dccifd(8) FreeBSD System Manager's Manual dccifd(8) NNAAMMEE ddcccciiffdd -- Distributed Checksum Clearinghouse Interface Daemon SSYYNNOOPPSSIISS ddcccciiffdd [--VVddbbxxAANNPPQQ] [--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 | _l_h_o_s_t_,_l_p_o_r_t_,_r_h_o_s_t] [--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 _/_v_a_r_/_d_c_c_/_b_u_i_l_d_/_d_c_c_/_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 _/_v_a_r_/_d_c_c_/_d_c_c___c_o_n_f file and start the daemon with the _/_v_a_r_/_d_c_c_/_l_i_b_e_x_e_c_/_r_c_D_C_C or _/_v_a_r_/_d_c_c_/_l_i_b_e_x_e_c_/_s_t_a_r_t_-_d_c_c_i_f_d scripts. The list of servers that ddcccciiffdd contacts is in the memory mapped file _/_v_a_r_/_d_c_c_/_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. Two or more --VV options show the op- tions with which it was built. --dd enables debugging output from the DCC client software. Additional --dd options increase the number of messages. A single --dd logs aborted SMTP transactions including those from some "dictionary at- tacks." --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 mail message is logged, rejected, and otherwise han- dled the same. --PP 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 ddcccciiffdd knows that a mail message is extremely bulky and probably spam. For example, mail from a sender that is blacklisted in _w_h_i_t_e_c_l_n_t gets an X-DCC header that includes _b_u_l_k. To acommodate that bug in SpamAssassin, by default whenever ddcccciiffdd generates an X-DCC header containing "bulk", it also forces the _B_o_d_y count to "many". --PP turns off that kludge and the _B_o_d_y contains the count from the DCC server. --QQ only queries the DCC server about the checksums of messages instead of reporting. 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 _/_v_a_r_/_d_c_c_/_w_h_i_t_e_c_l_n_t file for your MX mail servers that use DCC than to use --QQ with ddcccciiffdd. Do not use --QQ 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 --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 _/_v_a_r_/_d_c_c_/_m_a_p file. If more than one is named, they must "flood" or change checksums and they must use the same --GG pa- rameters. See dccd(8). Usually all dccm or dccifd DCC client pro- cesses 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. --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 | _l_h_o_s_t_,_l_p_o_r_t_,_r_h_o_s_t 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 name or IP addresses of computers that can use ddcccciiffdd. 127.0.0.1 is a common choices for _l_h_o_s_t. The string _* for _l_h_o_s_t specifies IN_ADDRANY or all local IP addresses. 127.0.0.1 is a common choice for _r_h_o_s_t, but it can be a _x_x_x_._x_x_x_._x_x_x_._x_x_x_/_m_m CIDR block or a _x_x_x_._x_x_x_._x_x_x_._x_x_x_-_y_y_y_._y_y_y_._y_y_y_._y_y_y range of IPv4 or IPv6 addresses. --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 _/_v_a_r_/_d_c_c_/_m_a_p. 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 _/_v_a_r_/_d_c_c_/_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 main- tained. It has the same pathname 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 re- cipient counts as specified by --aa and --tt. 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 _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 users who 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 addressee _a_d_d_r_. Any checksum that is not white- or blacklisted by an individual addressee's per-user _w_h_i_t_e_c_l_n_t file is checked in the main _/_v_a_r_/_d_c_c_/_w_h_i_t_e_c_l_n_t 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 re- solved 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 in- dividual 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 all filtering except greylisting. 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 _/_v_a_r_/_d_c_c_/_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 DCC are con- trolled by thresholds on checksum types _r_e_p and _r_e_p_-_t_o_t_a_l. The DCC Reputations of IP addresses that the DCC database says have sent more than _r_e_p_-_t_o_t_a_l_,_l_o_g_-_t_h_o_l_d are computed and messages from those addresses are logged. Messages from IP addresses with DCC Reputa- tions of at least the _r_e_p_,_r_e_j_-_t_h_o_l_d rejection threshold can be re- jected. 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 _r_e_p_,_n_e_v_e_r and _r_e_p_-_t_o_t_a_l_,_n_e_v_e_r_,_2_0. Bulk 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 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 8 different sub- stitute headers can be specified, but only the checksum of the first 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. If _l_o_g_d_i_r is in the form _D_?_d_i_r, log files are put into subdirecto- ries of _d_i_r the form _d_i_r_/_J_J_J where _J_J_J is the current julian day. _H_?_d_i_r puts logs files into subdirectories of the form _d_i_r_/_J_J_J_/_H_H where _H_H is the current hour. _M_?_d_i_r puts log files into subdirecto- ries of the form _d_i_r_/_J_J_J_/_H_H_/_M_M where _M_M is the current minute. The directory is relative to the DCC home directory if it is not ab- solute _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) are an equivalent mechanism for per-user log di- rectories. Also see the FILES section below concerning the contents of log files. --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 re- cipient, 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 an- chored 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-do- main 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 de- fault 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 _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 de- fault 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 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 white- and blacklist checks of the SMTP client IP ad- dress, 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 effective than greylisting with dccm(8) or dccifd(8) but can be useful in sit- uations where greylisting cannot be used. It can be combined with greylisting. _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[any[_,_b_l_t_y_p_e]] --BB _d_o_m_a_i_n[_,_I_P_a_d_d_r[_/_x_x[_&_I_P_m_a_s_k][_,_b_l_t_y_p_e]]] --BB _d_o_m_a_i_n[_,_I_P_a_d_d_r_L_O[_-_I_P_a_d_d_r_H_I[_&_I_P_m_a_s_k][_,_b_l_t_y_p_e]]] _D_o_m_a_i_n is a DNS blacklist domain such as _e_x_a_m_p_l_e_._c_o_m that will be searched. The strings _a_n_y, _I_P_a_d_d_r, _I_P_a_d_d_r_/_x_x, or _I_P_a_d_d_r_L_O_-_I_P_a_d_d_r_H_I, specifies which IP addresses found in the DNS blacklist after apply- ing the optional IP address mask _I_P_m_a_s_k say that mail messages should be rejected or accepted with --BB _s_e_t_:_w_h_i_t_e. "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 _b_l_t_y_p_e as _n_a_m_e, _a_l_l_-_n_a_m_e_s, _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 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 _a_l_l_-_n_a_m_e_s. Use _n_a_m_e with DNS blacklists that use wildcards for speed but _a_l_l_-_n_a_m_e_s for other DNS name blacklists. Blacklist types of _I_P_v_4 and _I_P_v_6 require that the domain name in a URL sender ad- dress be resolved into an IPv4 or IPv6 address. The resolved ad- dress from the mail message is then written as a reversed string of decimal octets to check the DNS blacklist, as in _2_._0_._0_._1_2_7_._e_x_a_m_p_l_e_._c_o_m. A _d_o_m_a_i_n of "." and type of _n_a_m_e 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 --BB _s_e_t_:_g_r_o_u_p_=_X. All searching within a group of black- lists is stopped at the first positive result. Unlike dccproc(8), positive results are ignored by ddcccciiffdd after be- ing logged unless an _o_p_t_i_o_n _D_N_S_B_L_-_o_n or _o_p_t_i_o_n _D_N_S_B_L_x_-_o_n line ap- pears a _w_h_i_t_e_c_l_n_t file. --BB _s_e_t_:_n_o_-_c_l_i_e_n_t implies 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 implies 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_:_w_h_i_t_e says the DNS list is a whitelist of names or IP addresses. --BB _s_e_t_:_b_l_a_c_k restores the default. DNS whitelist usually also need --BB _s_e_t_:_n_o_-_m_a_i_l___h_o_s_t, --BB _s_e_t_:_n_o_-_U_R_L, --BB _s_e_t_:_n_o_-_M_X, --BB _s_e_t_:_n_o_-_N_S, and --BB _s_e_t_:_n_o_-_m_a_i_l___h_o_s_t. --BB _s_e_t_:_d_e_f_a_u_l_t_s is equivalent to all of --BB _s_e_t_:_b_l_a_c_k --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 following DNS blacklists specified with --BB _d_o_m_a_i_n[_._._.] to group 1, 2, 3, or 4. --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 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. --BB _s_e_t_:_r_e_j_-_m_s_g_=_"_r_e_j_e_c_t_i_o_n _m_e_s_s_a_g_e_" 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_e_s_s_a_g_e is null, the default is restored. The de- fault DNS blacklist rejection message is the first message set with --rr. --BB _s_e_t_:_m_a_x___h_e_l_p_e_r_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 Unless SMTP proxy mode is enabled with --oo, 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 _c_k_s_u_m_s return _X_-_D_C_C header and the checksums for the message. _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_-_o_f_f disable greylisting for this message. _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 has the same effect as running ddcccciiffdd with --aa _I_G_N_O_R_E. It suppresses the overall, one character line 'R' result. This can be use- ful when using ddcccciiffdd only for greylisting. _l_o_g ensure that this message is logged as if ddcccciiffdd were running with --tt --aallll,,00,, _r_c_v_d_-_n_e_x_t causes ddcccciiffdd to skip a Received: header looking for the client IP address and HELO value. Each additional _r_c_v_d_-_n_e_x_t option in- creases the number of Received: headers skipped. _M_X or _M_X_D_C_C in the global --ww _w_h_i_t_e_c_l_n_t 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 ad- dress])..." format. Non-standard Received headers commonly 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 cannot invoke a per-user _w_h_i_t_e_c_l_n_t 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). 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 re- sult. 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 of- fered 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 @prefix@ is the DCC home directory in which other files are found. @libexecdir@/start-dccifd or @libexecdir@/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 --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 _/_v_a_r_/_d_c_c_/_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 _/_v_a_r_/_d_c_c_/_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 RHYOLITE_VERSION. 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. March 22, 2024