Tony Nugent's fixes.

[~andy/fetchmail] / driver.c

/*
 * driver.c -- generic driver for mail fetch method protocols
 *
 * Copyright 1996 by Eric S. Raymond
 * All rights reserved.
 * For license terms, see the file COPYING in this directory.
 */

#include  <config.h>
#include  <stdio.h>
#include  <setjmp.h>
#include  <errno.h>
#include  <ctype.h>
#include  <string.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
#if defined(HAVE_ALLOCA_H)
#include <alloca.h>
#endif
#include  <sys/time.h>
#include  <signal.h>

#ifdef HAVE_GETHOSTBYNAME
#include <netdb.h>
#include "mx.h"
#endif /* HAVE_GETHOSTBYNAME */

#ifdef KERBEROS_V4
#include <krb.h>
#include <des.h>
#include <netinet/in.h>
#include <netdb.h>
#endif /* KERBEROS_V4 */
#include  "socket.h"
#include  "fetchmail.h"
#include  "socket.h"
#include  "smtp.h"

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

#define SMTP_PORT       25      /* standard SMTP service port */

extern char *strstr();  /* needed on sysV68 R3V7.1. */

int batchlimit;         /* how often to tear down the delivery connection */
int fetchlimit;         /* how often to tear down the server connection */
int batchcount;         /* count of messages sent in current batch */
int peek_capable;       /* can we peek for better error recovery? */

static const struct method *protocol;
static jmp_buf  restart;

char tag[TAGLEN];
static int tagnum;
#define GENSYM  (sprintf(tag, "a%04d", ++tagnum), tag)

static char *shroud;    /* string to shroud in debug output, if  non-NULL */
static int mytimeout;   /* value of nonreponse timeout */

static void vtalarm(int timeleft)
/* reset the nonresponse-timeout */
{
    struct itimerval ntimeout;

    ntimeout.it_interval.tv_sec = ntimeout.it_interval.tv_usec = 0;
    ntimeout.it_value.tv_sec  = timeleft;
    ntimeout.it_value.tv_usec = 0;
    setitimer(ITIMER_VIRTUAL, &ntimeout, (struct itimerval *)NULL);
}

static void vtalarm_handler (int signal)
/* handle server-timeout SIGVTALARM signal */
{
    longjmp(restart, 1);
}

#ifdef HAVE_RES_SEARCH
#define MX_RETRIES      3

static int is_host_alias(const char *name, struct query *ctl)
/* determine whether name is a DNS alias of the hostname */
{
    struct hostent      *he;
    struct mxentry      *mxp, *mxrecords;

    /*
     * The first two checks are optimizations that will catch a good
     * many cases.  (1) check against the hostname the user
     * specified.  Odds are good this will either be the mailserver's
     * FQDN or a suffix of it with the mailserver's domain's default
     * host name omitted.  Then check the rest of the `also known as'
     * cache accumulated by previous DNS checks.  This cache is primed
     * by the aka list option.
     *
     * (2) check against the mailserver's FQDN, in case
     * it's not the same as the declared hostname.
     *
     * Either of these on a mail address is definitive.  Only if the
     * name doesn't match either is it time to call the bind library.
     * If this happens odds are good we're looking at an MX name.
     */
    if (str_in_list(&ctl->server.lead_server->names, name))
        return(TRUE);
    else if (strcmp(name, ctl->server.canonical_name) == 0)
        return(TRUE);
    else if (!ctl->server.dns)
        return(FALSE);

    /*
     * We know DNS service was up at the beginning of this poll cycle.
     * If it's down, our nameserver has crashed.  We don't want to try
     * delivering the current message or anything else from this
     * mailbox until it's back up.
     */
    else if ((he = gethostbyname(name)) != (struct hostent *)NULL)
    {
        if (strcmp(ctl->server.canonical_name, he->h_name) == 0)
            goto match;
        else
            return(FALSE);
    }
    else
        switch (h_errno)
        {
        case HOST_NOT_FOUND:    /* specified host is unknown */
        case NO_ADDRESS:        /* valid, but does not have an IP address */
            break;

        case NO_RECOVERY:       /* non-recoverable name server error */
        case TRY_AGAIN:         /* temporary error on authoritative server */
        default:
            if (outlevel != O_SILENT)
                putchar('\n');  /* terminate the progress message */
            error(0, 0,
                "nameserver failure while looking for `%s' during poll of %s.",
                name, ctl->server.names->id);
            ctl->errcount++;
            longjmp(restart, 2);        /* try again next poll cycle */
            break;
        }

    /*
     * We're only here if DNS was OK but the gethostbyname() failed
     * with a HOST_NOT_FOUND or NO_ADDRESS error.
     * Search for a name match on MX records pointing to the server.
     */
    h_errno = 0;
    if ((mxrecords = getmxrecords(name)) == (struct mxentry *)NULL)
    {
        switch (h_errno)
        {
        case HOST_NOT_FOUND:    /* specified host is unknown */
        case NO_ADDRESS:        /* valid, but does not have an IP address */
            return(FALSE);
            break;

        case NO_RECOVERY:       /* non-recoverable name server error */
        case TRY_AGAIN:         /* temporary error on authoritative server */
        default:
            error(0, 0,
                "nameserver failure while looking for `%s' during poll of %s.",
                name, ctl->server.names->id);
            ctl->errcount++;
            longjmp(restart, 2);        /* try again next poll cycle */
            break;
        }
    }
    else
    {
        for (mxp = mxrecords; mxp->name; mxp++)
            if (strcmp(ctl->server.canonical_name, mxp->name) == 0)
                goto match;
        return(FALSE);
    match:;
    }

    /* add this name to relevant server's `also known as' list */
    save_str(&ctl->server.lead_server->names, -1, name);
    return(TRUE);
}

static void map_name(name, ctl, xmit_names)
/* add given name to xmit_names if it matches declared localnames */
const char *name;               /* name to map */
struct query *ctl;              /* list of permissible aliases */
struct idlist **xmit_names;     /* list of recipient names parsed out */
{
    const char  *lname;

    lname = idpair_find(&ctl->localnames, name);
    if (!lname && ctl->wildcard)
        lname = name;

    if (lname != (char *)NULL)
    {
        if (outlevel == O_VERBOSE)
            error(0, 0, "mapped %s to local %s", name, lname);
        save_str(xmit_names, -1, lname);
    }
}

void find_server_names(hdr, ctl, xmit_names)
/* parse names out of a RFC822 header into an ID list */
const char *hdr;                /* RFC822 header in question */
struct query *ctl;              /* list of permissible aliases */
struct idlist **xmit_names;     /* list of recipient names parsed out */
{
    if (hdr == (char *)NULL)
        return;
    else
    {
        char    *cp, *lname;

        if ((cp = nxtaddr(hdr)) != (char *)NULL)
            do {
                char    *atsign;

                if ((atsign = strchr(cp, '@')))
                {
                    struct idlist       *idp;

                    /*
                     * Does a trailing segment of the hostname match something
                     * on the localdomains list?  If so, save the whole name
                     * and keep going.
                     */
                    for (idp = ctl->server.localdomains; idp; idp = idp->next)
                    {
                        char    *rhs;

                        rhs = atsign + 1 + (strlen(atsign) - strlen(idp->id));
                        if ((rhs[-1] == '.' || rhs[-1] == '@')
                                        && strcmp(rhs, idp->id) == 0)
                        {
                            if (outlevel == O_VERBOSE)
                                error(0, 0, "passed through %s matching %s", 
                                      cp, idp->id);
                            save_str(xmit_names, -1, cp);
                            continue;
                        }
                    }

                    /*
                     * Check to see if the right-hand part is an alias
                     * or MX equivalent of the mailserver.  If it's
                     * not, skip this name.  If it is, we'll keep
                     * going and try to find a mapping to a client name.
                     */
                    if (!is_host_alias(atsign+1, ctl))
                        continue;
                    atsign[0] = '\0';
                }

                map_name(cp, ctl, xmit_names);
            } while
                ((cp = nxtaddr((char *)NULL)) != (char *)NULL);
    }
}

char *parse_received(struct query *ctl, char *bufp)
/* try to extract */
{
    char *ok;
    static char rbuf[HOSTLEN + USERNAMELEN + 4]; 

    /*
     * Try to extract the real envelope addressee.  We look here
     * specifically for the mailserver's Received line.
     * Note: this will only work for sendmail, or an MTA that
     * shares sendmail's convention for embedding the envelope
     * address in the Received line.  Sendmail itself only
     * does this when the mail has a single recipient.
     */
    if ((ok = strstr(bufp, "by ")) == (char *)NULL)
        ok = (char *)NULL;
    else
    {
        char    *sp, *tp;

        /* extract space-delimited token after "by " */
        for (sp = ok + 3; isspace(*sp); sp++)
            continue;
        tp = rbuf;
        for (; !isspace(*sp); sp++)
            *tp++ = *sp;
        *tp = '\0';

        /*
         * If it's a DNS name of the mail server, look for the
         * recipient name after a following "for".  Otherwise
         * punt.
         */
        if (is_host_alias(rbuf, ctl))
            ok = strstr(sp, "for ");
        else
            ok = (char *)NULL;
    }

    if (ok != 0)
    {
        char    *sp, *tp;

        tp = rbuf;
        sp = ok + 4;
        if (*sp == '<')
            sp++;
        while (*sp && *sp != '>' && *sp != '@' && *sp != ';')
            if (!isspace(*sp))
                *tp++ = *sp++;
            else
            {
                /* uh oh -- whitespace here can't be right! */
                ok = (char *)NULL;
                break;
            }
        *tp = '\0';
    }

    if (!ok)
        return(NULL);
    else
    {
        if (outlevel == O_VERBOSE)
            error(0, 0, "found Received address `%s'", rbuf);
        return(rbuf);
    }
}
#endif /* HAVE_RES_SEARCH */

static FILE *smtp_open(struct query *ctl)
/* try to open a socket to the appropriate SMTP server for this query */ 
{
    struct query *lead;

    lead = ctl->lead_smtp; /* go to the SMTP leader for this query */

    /* maybe it's time to close the socket in order to force delivery */
    if (batchlimit && lead->smtp_sockfp && batchcount++ == batchlimit)
    {
        fclose(lead->smtp_sockfp);
        lead->smtp_sockfp = (FILE *)NULL;
        batchcount = 0;
    }

    /* 
     * RFC 1123 requires that the domain name in HELO address is a
     * "valid principal domain name" for the client host.  We
     * 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).
     */

    /* if no socket to this host is already set up, try to open ESMTP */
    if (lead->smtp_sockfp == (FILE *)NULL)
    {
        if ((lead->smtp_sockfp = SockOpen(lead->smtphost, SMTP_PORT)) == (FILE *)NULL)
            return((FILE *)NULL);
        else if (SMTP_ok(lead->smtp_sockfp) != SM_OK
                 || SMTP_ehlo(lead->smtp_sockfp, 
                              ctl->server.names->id,
                              &lead->server.esmtp_options) != SM_OK)
        {
            /*
             * 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.
             */
            fclose(lead->smtp_sockfp);
            lead->smtp_sockfp = (FILE *)NULL;
        }
    }

    /* if opening for ESMTP failed, try SMTP */
    if (lead->smtp_sockfp == (FILE *)NULL)
    {
        if ((lead->smtp_sockfp = SockOpen(lead->smtphost, SMTP_PORT)) == (FILE *)NULL)
            return((FILE *)NULL);
        else if (SMTP_ok(lead->smtp_sockfp) != SM_OK
                 || SMTP_helo(lead->smtp_sockfp, ctl->server.names->id) != SM_OK)
        {
            fclose(lead->smtp_sockfp);
            lead->smtp_sockfp = (FILE *)NULL;
        }
    }

    return(lead->smtp_sockfp);
}

static int gen_readmsg(sockfp, len, delimited, ctl, realname)
/* read message content and ship to SMTP or MDA */
FILE *sockfp;           /* to which the server is connected */
long len;               /* length of message */
int delimited;          /* does the protocol use a message delimiter? */
struct query *ctl;      /* query control record */
char *realname;         /* real name of host */
{
    char buf [MSGBUFSIZE+1]; 
    int from_offs, to_offs, cc_offs, bcc_offs, ctt_offs, env_offs;
    char *headers, *received_for;
    int n, oldlen, ch, sizeticker, delete_ok;
    FILE *sinkfp;
    RETSIGTYPE (*sigchld)();
#ifdef HAVE_GETHOSTBYNAME
    char rbuf[HOSTLEN + USERNAMELEN + 4]; 
#endif /* HAVE_GETHOSTBYNAME */
    char                *cp;
    struct idlist       *idp, *xmit_names;
    int                 good_addresses, bad_addresses;
#ifdef HAVE_RES_SEARCH
    int                 no_local_matches = FALSE;
#endif /* HAVE_RES_SEARCH */

    sizeticker = 0;
    delete_ok = TRUE;

    /* read message headers */
    headers = received_for = NULL;
    from_offs = to_offs = cc_offs = bcc_offs = ctt_offs = env_offs = -1;
    oldlen = 0;
    for (;;)
    {
        char *line;

        line = xmalloc(sizeof(buf));
        line[0] = '\0';
        do {
            if (!SockGets(buf, sizeof(buf)-1, sockfp))
                return(PS_SOCKET);
            vtalarm(ctl->server.timeout);
            /* leave extra room for reply_hack to play with */
            line = realloc(line, strlen(line) + strlen(buf) + HOSTLEN + 1);
            strcat(line, buf);
            if (line[0] == '\r' && line[1] == '\n')
                break;
        } while
            /* we may need to grab RFC822 continuations */
            ((ch = SockPeek(sockfp)) == ' ' || ch == '\t');

        /* write the message size dots */
        if ((outlevel>O_SILENT && outlevel<O_VERBOSE) && (n=strlen(line)) > 0)
        {
            sizeticker += n;
            while (sizeticker >= SIZETICKER)
            {
                error_build(".");
                sizeticker -= SIZETICKER;
            }
        }
        len -= n;

        /* check for end of headers; don't save terminating line */
        if (line[0] == '\r' && line[1] == '\n')
        {
            free(line);
            break;
        }
     
        if (ctl->rewrite)
            reply_hack(line, realname);

        if (!headers)
        {
            oldlen = strlen(line);
            headers = xmalloc(oldlen + 1);
            (void) strcpy(headers, line);
            free(line);
            line = headers;
        }
        else
        {
            int newlen;

            newlen = oldlen + strlen(line);
            headers = realloc(headers, newlen + 1);
            if (headers == NULL)
                return(PS_IOERR);
            strcpy(headers + oldlen, line);
            free(line);
            line = headers + oldlen;
            oldlen = newlen;
        }

        if (from_offs == -1 && !strncasecmp("From:", line, 5))
            from_offs = (line - headers);
        else if (from_offs == -1 && !strncasecmp("Resent-From:", line, 12))
            from_offs = (line - headers);
        else if (from_offs == -1 && !strncasecmp("Apparently-From:", line, 16))
            from_offs = (line - headers);

        else if (!strncasecmp("To:", line, 3))
            to_offs = (line - headers);

        else if (env_offs == -1 && !strncasecmp(ctl->server.envelope,
                                                line,
                                                strlen(ctl->server.envelope)))
            env_offs = (line - headers);

        else if (!strncasecmp("Cc:", line, 3))
            cc_offs = (line - headers);

        else if (!strncasecmp("Bcc:", line, 4))
            bcc_offs = (line - headers);

        else if (!strncasecmp("Content-Transfer-Encoding:", line, 26))
            ctt_offs = (line - headers);

#ifdef HAVE_RES_SEARCH
        else if (MULTIDROP(ctl) && !received_for && !strncasecmp("Received:", line, 9))
            received_for = parse_received(ctl, line);
#endif /* HAVE_RES_SEARCH */
    }

    /*
     * Hack time.  If the first line of the message was blank, with no headers
     * (this happens occasionally due to bad gatewaying software) cons up
     * a set of fake headers.  
     *
     * If you modify the fake header template below, be sure you don't
     * make either From or To address @-less, otherwise the reply_hack
     * logic will do bad things.
     */
    if (headers == (char *)NULL)
    {
        sprintf(buf, 
        "From: <FETCHMAIL-DAEMON@%s>\r\nTo: %s@localhost\r\nSubject: Headerless mail from %s's mailbox on %s\r\n",
                fetchmailhost, user, ctl->remotename, realname);
        headers = xstrdup(buf);
    }

    /*
     * We can now process message headers before reading the text.
     * In fact we have to, as this will tell us where to forward to.
     */

    /* cons up a list of local recipients */
    xmit_names = (struct idlist *)NULL;
    bad_addresses = good_addresses = 0;
#ifdef HAVE_RES_SEARCH
    /* is this a multidrop box? */
    if (MULTIDROP(ctl))
    {
        if (env_offs > -1)          /* We have the actual envelope addressee */
            find_server_names(headers + env_offs, ctl, &xmit_names);
        else if (received_for)
            /*
             * We have the Received for addressee.  
             * It has to be a mailserver address, or we
             * wouldn't have got here.
             */
            map_name(received_for, ctl, &xmit_names);
        else
        {
            /*
             * We haven't extracted the envelope address.
             * So check all the header addresses.
             */
            if (to_offs > -1)
                find_server_names(headers + to_offs,  ctl, &xmit_names);
            if (cc_offs > -1)
                find_server_names(headers + cc_offs,  ctl, &xmit_names);
            if (bcc_offs > -1)
                find_server_names(headers + bcc_offs, ctl, &xmit_names);
        }
        if (!xmit_names)
        {
            no_local_matches = TRUE;
            save_str(&xmit_names, -1, user);
            if (outlevel == O_VERBOSE)
                error(0, 0, 
                      "no local matches, forwarding to %s",
                      user);
        }
    }
    else        /* it's a single-drop box, use first localname */
#endif /* HAVE_RES_SEARCH */
        save_str(&xmit_names, -1, ctl->localnames->id);

    /* time to address the message */
    if (ctl->mda)       /* we have a declared MDA */
    {
        int     length = 0;
        char    *names, *cmd;

        /*
         * We go through this in order to be able to handle very
         * long lists of users and (re)implement %s.
         */
        for (idp = xmit_names; idp; idp = idp->next)
            length += (strlen(idp->id) + 1);
        names = (char *)alloca(length);
        names[0] = '\0';
        for (idp = xmit_names; idp; idp = idp->next)
        {
            strcat(names, idp->id);
            strcat(names, " ");
        }
        cmd = (char *)alloca(strlen(ctl->mda) + length);
        sprintf(cmd, ctl->mda, names);
        if (outlevel == O_VERBOSE)
            error(0, 0, "about to deliver with: %s", cmd);

#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(cmd, "w");

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

        if (!sinkfp)
        {
            error(0, 0, "MDA open failed");
            return(PS_IOERR);
        }

        sigchld = signal(SIGCHLD, SIG_DFL);
    }
    else
    {
        char    *ap, *ctt, options[MSGBUFSIZE];
        int     smtperr;

        /* build a connection to the SMTP listener */
        if (!ctl->mda && ((sinkfp = smtp_open(ctl)) == NULL))
        {
            free_str_list(&xmit_names);
            error(0, 0, "SMTP connect failed");
            return(PS_SMTP);
        }

        /*
         * Compute ESMTP options.  It's a kluge to use nxtaddr()
         * here because the contents of the Content-Transfer-Encoding
         * headers isn't semantically an address.  But it has the
         * desired tokenizing effect.
         */
        options[0] = '\0';
        if ((ctl->server.esmtp_options & ESMTP_8BITMIME)
            && (ctt_offs >= 0)
            && (ctt = nxtaddr(headers + ctt_offs)))
            if (!strcasecmp(ctt,"7BIT"))
                sprintf(options, " BODY=7BIT", ctt);
            else if (!strcasecmp(ctt,"8BIT"))
                sprintf(options, " BODY=8BITMIME", ctt);
        if ((ctl->server.esmtp_options & ESMTP_SIZE) && !delimited)
            sprintf(options + strlen(options), " SIZE=%d", len);

        /*
         * Try to get the SMTP listener to take the header
         * From address as MAIL FROM (this makes the logging
         * nicer).  If it won't, fall back on the calling-user
         * ID.  This won't affect replies, which use the header
         * From address anyway.
         *
         * 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 From
         * 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 lines, *and*
         * the local SMTP listener insists on them.
         */
        if (from_offs == -1 || !(ap = nxtaddr(headers + from_offs)))
            ap = user;
        if (SMTP_from(sinkfp, ap, options) != SM_OK)
        {
            int smtperr = atoi(smtp_response);

            if (smtperr >= 400)
                error(0, 0, "SMTP error: %s", smtp_response);

            /*
             * There'a one problem with this flow of control;
             * there's no way to avoid reading the whole message
             * off the server, even if the MAIL FROM response 
             * tells us that it's just to be discarded.  We could
             * fix this under IMAP by reading headers first, then
             * trying to issue the MAIL FROM, and *then* reading
             * the body...but POP3 can't do this.
             */

            switch (smtperr)
            {
            case 571: /* unsolicited email refused */
                /*
                 * 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.
                 */
                sinkfp = (FILE *)NULL;
                goto skiptext;

            case 452: /* insufficient system storage */
                /*
                 * Temporary out-of-queue-space condition on the
                 * ESMTP server.  Don't try to ship the message, 
                 * and suppress deletion so it can be retried on
                 * a future retrieval cycle.
                 */
                delete_ok = FALSE;
                sinkfp = (FILE *)NULL;
                SMTP_rset(sockfp);      /* required by RFC1870 */
                goto skiptext;

            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.
                 */
                sinkfp = (FILE *)NULL;
                SMTP_rset(sockfp);      /* required by RFC1870 */
                goto skiptext;

            default:    /* retry with invoking user's address */
                if (SMTP_from(sinkfp, user, options) != SM_OK)
                {
                    error(0,0,"SMTP error: %s", smtp_response);
                    return(PS_SMTP);    /* should never happen */
                }
            }
        }

        /*
         * Now list the recipient addressees
         *
         * 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.  RFC1123 doesn't say whether
         * the FQDN part can be null (as it frequently will be
         * here), but it's hard to see how this could cause a
         * problem.
         */
        for (idp = xmit_names; idp; idp = idp->next)
            if (SMTP_rcpt(sinkfp, idp->id) == SM_OK)
                good_addresses++;
            else
            {
                bad_addresses++;
                idp->val.num = 0;
                error(0, 0, 
                      "SMTP listener doesn't like recipient address `%s'", idp->id);
            }
        if (!good_addresses && SMTP_rcpt(sinkfp, user) != SM_OK)
        {
            error(0, 0, 
                  "can't even send to calling user!");
            return(PS_SMTP);
        }

        /* tell it we're ready to send data */
        SMTP_data(sinkfp);

    skiptext:;
    }

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

        for (sp = tp = headers; *sp; sp++)
            if (*sp != '\r')
                *tp++ =  *sp;
        *tp = '\0';

    }

    /* write all the headers */
    if (sinkfp)
    {
        if (ctl->mda)
            n = fwrite(headers, 1, strlen(headers), sinkfp);
        else
            n = SockWrite(headers, 1, strlen(headers), sinkfp);

        if (n < 0)
        {
            free(headers);
            headers = NULL;
            error(0, errno, "writing RFC822 headers");
            if (ctl->mda)
            {
                pclose(sinkfp);
                signal(SIGCHLD, sigchld);
            }
            return(PS_IOERR);
        }
        else if (outlevel == O_VERBOSE)
            fputs("#", stderr);
    }
    free(headers);
    headers = NULL;

    /* write error notifications */
#ifdef HAVE_RES_SEARCH
    if (no_local_matches || bad_addresses)
#else
    if (bad_addresses)
#endif /* HAVE_RES_SEARCH */
    {
        int     errlen = 0;
        char    errhd[USERNAMELEN + POPBUFSIZE], *errmsg;

        errmsg = errhd;
        (void) strcpy(errhd, "X-Fetchmail-Warning: ");
#ifdef HAVE_RES_SEARCH
        if (no_local_matches)
        {
            strcat(errhd, "no recipient addresses matched declared local names");
            if (bad_addresses)
                strcat(errhd, "; ");
        }
#endif /* HAVE_RES_SEARCH */

        if (bad_addresses)
        {
            strcat(errhd, "SMTP listener rejected local recipient addresses: ");
            errlen = strlen(errhd);
            for (idp = xmit_names; idp; idp = idp->next)
                if (!idp->val.num)
                    errlen += strlen(idp->id) + 2;

            errmsg = alloca(errlen+3);
            (void) strcpy(errmsg, errhd);
            for (idp = xmit_names; idp; idp = idp->next)
                if (!idp->val.num)
                {
                    strcat(errmsg, idp->id);
                    if (idp->next)
                        strcat(errmsg, ", ");
                }
        }

        strcat(errmsg, "\n");

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

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

        /* ship out the error line */
        if (sinkfp)
        {
            if (ctl->mda)
                fwrite(errmsg, 1, strlen(errmsg), sinkfp);
            else
                SockWrite(errmsg, 1, strlen(errmsg), sinkfp);
        }
    }

    free_str_list(&xmit_names);

    /* issue the delimiter line */
    if (sinkfp)
    {
        if (ctl->mda)
            fputc('\n', sinkfp);
        else
            SockWrite("\r\n", 1, 2, sinkfp);
    }

    /*
     *  Body processing starts here
     */

    /* pass through the text lines */
    while (delimited || len > 0)
    {
        if (!SockGets(buf, sizeof(buf)-1, sockfp))
            return(PS_SOCKET);
        vtalarm(ctl->server.timeout);

        /* write the message size dots */
        if ((n = strlen(buf)) > 0)
        {
            sizeticker += n;
            while (sizeticker >= SIZETICKER)
            {
                if (outlevel > O_SILENT)
                    error_build(".");
                sizeticker -= SIZETICKER;
            }
        }
        len -= n;

        /* check for end of message */
        if (delimited && *buf == '.')
            if (buf[1] == '\r' && buf[2] == '\n')
                break;

        /* ship out the text line */
        if (sinkfp)
        {
            /* SMTP byte-stuffing */
            if (*buf == '.')
                if (ctl->mda)
                    fputs(".", sinkfp);
                else
                    SockWrite(buf, 1, 1, sinkfp);

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

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

            /* ship the text line */
            if (ctl->mda)
                n = fwrite(buf, 1, strlen(buf), sinkfp);
            else if (sinkfp)
                n = SockWrite(buf, 1, strlen(buf), sinkfp);

            if (n < 0)
            {
                error(0, errno, "writing message text");
                if (ctl->mda)
                {
                    pclose(sinkfp);
                    signal(SIGCHLD, sigchld);
                }
                return(PS_IOERR);
            }
            else if (outlevel == O_VERBOSE)
                fputc('*', stderr);
        }
    }

    /*
     * End-of-message processing starts here
     */

    if (outlevel == O_VERBOSE)
        fputc('\n', stderr);

    if (ctl->mda)
    {
        int rc;

        /* close the delivery pipe, we'll reopen before next message */
        rc = pclose(sinkfp);
        signal(SIGCHLD, sigchld);
        if (rc)
        {
            error(0, 0, "MDA exited abnormally or returned nonzero status");
            return(PS_IOERR);
        }
    }
    else if (sinkfp)
    {
        /* write message terminator */
        if (SMTP_eom(sinkfp) != SM_OK)
        {
            error(0, 0, "SMTP listener refused delivery");
            return(PS_TRANSIENT);
        }
    }

    return(delete_ok ? PS_SUCCESS : PS_TRANSIENT);
}

#ifdef KERBEROS_V4
int
kerberos_auth (socket, canonical) 
/* authenticate to the server host using Kerberos V4 */
int socket;             /* socket to server host */
const char *canonical;  /* server name */
{
    char * host_primary;
    KTEXT ticket;
    MSG_DAT msg_data;
    CREDENTIALS cred;
    Key_schedule schedule;
    int rem;
  
    ticket = ((KTEXT) (malloc (sizeof (KTEXT_ST))));
    rem = (krb_sendauth (0L, socket, ticket, "pop",
                         canonical,
                         ((char *) (krb_realmofhost (canonical))),
                         ((unsigned long) 0),
                         (&msg_data),
                         (&cred),
                         (schedule),
                         ((struct sockaddr_in *) 0),
                         ((struct sockaddr_in *) 0),
                         "KPOPV0.1"));
    free (ticket);
    if (rem != KSUCCESS)
    {
        error(0, 0, "kerberos error %s", (krb_get_err_text (rem)));
        return (PS_ERROR);
    }
    return (0);
}
#endif /* KERBEROS_V4 */

int do_protocol(ctl, proto)
/* retrieve messages from server using given protocol method table */
struct query *ctl;              /* parsed options with merged-in defaults */
const struct method *proto;     /* protocol method table */
{
    int ok, js, pst;
    char *msg, *sp, *cp, realname[HOSTLEN];
    void (*sigsave)();

#ifndef KERBEROS_V4
    if (ctl->server.authenticate == A_KERBEROS)
    {
        error(0, 0, "Kerberos support not linked.");
        return(PS_ERROR);
    }
#endif /* KERBEROS_V4 */

    /* lacking methods, there are some options that may fail */
    if (!proto->is_old)
    {
        /* check for unsupported options */
        if (ctl->flush) {
            error(0, 0,
                    "Option --flush is not supported with %s",
                    proto->name);
            return(PS_SYNTAX);
        }
        else if (ctl->fetchall) {
            error(0, 0,
                    "Option --all is not supported with %s",
                    proto->name);
            return(PS_SYNTAX);
        }
    }
    if (!proto->getsizes && ctl->limit)
    {
        error(0, 0,
                "Option --limit is not supported with %s",
                proto->name);
        return(PS_SYNTAX);
    }

    protocol = proto;
    tagnum = 0;
    tag[0] = '\0';      /* nuke any tag hanging out from previous query */
    ok = 0;
    error_init(poll_interval == 0 && !logfile);

    /* set up the server-nonresponse timeout */
    sigsave = signal(SIGVTALRM, vtalarm_handler);
    vtalarm(mytimeout = ctl->server.timeout);

    if ((js = setjmp(restart)) == 1)
    {
        error(0, 0,
                "timeout after %d seconds waiting for %s.",
                ctl->server.timeout, ctl->server.names->id);
        ok = PS_ERROR;
    }
    else if (js == 2)
    {
        /* error message printed at point of longjmp */
        ok = PS_ERROR;
    }
    else
    {
        char buf [POPBUFSIZE+1];
        int *msgsizes, len, num, count, new, deletions = 0;
        FILE *sockfp; 
        /* execute pre-initialization command, if any */
        if (ctl->preconnect && (ok = system(ctl->preconnect)))
        {
            sprintf(buf, "pre-connection command failed with status %d", ok);
            error(0, 0, buf);
            ok = PS_SYNTAX;
            goto closeUp;
        }

        /* open a socket to the mail server */
        if (!(sockfp = SockOpen(ctl->server.names->id,
                     ctl->server.port ? ctl->server.port : protocol->port)))
        {
#ifndef EHOSTUNREACH
#define EHOSTUNREACH (-1)
#endif
            if (errno != EHOSTUNREACH)
                error(0, errno, "connecting to host");
            ok = PS_SOCKET;
            goto closeUp;
        }

#ifdef KERBEROS_V4
        if (ctl->authenticate == A_KERBEROS)
        {
            ok = kerberos_auth(fileno(sockfp), ctl->server.canonical_name);
            if (ok != 0)
                goto cleanUp;
            vtalarm(ctl->server.timeout);
        }
#endif /* KERBEROS_V4 */

        /* accept greeting message from mail server */
        ok = (protocol->parse_response)(sockfp, buf);
        if (ok != 0)
            goto cleanUp;
        vtalarm(ctl->server.timeout);

        /*
         * Try to parse the host's actual name out of the greeting
         * message.  We do this so that the progress messages will
         * make sense even if the connection is indirected through
         * ssh. *Do* use this for hacking reply headers, but *don't*
         * use it for error logging, as the names in the log should
         * correlate directly back to rc file entries.
         *
         * This assumes that the first space-delimited token found
         * that contains at least two dots (with the characters on
         * each side of the dot alphanumeric to exclude version
         * numbers) is the hostname.  The hostname candidate may not
         * contain @ -- if it does it's probably a mailserver
         * maintainer's name.  If no such token is found, fall back on
         * the .fetchmailrc id.
         */
        pst = 0;
        for (cp = buf; *cp; cp++)
        {
            switch (pst)
            {
            case 0:             /* skip to end of current token */
                if (*cp == ' ')
                    pst = 1;
                break;

            case 1:             /* look for blank-delimited token */
                if (*cp != ' ')
                {
                    sp = cp;
                    pst = 2;
                }
                break;

            case 2:             /* look for first dot */
                if (*cp == '@')
                    pst = 0;
                else if (*cp == ' ')
                    pst = 1;
                else if (*cp == '.' && isalpha(cp[1]) && isalpha(cp[-1]))
                    pst = 3;
                break;

            case 3:             /* look for second dot */
                if (*cp == '@')
                    pst = 0;
                else if (*cp == ' ')
                    pst = 1;
                else if (*cp == '.' && isalpha(cp[1]) && isalpha(cp[-1]))
                    pst = 4;
                break;

            case 4:             /* look for trailing space */
                if (*cp == '@')
                    pst = 0;
                else if (*cp == ' ')
                {
                    pst = 5;
                    goto done;
                }
                break;
            }
        }
    done:
        if (pst == 5)
        {
            char        *tp = realname;

            while (sp < cp)
                *tp++ = *sp++;
            *tp = '\0';
        }
        else
            strcpy(realname, ctl->server.names->id);

        /* try to get authorized to fetch mail */
        if (protocol->getauth)
        {
            shroud = ctl->password;
            ok = (protocol->getauth)(sockfp, ctl, buf);
            shroud = (char *)NULL;
            if (ok == PS_ERROR)
                ok = PS_AUTHFAIL;
            if (ok != 0)
            {
                error(0, 0, "Authorization failure on %s@%s", 
                      ctl->remotename,
                      realname);
                goto cleanUp;
            }
            vtalarm(ctl->server.timeout);
        }

        /* compute number of messages and number of new messages waiting */
        ok = (protocol->getrange)(sockfp, ctl, &count, &new);
        if (ok != 0)
            goto cleanUp;
        vtalarm(ctl->server.timeout);

        /* show user how many messages we downloaded */
        if (outlevel > O_SILENT)
            if (count == -1)                    /* only used for ETRN */
                error(0, 0, "Polling %s@%s", 
                        ctl->remotename,
                        realname);
            else if (count == 0)
                error(0, 0, "No mail at %s@%s", 
                        ctl->remotename,
                        realname);
            else
            {
                if (new != -1 && (count - new) > 0)
                    error(0, 0, "%d message%s (%d seen) at %s@%s.",
                                count, count > 1 ? "s" : "", count-new,
                                ctl->remotename,
                                realname);
                else
                    error(0, 0, "%d message%s at %s@%s.", 
                                count, count > 1 ? "s" : "",
                                ctl->remotename,
                                realname);
            }

        /* we may need to get sizes in order to check message limits */
        msgsizes = (int *)NULL;
        if (!ctl->fetchall && proto->getsizes && ctl->limit)
        {
            msgsizes = (int *)alloca(sizeof(int) * count);

            ok = (proto->getsizes)(sockfp, count, msgsizes);
            if (ok != 0)
                goto cleanUp;
            vtalarm(ctl->server.timeout);
        }

        if (check_only)
        {
            if (new == -1 || ctl->fetchall)
                new = count;
            ok = ((new > 0) ? PS_SUCCESS : PS_NOMAIL);
            goto cleanUp;
        }
        else if (count > 0)
        {    
            int force_retrieval, fetches;

            /*
             * What forces this code is that in POP3 and IMAP2BIS you can't
             * fetch a message without having it marked `seen'.  In IMAP4,
             * on the other hand, you can (peek_capable is set to convey
             * this).
             *
             * The result of being unable to peek is that if there's
             * any kind of transient error (DNS lookup failure, or
             * sendmail refusing delivery due to process-table limits)
             * the message will be marked "seen" on the server without
             * having been delivered.  This is not a big problem if
             * fetchmail is running in foreground, because the user
             * will see a "skipped" message when it next runs and get
             * clued in.
             *
             * But in daemon mode this leads to the message being silently
             * ignored forever.  This is not acceptable.
             *
             * We compensate for this by checking the error count from the 
             * previous pass and forcing all messages to be considered new
             * if it's nonzero.
             */
            force_retrieval = !peek_capable && (ctl->errcount > 0);

            ctl->errcount = fetches = 0;

            /* read, forward, and delete messages */
            for (num = 1; num <= count; num++)
            {
                int     toolarge = msgsizes && (msgsizes[num-1] > ctl->limit);
                int     fetch_it = ctl->fetchall ||
                    (!toolarge && (force_retrieval || !(protocol->is_old && (protocol->is_old)(sockfp,ctl,num))));
                int     suppress_delete = FALSE;

                /* we may want to reject this message if it's old */
                if (!fetch_it)
                {
                    if (outlevel > O_SILENT)
                    {
                        error_build("skipping message %d", num);
                        if (toolarge)
                            error_build(" (oversized, %d bytes)", msgsizes[num-1]);
                    }
                }
                else
                {
                    /* request a message */
                    ok = (protocol->fetch)(sockfp, ctl, num, &len);
                    if (ok != 0)
                        goto cleanUp;
                    vtalarm(ctl->server.timeout);

                    if (outlevel > O_SILENT)
                    {
                        error_build("reading message %d", num);
                        if (len > 0)
                            error_build(" (%d bytes)", len);
                        if (outlevel == O_VERBOSE)
                            error_complete(0, 0, "");
                        else
                            error_build(" ");
                    }

                    /* read the message and ship it to the output sink */
                    ok = gen_readmsg(sockfp,
                                     len, 
                                     protocol->delimited,
                                     ctl,
                                     realname);
                    if (ok == PS_TRANSIENT)
                        suppress_delete = TRUE;
                    else if (ok)
                        goto cleanUp;
                    vtalarm(ctl->server.timeout);

                    /* tell the server we got it OK and resynchronize */
                    if (protocol->trail)
                    {
                        ok = (protocol->trail)(sockfp, ctl, num);
                        if (ok != 0)
                            goto cleanUp;
                        vtalarm(ctl->server.timeout);
                    }

                    fetches++;
                }

                /*
                 * At this point in flow of control, either we've bombed
                 * on a protocol error or had delivery refused by the SMTP
                 * server (unlikely -- I've never seen it) or we've seen
                 * `accepted for delivery' and the message is shipped.
                 * It's safe to mark the message seen and delete it on the
                 * server now.
                 */

                /* maybe we delete this message now? */
                if (protocol->delete
                    && !suppress_delete
                    && (fetch_it ? !ctl->keep : ctl->flush))
                {
                    deletions++;
                    if (outlevel > O_SILENT) 
                        error_complete(0, 0, " flushed");
                    ok = (protocol->delete)(sockfp, ctl, num);
                    if (ok != 0)
                        goto cleanUp;
                    vtalarm(ctl->server.timeout);
                    delete_str(&ctl->newsaved, num);
                }
                else if (outlevel > O_SILENT) 
                    error_complete(0, 0, " not flushed");

                /* perhaps this as many as we're ready to handle */
                if (ctl->fetchlimit && ctl->fetchlimit <= fetches)
                    break;
            }

            ok = gen_transact(sockfp, protocol->exit_cmd);
            if (ok == 0)
                ok = PS_SUCCESS;
            vtalarm(0);
            fclose(sockfp);
            goto closeUp;
        }
        else {
            ok = gen_transact(sockfp, protocol->exit_cmd);
            if (ok == 0)
                ok = PS_NOMAIL;
            vtalarm(0);
            fclose(sockfp);
            goto closeUp;
        }

    cleanUp:
        vtalarm(ctl->server.timeout);
        if (ok != 0 && ok != PS_SOCKET)
            gen_transact(sockfp, protocol->exit_cmd);
        vtalarm(0);
        fclose(sockfp);
    }

    switch (ok)
    {
    case PS_SOCKET:
        msg = "socket";
        break;
    case PS_AUTHFAIL:
        msg = "authorization";
        break;
    case PS_SYNTAX:
        msg = "missing or bad RFC822 header";
        break;
    case PS_IOERR:
        msg = "MDA";
        break;
    case PS_ERROR:
        msg = "client/server synchronization";
        break;
    case PS_PROTOCOL:
        msg = "client/server protocol";
        break;
    case PS_SMTP:
        msg = "SMTP transaction";
        break;
    case PS_UNDEFINED:
        error(0, 0, "undefined");
        break;
    }
    if (ok==PS_SOCKET || ok==PS_AUTHFAIL || ok==PS_SYNTAX || ok==PS_IOERR
                || ok==PS_ERROR || ok==PS_PROTOCOL || ok==PS_SMTP)
        error(0, 0, "%s error while fetching from %s", msg, ctl->server.names->id);

closeUp:
    signal(SIGVTALRM, sigsave);
    return(ok);
}

#if defined(HAVE_STDARG_H)
void gen_send(FILE *sockfp, char *fmt, ... )
/* assemble command in printf(3) style and send to the server */
#else
void gen_send(sockfp, fmt, va_alist)
/* assemble command in printf(3) style and send to the server */
FILE *sockfp;           /* socket to which server is connected */
const char *fmt;        /* printf-style format */
va_dcl
#endif
{
    char buf [POPBUFSIZE+1];
    va_list ap;

    if (protocol->tagged)
        (void) sprintf(buf, "%s ", GENSYM);
    else
        buf[0] = '\0';

#if defined(HAVE_STDARG_H)
    va_start(ap, fmt) ;
#else
    va_start(ap);
#endif
    vsprintf(buf + strlen(buf), fmt, ap);
    va_end(ap);

    strcat(buf, "\r\n");
    SockWrite(buf, 1, strlen(buf), sockfp);

    if (outlevel == O_VERBOSE)
    {
        char *cp;

        if (shroud && (cp = strstr(buf, shroud)))
        {
            char        *sp;

            sp = cp + strlen(shroud);
            *cp++ = '*';
            while (*sp)
                *cp++ = *sp++;
            *cp = '\0';
        }
        buf[strlen(buf)-2] = '\0';
        error(0, 0, "%s> %s", protocol->name, buf);
    }
}

int gen_recv(sockfp, buf, size)
/* get one line of input from the server */
FILE *sockfp;   /* socket to which server is connected */
char *buf;      /* buffer to receive input */
int size;       /* length of buffer */
{
    if (!SockGets(buf, size, sockfp))
        return(PS_SOCKET);
    else
    {
        if (buf[strlen(buf)-1] == '\n')
            buf[strlen(buf)-1] = '\0';
        if (buf[strlen(buf)-1] == '\r')
            buf[strlen(buf)-1] = '\r';
        if (outlevel == O_VERBOSE)
            error(0, 0, "%s< %s", protocol->name, buf);
        return(PS_SUCCESS);
    }
}

#if defined(HAVE_STDARG_H)
int gen_transact(FILE *sockfp, char *fmt, ... )
/* assemble command in printf(3) style, send to server, accept a response */
#else
int gen_transact(sockfp, fmt, va_alist)
/* assemble command in printf(3) style, send to server, accept a response */
FILE *sockfp;           /* socket to which server is connected */
const char *fmt;        /* printf-style format */
va_dcl
#endif
{
    int ok;
    char buf [POPBUFSIZE+1];
    va_list ap;

    if (protocol->tagged)
        (void) sprintf(buf, "%s ", GENSYM);
    else
        buf[0] = '\0';

#if defined(HAVE_STDARG_H)
    va_start(ap, fmt) ;
#else
    va_start(ap);
#endif
    vsprintf(buf + strlen(buf), fmt, ap);
    va_end(ap);

    strcat(buf, "\r\n");
    SockWrite(buf, 1, strlen(buf), sockfp);

    if (outlevel == O_VERBOSE)
    {
        char *cp;

        if (shroud && (cp = strstr(buf, shroud)))
        {
            char        *sp;

            sp = cp + strlen(shroud);
            *cp++ = '*';
            while (*sp)
                *cp++ = *sp++;
            *sp = '\0';
        }
        buf[strlen(buf)-1] = '\0';
        error(0, 0, "%s> %s", protocol->name, buf);
    }

    /* we presume this does its own response echoing */
    ok = (protocol->parse_response)(sockfp, buf);
    vtalarm(mytimeout);

    return(ok);
}

/* driver.c ends here */