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sendmail: make it possible to pause after connection helper is started

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If a non-starttls helper is in use, initial 220 response is processed by us,
not by helper.
Some servers consider us to be a spammer if we don't wait for it.

It is not in protocol, but it is a real-life problem.

The workaround in this patch is a magic envvar, $SMTP_ANTISPAM_DELAY:

...
	-H 'PROG ARGS'	Run connection helper. Examples:
		openssl s_client -quiet -tls1 -starttls smtp -connect smtp.gmail.com:25
		openssl s_client -quiet -tls1 -connect smtp.gmail.com:465
			$SMTP_ANTISPAM_DELAY: seconds to wait after helper connect
...

By using it, people can tweak sendmail behavior even if sendmail invocation
is buried in some scripts.

function                                             old     new   delta
packed_usage                                       30464   30497     +33
sendmail_main                                       1185    1206     +21
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 54/0)               Total: 54 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2016-09-07 13:16:33 +02:00
parent d42cdc2222
commit b9f56e82da
1 changed files with 14 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
mailutils/sendmail.c
View File

@ -27,6 +27,7 @@
//usage: "\n -H 'PROG ARGS' Run connection helper. Examples:"
//usage: "\n openssl s_client -quiet -tls1 -starttls smtp -connect smtp.gmail.com:25"
//usage: "\n openssl s_client -quiet -tls1 -connect smtp.gmail.com:465"
//usage: "\n $SMTP_ANTISPAM_DELAY: seconds to wait after helper connect"
//usage: "\n -S HOST[:PORT] Server (default $SMTPHOST or 127.0.0.1)"
//usage: "\n -amLOGIN Log in using AUTH LOGIN (-amCRAM-MD5 not supported)"
//usage: "\n -auUSER Username for AUTH"
@ -207,7 +208,7 @@ static void rcptto_list(const char *list)
int sendmail_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int sendmail_main(int argc UNUSED_PARAM, char **argv)
{
char *opt_connect = opt_connect;
char *opt_connect;
char *opt_from = NULL;
char *s;
llist_t *list = NULL;
@ -239,6 +240,11 @@ int sendmail_main(int argc UNUSED_PARAM, char **argv)
// init global variables
INIT_G();
// default HOST[:PORT] is $SMTPHOST, or localhost
opt_connect = getenv("SMTPHOST");
if (!opt_connect)
opt_connect = (char *)"127.0.0.1";
// save initial stdin since body is piped!
xdup2(STDIN_FILENO, 3);
G.fp0 = xfdopen_for_read(3);
@ -274,6 +280,7 @@ int sendmail_main(int argc UNUSED_PARAM, char **argv)
// connection helper ordered? ->
if (opts & OPT_H) {
const char *delay;
const char *args[] = { "sh", "-c", opt_connect, NULL };
// plug it in
launch_helper(args);
@ -292,7 +299,12 @@ int sendmail_main(int argc UNUSED_PARAM, char **argv)
// before 220 reached it. The code below is unsafe in this regard:
// in non-STARTTLSed case, we potentially send NOOP before 220
// is sent by server.
// Ideas? (--delay SECS opt? --assume-starttls-helper opt?)
//
// If $SMTP_ANTISPAM_DELAY is set, we pause before sending NOOP.
//
delay = getenv("SMTP_ANTISPAM_DELAY");
if (delay)
sleep(atoi(delay));
code = smtp_check("NOOP", -1);
if (code == 220)
// we got 220 - this is not STARTTLSed connection,
@ -304,14 +316,6 @@ int sendmail_main(int argc UNUSED_PARAM, char **argv)
} else {
// vanilla connection
int fd;
// host[:port] not explicitly specified? -> use $SMTPHOST
// no $SMTPHOST? -> use localhost
if (!(opts & OPT_S)) {
opt_connect = getenv("SMTPHOST");
if (!opt_connect)
opt_connect = (char *)"127.0.0.1";
}
// do connect
fd = create_and_connect_stream_or_die(opt_connect, 25);
// and make ourselves a simple IO filter
xmove_fd(fd, STDIN_FILENO);