1 | /* vi: set sw=4 ts=4: */
|
---|
2 | /*
|
---|
3 | * bare bones sendmail
|
---|
4 | *
|
---|
5 | * Copyright (C) 2008 by Vladimir Dronnikov <dronnikov@gmail.com>
|
---|
6 | *
|
---|
7 | * Licensed under GPLv2, see file LICENSE in this source tree.
|
---|
8 | */
|
---|
9 | #include "libbb.h"
|
---|
10 | #include "mail.h"
|
---|
11 |
|
---|
12 | // limit maximum allowed number of headers to prevent overflows.
|
---|
13 | // set to 0 to not limit
|
---|
14 | #define MAX_HEADERS 256
|
---|
15 |
|
---|
16 | static int smtp_checkp(const char *fmt, const char *param, int code)
|
---|
17 | {
|
---|
18 | char *answer;
|
---|
19 | const char *msg = command(fmt, param);
|
---|
20 | // read stdin
|
---|
21 | // if the string has a form \d\d\d- -- read next string. E.g. EHLO response
|
---|
22 | // parse first bytes to a number
|
---|
23 | // if code = -1 then just return this number
|
---|
24 | // if code != -1 then checks whether the number equals the code
|
---|
25 | // if not equal -> die saying msg
|
---|
26 | while ((answer = xmalloc_fgetline(stdin)) != NULL)
|
---|
27 | if (strlen(answer) <= 3 || '-' != answer[3])
|
---|
28 | break;
|
---|
29 | if (answer) {
|
---|
30 | int n = atoi(answer);
|
---|
31 | if (timeout)
|
---|
32 | alarm(0);
|
---|
33 | free(answer);
|
---|
34 | if (-1 == code || n == code)
|
---|
35 | return n;
|
---|
36 | }
|
---|
37 | bb_error_msg_and_die("%s failed", msg);
|
---|
38 | }
|
---|
39 |
|
---|
40 | static int smtp_check(const char *fmt, int code)
|
---|
41 | {
|
---|
42 | return smtp_checkp(fmt, NULL, code);
|
---|
43 | }
|
---|
44 |
|
---|
45 | // strip argument of bad chars
|
---|
46 | static char *sane_address(char *str)
|
---|
47 | {
|
---|
48 | char *s = str;
|
---|
49 | char *p = s;
|
---|
50 | while (*s) {
|
---|
51 | if (isalnum(*s) || '_' == *s || '-' == *s || '.' == *s || '@' == *s) {
|
---|
52 | *p++ = *s;
|
---|
53 | }
|
---|
54 | s++;
|
---|
55 | }
|
---|
56 | *p = '\0';
|
---|
57 | return str;
|
---|
58 | }
|
---|
59 |
|
---|
60 | static void rcptto(const char *s)
|
---|
61 | {
|
---|
62 | // N.B. we don't die if recipient is rejected, for the other recipients may be accepted
|
---|
63 | if (250 != smtp_checkp("RCPT TO:<%s>", s, -1))
|
---|
64 | bb_error_msg("Bad recipient: <%s>", s);
|
---|
65 | }
|
---|
66 |
|
---|
67 | int sendmail_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
|
---|
68 | int sendmail_main(int argc UNUSED_PARAM, char **argv)
|
---|
69 | {
|
---|
70 | char *opt_connect = opt_connect;
|
---|
71 | char *opt_from;
|
---|
72 | char *s;
|
---|
73 | llist_t *list = NULL;
|
---|
74 | char *domain = sane_address(safe_getdomainname());
|
---|
75 | unsigned nheaders = 0;
|
---|
76 | int code;
|
---|
77 |
|
---|
78 | enum {
|
---|
79 | //--- standard options
|
---|
80 | OPT_t = 1 << 0, // read message for recipients, append them to those on cmdline
|
---|
81 | OPT_f = 1 << 1, // sender address
|
---|
82 | OPT_o = 1 << 2, // various options. -oi IMPLIED! others are IGNORED!
|
---|
83 | OPT_i = 1 << 3, // IMPLIED!
|
---|
84 | //--- BB specific options
|
---|
85 | OPT_w = 1 << 4, // network timeout
|
---|
86 | OPT_H = 1 << 5, // use external connection helper
|
---|
87 | OPT_S = 1 << 6, // specify connection string
|
---|
88 | OPT_a = 1 << 7, // authentication tokens
|
---|
89 | };
|
---|
90 |
|
---|
91 | // init global variables
|
---|
92 | INIT_G();
|
---|
93 |
|
---|
94 | // save initial stdin since body is piped!
|
---|
95 | xdup2(STDIN_FILENO, 3);
|
---|
96 | G.fp0 = xfdopen_for_read(3);
|
---|
97 |
|
---|
98 | // parse options
|
---|
99 | // -f is required. -H and -S are mutually exclusive
|
---|
100 | opt_complementary = "f:w+:H--S:S--H:a::";
|
---|
101 | // N.B. since -H and -S are mutually exclusive they do not interfere in opt_connect
|
---|
102 | // -a is for ssmtp (http://downloads.openwrt.org/people/nico/man/man8/ssmtp.8.html) compatibility,
|
---|
103 | // it is still under development.
|
---|
104 | opts = getopt32(argv, "tf:o:iw:H:S:a::", &opt_from, NULL, &timeout, &opt_connect, &opt_connect, &list);
|
---|
105 | //argc -= optind;
|
---|
106 | argv += optind;
|
---|
107 |
|
---|
108 | // process -a[upm]<token> options
|
---|
109 | if ((opts & OPT_a) && !list)
|
---|
110 | bb_show_usage();
|
---|
111 | while (list) {
|
---|
112 | char *a = (char *) llist_pop(&list);
|
---|
113 | if ('u' == a[0])
|
---|
114 | G.user = xstrdup(a+1);
|
---|
115 | if ('p' == a[0])
|
---|
116 | G.pass = xstrdup(a+1);
|
---|
117 | // N.B. we support only AUTH LOGIN so far
|
---|
118 | //if ('m' == a[0])
|
---|
119 | // G.method = xstrdup(a+1);
|
---|
120 | }
|
---|
121 | // N.B. list == NULL here
|
---|
122 | //bb_info_msg("OPT[%x] AU[%s], AP[%s], AM[%s], ARGV[%s]", opts, au, ap, am, *argv);
|
---|
123 |
|
---|
124 | // connect to server
|
---|
125 |
|
---|
126 | // connection helper ordered? ->
|
---|
127 | if (opts & OPT_H) {
|
---|
128 | const char *args[] = { "sh", "-c", opt_connect, NULL };
|
---|
129 | // plug it in
|
---|
130 | launch_helper(args);
|
---|
131 | // vanilla connection
|
---|
132 | } else {
|
---|
133 | int fd;
|
---|
134 | // host[:port] not explicitly specified? -> use $SMTPHOST
|
---|
135 | // no $SMTPHOST ? -> use localhost
|
---|
136 | if (!(opts & OPT_S)) {
|
---|
137 | opt_connect = getenv("SMTPHOST");
|
---|
138 | if (!opt_connect)
|
---|
139 | opt_connect = (char *)"127.0.0.1";
|
---|
140 | }
|
---|
141 | // do connect
|
---|
142 | fd = create_and_connect_stream_or_die(opt_connect, 25);
|
---|
143 | // and make ourselves a simple IO filter
|
---|
144 | xmove_fd(fd, STDIN_FILENO);
|
---|
145 | xdup2(STDIN_FILENO, STDOUT_FILENO);
|
---|
146 | }
|
---|
147 | // N.B. from now we know nothing about network :)
|
---|
148 |
|
---|
149 | // wait for initial server OK
|
---|
150 | // N.B. if we used openssl the initial 220 answer is already swallowed during openssl TLS init procedure
|
---|
151 | // so we need to kick the server to see whether we are ok
|
---|
152 | code = smtp_check("NOOP", -1);
|
---|
153 | // 220 on plain connection, 250 on openssl-helped TLS session
|
---|
154 | if (220 == code)
|
---|
155 | smtp_check(NULL, 250); // reread the code to stay in sync
|
---|
156 | else if (250 != code)
|
---|
157 | bb_error_msg_and_die("INIT failed");
|
---|
158 |
|
---|
159 | // we should start with modern EHLO
|
---|
160 | if (250 != smtp_checkp("EHLO %s", domain, -1)) {
|
---|
161 | smtp_checkp("HELO %s", domain, 250);
|
---|
162 | }
|
---|
163 | if (ENABLE_FEATURE_CLEAN_UP)
|
---|
164 | free(domain);
|
---|
165 |
|
---|
166 | // perform authentication
|
---|
167 | if (opts & OPT_a) {
|
---|
168 | smtp_check("AUTH LOGIN", 334);
|
---|
169 | // we must read credentials unless they are given via -a[up] options
|
---|
170 | if (!G.user || !G.pass)
|
---|
171 | get_cred_or_die(4);
|
---|
172 | encode_base64(NULL, G.user, NULL);
|
---|
173 | smtp_check("", 334);
|
---|
174 | encode_base64(NULL, G.pass, NULL);
|
---|
175 | smtp_check("", 235);
|
---|
176 | }
|
---|
177 |
|
---|
178 | // set sender
|
---|
179 | // N.B. we have here a very loosely defined algotythm
|
---|
180 | // since sendmail historically offers no means to specify secrets on cmdline.
|
---|
181 | // 1) server can require no authentication ->
|
---|
182 | // we must just provide a (possibly fake) reply address.
|
---|
183 | // 2) server can require AUTH ->
|
---|
184 | // we must provide valid username and password along with a (possibly fake) reply address.
|
---|
185 | // For the sake of security username and password are to be read either from console or from a secured file.
|
---|
186 | // Since reading from console may defeat usability, the solution is either to read from a predefined
|
---|
187 | // file descriptor (e.g. 4), or again from a secured file.
|
---|
188 |
|
---|
189 | // got no sender address? -> use system username as a resort
|
---|
190 | // N.B. we marked -f as required option!
|
---|
191 | //if (!G.user) {
|
---|
192 | // // N.B. IMHO getenv("USER") can be way easily spoofed!
|
---|
193 | // G.user = xuid2uname(getuid());
|
---|
194 | // opt_from = xasprintf("%s@%s", G.user, domain);
|
---|
195 | //}
|
---|
196 | //if (ENABLE_FEATURE_CLEAN_UP)
|
---|
197 | // free(domain);
|
---|
198 | smtp_checkp("MAIL FROM:<%s>", opt_from, 250);
|
---|
199 |
|
---|
200 | // process message
|
---|
201 |
|
---|
202 | // read recipients from message and add them to those given on cmdline.
|
---|
203 | // this means we scan stdin for To:, Cc:, Bcc: lines until an empty line
|
---|
204 | // and then use the rest of stdin as message body
|
---|
205 | code = 0; // set "analyze headers" mode
|
---|
206 | while ((s = xmalloc_fgetline(G.fp0)) != NULL) {
|
---|
207 | dump:
|
---|
208 | // put message lines doubling leading dots
|
---|
209 | if (code) {
|
---|
210 | // escape leading dots
|
---|
211 | // N.B. this feature is implied even if no -i (-oi) switch given
|
---|
212 | // N.B. we need to escape the leading dot regardless of
|
---|
213 | // whether it is single or not character on the line
|
---|
214 | if ('.' == s[0] /*&& '\0' == s[1] */)
|
---|
215 | printf(".");
|
---|
216 | // dump read line
|
---|
217 | printf("%s\r\n", s);
|
---|
218 | free(s);
|
---|
219 | continue;
|
---|
220 | }
|
---|
221 |
|
---|
222 | // analyze headers
|
---|
223 | // To: or Cc: headers add recipients
|
---|
224 | if (0 == strncasecmp("To:", s, 3) || 0 == strncasecmp("Bcc:" + 1, s, 3)) {
|
---|
225 | rcptto(sane_address(s+3));
|
---|
226 | goto addheader;
|
---|
227 | // Bcc: header adds blind copy (hidden) recipient
|
---|
228 | } else if (0 == strncasecmp("Bcc:", s, 4)) {
|
---|
229 | rcptto(sane_address(s+4));
|
---|
230 | free(s);
|
---|
231 | // N.B. Bcc: vanishes from headers!
|
---|
232 |
|
---|
233 | // other headers go verbatim
|
---|
234 |
|
---|
235 | // N.B. RFC2822 2.2.3 "Long Header Fields" allows for headers to occupy several lines.
|
---|
236 | // Continuation is denoted by prefixing additional lines with whitespace(s).
|
---|
237 | // Thanks (stefan.seyfried at googlemail.com) for pointing this out.
|
---|
238 | } else if (strchr(s, ':') || (list && skip_whitespace(s) != s)) {
|
---|
239 | addheader:
|
---|
240 | // N.B. we allow MAX_HEADERS generic headers at most to prevent attacks
|
---|
241 | if (MAX_HEADERS && ++nheaders >= MAX_HEADERS)
|
---|
242 | goto bail;
|
---|
243 | llist_add_to_end(&list, s);
|
---|
244 | // a line without ":" (an empty line too, by definition) doesn't look like a valid header
|
---|
245 | // so stop "analyze headers" mode
|
---|
246 | } else {
|
---|
247 | reenter:
|
---|
248 | // put recipients specified on cmdline
|
---|
249 | while (*argv) {
|
---|
250 | char *t = sane_address(*argv);
|
---|
251 | rcptto(t);
|
---|
252 | //if (MAX_HEADERS && ++nheaders >= MAX_HEADERS)
|
---|
253 | // goto bail;
|
---|
254 | llist_add_to_end(&list, xasprintf("To: %s", t));
|
---|
255 | argv++;
|
---|
256 | }
|
---|
257 | // enter "put message" mode
|
---|
258 | // N.B. DATA fails iff no recipients were accepted (or even provided)
|
---|
259 | // in this case just bail out gracefully
|
---|
260 | if (354 != smtp_check("DATA", -1))
|
---|
261 | goto bail;
|
---|
262 | // dump the headers
|
---|
263 | while (list) {
|
---|
264 | printf("%s\r\n", (char *) llist_pop(&list));
|
---|
265 | }
|
---|
266 | // stop analyzing headers
|
---|
267 | code++;
|
---|
268 | // N.B. !s means: we read nothing, and nothing to be read in the future.
|
---|
269 | // just dump empty line and break the loop
|
---|
270 | if (!s) {
|
---|
271 | puts("\r");
|
---|
272 | break;
|
---|
273 | }
|
---|
274 | // go dump message body
|
---|
275 | // N.B. "s" already contains the first non-header line, so pretend we read it from input
|
---|
276 | goto dump;
|
---|
277 | }
|
---|
278 | }
|
---|
279 | // odd case: we didn't stop "analyze headers" mode -> message body is empty. Reenter the loop
|
---|
280 | // N.B. after reenter code will be > 0
|
---|
281 | if (!code)
|
---|
282 | goto reenter;
|
---|
283 |
|
---|
284 | // finalize the message
|
---|
285 | smtp_check(".", 250);
|
---|
286 | bail:
|
---|
287 | // ... and say goodbye
|
---|
288 | smtp_check("QUIT", 221);
|
---|
289 | // cleanup
|
---|
290 | if (ENABLE_FEATURE_CLEAN_UP)
|
---|
291 | fclose(G.fp0);
|
---|
292 |
|
---|
293 | return EXIT_SUCCESS;
|
---|
294 | }
|
---|