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function old new delta sendmail_main 934 939 +5 smtp_checkp 167 165 -2 packed_usage 28634 28621 -13 Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
355 lines
11 KiB
C
355 lines
11 KiB
C
/* vi: set sw=4 ts=4: */
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/*
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* bare bones sendmail
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*
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* Copyright (C) 2008 by Vladimir Dronnikov <dronnikov@gmail.com>
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*
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* Licensed under GPLv2, see file LICENSE in this source tree.
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*/
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//kbuild:lib-$(CONFIG_SENDMAIL) += sendmail.o mail.o
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//usage:#define sendmail_trivial_usage
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//usage: "[OPTIONS] [RECIPIENT_EMAIL]..."
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//usage:#define sendmail_full_usage "\n\n"
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//usage: "Read email from stdin and send it\n"
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//usage: "\nStandard options:"
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//usage: "\n -t Read additional recipients from message body"
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//usage: "\n -f SENDER Sender (required)"
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//usage: "\n -o OPTIONS Various options. -oi implied, others are ignored"
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//usage: "\n -i -oi synonym. implied and ignored"
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//usage: "\n"
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//usage: "\nBusybox specific options:"
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//usage: "\n -v Verbose"
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//usage: "\n -w SECS Network timeout"
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//usage: "\n -H 'PROG ARGS' Run connection helper"
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//usage: "\n Examples:"
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//usage: "\n -H 'exec openssl s_client -quiet -tls1 -starttls smtp"
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//usage: "\n -connect smtp.gmail.com:25' <email.txt"
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//usage: "\n [4<username_and_passwd.txt | -auUSER -apPASS]"
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//usage: "\n -H 'exec openssl s_client -quiet -tls1"
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//usage: "\n -connect smtp.gmail.com:465' <email.txt"
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//usage: "\n [4<username_and_passwd.txt | -auUSER -apPASS]"
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//usage: "\n -S HOST[:PORT] Server"
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//usage: "\n -auUSER Username for AUTH LOGIN"
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//usage: "\n -apPASS Password for AUTH LOGIN"
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////usage: "\n -amMETHOD Authentication method. Ignored. LOGIN is implied"
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//usage: "\n"
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//usage: "\nOther options are silently ignored; -oi -t is implied"
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//usage: IF_MAKEMIME(
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//usage: "\nUse makemime to create emails with attachments"
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//usage: )
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#include "libbb.h"
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#include "mail.h"
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// limit maximum allowed number of headers to prevent overflows.
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// set to 0 to not limit
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#define MAX_HEADERS 256
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static void send_r_n(const char *s)
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{
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if (verbose)
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bb_error_msg("send:'%s'", s);
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printf("%s\r\n", s);
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}
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static int smtp_checkp(const char *fmt, const char *param, int code)
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{
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char *answer;
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char *msg = send_mail_command(fmt, param);
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// read stdin
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// if the string has a form NNN- -- read next string. E.g. EHLO response
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// parse first bytes to a number
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// if code = -1 then just return this number
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// if code != -1 then checks whether the number equals the code
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// if not equal -> die saying msg
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while ((answer = xmalloc_fgetline(stdin)) != NULL) {
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if (verbose)
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bb_error_msg("recv:'%.*s'", (int)(strchrnul(answer, '\r') - answer), answer);
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if (strlen(answer) <= 3 || '-' != answer[3])
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break;
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free(answer);
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}
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if (answer) {
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int n = atoi(answer);
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if (timeout)
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alarm(0);
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free(answer);
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if (-1 == code || n == code) {
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free(msg);
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return n;
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}
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}
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bb_error_msg_and_die("%s failed", msg);
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}
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static int smtp_check(const char *fmt, int code)
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{
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return smtp_checkp(fmt, NULL, code);
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}
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// strip argument of bad chars
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static char *sane_address(char *str)
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{
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char *s = str;
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char *p = s;
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while (*s) {
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if (isalnum(*s) || '_' == *s || '-' == *s || '.' == *s || '@' == *s) {
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*p++ = *s;
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}
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s++;
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}
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*p = '\0';
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return str;
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}
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static void rcptto(const char *s)
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{
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// N.B. we don't die if recipient is rejected, for the other recipients may be accepted
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if (250 != smtp_checkp("RCPT TO:<%s>", s, -1))
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bb_error_msg("Bad recipient: <%s>", s);
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}
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int sendmail_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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int sendmail_main(int argc UNUSED_PARAM, char **argv)
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{
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char *opt_connect = opt_connect;
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char *opt_from;
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char *s;
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llist_t *list = NULL;
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char *domain = sane_address(safe_getdomainname());
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unsigned nheaders = 0;
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int code;
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enum {
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//--- standard options
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OPT_t = 1 << 0, // read message for recipients, append them to those on cmdline
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OPT_f = 1 << 1, // sender address
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OPT_o = 1 << 2, // various options. -oi IMPLIED! others are IGNORED!
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OPT_i = 1 << 3, // IMPLIED!
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//--- BB specific options
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OPT_w = 1 << 4, // network timeout
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OPT_H = 1 << 5, // use external connection helper
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OPT_S = 1 << 6, // specify connection string
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OPT_a = 1 << 7, // authentication tokens
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OPT_v = 1 << 8, // verbosity
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};
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// init global variables
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INIT_G();
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// save initial stdin since body is piped!
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xdup2(STDIN_FILENO, 3);
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G.fp0 = xfdopen_for_read(3);
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// parse options
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// -v is a counter, -f is required. -H and -S are mutually exclusive, -a is a list
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opt_complementary = "vv:f:w+:H--S:S--H:a::";
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// N.B. since -H and -S are mutually exclusive they do not interfere in opt_connect
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// -a is for ssmtp (http://downloads.openwrt.org/people/nico/man/man8/ssmtp.8.html) compatibility,
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// it is still under development.
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opts = getopt32(argv, "tf:o:iw:H:S:a::v", &opt_from, NULL,
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&timeout, &opt_connect, &opt_connect, &list, &verbose);
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//argc -= optind;
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argv += optind;
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// process -a[upm]<token> options
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if ((opts & OPT_a) && !list)
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bb_show_usage();
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while (list) {
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char *a = (char *) llist_pop(&list);
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if ('u' == a[0])
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G.user = xstrdup(a+1);
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if ('p' == a[0])
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G.pass = xstrdup(a+1);
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// N.B. we support only AUTH LOGIN so far
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//if ('m' == a[0])
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// G.method = xstrdup(a+1);
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}
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// N.B. list == NULL here
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//bb_info_msg("OPT[%x] AU[%s], AP[%s], AM[%s], ARGV[%s]", opts, au, ap, am, *argv);
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// connect to server
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// connection helper ordered? ->
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if (opts & OPT_H) {
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const char *args[] = { "sh", "-c", opt_connect, NULL };
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// plug it in
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launch_helper(args);
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// Now:
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// our stdout will go to helper's stdin,
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// helper's stdout will be available on our stdin.
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// Wait for initial server message.
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// If helper (such as openssl) invokes STARTTLS, the initial 220
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// is swallowed by helper (and not repeated after TLS is initiated).
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// We will send NOOP cmd to server and check the response.
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// We should get 220+250 on plain connection, 250 on STARTTLSed session.
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//
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// The problem here is some servers delay initial 220 message,
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// and consider client to be a spammer if it starts sending cmds
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// before 220 reached it. The code below is unsafe in this regard:
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// in non-STARTTLSed case, we potentially send NOOP before 220
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// is sent by server.
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// Ideas? (--delay SECS opt? --assume-starttls-helper opt?)
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code = smtp_check("NOOP", -1);
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if (code == 220)
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// we got 220 - this is not STARTTLSed connection,
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// eat 250 response to our NOOP
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smtp_check(NULL, 250);
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else
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if (code != 250)
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bb_error_msg_and_die("SMTP init failed");
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} else {
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// vanilla connection
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int fd;
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// host[:port] not explicitly specified? -> use $SMTPHOST
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// no $SMTPHOST? -> use localhost
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if (!(opts & OPT_S)) {
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opt_connect = getenv("SMTPHOST");
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if (!opt_connect)
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opt_connect = (char *)"127.0.0.1";
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}
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// do connect
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fd = create_and_connect_stream_or_die(opt_connect, 25);
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// and make ourselves a simple IO filter
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xmove_fd(fd, STDIN_FILENO);
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xdup2(STDIN_FILENO, STDOUT_FILENO);
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// Wait for initial server 220 message
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smtp_check(NULL, 220);
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}
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// we should start with modern EHLO
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if (250 != smtp_checkp("EHLO %s", domain, -1))
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smtp_checkp("HELO %s", domain, 250);
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// perform authentication
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if (opts & OPT_a) {
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smtp_check("AUTH LOGIN", 334);
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// we must read credentials unless they are given via -a[up] options
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if (!G.user || !G.pass)
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get_cred_or_die(4);
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encode_base64(NULL, G.user, NULL);
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smtp_check("", 334);
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encode_base64(NULL, G.pass, NULL);
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smtp_check("", 235);
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}
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// set sender
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// N.B. we have here a very loosely defined algorythm
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// since sendmail historically offers no means to specify secrets on cmdline.
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// 1) server can require no authentication ->
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// we must just provide a (possibly fake) reply address.
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// 2) server can require AUTH ->
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// we must provide valid username and password along with a (possibly fake) reply address.
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// For the sake of security username and password are to be read either from console or from a secured file.
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// Since reading from console may defeat usability, the solution is either to read from a predefined
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// file descriptor (e.g. 4), or again from a secured file.
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// got no sender address? -> use system username as a resort
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// N.B. we marked -f as required option!
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//if (!G.user) {
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// // N.B. IMHO getenv("USER") can be way easily spoofed!
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// G.user = xuid2uname(getuid());
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// opt_from = xasprintf("%s@%s", G.user, domain);
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//}
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smtp_checkp("MAIL FROM:<%s>", opt_from, 250);
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// process message
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// read recipients from message and add them to those given on cmdline.
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// this means we scan stdin for To:, Cc:, Bcc: lines until an empty line
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// and then use the rest of stdin as message body
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code = 0; // set "analyze headers" mode
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while ((s = xmalloc_fgetline(G.fp0)) != NULL) {
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dump:
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// put message lines doubling leading dots
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if (code) {
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// escape leading dots
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// N.B. this feature is implied even if no -i (-oi) switch given
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// N.B. we need to escape the leading dot regardless of
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// whether it is single or not character on the line
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if ('.' == s[0] /*&& '\0' == s[1] */)
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printf(".");
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// dump read line
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send_r_n(s);
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free(s);
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continue;
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}
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// analyze headers
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// To: or Cc: headers add recipients
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if (0 == strncasecmp("To:", s, 3) || 0 == strncasecmp("Bcc:" + 1, s, 3)) {
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rcptto(sane_address(s+3));
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goto addheader;
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}
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// Bcc: header adds blind copy (hidden) recipient
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if (0 == strncasecmp("Bcc:", s, 4)) {
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rcptto(sane_address(s+4));
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free(s);
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// N.B. Bcc: vanishes from headers!
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} else
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if (strchr(s, ':') || (list && skip_whitespace(s) != s)) {
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// other headers go verbatim
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// N.B. RFC2822 2.2.3 "Long Header Fields" allows for headers to occupy several lines.
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// Continuation is denoted by prefixing additional lines with whitespace(s).
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// Thanks (stefan.seyfried at googlemail.com) for pointing this out.
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addheader:
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// N.B. we allow MAX_HEADERS generic headers at most to prevent attacks
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if (MAX_HEADERS && ++nheaders >= MAX_HEADERS)
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goto bail;
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llist_add_to_end(&list, s);
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} else {
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// a line without ":" (an empty line too, by definition) doesn't look like a valid header
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// so stop "analyze headers" mode
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reenter:
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// put recipients specified on cmdline
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while (*argv) {
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char *t = sane_address(*argv);
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rcptto(t);
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//if (MAX_HEADERS && ++nheaders >= MAX_HEADERS)
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// goto bail;
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llist_add_to_end(&list, xasprintf("To: %s", t));
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argv++;
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}
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// enter "put message" mode
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// N.B. DATA fails iff no recipients were accepted (or even provided)
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// in this case just bail out gracefully
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if (354 != smtp_check("DATA", -1))
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goto bail;
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// dump the headers
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while (list) {
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send_r_n((char *) llist_pop(&list));
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}
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// stop analyzing headers
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code++;
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// N.B. !s means: we read nothing, and nothing to be read in the future.
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// just dump empty line and break the loop
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if (!s) {
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send_r_n("");
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break;
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}
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// go dump message body
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// N.B. "s" already contains the first non-header line, so pretend we read it from input
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goto dump;
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}
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}
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// odd case: we didn't stop "analyze headers" mode -> message body is empty. Reenter the loop
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// N.B. after reenter code will be > 0
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if (!code)
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goto reenter;
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// finalize the message
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smtp_check(".", 250);
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bail:
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// ... and say goodbye
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smtp_check("QUIT", 221);
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// cleanup
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if (ENABLE_FEATURE_CLEAN_UP)
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fclose(G.fp0);
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return EXIT_SUCCESS;
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}
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