hush/networking/sendmail.c

588 lines
14 KiB
C

/* vi: set sw=4 ts=4: */
/*
* bare bones sendmail/fetchmail
*
* Copyright (C) 2008 by Vladimir Dronnikov <dronnikov@gmail.com>
*
* 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);
}
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] = "server[:port]";*/ \
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));
}
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();
if (helper_pid < 0)
bb_perror_msg_and_die("vfork");
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_getline(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 int inline 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_getline(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 void inline 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
int sendgetmail_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int sendgetmail_main(int argc, char **argv)
{
llist_t *opt_recipients = NULL;
const char *opt_user;
const char *opt_pass;
enum {
OPT_w = 1 << 0, // network timeout
OPT_U = 1 << 1, // user
OPT_P = 1 << 2, // password
OPT_X = 1 << 3, // connect using openssl s_client helper
OPTS_n = 1 << 4, // sendmail: request notification
OPTF_t = 1 << 4, // fetchmail: use "TOP" not "RETR"
OPTS_s = 1 << 5, // sendmail: subject
OPTF_z = 1 << 5, // fetchmail: delete from server
OPTS_c = 1 << 6, // sendmail: assumed charset
OPTS_t = 1 << 7, // sendmail: recipient(s)
};
const char *options;
unsigned 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 = "-2:w+:t:t::"; // count(-t) > 0
options = "w:U:P:X" "ns:c:t:";
} else {
// FETCHMAIL
opt_after_connect = NULL;
opt_complementary = "-2:w+:P";
options = "w:U:P:X" "tz";
}
opts = getopt32(argv, options,
&timeout, &opt_user, &opt_pass,
&opt_subject, &opt_charset, &opt_recipients
);
//argc -= optind;
argv += optind;
// first argument is remote server[:port]
opt_connect = *argv++;
// connect to server
// SSL ordered? ->
if (opts & OPT_X) {
// ... 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);
}
#if ENABLE_FETCHMAIL
// we are sendmail?
if (opt_after_connect)
#endif
{
/***************************************************
* SENDMAIL
***************************************************/
char *opt_from;
int code;
char *boundary;
const char *fmt;
const char *p;
char *q;
// we didn't use SSL helper? ->
if (!(opts & OPT_X)) {
// ... wait for initial server OK
smtp_check(NULL, 220);
}
// get the sender
opt_from = sane(*argv++);
// introduce to server
// we should start with modern EHLO
if (250 != smtp_checkp("EHLO %s", 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 = (opts & OPT_P) ? -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 (!(opts & OPT_U)) {
// no! fetch it from "from" option
//opts |= OPT_U;
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 (llist_t *to = opt_recipients; to; to = to->link) {
smtp_checkp("RCPT TO:<%s>", sane(to->data), 250);
}
// enter "put message" mode
smtp_check("DATA", 354);
// put address headers
printf("From: %s\r\n", opt_from);
for (llist_t *to = opt_recipients; to; to = to->link) {
printf("To: %s\r\n", to->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 *)"";
while (*argv) {
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(*argv, NULL);
if (*(++argv))
q = bb_get_last_path_component_strip(*argv);
}
// 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
} else {
/***************************************************
* FETCHMAIL
***************************************************/
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 (!(opts & OPT_U)) {
//opts |= OPT_U;
// N.B. IMHO getenv("USER") can be way easily spoofed!
opt_user = bb_getpwuid(NULL, -1, getuid());
}
// get server greeting
pop3_checkr(NULL, NULL, &buf);
// server supports APOP?
if ('<' == *buf) {
md5_ctx_t md5;
// yes! compose <stamp><password>
char *s = strchr(buf, '>');
if (s)
strcpy(s+1, opt_pass);
s = buf;
// get md5 sum of <stamp><password>
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(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(), pid, hostname);
char *target;
int rc;
// retrieve message in ./tmp/
pop3_check(retr, (const char *)nmsg);
pop3_message(filename);
// delete message from server
if (opts & OPTF_z)
pop3_check("DELE %u", (const char*)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;
}