dccifd(8)                   System Manager's Manual                  dccifd(8)


NAME

     dccifd -- Distributed Checksum Clearinghouse Program Interface


SYNOPSIS

     dccifd [-VdbxANQ] [-G on | off | noIP | IPmask/xx] [-h homedir]
            [-p /sock/name | lhost,lport,rhost/bits] [-m map] [-w whiteclnt]
            [-U userdirs] [-t type,[log-thold,]rej-thold] [-g [not-]type]
            [-S header] [-l logdir] [-R rundir] [-T tmpdir]
            [-j maxjobs] [-L ltype,facility.level]


DESCRIPTION

     Dccifd is a daemon built intended to connect spam filters such as SpamAs-
     sasin and mail transfer agents (MTAs) other than sendmail to DCC servers.
     The MTA or filter dccifd which in turn reports related checksums to the
     nearest DCC server.  DCCIFD then adds an X-DCC SMTP header line to the
     message.  The MTA is told to reject the message if it is unsolicited
     bulk.

     Dccifd is similar to the DCC sendmail milter interface, dccm(8) and the
     DCC Procmail interface, dccproc(8).  dccifd is more efficient than
     dccproc but not restricted to use with sendmail.  All three send reports
     of checksums related to mail received by DCC clients and queries about
     the total number of reports of particular checksums.

     MTA programs use a simple ASCII protocol to send a mail message including
     its SMTP envelope to the daemon.  Dccifd responds with an indication of
     whether the message is unsolicited bulk and an optional copy of the mes-
     sage with an X-DCC header added.  The protocol is described below and in
     the include/dccif.h file in the DCC source.  There is a sample C inter-
     face routine in the dcclib/dccif.c file in the DCC source and the
     dcclib.a library generated from the source.  A Perl version of the inter-
     face routine is in dccifd/dccif.pl.  Test or demonstration programs in
     the style of dccproc(8) that use those interface routines are in
     dccifd/dccif-test.

     Since the checksums of messages that are whitelisted locally by the -w
     whiteclnt file are not reported to the DCC server, dccifd knows nothing
     about the total recipient counts for their checksums and so cannot add
     X-DCC header lines to such messages.

     The list of servers that dccifd contacts is in a memory mapped file
     shared by local DCC clients.  The file is maintained with cdcc(8).  Turn
     on the daemon and put its parameters in the dcc_conf.  Start the daemon
     with the start-dccifd script.

   OPTIONS
     The following options are available:

     -V   displays the version of the DCC program interface.

     -d   enables debugging output from the DCC client library.  Additional -d
          options increase the number of messages.  A single -d causes aborted
          SMTP transactions to be logged.

     -b   causes the daemon to not detach itself from the controlling tty and
          put itself into the background.

     -x   causes the daemon to try "extra hard" to contact a DCC server.
          Since it is usually more important to deliver mail than to report
          its checksums, dccifd normally does not delay too long while trying
          to contact a DCC server.  It also will not try again for several
          seconds after a failure.  With -x, it will always try to contact the
          DCC server and it will tell the MTA to answer the DATA command with
          a 4yz temporary failure.

     -A   adds to existing X-DCC headers in the message instead of replacing
          existing headers of the brand of the current server.

     -N   neither adds, deletes, nor replaces existing X-DCC headers in the
          message.  Each message is logged, rejected, and otherwise handled
          the same.

     -Q   only queries the DCC server about the checksums of messages instead
          of reporting and querying.  This is useful when dccifd is used to
          filter mail that has already been reported to a DCC server by
          another DCC client.  This can also be useful when applying a private
          white or black list to mail that has already been reported to a DCC
          server.  No single mail message should be reported to a DCC server
          more than once per recipient, because each report will increase the
          apparent "bulkness" of the message.

     -G on | off | noIP | IPmask/xx
          controls greylisting.  A working greylist server must be named in
          the map file in the DCC home directory.  See dccd(8).

          IPmask/xx and noIP remove part or all of the IP address from the
          greylist triple.  The CIDR block size, xx, must be between 1 and
          128.  96 is added to block sizes smaller than 33 to make them appro-
          priate for the IPv6 addresses used by the DCC.  IPmask/96 differs
          from noIP because the former retains the IPv4 to IPv6 mapping pre-
          fix.

     -W   makes recipient addresses almost white-listed by default to ease
          managing systems where only a minority of users want unsolicited
          bulk mail to be rejected or discarded.  This kludge of a feature is
          useful when addresses should by default not be protected against
          spam with the DCC.  The idea is that the destination addresses of
          participating users are listed with OK2" and non-participants are
          not listed or listed with "OK".

          Messages sent to target addresses that are listed in the -w
          whiteclnt file with "OK" are not reported to the DCC server.

          Messages sent only to target addresses that are not listed are
          delivered.  The DCC server is queried and the X-DCC header is added
          but the message is delivered regardless of target counts and thresh-
          olds.

          Target addresses listed with "OK2" in the whiteclnt file are treated
          neutrally or as if they were not listed and the -W option were not
          specified.  Mail is delivered, rejected, or discarded to addresses
          listed with "OK2" as controlled by target counts, thresholds, and
          whatever the MTA does with an "R" result..

          See also the discussion of -w.

     -h homedir
          overrides the default DCC home directory, which is often /var/dcc.

     -p /sock/name | lhost,lport,rhost/bits
          overrides the default address at which programs contact dccifd.  The
          default is a UNIX domain socket named dccifd in the DCC home direc-
          tory.

          The second form specifies a local host name or IP address, a local
          TCP port number, and the host names or IP addresses of computers
          that can use dccifd.  127.0.0.1 or localhost are common choices for
          lhost.  The special string @ specifies IN_ADDRANY or all local IP
          addresses.  127.0.0.0/8 is a common choice for rhost/bits.

     -m map
          specifies a name or path of the memory mapped parameter file instead
          of the default map in the DCC home directory.  It should be created
          with the cdcc(8) command.

     -w whiteclnt
          specifies an optional file containing SMTP client IP addresses, SMTP
          envelope values, and header values of mail that is not spam, does
          not need a X-DCC header, and whose checksums should not be reported
          to the DCC server.  Local whitelist env_To values are handy for
          white-listing or exempting destination addresses such as Postmaster
          from filtering and for blacklisting or marking addresses that should
          never receive mail.  Mail sent to blacklisted addresses or with
          other blacklisted values such as From or env_From values is reported
          to the DCC server as spam or with target counts of millions.

          If the pathname whiteclnt is not absolute, it is relative to the DCC
          home directory.  The format of the dccifd whiteclnt file is the same
          as the whitelist files used by dbclean(8) and the whiteclnt file
          used by dccproc(8).  See dcc(8) for a description of DCC white and
          blacklists.  Because the contents of the whiteclnt file are used
          frequently, a companion file is automatically created and main-
          tained.  It has the same pathname but with an added suffix of .dccw
          and contains a memory mapped hash table of the main file.

          A local whitelist entry ("OK") or two or more semi-white listings
          ("OK2") for one of the message's checksums prevents all of the mes-
          sage's checksums from being reported to the DCC server and the addi-
          tion of a X-DCC header line by dccifd (except for env_To checksums
          or when -W is used).  A local whitelist entry for a checksum also
          prevents rejecting or discarding the message based on DCC recipient
          counts as specified by -t.  Otherwise, one or more checksums with
          blacklisting entries ("MANY") cause all of the message's checksums
          to be reported to the server with an addressee count of "MANY".

          If the message has a single recipient, an env_To local whiteclnt
          entry of "OK" for the checksum of its recipient address acts like
          any other whiteclnt entry of "OK."  When the SMTP message has more
          than one recipient, the effects can be complicated.  When a message
          has several recipients with some but not all listed in the whiteclnt
          file, dccifd tries comply with the wishes of the users who want fil-
          tering as well as those who don't by silently not delivering the
          message to those who want filtering (i.e. are not white-listed) and
          delivering the message to don't want filtering.

          Consider the -W option for implicitly or by default white-listing
          env_to values.

     -U userdirs
          enables private whitelists and log files.  Each target of a message
          can have a directory of log files named userdirs/addr/log where addr
          is the local user or mailbox name computed by the MTA.  The name of
          each user's log directory must be log.  If it is not absolute,
          userdirs is relative to the DCC home directory.  The sub-directory
          prefixes for -l logdir are not honored.  The directory containing
          the log files must be named log and it must be writable by the
          dccifd process.  Each log directory must exist or logging for the
          corresponding is silently disabled.  The files created in the log
          directory are owned by the UID of the dccifd process, but they have
          group and other read and write permissions copied from the corre-
          sponding log directory.  To ensure the privacy of mail, it may be
          good to make the directories readable only by owner and group, and
          to use a cron script that changes the owner of each file to match
          the grandparent addr directory.

          There can also be a whitelist named userdirs/addr/whiteclnt for each
          address addr. The name of the file must be whiteclnt.  Any checksum
          that is not white- or blacklisted by an individual addressee's
          whitelist is checked in the -w -whiteclnt list.  A missing per-
          address whiteclnt file is the same as an empty file.  Relative paths
          for whitelists included in per-address files are resolved in the DCC
          home directory.  The whiteclnt files and the addr directories con-
          taining them must be writable by the dccifd process.

     -t type,[log-thold,]rej-thold
          sets logging and "spam" thresholds for checksum type.  The checksum
          types are IP, env_From, From, Message-ID, Received, Body, Fuz1, and
          Fuz2.  The string ALL sets thresholds for all types, but is unlikely
          to be useful except for setting logging thresholds.  The string CMN
          specifies the commonly used checksums Body, Fuz1, and Fuz2.
          Rej-thold and log-thold must be numbers, the string NEVER, or the
          string MANY indicating millions of targets.  Counts from the DCC
          server as large as the threshold for any single type are taken as
          sufficient evidence that the message should be logged or rejected.

          Log-thold is the threshold at which messages are logged.  It can be
          handy to log messages at a lower threshold to find solicited bulk
          mail sources such as mailing lists.  If no logging threshold is set,
          only rejected mail and messages with complicated combinations of
          white and blacklisting are logged.  Messages that reach at least one
          of their rejection thresholds are logged regardless of logging
          thresholds.

          Rej-thold is the threshold at which messages are considered "bulk,"
          and so should be rejected or discard if not white-listed.

          The checksums of locally white-listed messages are not checked with
          the DCC server and so only the number of targets of the current
          instance of a white-listed message are compared against the thresh-
          olds.

          The default is -t ALL,NEVER, so that nothing is discarded or logged.
          A common choice is -t CMN,25,50 to reject or discard mail with com-
          mon bodies except as overridden by the whitelist of the DCC server
          and local -o, -s, -g, and -w.

     -g [not-]type
          indicates that white-listed, OK or OK2, counts from the DCC server
          for a type of checksum are to be believed.  They should be ignored
          if prefixed with not-.  Type is one of the same set of strings as
          for -t.  Only IP, env_From, and From are likely choices.  By default
          all three are honored, and hence the need for not-.

     -S hdr
          adds to the list of substitute or locally chosen headers that are
          checked with the -w whiteclnt file and sent to the DCC server.  The
          checksum of the last header of type hdr found in the message is
          checked.  Hdr can be HELO to specify the SMTP envelope HELO value.
          Hdr can also be mail_host to specify the host name from the
          Mail_from value in the SMTP envelope.  As many as 6 different sub-
          stitute headers can be specified, but only the checksum of the first
          of the 6 will be sent to the DCC server.

     -l logdir
          specifies a directory in which files containing copies of messages
          processed by dccifd are kept.  All messages logged are copied to the
          -l logdir directory.  They can also be copied to per-user directo-
          ries specified with -U.  Information about other recipients of a
          message is deleted from the per-user copies.

          If logdir starts with D?, log files are put into subdirectories of
          the form logdir/JJJ where JJJ is the current julian day.  H?logdir
          puts logs files into subdirectories of the form logdir/JJJ/HH where
          HH is the current hour.  M?logdir puts log files into subdirectories
          of the form logdir/JJJ/HH/MM where MM is the current minute.  See
          the FILES section below concerning the contents of the files.

          The directory is relative to the DCC home directory if it is not
          absolute

     -R rundir
          specifies the "run" directory where the UNIX domain socket and file
          containing the daemon's process ID are stored.  The default value is
          often /var/run/dcc.

     -T tmpdir
          changes the default directory for temporary files from the default.
          The default is the directory specified with -l or the system default
          if there -l is not used.  The system default is often /tmp.

     -j maxjobs
          limits the number of simultaneous requests that will be processed.
          The default value is the maximum number that seems to be possible
          given the number of open files, select() bit masks, and so forth
          that are available.

     -L ltype,facility.level
          specifies how messages should be logged.  Ltype must be error or
          info to indicate which of the two types of messages are being con-
          trolled.  Level must be a syslog(3) level among EMERG, ALERT, CRIT,
          ERR, WARNING, NOTICE, INFO, and DEBUG.  Facility must be among AUTH,
          AUTHPRIV, CRON, DAEMON, FTP, KERN, LPR, MAIL, NEWS, USER, UUCP, and
          LOCAL0 through LOCAL7.  The default is equivalent to

                -L info,MAIL.NOTICE -L error,MAIL.ERR

   Protocol
     Dccifd uses a simple ASCII protocol to receive mail messages to be
     checked and to return results.  For each message, the MTA must open a
     connection to the interface daemon, send options, envelope recipients,
     and the message, receive the results, and close the connection.

     Each of the following lines are sent in order to the daemon.  Each ends
     with a newline ('\n') character.
       options     zero or more blank-separated strings among:
                     spam       if the message is known to be spam
                     body       if all of the headers with added X-DCC if
                                header line and body should be returned
                     header     the X-DCC header should be returned
                     query      to ask the DCC server about the message with-
                                out reporting it as if dccifd were running
                                with -Q.
                     no-reject  to prevent the overall, one character line 'R'
                                result.  This can be useful when using dccifd
                                only for greylisting.
       client      IP address of the SMTP client in a "dotted" or "coloned"
                   ASCII string and reverse-DNS host name.  If the host name
                   is present, it must follow a carriage return character
                   ('\r') after the IP address.  The client IP address must be
                   present and non-null if the host name is present If the
                   client IP address is absent, then the IP address and host
                   name are taken from the first Received header if it has the
                   standard "name (name [IP address])..." format.
       HELO        SMTP HELO value or nothing, followed by a newline charac-
                   ter.
       sender      or SMTP Mail From command value
       recipients  or SMTP Rcpt To values followed by the the corresponding
                   local user names, one pair to a line.  Each optional local
                   user name is separated from the corresponding recipient
                   address by a carriage return ('\r').  A local user name can
                   be null if it is not known.  Recipients that lack local
                   user names will lack per-user log files and will not invoke
                   a per-user white-list.

     The last recipient-user name pair is followed by an empty line and the
     headers and body of the message.  The end of the body of the mail message
     is signaled by the MTA half-closing the connection.  See shutdown(2).

     Dccifd responds with three things.  First is a one character line of the
     overall result advising the MTA to
       A    accept the message for all recipients and answer the SMTP DATA
            command with a 2yz result.
       G    answer with a 4yz result to embargo the message for greylisting.
       R    reject the message and answer the DATA command with a 5yz result.
       S    accept the message for some recipients and so answer the DATA com-
            mand with a 2yz result.
       T    temporary failure by the DCC system and so answer with a 4yz
            result.

     Second is a line of 'A', 'G', and 'R' characters indicating that the mes-
     sage should be accepted and delivered or discarded for each corresponding
     recipient.  Limitations in the SMTP protocol allows only a single result
     for the DATA command for all recipients that were not rejected before
     body of the message was offered with the DATA command.  To accept the
     message for some recipients and reject it for others, the MTA must tell
     the SMTP client it is accepting the message for all recipients and then
     discard it for those that would reject it.

     Finally, if the body or header strings are in the first line of options
     sent by the MTA to the daemon, then the X-DCC header line or the entire
     body with the X-DCC header line follows.


FILES

     /var/dcc    is the DCC home directory in which other files are found.
     libexec/start-dccifd
                 is a script often used to the daemon.
     dcc/dcc_conf
                 contains parameters used by the scripts to start DCC daemons
                 and cron jobs.
     logdir      is an optional directory specified with -l and containing
                 marked mail.  Each file in the directory contains one mes-
                 sage, at least one of whose checksums reached its -t thresh-
                 olds or that is interesting for some other reason.  Each file
                 starts with lines containing the date when the message was
                 received, the IP address of the SMTP client, and SMTP enve-
                 lope values.  Those lines are followed by the body of the
                 SMTP message including its header as it was received.  Only
                 approximately the first 32 KBytes of the body are recorded.
                 The checksums for the message follow the body.  They are fol-
                 lowed by lines indicate that one of the checksums is white-
                 or blacklisted by the -w whiteclnt file.  Each file ends with
                 the X-DCC header line added to the message and the disposi-
                 tion of the message.
     map         is the memory mapped file of information concerning DCC
                 servers in the DCC home directory.
     whiteclnt   contains the client whitelist in the format described in
                 dcc(8).
     whiteclnt.dccw
                 is a memory mapped hash table of the whiteclnt file.
     dccifd.pid  in the -R rundir directory contains daemon's process ID.


SEE ALSO

     cdcc(8), dbclean(8), dcc(8), dccd(8), dblist(8), dccm(8), dccproc(8),
     dccsight(8),


HISTORY

     Implementation of dccifd was started at Rhyolite Software in 2002.  This
     describes version 1.2.39.


BUGS

     dccifd uses -t where dccproc(8) uses -c.

     Systems without setrlimit(2) and getrlimit(2) can have problems with the
     default limit on the number of simultaneous jobs, the value of -j.  Every
     job requires four open files.  These problems are usually seen with
     errors messages that say something like
           dccifd[24448]: DCC: accept() returned invalid socket
     A fix is to use a smaller value for -j or to allow dccifd to open more
     files.

FreeBSD 4.9                     March 27, 2004                     FreeBSD 4.9

Man(1) output converted with man2html modified for the DCC $Date 2001/04/29 03:22:18 $