/* vi: set sw=4 ts=4: */ /* * bare bones sendmail * * Copyright (C) 2008 by Vladimir Dronnikov * * Licensed under GPLv2, see file LICENSE in this tarball for details. */ #include "libbb.h" #include "mail.h" static int smtp_checkp(const char *fmt, const char *param, int code) { char *answer; const char *msg = command(fmt, param); // read stdin // if the string has a form \d\d\d- -- read next string. E.g. EHLO response // parse first bytes to a number // if code = -1 then just return this number // if code != -1 then checks whether the number equals the code // if not equal -> die saying msg while ((answer = xmalloc_fgetline(stdin)) != NULL) if (strlen(answer) <= 3 || '-' != answer[3]) break; if (answer) { int n = atoi(answer); if (timeout) alarm(0); free(answer); if (-1 == code || n == code) return n; } bb_error_msg_and_die("%s failed", msg); } static int smtp_check(const char *fmt, int code) { return smtp_checkp(fmt, NULL, code); } // strip argument of bad chars static char *sane_address(char *str) { char *s = str; char *p = s; while (*s) { if (isalnum(*s) || '_' == *s || '-' == *s || '.' == *s || '@' == *s) { *p++ = *s; } s++; } *p = '\0'; return str; } static void rcptto(const char *s) { smtp_checkp("RCPT TO:<%s>", s, 250); } int sendmail_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; int sendmail_main(int argc UNUSED_PARAM, char **argv) { #if ENABLE_FEATURE_SENDMAIL_MAILX llist_t *opt_attachments = NULL; const char *opt_subject; #if ENABLE_FEATURE_SENDMAIL_MAILXX llist_t *opt_carboncopies = NULL; char *opt_errors_to; #endif #endif char *opt_connect = opt_connect; char *opt_from, *opt_fullname; char *boundary; llist_t *l; llist_t *headers = NULL; char *domain = sane_address(safe_getdomainname()); int code; enum { OPT_w = 1 << 0, // network timeout OPT_t = 1 << 1, // read message for recipients OPT_N = 1 << 2, // request notification OPT_f = 1 << 3, // sender address OPT_F = 1 << 4, // sender name, overrides $NAME OPT_s = 1 << 5, // subject OPT_j = 1 << 6, // assumed charset OPT_a = 1 << 7, // attachment(s) OPT_H = 1 << 8, // use external connection helper OPT_S = 1 << 9, // specify connection string OPT_c = 1 << 10, // carbon copy OPT_e = 1 << 11, // errors-to address }; // init global variables INIT_G(); // save initial stdin since body is piped! xdup2(STDIN_FILENO, 3); G.fp0 = fdopen(3, "r"); // parse options opt_complementary = "w+" USE_FEATURE_SENDMAIL_MAILX(":a::H--S:S--H") USE_FEATURE_SENDMAIL_MAILXX(":c::"); opts = getopt32(argv, "w:t" "N:f:F:" USE_FEATURE_SENDMAIL_MAILX("s:j:a:H:S:") USE_FEATURE_SENDMAIL_MAILXX("c:e:") "X:V:vq:R:O:o:nmL:Iih:GC:B:b:A:" // postfix compat only, ignored // r:Q:p:M:Dd are candidates from another man page. TODO? "46E", // ssmtp introduces another quirks. TODO?: -a[upm] (user, pass, method) to be supported &timeout /* -w */, NULL, &opt_from, &opt_fullname, USE_FEATURE_SENDMAIL_MAILX(&opt_subject, &G.opt_charset, &opt_attachments, &opt_connect, &opt_connect,) USE_FEATURE_SENDMAIL_MAILXX(&opt_carboncopies, &opt_errors_to,) NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL ); //argc -= optind; argv += optind; // connect to server #if ENABLE_FEATURE_SENDMAIL_MAILX // N.B. -H and -S are mutually exclusive so they do not spoil opt_connect // connection helper ordered? -> if (opts & OPT_H) { const char *args[] = { "sh", "-c", opt_connect, NULL }; // plug it in launch_helper(args); // vanilla connection } else #endif { 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); xdup2(STDIN_FILENO, STDOUT_FILENO); } // N.B. from now we know nothing about network :) // wait for initial server OK // N.B. if we used openssl the initial 220 answer is already swallowed during openssl TLS init procedure // so we need to push the server to see whether we are ok code = smtp_check("NOOP", -1); // 220 on plain connection, 250 on openssl-helped TLS session if (220 == code) smtp_check(NULL, 250); // reread the code to stay in sync else if (250 != code) bb_error_msg_and_die("INIT failed"); // we should start with modern EHLO if (250 != smtp_checkp("EHLO %s", domain, -1)) { smtp_checkp("HELO %s", domain, 250); } // set sender // N.B. we have here a very loosely defined algotythm // since sendmail historically offers no means to specify secrets on cmdline. // 1) server can require no authentication -> // we must just provide a (possibly fake) reply address. // 2) server can require AUTH -> // we must provide valid username and password along with a (possibly fake) reply address. // For the sake of security username and password are to be read either from console or from a secured file. // Since reading from console may defeat usability, the solution is either to read from a predefined // file descriptor (e.g. 4), or again from a secured file. // got no sender address? -> use system username as a resort if (!(opts & OPT_f)) { // N.B. IMHO getenv("USER") can be way easily spoofed! G.user = xuid2uname(getuid()); opt_from = xasprintf("%s@%s", G.user, domain); } if (ENABLE_FEATURE_CLEAN_UP) free(domain); code = -1; // first try softly without authentication while (250 != smtp_checkp("MAIL FROM:<%s>", opt_from, code)) { // MAIL FROM failed -> authentication needed if (334 == smtp_check("AUTH LOGIN", -1)) { // we must read credentials get_cred_or_die(4); encode_base64(NULL, G.user, NULL); smtp_check("", 334); encode_base64(NULL, G.pass, NULL); smtp_check("", 235); } // authenticated OK? -> retry to set sender // but this time die on failure! code = 250; } // recipients specified as arguments while (*argv) { char *s = sane_address(*argv); // loose test on email address validity // if (strchr(s, '@')) { rcptto(s); llist_add_to_end(&headers, xasprintf("To: %s", s)); // } argv++; } #if ENABLE_FEATURE_SENDMAIL_MAILXX // carbon copies recipients specified as -c options for (l = opt_carboncopies; l; l = l->link) { char *s = sane_address(l->data); // loose test on email address validity // if (strchr(s, '@')) { rcptto(s); // TODO: do we ever need to mangle the message? //llist_add_to_end(&headers, xasprintf("Cc: %s", s)); // } } #endif // if -t specified or no recipients specified -> read recipients from message // i.e. scan stdin for To:, Cc:, Bcc: lines ... // ... and then use the rest of stdin as message body // N.B. subject read from body can be further overrided with one specified on command line. // recipients are merged. Bcc: lines are deleted // N.B. other headers are collected and will be dumped verbatim if (opts & OPT_t || !headers) { // fetch recipients and (optionally) subject char *s; while ((s = xmalloc_fgetline(G.fp0)) != NULL) { if (0 == strncasecmp("To: ", s, 4) || 0 == strncasecmp("Cc: ", s, 4)) { rcptto(sane_address(s+4)); llist_add_to_end(&headers, s); } else if (0 == strncasecmp("Bcc: ", s, 5)) { rcptto(sane_address(s+5)); free(s); // N.B. Bcc vanishes from headers! } else if (0 == strncmp("Subject: ", s, 9)) { // we read subject -> use it verbatim unless it is specified // on command line if (!(opts & OPT_s)) llist_add_to_end(&headers, s); else free(s); } else if (s[0]) { // misc header llist_add_to_end(&headers, s); } else { free(s); break; // stop on the first empty line } } } // enter "put message" mode smtp_check("DATA", 354); // put headers we could have preread with -t for (l = headers; l; l = l->link) { printf("%s\r\n", l->data); if (ENABLE_FEATURE_CLEAN_UP) free(l->data); } // put (possibly encoded) subject #if ENABLE_FEATURE_SENDMAIL_MAILX if (opts & OPT_s) { printf("Subject: "); if (opts & OPT_j) { printf("=?%s?B?", G.opt_charset); encode_base64(NULL, opt_subject, NULL); printf("?="); } else { printf("%s", opt_subject); } printf("\r\n"); } #endif // put sender name, $NAME is the default if (!(opts & OPT_F)) opt_fullname = getenv("NAME"); if (opt_fullname) printf("From: \"%s\" <%s>\r\n", opt_fullname, opt_from); // put notification if (opts & OPT_N) printf("Disposition-Notification-To: %s\r\n", opt_from); #if ENABLE_FEATURE_SENDMAIL_MAILXX // put errors recipient if (opts & OPT_e) printf("Errors-To: %s\r\n", opt_errors_to); #endif // make a random string -- it will delimit message parts srand(monotonic_us()); boundary = xasprintf("%d=_%d-%d", rand(), rand(), rand()); // put common headers // TODO: do we really need this? // printf("Message-ID: <%s>\r\n", boundary); #if ENABLE_FEATURE_SENDMAIL_MAILX // have attachments? -> compose multipart MIME if (opt_attachments) { const char *fmt; const char *p; char *q; printf( "Mime-Version: 1.0\r\n" "%smultipart/mixed; boundary=\"%s\"\r\n" , "Content-Type: " , boundary ); // body is pseudo attachment read from stdin in first turn llist_add_to(&opt_attachments, (char *)"-"); // put body + attachment(s) // N.B. all these weird things just to be tiny // by reusing string patterns! fmt = "\r\n--%s\r\n" "%stext/plain; charset=%s\r\n" "%s%s\r\n" "%s" ; p = G.opt_charset; q = (char *)""; l = opt_attachments; while (l) { printf( fmt , boundary , "Content-Type: " , p , "Content-Disposition: inline" , q , "Content-Transfer-Encoding: base64\r\n" ); p = ""; fmt = "\r\n--%s\r\n" "%sapplication/octet-stream%s\r\n" "%s; filename=\"%s\"\r\n" "%s" ; encode_base64(l->data, (const char *)G.fp0, "\r"); l = l->link; if (l) q = bb_get_last_path_component_strip(l->data); } // put message terminator printf("\r\n--%s--\r\n" "\r\n", boundary); // no attachments? -> just dump message } else #endif { char *s; // terminate headers printf("\r\n"); // put plain text respecting leading dots while ((s = xmalloc_fgetline(G.fp0)) != NULL) { // escape leading dots // N.B. this feature is implied even if no -i (-oi) switch given // N.B. we need to escape the leading dot regardless of // whether it is single or not character on the line if ('.' == s[0] /*&& '\0' == s[1] */) printf("."); // dump read line printf("%s\r\n", s); } } // leave "put message" mode smtp_check(".", 250); // ... and say goodbye smtp_check("QUIT", 221); // cleanup if (ENABLE_FEATURE_CLEAN_UP) fclose(G.fp0); return EXIT_SUCCESS; }