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|
dccproc(8) Distributed Checksum Clearinghouse dccproc(8)
NNAAMMEE
ddccccpprroocc -- Distributed Checksum Clearinghouse Procmail Interface
SSYYNNOOPPSSIISS
ddccccpprroocc [--VVddAAQQCCHHEERR] [--hh _h_o_m_e_d_i_r] [--mm _m_a_p] [--ww _w_h_i_t_e_c_l_n_t] [--TT _t_m_p_d_i_r]
[--aa _I_P_-_a_d_d_r_e_s_s] [--ff _e_n_v___f_r_o_m] [--tt _t_a_r_g_e_t_s]
[--xx _e_x_i_t_c_o_d_e] [--cc _t_y_p_e_,[_l_o_g_-_t_h_o_l_d_,]_r_e_j_-_t_h_o_l_d] [--gg [_n_o_t_-]_t_y_p_e]
[--SS _h_e_a_d_e_r] [--ii _i_n_f_i_l_e] [--oo _o_u_t_f_i_l_e] [--ll _l_o_g_d_i_r]
[--BB _d_n_s_b_l_-_o_p_t_i_o_n] [--LL _l_t_y_p_e_,_f_a_c_i_l_i_t_y_._l_e_v_e_l]
DDEESSCCRRIIPPTTIIOONN
DDccccpprroocc copies a complete SMTP message from standard input or a file to
standard output or another file. As it copies the message, it computes
the DCC checksums for the message, reports them to a DCC server, and adds
a header line to the message. Another program such as procmail(1) can
use the added header line to filter mail. Dccproc does not support any
thresholds of its own, because equivalent effects can be achieved with
regular expressions and you can apply dccproc several times using differ-
ent DCC servers and then score mail based what all of the DCC servers
say.
Error messages are sent to stderr as well as the system log. Connect
stderr and stdout to the same file to see errors in context, but direct
stderr to /dev/null to keep DCC error messages out of the mail. The --ii
option can also be used to separate the error messages.
DDccccpprroocc 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 no mail, address, headers, or other
information, but only cryptographically secure checksums of such informa-
tion. A DCC server cannot determine the text or other information that
corresponds to the checksums it receives. It only acts as a clearing-
house of counts of checksums computed by clients.
For the sake of privacy for even the checksums of private mail, the
checksums of senders 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.
When sendmail(8) is used, dccm(8) is a better DCC interface. Dccifd(8)
is more efficient than ddccccpprroocc because it is a daemon, but that has costs
in complexity. See dccsight(8) for a way to use previously computed
checksums.
OOPPTTIIOONNSS
The following options are available:
--VV displays the version of the DCC procmail(1) interface.
--dd enables debugging output from the DCC client library. Additional --dd
options increase the number of messages. One causes error messages
to be sent to STDERR as well as the system log.
--AA adds to existing X-DCC headers (if any) of the brand of the current
server instead of replacing existing headers.
--QQ only queries the DCC server about the checksums of messages instead
of reporting and then querying. This is useful when ddccccpprroocc is used
to filter mail that has already been reported to a DCC server by
another DCC client such as dccm(8). 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, such as would happen
if ddccccpprroocc is not given --QQ when processing a stream of mail that has
already been seen by a DCC client. Additional reports of a message
increase its apparent "bulkness."
--CC outputs only the X-DCC header and the checksums for the message.
--HH outputs only the X-DCC header.
--EE adds lines to the start of the log file turned on with --ll and --cc
describing what might have been the envelope of the message. All of
the information for the envelope lines comes from arguments to
ddccccpprroocc including --aa and --RR. No lines are generated for which no
information is available, such as the envelope recipient.
--RR says the first Received line has a standard "name (name [IP
address])..." format and that the address is the IP address of the
SMTP client that would otherwise be provided with --aa. If the local
SMTP server adds a Received line with some other format or does not
add a Received line, the --aa option should be used.
--hh _h_o_m_e_d_i_r
overrides the default DCC home directory, which is often /var/dcc.
--mm _m_a_p
specifies a name or path of the memory mapped parameter file instead
of the default _m_a_p in the DCC home directory. It should be created
with the nneeww mmaapp operation of the cdcc(8) command.
--ww _w_h_i_t_e_c_l_n_t
specifies an optional file containing SMTP client IP addresses and
SMTP headers of mail that do not need X-DCC headers and whose check-
sums should not be reported to the DCC server. It can also contain
checksums of spam. If the pathname is not absolute, it is relative
to the DCC home directory. Thus, individual users with private
whitelists usually specify them with absolute paths. Common
whitelists shared by users must be in the DCC home directory or one
of its subdirectories and owned by the set-UID user of ddccccpprroocc. It
is useful to _i_n_c_l_u_d_e a common or system-wide whitelist in private
lists.
The format of the ddccccpprroocc whiteclnt file is the same as the
_w_h_i_t_e_l_i_s_t file required by dbclean(8) and dccm(8). Unlike dccm, the
ddccccpprroocc whitelist is optional. Unless --ww is used, ddccccpprroocc uses only
the whitelist in the DCC server, which is rarely sufficient.
Because the contents of the _w_h_i_t_e_c_l_n_t file are used frequently, a
companion file is automatically created and maintained. It has the
same pathname but with an added suffix of _._d_c_c_w. It contains a mem-
ory mapped hash table of the main file.
A local whitelist entry ("OK) or two or more semi-whitelistings
("OK2") for one of the message's checksums prevents all of the mes-
sage's checksums from being reported to the DCC server and the addi-
tion of a _X_-_D_C_C header line by ddccccpprroocc. Because it is run by or on
behalf of a single user, ddccccpprroocc ignores _e_n_v___T_o entries in the
_w_h_i_t_e_c_l_n_t file. Users who don't want to use ddccccpprroocc shouldn't.
--TT _t_m_p_d_i_r
changes the default directory for temporary files from the default.
The default is the directory specified with --ll or the system default
if there --ll is not used. The system default is often _/_t_m_p.
--aa _I_P_-_a_d_d_r_e_s_s
specifies the IP address (not the host name) of the immediately pre-
vious SMTP client. It is often not available. See also --RR.
--ff _e_n_v___f_r_o_m
specifies the RFC 821 envelope "Mail From" value with which the mes-
sage arrived. It is often not available. If --ff is not present, the
contents of the first Return-Path: or UNIX style From_ header is
used. The _e_n_v___f_r_o_m string is often but need not be bracketed with
"<>".
--tt _t_a_r_g_e_t_s
specifies the number of addressees of the message if other than 1.
The string _m_a_n_y instead of a number asserts that there were too many
addressees and that the message is unsolicited bulk email.
--xx _e_x_i_t_c_o_d_e
specifies the code or status with which ddccccpprroocc exits if the --cc
thresholds are reached or the --ww _w_h_i_t_e_c_l_n_t file blacklists the mes-
sage, unless the message is whitelisted.
The default value is EX_NOUSER. EX_NOUSER is 67 on many systems.
Use 0 to always exit successfully.
--cc _t_y_p_e_,[_l_o_g_-_t_h_o_l_d_,]_r_e_j_-_t_h_o_l_d
sets logging and "spam" thresholds for checksum _t_y_p_e. Each logged
message placed in a separate file in the directory specified with
--ll. The checksum types are _I_P, _e_n_v___F_r_o_m, _F_r_o_m, _M_e_s_s_a_g_e_-_I_D,
_R_e_c_e_i_v_e_d, _B_o_d_y, _F_u_z_1, and _F_u_z_2. The string _A_L_L sets thresholds for
all types, but is unlikely to be useful except for setting logging
thresholds. The string _C_M_N specifies the commonly used checksums
_B_o_d_y, _F_u_z_1, and _F_u_z_2. _R_e_j_-_t_h_o_l_d and _l_o_g_-_t_h_o_l_d must be numbers, the
string _N_E_V_E_R, or the string _M_A_N_Y 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.
_L_o_g_-_t_h_o_l_d 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. Messages that reach at least
one of their rejection thresholds or that have complicated combina-
tions of white- and blacklisting are logged regardless of logging
thresholds.
_R_e_j_-_t_h_o_l_d is the threshold at which messages are considered "bulk,"
and so should cause the X-DCC header line to contain the string
"bulk" and ddccccpprroocc to exit with the value set by --xx.
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 thresh-
olds.
The default is --cc _A_L_L_,_N_E_V_E_R, so that nothing is discarded or logged.
A common choice is --cc _C_M_N_,_2_5_,_5_0 to reject or discard mail with com-
mon bodies except as overridden by the whitelist of the DCC server
and --gg and --ww.
--gg [_n_o_t_-]_t_y_p_e
indicates that white-listed, _O_K or _O_K_2, counts from the DCC server
for a type of checksum are to be believed. They should be ignored
if prefixed with _n_o_t_-. _T_y_p_e is one of the same set of strings as
for --cc. Only _I_P, _e_n_v___F_r_o_m, and _F_r_o_m are likely choices. By default
all three are honored, and hence the need for _n_o_t_-.
--SS _h_d_r
adds to the list of substitute or locally chosen headers that are
checked with the --ww _w_h_i_t_e_c_l_n_t file and sent to the DCC server. The
checksum of the last header of type _h_d_r found in the message is
checked. As many as 6 different substitute headers can be speci-
fied, but only the checksum of the first of the 6 will be sent to
the DCC server.
--ii _i_n_f_i_l_e
specifies an input file for the entire message instead of standard
input. If not absolute, the pathname is interpreted relative to the
directory in which ddccccpprroocc was started.
--oo _o_u_t_f_i_l_e
specifies an output file for the entire message including headers
instead of standard output. If not absolute, the pathname is inter-
preted relative to the directory in which ddccccpprroocc was started.
--ll _l_o_g_d_i_r
specifies a directory for copies of messages whose checksum target
counts exceed --cc thresholds. The format of each file is affected by
--EE. If _l_o_g_d_i_r is not an absolute path, it is relative to the direc-
tory in which ddccccpprroocc is started. If _l_o_g_d_i_r starts with _D_?, log
files are put into subdirectories of the form _l_o_g_d_i_r_/_J_J_J where _J_J_J
is the current julian day. _H_?_l_o_g_d_i_r puts logs files into subdirec-
tories of the form _l_o_g_d_i_r_/_J_J_J_/_H_H where _H_H is the current hour.
_M_?_l_o_g_d_i_r puts log files into subdirectories of the form
_l_o_g_d_i_r_/_J_J_J_/_H_H_/_M_M where _M_M is the current minute. See the FILES sec-
tion below concerning the contents of the files.
The directory is relative to the DCC home directory if it is not
absolute
--BB _d_n_s_b_l_-_o_p_t_i_o_n
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 pos-
itives to use on abuse mailboxes. It is less effective than
greylisting with dccm(8) or dccifd(8) but can be useful in situa-
tions where greylisting cannot be used.
_D_n_s_b_l_-_o_p_t_i_o_n is either of the form _s_e_t_:_o_p_t_i_o_n or of the form
_d_o_m_a_i_n[_,_I_P_a_d_d_r[_,_b_l_t_y_p_e]]. _D_o_m_a_i_n is a DNS blacklist domain such as
example.com that will be searched. _I_P_a_d_d_r is the IP address in the
DNS blacklist that indicates that the mail message is spam.
127.0.0.1 is assumed if _I_P_a_d_d_r 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 _b_l_t_y_p_e as _n_a_m_e, _I_P_v_4, or _I_P_v_6. Given an envelope sender
domain name or a domain name in a URL of spam.domain.org and a
blacklist of type _n_a_m_e, spam.domain.org.example.com will be tried.
Blacklist types of _I_P_v_4 and _I_P_v_6 require that the domain name in a
URL be resolved into an IPv4 or IPv6 address. The address is then
written as a reversed string of decimal octets to check the DNS
blacklist, as in 2.0.0.127.example.com,
More than one blacklist can be specified. They are searched in
order. All searching is stopped at the first positive result. Pos-
itive results are ignored after being logged unless an _o_p_t_i_o_n
_D_N_S_B_L_-_o_n line appears in the global or per-user _w_h_i_t_e_c_l_n_t file.
--BB _s_e_t_:_d_e_b_u_g sends more messages about all DNS resolutions to the
system log.
--BB _s_e_t_:_m_s_g_-_s_e_c_s_=_S limits ddccccpprroocc to _S seconds total for checking all
DNS blacklists. The default is 20.
--BB _s_e_t_:_U_R_L_-_s_e_c_s_=_S limits ddccccpprroocc to at most _S seconds resolving and
checking any single URL. The default is 5. Some spam contains
dozens of URLs and that some "spamvertised" URLs contain host names
that need minutes to resolve. Busy mail systems cannot afford to
spend minutes checking each incoming mail message. In order to use
typical single-threaded DNS resolver libraries, dccm(8) and
dccifd(8) use fleets of helper processes.
--BB _s_e_t_:_n_o_-_e_n_v_e_l_o_p_e says that SMTP client IP addresses and sender
Mail_From domain names should not be checked in the following black-
lists. --BB _s_e_t_:_e_n_v_e_l_o_p_e restores the default for subsequently named
blacklists.
--BB _s_e_t_:_n_o_-_b_o_d_y says that URLs in the message body should not be
checked in the in the following blacklists. --BB _s_e_t_:_b_o_d_y restores
the default for later blacklists.
--BB _s_e_t_:_n_o_-_M_X says MX servers of sender Mail_From domain names and
host names in URLs should not be checked in the following black-
lists. --BB _s_e_t_:_M_X restores the default.
--LL _l_t_y_p_e_,_f_a_c_i_l_i_t_y_._l_e_v_e_l
specifies how messages should be logged. _L_t_y_p_e must be _e_r_r_o_r or
_i_n_f_o to indicate which of the two types of messages are being con-
trolled. _L_e_v_e_l must be a syslog(3) level among _E_M_E_R_G, _A_L_E_R_T, _C_R_I_T,
_E_R_R, _W_A_R_N_I_N_G, _N_O_T_I_C_E, _I_N_F_O, and _D_E_B_U_G. _F_a_c_i_l_i_t_y must be among _A_U_T_H,
_A_U_T_H_P_R_I_V, _C_R_O_N, _D_A_E_M_O_N, _F_T_P, _K_E_R_N, _L_P_R, _M_A_I_L, _N_E_W_S, _U_S_E_R, _U_U_C_P, and
_L_O_C_A_L_0 through _L_O_C_A_L_7. The default is equivalent to
--LL _i_n_f_o_,_M_A_I_L_._N_O_T_I_C_E --LL _e_r_r_o_r_,_M_A_I_L_._E_R_R
Something like this turns off the log messages:
--LL _n_o_t_i_c_e_,_M_A_I_L_._d_e_b_u_g --LL _e_r_r_o_r_,_M_A_I_L_._D_E_B_U_G
ddccccpprroocc exits 0 on success and with the --xx value if the --cc thresholds are
reached or the --ww _w_h_i_t_e_c_l_n_t file blacklists the message. If at all pos-
sible, the input mail message is output to standard output or the --oo
_o_u_t_f_i_l_e despite errors. If possible, error messages are put into the
system log instead of being mixed with the output mail message. The exit
status is zero for errors so that the mail message will not be rejected.
FFIILLEESS
/var/dcc DCC home directory in which other files are found.
map memory mapped file in the DCC home directory of information
concerning DCC servers.
whiteclnt contains the client whitelist in the format described in
dcc(8).
whiteclnt.dccw
is a memory mapped hash table corresponding to the _w_h_i_t_e_c_l_n_t
file.
tmpdir contains temporary files created and deleted as ddccccpprroocc pro-
cesses the message.
logdir is an optional directory specified with --ll and containing
marked mail. Each file in the directory contains one message,
at least one of whose checksums reached one of its --cc thresh-
olds. The entire body of the SMTP message including its
header is followed by the checksums for the message.
EEXXAAMMPPLLEESS
The following procmailrc(5) rule adds an X-DCC header to passing mail
:0 f
| /usr/local/bin/dccproc -ERw whiteclnt
This procmailrc(5) recipe rejects mail with total counts of 10 or larger
for the commonly used checksums:
:0 fW
| /usr/local/bin/dccproc -ERw whiteclnt -ccmn,10
:0 e
{
EXITCODE=67
:0
/dev/null
}
SSEEEE AALLSSOO
cdcc(8), dcc(8), dbclean(8), dccd(8), dblist(8), dccifd(8), dccm(8),
dccsight(8), mail(1), procmail(1).
HHIISSTTOORRYY
Implementation of ddccccpprroocc was started at Rhyolite Software in 2000. This
describes version 1.2.74.
BBUUGGSS
ddccccpprroocc uses --cc where dccm(8) uses --tt.
FreeBSD 4.9 March 20, 2005 FreeBSD 4.9
|
