dccifd.8

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

## NAME

         dccifd -- Distributed Checksum Clearinghouse Program Interface

## SYNOPSIS

         dccifd [-VdbxANQ] [-G on | off | noIP | IPmask/xx] [-h homedir]
                [-p /sock | host,port,rhost/bits] [-o /sock | host,port]
                [-D local-domain] [-r rejection-msg] [-m map] [-w whiteclnt]
                [-U userdirs] [-a IGNORE|REJECT] [-t type,[log-thold,]rej-thold]
                [-g [not-]type] [-S header] [-l logdir] [-R rundir] [-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.  DCCIFD then adds an X-DCC SMTP header line to the mes-
         sage.  The MTA is told to reject the message if it is unsolicited bulk.

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

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

         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.

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

       OPTIONS
         The following options are available:

         -V   displays the version of the DCC program interface.

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

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

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

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

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

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

         -G on | off | noIP | IPmask/xx
              controls greylisting.  At least one working greylist server must be
              listed in the map file in the DCC home directory.  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 DCC client pro-
              cesses of dccm or dccifd should use the same -G parameters.

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

         -W   turns off DCC filtering by default to ease managing systems where
              only a minority of users want unsolicited bulk mail to be rejected.
              This is equivalent to a option dcc-off line in the main -w whiteclnt
              file.  When DCC filtering is off, the DCC server is queried and the
              X-DCC header is added but the message is marked to be delivered
              regardless of target counts and thresholds.

              DCC filtering is enabled for a mailbox when -W is not used and there
              is no option dcc-off line in the main or per-user whiteclnt file or
              there is a option dcc-on pine in the per-user whiteclnt file for the
              mailbox.  DCC filtering can also be enabled with an "OK2" entry for
              the fully qualified mailbox in the main or per-user whiteclnt file.

              Messages sent only to target addresses that are listed in the global
              or relevant per-user -w whiteclnt file with "OK" are not reported to
              the DCC server and so are not rejected and do not receive X-DCC
              headers.

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

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

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

         -o /sock | host,port
              enables SMTP proxy mode instead of the ASCII protocol and specifies
              the address of the SMTP server for which dccifd acts as SMTP client.
              When /sock is /var/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.

              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 map in the DCC home directory.  It should be created
              with the cdcc(8) command.

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

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

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

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

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

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

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

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

              Spam can also be REJECTed. The default is REJECT.

              With an action of REJECT, spam sent to both white-listed targets and
              non-white-listed targets is delivered to white-listed targets and if
              possible, silently discarded for non-white-listed targets.  This is
              not possible if there are too many non-white-listed targets to be
              saved in a buffer of about 500 bytes.

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

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

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

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

              The default is -t ALL,NEVER, so that nothing is rejected or logged.
              A common choice is -t CMN,25,50 to reject mail with common bodies
              except as overridden by the whitelist of the DCC server and local
              -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 6 different sub-
              stitute headers can be specified, but only the checksum of the first
              of the 6 will be sent to the DCC server.

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

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

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

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

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

         -D local-domain
              specifies a host 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 default
              ASCII protocol includes an optional user name with each recipient
              SMTP address.  When that user name is absent or when the subset of
              ESMTP enabled with -o is used, each mail address is checked against
              the list of -D local-domains.  If there is at least one match, the
              part of the recipient address remaining after matching the longest
              local-domain is taken as the user name.  The matching 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.

         -r rejection-msg
              specifies the rejection message for unsolicited bulk mail or for
              mail temporarily blocked by greylisting when -G is specified.  The
              first rejection-msg replaces the default bulk mail rejection mes-
              sage, "5.7.1 550 mail %s from %s rejected by DCC" The second
              replaces "4.2.1 452 mail %s from %s greylist temporary embargoed".
              There can be zero, one, or two "%s" strings.  The first is replaced
              an empty string and the second is replaced by the IP address of the
              SMTP client.

              A common alternate for the bulk mail rejection message is "4.7.1 451
              Access denied by DCC" to tell the sender 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 bulk mail
              rejection message does not start with a recognized error type and
              number, type 5.7.1 and 550 or 4.2.1 and 452 are used.

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

         -B dnsbl-option
              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 far too many false pos-
              itives 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.

              Dnsbl-option is either of the form set:option or of the form
              domain[,IPaddr[,bltype]].  Domain is a DNS blacklist domain such as
              example.com that will be searched.  IPaddr is the IP address in the
              DNS blacklist that indicates that the mail message is spam.
              127.0.0.1 is assumed if IPaddr 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 bltype as name, 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 tried.
              Blacklist types of IPv4 and IPv6 require that the domain name in a
              URL 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.  They are searched in
              order.  All searching is stopped at the first positive result.  Pos-
              itive results are ignored after being logged unless an option
              DNSBL-on line appears in the global or per-user whiteclnt file.

              -B set:debug sends more messages about all DNS resolutions to the
              system log.

              -B set:msg-secs=S limits dccifd to S seconds total for checking all
              DNS blacklists.  The default is 20.

              -B set:URL-secs=S limits dccifd to at most S seconds resolving and
              checking any single URL.  The default is 5.  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.  In order to use
              typical single-threaded DNS resolver libraries, dccm(8) and
              dccifd(8) use fleets of helper processes.

              -B set:no-envelope says that SMTP client IP addresses and sender
              Mail_From domain names should not be checked in the following black-
              lists.  -B set:envelope restores the default for subsequently named
              blacklists.

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

              -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 black-
              lists.  -B set:MX restores the default.

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

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

         dccifd normally sends counts of mail rejected and so forth 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
         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
                         query       ask the DCC server about the message without
                                     reporting it as if dccifd were running with
                                     -Q.
                         grey-query  only query the greylist server for this mes-
                                     sage.  -G on must be in use.
                         no-reject   suppress the overall, one character line 'R'
                                     result.  This can be useful when using dccifd
                                     only for greylisting.
           client      IP address of the SMTP client in a "dotted" or "coloned"
                       ASCII string and reverse-DNS host name.  If the host name
                       is present, it must follow a carriage return character
                       ('\r') after the IP address.  The client IP address must be
                       present and non-null if the host name is present.  If the
                       client IP address is absent, then the IP address and host
                       name are taken from the first Received header if it has the
                       standard "name (name [IP address])..." format.
           HELO        SMTP HELO value or nothing, followed by a newline charac-
                       ter.
           sender      or SMTP Mail From command value
           recipients  or SMTP Rcpt To values followed by corresponding local user
                       names, one pair to a line.  Each optional local user name
                       is separated from the corresponding recipient address by a
                       carriage return ('\r').  A local user name can be null if
                       it is not known.  Recipients that lack local user names
                       will lack per-user log files and will not invoke a per-user
                       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).

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

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

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

## FILES

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

## SEE ALSO

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

## HISTORY

         Implementation of dccifd was started at Rhyolite Software in 2002.  This
         describes version 1.2.74.

## BUGS

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

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

    FreeBSD 4.9                     March 20, 2005                     FreeBSD 4.9