source: MondoRescue/branches/2.2.9/mindi-busybox/mailutils/sendmail.c

/* 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 source tree.
 */
#include "libbb.h"
#include "mail.h"

// limit maximum allowed number of headers to prevent overflows.
// set to 0 to not limit
#define MAX_HEADERS 256

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)
{
    // N.B. we don't die if recipient is rejected, for the other recipients may be accepted
    if (250 != smtp_checkp("RCPT TO:<%s>", s, -1))
        bb_error_msg("Bad recipient: <%s>", s);
}

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());
    unsigned nheaders = 0;
    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 = xfdopen_for_read(3);

    // 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) {
 dump:
        // 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, 3) || 0 == strncasecmp("Bcc:" + 1, s, 3)) {
            rcptto(sane_address(s+3));
            goto addheader;
        // Bcc: header adds blind copy (hidden) recipient
        } else if (0 == strncasecmp("Bcc:", s, 4)) {
            rcptto(sane_address(s+4));
            free(s);
            // N.B. Bcc: vanishes from headers!

        // other headers go verbatim

        // N.B. RFC2822 2.2.3 "Long Header Fields" allows for headers to occupy several lines.
        // Continuation is denoted by prefixing additional lines with whitespace(s).
        // Thanks (stefan.seyfried at googlemail.com) for pointing this out.
        } else if (strchr(s, ':') || (list && skip_whitespace(s) != s)) {
 addheader:
            // N.B. we allow MAX_HEADERS generic headers at most to prevent attacks
            if (MAX_HEADERS && ++nheaders >= MAX_HEADERS)
                goto bail;
            llist_add_to_end(&list, s);
        // a line without ":" (an empty line too, by definition) doesn't look like a valid header
        // so stop "analyze headers" mode
        } else {
 reenter:
            // put recipients specified on cmdline
            while (*argv) {
                char *t = sane_address(*argv);
                rcptto(t);
                //if (MAX_HEADERS && ++nheaders >= MAX_HEADERS)
                //  goto bail;
                llist_add_to_end(&list, xasprintf("To: %s", t));
                argv++;
            }
            // enter "put message" mode
            // N.B. DATA fails iff no recipients were accepted (or even provided)
            // in this case just bail out gracefully
            if (354 != smtp_check("DATA", -1))
                goto bail;
            // dump the headers
            while (list) {
                printf("%s\r\n", (char *) llist_pop(&list));
            }
            // stop analyzing headers
            code++;
            // N.B. !s means: we read nothing, and nothing to be read in the future.
            // just dump empty line and break the loop
            if (!s) {
                puts("\r");
                break;
            }
            // go dump message body
            // N.B. "s" already contains the first non-header line, so pretend we read it from input
            goto dump;
        }
    }
    // odd case: we didn't stop "analyze headers" mode -> message body is empty. Reenter the loop
    // N.B. after reenter code will be > 0
    if (!code)
        goto reenter;

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

    return EXIT_SUCCESS;
}