dccifd(8)             Distributed Checksum Clearinghouse             dccifd(8)


NAME

     dccifd -- Distributed Checksum Clearinghouse Interface Daemon


SYNOPSIS

     dccifd [-VdbxANPQ] [-G on | off | noIP | IPmask/xx] [-h homedir]
            [-I user] [-p /sock | lhost,lport,rhost] [-o /sock | host,port]
            [-D local-domain] [-m map] [-w whiteclnt] [-U userdirs]
            [-a IGNORE | REJECT | DISCARD] [-t type,[log-thold,]rej-thold]
            [-g [not-]type] [-S header] [-l logdir] [-R rundir]
            [-r rejection-msg] [-T tmpdir] [-j maxjobs]
            [-B dnsbl-option] [-L ltype,facility.level]


DESCRIPTION

     dccifd is a daemon intended to connect spam filters such as SpamAssasin
     and mail transfer agents (MTAs) other than sendmail to DCC servers.  The
     MTA or filter dccifd which in turn reports related checksums to the near-
     est DCC server and 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(8) but not restricted to use with sendmail like dccm(8).  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 a subset of SMTP 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 message with an X-DCC header added.  The ASCII protocol is
     described below and in the include/dccif.h file in the DCC source.  There
     is a sample C interface routine in the dcclib/dccif.c file in the DCC
     source and the dcclib.a library generated from the source.  A Perl ver-
     sion of the interface routine is in dccifd/dccif.pl.  Test or demonstra-
     tion programs in the style of dccproc(8) that use those interface rou-
     tines are in /var/dcc/build/dcc/dccifd/dccif-test.

     A subset of ESMTP can be used instead of the ASCII protocol to connect
     dccifd to postfix as a "Before-Queue Content Filter."  See the -o flag.

     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.

     Enable the daemon and put its parameters in the /var/dcc/dcc_conf file
     and start the daemon with the /var/dcc/libexec/rcDCC or
     /var/dcc/libexec/start-dccifd scripts.

     The list of servers that dccifd contacts is in the memory mapped file
     /var/dcc/map shared by local DCC clients.  The file is  maintained with
     cdcc(8).

   OPTIONS
     The following options are available:

     -V   displays the version of dccifd.  Two or more -V options show the
          options with which it was built.

     -d   enables debugging output from the DCC client software.  Additional
          -d options increase the number of messages.  A single -d logs
          aborted SMTP transactions including those from some "dictionary
          attacks."

     -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 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 mail message is logged, rejected, and otherwise han-
          dled the same.

     -P   The SpamAsassin DCC.pm plugin should watch for "bulk" in X-DCC SMTP
          header fields, but historically has looked for counts of "many".
          However, there are situations when dccifd knows that a mail message
          is extremely bulky and probably spam.  For example, mail from a
          sender that is blacklisted in whiteclnt gets an X-DCC header that
          includes bulk.  To acommodate that bug in SpamAssassin, by default
          whenever dccifd generates an X-DCC header containing "bulk", it also
          forces the Body count to "many".  -P turns off that kludge and the
          Body contains the count from the DCC server.

     -Q   only queries the DCC server about the checksums of messages instead
          of reporting.  This is useful when dccifd is used to filter mail
          that has already been reported to a DCC server by another DCC
          client.  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.

          It is better to use MXDCC lines in the global /var/dcc/whiteclnt
          file for your MX mail servers that use DCC than to use -Q with
          dccifd.

          Do not use -Q except on mail that you know has been reported to a
          DCC server.  DCC depends on reports of all except known private mail
          and works only because almost no DCC installations use -Q.

     -G on | off | noIP | IPmask/xx
          controls greylisting.  At least one working greylist server must be
          listed in the /var/dcc/map file.  If more than one is named, they
          must "flood" or change checksums and they must use the same -G
          parameters.  See dccd(8).  Usually all dccm or dccifd DCC client
          processes use the same -G parameters.

          IPmask/xx and noIP remove part or all of the IP address from the
          greylist triple.

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

     -I user
          specifies the UID and GID of the process.

     -p /sock/name | lhost,lport,rhost
          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 name or IP addresses of computers that
          can use dccifd.  127.0.0.1 is a common choices for lhost.  The
          string * for lhost specifies IN_ADDRANY or all local IP addresses.
          127.0.0.1 is a common choice for rhost, but it can be a
          xxx.xxx.xxx.xxx/mm CIDR block or a xxx.xxx.xxx.xxx-yyy.yyy.yyy.yyy
          range of IPv4 or IPv6 addresses.

     -o /sock | host,port
          enables SMTP proxy mode instead of the ASCII protocol and specifies
          the output connection when dccifd acts as an SMTP proxy.  It is the
          address of the SMTP server for which dccifd acts as SMTP client.
          When /sock is /dev/null, dccifd acts as if there were downstream
          SMTP server that always answers "250 ok".  The string @ specifies
          the same IP address as the incoming TCP connection.

          The input to dccifd in SMTP proxy mode is specified with -p.  For
          example, -p 127.0.0.1,10025,127.0.0.1/32 -o 127.0.0.1,10026 could be
          used to connect dccifd with Postfix as described in the documenta-
          tion in version 2.2.1 Postfix documentation.

          See below concerning the subset of ESMTP used in this mode.

     -m map
          specifies a name or path of the memory mapped parameter file instead
          of the default /var/dcc/map.  It should be created with the cdcc(8)
          command.

     -w whiteclnt
          specifies an optional file containing filtering parameters as well
          as SMTP client IP addresses, SMTP envelope values, and header values
          of mail that is spam or is not spam and does not need a X-DCC
          header, and whose checksums should not be reported to the DCC
          server.

          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
          /var/dcc/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 whitelist entry ("OK") or two or more semi-whitelistings ("OK2")
          for one of the message's checksums prevents all of the message's
          checksums from being reported to the DCC server and the addition of
          a X-DCC header line by dccifd.  A whitelist entry for a checksum
          also prevents rejecting or discarding the message based on DCC
          recipient counts as specified by -a and -t.  Otherwise, one or more
          checksums with blacklisting entries ("MANY") cause all of the mes-
          sage's checksums to be reported to the server with an addressee
          count of "MANY".

          If the message has a single recipient, an env_To 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 sev-
          eral recipients with some but not all listed in the whiteclnt file,
          dccifd tries comply with the wishes of the users who want filtering
          as well as those who don't by silently not delivering the message to
          those who want filtering (i.e. are not whitelisted) and delivering
          the message to users who don't want filtering.

     -U userdirs
          enables per-user whiteclnt files and log directories.  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 com-
          puted 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 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 permis-
          sions copied from the corresponding 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 per-user whitelist file named
          userdirs/addr/whiteclnt for each addressee addr. Any checksum that
          is not white- or blacklisted by an individual addressee's per-user
          whiteclnt file  is checked in the main /var/dcc/whiteclnt file.  A
          missing per-addressee whiteclnt file is the same as an empty file.
          Relative paths for files included in per-addressee files are
          resolved in the DCC home directory.  The whiteclnt files and the
          addr directories containing them must be writable by the dccifd
          process.

          Option lines in per-user whiteclnt files can be used to modify many
          aspects of dccifd filtering, as described in the main dcc man page.
          For example, an option dcc-off line turns off DCC filtering for
          individual mailboxes.

     -a IGNORE | REJECT | DISCARD
          specifies the action taken when dccifd is in proxy mode with -o and
          DCC server counts or -t thresholds say that a message is unsolicited
          and bulk.  IGNORE causes the message to be unaffected except for
          adding the X-DCC header line to the message.  This turns off all
          filtering except greylisting.

          Spam can also be REJECTed or when in proxy mode with -o accepted and
          silently DISCARDed without being delivered to local mailboxes.  The
          default is REJECT.

          Mail forwarded via IP addresses marked MX or MXDCC in the main
          /var/dcc/whiteclnt file is treated as if -a DISCARD were specified.
          This prevents "bouncing" spam.

          The effects of the -w whiteclnt are not affected by -a.

     -t type,[log-thold,]rej-thold
          sets logging and "spam" thresholds for checksum type.  The checksum
          types are IP, env_From, From, Message-ID, substitute, Received,
          Body, Fuz1, Fuz2, rep-total, and rep.  The first six, IP through
          substitute, have no effect except when a local DCC server configured
          with -K is used.  The substitute thresholds apply to the first sub-
          stitute heading encountered in the mail message.  The string ALL
          sets thresholds for all types, but is unlikely to be useful except
          for setting logging thresholds.  The string CMN specifies the com-
          monly 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 discarded if not whitelisted.

          DCC Reputation thresholds in the commercial version of DCC are con-
          trolled by thresholds on checksum types rep and rep-total.  The DCC
          Reputations of IP addresses that the DCC database says have sent
          more than rep-total,log-thold are computed and messages from those
          addresses are logged.  Messages from IP addresses with DCC Reputa-
          tions of at least the rep,rej-thold rejection threshold can be
          rejected.  The DCC Reputation of an IP address is the percentage of
          its messages known to have been sent to at least 10 recipients.  The
          defaults are equivalent to rep,never and rep-total,never,20.

          Bulk DCC Reputations do not reject mail unless enabled by an
          option DCC-rep-on line a whiteclnt file.

          The checksums of locally whitelisted messages are not checked with
          the DCC server and so only the number of targets of the current copy
          of a whitelisted message are compared against the thresholds.

          The default is ALL,NEVER, so that nothing is discarded, rejected, or
          logged.  A common choice is CMN,25,50 to reject or discard mail with
          common bodies except as overridden by the whitelist of the DCC
          server, the sendmail ${dcc_isspam} and ${dcc_notspam} macros, and
          -g, and -w.

     -g [not-]type
          indicates that whitelisted, 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 8 different sub-
          stitute headers can be specified, but only the checksum of the first
          will be sent to the DCC server.

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

          If logdir is in the form D?dir, log files are put into subdirecto-
          ries of dir the form dir/JJJ where JJJ is the current julian day.
          H?dir puts logs files into subdirectories of the form dir/JJJ/HH
          where HH is the current hour.  M?dir puts log files into subdirecto-
          ries of the form dir/JJJ/HH/MM where MM is the current minute.

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

          Option log-subdirectory-{day,hour,minute} lines in whiteclnt files
          described in dcc(8) are an equivalent mechanism for per-user log
          directories.  Also see the FILES section below concerning the con-
          tents of log files.

     -R rundir
          specifies the "run" directory where the file containing the daemon's
          process ID is stored.  The default value is /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 -l is not used.  The system default is often /tmp.

     -D local-domain
          specifies a host or domain name by which the system is known.  There
          can be several -D settings.

          To find the per-user log directory and whitelist for each mail
          recipient, dccifd must know each recipient's user name.  The ASCII
          protocol used between and the MTA includes an optional user name
          with each SMTP recipient address.  When the user name is absent when
          the ASCII protocol is used or when the subset of ESMTP enabled with
          -o is used, and when the SMTP recipient address includes an at sign
          (@) each mail address is checked against the list of local-domains.
          The part of the recipient address remaining after longest matching
          local-domain (if any) is taken as the user name.  The match is
          anchored at the right or the end of the recipient address.  It must
          start at a period (.) or at sign (@) in the domain name part of the
          address.

          If local-domain starts with an asterisk (*) indicating a wildcard,
          preceding sub-domain names are discarded to compute the user name.
          Otherwise, the computed user name will include any unmatched sub-
          domain names.

          The default value of local-domain when there are no -D settings is
          the host name of the system.

     -r rejection-msg
          specifies the rejection message in -o proxy mode for unsolicited
          bulk mail or for mail temporarily blocked by greylisting when -G is
          specified.  The first -r rejection-msg replaces the default bulk
          mail rejection message, "5.7.1 550 mail %ID from %CIP rejected by
          DCC".  The second replaces "4.2.1 452 mail %ID from %CIP temporary
          greylist embargoed".  The third -r rejection-msg replaces the
          default SMTP rejection message "5.7.1 550 %ID bulk mail reputation;
          see https://commercial-dcc.rhyolite.com/cgi-bin/reps.cgi?tgt=%CIP"
          for mail with bulk DCC Reputations.  If rejection-msg is the zero-
          length string, the -r setting is counted but the corresponding
          default message is not changed.

          Rejection-msg can contain specific information about the mail mes-
          sage.  The following strings starting with % are replaced with the
          corresponding values:
              %ID       message ID such as the unique part of log file name or
                        sendmail queue ID
              %CIP      SMTP client IP address
              %BTYPE    type of DNS blacklist hit, such as "SMTP client",
                        "mail_host", or "URL NS"
              %BTGT     IP address or name declared bad by DNS blacklist
              %BPROBE   domain name found in DNS blacklist such as
                        4.3.2.10.example.com
              %BRESULT  value of the %BPROBE domain name found in DNS black-
                        list

          A common alternate for the bulk mail rejection message is "4.7.1 451
          Access denied by DCC" to tell the sending mail system to continue
          trying.  Use a 4yz response with caution, because it is likely to
          delay for days a delivery failure message for false positives.  If
          the rejection message does not start with an RFC 1893 status code
          and RFC 2821 reply code, 5.7.1 and 550 or 4.2.1 and 452 are used.

          See also -B set:rej-msg to set the status message for mail rejected
          by DNS blacklists.

     -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 system limits on open files, select() bit masks, and so forth.
          Start dccifd with -d and see the starting message in the system log
          to see the limit.

     -B dnsbl-option
          enables DNS white- and blacklist checks of the SMTP client IP
          address, SMTP envelope Mail_From sender domain name, and of host
          names in URLs in the message body.  Body URL blacklisting has too
          many false positives to use on abuse mailboxes.  It is less effec-
          tive than greylisting with dccm(8) or dccifd(8) but can be useful in
          situations where greylisting cannot be used.  It can be combined
          with greylisting.

          Dnsbl-option is either one of the -B set:option forms or
              -B domain[any[,bltype]]
              -B domain[,IPaddr[/xx[&IPmask][,bltype]]]
              -B domain[,IPaddrLO[-IPaddrHI[&IPmask][,bltype]]]
          Domain is a DNS blacklist domain such as example.com that will be
          searched.  The strings any, IPaddr, IPaddr/xx, or IPaddrLO-IPaddrHI,
          specifies which IP addresses found in the DNS blacklist after apply-
          ing the optional IP address mask IPmask say that mail messages
          should be rejected or accepted with -B set:white.  "127.0.0.2" is
          assumed if no address(es) are specified.  IPv6 addresses can be
          specified with the usual colon (:) notation.  Host names can be used
          instead of numeric addresses.  The type of DNS blacklist is speci-
          fied by bltype as name, all-names, IPv4, or IPv6.  Given an envelope
          sender domain name or a domain name in a URL of spam.domain.org and
          a blacklist of type name, spam.domain.org.example.com will be looked
          up.  The names spam.domain.org.example.com, domain.org.example.com,
          and org.example.com will be looked up in blacklists of type
          all-names.  Use name with DNS blacklists that use wildcards for
          speed but all-names for other DNS name blacklists.  Blacklist types
          of IPv4 and IPv6 require that the domain name in a URL sender
          address be resolved into an IPv4 or IPv6 address.  The resolved
          address from the mail message is then written as a reversed string
          of decimal octets to check the DNS blacklist, as in
          2.0.0.127.example.com.

          A domain of "."  and type of name can be used to blacklist domain
          names with specified addresses.  This can be useful to detect URLs
          with domain names listed in a Response Policy Zone (RPZ).  For exam-
          ple, the following can be used to reject mail containing URLs listed
          by a response policy zone that maps evil domain names to 224.0.0.0
          with an informative status message:

            '-Bset:rej-msg=5.7.1 550 %ID %BTYPE \
                  https://example.com/query/dbl?domain=%BTGT'
            -B.,224.0.0.0,name

          More than one blacklist can be specified and blacklists can be
          grouped with -B set:group=X.  All searching within a group of black-
          lists is stopped at the first positive result.

          Unlike dccproc(8), positive results are ignored by dccifd after
          being logged unless an option DNSBL-on or option DNSBLx-on line
          appears a whiteclnt file.

          -B set:no-client
               implies that SMTP client IP addresses and reverse DNS domain
               names should not be checked in the following blacklists.
               -B set:client restores the default for the following black-
               lists.

          -B set:no-mail_host
               implies that SMTP envelope Mail_From sender domain names should
               not be checked in the following blacklists.  -B set:mail_host
               restores the default.

          -B set:no-URL
               says that URLs in the message body should not be checked in the
               in the following blacklists.  -B set:URL restores the default.

          -B set:no-MX
               says MX servers of sender Mail_From domain names and host names
               in URLs should not be checked in the following blacklists.
               -B set:MX restores the default.

          -B set:no-NS
               says DNS servers of sender Mail_From domain names and host
               names in URLs should not be checked in the following black-
               lists.  -B set:NS restores the default.

          -B set:white
               says the DNS list is a whitelist of names or IP addresses.
               -B set:black restores the default.  DNS whitelist usually also
               need -B set:no-mail_host, -B set:no-URL, -B set:no-MX,
               -B set:no-NS, and -B set:no-mail_host.

          -B set:defaults
               is equivalent to all of -B set:black -B set:client
               -B set:mail_host -B set:URL -B set:MX and -B set:NS

          -B set:group=X
               adds following DNS blacklists specified with -B domain[...] to
               group 1, 2, 3, or 4.

          -B set:debug=X
               sets the DNS blacklist logging level

          -B set:msg-secs=S
               limits dccifd to S seconds total for checking all DNS black-
               lists.  The default is 25.

          -B set:URL-secs=S
               limits dccifd to at most S seconds resolving and checking any
               single URL or IP address.  The default is 11.  Some spam con-
               tains dozens of URLs and some "spamvertised" URLs contain host
               names that need minutes to resolve.  Busy mail systems cannot
               afford to spend minutes checking each incoming mail message.

          -B set:rej-msg="rejection message"
               sets the SMTP rejection message for the following blacklists.
               Rejection-msg must be in the same format as for -r.  If
               rejection message is null, the default is restored.  The
               default DNS blacklist rejection message is the first message
               set with -r.

          -B set:max_helpers=X
               sets maximum number of helper processes to X.  In order to use
               typical single-threaded DNS resolver libraries, dccifd uses
               fleets of helper processes.  It is rarely a good idea to change
               the default, which is the same as the maximum number of simul-
               taneous jobs set with -j.

          -B set:progpath=/var/dcc/libexec/dns-helper
               changes the path to the helper program.

     -L ltype,facility.level
          specifies how messages should be logged.  Ltype must be error, info,
          or off to indicate which of the two types of messages are being con-
          trolled or to turn off all syslog(3) messages from dccifd.  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

     dccifd normally sends counts of mail rejected and so forth to the system
     log at midnight.  The SIGUSR1 signal sends an immediate report to the
     system log.  The reports will be repeated every 24 hours at the same
     minute as the signal instead of at midnight.

   Protocol
     Unless SMTP proxy mode is enabled with -o, 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.

     Instead of the ASCII protocol, a subset of ESMTP is enabled by -o.  Only
     the familiar HELO, EHLO, Mail, Rcpt, DATA, RSET, and QUIT commands and
     the Postfix extensions XFORWARD and XCLIENT are honored.  Since SMTP has
     no provisions for user names, the protocol enabled by -o depends on a
     list of local domain names specified with -D to find per-user log direc-
     tories and whitelist files.  If neither XFORWARD nor XCLIENT are used,
     dccifd uses the IP address of the MTA and the value of the HELO command.

     In the ASCII protocol, each of the following lines are sent in order to
     dccifd.  Each ends with a newline ('\n') character.
       options     zero or more blank-separated strings among:
                     spam        the message is already known to be spam
                     body        return all of the headers with the added
                                 X-DCC header line and the body
                     header      return the X-DCC header
                     cksums      return X-DCC header and the checksums for the
                                 message.
                     query       ask the DCC server about the message without
                                 reporting it, as if dccifd were running with
                                 -Q.
                     grey-off    disable greylisting for this message.
                     grey-query  only query the greylist server for this mes-
                                 sage.  -G on must be in use.
                     no-reject   has the same effect as running dccifd with
                                 -a IGNORE.  It suppresses the overall, one
                                 character line 'R' result.  This can be use-
                                 ful when using dccifd only for greylisting.
                     log         ensure that this message is logged as if
                                 dccifd were running with -t -all,0,
                     rcvd-next   causes dccifd to skip a Received: header
                                 looking for the client IP address and HELO
                                 value.  Each additional rcvd-next option
                                 increases the number of Received: headers
                                 skipped.  MX or MXDCC in the global
                                 -w whiteclnt file usually work better.
       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.  The
                   string "0.0.0.0\n" is understood the same as the null
                   string, meaning that both the IP address and host name are
                   absent.  If the client IP address is absent, then the IP
                   address and host name are taken from the first non-local
                   Received header if it has the standard "name (name [IP
                   address])..." format.  Non-standard Received headers com-
                   monly added by qmail as well as Received headers specifying
                   IP addresses marked MX or MXDCC in the global -w whiteclnt
                   file are skipped.
       HELO        SMTP HELO value or nothing, followed by a newline ('\n')
                   character.  If the HELO value is null and the IP address of
                   the SMTP client are not supplied, they will be taken from
                   the same Received: header that supplies the IP address.
       sender      or SMTP Mail From command value for the env_from checksum.
                   If the sender is null, the contents of the first Return-
                   Path: or UNIX style From_ header is used.
       recipients  or SMTP Rcpt To recipient mailboxes followed by correspond-
                   ing local user names, one (mailbox,user) pair to a line.
                   Each optional local user name is separated from the corre-
                   sponding mailbox recipient address by a carriage return
                   ('\r').  A local user name can be null if it is not known,
                   but each recipient mailbox must be non-null.  If there are
                   no lines of (mailbox,user) pairs and if the spam option is
                   not included, then the query is assumed.  Mailboxes without
                   user names will lack per-user log files and cannot invoke a
                   per-user whiteclnt file.

     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:
       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 characters indicating the disposition of the message
     for each corresponding recipient:
       A    deliver the message
       G    discard the message during a greylist embargo
       R    discard the message as spam
     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 accept-
     ing 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.
     /var/dcc/libexec/start-dccifd
                 or
     /var/dcc/libexec/rcDCC
                 are scripts used to start the daemon.
     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
                 unless modified by ./configure --with-max-log-size=xx The
                 checksums for the message follow the body.  They are followed
                 by lines indicate that one of the checksums is white- or
                 blacklisted by the -w whiteclnt file.  Each log file ends
                 with the X-DCC header line added to the message and the dis-
                 position 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 /var/dcc/whiteclnt file.
     dccifd.pid  in the -R rundir directory contains daemon's process ID.


EXAMPLES

     Dccifd can be used as Postfix Before-Queue Content filter.  In some tests
     these values for -p and -o in /var/dcc/dcc_conf.

         DCCIFD_ENABLE=on
         DCCIFD_ARGS="-p 127.0.0.1,10025,127.0.0.1/32 -o 127.0.0.1,10026   ..."

     worked with these lines in /etc/postfix/master.cf

         smtp      inet  n       -       n       -       -       smtpd
             -o smtpd_proxy_filter=127.0.0.1:10025
         127.0.0.1:10026 inet n  -       n       -       -       smtpd
             -o smtpd_authorized_xforward_hosts=127.0.0.0/8
             -o smtpd_client_restrictions=
             -o smtpd_helo_restrictions=
             -o smtpd_sender_restrictions=
             -o smtpd_recipient_restrictions=permit_mynetworks,reject
             -o smtpd_data_restrictions=
             -o mynetworks=127.0.0.0/8
             -o receive_override_options=no_unknown_recipient_checks


SEE ALSO

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


HISTORY

     Implementation of dccifd Distributed Checksum Clearinghouses are based on
     an idea of Paul Vixie with code designed and written at Rhyolite Software
     starting in 2000.  was started at Rhyolite Software in 2002.  This docu-
     ment describes version 1.3.163.


BUGS

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

     By default dccifd look for its UNIX domain socket in the DCC home direc-
     tory, but dccm(8) looks in its -R rundir.

     Systems without setrlimit(2) and getrlimit(2) RLIMIT_NOFILE 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(): Result too large
     A fix is to use a smaller value for -j or to allow dccifd to open more
     files.

                                March 09, 2018

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