summaryrefslogtreecommitdiff
path: root/mailutils/sendmail.c
blob: 014b20dc8df25841826b9e28c669aca9b85ac620 (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
/* 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"
#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)
{
	char *opt_connect = opt_connect;
	char *opt_from;
	char *s;
	llist_t *list = NULL;
	char *domain = sane_address(safe_getdomainname());
	int code;

	enum {
	//--- standard options
		OPT_t = 1 << 0,         // read message for recipients, append them to those on cmdline
		OPT_f = 1 << 1,         // sender address
		OPT_o = 1 << 2,         // various options. -oi IMPLIED! others are IGNORED!
		OPT_i = 1 << 3,         // IMPLIED!
	//--- BB specific options
		OPT_w = 1 << 4,         // network timeout
		OPT_H = 1 << 5,         // use external connection helper
		OPT_S = 1 << 6,         // specify connection string
		OPT_a = 1 << 7,         // authentication tokens
	};

	// init global variables
	INIT_G();

	// save initial stdin since body is piped!
	xdup2(STDIN_FILENO, 3);
	G.fp0 = fdopen(3, "r");

	// parse options
	// -f is required. -H and -S are mutually exclusive
	opt_complementary = "f:w+:H--S:S--H:a::";
	// N.B. since -H and -S are mutually exclusive they do not interfere in opt_connect
	// -a is for ssmtp (http://downloads.openwrt.org/people/nico/man/man8/ssmtp.8.html) compatibility,
	// it is still under development.
	opts = getopt32(argv, "tf:o:iw:H:S:a::", &opt_from, NULL, &timeout, &opt_connect, &opt_connect, &list);
	//argc -= optind;
	argv += optind;

	// process -a[upm]<token> options
	if ((opts & OPT_a) && !list)
		bb_show_usage();
	while (list) {
		char *a = (char *) llist_pop(&list);
		if ('u' == a[0])
			G.user = xstrdup(a+1);
		if ('p' == a[0])
			G.pass = xstrdup(a+1);
		// N.B. we support only AUTH LOGIN so far
		//if ('m' == a[0])
		//	G.method = xstrdup(a+1);
	}
	// N.B. list == NULL here
	//bb_info_msg("OPT[%x] AU[%s], AP[%s], AM[%s], ARGV[%s]", opts, au, ap, am, *argv);

	// connect to server

	// connection helper ordered? ->
	if (opts & OPT_H) {
		const char *args[] = { "sh", "-c", opt_connect, NULL };
		// plug it in
		launch_helper(args);
	// vanilla connection
	} else {
		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 kick 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);
	}
	if (ENABLE_FEATURE_CLEAN_UP)
		free(domain);

	// perform authentication
	if (opts & OPT_a) {
		smtp_check("AUTH LOGIN", 334);
		// we must read credentials unless they are given via -a[up] options
		if (!G.user || !G.pass)
			get_cred_or_die(4);
		encode_base64(NULL, G.user, NULL);
		smtp_check("", 334);
		encode_base64(NULL, G.pass, NULL);
		smtp_check("", 235);
	}

	// 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
	// N.B. we marked -f as required option!
	//if (!G.user) {
	//	// 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);
	smtp_checkp("MAIL FROM:<%s>", opt_from, 250);

	// process message

	// read recipients from message and add them to those given on cmdline.
	// this means we scan stdin for To:, Cc:, Bcc: lines until an empty line
	// and then use the rest of stdin as message body
	code = 0; // set "analyze headers" mode
	while ((s = xmalloc_fgetline(G.fp0)) != NULL) {
		// put message lines doubling leading dots
		if (code) {
			// 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);
			free(s);
			continue;
		}

		// analyze headers
		// To: or Cc: headers add recipients
		if (0 == strncasecmp("To: ", s, 4) || 0 == strncasecmp("Bcc: " + 1, s, 4)) {
			rcptto(sane_address(s+4));
//			goto addh;
			llist_add_to_end(&list, s);
		// Bcc: header adds blind copy (hidden) recipient
		} else if (0 == strncasecmp("Bcc: ", s, 5)) {
			rcptto(sane_address(s+5));
			free(s);
			// N.B. Bcc: vanishes from headers!
		// other headers go verbatim
		} else if (s[0]) {
// addh:
			llist_add_to_end(&list, s);
		// the empty line stops analyzing headers
		} else {
			free(s);
			// put recipients specified on cmdline
			while (*argv) {
				s = sane_address(*argv);
				rcptto(s);
				llist_add_to_end(&list, xasprintf("To: %s", s));
				argv++;
			}
			// enter "put message" mode
			smtp_check("DATA", 354);
			// dump the headers
			while (list) {
				printf("%s\r\n", (char *) llist_pop(&list));
			}
			printf("%s\r\n" + 2); // quirk for format string to be reused
			// stop analyzing headers
			code++;
		}
	}

	// finalize the message
	smtp_check(".", 250);
	// ... and say goodbye
	smtp_check("QUIT", 221);
	// cleanup
	if (ENABLE_FEATURE_CLEAN_UP)
		fclose(G.fp0);

	return EXIT_SUCCESS;
}