[~andy/fetchmail] / sink.c

/*
 * sink.c -- forwarding/delivery support for fetchmail
 *
 * The interface of this module (open_sink(), stuff_line(), close_sink(),
 * release_sink()) seals off the delivery logic from the protocol machine,
 * so the latter won't have to care whether it's shipping to an [SL]MTP
 * listener daemon or an MDA pipe.
 *
 * Copyright 1998 by Eric S. Raymond
 * For license terms, see the file COPYING in this directory.
 */

#include  "config.h"
#include  <stdio.h>
#include  <errno.h>
#include  <string.h>
#include  <signal.h>
#include  <time.h>
#ifdef HAVE_MEMORY_H
#include  <memory.h>
#endif /* HAVE_MEMORY_H */
#if defined(STDC_HEADERS)
#include  <stdlib.h>
#endif
#if defined(HAVE_UNISTD_H)
#include  <unistd.h>
#endif
#if defined(HAVE_STDARG_H)
#include  <stdarg.h>
#else
#include  <varargs.h>
#endif
#include  <ctype.h>
#include  <time.h>

#include  "fetchmail.h"
#include  "socket.h"
#include  "smtp.h"
#include  "i18n.h"

/* BSD portability hack...I know, this is an ugly place to put it */
#if !defined(SIGCHLD) && defined(SIGCLD)
#define SIGCHLD SIGCLD
#endif

/* makes the open_sink()/close_sink() pair non-reentrant */
static int lmtp_responses;

void smtp_close(struct query *ctl, int sayquit)
/* close the socket to SMTP server */
{
    if (ctl->smtp_socket != -1)
    {
        if (sayquit)
            SMTP_quit(ctl->smtp_socket);
        SockClose(ctl->smtp_socket);
        ctl->smtp_socket = -1;
    }
    batchcount = 0;
}

int smtp_open(struct query *ctl)
/* try to open a socket to the appropriate SMTP server for this query */ 
{
    char *parsed_host = NULL;

    /* maybe it's time to close the socket in order to force delivery */
    if (NUM_NONZERO(ctl->batchlimit)) {
        if (batchcount == ctl->batchlimit)
            smtp_close(ctl, 1);
        batchcount++;
    }

    /* if no socket to any SMTP host is already set up, try to open one */
    if (ctl->smtp_socket == -1) 
    {
        /* 
         * RFC 1123 requires that the domain name in HELO address is a
         * "valid principal domain name" for the client host. If we're
         * running in invisible mode, violate this with malice
         * aforethought in order to make the Received headers and
         * logging look right.
         *
         * In fact this code relies on the RFC1123 requirement that the
         * SMTP listener must accept messages even if verification of the
         * HELO name fails (RFC1123 section 5.2.5, paragraph 2).
         *
         * How we compute the true mailhost name to pass to the
         * listener doesn't affect behavior on RFC1123-violating
         * listeners that check for name match; we're going to lose
         * on those anyway because we can never give them a name
         * that matches the local machine fetchmail is running on.
         * What it will affect is the listener's logging.
         */
        struct idlist   *idp;
        const char *id_me = run.invisible ? ctl->server.truename : fetchmailhost;
        int oldphase = phase;

        errno = 0;

        /*
         * Run down the SMTP hunt list looking for a server that's up.
         * Use both explicit hunt entries (value TRUE) and implicit 
         * (default) ones (value FALSE).
         */
        oldphase = phase;
        phase = LISTENER_WAIT;

        set_timeout(ctl->server.timeout);
        for (idp = ctl->smtphunt; idp; idp = idp->next)
        {
            char        *cp;
#ifdef INET6_ENABLE 
            char        *portnum = SMTP_PORT;
#else
            int         portnum = SMTP_PORT;
#endif /* INET6_ENABLE */

            xalloca(parsed_host, char *, strlen(idp->id) + 1);

            ctl->smtphost = idp->id;  /* remember last host tried. */
            if(ctl->smtphost[0]=='/')
                ctl->listener = LMTP_MODE;

            strcpy(parsed_host, idp->id);
            if ((cp = strrchr(parsed_host, '/')))
            {
                *cp++ = 0;
#ifdef INET6_ENABLE 
                portnum = cp;
#else
                portnum = atoi(cp);
#endif /* INET6_ENABLE */
            }

            if (ctl->smtphost[0]=='/'){
                if ((ctl->smtp_socket = UnixOpen(ctl->smtphost))==-1)
                    continue;
            } else
                if ((ctl->smtp_socket = SockOpen(parsed_host,portnum,NULL,
                                             ctl->server.plugout)) == -1)
                    continue;

            /* return immediately for ODMR */
            if (ctl->server.protocol == P_ODMR)
            {
               set_timeout(0);
               phase = oldphase;
               return(ctl->smtp_socket); /* success */
            }

            /* are we doing SMTP or LMTP? */
            SMTP_setmode(ctl->listener);

            /* first, probe for ESMTP */
            if (SMTP_ok(ctl->smtp_socket) == SM_OK &&
                    SMTP_ehlo(ctl->smtp_socket, id_me, 
                              ctl->server.esmtp_name, ctl->server.esmtp_password,
                              &ctl->server.esmtp_options) == SM_OK)
               break;  /* success */

            /*
             * RFC 1869 warns that some listeners hang up on a failed EHLO,
             * so it's safest not to assume the socket will still be good.
             */
            smtp_close(ctl, 0);

            /* if opening for ESMTP failed, try SMTP */
            if ((ctl->smtp_socket = SockOpen(parsed_host,portnum,NULL,
                                             ctl->server.plugout)) == -1)
                continue;

            if (SMTP_ok(ctl->smtp_socket) == SM_OK && 
                    SMTP_helo(ctl->smtp_socket, id_me) == SM_OK)
                break;  /* success */

            smtp_close(ctl, 0);
        }
        set_timeout(0);
        phase = oldphase;
    }

    /*
     * RFC 1123 requires that the domain name part of the
     * RCPT TO address be "canonicalized", that is a FQDN
     * or MX but not a CNAME.  Some listeners (like exim)
     * enforce this.  Now that we have the actual hostname,
     * compute what we should canonicalize with.
     * 
     * make sure we do not forget to drop the /port if
     * using LMTP (hmh)
     */
    if (ctl->listener == LMTP_MODE && !ctl->smtpaddress) 
    {
        if (parsed_host && parsed_host[0] != 0)
                ctl->destaddr = xstrdup(parsed_host);
        else 
                ctl->destaddr = (ctl->smtphost && ctl->smtphost[0] != '/') ? ctl->smtphost : "localhost";
    } 
    else 
        ctl->destaddr = ctl->smtpaddress ? ctl->smtpaddress : ( ctl->smtphost && ctl->smtphost[0] != '/' ? ctl->smtphost : "localhost");

    if (outlevel >= O_DEBUG && ctl->smtp_socket != -1)
        report(stdout, GT_("forwarding to %s\n"), ctl->smtphost);

    return(ctl->smtp_socket);
}

static void sanitize(char *s)
/* replace unsafe shellchars by an _ */
{
    const static char *ok_chars = " 1234567890!@%-_=+:,./abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    char *cp;

    for (cp = s; *(cp += strspn(cp, ok_chars)); /* NO INCREMENT */)
        *cp = '_';
}

static int send_bouncemail(struct query *ctl, struct msgblk *msg,
                           int userclass, char *message,
                           int nerrors, char *errors[])
/* bounce back an error report a la RFC 1892 */
{
    char daemon_name[18 + HOSTLEN] = "FETCHMAIL-DAEMON@";
    char boundary[BUFSIZ], *bounce_to;
    int sock;

    /* don't bounce in reply to undeliverable bounces */
    if (!msg->return_path[0] || strcmp(msg->return_path, "<>") == 0)
        return(FALSE);

    bounce_to = (run.bouncemail ? msg->return_path : run.postmaster);

    SMTP_setmode(SMTP_MODE);

    /* can't just use fetchmailhost here, it might be localhost */
    strcat(daemon_name, host_fqdn());

    /* we need only SMTP for this purpose */
    if ((sock = SockOpen("localhost", SMTP_PORT, NULL, NULL)) == -1
                || SMTP_ok(sock) != SM_OK 
                || SMTP_helo(sock, fetchmailhost) != SM_OK
                || SMTP_from(sock, daemon_name, (char *)NULL) != SM_OK
                || SMTP_rcpt(sock, bounce_to) != SM_OK
                || SMTP_data(sock) != SM_OK)
        return(FALSE);

    /* our first duty is to keep the sacred foo counters turning... */
#ifdef HAVE_SNPRINTF
    snprintf(boundary, sizeof(boundary),
#else
    sprintf(boundary,
#endif /* HAVE_SNPRINTF */
            "foo-mani-padme-hum-%d-%d-%ld", 
            (int)getpid(), (int)getppid(), time((time_t *)NULL));

    if (outlevel >= O_VERBOSE)
        report(stdout, GT_("SMTP: (bounce-message body)\n"));
    else
        /* this will usually go to sylog... */
        report(stderr, GT_("mail from %s bounced to %s\n"),
               daemon_name, bounce_to);

    /* bouncemail headers */
    SockPrintf(sock, "Return-Path: <>\r\n");
    SockPrintf(sock, "From: %s\r\n", daemon_name);
    SockPrintf(sock, "To: %s\r\n", bounce_to);
    SockPrintf(sock, "MIME-Version: 1.0\r\n");
    SockPrintf(sock, "Content-Type: multipart/report; report-type=delivery-status;\r\n\tboundary=\"%s\"\r\n", boundary);
    SockPrintf(sock, "\r\n");

    /* RFC1892 part 1 -- human-readable message */
    SockPrintf(sock, "--%s\r\n", boundary); 
    SockPrintf(sock,"Content-Type: text/plain\r\n");
    SockPrintf(sock, "\r\n");
    SockWrite(sock, message, strlen(message));
    SockPrintf(sock, "\r\n");
    SockPrintf(sock, "\r\n");

    if (nerrors)
    {
        struct idlist   *idp;
        int             nusers;
        
        /* RFC1892 part 2 -- machine-readable responses */
        SockPrintf(sock, "--%s\r\n", boundary); 
        SockPrintf(sock,"Content-Type: message/delivery-status\r\n");
        SockPrintf(sock, "\r\n");
        SockPrintf(sock, "Reporting-MTA: dns; %s\r\n", fetchmailhost);

        nusers = 0;
        for (idp = msg->recipients; idp; idp = idp->next)
            if (idp->val.status.mark == userclass)
            {
                char    *error;
                /* Minimum RFC1894 compliance + Diagnostic-Code field */
                SockPrintf(sock, "\r\n");
                SockPrintf(sock, "Final-Recipient: rfc822; %s@%s\r\n", 
                           idp->id, fetchmailhost);
                SockPrintf(sock, "Last-Attempt-Date: %s\r\n", rfc822timestamp());
                SockPrintf(sock, "Action: failed\r\n");

                if (nerrors == 1)
                    /* one error applies to all users */
                    error = errors[0];
                else if (nerrors > nusers)
                {
                    SockPrintf(sock, "Internal error: SMTP error count doesn't match number of recipients.\r\n");
                    break;
                }
                else
                    /* errors correspond 1-1 to selected users */
                    error = errors[nusers++];
                
                if (strlen(error) > 9 && isdigit(error[4])
                        && error[5] == '.' && isdigit(error[6])
                        && error[7] == '.' && isdigit(error[8]))
                    /* Enhanced status code available, use it */
                    SockPrintf(sock, "Status: %5.5s\r\n", &(error[4]));
                else
                    /* Enhanced status code not available, fake one */
                    SockPrintf(sock, "Status: %c.0.0\r\n", error[0]);
                SockPrintf(sock, "Diagnostic-Code: %s\r\n", error);
            }
        SockPrintf(sock, "\r\n");
    }

    /* RFC1892 part 3 -- headers of undelivered message */
    SockPrintf(sock, "--%s\r\n", boundary); 
    SockPrintf(sock, "Content-Type: text/rfc822-headers\r\n");
    SockPrintf(sock, "\r\n");
    SockWrite(sock, msg->headers, strlen(msg->headers));
    SockPrintf(sock, "\r\n");
    SockPrintf(sock, "--%s--\r\n", boundary); 

    if (SMTP_eom(sock) != SM_OK || SMTP_quit(sock))
        return(FALSE);

    SockClose(sock);

    return(TRUE);
}

static int handle_smtp_report(struct query *ctl, struct msgblk *msg)
/* handle SMTP errors based on the content of SMTP_response */
/* return of PS_REFUSED deletes mail from the server; PS_TRANSIENT keeps it */
{
    int smtperr = atoi(smtp_response);
    char *responses[1];

    xalloca(responses[0], char *, strlen(smtp_response)+1);
    strcpy(responses[0], smtp_response);

#ifdef __UNUSED__
    /*
     * Don't do this!  It can really mess you up if, for example, you're
     * reporting an error with a single RCPT TO address among several;
     * RSET discards the message body and it doesn't get sent to the
     * valid recipients.
     */
    SMTP_rset(ctl->smtp_socket);    /* stay on the safe side */
    if (outlevel >= O_DEBUG)
        report(stdout, GT_("Saved error is still %d\n"), smtperr);
#endif /* __UNUSED */

    /*
     * Note: send_bouncemail message strings are not made subject
     * to gettext translation because (a) they're going to be 
     * embedded in a text/plain 7bit part, and (b) they're
     * going to be associated with listener error-response
     * messages, which are probably in English (none of the
     * MTAs I know about are internationalized).
     */
    if (str_find(&ctl->antispam, smtperr))
    {
        /*
         * SMTP listener explicitly refuses to deliver mail
         * coming from this address, probably due to an
         * anti-spam domain exclusion.  Respect this.  Don't
         * try to ship the message, and don't prevent it from
         * being deleted.  There's no point in bouncing the
         * email either since most spammers don't put their
         * real return email address anywhere in the headers
         * (unless the user insists with the SET SPAMBOUNCE
         * config option).
         *
         * Default values:
         *
         * 571 = sendmail's "unsolicited email refused"
         * 550 = exim's new antispam response (temporary)
         * 501 = exim's old antispam response
         * 554 = Postfix antispam response.
         *
         */
        if (run.spambounce)
     {
       char rejmsg[160];
#ifdef HAVE_SNPRINTF
       snprintf(rejmsg, sizeof(rejmsg),
#else
       sprintf(rejmsg,
#endif /* HAVE_SNPRINTF */
                "spam filter or virus scanner rejected message because:\r\n"
                "%s\r\n", responses[0]);
          
                send_bouncemail(ctl, msg, XMIT_ACCEPT,
                       rejmsg, 1, responses);
     }
        return(PS_REFUSED);
    }

    /*
     * Suppress error message only if the response specifically 
     * meant `excluded for policy reasons'.  We *should* see
     * an error when the return code is less specific.
     */
    if (smtperr >= 400)
        report(stderr, GT_("%cMTP error: %s\n"), 
              ctl->listener,
              responses[0]);

    switch (smtperr)
    {
    case 552: /* message exceeds fixed maximum message size */
        /*
         * Permanent no-go condition on the
         * ESMTP server.  Don't try to ship the message, 
         * and allow it to be deleted.
         */
        if (run.bouncemail)
            send_bouncemail(ctl, msg, XMIT_ACCEPT,
                        "This message was too large (SMTP error 552).\r\n", 
                        1, responses);
        return(PS_REFUSED);
  
    case 553: /* invalid sending domain */
        /*
         * These latter days 553 usually means a spammer is trying to
         * cover his tracks.  We never bouncemail on these, because 
         * (a) the return address is invalid by definition, and 
         * (b) we wouldn't want spammers to get confirmation that
         * this address is live, anyway.
         */
#ifdef __DONT_FEED_THE_SPAMMERS__
        if (run.bouncemail)
            send_bouncemail(ctl, msg, XMIT_ACCEPT,
                        "Invalid address in MAIL FROM (SMTP error 553).\r\n", 
                        1, responses);
#endif /* __DONT_FEED_THE_SPAMMERS__ */
        return(PS_REFUSED);

    default:
        /* bounce non-transient errors back to the sender */
        if (smtperr >= 500 && smtperr <= 599)
            if (send_bouncemail(ctl, msg, XMIT_ACCEPT,
                                "General SMTP/ESMTP error.\r\n", 
                                1, responses))
                return(run.bouncemail ? PS_REFUSED : PS_TRANSIENT);
        /*
         * We're going to end up here on 4xx errors, like:
         *
         * 451: temporarily unable to identify sender (exim)
         * 452: temporary out-of-queue-space condition on the ESMTP server.
         *
         * These are temporary errors.  Don't try to ship the message,
         * and suppress deletion so it can be retried on a future
         * retrieval cycle.
         *
         * Bouncemail *might* be appropriate here as a delay
         * notification (note; if we ever add this, we must make
         * sure the RFC1894 Action field is "delayed" rather than
         * "failed").  But it's not really necessary because
         * these are not actual failures, we're very likely to be
         * able to recover on the next cycle.
         */
        return(PS_TRANSIENT);
    }
}

/* these are shared by open_sink and stuffline */
static FILE *sinkfp;

int stuffline(struct query *ctl, char *buf)
/* ship a line to the given control block's output sink (SMTP server or MDA) */
{
    int n, oldphase;
    char *last;

    /* The line may contain NUL characters. Find the last char to use
     * -- the real line termination is the sequence "\n\0".
     */
    last = buf;
    while ((last += strlen(last)) && (last[-1] != '\n'))
        last++;

    /* fix message lines that have only \n termination (for qmail) */
    if (ctl->forcecr)
    {
        if (last - 1 == buf || last[-2] != '\r')
        {
            last[-1] = '\r';
            *last++  = '\n';
            *last    = '\0';
        }
    }

    oldphase = phase;
    phase = FORWARDING_WAIT;

    /*
     * SMTP byte-stuffing.  We only do this if the protocol does *not*
     * use .<CR><LF> as EOM.  If it does, the server will already have
     * decorated any . lines it sends back up.
     */
    if (*buf == '.')
    {
        if (ctl->server.base_protocol->delimited)       /* server has already byte-stuffed */
        {
            if (ctl->mda)
                ++buf;
            else
                /* writing to SMTP, leave the byte-stuffing in place */;
        }
        else /* if (!protocol->delimited)       -- not byte-stuffed already */
        {
            if (!ctl->mda)
                SockWrite(ctl->smtp_socket, buf, 1);    /* byte-stuff it */
            else
                /* leave it alone */;
        }
    }

    /* we may need to strip carriage returns */
    if (ctl->stripcr)
    {
        char    *sp, *tp;

        for (sp = tp = buf; sp < last; sp++)
            if (*sp != '\r')
                *tp++ =  *sp;
        *tp = '\0';
        last = tp;
    }

    n = 0;
    if (ctl->mda || ctl->bsmtp)
        n = fwrite(buf, 1, last - buf, sinkfp);
    else if (ctl->smtp_socket != -1)
        n = SockWrite(ctl->smtp_socket, buf, last - buf);

    phase = oldphase;

    return(n);
}

static int open_bsmtp_sink(struct query *ctl, struct msgblk *msg,
              int *good_addresses, int *bad_addresses)
/* open a BSMTP stream */
{
    struct      idlist *idp;

    if (strcmp(ctl->bsmtp, "-") == 0)
        sinkfp = stdout;
    else
        sinkfp = fopen(ctl->bsmtp, "a");

    /* see the ap computation under the SMTP branch */
    fprintf(sinkfp, 
            "MAIL FROM: %s", (msg->return_path[0]) ? msg->return_path : user);

    if (ctl->pass8bits || (ctl->mimemsg & MSG_IS_8BIT))
        fputs(" BODY=8BITMIME", sinkfp);
    else if (ctl->mimemsg & MSG_IS_7BIT)
        fputs(" BODY=7BIT", sinkfp);

    /* exim's BSMTP processor does not handle SIZE */
    /* fprintf(sinkfp, " SIZE=%d", msg->reallen); */

    fprintf(sinkfp, "\r\n");

    /*
     * RFC 1123 requires that the domain name part of the
     * RCPT TO address be "canonicalized", that is a FQDN
     * or MX but not a CNAME.  Some listeners (like exim)
     * enforce this.  Now that we have the actual hostname,
     * compute what we should canonicalize with.
     */
    ctl->destaddr = ctl->smtpaddress ? ctl->smtpaddress : "localhost";

    *bad_addresses = 0;
    for (idp = msg->recipients; idp; idp = idp->next)
        if (idp->val.status.mark == XMIT_ACCEPT)
        {
            if (ctl->smtpname)
                fprintf(sinkfp, "RCPT TO: %s\r\n", ctl->smtpname);
            else if (strchr(idp->id, '@'))
                fprintf(sinkfp,
                        "RCPT TO: %s\r\n", idp->id);
            else
                fprintf(sinkfp,
                        "RCPT TO: %s@%s\r\n", idp->id, ctl->destaddr);
            *good_addresses = 0;
        }

    fputs("DATA\r\n", sinkfp);

    if (ferror(sinkfp))
    {
        report(stderr, GT_("BSMTP file open or preamble write failed\n"));
        return(PS_BSMTP);
    }

    return(PS_SUCCESS);
}

/* this is experimental and will be removed if double bounces are reported */
#define EXPLICIT_BOUNCE_ON_BAD_ADDRESS


static const char *is_quad(const char *q)
/* Check if the string passed in points to what could be one quad of a
 * dotted-quad IP address.  Requirements are that the string is not a
 * NULL pointer, begins with a period (which is skipped) or a digit
 * and ends with a period or a NULL.  If these requirements are met, a
 * pointer to the last character (the period or the NULL character) is
 * returned; otherwise NULL.
 */
{
  const char *r;
  
  if (!q || !*q)
    return NULL;
  if (*q == '.')
    q++;
  for(r=q;isdigit(*r);r++)
    ;
  if ( ((*r) && (*r != '.')) || ((r-q) < 1) || ((r-q)>3) )
    return NULL;
  /* Make sure quad is < 255 */
  if ( (r-q) == 3)
    if (*q > '2')
      return NULL;
    else if (*q == '2')
    {
      if (*(q+1) > '5')
        return NULL;
      else if (*(q+1) == '5')
      {
        if (*(q+2) > '5')
          return NULL;
      }
    }
  return r;
}

static int is_dottedquad(const char *hostname)
/* Returns a true value if the passed in string looks like an IP
 *  address in dotted-quad form, and a false value otherwise.
 */

{
  return ((hostname=is_quad(is_quad(is_quad(is_quad(hostname))))) != NULL) &&
    (*hostname == '\0');
}

static int open_smtp_sink(struct query *ctl, struct msgblk *msg,
              int *good_addresses, int *bad_addresses)
/* open an SMTP stream */
{
    const char  *ap;
    struct      idlist *idp;
    char                options[MSGBUFSIZE]; 
    char                addr[HOSTLEN+USERNAMELEN+1];
#ifdef EXPLICIT_BOUNCE_ON_BAD_ADDRESS
    char                **from_responses;
#endif /* EXPLICIT_BOUNCE_ON_BAD_ADDRESS */
    int         total_addresses;
    int         force_transient_error = 0;

    /*
     * Compute ESMTP options.
     */
    options[0] = '\0';
    if (ctl->server.esmtp_options & ESMTP_8BITMIME) {
         if (ctl->pass8bits || (ctl->mimemsg & MSG_IS_8BIT))
            strcpy(options, " BODY=8BITMIME");
         else if (ctl->mimemsg & MSG_IS_7BIT)
            strcpy(options, " BODY=7BIT");
    }

    if ((ctl->server.esmtp_options & ESMTP_SIZE) && msg->reallen > 0)
        sprintf(options + strlen(options), " SIZE=%d", msg->reallen);

    /*
     * Try to get the SMTP listener to take the Return-Path
     * address as MAIL FROM.  If it won't, fall back on the
     * remotename and mailserver host.  This won't affect replies,
     * which use the header From address anyway; the MAIL FROM
     * address is a place for the SMTP listener to send
     * bouncemail.  The point is to guarantee a FQDN in the MAIL
     * FROM line -- some SMTP listeners, like smail, become
     * unhappy otherwise.
     *
     * RFC 1123 requires that the domain name part of the
     * MAIL FROM address be "canonicalized", that is a
     * FQDN or MX but not a CNAME.  We'll assume the Return-Path
     * header is already in this form here (it certainly
     * is if rewrite is on).  RFC 1123 is silent on whether
     * a nonexistent hostname part is considered canonical.
     *
     * This is a potential problem if the MTAs further upstream
     * didn't pass canonicalized From/Return-Path lines, *and* the
     * local SMTP listener insists on them. 
     *
     * Handle the case where an upstream MTA is setting a return
     * path equal to "@".  Ghod knows why anyone does this, but 
     * it's been reported to happen in mail from Amazon.com and
     * Motorola.
     *
     * Also, if the hostname is a dotted quad, wrap it in square brackets.
     * Apparently this is required by some RFC I wot not of.
     */
    if (!msg->return_path[0] || (0 == strcmp(msg->return_path, "@")))
    {
      if (is_dottedquad(ctl->server.truename))
      {
#ifdef HAVE_SNPRINTF
        snprintf(addr, sizeof(addr),
#else
                 sprintf(addr,
#endif /* HAVE_SNPRINTF */
              "%s@[%s]", ctl->remotename, ctl->server.truename);
      }
      else
      {
#ifdef HAVE_SNPRINTF
        snprintf(addr, sizeof(addr),
#else
        sprintf(addr,
#endif /* HAVE_SNPRINTF */
              "%s@%s", ctl->remotename, ctl->server.truename);
      }
        ap = addr;
    }
    else if (strchr(msg->return_path,'@') || strchr(msg->return_path,'!'))
        ap = msg->return_path;
    else                /* in case Return-Path existed but was local */
    {
      if (is_dottedquad(ctl->server.truename))
      {
#ifdef HAVE_SNPRINTF
        snprintf(addr, sizeof(addr),
#else
        sprintf(addr,
#endif /* HAVE_SNPRINTF */
                "%s@[%s]", msg->return_path, ctl->server.truename);
      }
      else
      {
#ifdef HAVE_SNPRINTF
        snprintf(addr, sizeof(addr),
#else
        sprintf(addr,
#endif /* HAVE_SNPRINTF */
                "%s@%s", msg->return_path, ctl->server.truename);
      }
        ap = addr;
    }

    if (SMTP_from(ctl->smtp_socket, ap, options) != SM_OK)
    {
        int err = handle_smtp_report(ctl, msg);

        SMTP_rset(ctl->smtp_socket);    /* stay on the safe side */
        return(err);
    }

    /*
     * Now list the recipient addressees
     */
    total_addresses = 0;
    for (idp = msg->recipients; idp; idp = idp->next)
        total_addresses++;
#ifdef EXPLICIT_BOUNCE_ON_BAD_ADDRESS
    xalloca(from_responses, char **, sizeof(char *) * total_addresses);
#endif /* EXPLICIT_BOUNCE_ON_BAD_ADDRESS */
    for (idp = msg->recipients; idp; idp = idp->next)
        if (idp->val.status.mark == XMIT_ACCEPT)
        {
            if (strchr(idp->id, '@'))
                strcpy(addr, idp->id);
            else {
                if (ctl->smtpname) {
#ifdef HAVE_SNPRINTF
                    snprintf(addr, sizeof(addr), "%s", ctl->smtpname);
#else
                    sprintf(addr, "%s", ctl->smtpname);
#endif /* HAVE_SNPRINTF */

                } else {
#ifdef HAVE_SNPRINTF
                  snprintf(addr, sizeof(addr), "%s@%s", idp->id, ctl->destaddr);
#else
                  sprintf(addr, "%s@%s", idp->id, ctl->destaddr);
#endif /* HAVE_SNPRINTF */
                }
            }
            if (SMTP_rcpt(ctl->smtp_socket, addr) == SM_OK)
                (*good_addresses)++;
            else
            {
#ifdef EXPLICIT_BOUNCE_ON_BAD_ADDRESS
                    char errbuf[POPBUFSIZE];
#endif /* EXPLICIT_BOUNCE_ON_BAD_ADDRESS */
                if (handle_smtp_report(ctl, msg) == PS_TRANSIENT)
                    force_transient_error = 1;

#ifdef EXPLICIT_BOUNCE_ON_BAD_ADDRESS
#ifdef HAVE_SNPRINTF
                snprintf(errbuf, sizeof(errbuf), "%s: %s",
                                idp->id, smtp_response);
#else
                strncpy(errbuf, idp->id, sizeof(errbuf));
                strcat(errbuf, ": ");
                strcat(errbuf, smtp_response);
#endif /* HAVE_SNPRINTF */

                xalloca(from_responses[*bad_addresses], 
                        char *, 
                        strlen(errbuf)+1);
                strcpy(from_responses[*bad_addresses], errbuf);
#endif /* EXPLICIT_BOUNCE_ON_BAD_ADDRESS */

                (*bad_addresses)++;
                idp->val.status.mark = XMIT_RCPTBAD;
                if (outlevel >= O_VERBOSE)
                    report(stderr, 
                          GT_("%cMTP listener doesn't like recipient address `%s'\n"),
                          ctl->listener, addr);
            }
        }

#ifdef EXPLICIT_BOUNCE_ON_BAD_ADDRESS
    /*
     * This should not be necessary, because the SMTP listener itself
     * should genrate a bounce for the bad address.
     */
    if (*bad_addresses)
        send_bouncemail(ctl, msg, XMIT_RCPTBAD,
                        "Some addresses were rejected by the MDA fetchmail forwards to.\r\n",
                        *bad_addresses, from_responses);
#endif /* EXPLICIT_BOUNCE_ON_BAD_ADDRESS */

    /*
     * It's tempting to do local notification only if bouncemail was
     * insufficient -- that is, to add && total_addresses > *bad_addresses
     * to the test here.  The problem with this theory is that it would
     * make initial diagnosis of a broken multidrop configuration very
     * hard -- most single-recipient messages would just invisibly bounce.
     */
    if (!(*good_addresses)) 
    {
        if (force_transient_error) {
                /* do not risk dataloss due to overengineered multidrop
                 * crap. If one of the recipients returned PS_TRANSIENT,
                 * we return exactly that.
                 */
                SMTP_rset(ctl->smtp_socket);        /* required by RFC1870 */
                return(PS_TRANSIENT);
        }
        if (!run.postmaster[0])
        {
            if (outlevel >= O_VERBOSE)
                report(stderr, GT_("no address matches; no postmaster set.\n"));
            SMTP_rset(ctl->smtp_socket);        /* required by RFC1870 */
            return(PS_REFUSED);
        }
        if (strchr(run.postmaster, '@'))
            strncpy(addr, run.postmaster, sizeof(addr));
        else
        {
#ifdef HAVE_SNPRINTF
            snprintf(addr, sizeof(addr), "%s@%s", run.postmaster, ctl->destaddr);
#else
            sprintf(addr, "%s@%s", run.postmaster, ctl->destaddr);
#endif /* HAVE_SNPRINTF */
        }

        if (SMTP_rcpt(ctl->smtp_socket, addr) != SM_OK)
        {
            report(stderr, GT_("can't even send to %s!\n"), run.postmaster);
            SMTP_rset(ctl->smtp_socket);        /* required by RFC1870 */
            return(PS_REFUSED);
        }

        if (outlevel >= O_VERBOSE)
            report(stderr, GT_("no address matches; forwarding to %s.\n"), run.postmaster);
    }

    /* 
     * Tell the listener we're ready to send data.
     * Some listeners (like zmailer) may return antispam errors here.
     */
    if (SMTP_data(ctl->smtp_socket) != SM_OK)
    {
        SMTP_rset(ctl->smtp_socket);    /* stay on the safe side */
        return(handle_smtp_report(ctl, msg));
    }

    /*
     * We need to stash this away in order to know how many
     * response lines to expect after the LMTP end-of-message.
     */
    lmtp_responses = *good_addresses;

    return(PS_SUCCESS);
}

static int open_mda_sink(struct query *ctl, struct msgblk *msg,
              int *good_addresses, int *bad_addresses)
/* open a stream to a local MDA */
{
#ifdef HAVE_SIGACTION
    struct      sigaction sa_new;
#endif /* HAVE_SIGACTION */
    struct      idlist *idp;
    int length = 0, fromlen = 0, nameslen = 0;
    char        *names = NULL, *before, *after, *from = NULL;

    ctl->destaddr = "localhost";

    for (idp = msg->recipients; idp; idp = idp->next)
        if (idp->val.status.mark == XMIT_ACCEPT)
            (*good_addresses)++;

    length = strlen(ctl->mda);
    before = xstrdup(ctl->mda);

    /* get user addresses for %T (or %s for backward compatibility) */
    if (strstr(before, "%s") || strstr(before, "%T"))
    {
        /*
         * We go through this in order to be able to handle very
         * long lists of users and (re)implement %s.
         */
        nameslen = 0;
        for (idp = msg->recipients; idp; idp = idp->next)
            if ((idp->val.status.mark == XMIT_ACCEPT))
                nameslen += (strlen(idp->id) + 1);      /* string + ' ' */
        if ((*good_addresses == 0))
            nameslen = strlen(run.postmaster);

        names = (char *)xmalloc(nameslen + 1);  /* account for '\0' */
        if (*good_addresses == 0)
            strcpy(names, run.postmaster);
        else
        {
            names[0] = '\0';
            for (idp = msg->recipients; idp; idp = idp->next)
                if (idp->val.status.mark == XMIT_ACCEPT)
                {
                    strcat(names, idp->id);
                    strcat(names, " ");
                }
            names[--nameslen] = '\0';   /* chop trailing space */
        }

        /* sanitize names in order to contain only harmless shell chars */
        sanitize(names);
    }

    /* get From address for %F */
    if (strstr(before, "%F"))
    {
        from = xstrdup(msg->return_path);

        /* sanitize from in order to contain *only* harmless shell chars */
        sanitize(from);

        fromlen = strlen(from);
    }

    /* do we have to build an mda string? */
    if (names || from) 
    {           
        char    *sp, *dp;

        /* find length of resulting mda string */
        sp = before;
        while ((sp = strstr(sp, "%s"))) {
            length += nameslen - 2;     /* subtract %s */
            sp += 2;
        }
        sp = before;
        while ((sp = strstr(sp, "%T"))) {
            length += nameslen - 2;     /* subtract %T */
            sp += 2;
        }
        sp = before;
        while ((sp = strstr(sp, "%F"))) {
            length += fromlen - 2;      /* subtract %F */
            sp += 2;
        }

        after = xmalloc(length + 1);

        /* copy mda source string to after, while expanding %[sTF] */
        for (dp = after, sp = before; (*dp = *sp); dp++, sp++) {
            if (sp[0] != '%')   continue;

            /* need to expand? BTW, no here overflow, because in
            ** the worst case (end of string) sp[1] == '\0' */
            if (sp[1] == 's' || sp[1] == 'T') {
                strcpy(dp, names);
                dp += nameslen;
                sp++;   /* position sp over [sT] */
                dp--;   /* adjust dp */
            } else if (sp[1] == 'F') {
                strcpy(dp, from);
                dp += fromlen;
                sp++;   /* position sp over F */
                dp--;   /* adjust dp */
            }
        }

        if (names) {
            free(names);
            names = NULL;
        }
        if (from) {
            free(from);
            from = NULL;
        }

        free(before);

        before = after;
    }


    if (outlevel >= O_DEBUG)
        report(stdout, GT_("about to deliver with: %s\n"), before);

#ifdef HAVE_SETEUID
    /*
     * Arrange to run with user's permissions if we're root.
     * This will initialize the ownership of any files the
     * MDA creates properly.  (The seteuid call is available
     * under all BSDs and Linux)
     */
    seteuid(ctl->uid);
#endif /* HAVE_SETEUID */

    sinkfp = popen(before, "w");
    free(before);
    before = NULL;

#ifdef HAVE_SETEUID
    /* this will fail quietly if we didn't start as root */
    seteuid(0);
#endif /* HAVE_SETEUID */

    if (!sinkfp)
    {
        report(stderr, GT_("MDA open failed\n"));
        return(PS_IOERR);
    }

    /*
     * We need to disable the normal SIGCHLD handling here because 
     * sigchld_handler() would reap away the error status, returning
     * error status instead of 0 for successful completion.
     */
#ifndef HAVE_SIGACTION
    signal(SIGCHLD, SIG_DFL);
#else
    memset (&sa_new, 0, sizeof sa_new);
    sigemptyset (&sa_new.sa_mask);
    sa_new.sa_handler = SIG_DFL;
    sigaction (SIGCHLD, &sa_new, NULL);
#endif /* HAVE_SIGACTION */

    return(PS_SUCCESS);
}

int open_sink(struct query *ctl, struct msgblk *msg,
              int *good_addresses, int *bad_addresses)
/* set up sinkfp to be an input sink we can ship a message to */
{
    *bad_addresses = *good_addresses = 0;

    if (ctl->bsmtp)             /* dump to a BSMTP batch file */
        return(open_bsmtp_sink(ctl, msg, good_addresses, bad_addresses));
    /* 
     * Try to forward to an SMTP or LMTP listener.  If the attempt to 
     * open a socket fails, fall through to attempt delivery via
     * local MDA.
     */
    else if (!ctl->mda && smtp_open(ctl) != -1)
        return(open_smtp_sink(ctl, msg, good_addresses, bad_addresses));

    /*
     * Awkward case.  User didn't specify an MDA.  Our attempt to get a
     * listener socket failed.  Try to cope anyway -- initial configuration
     * may have found procmail.
     */
    else if (!ctl->mda)
    {
        report(stderr, GT_("%cMTP connect to %s failed\n"),
               ctl->listener,
               ctl->smtphost ? ctl->smtphost : "localhost");

#ifndef FALLBACK_MDA
        /* No fallback MDA declared.  Bail out. */
        return(PS_SMTP);
#else
        /*
         * If user had things set up to forward offsite, no way
         * we want to deliver locally!
         */
        if (ctl->smtphost && strcmp(ctl->smtphost, "localhost"))
            return(PS_SMTP);

        /* 
         * User was delivering locally.  We have a fallback MDA.
         * Latch it in place, logging the error, and fall through.
         * Set stripcr as we would if MDA had been the initial transport
         */
        ctl->mda = FALLBACK_MDA;
        if (!ctl->forcecr)
            ctl->stripcr = TRUE;

        report(stderr, GT_("can't raise the listener; falling back to %s"),
                         FALLBACK_MDA);
#endif
    }

    if (ctl->mda)               /* must deliver through an MDA */
        return(open_mda_sink(ctl, msg, good_addresses, bad_addresses));

    return(PS_SUCCESS);
}

void release_sink(struct query *ctl)
/* release the per-message output sink, whether it's a pipe or SMTP socket */
{
    if (ctl->bsmtp && sinkfp)
        fclose(sinkfp);
    else if (ctl->mda)
    {
        if (sinkfp)
        {
            pclose(sinkfp);
            sinkfp = (FILE *)NULL;
        }
        deal_with_sigchld(); /* Restore SIGCHLD handling to reap zombies */
    }
}

int close_sink(struct query *ctl, struct msgblk *msg, flag forward)
/* perform end-of-message actions on the current output sink */
{
    if (ctl->mda)
    {
        int rc;

        /* close the delivery pipe, we'll reopen before next message */
        if (sinkfp)
        {
            rc = pclose(sinkfp);
            sinkfp = (FILE *)NULL;
        }
        else
            rc = 0;

        deal_with_sigchld(); /* Restore SIGCHLD handling to reap zombies */

        if (rc)
        {
            report(stderr, 
                   GT_("MDA returned nonzero status %d\n"), rc);
            return(FALSE);
        }
    }
    else if (ctl->bsmtp && sinkfp)
    {
        int error;

        /* implicit disk-full check here... */
        fputs(".\r\n", sinkfp);
        error = ferror(sinkfp);
        if (strcmp(ctl->bsmtp, "-"))
            if (fclose(sinkfp) == EOF) error = 1;
        if (error)
        {
            report(stderr, 
                   GT_("Message termination or close of BSMTP file failed\n"));
            return(FALSE);
        }
    }
    else if (forward)
    {
        /* write message terminator */
        if (SMTP_eom(ctl->smtp_socket) != SM_OK)
        {
            if (handle_smtp_report(ctl, msg) != PS_REFUSED)
            {
                SMTP_rset(ctl->smtp_socket);    /* stay on the safe side */
                return(FALSE);
            }
            else
            {
                report(stderr, GT_("SMTP listener refused delivery\n"));
                SMTP_rset(ctl->smtp_socket);    /* stay on the safe side */
                return(TRUE);
            }
        }

        /*
         * If this is an SMTP connection, SMTP_eom() ate the response.
         * But could be this is an LMTP connection, in which case we have to
         * interpret either (a) a single 503 response meaning there
         * were no successful RCPT TOs, or (b) a variable number of
         * responses, one for each successful RCPT TO.  We need to send
         * bouncemail on each failed response and then return TRUE anyway,
         * otherwise the message will get left in the queue and resent
         * to people who got it the first time.
         */
        if (ctl->listener == LMTP_MODE)
        {
            if (lmtp_responses == 0)
            {
                SMTP_ok(ctl->smtp_socket); 

                /*
                 * According to RFC2033, 503 is the only legal response
                 * if no RCPT TO commands succeeded.  No error recovery
                 * is really possible here, as we have no idea what
                 * insane thing the listener might be doing if it doesn't
                 * comply.
                 */
                if (atoi(smtp_response) == 503)
                    report(stderr, GT_("LMTP delivery error on EOM\n"));
                else
                    report(stderr,
                          GT_("Unexpected non-503 response to LMTP EOM: %s\n"),
                          smtp_response);

                /*
                 * It's not completely clear what to do here.  We choose to
                 * interpret delivery failure here as a transient error, 
                 * the same way SMTP delivery failure is handled.  If we're
                 * wrong, an undead message will get stuck in the queue.
                 */
                return(FALSE);
            }
            else
            {
                int     i, errors;
                char    **responses;

                /* eat the RFC2033-required responses, saving errors */ 
                xalloca(responses, char **, sizeof(char *) * lmtp_responses);
                for (errors = i = 0; i < lmtp_responses; i++)
                {
                    if (SMTP_ok(ctl->smtp_socket) == SM_OK)
                        responses[i] = (char *)NULL;
                    else
                    {
                        xalloca(responses[errors], 
                                char *, 
                                strlen(smtp_response)+1);
                        strcpy(responses[errors], smtp_response);
                        errors++;
                    }
                }

                if (errors == 0)
                    return(TRUE);       /* all deliveries succeeded */
                else
                    /*
                     * One or more deliveries failed.
                     * If we can bounce a failures list back to the
                     * sender, and the postmaster does not want to
                     * deal with the bounces return TRUE, deleting the
                     * message from the server so it won't be
                     * re-forwarded on subsequent poll cycles.
                     */
                  return(send_bouncemail(ctl, msg, XMIT_ACCEPT,
                                         "LSMTP partial delivery failure.\r\n",
                                         errors, responses));
            }
        }
    }

    return(TRUE);
}

int open_warning_by_mail(struct query *ctl, struct msgblk *msg)
/* set up output sink for a mailed warning to calling user */
{
    int good, bad;

    /*
     * Dispatching warning email is a little complicated.  The problem is
     * that we have to deal with three distinct cases:
     *
     * 1. Single-drop running from user account.  Warning mail should
     * go to the local name for which we're collecting (coincides
     * with calling user).
     *
     * 2. Single-drop running from root or other privileged ID, with rc
     * file generated on the fly (Ken Estes's weird setup...)  Mail
     * should go to the local name for which we're collecting (does not 
     * coincide with calling user).
     * 
     * 3. Multidrop.  Mail must go to postmaster.  We leave the recipients
     * member null so this message will fall through to run.postmaster.
     *
     * The zero in the reallen element means we won't pass a SIZE
     * option to ESMTP; the message length would be more trouble than
     * it's worth to compute.
     */
    struct msgblk reply = {NULL, NULL, "FETCHMAIL-DAEMON@", 0};
    int status;

    strcat(reply.return_path, ctl->smtpaddress ? ctl->smtpaddress :
            fetchmailhost);

    if (!MULTIDROP(ctl))                /* send to calling user */
    {
        save_str(&reply.recipients, ctl->localnames->id, XMIT_ACCEPT);
        status = open_sink(ctl, &reply, &good, &bad);
        free_str_list(&reply.recipients);
    }
    else                                /* send to postmaster  */
        status = open_sink(ctl, &reply, &good, &bad);
    stuff_warning(ctl, "Date: %s", rfc822timestamp());
    return(status);
}

#if defined(HAVE_STDARG_H)
void stuff_warning(struct query *ctl, const char *fmt, ... )
#else
void stuff_warning(struct query *ctl, fmt, va_alist)
struct query *ctl;
const char *fmt;        /* printf-style format */
va_dcl
#endif
/* format and ship a warning message line by mail */
{
    char        buf[POPBUFSIZE];
    va_list ap;

    /*
     * stuffline() requires its input to be writeable (for CR stripping),
     * so we needed to copy the message to a writeable buffer anyway in
     * case it was a string constant.  We make a virtue of that necessity
     * here by supporting stdargs/varargs.
     */
#if defined(HAVE_STDARG_H)
    va_start(ap, fmt) ;
#else
    va_start(ap);
#endif
#ifdef HAVE_VSNPRINTF
    vsnprintf(buf, sizeof(buf), fmt, ap);
#else
    vsprintf(buf, fmt, ap);
#endif
    va_end(ap);

#ifdef HAVE_SNPRINTF
    snprintf(buf+strlen(buf), sizeof(buf)-strlen(buf), "\r\n");
#else
    strcat(buf, "\r\n");
#endif /* HAVE_SNPRINTF */

    stuffline(ctl, buf);
}

void close_warning_by_mail(struct query *ctl, struct msgblk *msg)
/* sign and send mailed warnings */
{
    stuff_warning(ctl, GT_("--\r\n\t\t\t\tThe Fetchmail Daemon\r\n"));
    close_sink(ctl, msg, TRUE);
}

/* sink.c ends here */