dccifd(8)             Distributed Checksum Clearinghouse             dccifd(8)

NNAAMMEE
     ddcccciiffdd -- Distributed Checksum Clearinghouse Interface Daemon

SSYYNNOOPPSSIISS
     ddcccciiffdd [--VVddbbxxAANNQQ] [--GG _o_n | _o_f_f | _n_o_I_P | _I_P_m_a_s_k_/_x_x] [--hh _h_o_m_e_d_i_r] [--II _u_s_e_r]
            [--pp _/_s_o_c_k | _h_o_s_t_,_p_o_r_t_,_r_h_o_s_t_/_b_i_t_s] [--oo _/_s_o_c_k | _h_o_s_t_,_p_o_r_t]
            [--DD _l_o_c_a_l_-_d_o_m_a_i_n] [--mm _m_a_p] [--ww _w_h_i_t_e_c_l_n_t] [--UU _u_s_e_r_d_i_r_s]
            [--aa _I_G_N_O_R_E | _R_E_J_E_C_T | _D_I_S_C_A_R_D] [--tt _t_y_p_e_,[_l_o_g_-_t_h_o_l_d_,]_r_e_j_-_t_h_o_l_d]
            [--gg [_n_o_t_-]_t_y_p_e] [--SS _h_e_a_d_e_r] [--ll _l_o_g_d_i_r] [--RR _r_u_n_d_i_r]
            [--rr _r_e_j_e_c_t_i_o_n_-_m_s_g] [--TT _t_m_p_d_i_r] [--jj _m_a_x_j_o_b_s]
            [--BB _d_n_s_b_l_-_o_p_t_i_o_n] [--LL _l_t_y_p_e_,_f_a_c_i_l_i_t_y_._l_e_v_e_l]

DDEESSCCRRIIPPTTIIOONN
     ddcccciiffdd 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 ddcccciiffdd which in turn reports related checksums to the near-
     est DCC server and adds an _X_-_D_C_C SMTP header line to the message.  The
     MTA is told to reject the message if it is unsolicited bulk.

     DDcccciiffdd is similar to the DCC sendmail milter interface, dccm(8) and the
     DCC Procmail interface, dccproc(8).  DDcccciiffdd 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.  DDcccciiffdd responds with
     an indication of whether the message is unsolicited bulk and an optional
     copy of the message with an _X_-_D_C_C header added.  The ASCII protocol is
     described below and in the _i_n_c_l_u_d_e_/_d_c_c_i_f_._h file in the DCC source.  There
     is a sample C interface routine in the _d_c_c_l_i_b_/_d_c_c_i_f_._c file in the DCC
     source and the _d_c_c_l_i_b_._a library generated from the source.  A _P_e_r_l ver-
     sion of the interface routine is in _d_c_c_i_f_d_/_d_c_c_i_f_._p_l.  Test or demonstra-
     tion programs in the style of dccproc(8) that use those interface rou-
     tines are in _d_c_c_i_f_d_/_d_c_c_i_f_-_t_e_s_t.

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

     Since the checksums of messages that are whitelisted locally by the --ww
     _w_h_i_t_e_c_l_n_t file are not reported to the DCC server, ddcccciiffdd knows nothing
     about the total recipient counts for their checksums and so cannot add
     _X_-_D_C_C header lines to such messages.

     Enable the daemon and put its parameters in the _d_c_c___c_o_n_f file and start
     the daemon with the _s_t_a_r_t_-_d_c_c_i_f_d script.

     The list of servers that ddcccciiffdd contacts is in the memory mapped file _m_a_p
     shared by local DCC clients.  The file is  maintained with cdcc(8).

   OOPPTTIIOONNSS
     The following options are available:

     --VV   displays the version of ddcccciiffdd.

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

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

     --xx   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, ddcccciiffdd 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 --xx, 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.

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

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

     --QQ   only queries the DCC server about the checksums of messages instead
          of reporting and querying.  This is useful when ddcccciiffdd 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 _M_X_D_C_C lines in the global _w_h_i_t_e_c_l_n_t file for
          your MX mail servers that use DCC than --QQ.

     --GG _o_n | _o_f_f | _n_o_I_P | _I_P_m_a_s_k_/_x_x
          controls _g_r_e_y_l_i_s_t_i_n_g.  At least one working greylist server must be
          listed in the _m_a_p file in the DCC home directory.  If more than one
          is named, they must "flood" or change checksums and they must use
          the same --GG parameters.  See dccd(8).  Usually all dccm or dccifd
          DCC client processes use the same --GG parameters.

          _I_P_m_a_s_k_/_x_x and _n_o_I_P remove part or all of the IP address from the
          greylist triple.  The CIDR block size, _x_x, 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.  _I_P_m_a_s_k_/_9_6 differs
          from _n_o_I_P for IPv4 addresses, because the former retains the IPv4 to
          IPv6 mapping prefix.

     --hh _h_o_m_e_d_i_r
          overrides the default DCC home directory, _/_v_a_r_/_d_c_c.

     --II _u_s_e_r
          specifies the UID and GID of the process.

     --pp _/_s_o_c_k_/_n_a_m_e | _h_o_s_t_,_p_o_r_t_,_r_h_o_s_t_/_b_i_t_s
          overrides the default address at which programs contact ddcccciiffdd.  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 ddcccciiffdd.  127.0.0.1 or _l_o_c_a_l_h_o_s_t are common choices for
          _h_o_s_t.  The string _@ specifies IN_ADDRANY or all local IP addresses.
          127.0.0.0/8 is a common choice for _r_h_o_s_t_/_b_i_t_s.

     --oo _/_s_o_c_k | _h_o_s_t_,_p_o_r_t
          enables SMTP proxy mode instead of the ASCII protocol and specifies
          the output connection when ddcccciiffdd acts as an SMTP proxy.  It is the
          address of the SMTP server for which ddcccciiffdd acts as SMTP client.
          When _/_s_o_c_k is _/_d_e_v_/_n_u_l_l, ddcccciiffdd 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 ddcccciiffdd in SMTP proxy mode is specified with ----pp.  For
          example, --pp _1_2_7_._0_._0_._1_,_1_0_0_2_5_,_1_2_7_._0_._0_._1_/_3_2 --oo _1_2_7_._0_._0_._1_,_1_0_0_2_6 could be
          used to connect ddcccciiffdd 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.

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

     --ww _w_h_i_t_e_c_l_n_t
          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_-_D_C_C
          header, and whose checksums should not be reported to the DCC
          server.

          If the pathname _w_h_i_t_e_c_l_n_t is not absolute, it is relative to the DCC
          home directory.

          The format of the ddcccciiffdd whiteclnt file is the same as the _w_h_i_t_e_l_i_s_t
          files used by dbclean(8) and the _w_h_i_t_e_c_l_n_t file used by dccproc(8).
          See dcc(8) for a description of DCC white and blacklists.  Because
          the contents of the _w_h_i_t_e_c_l_n_t file are used frequently, a companion
          file is automatically created and maintained.  It has the same path-
          name but with an added suffix of _._d_c_c_w 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_-_D_C_C header line by ddcccciiffdd A whitelist entry for a checksum also
          prevents rejecting or discarding the message based on DCC recipient
          counts as specified by --aa and --tt.  Otherwise, one or more checksums
          with blacklisting entries ("MANY") cause all of the message's check-
          sums to be reported to the server with an addressee count of "MANY".

          If the message has a single recipient, an _e_n_v___T_o _w_h_i_t_e_c_l_n_t entry of
          "OK" for the checksum of its recipient address acts like any other
          _w_h_i_t_e_c_l_n_t 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 _w_h_i_t_e_c_l_n_t file,
          ddcccciiffdd 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 don't want filtering.

     --UU _u_s_e_r_d_i_r_s
          enables per-user _w_h_i_t_e_c_l_n_t files and log directories.  Each target
          of a message can have a directory of log files named
          _u_s_e_r_d_i_r_s_/_a_d_d_r_/_l_o_g where _a_d_d_r is the local user or mailbox name com-
          puted by the MTA.  The name of each user's log directory must be
          _l_o_g.  If it is not absolute, _u_s_e_r_d_i_r_s is relative to the DCC home
          directory.  The directory containing the log files must be named _l_o_g
          and it must be writable by the ddcccciiffdd 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
          ddcccciiffdd process, but they have _g_r_o_u_p and _o_t_h_e_r read and write permis-
          sions copied from the corresponding _l_o_g directory.  To ensure the
          privacy of mail, it may be good to make the directories readable
          only by _o_w_n_e_r and _g_r_o_u_p, and to use a cron script that changes the
          owner of each file to match the grandparent _a_d_d_r directory.

          There can also be a per -user whitelist file named
          _u_s_e_r_d_i_r_s_/_a_d_d_r_/_w_h_i_t_e_c_l_n_t for each address _a_d_d_r_. Any checksum that is
          not white- or blacklisted by an individual addressee's _w_h_i_t_e_c_l_n_t
          file  is checked in the main --ww --wwhhiitteeccllnntt file.  A missing per-
          addressee _w_h_i_t_e_c_l_n_t 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 _w_h_i_t_e_c_l_n_t files and the _a_d_d_r directories
          containing them must be writable by the ddcccciiffdd process.

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

     --aa _I_G_N_O_R_E | _R_E_J_E_C_T | _D_I_S_C_A_R_D
          specifies the action taken when ddcccciiffdd is in proxy mode with --oo and
          DCC server counts or --tt thresholds say that a message is unsolicited
          and bulk.  _I_G_N_O_R_E causes the message to be unaffected except for
          adding the _X_-_D_C_C header line to the message.  This turns off DCC
          filtering.

          Spam can also be _R_E_J_E_C_Ted or (when in proxy mode with --oo) accepted
          and silently _D_I_S_C_A_R_Ded without being delivered to local mailboxes.
          The default is _R_E_J_E_C_T.

          Mail forwarded via IP addresses marked _M_X or _M_X_D_C_C in the main
          _w_h_i_t_e_c_l_n_t file is treated as if --aa _D_I_S_C_A_R_D were specified.  This
          prevents "bouncing" spam.

          The effects of the --ww _w_h_i_t_e_c_l_n_t are not affected by --aa.

     --tt _t_y_p_e_,[_l_o_g_-_t_h_o_l_d_,]_r_e_j_-_t_h_o_l_d
          sets logging and "spam" thresholds for checksum _t_y_p_e.  The checksum
          types are _I_P, _e_n_v___F_r_o_m, _F_r_o_m, _M_e_s_s_a_g_e_-_I_D, _s_u_b_s_t_i_t_u_t_e, _R_e_c_e_i_v_e_d,
          _B_o_d_y, _F_u_z_1, _F_u_z_2, _r_e_p_-_t_o_t_a_l, and _r_e_p.  The first six, _I_P through
          _s_u_b_s_t_i_t_u_t_e, have no effect except when a local DCC server configured
          with --KK is used.  The _s_u_b_s_t_i_t_u_t_e thresholds apply to the first sub-
          stitute heading encountered in the mail message.  The string _A_L_L
          sets thresholds for all types, but is unlikely to be useful except
          for setting logging thresholds.  The string _C_M_N specifies the com-
          monly used checksums _B_o_d_y, _F_u_z_1, and _F_u_z_2.  _R_e_j_-_t_h_o_l_d and _l_o_g_-_t_h_o_l_d
          must be numbers, the string _N_E_V_E_R, or the string _M_A_N_Y 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.

          _L_o_g_-_t_h_o_l_d 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.

          _R_e_j_-_t_h_o_l_d 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 the DCC are
          controlled by thresholds on checksum types _r_e_p and _r_e_p_-_t_o_t_a_l.  Mes-
          sages from an IP address that the DCC database says has sent more
          than --tt _r_e_p_-_t_o_t_a_l_,_l_o_g_-_t_h_o_l_d messages are logged.  A DCC Reputation
          is computed for messages received from IP addresses that have sent
          more than --tt _r_e_p_-_t_o_t_a_l_,_l_o_g_-_t_h_o_l_d messages.  The DCC Reputation of an
          IP address is the percentage of its messages that have been detected
          as bulk or having at least 10 recipients.  The defaults are equiva-
          lent to --tt _r_e_p_,_n_e_v_e_r and --tt _r_e_p_-_t_o_t_a_l_,_n_e_v_e_r_,_2_0.

          Bad DCC Reputations do not reject mail unless enabled by an _o_p_t_i_o_n
          _D_C_C_-_r_e_p_-_o_n line in a _w_h_i_t_e_c_l_n_t 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 _A_L_L_,_N_E_V_E_R, so that nothing is discarded, rejected, or
          logged.  A common choice is _C_M_N_,_2_5_,_5_0 to reject or discard mail with
          common bodies except as overridden by the whitelist of the DCC
          server, the sendmail _$_{_d_c_c___i_s_s_p_a_m_} and _$_{_d_c_c___n_o_t_s_p_a_m_} macros, and
          --gg, and --ww.

     --gg [_n_o_t_-]_t_y_p_e
          indicates that whitelisted, _O_K or _O_K_2, counts from the DCC server
          for a type of checksum are to be believed.  They should be ignored
          if prefixed with _n_o_t_-.  _T_y_p_e is one of the same set of strings as
          for --tt.  Only _I_P, _e_n_v___F_r_o_m, and _F_r_o_m are likely choices.  By default
          all three are honored, and hence the need for _n_o_t_-.

     --SS _h_d_r
          adds to the list of substitute or locally chosen headers that are
          checked with the --ww _w_h_i_t_e_c_l_n_t file and sent to the DCC server.  The
          checksum of the last header of type _h_d_r found in the message is
          checked.  _H_d_r can be _H_E_L_O to specify the SMTP envelope HELO value.
          _H_d_r can also be _m_a_i_l___h_o_s_t to specify the host name from the
          Mail_from value in the SMTP envelope.  As many as six different sub-
          stitute headers can be specified, but only the checksum of the first
          of the six will be sent to the DCC server.

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

          See the FILES section below concerning the contents of the files.
          See also the _o_p_t_i_o_n _l_o_g_-_s_u_b_d_i_r_e_c_t_o_r_y_-_{_d_a_y_,_h_o_u_r_,_m_i_n_u_t_e_} lines in
          _w_h_i_t_e_c_l_n_t files described in dcc(8).

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

     --RR _r_u_n_d_i_r
          specifies the "run" directory where the file containing the daemon's
          process ID is stored.  The default value is _/_v_a_r_/_r_u_n_/_d_c_c.

     --TT _t_m_p_d_i_r
          changes the default directory for temporary files from the default.
          The default is the directory specified with --ll or the system default
          if --ll is not used.  The system default is often _/_t_m_p.

     --DD _l_o_c_a_l_-_d_o_m_a_i_n
          specifies a host or domain name by which the system is known.  There
          can be several --DD settings.

          To find the per-user log directory and whitelist for each mail
          recipient, ddcccciiffdd 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
          --oo is used, and when the SMTP recipient address includes an _a_t _s_i_g_n
          (@) each mail address is checked against the list of _l_o_c_a_l_-_d_o_m_a_i_ns.
          The part of the recipient address remaining after longest matching
          _l_o_c_a_l_-_d_o_m_a_i_n (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 _a_t _s_i_g_n (@) in the domain name part of the
          address.

          If _l_o_c_a_l_-_d_o_m_a_i_n 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 _l_o_c_a_l_-_d_o_m_a_i_n when there are no --DD settings is
          the host name of the system.

     --rr _r_e_j_e_c_t_i_o_n_-_m_s_g
          specifies the rejection message in --oo proxy mode for unsolicited
          bulk mail or for mail temporarily blocked by _g_r_e_y_l_i_s_t_i_n_g when --GG is
          specified.  The first --rr _r_e_j_e_c_t_i_o_n_-_m_s_g 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 --rr _r_e_j_e_c_t_i_o_n_-_m_s_g replaces the
          default SMTP rejection message "5.7.1 550 %ID bad reputation; see
          http://commercial-dcc.rhyolite.com/cgi-bin/reps.cgi?tgt=%CIP" for
          mail with bad DCC Reputations.  If _r_e_j_e_c_t_i_o_n_-_m_s_g is the zero-length
          string, the --rr setting is counted but the corresponding message is
          not changed.

          _R_e_j_e_c_t_i_o_n_-_m_s_g 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 --BB _s_e_t_:_r_e_j_-_m_s_g_=_r_e_j_e_c_t_i_o_n_-_m_s_g to set the status message for
          mail rejected by DNS blacklists.

     --jj _m_a_x_j_o_b_s
          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 ddcccciiffdd with --dd and see the starting message in the system log
          to see the limit.

     --BB _d_n_s_b_l_-_o_p_t_i_o_n
          enables DNS 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 posi-
          tives to use on abuse mailboxes.  It is less effective than
          greylisting with dccm(8) or dccifd(8) but can be useful in situa-
          tions where greylisting cannot be used.

          _D_n_s_b_l_-_o_p_t_i_o_n is either one of the --BB _s_e_t_:_o_p_t_i_o_n forms or
              --BB _d_o_m_a_i_n[_,_I_P_a_d_d_r[_/_x_x[_,_b_l_t_y_p_e]]]
          _D_o_m_a_i_n is a DNS blacklist domain such as example.com that will be
          searched.  _I_P_a_d_d_r[_/_x_x_x] is the string "any" an IP address in the DNS
          blacklist that indicates that the mail message should be rejected,
          or a CIDR block covering results from the DNS blacklist.
          "127.0.0.2" is assumed if _I_P_a_d_d_r is absent.  IPv6 addresses can be
          specified with the usual colon (:) notation.  Names can be used
          instead of numeric addresses.  The type of DNS blacklist is speci-
          fied by _b_l_t_y_p_e as _n_a_m_e, _I_P_v_4, or _I_P_v_6.  Given an envelope sender
          domain name or a domain name in a URL of spam.domain.org and a
          blacklist of type _n_a_m_e, spam.domain.org.example.com will be tried.
          Blacklist types of _I_P_v_4 and _I_P_v_6 require that the domain name in a
          URL sender address be resolved into an IPv4 or IPv6 address.  The
          address is then written as a reversed string of decimal octets to
          check the DNS blacklist, as in 2.0.0.127.example.com,

          More than one blacklist can be specified and blacklists can be
          grouped.  All searching within a group is stopped at the first posi-
          tive result.

          Positive results are ignored after being logged unless an
          _o_p_t_i_o_n _D_N_S_B_L_-_o_n line appears in the global or per-user _w_h_i_t_e_c_l_n_t
          file.

          --BB _s_e_t_:_n_o_-_c_l_i_e_n_t
               says that SMTP client IP addresses and reverse DNS domain names
               should not be checked in the following blacklists.
               --BB _s_e_t_:_c_l_i_e_n_t restores the default for the following black-
               lists.

          --BB _s_e_t_:_n_o_-_m_a_i_l___h_o_s_t
               says that SMTP envelope Mail_From sender domain names should
               not be checked in the following blacklists.  --BB _s_e_t_:_m_a_i_l___h_o_s_t
               restores the default.

          --BB _s_e_t_:_n_o_-_U_R_L
               says that URLs in the message body should not be checked in the
               in the following blacklists.  --BB _s_e_t_:_U_R_L restores the default.

          --BB _s_e_t_:_n_o_-_M_X
               says MX servers of sender Mail_From domain names and host names
               in URLs should not be checked in the following blacklists.
               --BB _s_e_t_:_M_X restores the default.

          --BB _s_e_t_:_n_o_-_N_S
               says DNS servers of sender Mail_From domain names and host
               names in URLs should not be checked in the following black-
               lists.  --BB _s_e_t_:_N_S restores the default.

          --BB _s_e_t_:_d_e_f_a_u_l_t_s
               is equivalent to all of --BB _s_e_t_:_n_o_-_t_e_m_p_-_f_a_i_l --BB _s_e_t_:_c_l_i_e_n_t
               --BB _s_e_t_:_m_a_i_l___h_o_s_t --BB _s_e_t_:_U_R_L --BB _s_e_t_:_M_X and --BB _s_e_t_:_N_S

          --BB _s_e_t_:_g_r_o_u_p_=_X
               adds later DNS blacklists specified with
                   --BB _d_o_m_a_i_n[_,_I_P_a_d_d_r[_/_x_x[_,_b_l_t_y_p_e]]]
               to group 1, 2, or 3.

          --BB _s_e_t_:_d_e_b_u_g_=_X
               sets the DNS blacklist logging level

          --BB _s_e_t_:_m_s_g_-_s_e_c_s_=_S
               limits ddcccciiffdd to _S seconds total for checking all DNS black-
               lists.  The default is 25.

          --BB _s_e_t_:_U_R_L_-_s_e_c_s_=_S
               limits ddcccciiffdd to at most _S seconds resolving and checking any
               single URL.  The default is 11.  Some spam contains dozens of
               URLs and that some "spamvertised" URLs contain host names that
               need minutes to resolve.  Busy mail systems cannot afford to
               spend minutes checking each incoming mail message.

          --BB _s_e_t_:_r_e_j_-_m_s_g_=_r_e_j_e_c_t_i_o_n_-_m_s_g
               sets the SMTP rejection message for the following blacklists.
               _R_e_j_e_c_t_i_o_n_-_m_s_g must be in the same format as for --rr.  If
               _r_e_j_e_c_t_i_o_n_-_m_s_g is null, the default is restored.  The default
               DNS blacklist rejection message is the first message set with
               --rr.

          --BB _s_e_t_:_t_e_m_p_-_f_a_i_l
               causes ddcccciiffdd to the MTA to answer the SMTP DATA command with
                  452 4.2.1 mail %ID from %CIP temporary delayed for DNSBL
               if any DNS answer required for a DNSBL in the current group
               times out, including resolving names in URLs.

          --BB _s_e_t_:_n_o_-_t_e_m_p_-_f_a_i_l
               restores the default of assuming a negative answer for DNS
               responses that take too long.

          --BB _s_e_t_:_m_a_x_j_o_b_s_=_X
               sets maximum number of helper processes to _X.  In order to use
               typical single-threaded DNS resolver libraries, ddcccciiffdd 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 --jj.

          --BB _s_e_t_:_p_r_o_g_p_a_t_h_=_/_v_a_r_/_d_c_c_/_l_i_b_e_x_e_c_/_d_n_s_-_h_e_l_p_e_r
               changes the path to the helper program.

     --LL _l_t_y_p_e_,_f_a_c_i_l_i_t_y_._l_e_v_e_l
          specifies how messages should be logged.  _L_t_y_p_e must be _e_r_r_o_r, _i_n_f_o,
          or _o_f_f to indicate which of the two types of messages are being con-
          trolled or to turn off all syslog(3) messages from ddcccciiffdd.  _L_e_v_e_l
          must be a syslog(3) level among _E_M_E_R_G, _A_L_E_R_T, _C_R_I_T, _E_R_R, _W_A_R_N_I_N_G,
          _N_O_T_I_C_E, _I_N_F_O, and _D_E_B_U_G.  _F_a_c_i_l_i_t_y must be among _A_U_T_H, _A_U_T_H_P_R_I_V,
          _C_R_O_N, _D_A_E_M_O_N, _F_T_P, _K_E_R_N, _L_P_R, _M_A_I_L, _N_E_W_S, _U_S_E_R, _U_U_C_P, and _L_O_C_A_L_0
          through _L_O_C_A_L_7.  The default is equivalent to
                --LL _i_n_f_o_,_M_A_I_L_._N_O_T_I_C_E --LL _e_r_r_o_r_,_M_A_I_L_._E_R_R

     ddcccciiffdd 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.

   PPrroottooccooll
     DDcccciiffdd 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 --oo.  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 --oo depends on a
     list of local domain names specified with --DD to find per-user log direc-
     tories and whitelist files.  If neither XFORWARD nor XCLIENT are used,
     ddcccciiffdd 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
     ddcccciiffdd.  Each ends with a newline ('\n') character.
       options     zero or more blank-separated strings among:
                     _s_p_a_m        the message is already known to be spam
                     _b_o_d_y        return all of the headers with the added
                                 _X_-_D_C_C header line and the body
                     _h_e_a_d_e_r      return the _X_-_D_C_C header
                     _q_u_e_r_y       ask the DCC server about the message without
                                 reporting it, as if ddcccciiffdd were running with
                                 --QQ.
                     _g_r_e_y_-_q_u_e_r_y  only query the greylist server for this mes-
                                 sage.  --GG _o_n must be in use.
                     _n_o_-_r_e_j_e_c_t   suppress the overall, one character line 'R'
                                 result.  This can be useful when using ddcccciiffdd
                                 only for greylisting.
                     _l_o_g         ensure that this message is logged as if
                                 ddcccciiffdd were running with --tt --aallll,,00,,
       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 _M_X or _M_X_D_C_C in the global --ww _w_h_i_t_e_c_l_n_t
                   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 _M_a_i_l _F_r_o_m 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 _R_c_p_t _T_o 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 _s_p_a_m option is
                   not included, then the _q_u_e_r_y is assumed.  Mailboxes without
                   user names will lack per-user log files and will not invoke
                   a per-user whitelist.

     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).

     DDcccciiffdd 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 _b_o_d_y or _h_e_a_d_e_r strings are in the first line of _o_p_t_i_o_n_s
     sent by the MTA to the daemon, then the _X_-_D_C_C header line or the entire
     body with the _X_-_D_C_C header line follows.

FFIILLEESS
     /var/dcc    is the DCC home directory in which other files are found.
     /var/dcc/libexec/start-dccifd
                 and
     /var/dcc/libexec/rcDCC
                 are scripts used to start 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 --ll and containing
                 marked mail.  Each file in the directory contains one mes-
                 sage, at least one of whose checksums reached its --tt 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 _._/_c_o_n_f_i_g_u_r_e _-_-_w_i_t_h_-_m_a_x_-_l_o_g_-_s_i_z_e_=_x_x 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 --ww _w_h_i_t_e_c_l_n_t file.  Each log file ends
                 with the _X_-_D_C_C 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 _w_h_i_t_e_c_l_n_t file.
     dccifd.pid  in the --RR _r_u_n_d_i_r directory contains daemon's process ID.

EEXXAAMMPPLLEESS
     Dccifd can be used as Postfix Before-Queue Content filter.  In some tests
     these values for --pp and --oo in _d_c_c___c_o_n_f.

         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

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

HHIISSTTOORRYY
     Implementation of ddcccciiffdd 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 1.3.103.

BBUUGGSS
     ddcccciiffdd uses --tt where dccproc(8) uses --cc.

     By default ddcccciiffdd look for its UNIX domain socket in the DCC home direc-
     tory, but dccm(8) looks in its --RR _r_u_n_d_i_r.

     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 --jj.  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 --jj or to allow ddcccciiffdd to open more
     files.

                               February 26, 2009