/* vi: set sw=4 ts=4: */ /* * bare bones sendmail/fetchmail * * Copyright (C) 2008 by Vladimir Dronnikov * * Licensed under GPLv2, see file LICENSE in this tarball for details. */ #include "libbb.h" #define INITIAL_STDIN_FILENO 3 static void uuencode(char *fname, const char *text) { enum { SRC_BUF_SIZE = 45, /* This *MUST* be a multiple of 3 */ DST_BUF_SIZE = 4 * ((SRC_BUF_SIZE + 2) / 3), }; #define src_buf text int fd; #define len fd char dst_buf[DST_BUF_SIZE + 1]; if (fname) { fd = INITIAL_STDIN_FILENO; if (NOT_LONE_DASH(fname)) fd = xopen(fname, O_RDONLY); src_buf = bb_common_bufsiz1; // N.B. strlen(NULL) segfaults! } else if (text) { // though we do not call uuencode(NULL, NULL) explicitly // still we do not want to break things suddenly len = strlen(text); } else return; fflush(stdout); // sync stdio and unistd output while (1) { size_t size; if (fname) { size = full_read(fd, (char *)src_buf, SRC_BUF_SIZE); if ((ssize_t)size < 0) bb_perror_msg_and_die(bb_msg_read_error); } else { size = len; if (len > SRC_BUF_SIZE) size = SRC_BUF_SIZE; } if (!size) break; // encode the buffer we just read in bb_uuencode(dst_buf, src_buf, size, bb_uuenc_tbl_base64); if (fname) { xwrite(STDOUT_FILENO, "\r\n", 2); } else { src_buf += size; len -= size; } xwrite(STDOUT_FILENO, dst_buf, 4 * ((size + 2) / 3)); } if (fname) close(fd); #undef src_buf #undef len } struct globals { pid_t helper_pid; unsigned timeout; // arguments for SSL connection helper const char *xargs[9]; // arguments for postprocess helper const char *fargs[3]; }; #define G (*ptr_to_globals) #define helper_pid (G.helper_pid) #define timeout (G.timeout ) #define xargs (G.xargs ) #define fargs (G.fargs ) #define INIT_G() do { \ SET_PTR_TO_GLOBALS(xzalloc(sizeof(G))); \ xargs[0] = "openssl"; \ xargs[1] = "s_client"; \ xargs[2] = "-quiet"; \ xargs[3] = "-connect"; \ /*xargs[4] = "localhost";*/ \ xargs[5] = "-tls1"; \ xargs[6] = "-starttls"; \ xargs[7] = "smtp"; \ fargs[0] = "utf-8"; \ } while (0) #define opt_connect (xargs[4]) #define opt_after_connect (xargs[5]) #define opt_charset (fargs[0]) #define opt_subject (fargs[1]) static void kill_helper(void) { // TODO!!!: is there more elegant way to terminate child on program failure? if (helper_pid > 0) kill(helper_pid, SIGTERM); } // generic signal handler static void signal_handler(int signo) { #define err signo if (SIGALRM == signo) { kill_helper(); bb_error_msg_and_die("timed out"); } // SIGCHLD. reap zombies if (wait_any_nohang(&err) > 0) if (WIFEXITED(err) && WEXITSTATUS(err)) bb_error_msg_and_die("child exited (%d)", WEXITSTATUS(err)); #undef err } /* libbb candidate */ static pid_t vfork_or_die(void) { pid_t pid = vfork(); if (pid < 0) bb_perror_msg_and_die("vfork"); return pid; } static void launch_helper(const char **argv) { // setup vanilla unidirectional pipes interchange int idx; int pipes[4]; xpipe(pipes); xpipe(pipes+2); helper_pid = vfork_or_die(); idx = (!helper_pid) * 2; xdup2(pipes[idx], STDIN_FILENO); xdup2(pipes[3-idx], STDOUT_FILENO); if (ENABLE_FEATURE_CLEAN_UP) for (int i = 4; --i >= 0; ) if (pipes[i] > STDOUT_FILENO) close(pipes[i]); if (!helper_pid) { // child: try to execute connection helper BB_EXECVP(*argv, (char **)argv); _exit(127); } // parent: check whether child is alive bb_signals(0 + (1 << SIGCHLD) + (1 << SIGALRM) , signal_handler); signal_handler(SIGCHLD); // child seems OK -> parent goes on } static const char *command(const char *fmt, const char *param) { const char *msg = fmt; alarm(timeout); if (msg) { msg = xasprintf(fmt, param); printf("%s\r\n", msg); } fflush(stdout); return msg; } 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); alarm(0); if (ENABLE_FEATURE_CLEAN_UP) { free(answer); } if (-1 == code || n == code) { return n; } } kill_helper(); bb_error_msg_and_die("%s failed", msg); } static inline int smtp_check(const char *fmt, int code) { return smtp_checkp(fmt, NULL, code); } // strip argument of bad chars static char *sane(char *str) { char *s = str; char *p = s; while (*s) { if (isalnum(*s) || '_' == *s || '-' == *s || '.' == *s || '@' == *s) { *p++ = *s; } s++; } *p = '\0'; return str; } #if ENABLE_FETCHMAIL static void pop3_checkr(const char *fmt, const char *param, char **ret) { const char *msg = command(fmt, param); char *answer = xmalloc_fgetline(stdin); if (answer && '+' == *answer) { alarm(0); if (ret) *ret = answer+4; // skip "+OK " else if (ENABLE_FEATURE_CLEAN_UP) free(answer); return; } kill_helper(); bb_error_msg_and_die("%s failed", msg); } static inline void pop3_check(const char *fmt, const char *param) { pop3_checkr(fmt, param, NULL); } static void pop3_message(const char *filename) { int fd; char *answer; // create and open file filename // read stdin, copy to created file fd = xopen(filename, O_CREAT | O_WRONLY | O_TRUNC | O_EXCL); while ((answer = xmalloc_fgets_str(stdin, "\r\n")) != NULL) { char *s = answer; if ('.' == *answer) { if ('.' == answer[1]) s++; else if ('\r' == answer[1] && '\n' == answer[2] && '\0' == answer[3]) break; } xwrite(fd, s, strlen(s)); free(answer); } close(fd); } #endif static char *parse_url(char *url, char **user, char **pass) { // parse [user[:pass]@]host // return host char *s = strchr(url, '@'); *user = *pass = NULL; if (s) { *s++ = '\0'; *user = url; url = s; s = strchr(*user, ':'); if (s) { *s++ = '\0'; *pass = s; } } return url; } int sendgetmail_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; int sendgetmail_main(int argc ATTRIBUTE_UNUSED, char **argv) { llist_t *opt_recipients = NULL; llist_t *opt_attachments = NULL; char *opt_from; char *opt_user; char *opt_pass; enum { OPT_w = 1 << 0, // network timeout OPT_H = 1 << 1, // [user:password@]server[:port] OPT_S = 1 << 2, // connect using openssl s_client helper OPTS_t = 1 << 3, // sendmail: read addresses from body OPTF_t = 1 << 3, // fetchmail: use "TOP" not "RETR" OPTS_s = 1 << 4, // sendmail: subject OPTF_z = 1 << 4, // fetchmail: delete from server OPTS_c = 1 << 5, // sendmail: assumed charset OPTS_a = 1 << 6, // sendmail: attachment(s) OPTS_i = 1 << 7, // sendmail: ignore lone dots in message body (implied) OPTS_N = 1 << 8, // sendmail: request notification }; const char *options; int opts; // init global variables INIT_G(); // parse options, different option sets for sendmail and fetchmail // N.B. opt_after_connect hereafter is NULL if we are called as fetchmail // and is NOT NULL if we are called as sendmail if (!ENABLE_FETCHMAIL || 's' == applet_name[0]) { // SENDMAIL // save initial stdin (body or attachements can be piped!) xdup2(STDIN_FILENO, INITIAL_STDIN_FILENO); opt_complementary = "w+:a::"; options = "w:H:St" "s:c:a:iN:f:"; // body is pseudo attachment read from stdin llist_add_to_end(&opt_attachments, (char *)"-"); } else { // FETCHMAIL opt_after_connect = NULL; opt_complementary = "-1:w+"; options = "w:H:St" "z"; } opts = getopt32(argv, options, &timeout /* -w */, &opt_connect /* -H */, &opt_subject, &opt_charset, &opt_attachments, NULL, &opt_from ); //argc -= optind; argv += optind; // connect to server // host[:port] not specified ? -> use $HOST. no $HOST ? -> use localhost if (!(opts & OPT_H)) { opt_connect = getenv("HOST"); if (!opt_connect) opt_connect = "127.0.0.1"; } // fetch username and password, if any // NB: parse_url modifies opt_connect[] ONLY if '@' is there. // Thus "127.0.0.1" won't be modified, an is ok that it is RO. opt_connect = parse_url((char*)opt_connect, &opt_user, &opt_pass); // bb_error_msg("H[%s] U[%s] P[%s]", opt_connect, opt_user, opt_pass); // SSL ordered? -> if (opts & OPT_S) { // ... use openssl helper launch_helper(xargs); // no SSL ordered? -> } else { // ... make plain connect int fd = create_and_connect_stream_or_die(opt_connect, 25); // make ourselves a simple IO filter // from now we know nothing about network :) xmove_fd(fd, STDIN_FILENO); xdup2(STDIN_FILENO, STDOUT_FILENO); } // are we sendmail? if (!ENABLE_FETCHMAIL || opt_after_connect) /*************************************************** * SENDMAIL ***************************************************/ { int code; char *boundary; const char *fmt; const char *p; char *q; llist_t *l; // recipients specified as arguments while (*argv) { // loose test on email address validity if (strchr(sane(*argv), '@')) llist_add_to_end(&opt_recipients, *argv); argv++; } // we didn't use SSL helper? -> if (!(opts & OPT_S)) { // ... wait for initial server OK smtp_check(NULL, 220); } // if -t specified or no recipients specified -> enter all-included mode // i.e. scan stdin for To: and Subject: lines ... // ... and then use the rest of stdin as message body // N.B. subject read from body has priority // over that specified on command line. // recipients are merged if (opts & OPTS_t || !opt_recipients) { // fetch recipients and (optionally) subject char *s; while ((s = xmalloc_reads(INITIAL_STDIN_FILENO, NULL, NULL)) != NULL) { if (0 == strncmp("To: ", s, 4)) { llist_add_to_end(&opt_recipients, s+4); } else if (0 == strncmp("Subject: ", s, 9)) { opt_subject = s+9; opts |= OPTS_s; } else { char first = s[0]; free(s); if (!first) break; // empty line } } } // introduce to server // we should start with modern EHLO if (250 != smtp_checkp("EHLO %s", sane(opt_from), -1)) { smtp_checkp("HELO %s", opt_from, 250); } // set sender // NOTE: if password has not been specified // then no authentication is possible code = (opt_pass) ? -1 : 250; // first try softly without authentication while (250 != smtp_checkp("MAIL FROM:<%s>", opt_from, code)) { // MAIL FROM failed -> authentication needed // have we got username? if (!opt_user) { // no! fetch it from "from" option opt_user = xstrdup(opt_from); *strchrnul(opt_user, '@') = '\0'; } // now we've got username // so try to authenticate if (334 == smtp_check("AUTH LOGIN", -1)) { uuencode(NULL, opt_user); smtp_check("", 334); uuencode(NULL, opt_pass); smtp_check("", 235); } // authenticated OK? -> retry to set sender // but this time die on failure! code = 250; } // set recipients for (l = opt_recipients; l; l = l->link) { smtp_checkp("RCPT TO:<%s>", sane(l->data), 250); } // enter "put message" mode smtp_check("DATA", 354); // put address headers printf("From: %s\r\n", opt_from); for (l = opt_recipients; l; l = l->link) { printf("To: %s\r\n", l->data); } // put encoded subject if (opts & OPTS_c) sane((char *)opt_charset); if (opts & OPTS_s) { printf("Subject: =?%s?B?", opt_charset); uuencode(NULL, opt_subject); printf("?=\r\n"); } // put notification if (opts & OPTS_N) printf("Disposition-Notification-To: %s\r\n", opt_from); // make a random string -- it will delimit message parts srand(monotonic_us()); boundary = xasprintf("%d-%d-%d", rand(), rand(), rand()); // put common headers and body start printf( "Message-ID: <%s>\r\n" "Mime-Version: 1.0\r\n" "%smultipart/mixed; boundary=\"%s\"\r\n" , boundary , "Content-Type: " , boundary ); // 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 = 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" ; uuencode(l->data, NULL); 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); // leave "put message" mode smtp_check(".", 250); // ... and say goodbye smtp_check("QUIT", 221); } #if ENABLE_FETCHMAIL /*************************************************** * FETCHMAIL ***************************************************/ else { char *buf; unsigned nmsg; char *hostname; pid_t pid; // cache fetch command: // TOP will return only the headers // RETR will dump the whole message const char *retr = (opts & OPTF_t) ? "TOP %u 0" : "RETR %u"; // goto maildir xchdir(*argv++); // cache postprocess program *fargs = *argv; // authenticate if (!opt_user) { // N.B. IMHO getenv("USER") can be way easily spoofed! opt_user = bb_getpwuid(NULL, -1, getuid()); } // password is mandatory if (!opt_pass) { bb_error_msg_and_die("no password"); } // get server greeting pop3_checkr(NULL, NULL, &buf); // server supports APOP? if ('<' == *buf) { md5_ctx_t md5; // yes! compose char *s = strchr(buf, '>'); if (s) strcpy(s+1, opt_pass); s = buf; // get md5 sum of md5_begin(&md5); md5_hash(s, strlen(s), &md5); md5_end(s, &md5); // NOTE: md5 struct contains enough space // so we reuse md5 space instead of xzalloc(16*2+1) #define md5_hex ((uint8_t *)&md5) // uint8_t *md5_hex = (uint8_t *)&md5; *bin2hex((char *)md5_hex, s, 16) = '\0'; // APOP s = xasprintf("%s %s", opt_user, md5_hex); #undef md5_hex pop3_check("APOP %s", s); if (ENABLE_FEATURE_CLEAN_UP) { free(s); free(buf-4); // buf is "+OK " away from malloc'ed string } // server ignores APOP -> use simple text authentication } else { // USER pop3_check("USER %s", opt_user); // PASS pop3_check("PASS %s", opt_pass); } // get mailbox statistics pop3_checkr("STAT", NULL, &buf); // prepare message filename suffix hostname = safe_gethostname(); pid = getpid(); // get messages counter // NOTE: we don't use xatou(buf) since buf is "nmsg nbytes" // we only need nmsg and atoi is just exactly what we need // if atoi fails to convert buf into number it returns 0 // in this case the following loop simply will not be executed nmsg = atoi(buf); if (ENABLE_FEATURE_CLEAN_UP) free(buf-4); // buf is "+OK " away from malloc'ed string // loop through messages for (; nmsg; nmsg--) { // generate unique filename char *filename = xasprintf("tmp/%llu.%u.%s", monotonic_us(), (unsigned)pid, hostname); char *target; int rc; // retrieve message in ./tmp/ pop3_check(retr, (const char *)(ptrdiff_t)nmsg); pop3_message(filename); // delete message from server if (opts & OPTF_z) pop3_check("DELE %u", (const char*)(ptrdiff_t)nmsg); // run postprocessing program if (*fargs) { fargs[1] = filename; rc = wait4pid(spawn((char **)fargs)); if (99 == rc) break; if (1 == rc) goto skip; } // atomically move message to ./new/ target = xstrdup(filename); strncpy(target, "new", 3); // ... or just stop receiving on error if (rename_or_warn(filename, target)) break; free(target); skip: free(filename); } // Bye pop3_check("QUIT", NULL); } #endif // ENABLE_FETCHMAIL return 0; }