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psyced/world/net/smtp/server.c

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2009-01-26 20:12:53 +00:00
// $Id: server.c,v 1.57 2008/05/24 07:23:00 lynx Exp $ // vim:syntax=lpc
/*
* rudimentary prototype of an SMTP server
* all your protocols belong to us
*/
#include <net.h>
#include <server.h>
#include <person.h>
// does mailto:*place@host work for addressing places?
// unfortunately # is not allowed in mailto: urls according to the NEW URI RFC
#define GROUP_PREFIX '*'
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#define PERSON_PREFIX '~'
// RFC 822 allows both * and ~ in usernames. phew.
#ifndef MAX_EMAIL_LINES
# ifdef _flag_optimize_protection_SMTP
# define MAX_EMAIL_LINES 5
# else
# define MAX_EMAIL_LINES 50
# endif
#endif
#ifndef MAX_EMAIL_SIZE
# ifdef _flag_optimize_protection_SMTP
# define MAX_EMAIL_SIZE 50 * 7
# else
# define MAX_EMAIL_SIZE 50 * 70
# endif
#endif
#ifndef _time_logon_delay_SMTP
# define _time_logon_delay_SMTP 20
#endif
// handle st00pid optional brackets
#define ADDRPARSE(XXX, USER, HOST) (\
sscanf(XXX, "<%s@%s>", USER, HOST) || \
sscanf(XXX, "%s@%s", USER, HOST) || \
sscanf(XXX, "<%s>", USER) || \
(USER = XXX) )
qScheme() { return "smtp"; }
volatile mapping vars;
volatile object target;
volatile string origin, text, header;
volatile int bodycount; // yeaaahhh!! bodycount's in the house!!
volatile mapping head2vars = ([
"subject": "_subject",
"content-type": "_type_content",
"message-id": "_ID_SMTP",
]);
#ifdef SMTP_ALIASES
volatile mapping smtp_aliases = ([
SMTP_ALIASES
]);
#endif
// the most important thing in an smtp daemon is.. the spam filter
//
// our current strategy is:
// reject mails with attachments.
// reject non-plain mails.
// reject mails that exceed MAX_EMAIL_LINES lines.
//
// leaves you with only the shortest V1AGRA candidates.
//
spam(mc, extra, message) {
P1(("%O spam(%O, %O..\n", ME, mc, extra))
write(message);
#if 0
monitor_report("_warning_abuse"+ mc,
S("%O rejecting %s mail from %O for %O.",
query_ip_number(), a, origin, vars["_nick_target"]));
#else
// seems to work generally, so lets reduce the
// reporting to a logfile..
log_file("SMTP_SPAM", "%s\t%s\t%s\t%s\t%O\n",
query_ip_number() || "(null)",
vars["_nick_target"] || "(null)",
mc, origin || "(null)", extra);
#endif
QUIT
}
parse(a) {
/*
* this is the parser for the command mode
*/
string cmd, fullargs;
string *args;
unless (sscanf(a, "%s%t%s", cmd, fullargs)) cmd = a;
if (fullargs) args = explode(fullargs, " ");
if (smtpcmd(cmd, args, fullargs, a))
next_input_to(#'parse);
}
#if !__EFUN_DEFINED__(trim)
# define trim(x) x
#endif
body(a) {
if (a != ".") {
if (++bodycount > MAX_EMAIL_LINES)
return spam("_illegal_length", vars["_subject"],
"254 Insufficient storage for long messages\n");
if (a != "") {
text += a + "\n";
if (strlen(text) > MAX_EMAIL_SIZE)
return spam("_illegal_size", vars["_subject"],
"254 Insufficient storage for long messages\n");
}
next_input_to(#'body);
return;
}
PT(("SMTP %O content %O vars %O\n", query_ip_number(), text, vars))
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unless (objectp(target)) {
// || (strlen(vars["_nick_target"]) &&
// (target = vars["_nick_target"][0] == GROUP_PREFIX
// ? find_place(vars["_nick_target"]) :
// summon_person(vars["_nick_target"])))) {
// ... and PERSON_PREFIX?
// re-summon may happen when a user logged out while the
// mail was coming in. unlikely. even unlikelier that it
// gets here:
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P0(("SMTP %O requires re-summon of username %O\n", query_ip_number(), user))
write("550 Technical problems summoning recipient\n");
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// let's observe this.. does it really happen?
// having summon logic twice in here is silly
} else {
string subject;
text = trim(chomp(text));
subject = trim(vars["_subject"] || "");
if (strlen(text) < 3 && strlen(subject) < 3) {
return spam("_illegal_content_empty", subject+text+a,
"254 What is this? An SMTP Presence Notification? Nice, we don't have that, yet. We have to invent it first!\n");
}
vars["_content"] = text;
vars["_subject"] = decode_embedded_charset(subject);
// more likely to have resolved by now
// even better to call async DNS here.. one day
vars["_host_source"] = query_ip_name();
write("250 accepted for delivery\n");
// certainly not the definitive mc, but at least person
// doesn't reply with a _message_echo_private which
// then goes out to spammers and godknowswho.. although
// in some cases that's sexy.
//
// uncool about this one: it doesn't get logged. but
// a _message wouldn't have the template. we need
// the mc reform!!
sendmsg(target, "_notice_email_delivered",
//"([_method_SMTP] from [_host_source] to [_nick_target]@[_host_target]) [_subject]\n[_content]\n",
// [_nick] wird erweitert um die source??!?
"([_method_SMTP] from [_nick] to [_nick_target]) [_subject]\n[_content]\n",
// "smtp:" for SOML-capable senders?
vars, "mailto:"+ origin);
// a log to get a clue if everything is working fine.
// sendmail keeps such logs too
log_file("SMTP_OK", "%s\t%s\t%s\t%s\n",
vars["_host_source"] || "(null)", vars["_nick_target"] || "(null)",
vars["_host_target"] || "(null)", origin || "(null)");
target = 0;
vars = ([]);
}
return next_input_to(#'parse);
}
headers(a) {
string t;
if (a == "") {
next_input_to(#'body);
bodycount = 0;
return;
}
next_input_to(#'headers);
unless (sscanf(a, "%s:%.0t%s", t, a)) {
// a continuation line..
if (header) {
if (vars[header]) vars[header] += a;
else {
// this cannot happen really
P0(("SMTP %O line cont for %O w/out start: %O\n",
query_ip_number(), header, a))
}
} else {
// skip! this is a continuation of a header that
// we have rejected according to head2vars!
// so we get here continously and there's nothing wrong
// with it!
}
return;
}
if (header = head2vars[lower_case(t)]) switch(header) {
case "_type_content":
unless (abbrev("text/plain", a))
return spam("_illegal_type_content", a,
"254 Insufficient storage for non-plain messages\n");
// we don't need to store this one
header = 0; // no line conts either
break;
// don't operate on headers yet as a line continuation may follow
// case "_subject":
// vars["_subject"] = decode_embedded_charset(a);
// break;
default:
vars[header] = a;
}
}
smtpcmd(cmd, args, all, asis) {
object o, palo;
string user, host, mail;
P2(("smtpcmd %s %O\n", cmd, args))
switch(cmd = upper_case(cmd)) {
case "RSET":
origin = 0;
target = 0;
case "NOOP":
write("250 SYS 64738\n");
break;
case "HELO":
case "EHLO":
if (sizeof(args) == 1) {
write("250 "+ SERVER_HOST +" Hello "
+ query_ip_number() +"\n");
// let's not put useless work on erq
// +query_ip_name()+" ["+query_ip_number()+"].\n";
} else write("501 Syntax: HELO hostname\n");
break;
case "MAIL":
case "SEND":
case "SOML":
case "SAML":
vars["_method_SMTP"] = cmd;
if (upper_case(all[0..4]) == "FROM:") {
origin = all[5] == ' ' ? all[6..] : all[5..];
host = query_ip_number();
if (ADDRPARSE(origin, user, host)) {
vars["_nick"] = origin = user +"@"+ host;
P3(("smtpcmd %s %O » %s\n", cmd, all, origin))
write("250 Sender superficially ok\n");
break;
}
}
write("501 Syntax: MAIL FROM: <address>\n");
break;
case "RCPT":
// unless (origin) {
// write("503 Need MAIL before RCPT\n");
// break;
// }
if (upper_case(all[0..2]) == "TO:") {
target = all[3] == ' ' ? all[4..] : all[3..];
if (ADDRPARSE(target, user, host)) {
#ifdef SMTP_ALIASES
string rcpt;
vars["_nick_target"] = user;
if (user = smtp_aliases[rcpt = lower_case(user)]) {
vars["_nick_target_alias"] = user;
} else user = rcpt;
#else
vars["_nick_target"] = user;
user = lower_case(user);
#endif
if (strlen(user)) {
// find_person and legal_name are not necessary
// as summon_person / find_place do all of that
if (user[0] == GROUP_PREFIX)
target = find_place(user[1..]);
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else if
#ifdef _flag_disable_prefix_person_SMTP
(target = summon_person(user))
#else
(user[0] == PERSON_PREFIX
&& target = summon_person(user[1 ..]))
#endif
{
if (target->isNewbie()) target = 0;
}
if (target) {
vars["_host_target"] = host || "";
write("250 Recipient apparently ok\n");
break;
}
}
target = 0;
spam("_unknown_name_user", 0,
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"550 '"+user+"' unknown.\n");
// spam does a QUIT in this case. too harsh?
break;
}
}
write("501 Syntax: RCPT TO: <address>\n");
break;
case "DATA":
unless (origin && target) {
spam("_insufficient_data", 0,
"503 Watcha tryinta hack?\n");
// spam does a QUIT in this case. too harsh?
break;
}
//write("354 Enter mail, end with '.' on a line by itself.\n");
write("354 Alright now, "+ query_ip_name()
+", tell me the truth.\n");
// I'm reading your lips, baby. So you better not spam me.
// But most of all the purpose is to activate erq for name
// resolution at this point, since we will want the hostname
// later. Of course we might as well go thru async DNS later
// when we are absolutely sure we are going to keep the
// message. TODO one day.
header = text = "";
next_input_to(#'headers);
return 0;
case "QUIT":
write("221 "+ SERVER_HOST +" says: I like your pink tie\n");
QUIT
case "HELP":
write("221 Ask http://about.psyc.eu/SMTP for help\n"
"221 Commands: HELO, MAIL, SEND, SOML, SAML, RCPT, RSET, DATA, QUIT\n");
break;
default:
// some try binary overflow attacks here.. looks a bit ugly
// but obviously has null effect on an ldmud
P1(("SMTP %O got %O from %O\n", ME, asis, query_ip_number()))
//write("500 Command not recognized.\n");
write("500 Huh?\n"); // why even talk to guys like that?
QUIT
break;
}
return 1;
}
greet() {
remove_input_to(ME, #'quit);
next_input_to(#'parse);
vars = ([ ]);
// should provide a hint for upgrading to PSYC protocol.. TODO
write("220 ESMTP "+ SERVER_HOST +" makes me feel http://www.psyced.org\n"
#ifdef _flag_optimize_protection_SMTP
// multiline greetings is a SPAM deterrent provision. they are not
// explicitely permitted in the RFC, but aren't forbidden either.
// cheap SMTP implementations like python2.4/smtplib.py choke on this.
# define MORE "220 " // 211? just as evil..
MORE "This is the psyced receptionist talking\n"
MORE "You are best known as "+ query_ip_name() +"\n"
MORE "Thank you for waiting. It's a spam deterrent provision\n"
MORE "Somebody also said that multiline greetings embarrass spammers\n"
MORE "If you like to spam, consider figure 1 at http://b-5.de/fig1/\n"
# undef MORE
#endif
);
}
logon() {
P2(("SMTP logon from %O\n", query_ip_number()))
#if DEBUG > 1
greet(); // make it easier for developers trying this out.
#else
call_out(#'greet, _time_logon_delay_SMTP);
// now wait a minute! .. almost
// this throws out spammers who think they can talk before
// being greeted
next_input_to(#'quit);
#endif
}