will only ever match for IP address related lookups.

A !pattern! uses an astrisk (*) for a wildcard, scanning over zero or more characters; a question-mark (?) matches any single character; a backslash followed by any character treats it as a literal (it loses any special meaning).

!abc!exact match for 'abc'
!abc*!match 'abc' at start of string
!*abc!match 'abc' at the end of string
!abc*def!match 'abc' at the start and match 'def' at the end, maybe with stuff in between.
!*abc*def*!find 'abc', then find 'def'

For black-white lookups, the following actions are recognised: OK or RELAY (white list), REJECT or ERROR (black list), DISCARD (accept & discard), SKIP or DUNNO (stop lookup, no result), and NEXT (opposite of SKIP, resume lookup). Its possible to specify an empty action after a pattern, which is treated like SKIP returning an undefined result. Other options may specify other actions.

Below is a list of supported tags. Other options may specify additional tags.

  
milter-siq-Connect:client-ip  value   § Can be a pattern list.
Connect:client-ip  value
client-ip  value
 
milter-siq-Connect:[client-ip]  value   § Can be a pattern list.
milter-siq-Connect:client-domain  value   § Can be a pattern list.
milter-siq-Connect:  value   § Can be a pattern list.
Connect:[client-ip] value
Connect:client-domain value
[client-ip] value
client-domain value
 
All mail sent by a connecting client-ip, unresolved client-ip address or IP addresses that resolve to a client-domain are black or white-listed. These allows you to white-list your network for mail sent internally and off-site, or connections from outside networks. Note that Sendmail also has special semantics for Connect: and untagged forms.
 
milter-siq-From:sender-address  value   § Can be a pattern list.
milter-siq-From:sender-domain  value   § Can be a pattern list.
milter-siq-From:sender@  value   § Can be a pattern list.
milter-siq-From:  value   § Can be a pattern list.
From:sender-address value
From:sender-domain value
From:sender@ value
sender-address value
sender-domain value
sender@ value
 
All mail from the sender-address, sender-domain, or that begins with sender is black or white-listed. In the case of a +detailed email address, the left hand side of the +detail is used for the sender@ lookup. Note that Sendmail also has special semantics for From: and untagged forms.
 
milter-siq-Auth:auth_authenvalue   § Can be a pattern list.
milter-siq-Auth:value   § Can be a pattern list.
 
All mail from the authenticated sender, as given by sendmail's {auth_authen} macro, is black or white-listed. The string searched by the pattern list will be the sender-address. The empty form of milter-siq-Auth: allows for a milter specific default only when {auth_authen} is defined.
 
milter-siq-To:recipient-address  value   § Can be a pattern list.
milter-siq-To:recipient-domain  value   § Can be a pattern list.
milter-siq-To:recipient@  value   § Can be a pattern list.
milter-siq-To:  value   § Can be a pattern list.
Spam:recipient-address value   * (FRIEND or HATER are recognised)
Spam:recipient-domain value   * (FRIEND or HATER are recognised)
Spam:recipient@ value   * (FRIEND or HATER are recognised)
To:recipient-address value
To:recipient-domain value
To:recipient@ value
recipient-address value
recipient-domain value
recipient@ value
 
All mail to the recipient-address, recipient-domain, or that begins with recipient is black or white-listed. In the case of a +detailed email address, the left hand side of the +detail is used for the recipient@ lookup. Note that Sendmail also has special semantics for Spam:, To:, and untagged forms.
 

The milter-siq-Connect:, milter-siq-From:, and milter-siq-To: tags provide a milter specific means to override the Sendmail variants. For example, you normally white list your local network through any and all milters, but on the odd occasion you might want to actually scan mail from inside going out, without removing the Connect: tag that allows Sendmail to relay for your network or white listing for other milters. So for example if you have Sendmail tags like:

To:mx.example.comRELAY

You might have to add milter specific overrides in order to make sure the mail still gets filtered:

To:mx.example.comRELAY
milter-siq-To:mx.example.comSKIP

Some additional examples:

milter-siq-Connect:80.94 [80.94.96.0/20]OK  REJECT
 
Accept connections from the netblock 80.94.96.0/20 (80.94.96.0 through to 80.94.111.255) and rejecting anything else in 80.94.0.0/16.
 
milter-siq-Connect:192.0.2 /^192\.0\.2\.8[0-9]/OK  REJECT
 
Accept connections from 192.0.2.80 through to 192.0.2.89, reject everything else in 192.0.2.0/24.
 
milter-siq-From:example.com /^john@.+/OK  /^fred\+.*@.*/OK  REJECT
 
Accept mail from <john@example.com> and <fred@example.com> when fred's address contains a plus-detail in the address. Reject everything else from example.com.
 
milter-siq-To:example.net !*+*@*!REJECT  !*.smith@*!REJECT  /^[0-9].*/REJECT
 
Reject mail to example.net using a plus-detail address or to any user who's last name is "smith" or addresses starting with a digit. No default given, so B/W processing would continue.
 

Normally when the access.db lookup matches a milter tag, then the value pattern list is processed and there are no further access.db lookups. The NEXT action allows the access.db lookups to resume and is effectively the opposite of SKIP. Consider the following examples:

milter-siq-From:com
From:com
/@com/REJECT  NEXT
OK
 
Reject mail from places like compaq.com or com.com if the pattern matches, but resume the access.db lookups otherwise.
 
milter-siq-From:aol.com  
From:fred@aol.com  
/^[a-zA-Z0-9!#$&'*+=?^_`{|}~.-]{3,16}@aol.com$/NEXT  REJECT
OK
 
AOL local parts are between 3 and 16 characters long and can contain dots and RFC 2822 atext characters except % and /. The NEXT used above allows one simple regex to validate the format of the address and proceed to lookup white listed and/or black listed addresses.
 
cache-file=/var/db/milter-limit.db
The file path used for BDB or flatfile cache types.
cache-gc-frequency=120
This option specifies the cache garbage collection frequency, which is based on the number of SMTP connections (not messages) handled by the milter. Every N connections, the cache is traversed to remove expired entries.
cache-type=bdb
The cache type can be one of: bdb, flatfile, hash.
+daemon
Start as a background daemon or foreground application.
file=/etc/mail/milter-siq.cf
Read the option file before command line options. This option is set by default. To disable the use of an option file, simply say file=''
-help or +help
Write the option summary to standard output and exit. The output is suitable for use as an option file.
milter-socket=unix:/var/run/milter/milter-siq.socket
A socket specifier used to communicate between Sendmail and milter-siq. Typically a unix named socket or a host:port. This value must match the value specified for the INPUT_MAIL_FILTER() macro in the sendmail.mc file. The accepted syntax is:
{unix|local}:/path/to/file
A named pipe. (default)
inet:port@{hostname|ip-address}
An IPV4 socket.
inet6:port@{hostname|ip-address}
An IPV6 socket.
milter-timeout=7210
The sendmail/milter I/O timeout in seconds.
pid-file=/var/run/milter/milter-siq.pid
The file path of where to save the process-id.
-quit or +quit
Quit an already running instance of the milter and exit. This is equivalent to: kill -QUIT `cat /var/run/milter/milter-siq.pid`
-restart or +restart
Terminate an already running instance of the milter before starting.
run-group=milter
The process runtime group name to be used when started by root.
run-user=milter
The process runtime user name to be used when started by root.
score-discard=-1
A message with a SIQ score less than or equal to this value will be discarded. The value can be between 0 and 99 inclusive, or -1 to disable. See also score-reject and score-tag options.
score-reject=-1
A message with a SIQ score less than or equal to value will be rejected. The value can be between 0 and 99 inclusive, or -1 to disable. See also score-discard and score-tag options.
score-tag=50
A message with a SIQ score less than or equal to this value will be tagged in the subject line. The value can be between 0 and 99 inclusive, or -1 to disable. See also score-discard and score-reject options.
siq-query=MAIL
Typically the SIQ query is done at the time of the MAIL FROM: command. However, the query can be delayed until the DATA command to allow other filters to be applied. Specify one of MAIL or DATA. Only with siq-query=DATA set, is it possible to B/W list by recipient.
siq-servers=
A semi-colon separated list of SIQ server host[,port] values. These servers will be queried for a score based on the SMTP client IP address and the domain portion of the MAIL FROM: argument. See the SIQ Protocol for details. Only the UDP format is currently supported.
subject-tag=[SPAM]
Subject tag prefix for invalid messages. To disable the subject tag specify: subject-tag=''.
-subject-tag-score
Append the percentage score to the subject tag prefix for spam messages. See also subject-tag.
verbose=info
A comma separated list of how much detail to write to the mail log. Those mark with § have meaning for this milter.
§ all All messages
§ 0 Log nothing.
§ info General info messages. (default)
§ trace Trace progress through the milter.
§ parse Details from parsing addresses or special strings.
§ debug Lots of debug messages.
§ dialog I/O from Communications dialog
  state State transitions of message body scanner.
§ dns Trace & debug of DNS operations
§ cache Cache get/put/gc operations.
§ database Sendmail database lookups.
§ socket-fd Socket open & close calls
§ socket-all All socket operations & I/O
§ libmilter libmilter engine diagnostics
work-dir=/var/tmp
The working directory of the process. Normally serves no purpose unless the kernel option that permits daemon process core dumps is set.

SMTP Responses

This is the list of possible SMTP responses generated by milter-siq.

550 5.7.1 message rejected, SIQ score [0-9]+ too low
Given the returned SIQ server score, the message was rejected. See score-reject.
450 4.7.1 please try again later
The SIQ server suggested to temporarily block the message.
553 5.1.0 imbalanced angle brackets in path
The path given for a MAIL or RCPT command is missing a closing angle bracket
553 5.1.0 address does not conform to RFC 2821 syntax
The address is missing the angle brackets, < and >, as required by the RFC grammar.
553 5.1.0 local-part too long
The stuff before the @ is too long.
553 5.1.[37] invalid local part
The stuff before the @ sign contains unacceptable characters.
553 5.1.0 domain name too long
The stuff after the @ is too long.
553 5.1.7 address incomplete
Expecting a domain.tld after the @ sign and found none.
553 5.1.[37] invalid domain name
The domain after the @ sign contains unacceptable characters.

Installation

  1. Download:

    milter-siq/0.21 md5sum Change Log
    LibSnert md5sum Change Log
    Sendmail 8.13   http://www.sendmail.org/
    Berkeley DB   http://www.sleepycat.com/
  2. If you have never built a milter for Sendmail, then please make sure that you build and install libmilter, which is not built by default when you build Sendmail. Please read the libmilter documentation. Briefly, it should be something like this:

    cd (path to)/sendmail-8.13.7/libmilter
    sh Build -c install
    
  3. The build process for libsnert and milter-siq is pretty straight forward once you have libmilter installed:

    cd (path to)/com/snert/src/lib
    ./configure
    make build
    cd ../milter-siq
    ./configure
    make build
    make install
    

    Both configuration scripts have some options that allow you to override defaults. Those options are listed with:

    ./configure --help
    
  4. An example ${prefix}/share/examples/milter-siq/milter-siq.mc is supplied. This file should be reviewed and the necessary elements inserted into your Sendmail .mc file and sendmail.cf rebuilt. Please note the comments on the general milter flags.

    
    
  5. Once installed and configured, start milter-siq and then restart Sendmail. An example startup script is provided in ${prefix}/share/examples/milter-siq/milter-siq.sh. The default options can be altered by specifying them on the command-line or within a /etc/mail/milter-siq.cf. The milter-siq.cf is parsed first followed by the command-line options.

Notes

  • Currently tested platforms:

    Cobalt Qube 1 with Linux RH 5.1 (mips 2.0.34 kernel); Linux RH 5.1 (Intel x386 2.2.25 kernel); FreeBSD 4.8, 4.9 (Intel x386); OpenBSD 3.6 (Intel x386)
  • The minimum desired file ownership and permissions are as follows for a typical Linux system. For FreeBSD, NetBSD, and OpenBSD the binary and cache locations may differ, but have the same permissions.

    Process user ``milter'' is primary member of group ``milter'' and secondary member of group ``smmsp''. Note that the milter should be started as root, so that it can create a .pid file and .socket file in /var/run; after which it will switch process ownership to milter:milter before starting the accept socket thread.

    /etc/mail/root:smmsp0750 drwxr-x---
    /etc/mail/access.dbroot:smmsp0640 -rw-r-----
    /etc/mail/sendmail.cfroot:smmsp0640 -rw-r-----
    /etc/mail/milter-siq.cfroot:root0644 -rw-r--r--
    /var/run/milter/milter-siq.pidmilter:milter0644 -rw-r--r--
    /var/run/milter/milter-siq.socketmilter:milter0644 srw-r--r--
    /var/db/milter-siqmilter:milter0644 -rw-r--r-- (*BSD)
    /var/cache/milter-siqmilter:milter0644 -rw-r--r-- (linux)
    /usr/local/libexec/milter-siqroot:milter0550 -r-xr-x---
  • I would like to express my thanks to Derek Balling for his support at http://www.milter.org/.

License Agreement 1.4

SNERTSOFT IS WILLING TO LICENSE THE SOFTWARE IDENTIFIED ABOVE TO YOU ONLY UPON THE CONDITION THAT YOU ACCEPT ALL OF THE TERMS CONTAINED IN THIS LICENSE AGREEMENT. PLEASE READ THE AGREEMENT CAREFULLY. BY DOWNLOADING OR INSTALLING THIS SOFTWARE, YOU ACCEPT THE TERMS OF THE AGREEMENT.

  1. Definitions

    1. ``Package'' means the identified above in source and/or binary form, any other machine readable materials provided (including, but not limited to documentation, sample files, data files), any updates or error corrections, and its derivative works.

    2. ``Private Individual'' means an individual using the Package for personal, private, and non-commercial use only.

    3. ``Organisation'' means a legal entity or an individual that does not qualify as a Private Individual defined above.

    4. ``You'' (or ``Your'') means a Private Individual or Organisation exercising rights under, and complying with all of the terms of, this License or a future version of this License issued under Section 5.1. For legal entities, ``You'' includes any entity which controls, is controlled by, or is under common control with You. For purposes of this definition,``control'' means (a) the power, direct or indirect, to cause the direction or management of such entity, whether by contract or otherwise, or (b) ownership of more than fifty percent (50%) of the outstanding shares or beneficial ownership of such entity.

    5. The Package is an original work written by Anthony C. Howe, hereto referred to as the ``Author''.

  2. License To Use

    1. If You are a Private Individual and so benefited from a reduced purchase price, then You may only compile, install, and use this Package, with or without private modifications, exclusively on a single machine You legally own or rent from a third party, provided You retain this notice, the Author's copyright notice, any and all license control methods (see below), and any links within the Package back to the most current online versions of this License and Disclaimer.

    2. Otherwise if You have paid the full purchase price, then You may compile, install, and use this Package, with or without private modifications, exclusively on machines You legally own or rent from a third party, provided You retain this notice, the Author's copyright notice, any and all license control methods (see below), and any links within the Package back to the most current online versions of this License and Disclaimer.

    3. You may copy, share, distribute, modify, and create derivative works from the user manuals and any related documentation solely for Your internal business purposes, such as in-house documentation, training manuals, or reference material.

  3. Restrictions

    1. Redistribution, including but not limited to books, CDROMS, download mirrors, floppy diskettes, hard disks, hardcopy print outs, online archives, solid state disks, streaming tapes, or other current or future forms of storage or communication media of the Package, with or without modifications, including any and all derivative works such as source patches, binaries, binary patches, or similar is expressly forbidden without prior written permission in hardcopy (letter or fax) signed and dated by the Author.

    2. It is expressly forbidden for You to use the Package, in whole or in part, in any other software, except those designated by the Author.

    3. It is expressly forbidden for You to use the Package to develop any software or other technology having the same primary function as the Package, including but not limited to using the Package in any development or test procedure that seeks to develop like software or other technology, or determine if such software or other technology performs in a similar manner as the Package.

    4. You may not sell, rent, lease, or transfer the Package to third parties without prior written permission in hardcopy (letter or fax) signed and dated by the Author.

  4. Termination

    1. This Agreement is effective until terminated. You may terminate this Agreement at any time by destroying all copies of the Package. This Agreement will terminate immediately without notice from the Author if You fail to comply with any provision of this Agreement. Either party may terminate this Agreement immediately should any portion of the Package become, or in either party's opinion be likely to become, the subject of a claim of infringement of any intellectual property right. Upon Termination, You must destroy all copies of the Package.

  5. Versions Of The License

    1. New Versions. The Author may publish revised and/or new versions of the License from time to time. Each version will be given a distinguishing version number.

    2. Effect of New Versions. Once a version of the Package has been published under a particular version of the License, You may always continue to use it under the terms of that License version. You may also choose to use such Package under the terms of any subsequent version of the License published by the Author. No one other than the Author has the right to modify the terms applicable to the Package created under this License.

Disclaimer

THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO WAY SHALL THE AUTHOR OR LICENSEE 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.

License Control

The Package may use one or more license control methods including, but not limited to, license key activation, periodic reporting of Package details and IP address of installation to SnertSoft, remote license verification by SnertSoft, or other future technical means. Any information reported to or gathered by SnertSoft shall remain strictly confidential and the private property of SnertSoft. Under no circumstances will SnertSoft resell or release this information to third parties, unless demanded by court order.

Support

Support is only provided for the Author's original Package. Priority support can be purchased. Free support is limited, based on the Author's availability, though enhancements requests and problem reports are welcome. A community mailing list is available; please refer to SnertSoft web site Support area for details.

Gifts

Gifts from the author's Amazon US or Amazon UK wishlist (search by mail address <achowe at snert dot com>) are welcomed for the continued encouragement, moral support, and ego pumping needed to work in foreign non-english speaking lands.

goals since 17 August 2004