aboutsummaryrefslogtreecommitdiff
path: root/networking/sendmail.c
blob: 63305d1492f73d3484397413f96fa61df68cf5a4 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
/* 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;
	} else {
		len = strlen(text);
	}

	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);
}

static pid_t helper_pid;

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)
{
	int err;

	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))
#if ENABLE_FEATURE_SENDMAIL_BLOATY
			bb_error_msg_and_die("child exited (%d)", WEXITSTATUS(err));
#else
			bb_error_msg_and_die("child failed");
#endif
}

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[0], (char **)argv);
		_exit(127);
	}
	// parent - check whether child is alive
	sig_catch(SIGCHLD, signal_handler);
	sig_catch(SIGALRM, signal_handler);
	signal_handler(SIGCHLD);
	// child seems OK -> parent goes on
}

static unsigned timeout;

static char *command(const char *fmt, const char *param)
{
	char *msg = (char *)fmt;
	alarm(timeout);
	if (msg) {
//		if (param)
			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;
	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
#if ENABLE_FEATURE_SENDMAIL_EHLO
	while ((answer = xmalloc_getline(stdin)) && '-' == answer[3]) ;
#else
	answer = xmalloc_getline(stdin);
#endif
	if (answer) {
		int n = atoi(answer);
		alarm(0);
		if (ENABLE_FEATURE_CLEAN_UP) {
			free(msg);
			free(answer);
		}
		if (-1 == code || n == code) {
			return n;
		}
	}
	kill_helper();
	bb_error_msg_and_die("%s failed", msg);
}

static int smtp_check(const char *fmt, int code)
{
	return smtp_checkp(fmt, NULL, code);
}

static void pop3_checkr(const char *fmt, const char *param, char **ret)
{
	char *msg = command(fmt, param);
	char *answer = xmalloc_getline(stdin);
	if (answer && '+' == answer[0]) {
		alarm(0);
		if (ret)
			*ret = answer;
		else
			free(answer);
		return;
	}
	kill_helper();
	bb_error_msg_and_die("%s failed", msg);
}

static void pop3_check(const char *fmt, const char *param)
{
	pop3_checkr(fmt, param, NULL);
}

// 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;
}

static void pop3_message(int fd)
{
	char *answer;
	// read stdin, copy to file fd
	while ((answer = xmalloc_fgets_str(stdin, "\r\n"))) {
		char *s = answer;
		if ('.' == answer[0]) {
			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);
}

static const char *args[] = {
	"openssl", "s_client", "-quiet", "-connect", NULL, "-tls1", "-starttls", "smtp", NULL
};
#define opt_connect	args[4]
#define opt_after_connect args[5]

int sendgetmail_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int sendgetmail_main(int argc, char **argv)
{
	llist_t *recipients = NULL;
	char *from;
	const char *subject;
	char *charset = (char *)"utf-8";

	const char *opt_user;
	const char *opt_pass;
	const char *opt_timeout;
	const char *opt_chdir;

	enum {
		OPT_C = 1 << 0,         // chdir
		OPT_w = 1 << 1,         // network timeout
		OPT_U = 1 << 2,         // user
		OPT_P = 1 << 3,         // password
		OPT_X = 1 << 4,         // use openssl connection helper

		OPTS_t = 1 << 5,        // sendmail "to"
		OPTF_t = 1 << 5,        // fetchmail "TOP"

		OPTS_f = 1 << 6,        // sendmail "from"
		OPTF_z = 1 << 6,        // fetchmail "delete"

		OPTS_n = 1 << 7,        // notification
		OPTS_s = 1 << 8,        // subject given
		OPTS_c = 1 << 9,        // charset for subject and body
	};

	const char *options;
	unsigned opts;

	// SENDMAIL
	if ('s' == applet_name[0]) {
		// save initial stdin
		xdup2(STDIN_FILENO, INITIAL_STDIN_FILENO);
		// -f must be specified
		// -t may be multiple
		opt_complementary = "-1:f:t::";
		options = "C:w:U:P:X" "t:f:ns:c:";
	// FETCHMAIL
	} else {
		opt_after_connect = NULL;
		opt_complementary = "=1:P";
		options = "C:w:U:P:X" "tz";
	}
	opts = getopt32(argv, options,
		&opt_chdir, &opt_timeout, &opt_user, &opt_pass,
		&recipients, &from, &subject, &charset
	);

	//argc -= optind;
	argv += optind;

	// first argument is remote server[:port]
	opt_connect = *argv++;

	if (opts & OPT_w)
		timeout = xatou(opt_timeout);

	// chdir
	if (opts & OPT_C)
		xchdir(opt_chdir);

	// connect to server
	if (opts & OPT_X) {
		launch_helper(args);
	} else {
		// no connection helper provided -> make plain connect
		int fd = create_and_connect_stream_or_die(opt_connect, 0);
		xmove_fd(fd, STDIN_FILENO);
		xdup2(STDIN_FILENO, STDOUT_FILENO);
	}

	// randomize
	srand(time(NULL));

	// SENDMAIL
	if (recipients) {
		int code;
		char *boundary;

		// wait for initial OK on plain connect
		if (!(opts & OPT_X))
			smtp_check(NULL, 220);

		sane(from);
		// introduce to server
		// should we respect modern (but useless here) EHLO?
		// or should they respect we wanna be tiny?!
		if (!ENABLE_FEATURE_SENDMAIL_EHLO || 250 != smtp_checkp("EHLO %s", from, -1)) {
			smtp_checkp("HELO %s", from, 250);
		}

		// set sender
		// NOTE: if password has not been specified ->
		// no authentication is possible
		code = (opts & OPT_P) ? -1 : 250;
		// first try softly without authentication
		while (250 != smtp_checkp("MAIL FROM:<%s>", from, code)) {
			// MAIL FROM failed -> authentication needed
			// do we have username?
			if (!(opts & OPT_U)) {
				// no! fetch it from "from" option
				//opts |= OPT_U;
				opt_user = xstrdup(from);
				*strchrnul(opt_user, '@') = '\0';
			}
			// now it seems we have username
			// 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 -> retry set sender
			// but now die on failure
			code = 250;
		}
		// set recipients
		for (llist_t *to = recipients; to; to = to->link) {
			smtp_checkp("RCPT TO:<%s>", sane(to->data), 250);
		}

		// now put message
		smtp_check("DATA", 354);
		// put address headers
		printf("From: %s\r\n", from);
		for (llist_t *to = recipients; to; to = to->link) {
			printf("To: %s\r\n", to->data);
		}
		// put encoded subject
		if (opts & OPTS_c)
			sane(charset);
		if (opts & OPTS_s) {
			printf("Subject: =?%s?B?", charset);
			uuencode(NULL, subject);
			printf("?=\r\n");
		}
		// put notification
		if (opts & OPTS_n)
			printf("Disposition-Notification-To: %s\r\n", from);
		// put common headers and body start
		boundary = xasprintf("%d-%d-%d", rand(), rand(), rand());
		printf(
			USE_FEATURE_SENDMAIL_BLOATY("X-Mailer: busybox " BB_VER " sendmail\r\n")
			"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)
	{
		const char *fmt =
			"\r\n--%s\r\n"
			"%stext/plain; charset=%s\r\n"
			"%s%s\r\n"
			"%s"
		;
		const char *p = charset;
		char *q = (char *)"";
		while (argv[0]) {
			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[0]);
		}
	}
		// put terminator
		printf("\r\n--%s--\r\n" "\r\n", boundary);
		if (ENABLE_FEATURE_CLEAN_UP)
			free(boundary);

		// end message and say goodbye
		smtp_check(".", 250);
		smtp_check("QUIT", 221);

	// FETCHMAIL
	} else {
		// authenticate
		char *buf;
		unsigned nmsg;
		if (!(opts & OPT_U)) {
			//opts |= OPT_U;
			opt_user = getenv("USER");
		}
#if ENABLE_FEATURE_FETCHMAIL_APOP
		pop3_checkr(NULL, NULL, &buf);
		// server supports APOP?
		if ('<' == buf[4]) {
			md5_ctx_t md5;
			uint8_t hex[16*2 + 1];
			// yes. compose <stamp><password>
			char *s = strchr(buf, '>');
			if (s)
				strcpy(s+1, opt_pass);
			s = buf+4;
			// get md5 sum of <stamp><password>
			md5_begin(&md5);
			md5_hash(s, strlen(s), &md5);
			md5_end(s, &md5);
			bin2hex(hex, s, 16);
			// APOP
			s = xasprintf("%s %s", opt_user, hex);
			pop3_check("APOP %s", s);
			if (ENABLE_FEATURE_CLEAN_UP) {
				free(s);
				free(buf);
			}
		} else {
#else
		{
			pop3_check(NULL, NULL);
#endif
			// USER
			pop3_check("USER %s", opt_user);
			// PASS
			pop3_check("PASS %s", opt_pass);
		}

		// get statistics
		pop3_checkr("STAT", NULL, &buf);

		// get number of messages
		nmsg = atoi(buf+4);
		if (ENABLE_FEATURE_CLEAN_UP)
			free(buf);

		// lock maildir
		////USE_FEATURE_CLEAN_UP(close)(xopen(".lock", O_CREAT | O_WRONLY | O_TRUNC | O_EXCL));
		
		// make tempnam(dir, salt) respect dir argument
		unsetenv("TMPDIR");

		// TODO: piping through external filter argv... if *argv

		// cache fetch command
	{
		const char *retr = (opts & OPTF_t) ? "TOP %u 0" : "RETR %u";
		// loop through messages
		for (; nmsg; nmsg--) {
			int fd;
			char tmp_name[sizeof("tmp/XXXXXX")];
			char new_name[sizeof("new/XXXXXX")];

			// retrieve message in ./tmp
			strcpy(tmp_name, "tmp/XXXXXX");
			fd = mkstemp(tmp_name);
			if (fd < 0)
				bb_perror_msg_and_die("cannot create unique file");
			pop3_check(retr, (const char *)nmsg);
			pop3_message(fd); // NB: closes fd

			// move file to ./new atomically
			strncpy(new_name, "new", 3);
			strcpy(new_name + 3, tmp_name + 3);
			if (rename(tmp_name, new_name) < 0) {
				// rats! such file exists! try to make unique name
				strcpy(new_name + 3, "tmp/XXXXXX" + 3);
				fd = mkstemp(new_name);
				if (fd < 0)
					bb_perror_msg_and_die("cannot create unique file");
				close(fd);
				if (rename(tmp_name, new_name) < 0) {
					// something is very wrong
					bb_perror_msg_and_die("cannot move %s to %s", tmp_name, new_name);
				}
			}

			// delete message from server
			if (opts & OPTF_z)
				pop3_check("DELE %u", (const char*)nmsg);
		}
	}

		// Bye
		pop3_check("QUIT", NULL);

		// unlock maildir
		////unlink(".lock");
	}

	return 0;
}