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https://github.com/sheumann/hush.git
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389 lines
11 KiB
C
389 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 tarball for details.
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*/
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#include "libbb.h"
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#include "mail.h"
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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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const char *msg = command(fmt, param);
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// read stdin
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// if the string has a form \d\d\d- -- 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 (strlen(answer) <= 3 || '-' != answer[3])
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break;
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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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return n;
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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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smtp_checkp("RCPT TO:<%s>", s, 250);
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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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#if ENABLE_FEATURE_SENDMAIL_MAILX
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llist_t *opt_attachments = NULL;
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const char *opt_subject;
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#if ENABLE_FEATURE_SENDMAIL_MAILXX
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llist_t *opt_carboncopies = NULL;
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char *opt_errors_to;
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#endif
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#endif
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char *opt_connect = opt_connect;
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char *opt_from, *opt_fullname;
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char *boundary;
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llist_t *l;
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llist_t *headers = NULL;
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char *domain = sane_address(safe_getdomainname());
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int code;
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enum {
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OPT_w = 1 << 0, // network timeout
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OPT_t = 1 << 1, // read message for recipients
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OPT_N = 1 << 2, // request notification
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OPT_f = 1 << 3, // sender address
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OPT_F = 1 << 4, // sender name, overrides $NAME
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OPT_s = 1 << 5, // subject
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OPT_j = 1 << 6, // assumed charset
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OPT_a = 1 << 7, // attachment(s)
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OPT_H = 1 << 8, // use external connection helper
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OPT_S = 1 << 9, // specify connection string
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OPT_c = 1 << 10, // carbon copy
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OPT_e = 1 << 11, // errors-to address
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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 = fdopen(3, "r");
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// parse options
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opt_complementary = "w+" USE_FEATURE_SENDMAIL_MAILX(":a::H--S:S--H") USE_FEATURE_SENDMAIL_MAILXX(":c::");
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opts = getopt32(argv,
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"w:t" "N:f:F:" USE_FEATURE_SENDMAIL_MAILX("s:j:a:H:S:") USE_FEATURE_SENDMAIL_MAILXX("c:e:")
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"X:V:vq:R:O:o:nmL:Iih:GC:B:b:A:" // postfix compat only, ignored
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// r:Q:p:M:Dd are candidates from another man page. TODO?
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"46E", // ssmtp introduces another quirks. TODO?: -a[upm] (user, pass, method) to be supported
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&timeout /* -w */, NULL, &opt_from, &opt_fullname,
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USE_FEATURE_SENDMAIL_MAILX(&opt_subject, &G.opt_charset, &opt_attachments, &opt_connect, &opt_connect,)
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USE_FEATURE_SENDMAIL_MAILXX(&opt_carboncopies, &opt_errors_to,)
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NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL
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);
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//argc -= optind;
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argv += optind;
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// connect to server
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#if ENABLE_FEATURE_SENDMAIL_MAILX
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// N.B. -H and -S are mutually exclusive so they do not spoil opt_connect
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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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// vanilla connection
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} else
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#endif
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{
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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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}
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// N.B. from now we know nothing about network :)
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// wait for initial server OK
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// N.B. if we used openssl the initial 220 answer is already swallowed during openssl TLS init procedure
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// so we need to push the server to see whether we are ok
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code = smtp_check("NOOP", -1);
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// 220 on plain connection, 250 on openssl-helped TLS session
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if (220 == code)
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smtp_check(NULL, 250); // reread the code to stay in sync
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else if (250 != code)
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bb_error_msg_and_die("INIT failed");
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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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}
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// set sender
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// N.B. we have here a very loosely defined algotythm
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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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if (!(opts & OPT_f)) {
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// N.B. IMHO getenv("USER") can be way easily spoofed!
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G.user = bb_getpwuid(NULL, -1, getuid());
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opt_from = xasprintf("%s@%s", G.user, domain);
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}
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if (ENABLE_FEATURE_CLEAN_UP)
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free(domain);
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code = -1; // first try softly without authentication
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while (250 != smtp_checkp("MAIL FROM:<%s>", opt_from, code)) {
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// MAIL FROM failed -> authentication needed
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if (334 == smtp_check("AUTH LOGIN", -1)) {
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// we must read credentials
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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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// authenticated OK? -> retry to set sender
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// but this time die on failure!
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code = 250;
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}
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// recipients specified as arguments
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while (*argv) {
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char *s = sane_address(*argv);
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// loose test on email address validity
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// if (strchr(s, '@')) {
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rcptto(s);
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llist_add_to_end(&headers, xasprintf("To: %s", s));
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// }
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argv++;
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}
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#if ENABLE_FEATURE_SENDMAIL_MAILXX
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// carbon copies recipients specified as -c options
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for (l = opt_carboncopies; l; l = l->link) {
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char *s = sane_address(l->data);
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// loose test on email address validity
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// if (strchr(s, '@')) {
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rcptto(s);
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// TODO: do we ever need to mangle the message?
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//llist_add_to_end(&headers, xasprintf("Cc: %s", s));
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// }
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}
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#endif
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// if -t specified or no recipients specified -> read recipients from message
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// i.e. scan stdin for To:, Cc:, Bcc: lines ...
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// ... and then use the rest of stdin as message body
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// N.B. subject read from body can be further overrided with one specified on command line.
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// recipients are merged. Bcc: lines are deleted
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// N.B. other headers are collected and will be dumped verbatim
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if (opts & OPT_t || !headers) {
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// fetch recipients and (optionally) subject
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char *s;
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while ((s = xmalloc_fgetline(G.fp0)) != NULL) {
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if (0 == strncasecmp("To: ", s, 4) || 0 == strncasecmp("Cc: ", s, 4)) {
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rcptto(sane_address(s+4));
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llist_add_to_end(&headers, s);
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} else if (0 == strncasecmp("Bcc: ", s, 5)) {
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rcptto(sane_address(s+5));
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free(s);
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// N.B. Bcc vanishes from headers!
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} else if (0 == strncmp("Subject: ", s, 9)) {
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// we read subject -> use it verbatim unless it is specified
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// on command line
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if (!(opts & OPT_s))
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llist_add_to_end(&headers, s);
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else
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free(s);
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} else if (s[0]) {
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// misc header
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llist_add_to_end(&headers, s);
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} else {
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free(s);
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break; // stop on the first empty line
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}
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}
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}
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// enter "put message" mode
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smtp_check("DATA", 354);
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// put headers we could have preread with -t
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for (l = headers; l; l = l->link) {
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printf("%s\r\n", l->data);
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if (ENABLE_FEATURE_CLEAN_UP)
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free(l->data);
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}
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// put (possibly encoded) subject
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#if ENABLE_FEATURE_SENDMAIL_MAILX
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if (opts & OPT_s) {
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printf("Subject: ");
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if (opts & OPT_j) {
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printf("=?%s?B?", G.opt_charset);
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encode_base64(NULL, opt_subject, NULL);
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printf("?=");
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} else {
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printf("%s", opt_subject);
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}
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printf("\r\n");
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}
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#endif
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// put sender name, $NAME is the default
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if (!(opts & OPT_F))
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opt_fullname = getenv("NAME");
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if (opt_fullname)
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printf("From: \"%s\" <%s>\r\n", opt_fullname, opt_from);
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// put notification
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if (opts & OPT_N)
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printf("Disposition-Notification-To: %s\r\n", opt_from);
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#if ENABLE_FEATURE_SENDMAIL_MAILXX
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// put errors recipient
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if (opts & OPT_e)
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printf("Errors-To: %s\r\n", opt_errors_to);
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#endif
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// make a random string -- it will delimit message parts
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srand(monotonic_us());
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boundary = xasprintf("%d=_%d-%d", rand(), rand(), rand());
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// put common headers
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// TODO: do we really need this?
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// printf("Message-ID: <%s>\r\n", boundary);
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#if ENABLE_FEATURE_SENDMAIL_MAILX
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// have attachments? -> compose multipart MIME
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if (opt_attachments) {
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const char *fmt;
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const char *p;
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char *q;
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printf(
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"Mime-Version: 1.0\r\n"
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"%smultipart/mixed; boundary=\"%s\"\r\n"
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, "Content-Type: "
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, boundary
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);
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// body is pseudo attachment read from stdin in first turn
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llist_add_to(&opt_attachments, (char *)"-");
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// put body + attachment(s)
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// N.B. all these weird things just to be tiny
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// by reusing string patterns!
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fmt =
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"\r\n--%s\r\n"
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"%stext/plain; charset=%s\r\n"
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"%s%s\r\n"
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"%s"
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;
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p = G.opt_charset;
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q = (char *)"";
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l = opt_attachments;
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while (l) {
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printf(
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fmt
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, boundary
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, "Content-Type: "
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, p
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, "Content-Disposition: inline"
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, q
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, "Content-Transfer-Encoding: base64\r\n"
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);
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p = "";
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fmt =
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"\r\n--%s\r\n"
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"%sapplication/octet-stream%s\r\n"
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"%s; filename=\"%s\"\r\n"
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"%s"
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;
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encode_base64(l->data, (const char *)G.fp0, "\r");
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l = l->link;
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if (l)
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q = bb_get_last_path_component_strip(l->data);
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}
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// put message terminator
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printf("\r\n--%s--\r\n" "\r\n", boundary);
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// no attachments? -> just dump message
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} else
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#endif
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{
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char *s;
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// terminate headers
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printf("\r\n");
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// put plain text respecting leading dots
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while ((s = xmalloc_fgetline(G.fp0)) != NULL) {
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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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printf("%s\r\n", s);
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}
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}
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// leave "put message" mode
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smtp_check(".", 250);
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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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