Provided by: dcc-client_1.2.74-2_i386 bug

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
     nearest DCC server.  DCCIFD then adds an X-DCC SMTP header line to the
     message.  The MTA is told to reject the message if it is unsolicited
     bulk.

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

     MTA programs generally use a simple ASCII protocol to send a mail message
     including its SMTP envelope to the daemon.  Dccifd responds with an
     indication of whether the message is unsolicited bulk and an optional
     copy of the 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 interface 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
          processes 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
          appropriate for the IPv6 addresses used by the DCC.  IPmask/96
          differs from noIP because the former retains the IPv4 to IPv6
          mapping prefix.

     -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
          directory.

          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
          maintained.  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
          message’s checksums from being reported to the DCC server and the
          addition 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
          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.

          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
          corresponding log directory.  To ensure the privacy of mail, it may
          be good to make the directories readable only by owner and group,
          and to use a cron script that changes the owner of each file to
          match the grandparent addr directory.

          There can also be a 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
          containing 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
          unsolicited 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
          thresholds.

          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
          substitute 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
          directories 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
          message, "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
          positives to use on abuse mailboxes.  It is less effective than
          greylisting with dccm(8) or dccifd(8) but can be useful in
          situations 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
          specified 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.
          Positive 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
          blacklists.  -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
          blacklists.  -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
          controlled.  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
     directories 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
                                 message.  -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
                   character.
       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
            command 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
     message 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
                 message, at least one of whose checksums reached its -t
                 thresholds 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 envelope 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 disposition 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.