.\" Copyright (c) 2005 by Rhyolite Software
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND RHYOLITE SOFTWARE DISCLAIMS ALL
.\" WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
.\" OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL RHYOLITE SOFTWARE
.\" BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES
.\" OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
.\" WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
.\" ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
.\" SOFTWARE.
.\"
.\" Rhyolite Software DCC 1.2.74-1.103 $Revision$
.\"
.Dd 2005/03/15 14:52:44
.ds volume-ds-DCC Distributed Checksum Clearinghouse
.Dt dccm 8 DCC
.Sh NAME
.Nm dccm
.Nd Distributed Checksum Clearinghouse Milter Interface
.Sh SYNOPSIS
.Bk -words
.Nm dccm
.Op Fl VdbxANQW
.Op Fl G Ar on | off | noIP | IPmask/xx
.Op Fl h Ar homedir
.br
.Op Fl p Ar protocol:filename | protocol:port@host
.Op Fl m Ar map
.br
.Op Fl w Ar whiteclnt
.Op Fl U Ar userdirs
.Op Fl a Ar IGNORE | REJECT | DISCARD
.br
.Oo
.Fl t Xo
.Sm off
.Ar type,
.Op Ar log-thold,
.Ar rej-thold
.Sm on
.Xc
.Oc
.Oo
.Fl g Xo
.Sm off
.Op Ar not-
.Ar type
.Sm on
.Xc
.Oc
.Op Fl S Ar header
.br
.Op Fl l Ar logdir
.Op Fl R Ar rundir
.Op Fl r Ar rejection-msg
.Op Fl j Ar maxjobs
.Op Fl B Ar dnsbl-option
.Op Fl L Ar ltype,facility.level
.Ek
.Sh DESCRIPTION
.Nm Dccm
is a daemon built with the sendmail milter interface intended to connect
sendmail to DCC servers.
When built with the milter filter machinery and configured to talk to
.Nm
in the
.Pa sendmail.cf
file,
sendmail passes all email to
.Nm
which in turn reports related checksums to the nearest DCC server.
.Nm Dccm
then adds an
.Em X-DCC
SMTP header line to the message.
Sendmail is told to reject the message if it is unsolicited bulk mail.
.Pp
.Nm
sends reports of checksums related to mail received by DCC clients
and queries about the total number of reports of particular checksums.
A DCC server receives
.Em no
mail, address, headers, or other information,
but only cryptographically secure checksums of such information.
A DCC server cannot determine the text or other information that corresponds
to the checksums it receives.
Its only acts as a clearinghouse of counts for checksums computed by clients.
For complete privacy as far as the DCC is concerned,
the checksums of purely internal mail or other
mail that is known to not be unsolicited bulk can be listed in a whitelist
to not be reported to the DCC server.
.Pp
Since the checksums of messages that are whitelisted locally
by the
.Fl w Ar whiteclnt
file are not reported to the DCC server,
.Nm
knows nothing about the total recipient counts for their checksums and
so cannot add
.Em X-DCC
header lines to such messages.
Sendmail does not tell
.Nm
about messages that are not received by sendmail via SMTP, including messages
submitted locally and received via UUCP, and so they also do not receive
.Em X-DCC
header lines.
.Pp
The list of servers that
.Nm
contacts is in a memory mapped file shared by local DCC clients.
The file is  maintained with
.Xr cdcc 8 .
Put parameters into the
.Pa dcc_conf
file and start the daemon with the
.Pa start-dccm
script.
.Pp
When sendmail is not used,
then
.Nm
is not useful.
.Xr dccproc 8
or
.Xr dccifd 8
can often be used instead.
.Ss OPTIONS
The following options are available:
.Bl -tag -width 3n
.It Fl V
displays the version of the DCC Milter interface.
.It Fl d
enables debugging output from the DCC client library.
Additional
.Fl d
options increase the number of messages.
A single
.Fl d
 aborted SMTP transactions including those from some "dictionary attacks."
.It Fl b
causes the daemon to not detach itself from the controlling tty
and put itself into the background.
.It Fl 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,
.Nm
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
.Fl x ,
unresponsive DCC servers cause
mail to be temporarily rejected with
.Em 4.7.1 451 DCC failure
.It Fl A
adds to existing X-DCC headers in the message
instead of replacing existing headers
of the brand of the current server.
.It Fl N
neither adds, deletes, nor replaces existing X-DCC headers in the message.
Each message is logged, rejected, and otherwise handled the same.
.It Fl Q
only queries the DCC server about the checksums of messages
instead of reporting and querying.
This is useful when
.Nm
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.
.It Fl G Ar on | off | noIP | IPmask/xx
controls
.Em greylisting .
At least one working greylist server must be listed in the
.Pa 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
.Fl G
parameters.
See
.Xr dccd 8 .
Usually all DCC client processes of dccm or dccifd should use the same
.Fl G
parameters.
.Pp
.Ar IPmask/xx
and
.Ar noIP
remove part or all of the IP address from the greylist triple.
The CIDR block size,
.Ar 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.
.Ar IPmask/96
differs from
.Ar noIP
because the former retains the IPv4 to IPv6 mapping prefix.
.It Fl W
turns off DCC filtering by default to ease managing systems where
only a minority of
users want unsolicited bulk mail to be rejected or discarded.
This is equivalent to a
.Ar option dcc-off
line in the main
.Fl w Ar whiteclnt
file.
When DCC filtering is off,
mail is handled as if
.Fl a Ar IGNORE
were in use.
The DCC server is queried and the
.Em X-DCC
header is added but the message is delivered regardless of
target counts and thresholds.
.Pp
DCC filtering is enabled for a mailbox when
.Fl W
is not used and there is no
.Ar option dcc-off
line
in the main
or per-user
.Ar whiteclnt
file or there is a
.Ar option dcc-on
pine in the per-user
.Ar 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
.Ar whiteclnt
file.
.Pp
Messages sent
.Em only
to target addresses that are listed in the global or relevant per-user
.Fl w Ar whiteclnt
file with "OK" are not reported to the DCC server
and so are not rejected or discarded and do not receive
.Em X-DCC
headers.
.It Fl h Ar homedir
overrides the default DCC home directory, which is often /var/dcc.
.It Fl p Ar protocol:filename | protocol:port@host
specifies the protocol and address by which sendmail will contact
.Nm dccm .
The default is a UNIX domain socket in the "run" directory, often
.Pa /var/run/dcc/dccm .
(See also
.Fl R)
This protocol and address must match the value in
.Pa sendmail.cf .
This mechanism can be used to connect
.Nm
on one computer to sendmail on another computer
when a port and host name or IP address are used.
.It Fl m Ar map
specifies a name or path of the memory mapped parameter file instead
of the default
.Pa map
file in the DCC home directory.
It should be created with the
.Xr cdcc 8
command.
.It Fl w Ar whiteclnt
specifies an optional file containing SMTP client IP addresses,
SMTP envelope values, and header values
of mail that is spam or is not spam and does not need a
.Em X-DCC
header,
and whose checksums should not be reported to the DCC server.
.Pp
If the pathname
.Ar whiteclnt
is not absolute, it is relative to the DCC home directory.
The format of the
.Nm
whiteclnt file is the same as the
.Pa whitelist
files used by
.Xr dbclean 8
and the
.Pa whiteclnt
file used by
.Xr dccproc 8 .
See
.Xr dcc 8
for a description of DCC white and blacklists.
Because the contents of the
.Ar whiteclnt
file are used frequently, a companion file is automatically
created and maintained.
It has the same pathname but with an added suffix of
.Ar .dccw
and contains a memory mapped hash table of the main file.
.Pp
A white-list entry ("OK") or two or more semi-white-listings ("OK2")
for the message's checksums prevents all of
the message's checksums from being reported to the DCC server 
and the addition of a
.Em X-DCC
header line by
.Nm dccm
(except for env_To checksums or when
.Fl W
is used).
A white-listing entry for a checksum
also prevents rejecting or discarding the message based on DCC recipient
counts as specified by
.Fl a
and
.Fl 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".
.Pp
White-list
.Ar env_To
values are handy for white-listing or exempting destination addresses
such as Postmaster from filtering
and for making "spam traps" of addresses that should never receive mail.
First an entry for the official envelope
.Ar Rcpt\ To
value is sought.
If that is not found,
.Nm
looks for an entry for the sendmail "user" string.
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.
.Pp
If the message has a single recipient, an
.Ar env_To
.Ar whiteclnt
entry of "OK" for the checksum of its recipient address acts like any other
.Ar 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
.Ar whiteclnt
file,
.Nm
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 white-listed) and delivering
the message to don't want filtering.
.Pp
Consider
.Fl W
or a
.Ar option dcc-off
line in whitelist files
to turn off DCC filtering.
.It Fl U Ar userdirs
enables private whitelist and log files.
Each target of a message can have a directory of log files named
.Ar usedirs/${dcc_userdir}/log
where
.Em ${dcc_userdir}
is the
.Pa sendmail.cf
macro described below.
If
.Em ${dcc_userdir}
is not set,
.Ar userdirs/${rcpt_mailer}/${rcpt_addr}/log
is used.
If it is not absolute,
.Ar userdirs
is relative to the DCC home directory.
The sub-directory prefixes for
.Fl l Ar logdir
are not honored.
The directory containing the log files must be named
.Ar log
and it must be writable by the
.Nm
process.
Each log directory must exist or logging for the corresponding
is silently disabled.
The files created in the log directory are owned by the UID of the
.Nm
process,
but they have
.Em group
and
.Em other
read and write permissions copied from the corresponding
.Ar log
directory.
To ensure the privacy of mail,
it may be good to make the directories readable only by
.Em owner
and
.Em group ,
and to use a
.Xr cron
script that changes the owner of each file to match the grandparent
.Ar addr
directory.
.Pp
There can also be
.Ar userdirs/${dcc_userdir}/whiteclnt ,
or if
.Ar ${dcc_userdir}
is not set,
.Ar userdirs/${rcpt_mailer}/${rcpt_addr}
per-user whitelist files.
The name of each file must be
.Ar whiteclnt .
Every checksum including the
.Em env_to
and sendmail "user"
values are looked for first in the userdirs/mailer/addr/whiteclnt
and list then in the global
.Fl w Ar whiteclnt
list.
A missing per-address
.Ar whiteclnt
file is the same as an empty file.
Relative paths for whitelists included in per-address whiteclnt
are resolved in the DCC home directory.
The
.Ar whiteclnt
files and the
.Ar addr
directories containing them must be writable by the
.Nm
process.
.Pp
The most likely value of
.Ar mailer
is
.Ar local .
Appropriate values for both
.Ar mailer
and
.Ar addr
can be seen by examining
.Em env_To
lines in
.Fl l Ar logdir
files.
.It Fl a Xo Ar IGNORE |
.Ar REJECT | DISCARD
.Xc
specifies the action taken when DCC server counts or
.Fl t
thresholds say that a message is unsolicited bulk.
.Ar IGNORE
causes the message to be unaffected except for adding the
.Em X-DCC
header line to the message.
This turns off DCC filtering.
.Pp
Spam can also be
.Ar REJECT Ns ed,
or accepted and silently
.Ar DISCARD Ns ed
without being delivered to local mailboxes.
The default is
.Ar REJECT .
.Pp
With an action of
.Ar REJECT
or
.Ar DISCARD ,
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.
.Pp
Determinations that mail is or is not spam from sendmail via
.Em ${dcc_isspam}
or
.Em ${dcc_notspam}
macros override
.Fl a .
The effects of the
.Fl w Ar whiteclnt
are also not affected by
.Fl a .
.It Fl t Xo
.Sm off
.Ar type,
.Op Ar log-thold,
.Ar rej-thold
.Sm on
.Xc
sets logging and "spam" thresholds for checksum
.Ar type .
The checksum types are
.Ar IP ,
.Ar env_From ,
.Ar From ,
.Ar Message-ID ,
.Ar Received ,
.Ar Body ,
.Ar Fuz1 ,
and
.Ar Fuz2 .
The string
.Ar ALL
sets thresholds for all types, but is unlikely to be useful except for
setting logging thresholds.
The string
.Ar CMN
specifies the commonly used checksums
.Ar Body ,
.Ar Fuz1 ,
and
.Ar Fuz2 .
.Ar Rej-thold
and
.Ar log-thold
must be numbers, the string
.Ar NEVER ,
or the string
.Ar 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.
.Pp
.Ar 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.
.Pp
.Ar Rej-thold
is the threshold at which messages are considered "bulk,"
and so should be rejected or discard if not white-listed.
Use
.Fl a Ar REJECT
or
.Fl a Ar Discard
to reject or discard bulk mail that is not white-listed.
Use
.Fl a Ar IGNORE to
only add X-DCC headers with the "bulk" string.
.Pp
The checksums of locally white-listed messages are not checked with
the DCC server and so only the number of targets of the current instance of
a white-listed message are compared against the thresholds.
.Pp
The default is
.Fl t Ar ALL,NEVER ,
so that nothing is discarded or logged.
A common choice is
.Fl t Ar CMN,25,50
to reject or discard
mail with common bodies except as overridden by
the whitelist of the DCC server, the sendmail
.Em ${dcc_isspam}
and
.Em ${dcc_notspam}
macros, and
.Fl g ,
and
.Fl w .
.It Fl g Xo
.Sm off
.Op Ar not-
.Ar type
.Sm on
.Xc
indicates that white-listed,
.Ar OK
or
.Ar OK2 ,
counts from the DCC server for a type of checksum are to be believed.
They should be ignored if prefixed with
.Ar not- .
.Ar Type
is one of the same set of strings as for
.Fl t .
Only
.Ar IP ,
.Ar env_From ,
and
.Ar From
are likely choices.
By default all three are honored,
and hence the need for
.Ar not- .
.It Fl S Ar hdr
adds to the list of substitute or locally chosen headers that
are checked with the
.Fl w Ar whiteclnt
file and sent to the DCC server.
The checksum of the last header of type
.Ar hdr
found in the message is checked.
.Ar Hdr
can be
.Em HELO
to specify the SMTP envelope HELO value.
.Ar Hdr
can also be
.Em mail_host
to specify the sendmail "resolved" host name from
the Mail_from value in the SMTP envelope.
.\"see DCC_MAX_SUB_CKS
As many as 6 different substitute headers can be specified, but only
the checksum of the first of the six will be sent to the DCC server.
.It Fl l Ar logdir
specifies a directory in which files containing copies of messages processed by
.Nm
are kept.
All messages logged are copied to the
.Fl l Ar logdir
directory.
They can also be copied to per-user directories specified with
.Fl U .
Information about other recipients of a message is deleted from
the per-user copies.
.Pp
If
.Ar logdir
starts with
.Em D? ,
log files are put into subdirectories of the form
.Ar logdir/JJJ
where
.Ar JJJ
is the current julian day.
.Ar H?logdir
puts logs files into subdirectories of the form
.Ar logdir/JJJ/HH
where
.Ar HH
is the current hour.
.Ar M?logdir
puts log files into subdirectories of the form
.Ar logdir/JJJ/HH/MM
where
.Ar MM
is the current minute.
See the FILES section below concerning the contents of the files.
.Pp
The directory is relative to the DCC home directory if it is not absolute
.It Fl R Ar 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.
.It Fl r Ar rejection-msg
specifies the rejection message for unsolicited bulk mail or
for mail temporarily blocked by
.Em greylisting
when
.Fl G
is specified.
The first
.Ar rejection-msg
replaces the default bulk mail rejection message,
.Bk -words
"5.7.1 550 mail %s from %s rejected by DCC".
.Ek
." see DCC_XCODE and DCC_RCODE in cmn.c
The second replaces
.Bk -words
"4.2.1 452 mail %s from %s greylist temporary embargoed".
.Ek
." see GREY_XCODE and GREY_RCODE in dccm.c
There can be zero, one, or two "%s" strings.
The first is replaced by the sendmail queue ID and the second is replaced by
the IP address of the SMTP client.
.Pp
A common alternate for the bulk mail rejection message is
.Bk -words
"4.7.1 451 Access denied by DCC"
.Ek
." see GREY_XCODE and GREY_RCODE in dccm.c
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.
." see DCC_XCODE DCC_RCODE GREY_XCODE GREY_RCODE in cmn.c
.It Fl j Ar maxjobs
limits the number of simultaneous requests from sendmail 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.
.\"
.\"
.\"
.\" syncronize changes in dccm, dccproc and dccifd man pages
.\"     it is too bad groff .so doesn't seem to work
.It Fl B Ar 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
.Xr dccm 8
or
.Xr dccifd 8
but can be useful in situations where
greylisting cannot be used.
.Pp
.Ar Dnsbl-option
is either of the form
.Ar set:option
or of the form
.Ar domain Ns Op Ar ,IPaddr Ns Op Ar ,bltype .
.Ar Domain
is a DNS blacklist domain such as example.com
that will be searched.
.Ar IPaddr
is the IP address in the DNS blacklist that indicates that the mail message
is spam.  127.0.0.1 is assumed if
.Ar 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
.Ar bltype
as
.Ar name ,
.Ar IPv4 ,
or
.Ar IPv6 .
Given an envelope sender domain name or a domain name in a URL of
spam.domain.org
and a blacklist of type
.Ar name ,
spam.domain.org.example.com will be tried.
Blacklist types of
.Ar IPv4
and
.Ar 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,
.Pp
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
.Ar option Ar DNSBL-on
line appears in the global or per-user
.Pa whiteclnt
file.
.Pp
.Fl B Ar set:debug
sends more messages about all DNS resolutions to the system log.
.Pp
.Fl B Ar set:msg-secs=S
limits
.Nm
to
.Ar S
seconds total for checking all DNS blacklists.
The default is 20.
.Pp
.Fl B Ar set:URL-secs=S
limits
.Nm
to at most
.Ar 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,
.Xr dccm 8
and
.Xr dccifd 8
use fleets of helper processes.
.Pp
.Fl B Ar set:no-envelope
says that SMTP client IP addresses and sender Mail_From domain names should
not be checked in the following blacklists.
.Fl B Ar set:envelope
restores the default for subsequently named blacklists.
.Pp
.Fl B Ar set:no-body
says that URLs in the message body should not be checked in the
in the following blacklists.
.Fl B Ar set:body
restores the default for later blacklists.
.Pp
.Fl B Ar 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.
.Fl B Ar set:MX
restores the default.
.\"
.\"
.\"
.It Fl L Ar ltype,facility.level
specifies how messages should be logged.
.Ar Ltype
must be
.Ar error
or
.Ar info
to indicate which of the two types of messages are being controlled.
.Ar Level
must be a
.Xr syslog 3
level among
.Ar EMERG , ALERT , CRIT , ERR ,
.Ar WARNING , NOTICE , INFO ,
and
.Ar DEBUG .
.Ar Facility
must be among
.Ar AUTH , AUTHPRIV , CRON , DAEMON ,
.Ar FTP , KERN , LPR , MAIL , NEWS ,
.Ar USER , UUCP ,
and
.Ar LOCAL0
through
.Ar LOCAL7 .
The default is equivalent to
.Pp
.Dl Fl L Ar info,MAIL.NOTICE Fl L Ar error,MAIL.ERR
.El
.Pp
.Nm
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.
They will be repeated every 24 hours instead of at midnight.
.Sh SENDMAIL MACROS
Sendmail can affect
.Nm
with the values of some
.Pa sendmail.cf
macros.
These macro names must be added to the
Milter.macros option statements in
.Pa sendmail.cf
as in the example "Feature" file dcc.m4.
.Bl -tag -width dcc_mail_host
.It Em ${dcc_isspam}
causes a mail message to be reported to the DCC server
as having been addressed to "MANY" recipients.
The
.Em ${dcc_isspam}
macro is ignored if the
.Em ${dcc_notspam}
macro is set to a non-null string
.Pp
If the value of the
.Ar ${dcc_isspam}
is null,
.Nm
uses SMTP rejection messages controlled by
.Fl a
and
.Fl r .
If the value of the
.Ar ${dcc_isspam}
macro starts with "DISCARD",
the mail message is silently discarded
as with
.Fl a Ar DISCARD.
This can be handy for keeping "spammers" from knowing they
are sending to "spam traps."
If value of the macro not null and does not start with "DISCARD",
it is used as the SMTP error
message given to the SMTP client trying to send the rejected message.
The message starts with an optional SMTP error type and number
followed by text.
.Pp
The
.Fl a
option does not effect messages
marked spam with
.Em ${dcc_isspam} .
When the
.Em ${dcc_isspam}
macro is set, the message is rejected or discarded despite
local or DCC database white-list entries.
The local white-list does control whether the message's
checksums will be reported to the DCC server and an
.Em X-DCC
SMTP header line will be added.
.It Em ${dcc_notspam}
causes a message not be considered unsolicited bulk despite
evidence to the contrary.
It also prevents
.Nm
from reporting the checksums of the message to the DCC server
and from adding an
.Em X-DCC
header line.
.Pp
When the macro is set by the
.Pa sendmail.cf
rules,
.Ar ${dcc_notspam}
macros overrides DCC threshlds that say the message should be
rejected as well as the effects of the
.Em ${dcc_isspam}
macro.
.It Em ${dcc_mail_host}
specifies the name of the SMTP client that is sending the message.
This macro is usually the same as the
.Em mail_host
macro.
They can differ when a sendmail "smart relay" is involved.
The
.Em ${dcc_mail_host}
macro does not work if
.Em FEATURE(delay_checks)
is used.
.It Em ${dcc_userdir}
is the per-user whitelist and log directory for a recipient.
If the macro is not set in sendmail.cf,
$&{rcpt_mailer}/$&{rcpt_addr}
is assumed,but with the recipient address converted to lower case.
Whatever value is used,
the directory name after the last slash (/) character is converted to
lower case.
Any value containing the string "/../" is ignored.
.Pp
This macro also does not work if
.Em FEATURE(delay_checks)
is used.
.Pp
The following two lines in a sendmail mc file have the same effect
as not defining the ${dcc_userdir} macro, provided
.Em FEATURE(dcc)
is also used and
the sendmail
.Pa cf/feature
directory has a symbolic link to the
.Pa misc/dcc.m4
file.
.El
.Bd -literal -compact
SLocal_check_rcpt
R$*	$: $1 $(macro {dcc_userdir} $@ $&{rcpt_mailer}/$&{rcpt_addr} $))
.Ed
.Sh FILES
.Bl -tag -width whiteclnt -compact
.It Pa /var/dcc
is the DCC home directory in which other files are found.
.It Pa libexec/start-dccm
is a script often used to the daemon.
.It Pa dcc/dcc_conf
contains parameters used by the scripts to start DCC daemons and cron jobs.
.It Pa logdir
is an optional directory specified with
.Fl l
and containing marked mail.
Each file in the directory contains one message, at least one of whose
checksums reached its
.Fl 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 by sendmail and without any new or changed header lines.
Only approximately the first 32 KBytes of the body are recorded
unless modified by
.Em ./configure --with-max-log-size=xx
The checksums for the message follow the body.
They are followed by lines indicating that the
.Em ${dcc_isspam}
or
.Em ${dcc_notspam}
.Pa sendmail.cf
macros were set or one of the checksums is white- or blacklisted by the
.Fl w Ar whiteclnt
file.
Each file ends with the
.Em X-DCC
header line added to the message and the disposition of
the message including SMTP status message if appropriate.
.It Pa map
is the memory mapped file of information concerning DCC servers
in the DCC home directory.
.It Pa whiteclnt
contains the client whitelist in
the format described in
.Xr dcc 8 .
.It Pa whiteclnt.dccw
is a memory mapped hash table of the
.Pa whiteclnt
file.
.It Pa dccm.pid
in the
.Fl R Ar rundir
directory contains daemon's process ID.
The string
.Dq dccm
is replaced by the file name containing the daemon to facilitate
running multiple daemons, probably connected to remote instances of
sendmail using TCP/IP instead of a UNIX domain socket.
See also
.Fl R .
.It Pa /var/run/dcc/dccm
is the default UNIX domain socket used by the sendmail milter interface.
See also
.Fl R .
.It Pa sendmail.cf
is the
.Xr sendmail 8
control file.
.It Pa misc/dcc.m4
sendmail mc file that should have a symbolic link in the sendmail
cf/feature directory so that
.Em FEATURE(dcc)
can be used in a sendmail mc file.
.El
.Sh EXAMPLES
.Nm Dccm
should be started before sendmail with something like the
script libexec/start-dccm.
It looks for common DCC parameters in the
.Pa dcc_conf
file in the DCC home directory.
.Pp
Those numbers should modified to fit local conditions.
It might be wise to replace the "100" numbers with much larger
values or with "MANY" until a few weeks of monitoring the log directory
show that sources of mailing lists are in the server's whitelist file
(see
.Xr dccd 8 )
or the local
.Pa whiteclnt
file.
.Pp
It is usually necessary to regularly delete old log files
with a script like libexec/cron-dccd.
.Pp
Sendmail must be built with the milter interface, such as by creating a
.Pa devtools/Site/site.config.m4
or similar file containing something like the following lines:
.Bd -literal -offset indent
APPENDDEF(`conf_sendmail_ENVDEF', `-D_FFR_MILTER=1')
APPENDDEF(`conf_libmilter_ENVDEF', `-D_FFR_MILTER=1')
.Ed
.Pp
Appropriate lines invoking the milter interface must be added to
.Pa sendmail.cf.
It should be sufficient to copy
the dcc.m4 file to the sendmail 8.11 cf/feature directory
and add the line
.Pp
.Dl FEATURE(dcc)
.Pp
to the local .mc file.
.Sh SEE ALSO
.Xr cdcc 8 ,
.Xr dbclean 8 ,
.Xr dcc 8 ,
.Xr dccd 8 ,
.Xr dblist 8 ,
.Xr dccifd 8 ,
.Xr dccproc 8 ,
.Xr dccsight 8 ,
.Xr sendmail 8 .
.Sh HISTORY
Implementation of
.Nm
was started at Rhyolite Software in 2000.
This describes version 1.2.74.
.Sh BUGS
.Nm
uses
.Fl t
where
.Xr dccproc 8
uses
.Fl c .
.Pp
On many systems with sendmail 8.11.3 and preceding,
a bug in the sendmail milter mechanism causes
.Nm
to die with a core file when given a signal.
.\"  LocalWords:  DCC whiteclnt whitelist setrlimit getrlimit dccproc dccm
.\"  LocalWords:  greylist