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<!-- Manpage converted by man2html 3.0.1 -->
<B><A HREF="dccifd.html">dccifd(8)</A></B> Distributed Checksum Clearinghouse <B><A HREF="dccifd.html">dccifd(8)</A></B>
</PRE>
<H2><A NAME="NAME">NAME</A></H2><PRE>
<B>dccifd</B> -- Distributed Checksum Clearinghouse Interface Daemon
</PRE>
<H2><A NAME="SYNOPSIS">SYNOPSIS</A></H2><PRE>
<B>dccifd</B> [<B>-VdbxANQ</B>] [<B>-G</B> <I>on</I> | <I>off</I> | <I>noIP</I> | <I>IPmask/xx</I>] [<B>-h</B> <I>homedir</I>] [<B>-I</B> <I>user</I>]
[<B>-p</B> <I>/sock</I> | <I>lhost,lport,rhost</I>] [<B>-o</B> <I>/sock</I> | <I>host,port</I>]
[<B>-D</B> <I>local-domain</I>] [<B>-m</B> <I>map</I>] [<B>-w</B> <I>whiteclnt</I>] [<B>-U</B> <I>userdirs</I>]
[<B>-a</B> <I>IGNORE</I> | <I>REJECT</I> | <I>DISCARD</I>] [<B>-t</B> <I>type,</I>[<I>log-thold,</I>]<I>rej-thold</I>]
[<B>-g</B> [<I>not-</I>]<I>type</I>] [<B>-S</B> <I>header</I>] [<B>-l</B> <I>logdir</I>] [<B>-R</B> <I>rundir</I>]
[<B>-r</B> <I>rejection-msg</I>] [<B>-T</B> <I>tmpdir</I>] [<B>-j</B> <I>maxjobs</I>]
[<B>-B</B> <I>dnsbl-option</I>] [<B>-L</B> <I>ltype,facility.level</I>]
</PRE>
<H2><A NAME="DESCRIPTION">DESCRIPTION</A></H2><PRE>
<B>dccifd</B> 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 <B>dccifd</B> which in turn reports related checksums to the near-
est DCC server and adds an <I>X-DCC</I> SMTP header line to the message. The
MTA is told to reject the message if it is unsolicited bulk.
<B>Dccifd</B> is similar to the DCC sendmail milter interface, <B><A HREF="dccm.html">dccm(8)</A></B> and the
DCC Procmail interface, <B><A HREF="dccproc.html">dccproc(8)</A></B>. <B>Dccifd</B> is more efficient than
<B><A HREF="dccproc.html">dccproc(8)</A></B> but not restricted to use with sendmail like <B><A HREF="dccm.html">dccm(8)</A></B>. 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. <B>Dccifd</B> responds with
an indication of whether the message is unsolicited bulk and an optional
copy of the message with an <I>X-DCC</I> header added. The ASCII protocol is
described below and in the <I>include/dccif.h</I> file in the DCC source. There
is a sample C interface routine in the <I>dcclib/dccif.c</I> file in the DCC
source and the <I>dcclib.a</I> library generated from the source. A <I>Perl</I> ver-
sion of the interface routine is in <I>dccifd/dccif.pl</I>. Test or demonstra-
tion programs in the style of <B><A HREF="dccproc.html">dccproc(8)</A></B> that use those interface rou-
tines are in <I>dccifd/dccif-test</I>.
A subset of ESMTP can be used instead of the ASCII protocol to connect
<B>dccifd</B> to postfix as a "Before-Queue Content Filter." See the <B>-o</B> flag.
Since the checksums of messages that are whitelisted locally by the <B>-w</B>
<I>whiteclnt</I> file are not reported to the DCC server, <B>dccifd</B> knows nothing
about the total recipient counts for their checksums and so cannot add
<I>X-DCC</I> header lines to such messages.
Enable the daemon and put its parameters in the <I>/var/lib/dcc/dcc</I><B>_</B><I>conf</I> file
and start the daemon with the <I>/usr/sbin/rcDCC</I> or
<I>/usr/sbin/start-dccifd</I> scripts.
The list of servers that <B>dccifd</B> contacts is in the memory mapped file <I>map</I>
shared by local DCC clients. The file is maintained with <B><A HREF="cdcc.html">cdcc(8)</A></B>.
<A NAME="OPTIONS"><B>OPTIONS</B></A>
The following options are available:
<A NAME="OPTION-V"><B>-V</B></A> displays the version of <B>dccifd</B>.
<A NAME="OPTION-d"><B>-d</B></A> enables debugging output from the DCC client software. Additional
<B>-d</B> options increase the number of messages. A single <B>-d</B> logs
aborted SMTP transactions including those from some "dictionary
attacks."
<A NAME="OPTION-b"><B>-b</B></A> causes the daemon to not detach itself from the controlling tty and
put itself into the background.
<A NAME="OPTION-x"><B>-x</B></A> 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, <B>dccifd</B> 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 <B>-x</B>, 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 NAME="OPTION-A"><B>-A</B></A> adds to existing X-DCC headers in the message instead of replacing
existing headers of the brand of the current server.
<A NAME="OPTION-N"><B>-N</B></A> neither adds, deletes, nor replaces existing X-DCC headers in the
message. Each message is logged, rejected, and otherwise handled
the same.
<A NAME="OPTION-Q"><B>-Q</B></A> only queries the DCC server about the checksums of messages instead
of reporting and querying. This is useful when <B>dccifd</B> 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 <I>MXDCC</I> lines in the global <I>whiteclnt</I> file for
your MX mail servers that use DCC than <B>-Q</B>.
<A NAME="OPTION-G"><B>-G</B></A> <I>on</I> | <I>off</I> | <I>noIP</I> | <I>IPmask/xx</I>
controls <I>greylisting</I>. At least one working greylist server must be
listed in the <I>map</I> file in the DCC home directory. If more than one
is named, they must "flood" or change checksums and they must use
the same <B>-G</B> parameters. See <B><A HREF="dccd.html">dccd(8)</A></B>. Usually all dccm or dccifd
DCC client processes use the same <B>-G</B> parameters.
<I>IPmask/xx</I> and <I>noIP</I> remove part or all of the IP address from the
greylist triple.
<A NAME="OPTION-h"><B>-h</B></A> <I>homedir</I>
overrides the default DCC home directory, <I>/var/lib/dcc</I>.
<A NAME="OPTION-I"><B>-I</B></A> <I>user</I>
specifies the UID and GID of the process.
<A NAME="OPTION-p"><B>-p</B></A> <I>/sock/name</I> | <I>lhost,lport,rhost</I>
overrides the default address at which programs contact <B>dccifd</B>. 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 <B>dccifd</B>. 127.0.0.1 is a common choices for <I>lhost</I>. The
string <I>@</I> specifies IN_ADDRANY or all local IP addresses. 127.0.0.1
is a common choice for <I>rhost</I>, but it can be a <I>xxx.xxx.xxx.xxx/mm</I>
CIDR block or a <I>xxx.xxx.xxx.xxx-yyy.yyy.yyy.yyy</I> range of IPv4 or
IPv6 addresses.
<A NAME="OPTION-o"><B>-o</B></A> <I>/sock</I> | <I>host,port</I>
enables SMTP proxy mode instead of the ASCII protocol and specifies
the output connection when <B>dccifd</B> acts as an SMTP proxy. It is the
address of the SMTP server for which <B>dccifd</B> acts as SMTP client.
When <I>/sock</I> is <I>/dev/null</I>, <B>dccifd</B> acts as if there were downstream
SMTP server that always answers "250 ok". The string <I>@</I> specifies
the same IP address as the incoming TCP connection.
The input to <B>dccifd</B> in SMTP proxy mode is specified with <B>--p</B>. For
example, <B>-p</B> <I>127.0.0.1,10025,127.0.0.1/32</I> <B>-o</B> <I>127.0.0.1,10026</I> could be
used to connect <B>dccifd</B> 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.
<A NAME="OPTION-m"><B>-m</B></A> <I>map</I>
specifies a name or path of the memory mapped parameter file instead
of the default <I>map</I> file in the DCC home directory. It should be
created with the <B><A HREF="cdcc.html">cdcc(8)</A></B> command.
<A NAME="OPTION-w"><B>-w</B></A> <I>whiteclnt</I>
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 <I>X-DCC</I>
header, and whose checksums should not be reported to the DCC
server.
If the pathname <I>whiteclnt</I> is not absolute, it is relative to the DCC
home directory.
The format of the <B>dccifd</B> whiteclnt file is the same as the <I>whitelist</I>
files used by <B><A HREF="dbclean.html">dbclean(8)</A></B> and the <I>whiteclnt</I> file used by <B><A HREF="dccproc.html">dccproc(8)</A></B>.
See <B><A HREF="dcc.html">dcc(8)</A></B> for a description of DCC white and blacklists. Because
the contents of the <I>whiteclnt</I> file are used frequently, a companion
file is automatically created and maintained. It has the same path-
name but with an added suffix of <I>.dccw</I> 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 <I>X-DCC</I> header line by <B>dccifd</B> A whitelist entry for a checksum also
prevents rejecting or discarding the message based on DCC recipient
counts as specified by <B>-a</B> and <B>-t</B>. Otherwise, one or more checksums
with blacklisting entries ("MANY") cause all of the message's check-
sums to be reported to the server with an addressee count of "MANY".
If the message has a single recipient, an <I>env</I><B>_</B><I>To</I> <I>whiteclnt</I> entry of
"OK" for the checksum of its recipient address acts like any other
<I>whiteclnt</I> 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 <I>whiteclnt</I> file,
<B>dccifd</B> 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.
<A NAME="OPTION-U"><B>-U</B></A> <I>userdirs</I>
enables per-user <I>whiteclnt</I> files and log directories. Each target
of a message can have a directory of log files named
<I>userdirs/addr/log</I> where <I>addr</I> is the local user or mailbox name com-
puted by the MTA. The name of each user's log directory must be
<I>log</I>. If it is not absolute, <I>userdirs</I> is relative to the DCC home
directory. The directory containing the log files must be named <I>log</I>
and it must be writable by the <B>dccifd</B> 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
<B>dccifd</B> process, but they have <I>group</I> and <I>other</I> read and write permis-
sions copied from the corresponding <I>log</I> directory. To ensure the
privacy of mail, it may be good to make the directories readable
only by <I>owner</I> and <I>group</I>, and to use a cron script that changes the
owner of each file to match the grandparent <I>addr</I> directory.
There can also be a per -user whitelist file named
<I>userdirs/addr/whiteclnt</I> for each address <I>addr.</I> Any checksum that is
not white- or blacklisted by an individual addressee's <I>whiteclnt</I>
file is checked in the main <B>-w -whiteclnt</B> file. A missing per-
addressee <I>whiteclnt</I> file is the same as an empty file. Relative
paths for files included in per-addressee files are resolved in the
DCC home directory. The <I>whiteclnt</I> files and the <I>addr</I> directories
containing them must be writable by the <B>dccifd</B> process.
<I>Option</I> lines in per-user whiteclnt files can be used to modify many
aspects of <B>dccifd</B> filtering, as described in the main dcc man page.
For example, an <I>option</I> <I>dcc-off</I> line turns off DCC filtering for
individual mailboxes.
<A NAME="OPTION-a"><B>-a</B></A> <I>IGNORE</I> | <I>REJECT</I> | <I>DISCARD</I>
specifies the action taken when <B>dccifd</B> is in proxy mode with <B>-o</B> and
DCC server counts or <B>-t</B> thresholds say that a message is unsolicited
and bulk. <I>IGNORE</I> causes the message to be unaffected except for
adding the <I>X-DCC</I> header line to the message. This turns off DCC
filtering.
Spam can also be <I>REJECT</I>ed or (when in proxy mode with <B>-o</B>) accepted
and silently <I>DISCARD</I>ed without being delivered to local mailboxes.
The default is <I>REJECT</I>.
Mail forwarded via IP addresses marked <I>MX</I> or <I>MXDCC</I> in the main
<I>whiteclnt</I> file is treated as if <B>-a</B> <I>DISCARD</I> were specified. This
prevents "bouncing" spam.
The effects of the <B>-w</B> <I>whiteclnt</I> are not affected by <B>-a</B>.
<A NAME="OPTION-t"><B>-t</B></A> <I>type,</I>[<I>log-thold,</I>]<I>rej-thold</I>
sets logging and "spam" thresholds for checksum <I>type</I>. The checksum
types are <I>IP</I>, <I>env</I><B>_</B><I>From</I>, <I>From</I>, <I>Message-ID</I>, <I>substitute</I>, <I>Received</I>,
<I>Body</I>, <I>Fuz1</I>, <I>Fuz2</I>, <I>rep-total</I>, and <I>rep</I>. The first six, <I>IP</I> through
<I>substitute</I>, have no effect except when a local DCC server configured
with <B>-K</B> is used. The <I>substitute</I> thresholds apply to the first sub-
stitute heading encountered in the mail message. The string <I>ALL</I>
sets thresholds for all types, but is unlikely to be useful except
for setting logging thresholds. The string <I>CMN</I> specifies the com-
monly used checksums <I>Body</I>, <I>Fuz1</I>, and <I>Fuz2</I>. <I>Rej-thold</I> and <I>log-thold</I>
must be numbers, the string <I>NEVER</I>, or the string <I>MANY</I> 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.
<I>Log-thold</I> 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.
<I>Rej-thold</I> 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 <I>rep</I> and <I>rep-total</I>. The DCC
Reputations of IP addresses that the DCC database says have sent
more than <I>rep-total,log-thold</I> are computed and messages from those
addresses are logged. Messages from IP addresses with DCC Reputa-
tions of at least the <I>rep,rej-thold</I> rejection threshold can be
rejected. The DCC Reputation of an IP address is the percentage of
its messages known to have been sent to at least 10 recipients. The
defaults are equivalent to <I>rep,never</I> and <I>rep-total,never,20</I>.
Bulk DCC Reputations do not reject mail unless enabled by an
<I>option</I> <I>DCC-rep-on</I> line in a <I>whiteclnt</I> 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 <I>ALL,NEVER</I>, so that nothing is discarded, rejected, or
logged. A common choice is <I>CMN,25,50</I> to reject or discard mail with
common bodies except as overridden by the whitelist of the DCC
server, the sendmail <I>${dcc</I><B>_</B><I>isspam}</I> and <I>${dcc</I><B>_</B><I>notspam}</I> macros, and
<B>-g</B>, and <B>-w</B>.
<A NAME="OPTION-g"><B>-g</B></A> [<I>not-</I>]<I>type</I>
indicates that whitelisted, <I>OK</I> or <I>OK2</I>, counts from the DCC server
for a type of checksum are to be believed. They should be ignored
if prefixed with <I>not-</I>. <I>Type</I> is one of the same set of strings as
for <B>-t</B>. Only <I>IP</I>, <I>env</I><B>_</B><I>From</I>, and <I>From</I> are likely choices. By default
all three are honored, and hence the need for <I>not-</I>.
<A NAME="OPTION-S"><B>-S</B></A> <I>hdr</I>
adds to the list of substitute or locally chosen headers that are
checked with the <B>-w</B> <I>whiteclnt</I> file and sent to the DCC server. The
checksum of the last header of type <I>hdr</I> found in the message is
checked. <I>Hdr</I> can be <I>HELO</I> to specify the SMTP envelope HELO value.
<I>Hdr</I> can also be <I>mail</I><B>_</B><I>host</I> to specify the host name from the
Mail_from value in the SMTP envelope. As many as six different sub-
stitute headers can be specified, but only the checksum of the first
of the six will be sent to the DCC server.
<A NAME="OPTION-l"><B>-l</B></A> <I>logdir</I>
specifies a directory in which files containing copies of messages
processed by <B>dccifd</B> are kept. They can be copied to per-user direc-
tories specified with <B>-U</B>. Information about other recipients of a
message is deleted from the per-user copies.
See the FILES section below concerning the contents of the files.
See also the <I>option</I> <I>log-subdirectory-{day,hour,minute}</I> lines in
<I>whiteclnt</I> files described in <B><A HREF="dcc.html">dcc(8)</A></B>.
The directory is relative to the DCC home directory if it is not
absolute
<A NAME="OPTION-R"><B>-R</B></A> <I>rundir</I>
specifies the "run" directory where the file containing the daemon's
process ID is stored. The default value is <I>/var/run/dcc</I>.
<A NAME="OPTION-T"><B>-T</B></A> <I>tmpdir</I>
changes the default directory for temporary files from the default.
The default is the directory specified with <B>-l</B> or the system default
if <B>-l</B> is not used. The system default is often <I>/tmp</I>.
<A NAME="OPTION-D"><B>-D</B></A> <I>local-domain</I>
specifies a host or domain name by which the system is known. There
can be several <B>-D</B> settings.
To find the per-user log directory and whitelist for each mail
recipient, <B>dccifd</B> 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
<B>-o</B> is used, and when the SMTP recipient address includes an <I>at</I> <I>sign</I>
(@) each mail address is checked against the list of <I>local-domain</I>s.
The part of the recipient address remaining after longest matching
<I>local-domain</I> (if any) is taken as the user name. The match is
anchored at the right or the end of the recipient address. It must
start at a period (.) or <I>at</I> <I>sign</I> (@) in the domain name part of the
address.
If <I>local-domain</I> starts with an asterisk (*) indicating a wildcard,
preceding sub-domain names are discarded to compute the user name.
Otherwise, the computed user name will include any unmatched sub-
domain names.
The default value of <I>local-domain</I> when there are no <B>-D</B> settings is
the host name of the system.
<A NAME="OPTION-r"><B>-r</B></A> <I>rejection-msg</I>
specifies the rejection message in <B>-o</B> proxy mode for unsolicited
bulk mail or for mail temporarily blocked by <I>greylisting</I> when <B>-G</B> is
specified. The first <B>-r</B> <I>rejection-msg</I> 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 <B>-r</B> <I>rejection-msg</I> replaces the
default SMTP rejection message "5.7.1 550 %ID bad reputation; see
http://commercial-dcc.rhyolite.com/cgi-bin/reps.cgi?tgt=%CIP" for
mail with bulk DCC Reputations. If <I>rejection-msg</I> is the zero-length
string, the <B>-r</B> setting is counted but the corresponding message is
not changed.
<I>Rejection-msg</I> can contain specific information about the mail mes-
sage. The following strings starting with % are replaced with the
corresponding values:
%ID message ID such as the unique part of log file name or
sendmail queue ID
%CIP SMTP client IP address
%BTYPE type of DNS blacklist hit, such as "SMTP client",
"mail_host", or "URL NS"
%BTGT IP address or name declared bad by DNS blacklist
%BPROBE domain name found in DNS blacklist such as
4.3.2.10.example.com
%BRESULT value of the %BPROBE domain name found in DNS black-
list
A common alternate for the bulk mail rejection message is "4.7.1 451
Access denied by DCC" to tell the sending mail system to continue
trying. Use a 4yz response with caution, because it is likely to
delay for days a delivery failure message for false positives. If
the rejection message does not start with an RFC 1893 status code
and RFC 2821 reply code, 5.7.1 and 550 or 4.2.1 and 452 are used.
See also <B>-B</B> <I>set:rej-msg=rejection-msg</I> to set the status message for
mail rejected by DNS blacklists.
<A NAME="OPTION-j"><B>-j</B></A> <I>maxjobs</I>
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 <B>dccifd</B> with <B>-d</B> and see the starting message in the system log
to see the limit.
<A NAME="OPTION-B"><B>-B</B></A> <I>dnsbl-option</I>
enables DNS blacklist checks of the SMTP client IP address, SMTP
envelope Mail_From sender domain name, and of host names in URLs in
the message body. Body URL blacklisting has too many false posi-
tives to use on abuse mailboxes. It is less effective than
greylisting with <B><A HREF="dccm.html">dccm(8)</A></B> or <B><A HREF="dccifd.html">dccifd(8)</A></B> but can be useful in situa-
tions where greylisting cannot be used.
<I>Dnsbl-option</I> is either one of the <B>-B</B> <I>set:option</I> forms or
<B>-B</B> <I>domain</I>[any[<I>,bltype</I>]]
<B>-B</B> <I>domain</I>[<I>,IPaddr</I>[<I>/xx</I>[<I>,bltype</I>]]]
<B>-B</B> <I>domain</I>[<I>,IPaddr</I>[<I>-IPaddrHI</I>[<I>,bltype</I>]]]
<I>Domain</I> is a DNS blacklist domain such as <I>example.com</I> that will be
searched. The string <I>any</I>, <I>IPaddr</I>, <I>IPaddr/xxx</I>, or <I>IPaddrLO-IPaddrHI</I>,
specifies which IP addresses found in the DNS blacklist say that
mail messages should be rejected "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 specified by <I>bltype</I> as
<I>name</I>, <I>all-names</I>, <I>IPv4</I>, or <I>IPv6</I>. Given an envelope sender domain
name or a domain name in a URL of spam.domain.org and a blacklist of
type <I>name</I>, spam.domain.org.example.com will be looked up. The names
spam.domain.org.example.com, domain.org.example.com, and org.exam-
ple.com will be looked up in blacklists of type <I>all-names</I>. Use
<I>names</I> with DNS blacklists that use wild cards for speed but
<I>all-names</I> for other DNS name blacklists. Blacklist types of <I>IPv4</I>
and <I>IPv6</I> require that the domain name in a URL sender address be
resolved into an IPv4 or IPv6 address. The resolved address from
the mail message is then written as a reversed string of decimal
octets to check the DNS blacklist, as in <I>2.0.0.127.example.com</I>.
More than one blacklist can be specified and blacklists can be
grouped with <B>-B</B> <I>set:group=X</I>. All searching within a group of black-
lists is stopped at the first positive result.
Positive results are ignored after being logged unless an
<I>option</I> <I>DNSBL-on</I> line appears in the global or per-user <I>whiteclnt</I>
file.
<B>-B</B> <I>set:no-client</I>
implies that SMTP client IP addresses and reverse DNS domain
names should not be checked in the following blacklists.
<B>-B</B> <I>set:client</I> restores the default for the following black-
lists.
<B>-B</B> <I>set:no-mail</I><B>_</B><I>host</I>
implies that SMTP envelope Mail_From sender domain names should
not be checked in the following blacklists. <B>-B</B> <I>set:mail</I><B>_</B><I>host</I>
restores the default.
<B>-B</B> <I>set:no-URL</I>
says that URLs in the message body should not be checked in the
in the following blacklists. <B>-B</B> <I>set:URL</I> restores the default.
<B>-B</B> <I>set:no-MX</I>
says MX servers of sender Mail_From domain names and host names
in URLs should not be checked in the following blacklists.
<B>-B</B> <I>set:MX</I> restores the default.
<B>-B</B> <I>set:no-NS</I>
says DNS servers of sender Mail_From domain names and host
names in URLs should not be checked in the following black-
lists. <B>-B</B> <I>set:NS</I> restores the default.
<B>-B</B> <I>set:defaults</I>
is equivalent to all of <B>-B</B> <I>set:client</I>
<B>-B</B> <I>set:mail</I><B>_</B><I>host</I> <B>-B</B> <I>set:URL</I> <B>-B</B> <I>set:MX</I> and <B>-B</B> <I>set:NS</I>
<B>-B</B> <I>set:group=X</I>
adds following DNS blacklists specified with
<B>-B</B> <I>domain</I>[<I>,IPaddr</I>[<I>/xx</I>[<I>,bltype</I>]]]
to group 1, 2, or 3.
<B>-B</B> <I>set:debug=X</I>
sets the DNS blacklist logging level
<B>-B</B> <I>set:msg-secs=S</I>
limits <B>dccifd</B> to <I>S</I> seconds total for checking all DNS black-
lists. The default is 25.
<B>-B</B> <I>set:URL-secs=S</I>
limits <B>dccifd</B> to at most <I>S</I> seconds resolving and checking any
single URL. The default is 11. Some spam contains dozens of
URLs and some "spamvertised" URLs contain host names that need
minutes to resolve. Busy mail systems cannot afford to spend
minutes checking each incoming mail message.
<B>-B</B> <I>set:rej-msg=rejection-msg</I>
sets the SMTP rejection message for the following blacklists.
<I>Rejection-msg</I> must be in the same format as for <B>-r</B>. If
<I>rejection-msg</I> is null, the default is restored. The default
DNS blacklist rejection message is the first message set with
<B>-r</B>.
<B>-B</B> <I>set:maxjobs=X</I>
sets maximum number of helper processes to <I>X</I>. In order to use
typical single-threaded DNS resolver libraries, <B>dccifd</B> 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 <B>-j</B>.
<B>-B</B> <I>set:progpath=/usr/sbin/dns-helper</I>
changes the path to the helper program.
<A NAME="OPTION-L"><B>-L</B></A> <I>ltype,facility.level</I>
specifies how messages should be logged. <I>Ltype</I> must be <I>error</I>, <I>info</I>,
or <I>off</I> to indicate which of the two types of messages are being con-
trolled or to turn off all <B>syslog(3)</B> messages from <B>dccifd</B>. <I>Level</I>
must be a <B>syslog(3)</B> level among <I>EMERG</I>, <I>ALERT</I>, <I>CRIT</I>, <I>ERR</I>, <I>WARNING</I>,
<I>NOTICE</I>, <I>INFO</I>, and <I>DEBUG</I>. <I>Facility</I> must be among <I>AUTH</I>, <I>AUTHPRIV</I>,
<I>CRON</I>, <I>DAEMON</I>, <I>FTP</I>, <I>KERN</I>, <I>LPR</I>, <I>MAIL</I>, <I>NEWS</I>, <I>USER</I>, <I>UUCP</I>, and <I>LOCAL0</I>
through <I>LOCAL7</I>. The default is equivalent to
<B>-L</B> <I>info,MAIL.NOTICE</I> <B>-L</B> <I>error,MAIL.ERR</I>
<B>dccifd</B> 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.
<A NAME="Protocol"><B>Protocol</B></A>
<B>Dccifd</B> 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 <B>-o</B>. 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 <B>-o</B> depends on a
list of local domain names specified with <B>-D</B> to find per-user log direc-
tories and whitelist files. If neither XFORWARD nor XCLIENT are used,
<B>dccifd</B> 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
<B>dccifd</B>. Each ends with a newline ('\n') character.
options zero or more blank-separated strings among:
<I>spam</I> the message is already known to be spam
<I>body</I> return all of the headers with the added
<I>X-DCC</I> header line and the body
<I>header</I> return the <I>X-DCC</I> header
<I>query</I> ask the DCC server about the message without
reporting it, as if <B>dccifd</B> were running with
<B>-Q</B>.
<I>grey-query</I> only query the greylist server for this mes-
sage. <B>-G</B> <I>on</I> must be in use.
<I>no-reject</I> suppress the overall, one character line 'R'
result. This can be useful when using <B>dccifd</B>
only for greylisting.
<I>log</I> ensure that this message is logged as if
<B>dccifd</B> were running with <B>-t -all,0,</B>
client IP address of the SMTP client in a "dotted" or "coloned"
ASCII string and reverse-DNS host name. If the host name
is present, it must follow a carriage return character
('\r') after the IP address. The client IP address must be
present and non-null if the host name is present. The
string "0.0.0.0\n" is understood the same as the null
string, meaning that both the IP address and host name are
absent. If the client IP address is absent, then the IP
address and host name are taken from the first non-local
Received header if it has the standard "name (name [IP
address])..." format. Non-standard Received headers com-
monly added by qmail as well as Received headers specifying
IP addresses marked <I>MX</I> or <I>MXDCC</I> in the global <B>-w</B> <I>whiteclnt</I>
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 <I>Mail</I> <I>From</I> 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 <I>Rcpt</I> <I>To</I> 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 <I>spam</I> option is
not included, then the <I>query</I> is assumed. Mailboxes without
user names will lack per-user log files and will not invoke
a per-user whitelist.
The last recipient-user name pair is followed by an empty line and the
headers and body of the message. The end of the body of the mail message
is signaled by the MTA half-closing the connection. See <B>shutdown(2)</B>.
<B>Dccifd</B> responds with three things. First is a one character line of the
overall result advising the MTA:
A accept the message for all recipients and answer the SMTP DATA
command with a 2yz result.
G answer with a 4yz result to embargo the message for greylisting.
R reject the message and answer the DATA command with a 5yz result.
S accept the message for some recipients and so answer the DATA com-
mand with a 2yz result.
T temporary failure by the DCC system and so answer with a 4yz
result.
Second is a line of characters indicating the disposition of the message
for each corresponding recipient:
A deliver the message
G discard the message during a greylist embargo
R discard the message as spam
The SMTP protocol allows only a single result for the DATA command for
all recipients that were not rejected before body of the message was
offered with the DATA command. To accept the message for some recipients
and reject it for others, the MTA must tell the SMTP client it is accept-
ing the message for all recipients and then discard it for those that
would reject it.
Finally, if the <I>body</I> or <I>header</I> strings are in the first line of <I>options</I>
sent by the MTA to the daemon, then the <I>X-DCC</I> header line or the entire
body with the <I>X-DCC</I> header line follows.
</PRE>
<H2><A NAME="FILES">FILES</A></H2><PRE>
<A NAME="FILE-/var/lib/dcc">/var/lib/dcc</A> is the DCC home directory in which other files are found.
<A NAME="FILE-/usr/sbin/start">/usr/sbin/start</A>-dccifd
and
<A NAME="FILE-/usr/sbin/rcDCC">/usr/sbin/rcDCC</A>
are scripts used to start the daemon.
<A NAME="FILE-/var/lib/dcc/dcc_conf">/var/lib/dcc/dcc_conf</A>
contains parameters used by the scripts to start DCC daemons
and cron jobs.
<A NAME="FILE-logdir">logdir</A> is an optional directory specified with <B>-l</B> and containing
marked mail. Each file in the directory contains one mes-
sage, at least one of whose checksums reached its <B>-t</B> 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 <I>./configure</I> <I>--with-max-log-size=xx</I> 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 <B>-w</B> <I>whiteclnt</I> file. Each log file ends
with the <I>X-DCC</I> header line added to the message and the dis-
position of the message.
<A NAME="FILE-map">map</A> is the memory mapped file of information concerning DCC
servers in the DCC home directory.
<A NAME="FILE-whiteclnt">whiteclnt</A> contains the client whitelist in the format described in
<B><A HREF="dcc.html">dcc(8)</A></B>.
<A NAME="FILE-whiteclnt.dccw">whiteclnt.dccw</A>
is a memory mapped hash table of the <I>whiteclnt</I> file.
<A NAME="FILE-dccifd.pid">dccifd.pid</A> in the <B>-R</B> <I>rundir</I> directory contains daemon's process ID.
</PRE>
<H2><A NAME="EXAMPLES">EXAMPLES</A></H2><PRE>
Dccifd can be used as Postfix Before-Queue Content filter. In some tests
these values for <B>-p</B> and <B>-o</B> in <I>/var/lib/dcc/dcc</I><B>_</B><I>conf</I>.
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
</PRE>
<H2><A NAME="SEE-ALSO">SEE ALSO</A></H2><PRE>
<B><A HREF="cdcc.html">cdcc(8)</A></B>, <B><A HREF="dbclean.html">dbclean(8)</A></B>, <B><A HREF="dcc.html">dcc(8)</A></B>, <B><A HREF="dccd.html">dccd(8)</A></B>, <B><A HREF="dblist.html">dblist(8)</A></B>, <B><A HREF="dccm.html">dccm(8)</A></B>, <B><A HREF="dccproc.html">dccproc(8)</A></B>,
<B><A HREF="dccsight.html">dccsight(8)</A></B>,
</PRE>
<H2><A NAME="HISTORY">HISTORY</A></H2><PRE>
Implementation of <B>dccifd</B> Distributed Checksum Clearinghouses are based on
an idea of Paul Vixie with code designed and written at Rhyolite Software
starting in 2000. was started at Rhyolite Software in 2002. This docu-
ment describes version 1.3.113.
</PRE>
<H2><A NAME="BUGS">BUGS</A></H2><PRE>
<B>dccifd</B> uses <B>-t</B> where <B><A HREF="dccproc.html">dccproc(8)</A></B> uses <B>-c</B>.
By default <B>dccifd</B> look for its UNIX domain socket in the DCC home direc-
tory, but <B><A HREF="dccm.html">dccm(8)</A></B> looks in its <B>-R</B> <I>rundir</I>.
Systems without <B>setrlimit(2)</B> and <B>getrlimit(2)</B> RLIMIT_NOFILE can have
problems with the default limit on the number of simultaneous jobs, the
value of <B>-j</B>. 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 <B>-j</B> or to allow <B>dccifd</B> to open more
files.
July 20, 2009
</PRE>
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