NAME
    ispMailGate - a general purpose filtering MDA for sendmail

WARNING! WARNING! WARNING!
    This is an alpha release! What you are using now is tested by using a
    comparatively small test suite in our local environment. You are perhaps
    planning to include this software in a production environment. We don't
    discourage to do so, but we strongly advise you to be extremely careful.
    In particular, start by filtering only mails for a very small number of
    email adresses, perhaps your own and something similar. That is, be
    extremely cautios when modifying your sendmail configuration.

    See INSTALLATION and SENDMAIL CONFIGURATION below for a detailed
    description of your sendmail setup.

SYNOPSIS
    For running standalone:

        ispMailGateD -f <sender> <recipient1> [... <recipientN>]

    For running as a daemon:

        ispMailGateD -s [-d] [-t <tmpdir>] [-a <facility>] [-p <pidfile>]
            [-u <unixsock>]

DESCRIPTION
    IspMailGate is a general purpose email filtering system. The program
    gets included into a sendmail configuration as a delivery agent (MDA)
    and the usual sendmail rules can be applied for deciding which emails to
    feed into ispMailGate. The true filters are implemented as modules, so
    its easy to extend the possibilities of ispMailGate. Current modules
    offer automatic compression and decompression, encryption, decryption
    and certification with PGP or virus scanning.

    The program can run in a usual standalone mode, but that's not
    recommended, except for debugging and similar tasks. The recommended
    mode will be running the program as a server, completely independent
    from sendmail. A small C program (called a wrapper) will instead be
    configured as sendmails MDA. This wrapper connects to the server via a
    well known Unix socket (by default /var/run/ispmailgate.sock), passes
    its command line arguments and standard input to the server and
    disconnects. Obviously this second solution has much better performance
    as you load the Perl interpreter only once.

  Command Line Interface

    The following options affect ispMailGate's behaviour:

    --facility=<fac>
        Advices the ispMailGate to use syslog facility <fac>. By default
        syslog entries are written as facility daemon.

    --debug
        The program runs in debugging mode, logging information into the
        syslog. Perhaps more information than you like ... :-)

    --from=<sender>
        Sets a mails sender.

    --server
        Tells the program not to run in standalone mode and instead detach
        from the shell to enter server mode. This mode is currently not
        usable, as the wrapper is not yet available.

    --tmp-dir=<dir>
        Sets the programs directory for temporary files to <dir>. When
        unpacking a complex and big multipart mail, the ispMailGate may need
        surprisingly much space. By default /var/spool/ispmailgate is used.

    --unix-sock=<sock>
        Tells the server to listen on file <sock> for unix socket
        connections. By default the server uses /var/run/ispmailgate.sock.

INSTALLATION
  Requirements

    To start with the requirements: You need

    1.) A running sendmail (recommended: 8.9.3 or later); if you don't have
    sendmail or an older version, you find the current release at

        ftp://ftp.sendmail.org/pub/sendmail

    2.) A late version of Perl (5.005 or later); if you don't have Perl, get
    it from any CPAN mirror, for example

        ftp://ftp.funet.fi/pub/languages/perl/CPAN/src/5.0

    3.) The MIME-tools module (version 4.116 or later), its prerequired
    modules (MailTools, MIME-Base64 and IO-Stringy) and the IO::Tee module
    (version 0.61 or later). All these modules are available from any CPAN
    mirror, for example

        ftp://ftp.funet.fi/pub/languages/perl/CPAN/modules/Mail
        ftp://ftp.funet.fi/pub/languages/perl/CPAN/modules/MIME
        ftp://ftp.funet.fi/pub/languages/perl/CPAN/modules/IO

    Installing a Perl module is quite easy, btw. Either you use the
    automatic CPAN interface (requires an Internet connection or something
    similar) by executing

        perl -MCPAN -e shell

    or you fetch the modules with FTP, extract the tar.gz files, go into the
    distribution directory (for example MIME-tools-4.116) and do a

        perl Makefile.PL
        make
        make test
        make install

    You'll like it! :-)

  System preparation

    Although ispMailGate is usually started as root, because certain
    initialization settings need root permissions, it must not continue
    running as root. Instead it impersonates itself to the same UID and GID
    that sendmail uses for delivering mails. In what follows, I assume UID
    *daemon* and GID <mail>, as used on a Red Hat Linux box.

    IspMailGate needs its own directory for creating temporary files.
    Usually this could be `/var/spool/ispmailgate' or something similar.
    Make sure that the daemon user from above, (but noone else) has access
    to this directory:

        mkdir /var/spool/ispmailgate
        chown daemon /var/spool/ispmailgate
        chgrp mail /var/spool/ispmailgate
        chmod 700 /var/spool/ispmailgate

  Program installation

    The program is installable like any other Perl module. Indeed, you can
    even use the automatic CPAN installation. If you are not used to CPAN
    installation or cannot use the CPAN shell, you need to perform a manual
    installation: First, fetch the archive from any CPAN mirror, for example

        ftp://ftp.funet.fi/pub/languages/perl/CPAN/authors/id/JWIED

    and extract the archive with

        gzip -cd Mail-IspMailGate-<version>.tar.gz | tar xf -

    After that, do a

        cd Mail-IspMailGate-<version>

    and do a

        perl Makefile.PL
        make
        make test           # You need to be root here!
        make install        # You need to be root here!

    While running "perl Makefile.PL", you'll be prompted a lot of questions.
    In general you can answer them by simply hitting return, the defaults
    should be fine. The questions are explained in the section CONFIGURATION
    FILE below, because your answers are used for creating this config file.
    the section on "CONFIGURATION FILE".

    If "make test" reports any errors, let me know.

SENDMAIL CONFIGURATION
    To understand the required sendmail configuration, let's first take a
    look at the following diagram:

            +----------------+
            | Incoming       |
            | mail for       |
            | joe@ispsoft.de |
            +----------------+

                |
                | Port 25
                | (SMTP)
                |

            +----------------------+        +---------------------+
            |                      |        |                     |
            |  Sendmail, with      |        |  IspMailGate        |
            |  IspMailGate support |  ----> |  receives and       |
            |  integrated          |        |  processes the mail |
            |                      |        |                     |
            +----------------------+        +---------------------+

               V                                    |
                                                    |
            +---------------------------+           | Port 26
            | mailertable:              |           |
            | ispsoft.de => ispmailgate |           |
            +---------------------------+           |

                                          +-----------------------+
            +-------------------------+   |                       |
            | Other mailertable:      |   |  Second sendmail,     |
            | ispsoft.de => mailhost  | < |  without IspMailGate, |
            +-------------------------+   |  other mailertable    |
                                          |                       |
                                          +-----------------------+

    The idea is that we have two sendmail instances: The first one is
    accepting mails from the outside world (it could well be smapd or
    another SMTP wrapper).

    Mails accepted by the first instance will optionally be piped into
    IspMailGate, depending on your mailertable or whatever method you choose
    for selecting a delivery agent.

    As soon as IspMailGate has processed your mails, they cannot be
    delivered to the same sendmail: Sendmail would detect the same
    recipients as before, and feed the mail back into IspMailGate. The
    immediate result would be an endless loop.

    Instead we configure another instance of sendmail, running for example
    on port 26, which accepts mails by IspMailGate. This second sendmail
    will typically be protected to the outside world, for example by using a
    packet filter.

    Of course it is possible to replace the second sendmail with a mail
    server running on another machine. However, I discourage you to do so,
    because IspMailGate has no integrated spooling system: If the foreign
    host would be down, you mail would be lost forever! However, you can
    easily configure the second sendmail for delivery to the same host, this
    time using a safe spooling system.

  Details

    Before reading on, you should have some basic knowledge on sendmail
    configuration. In particular you should be used to work with

    sendmail.mc
        the m4 macro file that is used to create sendmail.cf (If you had the
        impression that hacking sendmail.cf is the method of choice for
        configuring sendmail, your knowledge of sendmail is a little bit too
        basic :-)

    mailertable
        the file that is used for selecting delivery agents, based on a
        domain name

    sendmail.cw
        the file that is used for selecting "local" domains.

    All these files are described in the file cf/README from the sendmail
    distribution. The same file is available online as sendmail
    documentation on http://www.sendmail.org. I strongly encourage you to
    read about it.

    In what follows I assume that we have two hosts: *gate.ispsoft.de* is a
    firewall running IspMailGate and two instances of sendmail.
    *mail.ispsoft.de* is the real mail server. Mail for the domain
    *ispsoft.de* shall be checked by IspMailGate, passed to the second
    instance of sendmail and finally delivered to the real mail server.

    Furthermore I assume that the cf files from the sendmail distribution
    are in /usr/lib/sendmail-cf. This is the case on a Red Hat Linux box, if
    you have installed the RPM package *sendmail-cf*. It may be
    /usr/share/sendmail with SuSE Linux or anything else on another system.

    First of all we copy the file examples/ispmailgate.m4 from the
    IspMailGate distribution to /usr/lib/sendmail-cf/mailer. Then we create
    the following files:

    /etc/mail/sendmail.mc
          divert(-1)
          include(`/usr/lib/sendmail-cf/m4/cf.m4')
          define(`confCW_FILE', `/etc/mail/sendmail.cw')
          define(`ALIAS_FILE', `/etc/mail/aliases')
          define(`QUEUE_DIR', `/var/spool/mqueue')
          OSTYPE(`linux')
          FEATURE(use_cw_file)
          FEATURE(mailertable, `hash -o /etc/mail/mailertable')
          FEATURE(virtusertable, `hash -o /etc/mail/virtusertable')
          FEATURE(access_db)
          MAILER(local)
          MAILER(smtp)
          MAILER(ispmailgate)

    /etc/mail2/sendmail.mc
          divert(-1)
          include(`/usr/lib/sendmail-cf/m4/cf.m4')
          define(`confCW_FILE', `/etc/mail/sendmail.cw')
          define(`ALIAS_FILE', `/etc/mail/aliases')
          define(`QUEUE_DIR', `/var/spool/mqueue2')
          define(`confDAEMON_OPTIONS', `port=26')
          OSTYPE(`linux')
          FEATURE(use_cw_file)
          FEATURE(mailertable, `hash -o /etc/mail2/mailertable')
          FEATURE(virtusertable, `hash -o /etc/mail/virtusertable')
          FEATURE(access_db)
          MAILER(local)
          MAILER(smtp)

        You see, this is almost the same file, with three exceptions:

    1.)     The first sendmail is running on the default port 25, because it has
            no special port settings. The second sendmail is running on port
            26.

    2.)     The first sendmail is using /etc/mail/mailertable, the second has
            /etc/mail2/mailertable.

    3.)     The second sendmail doesn't have a mailer ispmailgate.

    4.)     The first sendmail is using another spool directory,
            /var/spool/mqueue2. (I am not sure, whether this is required,
            however it doesn't harm, so let's be on the safe side.)

    /etc/mail/mailertable
          ispsoft.de    ispmailgate:ispsoft.de

    /etc/mail2/mailertable
          ispsoft.de    ispmailgate:mail.ispsoft.de

        You see, the only difference between these two instances of
        mailertable is that the domain *ispsoft.de* is treated different.

    Finally we have to execute some commands to get this configuration
    running:

            mkdir /var/spool/mqueue2
            # The following should match the settings of
            # /var/spool/mqueue exactly.
            chown root /var/spool/mqueue2
            chgrp root /var/spool/mqueue2
            chmod 755 /var/spool/mqueue

            cd /etc/mail
            m4 sendmail.mc >sendmail.cf
            makemap hash mailertable <mailertable
            cd /etc/mail2
            m4 sendmail.mc >sendmail.cf
            makemap hash mailertable <mailertable

    The above is fine for Linux. On other operating systems you might need
    to use GNU m4 rather than the builtin m4 and replace the map type *hash*
    with *dbm*. In particular this applies to Solaris.

    Finally, kill any running sendmail and start the new versions with

            chmod 755 /etc/mail /etc/mail2
            chmod 644 /etc/mail/sendmail.cf /etc/mail2/sendmail.cf
            /usr/sbin/sendmail -C /etc/mail/sendmail.cf -bd -q1h
            /usr/sbin/sendmail -C /etc/mail2/sendmail.cf -bd -q1h

    (The chmod commands because sendmail is *really* picky about group
    writable files and directories.)

CONFIGURATION FILE
    The program depends on a local configuration file, read as the
    Mail::IspMailGate::Config module. In other words, this configuration
    file is pure Perl code defining certain variables under the name space
    Mail::IspMailGate::Config. The module is read from the file
    /usr/lib/perl5/site_perl/5.005/Mail/IspMailGate/Config.pm.

    The following variables are meaningful to the program:

    VERSION
        The programs version; do not modify without a good reason.

    tmp_dir
        Set's the default directory for creating temporary files, currently
        /var/spool/ispmailgate. You can modify this with the `--tmpdir'
        directive, see above.

    unix_sock
        The unix socket that the client connects to, currently
        /var/run/ispmailgate.sock. You can use the `--unixsock' argument for
        overwriting the default.

    pid_file
        The PID file where a running server stores its PID, currently
        /var/run/ispmailgate.pid. You can use the `--pidfile' argument for
        overwriting the default.

    mail_user
    mail_group
        IspMailGate is running as this user and group, by default daemon and
        mail.

    mail_host
        The host to use for passing mails after processing them by the mail
        filter. By default 'localhost' is used, in other words, the mails
        are immediately passed back to sendmail.

        To omit a possible loop problem, sendmail must be ready for handling
        email addresses like user@domain.ispmailgate. For such addresses it
        must rip off the .ispmailgate and guarantee not to feed the mails
        back into ispMailGate. See the section on "SENDMAIL CONFIGURATION"
        below.

    recipients
        An array ref with list of possible recipients/senders and filter
        lists that describe how to handle mails being sent from the senders
        to the recipients.

        Each element of the list is a hash ref with the following elements:

    recipient
            A regular expression (Perl regular expression, that is) for
            matching the recipient address. An empty string matches any
            recipient.

    sender  A regular expression (Perl regular expression, again) for matching
            the sender address. An empty string matches any sender.

    filters An array ref to a list of filters. A mail will be fed into that list
            (from the left to the right) and the final result will be
            returned to sendmail. See the Mail::IspMailGate::Filter(3)
            manpage for a description of creating filters.

        The recipient list will be read top to bottom, the first match
        decides which rule to choose. See the example configuration below
        for some example rules.

    default_filter
        If no element of the recipients list matches an emails senders and
        recipients, the filters from this variable will be choosen. By
        default it contains a dummy filter:

          $cfg->{'default_filter'} = ['Mail::IspMailGate::Filter::Dummy'];

    packer
        This variable belongs to the Packer module. See the
        Mail::IspMailGate::Packer(3) manpage for details.

    virscan
        These belong to the VirScan module. See the
        Mail::IspMailGate::VirScan(3) manpage for details.

    pgp This variable belong to the PGP module. See the
        Mail::IspMailGate::PGP(3) manpage for details.

  Example Configuration

    It might help to look at a commented example of the configuration file:

        package Mail::IspMailGate::Config;

        $Mail::IspMailGate::Config::config = bless( {
        # Config file version
          'VERSION' => '1.100',
        # Path of external virus scanner or empty
          'antivir_path' => '/usr/bin/antivir',
        # List of filters to use by default
          'default_filter' => [
            'Mail::IspMailGate::Filter::Dummy'
          ],
        # Facility to use for syslog
          'facility' => 'mail',
        # Path of the gzip binary (for extracting .gz files) or empty
          'gzip_path' => '/usr/bin/gzip',
        # Path of the LhA binary (for extracting .lha files) or empty
          'lha_path' => '',
        # GID under which sendmail is executing external binaries
          'mail_group' => 'mail',
        # Mail host (with optional :port) to use for final delivery
          'mail_host' => 'localhost:26',
        # UID under which sendmail is executing external binaries
          'mail_user' => 'daemon',
        # Configuration of the packer
          'packer' => {
            'gzip' => {
              'neg' => '$gzip_path -cd',
              'pos' => '$gzip_path -c'
            }
          },
        # PID file to use for the server
          'pid_file' => '/var/run/ispmailgate.pid',
        # E-Mail address of the administrator
          'postmaster' => '[A',
        # List of senders/recipients and associated filters
          'recipients' => [
            {
              'filters' => [
                'Mail::IspMailGate::Filter::VirScan'
              ],
              'recipient' => '[@\\.]ispsoft.de$'
            }
          ],
        # Path of the tar binary (for extracting .tar files) or empty
          'tar_path' => '/usr/bin/gtar',
        # Directory to use for temporary files
          'tmp_dir' => '/var/spool/ispmailgate',
        # Path of the unarj binary (for extracting .arj files) or empty
          'unarj_path' => '',
        # Path of the Unix socket to connect to a server
          'unix_sock' => '/var/run/ispmailgate.sock',
        # Domain to assume for email adresses without @domain
          'unqualified_domain' => 'ispsoft.de',
        # Path of the unzip binary (for extracting .zip files) or empty
          'unzip_path' => '/usr/bin/unzip',
        # Configuration of the virus scanner
          'virscan' => {
            'scanner' => '$antivir_path -rs -nolnk -noboot $ipaths',
            'deflater' => [
              {
                'cmd' => '$gzip_path -cd $ipath | $tar_path -xf -C $odir',
                'pattern' => '\\.(?:tgz|tar\\.gz|tar\\.[zZ])$'
              },
              {
                'cmd' => '$gzip_path -cd $ipath >$opath',
                'pattern' => '\\.(?:gz|[zZ])$'
              },
              {
                'cmd' => '$gzip_path -cd $ipath >$opath',
                'pattern' => '\\.tar$'
              },
              {
                'cmd' => '$unzip_path $ifile -d $odir',
                'pattern' => '\\.zip$'
              },
              {
                'cmd' => '$gzip_path -cd $ipath | $tar_path -xf -C $odir',
                'pattern' => '\\.(?:tgz|tar\\.gz|tar\\.[zZ])$'
              },
              {
                'cmd' => '$gzip_path -cd $ipath >$opath',
                'pattern' => '\\.(?:gz|[zZ])$'
              },
              {
                'cmd' => '$gzip_path -cd $ipath >$opath',
                'pattern' => '\\.tar$'
              },
              {
                'cmd' => '$unzip_path $ifile -d $odir',
                'pattern' => '\\.zip$'
              },
              {
                'cmd' => '$gzip_path -cd $ipath | $tar_path -xf -C $odir',
                'pattern' => '\\.(?:tgz|tar\\.gz|tar\\.[zZ])$'
              },
              {
                'cmd' => '$gzip_path -cd $ipath >$opath',
                'pattern' => '\\.(?:gz|[zZ])$'
              },
              {
                'cmd' => '$gzip_path -cd $ipath >$opath',
                'pattern' => '\\.tar$'
              },
              {
                'cmd' => '$unzip_path $ifile -d $odir',
                'pattern' => '\\.zip$'
              }
            ]
          },
        }, 'Mail::IspMailGate::Install' );

AUTHORS AND COPYRIGHT
    This module is

        Copyright (C) 1998         Amar Subramanian
                                   Grundstr. 32
                                   72810 Gomaringen
                                   Germany

                                   Email: amar@neckar-alb.de
                                   Phone: +49 7072 920696

                           and     Jochen Wiedmann
                                   Am Eisteich 9
                                   72555 Metzingen
                                   Germany

                                   Email: joe@ispsoft.de
                                   Phone: +49 7123 14887

        All Rights Reserved.

    You may distribute under the terms of either the GNU General Public
    License or the Artistic License, as specified in the Perl README file.

SEE ALSO
    the Mail::IspMailGate::Filter(3) manpage, the
    Mail::IspMailGate::Packer(3) manpage, the Mail::IspMailGate::VirScan(3)
    manpage, the Mail::IspMailGate::PGP(3) manpage and the MIME::Entity(3)
    manpage

