dccifd(8) FreeBSD System Manager's Manual dccifd(8)
NAME
dccifd -- Distributed Checksum Clearinghouse Interface Daemon
SYNOPSIS
dccifd [-VdbxANPQ] [-G on | off | noIP | IPmask/xx] [-h homedir]
[-I user] [-p /sock | lhost,lport,rhost] [-o /sock | host,port]
[-D local-domain] [-m map] [-w whiteclnt] [-U userdirs]
[-a IGNORE | REJECT | DISCARD] [-t type,[log-thold,]rej-thold]
[-g [not-]type] [-S header] [-l logdir] [-R rundir]
[-r rejection-msg] [-T tmpdir] [-j maxjobs]
[-B dnsbl-option] [-L ltype,facility.level]
DESCRIPTION
dccifd is a daemon intended to connect spam filters such as SpamAssasin
and mail transfer agents (MTAs) other than sendmail to DCC servers. The
MTA or filter dccifd which in turn reports related checksums to the near-
est DCC server and 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(8) but not restricted to use with sendmail like dccm(8). All
three send reports of checksums related to mail received by DCC clients
and queries about the total number of reports of particular checksums.
MTA programs use a simple ASCII protocol a subset of SMTP to send a mail
message including its SMTP envelope to the daemon. 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 ASCII 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 ver-
sion of the interface routine is in dccifd/dccif.pl. Test or demonstra-
tion programs in the style of dccproc(8) that use those interface rou-
tines are in /var/dcc/build/dcc/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.
Enable the daemon and put its parameters in the /var/dcc/dcc_conf file
and start the daemon with the /var/dcc/libexec/rcDCC or
/var/dcc/libexec/start-dccifd scripts.
The list of servers that dccifd contacts is in the memory mapped file
/var/dcc/map shared by local DCC clients. The file is maintained with
cdcc(8).
OPTIONS
The following options are available:
-V displays the version of dccifd. Two or more -V options show the op-
tions with which it was built.
-d enables debugging output from the DCC client software. Additional
-d options increase the number of messages. A single -d logs
aborted SMTP transactions including those from some "dictionary at-
tacks."
-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 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 mail message is logged, rejected, and otherwise han-
dled the same.
-P The SpamAsassin DCC.pm plugin should watch for "bulk" in X-DCC SMTP
header fields, but historically has looked for counts of "many".
However, there are situations when dccifd knows that a mail message
is extremely bulky and probably spam. For example, mail from a
sender that is blacklisted in whiteclnt gets an X-DCC header that
includes bulk. To acommodate that bug in SpamAssassin, by default
whenever dccifd generates an X-DCC header containing "bulk", it also
forces the Body count to "many". -P turns off that kludge and the
Body contains the count from the DCC server.
-Q only queries the DCC server about the checksums of messages instead
of reporting. This is useful when dccifd 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 MXDCC lines in the global /var/dcc/whiteclnt
file for your MX mail servers that use DCC than to use -Q with
dccifd.
Do not use -Q except on mail that you know has been reported to a
DCC server. DCC depends on reports of all except known private mail
and works only because almost no DCC installations use -Q.
-G on | off | noIP | IPmask/xx
controls greylisting. At least one working greylist server must be
listed in the /var/dcc/map file. If more than one is named, they
must "flood" or change checksums and they must use the same -G pa-
rameters. See dccd(8). Usually all dccm or dccifd DCC client pro-
cesses use the same -G parameters.
IPmask/xx and noIP remove part or all of the IP address from the
greylist triple.
-h homedir
overrides the default DCC home directory, /var/dcc.
-I user
specifies the UID and GID of the process.
-p /sock/name | lhost,lport,rhost
overrides the default address at which programs contact dccifd. The
default is a UNIX domain socket named dccifd in the DCC home direc-
tory.
The second form specifies a local host name or IP address, a local
TCP port number, and the host name or IP addresses of computers that
can use dccifd. 127.0.0.1 is a common choices for lhost. The
string * for lhost specifies IN_ADDRANY or all local IP addresses.
127.0.0.1 is a common choice for rhost, but it can be a
xxx.xxx.xxx.xxx/mm CIDR block or a xxx.xxx.xxx.xxx-yyy.yyy.yyy.yyy
range of IPv4 or IPv6 addresses.
-o /sock | host,port
enables SMTP proxy mode instead of the ASCII protocol and specifies
the output connection when dccifd acts as an SMTP proxy. It is the
address of the SMTP server for which dccifd acts as SMTP client.
When /sock is /dev/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.
The input to dccifd in SMTP proxy mode is specified with -p. For
example, -p 127.0.0.1,10025,127.0.0.1/32 -o 127.0.0.1,10026 could be
used to connect dccifd 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.
-m map
specifies a name or path of the memory mapped parameter file instead
of the default /var/dcc/map. It should be created with the cdcc(8)
command.
-w whiteclnt
specifies an optional file containing filtering parameters as well
as SMTP client IP addresses, SMTP envelope values, and header values
of mail that is spam or is not spam and does not need a X-DCC
header, and whose checksums should not be reported to the DCC
server.
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
/var/dcc/whitelist files used by dbclean(8) and the whiteclnt file
used by dccproc(8). See dcc(8) for a description of DCC white and
blacklists. Because the contents of the whiteclnt file are used
frequently, a companion file is automatically created and main-
tained. It has the same pathname but with an added suffix of .dccw
and contains a memory mapped hash table of the main file.
A whitelist entry ("OK") or two or more semi-whitelistings ("OK2")
for one of the message's checksums prevents all of the message's
checksums from being reported to the DCC server and the addition of
a X-DCC header line by dccifd. A whitelist entry for a checksum
also prevents rejecting or discarding the message based on DCC re-
cipient counts as specified by -a and -t. Otherwise, one or more
checksums with blacklisting entries ("MANY") cause all of the mes-
sage's checksums to be reported to the server with an addressee
count of "MANY".
If the message has a single recipient, an env_To 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 sev-
eral 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 users who don't want filtering.
-U userdirs
enables per-user whiteclnt files and log directories. 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 com-
puted 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 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 permis-
sions 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 per-user whitelist file named
userdirs/addr/whiteclnt for each addressee addr. Any checksum that
is not white- or blacklisted by an individual addressee's per-user
whiteclnt file is checked in the main /var/dcc/whiteclnt file. A
missing per-addressee whiteclnt file is the same as an empty file.
Relative paths for files included in per-addressee files are re-
solved in the DCC home directory. The whiteclnt files and the addr
directories containing them must be writable by the dccifd process.
Option lines in per-user whiteclnt files can be used to modify many
aspects of dccifd filtering, as described in the main dcc man page.
For example, an option dcc-off line turns off DCC filtering for in-
dividual mailboxes.
-a IGNORE | REJECT | DISCARD
specifies the action taken when dccifd is in proxy mode with -o and
DCC server counts or -t thresholds say that a message is unsolicited
and bulk. IGNORE causes the message to be unaffected except for
adding the X-DCC header line to the message. This turns off all
filtering except greylisting.
Spam can also be REJECTed or when in proxy mode with -o accepted and
silently DISCARDed without being delivered to local mailboxes. The
default is REJECT.
Mail forwarded via IP addresses marked MX or MXDCC in the main
/var/dcc/whiteclnt file is treated as if -a DISCARD were specified.
This prevents "bouncing" spam.
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, substitute, Received,
Body, Fuz1, Fuz2, rep-total, and rep. The first six, IP through
substitute, have no effect except when a local DCC server configured
with -K is used. The substitute thresholds apply to the first sub-
stitute heading encountered in the mail message. The string ALL
sets thresholds for all types, but is unlikely to be useful except
for setting logging thresholds. The string CMN specifies the com-
monly 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 or discarded if not whitelisted.
DCC Reputation thresholds in the commercial version of DCC are con-
trolled by thresholds on checksum types rep and rep-total. The DCC
Reputations of IP addresses that the DCC database says have sent
more than rep-total,log-thold are computed and messages from those
addresses are logged. Messages from IP addresses with DCC Reputa-
tions of at least the rep,rej-thold rejection threshold can be re-
jected. The DCC Reputation of an IP address is the percentage of
its messages known to have been sent to at least 10 recipients. The
defaults are equivalent to rep,never and rep-total,never,20.
Bulk DCC Reputations do not reject mail unless enabled by an
option DCC-rep-on line a whiteclnt 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 ALL,NEVER, so that nothing is discarded, rejected, or
logged. A common choice is CMN,25,50 to reject or discard mail with
common bodies except as overridden by the whitelist of the DCC
server, the sendmail ${dcc_isspam} and ${dcc_notspam} macros, and
-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 8 different sub-
stitute headers can be specified, but only the checksum of the first
will be sent to the DCC server.
-l logdir
specifies a directory in which files containing copies of messages
processed by dccifd are kept. They can be copied to per-user direc-
tories specified with -U. Information about other recipients of a
message is deleted from the per-user copies.
If logdir is in the form D?dir, log files are put into subdirecto-
ries of dir the form dir/JJJ where JJJ is the current julian day.
H?dir puts logs files into subdirectories of the form dir/JJJ/HH
where HH is the current hour. M?dir puts log files into subdirecto-
ries of the form dir/JJJ/HH/MM where MM is the current minute.
The directory is relative to the DCC home directory if it is not ab-
solute
Option log-subdirectory-{day,hour,minute} lines in whiteclnt files
described in dcc(8) are an equivalent mechanism for per-user log di-
rectories. Also see the FILES section below concerning the contents
of log files.
-R rundir
specifies the "run" directory where the file containing the daemon's
process ID is stored. The default value is /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 -l is not used. The system default is often /tmp.
-D local-domain
specifies a host or domain 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 re-
cipient, dccifd 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
-o is used, and when the SMTP recipient address includes an at sign
(@) each mail address is checked against the list of local-domains.
The part of the recipient address remaining after longest matching
local-domain (if any) is taken as the user name. The match is an-
chored at the right or the end of the recipient address. It must
start at a period (.) or at sign (@) in the domain name part of the
address.
If local-domain starts with an asterisk (*) indicating a wildcard,
preceding sub-domain names are discarded to compute the user name.
Otherwise, the computed user name will include any unmatched sub-do-
main names.
The default value of local-domain when there are no -D settings is
the host name of the system.
-r rejection-msg
specifies the rejection message in -o proxy mode for unsolicited
bulk mail or for mail temporarily blocked by greylisting when -G is
specified. The first -r rejection-msg 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 -r rejection-msg replaces the de-
fault SMTP rejection message "5.7.1 550 %ID bulk mail reputation;
see https://commercial-dcc.rhyolite.com/cgi-bin/reps.cgi?tgt=%CIP"
for mail with bulk DCC Reputations. If rejection-msg is the zero-
length string, the -r setting is counted but the corresponding de-
fault message is not changed.
Rejection-msg 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 set:rej-msg to set the status message for mail rejected
by DNS blacklists.
-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 system limits on open files, select() bit masks, and so forth.
Start dccifd with -d and see the starting message in the system log
to see the limit.
-B dnsbl-option
enables DNS white- and blacklist checks of the SMTP client IP ad-
dress, SMTP envelope Mail_From sender domain name, and of host names
in URLs in the message body. Body URL blacklisting has too many
false positives to use on abuse mailboxes. It is less effective
than greylisting with dccm(8) or dccifd(8) but can be useful in sit-
uations where greylisting cannot be used. It can be combined with
greylisting.
Dnsbl-option is either one of the -B set:option forms or
-B domain[any[,bltype]]
-B domain[,IPaddr[/xx[&IPmask][,bltype]]]
-B domain[,IPaddrLO[-IPaddrHI[&IPmask][,bltype]]]
Domain is a DNS blacklist domain such as example.com that will be
searched. The strings any, IPaddr, IPaddr/xx, or IPaddrLO-IPaddrHI,
specifies which IP addresses found in the DNS blacklist after apply-
ing the optional IP address mask IPmask say that mail messages
should be rejected or accepted with -B set:white. "127.0.0.2" is
assumed if no address(es) are specified. IPv6 addresses can be
specified with the usual colon (:) notation. Host names can be used
instead of numeric addresses. The type of DNS blacklist is speci-
fied by bltype as name, all-names, 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 looked
up. The names spam.domain.org.example.com, domain.org.example.com,
and org.example.com will be looked up in blacklists of type
all-names. Use name with DNS blacklists that use wildcards for
speed but all-names for other DNS name blacklists. Blacklist types
of IPv4 and IPv6 require that the domain name in a URL sender ad-
dress be resolved into an IPv4 or IPv6 address. The resolved ad-
dress from the mail message is then written as a reversed string of
decimal octets to check the DNS blacklist, as in
2.0.0.127.example.com.
A domain of "." and type of name can be used to blacklist domain
names with specified addresses. This can be useful to detect URLs
with domain names listed in a Response Policy Zone (RPZ). For exam-
ple, the following can be used to reject mail containing URLs listed
by a response policy zone that maps evil domain names to 224.0.0.0
with an informative status message:
'-Bset:rej-msg=5.7.1 550 %ID %BTYPE \
https://example.com/query/dbl?domain=%BTGT'
-B.,224.0.0.0,name
More than one blacklist can be specified and blacklists can be
grouped with -B set:group=X. All searching within a group of black-
lists is stopped at the first positive result.
Unlike dccproc(8), positive results are ignored by dccifd after be-
ing logged unless an option DNSBL-on or option DNSBLx-on line ap-
pears a whiteclnt file.
-B set:no-client
implies that SMTP client IP addresses and reverse DNS domain
names should not be checked in the following blacklists.
-B set:client restores the default for the following black-
lists.
-B set:no-mail_host
implies that SMTP envelope Mail_From sender domain names should
not be checked in the following blacklists. -B set:mail_host
restores the default.
-B set:no-URL
says that URLs in the message body should not be checked in the
in the following blacklists. -B set:URL restores the default.
-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.
-B set:no-NS
says DNS servers of sender Mail_From domain names and host
names in URLs should not be checked in the following black-
lists. -B set:NS restores the default.
-B set:white
says the DNS list is a whitelist of names or IP addresses.
-B set:black restores the default. DNS whitelist usually also
need -B set:no-mail_host, -B set:no-URL, -B set:no-MX,
-B set:no-NS, and -B set:no-mail_host.
-B set:defaults
is equivalent to all of -B set:black -B set:client
-B set:mail_host -B set:URL -B set:MX and -B set:NS
-B set:group=X
adds following DNS blacklists specified with -B domain[...] to
group 1, 2, 3, or 4.
-B set:debug=X
sets the DNS blacklist logging level
-B set:msg-secs=S
limits dccifd to S seconds total for checking all DNS black-
lists. The default is 25.
-B set:URL-secs=S
limits dccifd to at most S seconds resolving and checking any
single URL or IP address. The default is 11. Some spam con-
tains dozens of URLs and some "spamvertised" URLs contain host
names that need minutes to resolve. Busy mail systems cannot
afford to spend minutes checking each incoming mail message.
-B set:rej-msg="rejection message"
sets the SMTP rejection message for the following blacklists.
Rejection-msg must be in the same format as for -r. If
rejection message is null, the default is restored. The de-
fault DNS blacklist rejection message is the first message set
with -r.
-B set:max_helpers=X
sets maximum number of helper processes to X. In order to use
typical single-threaded DNS resolver libraries, dccifd 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 -j.
-B set:progpath=/var/dcc/libexec/dns-helper
changes the path to the helper program.
-L ltype,facility.level
specifies how messages should be logged. Ltype must be error, info,
or off to indicate which of the two types of messages are being con-
trolled or to turn off all syslog(3) messages from dccifd. 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 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.
Protocol
Unless SMTP proxy mode is enabled with -o, Dccifd uses a simple ASCII
protocol to receive mail messages to be checked and to return results.
For each message, the MTA must open a connection to the interface daemon,
send options, envelope recipients, and the message, receive the results,
and close the connection.
Instead of the ASCII protocol, a subset of ESMTP is enabled by -o. Only
the familiar HELO, EHLO, Mail, Rcpt, DATA, RSET, and QUIT commands and
the Postfix extensions XFORWARD and XCLIENT are honored. Since SMTP has
no provisions for user names, the protocol enabled by -o depends on a
list of local domain names specified with -D to find per-user log direc-
tories and whitelist files. If neither XFORWARD nor XCLIENT are used,
dccifd uses the IP address of the MTA and the value of the HELO command.
In the ASCII protocol, each of the following lines are sent in order to
dccifd. Each ends with a newline ('\n') character.
options zero or more blank-separated strings among:
spam the message is already known to be spam
body return all of the headers with the added
X-DCC header line and the body
header return the X-DCC header
cksums return X-DCC header and the checksums for the
message.
query ask the DCC server about the message without
reporting it, as if dccifd were running with
-Q.
grey-off disable greylisting for this message.
grey-query only query the greylist server for this mes-
sage. -G on must be in use.
no-reject has the same effect as running dccifd with
-a IGNORE. It suppresses the overall, one
character line 'R' result. This can be use-
ful when using dccifd only for greylisting.
log ensure that this message is logged as if
dccifd were running with -t -all,0,
rcvd-next causes dccifd to skip a Received: header
looking for the client IP address and HELO
value. Each additional rcvd-next option in-
creases the number of Received: headers
skipped. MX or MXDCC in the global
-w whiteclnt file usually work better.
client IP address of the SMTP client in a "dotted" or "coloned"
ASCII string and reverse-DNS host name. If the host name
is present, it must follow a carriage return character
('\r') after the IP address. The client IP address must be
present and non-null if the host name is present. The
string "0.0.0.0\n" is understood the same as the null
string, meaning that both the IP address and host name are
absent. If the client IP address is absent, then the IP
address and host name are taken from the first non-local
Received header if it has the standard "name (name [IP ad-
dress])..." format. Non-standard Received headers commonly
added by qmail as well as Received headers specifying IP
addresses marked MX or MXDCC in the global -w whiteclnt
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 Mail From 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 Rcpt To 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 spam option is
not included, then the query is assumed. Mailboxes without
user names will lack per-user log files and cannot invoke a
per-user whiteclnt file.
The last recipient-user name pair is followed by an empty line and the
headers and body of the message. The end of the body of the mail message
is signaled by the MTA half-closing the connection. See shutdown(2).
Dccifd responds with three things. First is a one character line of the
overall result advising the MTA:
A accept the message for all recipients and answer the SMTP DATA
command with a 2yz result.
G answer with a 4yz result to embargo the message for greylisting.
R reject the message and answer the DATA command with a 5yz result.
S accept the message for some recipients and so answer the DATA com-
mand with a 2yz result.
T temporary failure by the DCC system and so answer with a 4yz re-
sult.
Second is a line of characters indicating the disposition of the message
for each corresponding recipient:
A deliver the message
G discard the message during a greylist embargo
R discard the message as spam
The SMTP protocol allows only a single result for the DATA command for
all recipients that were not rejected before body of the message was of-
fered with the DATA command. To accept the message for some recipients
and reject it for others, the MTA must tell the SMTP client it is accept-
ing the message for all recipients and then discard it for those that
would reject it.
Finally, if the 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.
/var/dcc/libexec/start-dccifd
or
/var/dcc/libexec/rcDCC
are scripts used to start the daemon.
dcc_conf contains parameters used by the scripts to start DCC daemons
and cron jobs.
logdir is an optional directory specified with -l and containing
marked mail. Each file in the directory contains one mes-
sage, at least one of whose checksums reached its -t thresh-
olds or that is interesting for some other reason. Each file
starts with lines containing the date when the message was
received, the IP address of the SMTP client, and SMTP enve-
lope values. Those lines are followed by the body of the
SMTP message including its header as it was received. Only
approximately the first 32 KBytes of the body are recorded
unless modified by ./configure --with-max-log-size=xx The
checksums for the message follow the body. They are followed
by lines indicate that one of the checksums is white- or
blacklisted by the -w whiteclnt file. Each log file ends
with the X-DCC header line added to the message and the dis-
position of the message.
map is the memory mapped file of information concerning DCC
servers in the DCC home directory.
whiteclnt contains the client whitelist in the format described in
dcc(8).
whiteclnt.dccw
is a memory mapped hash table of the /var/dcc/whiteclnt file.
dccifd.pid in the -R rundir directory contains daemon's process ID.
EXAMPLES
Dccifd can be used as Postfix Before-Queue Content filter. In some tests
these values for -p and -o in /var/dcc/dcc_conf.
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
SEE ALSO
cdcc(8), dbclean(8), dcc(8), dccd(8), dblist(8), dccm(8), dccproc(8),
dccsight(8),
HISTORY
Implementation of dccifd Distributed Checksum Clearinghouses are based on
an idea of Paul Vixie with code designed and written at Rhyolite Software
starting in 2000. was started at Rhyolite Software in 2002. This docu-
ment describes version RHYOLITE_VERSION.
BUGS
dccifd uses -t where dccproc(8) uses -c.
By default dccifd look for its UNIX domain socket in the DCC home direc-
tory, but dccm(8) looks in its -R rundir.
Systems without setrlimit(2) and getrlimit(2) RLIMIT_NOFILE can have
problems with the default limit on the number of simultaneous jobs, the
value of -j. 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 -j or to allow dccifd to open more
files.
March 22, 2024
Man(1) output converted with man2html modified for DCC
$Date 2001/04/29 03:22:18 $
