source: branches/3.0/mindi-busybox/mailutils/sendmail.c @ 3085

Last change on this file since 3085 was 2725, checked in by bruno, 8 years ago
  • Update mindi-busybox to 1.18.3 to avoid problems with the tar command which is now failing on recent versions with busybox 1.7.3
  • Property svn:eol-style set to native
File size: 8.9 KB
Line 
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
16static 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
40static int smtp_check(const char *fmt, int code)
41{
42    return smtp_checkp(fmt, NULL, code);
43}
44
45// strip argument of bad chars
46static 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
60static 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
67int sendmail_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
68int 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}
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