busybox/networking/sendmail.c
2008-09-28 13:50:57 +00:00

556 lines
14 KiB
C

/* vi: set sw=4 ts=4: */
/*
* bare bones sendmail
*
* Copyright (C) 2008 by Vladimir Dronnikov <dronnikov@gmail.com>
*
* Licensed under GPLv2, see file LICENSE in this tarball for details.
*/
#include "libbb.h"
struct globals {
pid_t helper_pid;
unsigned timeout;
FILE *fp0; // initial stdin
// arguments for SSL connection helper
const char *xargs[9];
};
#define G (*ptr_to_globals)
#define helper_pid (G.helper_pid)
#define timeout (G.timeout )
#define fp0 (G.fp0 )
#define xargs (G.xargs )
#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"; \
} while (0)
#define opt_connect (xargs[4])
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
FILE *fp = fp;
ssize_t len = len;
char dst_buf[DST_BUF_SIZE + 1];
if (fname) {
fp = (NOT_LONE_DASH(fname)) ? xfopen_for_read(fname) : fp0;
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;
while (1) {
size_t size;
if (fname) {
size = fread((char *)src_buf, 1, SRC_BUF_SIZE, fp);
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) {
printf("\r\n");
} else {
src_buf += size;
len -= size;
}
fwrite(dst_buf, 1, 4 * ((size + 2) / 3), stdout);
}
if (fname)
fclose(fp);
#undef src_buf
}
#if ENABLE_FEATURE_SENDMAIL_SSL
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)) {
// if (WEXITSTATUS(err))
bb_error_msg_and_die("child exited (%d)", WEXITSTATUS(err));
// else
// kill(0, SIGCONT);
}
#undef 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
}
#else
#define kill_helper() ((void)0)
#define launch_helper(x) bb_error_msg_and_die("no SSL support")
#endif
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);
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;
}
// NB: parse_url can modify url[] (despite const), but only if '@' is there
static const char *parse_url(const char *url, const char **user, const 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;
}
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;
const char *opt_charset = CONFIG_FEATURE_SENDMAIL_CHARSET;
#if ENABLE_FEATURE_SENDMAIL_MAILXX
llist_t *opt_carboncopies = NULL;
char *opt_errors_to;
#endif
#endif
char *opt_from, *opt_fullname;
const char *opt_user;
const char *opt_pass;
int code;
char *boundary;
llist_t *l;
llist_t *headers = NULL;
char *domain = sane(safe_getdomainname());
unsigned opts;
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
OPT_t = 1 << 3, // read message for recipients
OPT_N = 1 << 4, // request notification
OPT_f = 1 << 5, // sender address
OPT_F = 1 << 6, // sender name, overrides $NAME
OPT_s = 1 << 7, // subject
OPT_j = 1 << 8, // assumed charset
OPT_a = 1 << 9, // attachment(s)
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);
fp0 = fdopen(3, "r");
// parse options
opt_complementary = "w+:a::" USE_FEATURE_SENDMAIL_MAILXX("c::");
opts = getopt32(argv,
"w:H:St" "N:f:F:" USE_FEATURE_SENDMAIL_MAILX("s:j:a:") 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 */, &opt_connect /* -H */,
NULL, &opt_from, &opt_fullname,
USE_FEATURE_SENDMAIL_MAILX(&opt_subject, &opt_charset, &opt_attachments,)
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
// host[:port] not specified ? -> use $SMTPHOST. no $SMTPHOST ? -> use localhost
if (!(opts & OPT_H)) {
opt_connect = getenv("SMTPHOST");
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(opt_connect, &opt_user, &opt_pass);
// username must be defined!
if (!opt_user) {
// N.B. IMHO getenv("USER") can be way easily spoofed!
opt_user = bb_getpwuid(NULL, -1, getuid());
}
// 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);
}
// got no sender address? -> use username as a resort
if (!(opts & OPT_f)) {
opt_from = xasprintf("%s@%s", opt_user, domain);
}
// introduce to server
// we didn't use SSL helper? ->
if (!(opts & OPT_S)) {
// ... wait for initial server OK
smtp_check(NULL, 220);
}
// we should start with modern EHLO
if (250 != smtp_checkp("EHLO %s", domain, -1)) {
smtp_checkp("HELO %s", domain, 250);
}
if (ENABLE_FEATURE_CLEAN_UP)
free(domain);
// 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
if (334 == smtp_check("AUTH LOGIN", -1)) {
uuencode(NULL, opt_user); // opt_user != NULL
smtp_check("", 334);
uuencode(NULL, opt_pass);
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(*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(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(fp0)) != NULL) {
if (0 == strncasecmp("To: ", s, 4) || 0 == strncasecmp("Cc: ", s, 4)) {
rcptto(sane(s+4));
llist_add_to_end(&headers, s);
} else if (0 == strncasecmp("Bcc: ", s, 5)) {
rcptto(sane(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 (opts & OPT_j)
sane((char *)opt_charset);
if (opts & OPT_s) {
printf("Subject: ");
if (opts & OPT_j) {
printf("=?%s?B?", opt_charset);
uuencode(NULL, opt_subject);
printf("?=");
} else {
printf("%s", opt_subject);
}
printf("\r\n");
}
// 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 = 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);
// no attachments? -> just dump message
} else
#endif
{
char *s;
// terminate headers
printf("\r\n");
// put plain text respecting leading dots
while ((s = xmalloc_fgetline(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(fp0);
return EXIT_SUCCESS;
}