[2725] | 1 | /* vi: set sw=4 ts=4: */
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| 2 | /*
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| 3 | * bare bones sendmail
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| 4 | *
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| 5 | * Copyright (C) 2008 by Vladimir Dronnikov <dronnikov@gmail.com>
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| 6 | *
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| 7 | * Licensed under GPLv2, see file LICENSE in this source tree.
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| 8 | */
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| 9 | #include "libbb.h"
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| 10 | #include "mail.h"
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| 11 |
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| 12 | // limit maximum allowed number of headers to prevent overflows.
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| 13 | // set to 0 to not limit
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| 14 | #define MAX_HEADERS 256
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| 15 |
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| 16 | static int smtp_checkp(const char *fmt, const char *param, int code)
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| 17 | {
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| 18 | char *answer;
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| 19 | const char *msg = command(fmt, param);
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| 20 | // read stdin
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| 21 | // if the string has a form \d\d\d- -- read next string. E.g. EHLO response
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| 22 | // parse first bytes to a number
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| 23 | // if code = -1 then just return this number
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| 24 | // if code != -1 then checks whether the number equals the code
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| 25 | // if not equal -> die saying msg
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| 26 | while ((answer = xmalloc_fgetline(stdin)) != NULL)
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| 27 | if (strlen(answer) <= 3 || '-' != answer[3])
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| 28 | break;
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| 29 | if (answer) {
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| 30 | int n = atoi(answer);
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| 31 | if (timeout)
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| 32 | alarm(0);
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| 33 | free(answer);
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| 34 | if (-1 == code || n == code)
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| 35 | return n;
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| 36 | }
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| 37 | bb_error_msg_and_die("%s failed", msg);
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| 38 | }
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| 39 |
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| 40 | static int smtp_check(const char *fmt, int code)
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| 41 | {
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| 42 | return smtp_checkp(fmt, NULL, code);
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| 43 | }
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| 44 |
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| 45 | // strip argument of bad chars
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| 46 | static char *sane_address(char *str)
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| 47 | {
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| 48 | char *s = str;
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| 49 | char *p = s;
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| 50 | while (*s) {
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| 51 | if (isalnum(*s) || '_' == *s || '-' == *s || '.' == *s || '@' == *s) {
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| 52 | *p++ = *s;
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| 53 | }
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| 54 | s++;
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| 55 | }
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| 56 | *p = '\0';
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| 57 | return str;
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| 58 | }
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| 59 |
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| 60 | static void rcptto(const char *s)
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| 61 | {
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| 62 | // N.B. we don't die if recipient is rejected, for the other recipients may be accepted
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| 63 | if (250 != smtp_checkp("RCPT TO:<%s>", s, -1))
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| 64 | bb_error_msg("Bad recipient: <%s>", s);
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| 65 | }
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| 66 |
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| 67 | int sendmail_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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| 68 | int sendmail_main(int argc UNUSED_PARAM, char **argv)
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| 69 | {
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| 70 | char *opt_connect = opt_connect;
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| 71 | char *opt_from;
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| 72 | char *s;
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| 73 | llist_t *list = NULL;
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| 74 | char *domain = sane_address(safe_getdomainname());
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| 75 | unsigned nheaders = 0;
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| 76 | int code;
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| 77 |
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| 78 | enum {
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| 79 | //--- standard options
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| 80 | OPT_t = 1 << 0, // read message for recipients, append them to those on cmdline
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| 81 | OPT_f = 1 << 1, // sender address
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| 82 | OPT_o = 1 << 2, // various options. -oi IMPLIED! others are IGNORED!
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| 83 | OPT_i = 1 << 3, // IMPLIED!
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| 84 | //--- BB specific options
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| 85 | OPT_w = 1 << 4, // network timeout
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| 86 | OPT_H = 1 << 5, // use external connection helper
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| 87 | OPT_S = 1 << 6, // specify connection string
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| 88 | OPT_a = 1 << 7, // authentication tokens
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| 89 | };
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| 90 |
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| 91 | // init global variables
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| 92 | INIT_G();
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| 93 |
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| 94 | // save initial stdin since body is piped!
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| 95 | xdup2(STDIN_FILENO, 3);
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| 96 | G.fp0 = xfdopen_for_read(3);
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| 97 |
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| 98 | // parse options
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| 99 | // -f is required. -H and -S are mutually exclusive
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| 100 | opt_complementary = "f:w+:H--S:S--H:a::";
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| 101 | // N.B. since -H and -S are mutually exclusive they do not interfere in opt_connect
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| 102 | // -a is for ssmtp (http://downloads.openwrt.org/people/nico/man/man8/ssmtp.8.html) compatibility,
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| 103 | // it is still under development.
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| 104 | opts = getopt32(argv, "tf:o:iw:H:S:a::", &opt_from, NULL, &timeout, &opt_connect, &opt_connect, &list);
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| 105 | //argc -= optind;
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| 106 | argv += optind;
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| 107 |
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| 108 | // process -a[upm]<token> options
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| 109 | if ((opts & OPT_a) && !list)
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| 110 | bb_show_usage();
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| 111 | while (list) {
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| 112 | char *a = (char *) llist_pop(&list);
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| 113 | if ('u' == a[0])
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| 114 | G.user = xstrdup(a+1);
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| 115 | if ('p' == a[0])
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| 116 | G.pass = xstrdup(a+1);
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| 117 | // N.B. we support only AUTH LOGIN so far
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| 118 | //if ('m' == a[0])
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| 119 | // G.method = xstrdup(a+1);
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| 120 | }
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| 121 | // N.B. list == NULL here
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| 122 | //bb_info_msg("OPT[%x] AU[%s], AP[%s], AM[%s], ARGV[%s]", opts, au, ap, am, *argv);
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| 123 |
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| 124 | // connect to server
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| 125 |
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| 126 | // connection helper ordered? ->
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| 127 | if (opts & OPT_H) {
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| 128 | const char *args[] = { "sh", "-c", opt_connect, NULL };
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| 129 | // plug it in
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| 130 | launch_helper(args);
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| 131 | // vanilla connection
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| 132 | } else {
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| 133 | int fd;
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| 134 | // host[:port] not explicitly specified? -> use $SMTPHOST
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| 135 | // no $SMTPHOST ? -> use localhost
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| 136 | if (!(opts & OPT_S)) {
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| 137 | opt_connect = getenv("SMTPHOST");
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| 138 | if (!opt_connect)
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| 139 | opt_connect = (char *)"127.0.0.1";
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| 140 | }
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| 141 | // do connect
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| 142 | fd = create_and_connect_stream_or_die(opt_connect, 25);
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| 143 | // and make ourselves a simple IO filter
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| 144 | xmove_fd(fd, STDIN_FILENO);
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| 145 | xdup2(STDIN_FILENO, STDOUT_FILENO);
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| 146 | }
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| 147 | // N.B. from now we know nothing about network :)
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| 148 |
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| 149 | // wait for initial server OK
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| 150 | // N.B. if we used openssl the initial 220 answer is already swallowed during openssl TLS init procedure
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| 151 | // so we need to kick the server to see whether we are ok
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| 152 | code = smtp_check("NOOP", -1);
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| 153 | // 220 on plain connection, 250 on openssl-helped TLS session
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| 154 | if (220 == code)
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| 155 | smtp_check(NULL, 250); // reread the code to stay in sync
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| 156 | else if (250 != code)
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| 157 | bb_error_msg_and_die("INIT failed");
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| 158 |
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| 159 | // we should start with modern EHLO
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| 160 | if (250 != smtp_checkp("EHLO %s", domain, -1)) {
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| 161 | smtp_checkp("HELO %s", domain, 250);
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| 162 | }
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| 163 | if (ENABLE_FEATURE_CLEAN_UP)
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| 164 | free(domain);
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| 165 |
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| 166 | // perform authentication
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| 167 | if (opts & OPT_a) {
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| 168 | smtp_check("AUTH LOGIN", 334);
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| 169 | // we must read credentials unless they are given via -a[up] options
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| 170 | if (!G.user || !G.pass)
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| 171 | get_cred_or_die(4);
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| 172 | encode_base64(NULL, G.user, NULL);
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| 173 | smtp_check("", 334);
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| 174 | encode_base64(NULL, G.pass, NULL);
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| 175 | smtp_check("", 235);
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| 176 | }
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| 177 |
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| 178 | // set sender
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| 179 | // N.B. we have here a very loosely defined algotythm
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| 180 | // since sendmail historically offers no means to specify secrets on cmdline.
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| 181 | // 1) server can require no authentication ->
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| 182 | // we must just provide a (possibly fake) reply address.
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| 183 | // 2) server can require AUTH ->
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| 184 | // we must provide valid username and password along with a (possibly fake) reply address.
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| 185 | // For the sake of security username and password are to be read either from console or from a secured file.
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| 186 | // Since reading from console may defeat usability, the solution is either to read from a predefined
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| 187 | // file descriptor (e.g. 4), or again from a secured file.
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| 188 |
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| 189 | // got no sender address? -> use system username as a resort
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| 190 | // N.B. we marked -f as required option!
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| 191 | //if (!G.user) {
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| 192 | // // N.B. IMHO getenv("USER") can be way easily spoofed!
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| 193 | // G.user = xuid2uname(getuid());
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| 194 | // opt_from = xasprintf("%s@%s", G.user, domain);
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| 195 | //}
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| 196 | //if (ENABLE_FEATURE_CLEAN_UP)
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| 197 | // free(domain);
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| 198 | smtp_checkp("MAIL FROM:<%s>", opt_from, 250);
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| 199 |
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| 200 | // process message
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| 201 |
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| 202 | // read recipients from message and add them to those given on cmdline.
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| 203 | // this means we scan stdin for To:, Cc:, Bcc: lines until an empty line
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| 204 | // and then use the rest of stdin as message body
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| 205 | code = 0; // set "analyze headers" mode
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| 206 | while ((s = xmalloc_fgetline(G.fp0)) != NULL) {
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| 207 | dump:
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| 208 | // put message lines doubling leading dots
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| 209 | if (code) {
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| 210 | // escape leading dots
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| 211 | // N.B. this feature is implied even if no -i (-oi) switch given
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| 212 | // N.B. we need to escape the leading dot regardless of
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| 213 | // whether it is single or not character on the line
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| 214 | if ('.' == s[0] /*&& '\0' == s[1] */)
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| 215 | printf(".");
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| 216 | // dump read line
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| 217 | printf("%s\r\n", s);
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| 218 | free(s);
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| 219 | continue;
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| 220 | }
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| 221 |
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| 222 | // analyze headers
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| 223 | // To: or Cc: headers add recipients
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| 224 | if (0 == strncasecmp("To:", s, 3) || 0 == strncasecmp("Bcc:" + 1, s, 3)) {
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| 225 | rcptto(sane_address(s+3));
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| 226 | goto addheader;
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| 227 | // Bcc: header adds blind copy (hidden) recipient
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| 228 | } else if (0 == strncasecmp("Bcc:", s, 4)) {
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| 229 | rcptto(sane_address(s+4));
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| 230 | free(s);
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| 231 | // N.B. Bcc: vanishes from headers!
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| 232 |
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| 233 | // other headers go verbatim
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| 234 |
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| 235 | // N.B. RFC2822 2.2.3 "Long Header Fields" allows for headers to occupy several lines.
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| 236 | // Continuation is denoted by prefixing additional lines with whitespace(s).
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| 237 | // Thanks (stefan.seyfried at googlemail.com) for pointing this out.
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| 238 | } else if (strchr(s, ':') || (list && skip_whitespace(s) != s)) {
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| 239 | addheader:
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| 240 | // N.B. we allow MAX_HEADERS generic headers at most to prevent attacks
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| 241 | if (MAX_HEADERS && ++nheaders >= MAX_HEADERS)
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| 242 | goto bail;
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| 243 | llist_add_to_end(&list, s);
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| 244 | // a line without ":" (an empty line too, by definition) doesn't look like a valid header
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| 245 | // so stop "analyze headers" mode
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| 246 | } else {
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| 247 | reenter:
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| 248 | // put recipients specified on cmdline
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| 249 | while (*argv) {
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| 250 | char *t = sane_address(*argv);
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| 251 | rcptto(t);
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| 252 | //if (MAX_HEADERS && ++nheaders >= MAX_HEADERS)
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| 253 | // goto bail;
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| 254 | llist_add_to_end(&list, xasprintf("To: %s", t));
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| 255 | argv++;
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| 256 | }
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| 257 | // enter "put message" mode
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| 258 | // N.B. DATA fails iff no recipients were accepted (or even provided)
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| 259 | // in this case just bail out gracefully
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| 260 | if (354 != smtp_check("DATA", -1))
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| 261 | goto bail;
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| 262 | // dump the headers
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| 263 | while (list) {
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| 264 | printf("%s\r\n", (char *) llist_pop(&list));
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| 265 | }
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| 266 | // stop analyzing headers
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| 267 | code++;
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| 268 | // N.B. !s means: we read nothing, and nothing to be read in the future.
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| 269 | // just dump empty line and break the loop
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| 270 | if (!s) {
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| 271 | puts("\r");
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| 272 | break;
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| 273 | }
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| 274 | // go dump message body
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| 275 | // N.B. "s" already contains the first non-header line, so pretend we read it from input
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| 276 | goto dump;
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| 277 | }
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| 278 | }
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| 279 | // odd case: we didn't stop "analyze headers" mode -> message body is empty. Reenter the loop
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| 280 | // N.B. after reenter code will be > 0
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| 281 | if (!code)
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| 282 | goto reenter;
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| 283 |
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| 284 | // finalize the message
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| 285 | smtp_check(".", 250);
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| 286 | bail:
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| 287 | // ... and say goodbye
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| 288 | smtp_check("QUIT", 221);
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| 289 | // cleanup
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| 290 | if (ENABLE_FEATURE_CLEAN_UP)
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| 291 | fclose(G.fp0);
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| 292 |
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| 293 | return EXIT_SUCCESS;
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| 294 | }
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