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| author | Peter Gervai <grin@grin.hu> |
|---|---|
| date | Tue, 10 Mar 2009 14:31:24 +0100 |
| parents | c7f6b056b673 |
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"> <HTML> <HEAD> <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1"> <TITLE>dccm.0.8</TITLE> <META http-equiv="Content-Style-Type" content="text/css"> <STYLE type="text/css"> BODY {background-color:white; color:black} ADDRESS {font-size:smaller} IMG.logo {width:6em; vertical-align:middle} </STYLE> </HEAD> <BODY> <PRE> <!-- Manpage converted by man2html 3.0.1 --> <B><A HREF="dccm.html">dccm(8)</A></B> Distributed Checksum Clearinghouse <B><A HREF="dccm.html">dccm(8)</A></B> </PRE> <H2><A NAME="NAME">NAME</A></H2><PRE> <B>dccm</B> -- Distributed Checksum Clearinghouse Milter Interface </PRE> <H2><A NAME="SYNOPSIS">SYNOPSIS</A></H2><PRE> <B>dccm</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>protocol:filename</I> | <I>protocol:port@host</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>-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>dccm</B> is a daemon built with the sendmail milter interface intended to connect <B>sendmail(8)</B> to DCC servers. When built with the milter filter machinery and configured to talk to <B>dccm</B> in the <I>sendmail.cf</I> file, send- mail passes all email to <B>dccm</B> which in turn reports related checksums to the nearest DCC server. <B>dccm</B> then adds an <I>X-DCC</I> SMTP header line to the message. Sendmail is told to reject the message if it is unsolicited bulk mail. <B>Dccm</B> 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 <I>no</I> 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. 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>dccm</B> knows nothing about the total recipient counts for their checksums and so cannot add <I>X-DCC</I> header lines to such messages. Sendmail does not tell <B>dccm</B> 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 <I>X-DCC</I> header lines. Enable the daemon and put its parameters in the <I>dcc</I><B>_</B><I>conf</I> file and start the daemon with the <I>@libexecdir@/start-dccm</I> or <I>var/dcc/libexec/rcDCC</I> script. The list of servers that <B>dccm</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>dccm</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> 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>dccm</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>dccm</B> is used to fil- ter 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. The CIDR block size, <I>xx</I>, must be between 1 and 128. 96 is added to block sizes smaller than 33 to make them appro- priate for the IPv6 addresses used by the DCC. <I>IPmask/96</I> differs from <I>noIP</I> for IPv4 addresses, because the former retains the IPv4 to IPv6 mapping prefix. <A NAME="OPTION-h"><B>-h</B></A> <I>homedir</I> overrides the default DCC home directory, <I>@prefix@</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>protocol:filename</I> | <I>protocol:port@host</I> specifies the protocol and address by which sendmail will contact <B>dccm</B>. The default is a UNIX domain socket in the "run" directory, <I>@dcc_rundir@/dccm</I>. (See also <B>-R)</B> This protocol and address must match the value in <I>sendmail.cf</I>. This mechanism can be used to con- nect <B>dccm</B> on one computer to sendmail on another computer when a port and host name or IP address are used. <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>dccm</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>dccm</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>dccm</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>usedirs/${dcc</I><B>_</B><I>userdir}/log</I> where <I>${dcc</I><B>_</B><I>userdir}</I> is the <I>sendmail.cf</I> macro described below. If <I>${dcc</I><B>_</B><I>userdir}</I> is not set, <I>userdirs/${rcpt</I><B>_</B><I>mailer}/${rcpt</I><B>_</B><I>addr}/log</I> is used. The most likely value of <I>mailer</I> is <I>local</I>. Appropriate values for both <I>${rcpt</I><B>_</B><I>mailer}</I> and <I>${rcpt</I><B>_</B><I>addr}</I> can be seen by examining <I>env</I><B>_</B><I>To</I> lines in <B>-l</B> <I>logdir</I> files. If it is not absolute, <I>userdirs</I> is rela- tive to the DCC home directory. The directory containing the log files must be named <I>log</I> and it must be writable by the <B>dccm</B> process. Each log directory must exist or logging for the corresponding is silently disabled. The files created in the log directory are owned by the UID of the <B>dccm</B> process, but they have <I>group</I> and <I>other</I> read and write permissions copied from the corresponding <I>log</I> directory. To ensure the privacy of mail, it may be good to make the directo- ries readable only by <I>owner</I> and <I>group</I>, and to use a cron script that changes the owner of each file to match the grandparent <I>addr</I> direc- tory. There can also be a per -user whitelist file named <I>userdirs/${dcc</I><B>_</B><I>userdir}/whiteclnt</I> or if <I>${dcc</I><B>_</B><I>userdir}</I> is not set, <I>userdirs/${rcpt</I><B>_</B><I>mailer}/${rcpt</I><B>_</B><I>addr}</I> per-user whitelist files. Any checksum that is not white- or blacklisted by an individual addressee's <I>whiteclnt</I> file is checked in the main <B>-w -whiteclnt</B> file. A missing per-addressee <I>whiteclnt</I> file is the same as an empty file. Relative paths for files included in per-addressee files are resolved in the DCC home directory. The <I>whiteclnt</I> files and the <I>addr</I> directories containing them must be writable by the <B>dccm</B> process. <I>Option</I> lines in per-user whiteclnt files can be used to modify many aspects of <B>dccm</B> filtering, as described in the main dcc man page. For example, an <I>option</I> <I>dcc-off</I> line turns off DCC filtering for individual mailboxes. <A NAME="OPTION-a"><B>-a</B></A> <I>IGNORE</I> | <I>REJECT</I> | <I>DISCARD</I> specifies the action taken when DCC server counts or <B>-t</B> thresholds say that a message is unsolicited and bulk. <I>IGNORE</I> causes the mes- sage to be unaffected except for adding the <I>X-DCC</I> header line to the message. This turns off DCC filtering. Spam can also be <I>REJECT</I>ed or accepted and silently <I>DISCARD</I>ed without being delivered to local mailboxes. The default is <I>REJECT</I>. Mail forwarded via IP addresses marked <I>MX</I> or <I>MXDCC</I> in the main <I>whiteclnt</I> file is treated as if <B>-a</B> <I>DISCARD</I> were specified. This prevents "bouncing" spam. Determinations that mail is or is not spam from sendmail via <I>${dcc</I><B>_</B><I>isspam}</I> or <I>${dcc</I><B>_</B><I>notspam}</I> macros override <B>-a</B>. 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 the DCC are controlled by thresholds on checksum types <I>rep</I> and <I>rep-total</I>. Mes- sages from an IP address that the DCC database says has sent more than <B>-t</B> <I>rep-total,log-thold</I> messages are logged. A DCC Reputation is computed for messages received from IP addresses that have sent more than <B>-t</B> <I>rep-total,log-thold</I> messages. The DCC Reputation of an IP address is the percentage of its messages that have been detected as bulk or having at least 10 recipients. The defaults are equiva- lent to <B>-t</B> <I>rep,never</I> and <B>-t</B> <I>rep-total,never,20</I>. Bad 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 sendmail "resolved" host name from the Mail_from value in the SMTP envelope. As many as six different substitute 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>dccm</B> are kept. They can be copied to per-user directo- ries 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 UNIX domain socket and file containing the daemon's process ID are stored. The default value is @dcc_rundir@ . <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 bad 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>dccm</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>[<I>,IPaddr</I>[<I>/xx</I>[<I>,bltype</I>]]] <I>Domain</I> is a DNS blacklist domain such as example.com that will be searched. <I>IPaddr</I>[<I>/xxx</I>] is the string "any" an IP address in the DNS blacklist that indicates that the mail message should be rejected, or a CIDR block covering results from the DNS blacklist. "127.0.0.2" is assumed if <I>IPaddr</I> is absent. IPv6 addresses can be specified with the usual colon (:) notation. Names can be used instead of numeric addresses. The type of DNS blacklist is speci- fied by <I>bltype</I> as <I>name</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 tried. 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 address is then written as a reversed string of decimal octets to check the DNS blacklist, as in 2.0.0.127.example.com, More than one blacklist can be specified and blacklists can be grouped. All searching within a group is stopped at the first posi- tive 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> says 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> says 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:no-temp-fail</I> <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 later 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>dccm</B> to <I>S</I> seconds total for checking all DNS blacklists. The default is 25. <B>-B</B> <I>set:URL-secs=S</I> limits <B>dccm</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 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. <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:temp-fail</I> causes <B>dccm</B> to the MTA to answer the SMTP DATA command with 452 4.2.1 mail %ID from %CIP temporary delayed for DNSBL if any DNS answer required for a DNSBL in the current group times out, including resolving names in URLs. <B>-B</B> <I>set:no-temp-fail</I> restores the default of assuming a negative answer for DNS responses that take too long. <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>dccm</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=@libexecdir@/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>dccm</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>dccm</B> normally sends counts of mail rejected and so forth the to 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. </PRE> <H2><A NAME="SENDMAIL-MACROS">SENDMAIL MACROS</A></H2><PRE> Sendmail can affect <B>dccm</B> with the values of some <I>sendmail.cf</I> macros. These macro names must be added to the Milter.macros option statements in <I>sendmail.cf</I> as in the example "Feature" file dcc.m4. <I>${dcc</I><B>_</B><I>isspam}</I> causes a mail message to be reported to the DCC server as having been addressed to "MANY" recipients. The <I>${dcc</I><B>_</B><I>isspam}</I> macro is ignored if the <I>${dcc</I><B>_</B><I>notspam}</I> macro is set to a non-null string If the value of the <I>${dcc</I><B>_</B><I>isspam}</I> is null, <B>dccm</B> uses SMTP rejection messages controlled by <B>-a</B> and <B>-r</B>. If the value of the <I>${dcc</I><B>_</B><I>isspam}</I> macro starts with "DISCARD", the mail message is silently discarded as with <B>-a</B> <I>DISCARD.</I> 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 fol- lowed by text. The <B>-a</B> option does not effect messages marked spam with <I>${dcc</I><B>_</B><I>isspam}</I>. When the <I>${dcc</I><B>_</B><I>isspam}</I> macro is set, the message is rejected or discarded despite local or DCC database whitelist entries. The local whitelist does con- trol whether the message's checksums will be reported to the DCC server and an <I>X-DCC</I> SMTP header line will be added. <I>${dcc</I><B>_</B><I>notspam}</I> causes a message not be considered unsolicited bulk despite evidence to the contrary. It also prevents <B>dccm</B> from reporting the checksums of the message to the DCC server and from adding an <I>X-DCC</I> header line. When the macro is set by the <I>sendmail.cf</I> rules, <I>${dcc</I><B>_</B><I>notspam}</I> macros overrides DCC threshlds that say the message should be rejected as well as the effects of the <I>${dcc</I><B>_</B><I>isspam}</I> macro. <I>${dcc</I><B>_</B><I>mail</I><B>_</B><I>host}</I> specifies the name of the SMTP client that is sending the message. This macro is usually the same as the <I>mail</I><B>_</B><I>host</I> macro. They can differ when a sendmail "smart relay" is involved. The <I>${dcc</I><B>_</B><I>mail</I><B>_</B><I>host}</I> macro does not work if <I>FEATURE(delay</I><B>_</B><I>checks)</I> is used. <I>${dcc</I><B>_</B><I>userdir}</I> is the per-user whitelist and log directory for a recipi- ent. 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 (/) char- acter is converted to lower case. Any value containing the string "/../" is ignored. This macro also does not work if <I>FEATURE(delay</I><B>_</B><I>checks)</I> is used. The following two lines in a sendmail mc file have the same effect as not defining the ${dcc_userdir} macro, pro- vided <I>FEATURE(dcc)</I> is also used and the sendmail <I>cf/feature</I> directory has a symbolic link to the <I>misc/dcc.m4</I> file. SLocal_check_rcpt R$* $: $1 $(macro {dcc_userdir} $@ $&{rcpt_mailer}/$&{rcpt_addr} $)) </PRE> <H2><A NAME="FILES">FILES</A></H2><PRE> <A NAME="FILE-@prefix@">@prefix@</A> is the DCC home directory in which other files are found. <A NAME="FILE-@libexecdir@/start">@libexecdir@/start</A>-dccm is a script used to <B>dccm</B>. <A NAME="FILE-dcc/dcc_conf">dcc/dcc_conf</A> contains parameters used by the scripts to start DCC daemons and cron jobs. <A NAME="FILE-logdir">logdir</A> is an optional directory specified with <B>-l</B> and containing marked mail. Each file in the directory contains one message, at least one of whose checksums reached its <B>-t</B> thresholds or that is interesting for some other reason. Each file starts with lines containing the date when the message was received, the IP address of the SMTP client, and SMTP envelope values. Those lines are followed by the body of the SMTP message including its header as it was received by sendmail and with- out any new or changed header lines. Only approximately the first 32 KBytes of the body are recorded unless modified by <I>./configure</I> <I>--with-max-log-size=xx</I> The checksums for the mes- sage follow the body. They are followed by lines indicating that the <I>${dcc</I><B>_</B><I>isspam}</I> or <I>${dcc</I><B>_</B><I>notspam}</I> <I>sendmail.cf</I> macros were set or one of the checksums is white- or blacklisted by the <B>-w</B> <I>whiteclnt</I> file. Each file ends with the <I>X-DCC</I> header line added to the message and the disposition of the message including SMTP status message if appropriate. <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-dccm.pid">dccm.pid</A> in the <B>-R</B> <I>rundir</I> directory contains daemon's process ID. The string ``dccm'' is replaced by the file name containing the daemon to facilitate running multiple daemons, probably con- nected to remote instances of sendmail using TCP/IP instead of a UNIX domain socket. See also <B>-R</B>. <A NAME="FILE-@dcc_rundir@/dccm">@dcc_rundir@/dccm</A> is the default UNIX domain socket used by the sendmail milter interface. See also <B>-R</B>. <A NAME="FILE-sendmail.cf">sendmail.cf</A> is the <B>sendmail(8)</B> control file. <A NAME="FILE-misc/dcc.m4">misc/dcc.m4</A> sendmail mc file that should have a symbolic link in the send- mail cf/feature directory so that <I>FEATURE(dcc)</I> can be used in a sendmail mc file. </PRE> <H2><A NAME="EXAMPLES">EXAMPLES</A></H2><PRE> <B>Dccm</B> should be started before sendmail with something like the script <I>@libexecdir@/start-dccm.</I> It looks for common DCC parameters in the <I>dcc</I><B>_</B><I>conf</I> file in the DCC home directory, <I>@prefix@.</I> 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 <B><A HREF="dccd.html">dccd(8)</A></B>) or the local <I>whiteclnt</I> file. It is usually necessary to regularly delete old log files with a script like @libexecdir@/cron-dccd. On systems unlike modern FreeBSD and other UNIX-like systems which include sendmail milter support, sendmail must be built with the milter interface, such as by creating a <I>devtools/Site/site.config.m4</I> or similar file containing something like the following lines: APPENDDEF(`conf_sendmail_ENVDEF', `-D_FFR_MILTER=1') APPENDDEF(`conf_libmilter_ENVDEF', `-D_FFR_MILTER=1') Appropriate lines invoking the milter interface must be added to <I>sendmail.cf.</I> That can be done by putting a symbolic link to the the misc/dcc.m4 file in the DCC source to the sendmail cf/feature directory and adding the line FEATURE(dcc) to the local .mc file. Note that <B>dccm</B> should not be used with the Postfix milter mechanism. Instead use <B><A HREF="dccifd.html">dccifd(8)</A></B> as a before-queue filter as described in that man page. </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="dccifd.html">dccifd(8)</A></B>, <B><A HREF="dccproc.html">dccproc(8)</A></B>, <B><A HREF="dccsight.html">dccsight(8)</A></B>, <B>sendmail(8)</B>. </PRE> <H2><A NAME="HISTORY">HISTORY</A></H2><PRE> Distributed Checksum Clearinghouses are based on an idea of Paul Vixie. Implementation of <B>dccm</B> was started at Rhyolite Software in 2000. This document describes version 1.3.103. </PRE> <H2><A NAME="BUGS">BUGS</A></H2><PRE> <B>dccm</B> uses <B>-t</B> where <B><A HREF="dccproc.html">dccproc(8)</A></B> uses <B>-c</B>. 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 dccm[24448]: DCC: accept() returned invalid socket A fix is to use a smaller value for <B>-j</B> or to allow <B>dccm</B> to open more files. Sendmail version 8.13 and later can be told to poll() instead of select with SM_CONF_POLL. Some older versions of sendmail knew about FFR_USE_POLL. One of the following lines in your devtools/Site/site.con- fig.m4 file can help: APPENDDEF(`conf_libmilter_ENVDEF', `-DSM_CONF_POLL') APPENDDEF(`conf_libmilter_ENVDEF', `-DFFR_USE_POLL') On many systems with sendmail 8.11.3 and preceding, a bug in the sendmail milter mechanism causes <B>dccm</B> to die with a core file when given a signal. February 26, 2009 </PRE> <HR> <ADDRESS> Man(1) output converted with <a href="http://www.oac.uci.edu/indiv/ehood/man2html.html">man2html</a> modified for the DCC $Date 2001/04/29 03:22:18 $ <BR> <A HREF="http://www.dcc-servers.net/dcc/"> <IMG SRC="http://logos.dcc-servers.net/border.png" class=logo ALT="DCC logo"> </A> <A HREF="http://validator.w3.org/check?uri=referer"> <IMG class=logo ALT="Valid HTML 4.01 Strict" SRC="http://www.w3.org/Icons/valid-html401"> </A> </ADDRESS> </BODY> </HTML>