[~andy/fetchmail] / transact.c

/*
 * transact.c -- transaction primitives for the fetchmail driver loop
 *
 * Copyright 2001 by Eric S. Raymond
 * For license terms, see the file COPYING in this directory.
 *
 * 
 */

#include  "config.h"
#include  <stdio.h>
#include  <string.h>
#include  <ctype.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

#ifdef HAVE_NET_SOCKET_H
#include <net/socket.h>
#endif
#include <sys/socket.h>
#include <netdb.h>
#include "md5.h"

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

/* global variables: please reinitialize them explicitly for proper
 * working in daemon mode */

/* session variables initialized in init_transact() */
int suppress_tags = FALSE;      /* emit tags? */
char tag[TAGLEN];
static int tagnum;
#define GENSYM  (sprintf(tag, "A%04d", ++tagnum % TAGMOD), tag)
static struct method *protocol;
char shroud[PASSWORDLEN*2+3];   /* string to shroud in debug output */

/* session variables initialized in do_session() */
int mytimeout;          /* value of nonreponse timeout */

/* mail variables initialized in readheaders() */
struct msgblk msgblk;
static int accept_count, reject_count;

static void map_name(const char *name, struct query *ctl, struct idlist **xmit_names)
/* add given name to xmit_names if it matches declared localnames */
/*   name:       name to map */
/*   ctl:        list of permissible aliases */
/*   xmit_names: list of recipient names parsed out */
{
    const char  *lname;
    int off = 0;
    
    lname = idpair_find(&ctl->localnames, name+off);
    if (!lname && ctl->wildcard)
        lname = name+off;

    if (lname != (char *)NULL)
    {
        if (outlevel >= O_DEBUG)
            report(stdout, GT_("mapped %s to local %s\n"), name, lname);
        save_str(xmit_names, lname, XMIT_ACCEPT);
        accept_count++;
    }
}

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

        for (cp = nxtaddr((const unsigned char *)hdr);
             cp != NULL;
             cp = nxtaddr(NULL))
        {
            char        *atsign;

            /* 
             * Handle empty address from a To: header containing only 
             * a comment.
             */
            if (!*cp)
                continue;

            /*
             * If the name of the user begins with a qmail virtual
             * domain prefix, ignore the prefix.  Doing this here
             * means qvirtual will work either with ordinary name
             * mapping or with a localdomains option.
             */
            if (ctl->server.qvirtual)
            {
                int sl = strlen(ctl->server.qvirtual);
 
                if (!strncasecmp((char *)cp, ctl->server.qvirtual, sl))
                    cp += sl;
            }

            if ((atsign = strchr((char *)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 + (strlen(atsign) - strlen((char *)idp->id));
                    if (rhs > atsign &&
                        (rhs[-1] == '.' || rhs[-1] == '@') &&
                        strcasecmp(rhs, (char *)idp->id) == 0)
                    {
                        if (outlevel >= O_DEBUG)
                            report(stdout, GT_("passed through %s matching %s\n"), 
                                  cp, idp->id);
                        save_str(xmit_names, (const char *)cp, XMIT_ACCEPT);
                        accept_count++;
                        goto nomap;
                    }
                }

                /* if we matched a local domain, idp != NULL */
                if (!idp)
                {
                    /*
                     * 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))
                    {
                        save_str(xmit_names, cp, XMIT_REJECT);
                        reject_count++;
                        continue;
                    }
                }
                atsign[0] = '\0';
                map_name(cp, ctl, xmit_names);
            nomap:;
            }
        }
    }
}

/*
 * Return zero on a syntactically invalid address, nz on a valid one.
 *
 * This used to be strchr(a, '.'), but it turns out that lines like this
 *
 * Received: from punt-1.mail.demon.net by mailstore for markb@ordern.com
 *          id 938765929:10:27223:2; Fri, 01 Oct 99 08:18:49 GMT
 *
 * are not uncommon.  So now we just check that the following token is
 * not itself an email address.
 */
#define VALID_ADDRESS(a)        !strchr(a, '@')

static char *parse_received(struct query *ctl, char *bufp)
/* try to extract real address from the Received line */
/* If a valid Received: line is found, we return the full address in
 * a buffer which can be parsed from nxtaddr().  This is to ansure that
 * the local domain part of the address can be passed along in 
 * find_server_names() if it contains one.
 * Note: We should return a dummy header containing the address 
 * which makes nxtaddr() behave correctly. 
 */
{
    char *base, *ok = (char *)NULL;
    static char rbuf[HOSTLEN + USERNAMELEN + 4]; 

#define RBUF_WRITE(value) if (tp < rbuf+sizeof(rbuf)-1) *tp++=value

    /*
     * 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 (outlevel >= O_DEBUG)
        report(stdout, GT_("analyzing Received line:\n%s"), bufp);

    /* search for whitepace-surrounded "by" followed by valid address */
    for (base = bufp;  ; base = ok + 2)
    {
        if (!(ok = strstr(base, "by")))
            break;
        else if (!isspace((unsigned char)ok[-1]) || !isspace((unsigned char)ok[2]))
            continue;
        else
        {
            char        *sp, *tp;

            /* extract space-delimited token after "by" */
            for (sp = ok + 2; isspace((unsigned char)*sp); sp++)
                continue;
            tp = rbuf;
            for (; *sp && !isspace((unsigned char)*sp); sp++)
                RBUF_WRITE(*sp);
            *tp = '\0';

            /* look for valid address */
            if (VALID_ADDRESS(rbuf))
                break;
            else
                ok = sp - 1;    /* arrange to skip this token */
        }
    }
    if (ok)
    {
        /*
         * 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))
        {
            if (outlevel >= O_DEBUG)
                report(stdout, 
                      GT_("line accepted, %s is an alias of the mailserver\n"), rbuf);
        }
        else
        {
            if (outlevel >= O_DEBUG)
                report(stdout, 
                      GT_("line rejected, %s is not an alias of the mailserver\n"), 
                      rbuf);
            return(NULL);
        }

        /* search for whitepace-surrounded "for" followed by xxxx@yyyy */
        for (base = ok + 4 + strlen(rbuf);  ; base = ok + 2)
        {
            if (!(ok = strstr(base, "for")))
                break;
            else if (!isspace((unsigned char)ok[-1]) || !isspace((unsigned char)ok[3]))
                continue;
            else
            {
                char    *sp, *tp;

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

                if (strchr(rbuf, '@'))
                    break;
                else
                    ok = sp - 1;        /* arrange to skip this token */
            }
        }
        if (ok)
        {
            flag        want_gt = FALSE;
            char        *sp, *tp;

            /* char after "for" could be space or a continuation newline */
            for (sp = ok + 4; isspace((unsigned char)*sp); sp++)
                continue;
            tp = rbuf;
            RBUF_WRITE(':');    /* Here is the hack.  This is to be friends */
            RBUF_WRITE(' ');    /* with nxtaddr()... */
            if (*sp == '<')
            {
                want_gt = TRUE;
                sp++;
            }
            while (*sp == '@')          /* skip routes */
                while (*sp && *sp++ != ':')
                    continue;
            while (*sp
                   && (want_gt ? (*sp != '>') : !isspace((unsigned char)*sp))
                   && *sp != ';')
                if (!isspace((unsigned char)*sp))
                {
                    RBUF_WRITE(*sp);
                    sp++;
                }    
                else
                {
                    /* uh oh -- whitespace here can't be right! */
                    ok = (char *)NULL;
                    break;
                }
            RBUF_WRITE('\n');
            *tp = '\0';
            if (strlen(rbuf) <= 3)      /* apparently nothing has been found */
                ok = NULL;
        } else
            ok = (char *)NULL;
    }

    if (!ok)
    {
        if (outlevel >= O_DEBUG)
            report(stdout, GT_("no Received address found\n"));
        return(NULL);
    }
    else
    {
        if (outlevel >= O_DEBUG) {
            char *lf = rbuf + strlen(rbuf)-1;
            *lf = '\0';
            if (outlevel >= O_DEBUG)
                report(stdout, GT_("found Received address `%s'\n"), rbuf+2);
            *lf = '\n';
        }
        return(rbuf);
    }
}

/* shared by readheaders and readbody */
static int sizeticker;

#define EMPTYLINE(s)   (((s)[0] == '\r' && (s)[1] == '\n' && (s)[2] == '\0') \
                       || ((s)[0] == '\n' && (s)[1] == '\0'))

static int end_of_header (const char *s)
/* accept "\r*\n" as EOH in order to be bulletproof against broken survers */
{
    while (s[0] == '\r')
        s++;
    return (s[0] == '\n' && s[1] == '\0');
}

int readheaders(int sock,
                       long fetchlen,
                       long reallen,
                       struct query *ctl,
                       int num,
                       flag *suppress_readbody)
/* read message headers and ship to SMTP or MDA */
/*   sock:              to which the server is connected */
/*   fetchlen:          length of message according to fetch response */
/*   reallen:           length of message according to getsizes */
/*   ctl:               query control record */
/*   num:               index of message */
/*   suppress_readbody: whether call to readbody() should be supressed */
{
    struct addrblk
    {
        int             offset;
        struct addrblk  *next;
    };
    struct addrblk      *to_addrchain = NULL;
    struct addrblk      **to_chainptr = &to_addrchain;
    struct addrblk      *resent_to_addrchain = NULL;
    struct addrblk      **resent_to_chainptr = &resent_to_addrchain;

    char                buf[MSGBUFSIZE+1];
    int                 from_offs, reply_to_offs, resent_from_offs;
    int                 app_from_offs, sender_offs, resent_sender_offs;
    int                 env_offs;
    char                *received_for, *rcv, *cp;
    static char         *delivered_to = NULL;
    int                 n, oldlen, ch, remaining, skipcount;
    size_t              linelen;
    int                 delivered_to_count;
    struct idlist       *idp;
    flag                no_local_matches = FALSE;
    flag                has_nuls;
    int                 olderrs, good_addresses, bad_addresses;
    int                 retain_mail = 0, refuse_mail = 0;
    flag                already_has_return_path = FALSE;

    sizeticker = 0;
    has_nuls = FALSE;
    msgblk.return_path[0] = '\0';
    olderrs = ctl->errcount;

    /* read message headers */
    msgblk.reallen = reallen;

    /*
     * We used to free the header block unconditionally at the end of 
     * readheaders, but it turns out that if close_sink() hits an error
     * condition the code for sending bouncemail will actually look
     * at the freed storage and coredump...
     */
    if (msgblk.headers)
       free(msgblk.headers);
    free_str_list(&msgblk.recipients);
    if (delivered_to)
        free(delivered_to);

    /* initially, no message digest */
    memset(ctl->digest, '\0', sizeof(ctl->digest));

    msgblk.headers = received_for = delivered_to = NULL;
    from_offs = reply_to_offs = resent_from_offs = app_from_offs = 
        sender_offs = resent_sender_offs = env_offs = -1;
    oldlen = 0;
    msgblk.msglen = 0;
    skipcount = 0;
    delivered_to_count = 0;
    ctl->mimemsg = 0;

    for (remaining = fetchlen; remaining > 0 || protocol->delimited; )
    {
        char *line, *rline;
        int overlong = FALSE; /* XXX FIXME: this is unused */

        line = xmalloc(sizeof(buf));
        linelen = 0;
        line[0] = '\0';
        do {
            do {
                char    *sp, *tp;

                set_timeout(mytimeout);
                if ((n = SockRead(sock, buf, sizeof(buf)-1)) == -1) {
                    set_timeout(0);
                    free(line);
                    free(msgblk.headers);
                    msgblk.headers = NULL;
                    return(PS_SOCKET);
                }
                set_timeout(0);

                /*
                 * Smash out any NULs, they could wreak havoc later on.
                 * Some network stacks seem to generate these at random,
                 * especially (according to reports) at the beginning of the
                 * first read.  NULs are illegal in RFC822 format.
                 */
                for (sp = tp = buf; sp < buf + n; sp++)
                    if (*sp)
                        *tp++ = *sp;
                *tp = '\0';
                n = tp - buf;
            } while
                  (n == 0);

            remaining -= n;
            linelen += n;
            msgblk.msglen += n;

            /*
             * Try to gracefully handle the case where the length of a
             * line exceeds MSGBUFSIZE.
             */
            if (n && buf[n-1] != '\n') 
            {
                overlong = TRUE;
                rline = (char *) realloc(line, linelen + 1);
                if (rline == NULL)
                {
                    free (line);
                    return(PS_IOERR);
                }
                line = rline;
                memcpy(line + linelen - n, buf, n);
                line[linelen] = '\0';
                ch = ' '; /* So the next iteration starts */
                continue;
            }

            /* lines may not be properly CRLF terminated; fix this for qmail */
            /* we don't want to overflow the buffer here */
            if (ctl->forcecr && buf[n-1]=='\n' && (n==1 || buf[n-2]!='\r'))
            {
                char * tcp;
                rline = (char *) realloc(line, linelen + 2);
                if (rline == NULL)
                {
                    free (line);
                    return(PS_IOERR);
                }
                line = rline;
                memcpy(line + linelen - n, buf, n - 1);
                tcp = line + linelen - 1;
                *tcp++ = '\r';
                *tcp++ = '\n';
                *tcp++ = '\0';
                n++;
                linelen++;
            }
            else
            {
                rline = (char *) realloc(line, linelen + 1);
                if (rline == NULL)
                {
                    free (line);
                    return(PS_IOERR);
                }
                line = rline;
                memcpy(line + linelen - n, buf, n + 1);
            }

            /* check for end of headers */
            if (end_of_header(line))
            {
                if (linelen != strlen (line))
                    has_nuls = TRUE;
                free(line);
                goto process_headers;
            }

            /*
             * Check for end of message immediately.  If one of your folders
             * has been mangled, the delimiter may occur directly after the
             * header.
             */
            if (protocol->delimited && line[0] == '.' && EMPTYLINE(line+1))
            {
                if (outlevel > O_SILENT)
                    report(stdout,
                           GT_("message delimiter found while scanning headers\n"));
                if (suppress_readbody)
                    *suppress_readbody = TRUE;
                if (linelen != strlen (line))
                    has_nuls = TRUE;
                free(line);
                goto process_headers;
            }

            /*
             * At least one brain-dead website (netmind.com) is known to
             * send out robotmail that's missing the RFC822 delimiter blank
             * line before the body! Without this check fetchmail segfaults.
             * With it, we treat such messages as spam and refuse them.
             */
            if (!refuse_mail && !isspace((unsigned char)line[0]) && !strchr(line, ':'))
            {
                if (linelen != strlen (line))
                    has_nuls = TRUE;
                if (outlevel > O_SILENT)
                    report(stdout,
                           GT_("incorrect header line found while scanning headers\n"));
                if (outlevel >= O_VERBOSE)
                    report (stdout, GT_("line: %s"), line);
                refuse_mail = 1;
            }

            /* check for RFC822 continuations */
            set_timeout(mytimeout);
            ch = SockPeek(sock);
            set_timeout(0);
        } while
            (ch == ' ' || ch == '\t');  /* continuation to next line? */

        /* write the message size dots */
        if ((outlevel > O_SILENT && outlevel < O_VERBOSE) && linelen > 0)
        {
            sizeticker += linelen;
            while (sizeticker >= SIZETICKER)
            {
                if (outlevel > O_SILENT && run.showdots && !run.use_syslog)
                {
                    fputc('.', stdout);
                    fflush(stdout);
                }
                sizeticker -= SIZETICKER;
            }
        }
                /*
                 * Decode MIME encoded headers. We MUST do this before
                 * looking at the Content-Type / Content-Transfer-Encoding
                 * headers (RFC 2046).
                 */
                if ( ctl->mimedecode )
                {
                    char *tcp;
                    UnMimeHeader(line);
                    /* the line is now shorter. So we retrace back till we find our terminating
                     * combination \n\0, we move backwards to make sure that we don't catch som
                     * \n\0 stored in the decoded part of the message */
                    for(tcp = line + linelen - 1; tcp > line && (*tcp != 0 || tcp[-1] != '\n'); tcp--);
                    if(tcp > line) linelen = tcp - line;
                }


        /* skip processing if we are going to retain or refuse this mail */
        if (retain_mail || refuse_mail)
        {
            free(line);
            continue;
        }

        /* we see an ordinary (non-header, non-message-delimiter line */
        if (linelen != strlen (line))
            has_nuls = TRUE;

        /*
         * The University of Washington IMAP server (the reference
         * implementation of IMAP4 written by Mark Crispin) relies
         * on being able to keep base-UID information in a special
         * message at the head of the mailbox.  This message should
         * neither be deleted nor forwarded.
         */
#ifdef POP2_ENABLE
        /*
         * We disable this check under POP2 because there's no way to
         * prevent deletion of the message.  So at least we ought to
         * forward it to the user so he or she will have some clue
         * that things have gone awry.
         */
        if (servport("pop2") != servport(protocol->service))
#endif /* POP2_ENABLE */
            if (num == 1 && !strncasecmp(line, "X-IMAP:", 7)) {
                free(line);
                retain_mail = 1;
                continue;
            }

        /*
         * This code prevents fetchmail from becoming an accessory after
         * the fact to upstream sendmails with the `E' option on.  It also
         * copes with certain brain-dead POP servers (like NT's) that pass
         * through Unix from_ lines.
         *
         * Either of these bugs can result in a non-RFC822 line at the
         * beginning of the headers.  If fetchmail just passes it
         * through, the client listener may think the message has *no*
         * headers (since the first) line it sees doesn't look
         * RFC822-conformant) and fake up a set.
         *
         * What the user would see in this case is bogus (synthesized)
         * headers, followed by a blank line, followed by the >From, 
         * followed by the real headers, followed by a blank line,
         * followed by text.
         *
         * We forestall this lossage by tossing anything that looks
         * like an escaped or passed-through From_ line in headers.
         * These aren't RFC822 so our conscience is clear...
         */
        if (!strncasecmp(line, ">From ", 6) || !strncasecmp(line, "From ", 5))
        {
            free(line);
            continue;
        }

        /*
         * We remove all Delivered-To: headers if dropdelivered is set
         * - special care must be taken if Delivered-To: is also used
         * as envelope at the same time.
         *
         * This is to avoid false mail loops errors when delivering
         * local messages to and from a Postfix or qmail mailserver.
         */
        if (ctl->dropdelivered && !strncasecmp(line, "Delivered-To:", 13)) 
        {
            if (delivered_to ||
                ctl->server.envelope == STRING_DISABLED ||
                !ctl->server.envelope ||
                strcasecmp(ctl->server.envelope, "Delivered-To") ||
                delivered_to_count != ctl->server.envskip)
                free(line);
            else 
                delivered_to = line;
            delivered_to_count++;
            continue;
        }

        /*
         * If we see a Status line, it may have been inserted by an MUA
         * on the mail host, or it may have been inserted by the server
         * program after the headers in the transaction stream.  This
         * can actually hose some new-mail notifiers such as xbuffy,
         * which assumes any Status line came from a *local* MDA and
         * therefore indicates that the message has been seen.
         *
         * Some buggy POP servers (including at least the 3.3(20)
         * version of the one distributed with IMAP) insert empty
         * Status lines in the transaction stream; we'll chuck those
         * unconditionally.  Nonempty ones get chucked if the user
         * turns on the dropstatus flag.
         */
        {
            char        *cp;

            if (!strncasecmp(line, "Status:", 7))
                cp = line + 7;
            else if (!strncasecmp(line, "X-Mozilla-Status:", 17))
                cp = line + 17;
            else
                cp = NULL;
            if (cp) {
                while (*cp && isspace((unsigned char)*cp)) cp++;
                if (!*cp || ctl->dropstatus)
                {
                    free(line);
                    continue;
                }
            }
        }

        if (ctl->rewrite)
            line = reply_hack(line, ctl->server.truename, &linelen);

        /*
         * OK, this is messy.  If we're forwarding by SMTP, it's the
         * SMTP-receiver's job (according to RFC821, page 22, section
         * 4.1.1) to generate a Return-Path line on final delivery.
         * The trouble is, we've already got one because the
         * mailserver's SMTP thought *it* was responsible for final
         * delivery.
         *
         * Stash away the contents of Return-Path (as modified by reply_hack)
         * for use in generating MAIL FROM later on, then prevent the header
         * from being saved with the others.  In effect, we strip it off here.
         *
         * If the SMTP server conforms to the standards, and fetchmail gets the
         * envelope sender from the Return-Path, the new Return-Path should be
         * exactly the same as the original one.
         *
         * We do *not* want to ignore empty Return-Path headers.  These should
         * be passed through as a way of indicating that a message should
         * not trigger bounces if delivery fails.  What we *do* need to do is
         * make sure we never try to rewrite such a blank Return-Path.  We
         * handle this with a check for <> in the rewrite logic above.
         *
         * Also, if an email has multiple Return-Path: headers, we only
         * read the first occurance, as some spam email has more than one
         * Return-Path.
         *
         */
        if ((already_has_return_path==FALSE) && !strncasecmp("Return-Path:", line, 12) && (cp = nxtaddr(line)))
        {
            already_has_return_path = TRUE;
            if (cp[0]=='\0')    /* nxtaddr() strips the brackets... */
                cp="<>";
            strncpy(msgblk.return_path, cp, sizeof(msgblk.return_path));
            msgblk.return_path[sizeof(msgblk.return_path)-1] = '\0';
            if (!ctl->mda) {
                free(line);
                continue;
            }
        }

        if (!msgblk.headers)
        {
            oldlen = linelen;
            msgblk.headers = xmalloc(oldlen + 1);
            (void) memcpy(msgblk.headers, line, linelen);
            msgblk.headers[oldlen] = '\0';
            free(line);
            line = msgblk.headers;
        }
        else
        {
            char *newhdrs;
            int newlen;

            newlen = oldlen + linelen;
            newhdrs = (char *) realloc(msgblk.headers, newlen + 1);
            if (newhdrs == NULL) {
                free(line);
                return(PS_IOERR);
            }
            msgblk.headers = newhdrs;
            memcpy(msgblk.headers + oldlen, line, linelen);
            msgblk.headers[newlen] = '\0';
            free(line);
            line = msgblk.headers + oldlen;
            oldlen = newlen;
        }

        /* find offsets of various special headers */
        if (!strncasecmp("From:", line, 5))
            from_offs = (line - msgblk.headers);
        else if (!strncasecmp("Reply-To:", line, 9))
            reply_to_offs = (line - msgblk.headers);
        else if (!strncasecmp("Resent-From:", line, 12))
            resent_from_offs = (line - msgblk.headers);
        else if (!strncasecmp("Apparently-From:", line, 16))
            app_from_offs = (line - msgblk.headers);
        /*
         * Netscape 4.7 puts "Sender: zap" in mail headers.  Perverse...
         *
         * But a literal reading of RFC822 sec. 4.4.2 supports the idea
         * that Sender: *doesn't* have to be a working email address.
         *
         * The definition of the Sender header in RFC822 says, in
         * part, "The Sender mailbox specification includes a word
         * sequence which must correspond to a specific agent (i.e., a
         * human user or a computer program) rather than a standard
         * address."  That implies that the contents of the Sender
         * field don't need to be a legal email address at all So
         * ignore any Sender or Resent-Sender lines unless they
         * contain @.
         *
         * (RFC2822 says the contents of Sender must be a valid mailbox
         * address, which is also what RFC822 4.4.4 implies.)
         */
        else if (!strncasecmp("Sender:", line, 7) && (strchr(line, '@') || strchr(line, '!')))
            sender_offs = (line - msgblk.headers);
        else if (!strncasecmp("Resent-Sender:", line, 14) && (strchr(line, '@') || strchr(line, '!')))
            resent_sender_offs = (line - msgblk.headers);

#ifdef __UNUSED__
        else if (!strncasecmp("Message-Id:", line, 11))
        {
            if (ctl->server.uidl)
            {
                char id[IDLEN+1];

                line[IDLEN+12] = 0;             /* prevent stack overflow */
                sscanf(line+12, "%s", id);
                if (!str_find( &ctl->newsaved, num))
                {
                    struct idlist *new = save_str(&ctl->newsaved,id,UID_SEEN);
                    new->val.status.num = num;
                }
            }
        }
#endif /* __UNUSED__ */

        /* if multidrop is on, gather addressee headers */
        if (MULTIDROP(ctl))
        {
            if (!strncasecmp("To:", line, 3)
                || !strncasecmp("Cc:", line, 3)
                || !strncasecmp("Bcc:", line, 4)
                || !strncasecmp("Apparently-To:", line, 14))
            {
                *to_chainptr = xmalloc(sizeof(struct addrblk));
                (*to_chainptr)->offset = (line - msgblk.headers);
                to_chainptr = &(*to_chainptr)->next; 
                *to_chainptr = NULL;
            }

            else if (!strncasecmp("Resent-To:", line, 10)
                     || !strncasecmp("Resent-Cc:", line, 10)
                     || !strncasecmp("Resent-Bcc:", line, 11))
            {
                *resent_to_chainptr = xmalloc(sizeof(struct addrblk));
                (*resent_to_chainptr)->offset = (line - msgblk.headers);
                resent_to_chainptr = &(*resent_to_chainptr)->next; 
                *resent_to_chainptr = NULL;
            }

            else if (ctl->server.envelope != STRING_DISABLED)
            {
                if (ctl->server.envelope 
                    && strcasecmp(ctl->server.envelope, "Received"))
                {
                    if (env_offs == -1 && !strncasecmp(ctl->server.envelope,
                                                       line,
                                                       strlen(ctl->server.envelope)))
                    {                           
                        if (skipcount++ < ctl->server.envskip)
                            continue;
                        env_offs = (line - msgblk.headers);
                    }    
                }
                else if (!received_for && !strncasecmp("Received:", line, 9))
                {
                    if (skipcount++ < ctl->server.envskip)
                        continue;
                    received_for = parse_received(ctl, line);
                }
            }
        }
    }

 process_headers:    

    if (retain_mail)
    {
        free(msgblk.headers);
        msgblk.headers = NULL;
        return(PS_RETAINED);
    }
    if (refuse_mail)
        return(PS_REFUSED);
    /*
     * This is the duplicate-message killer code.
     *
     * When mail delivered to a multidrop mailbox on the server is
     * addressed to multiple people on the client machine, there will
     * be one copy left in the box for each recipient.  This is not a
     * problem if we have the actual recipient address to dispatch on
     * (e.g. because we've mined it out of sendmail trace headers, or
     * a qmail Delivered-To line, or a declared sender envelope line).
     *
     * But if we're mining addressees out of the To/Cc/Bcc fields, and
     * if the mail is addressed to N people, each recipient will
     * get N copies.  This is bad when N > 1.
     *
     * Foil this by suppressing all but one copy of a message with a
     * given set of headers.
     *
     * Note: This implementation only catches runs of successive
     * messages with the same ID, but that should be good
     * enough. A more general implementation would have to store
     * ever-growing lists of seen message-IDs; in a long-running
     * daemon this would turn into a memory leak even if the 
     * implementation were perfect.
     * 
     * Don't mess with this code casually.  It would be way too easy
     * to break it in a way that blackholed mail.  Better to pass
     * the occasional duplicate than to do that...
     */
    if (MULTIDROP(ctl))
    {
        MD5_CTX context;

        MD5Init(&context);
        MD5Update(&context, msgblk.headers, strlen(msgblk.headers));
        MD5Final(ctl->digest, &context);

        if (!received_for && env_offs == -1 && !delivered_to)
        {
            /*
             * Hmmm...can MD5 ever yield all zeroes as a hash value?
             * If so there is a one in 18-quadrillion chance this 
             * code will incorrectly nuke the first message.
             */
            if (!memcmp(ctl->lastdigest, ctl->digest, DIGESTLEN))
                return(PS_REFUSED);
        }
        memcpy(ctl->lastdigest, ctl->digest, DIGESTLEN);
    }

    /*
     * 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 (msgblk.headers == (char *)NULL)
    {
        snprintf(buf, sizeof(buf),
                "From: FETCHMAIL-DAEMON\r\n"
                "To: %s@%s\r\n"
                "Subject: Headerless mail from %s's mailbox on %s\r\n",
                user, fetchmailhost, ctl->remotename, ctl->server.truename);
        msgblk.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.
     */

    /* Check for MIME headers indicating possible 8-bit data */
    ctl->mimemsg = MimeBodyType(msgblk.headers, ctl->mimedecode);

#ifdef SDPS_ENABLE
    if (ctl->server.sdps && sdps_envfrom)
    {
        /* We have the real envelope return-path, stored out of band by
         * SDPS - that's more accurate than any header is going to be.
         */
        strlcpy(msgblk.return_path, sdps_envfrom, sizeof(msgblk.return_path));
        free(sdps_envfrom);
    } else
#endif /* SDPS_ENABLE */
    /*
     * If there is a Return-Path address on the message, this was
     * almost certainly the MAIL FROM address given the originating
     * sendmail.  This is the best thing to use for logging the
     * message origin (it sets up the right behavior for bounces and
     * mailing lists).  Otherwise, fall down to the next available 
     * envelope address (which is the most probable real sender).
     * *** The order is important! ***
     * This is especially useful when receiving mailing list
     * messages in multidrop mode.  if a local address doesn't
     * exist, the bounce message won't be returned blindly to the 
     * author or to the list itself but rather to the list manager
     * (ex: specified by "Sender:") which is much less annoying.  This 
     * is true for most mailing list packages.
     */
    if( !msgblk.return_path[0] ){
        char *ap = NULL;
        if (resent_sender_offs >= 0 && (ap = nxtaddr(msgblk.headers + resent_sender_offs)));
        else if (sender_offs >= 0 && (ap = nxtaddr(msgblk.headers + sender_offs)));
        else if (resent_from_offs >= 0 && (ap = nxtaddr(msgblk.headers + resent_from_offs)));
        else if (from_offs >= 0 && (ap = nxtaddr(msgblk.headers + from_offs)));
        else if (reply_to_offs >= 0 && (ap = nxtaddr(msgblk.headers + reply_to_offs)));
        else if (app_from_offs >= 0 && (ap = nxtaddr(msgblk.headers + app_from_offs))) {}
        /* multi-line MAIL FROM addresses confuse SMTP terribly */
        if (ap && !strchr(ap, '\n')) {
            strncpy(msgblk.return_path, ap, sizeof(msgblk.return_path));
            msgblk.return_path[sizeof(msgblk.return_path)-1] = '\0';
        }
    }

    /* cons up a list of local recipients */
    msgblk.recipients = (struct idlist *)NULL;
    accept_count = reject_count = 0;
    /* is this a multidrop box? */
    if (MULTIDROP(ctl))
    {
#ifdef SDPS_ENABLE
        if (ctl->server.sdps && sdps_envto)
        {
            /* We have the real envelope recipient, stored out of band by
             * SDPS - that's more accurate than any header is going to be.
             */
            find_server_names(sdps_envto, ctl, &msgblk.recipients);
            free(sdps_envto);
        } else
#endif /* SDPS_ENABLE */ 
        if (env_offs > -1)          /* We have the actual envelope addressee */
            find_server_names(msgblk.headers + env_offs, ctl, &msgblk.recipients);
        else if (delivered_to && ctl->server.envelope != STRING_DISABLED &&
      ctl->server.envelope && !strcasecmp(ctl->server.envelope, "Delivered-To"))
   {
            find_server_names(delivered_to, ctl, &msgblk.recipients);
       free(delivered_to);
       delivered_to = NULL;
   }
        else if (received_for)
            /*
             * We have the Received for addressee.  
             * It has to be a mailserver address, or we
             * wouldn't have got here.
             * We use find_server_names() to let local 
             * hostnames go through.
             */
            find_server_names(received_for, ctl, &msgblk.recipients);
        else
        {
            /*
             * We haven't extracted the envelope address.
             * So check all the "Resent-To" header addresses if 
             * they exist.  If and only if they don't, consider
             * the "To" addresses.
             */
            register struct addrblk *nextptr;
            if (resent_to_addrchain) {
                /* delete the "To" chain and substitute it 
                 * with the "Resent-To" list 
                 */
                while (to_addrchain) {
                    nextptr = to_addrchain->next;
                    free(to_addrchain);
                    to_addrchain = nextptr;
                }
                to_addrchain = resent_to_addrchain;
                resent_to_addrchain = NULL;
            }
            /* now look for remaining adresses */
            while (to_addrchain) {
                find_server_names(msgblk.headers+to_addrchain->offset, ctl, &msgblk.recipients);
                nextptr = to_addrchain->next;
                free(to_addrchain);
                to_addrchain = nextptr;
            }
        }
        if (!accept_count)
        {
            no_local_matches = TRUE;
            save_str(&msgblk.recipients, run.postmaster, XMIT_ACCEPT);
            if (outlevel >= O_DEBUG)
                report(stdout,
                      GT_("no local matches, forwarding to %s\n"),
                      run.postmaster);
        }
    }
    else        /* it's a single-drop box, use first localname */
        save_str(&msgblk.recipients, ctl->localnames->id, XMIT_ACCEPT);


    /*
     * Time to either address the message or decide we can't deliver it yet.
     */
    if (ctl->errcount > olderrs)        /* there were DNS errors above */
    {
        if (outlevel >= O_DEBUG)
            report(stdout,
                   GT_("forwarding and deletion suppressed due to DNS errors\n"));
        free(msgblk.headers);
        msgblk.headers = NULL;
        free_str_list(&msgblk.recipients);
        return(PS_TRANSIENT);
    }
    else
    {
        /* set up stuffline() so we can deliver the message body through it */ 
        if ((n = open_sink(ctl, &msgblk,
                           &good_addresses, &bad_addresses)) != PS_SUCCESS)
        {
            free(msgblk.headers);
            msgblk.headers = NULL;
            free_str_list(&msgblk.recipients);
            return(n);
        }
    }

    n = 0;
    /*
     * Some server/sendmail combinations cause problems when our
     * synthetic Received line is before the From header.  Cope
     * with this...
     */
    if ((rcv = strstr(msgblk.headers, "Received:")) == (char *)NULL)
        rcv = msgblk.headers;
    /* handle ">Received:" lines too */
    while (rcv > msgblk.headers && rcv[-1] != '\n')
        rcv--;
    if (rcv > msgblk.headers)
    {
        char    c = *rcv;

        *rcv = '\0';
        n = stuffline(ctl, msgblk.headers);
        *rcv = c;
    }
    if (!run.invisible && n != -1)
    {
        /* utter any per-message Received information we need here */
        if (ctl->server.trueaddr) {
            char saddr[50];
            int e;

            e = getnameinfo(ctl->server.trueaddr, ctl->server.trueaddr_len,
                    saddr, sizeof(saddr), NULL, 0,
                    NI_NUMERICHOST);
            if (e)
                snprintf(saddr, sizeof(saddr), "(%-.*s)", sizeof(saddr) - 3, gai_strerror(e));
            snprintf(buf, sizeof(buf),
                    "Received: from %s [%s]\r\n", 
                    ctl->server.truename, saddr);
        } else {
            snprintf(buf, sizeof(buf),
                  "Received: from %s\r\n", ctl->server.truename);
        }
        n = stuffline(ctl, buf);
        if (n != -1)
        {
            /*
             * This header is technically invalid under RFC822.
             * POP3, IMAP, etc. are not legal mail-parameter values.
             */
            snprintf(buf, sizeof(buf),
                    "\tby %s with %s (fetchmail-%s",
                    fetchmailhost,
                    protocol->name,
                    VERSION);
            if (ctl->server.tracepolls)
            {
                snprintf(buf + strlen(buf), sizeof(buf) - strlen(buf),
                        " polling %s account %s",
                        ctl->server.pollname,
                        ctl->remotename);
            }
            snprintf(buf+strlen(buf), sizeof(buf)-strlen(buf), ")\r\n");
            n = stuffline(ctl, buf);
            if (n != -1)
            {
                buf[0] = '\t';
                if (good_addresses == 0)
                {
                    snprintf(buf+1, sizeof(buf)-1, "for <%s> (by default); ",
                            rcpt_address (ctl, run.postmaster, 0));
                }
                else if (good_addresses == 1)
                {
                    for (idp = msgblk.recipients; idp; idp = idp->next)
                        if (idp->val.status.mark == XMIT_ACCEPT)
                            break;      /* only report first address */
                    snprintf(buf+1, sizeof(buf)-1,
                            "for <%s>", rcpt_address (ctl, idp->id, 1));
                    snprintf(buf+strlen(buf), sizeof(buf)-strlen(buf)-1,
                            " (%s); ",
                            MULTIDROP(ctl) ? "multi-drop" : "single-drop");
                }
                else
                    buf[1] = '\0';

                snprintf(buf+strlen(buf), sizeof(buf)-strlen(buf), "%s\r\n",
                        rfc822timestamp());
                n = stuffline(ctl, buf);
            }
        }
    }

    if (n != -1)
        n = stuffline(ctl, rcv);        /* ship out rest of msgblk.headers */

    if (n == -1)
    {
        report(stdout, GT_("writing RFC822 msgblk.headers\n"));
        release_sink(ctl);
        free(msgblk.headers);
        msgblk.headers = NULL;
        free_str_list(&msgblk.recipients);
        return(PS_IOERR);
    }
    else if ((run.poll_interval == 0 || nodetach) && outlevel >= O_VERBOSE && !is_a_file(1) && !run.use_syslog)
        fputc('#', stdout);

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

        errmsg = errhd;
        strlcpy(errhd, "X-Fetchmail-Warning: ", sizeof(errhd));
        if (no_local_matches)
        {
            if (reject_count != 1)
                strlcat(errhd, GT_("no recipient addresses matched declared local names"), sizeof(errhd));
            else
            {
                for (idp = msgblk.recipients; idp; idp = idp->next)
                    if (idp->val.status.mark == XMIT_REJECT)
                        break;
                snprintf(errhd+strlen(errhd), sizeof(errhd)-strlen(errhd),
                        GT_("recipient address %s didn't match any local name"), idp->id);
            }
        }

        if (has_nuls)
        {
            if (errhd[sizeof("X-Fetchmail-Warning: ")])
                snprintf(errhd+strlen(errhd), sizeof(errhd)-strlen(errhd), "; ");
            snprintf(errhd+strlen(errhd), sizeof(errhd)-strlen(errhd),
                        GT_("message has embedded NULs"));
        }

        if (bad_addresses)
        {
            if (errhd[sizeof("X-Fetchmail-Warning: ")])
                snprintf(errhd+strlen(errhd), sizeof(errhd)-strlen(errhd), "; ");
            snprintf(errhd+strlen(errhd), sizeof(errhd)-strlen(errhd),
                        GT_("SMTP listener rejected local recipient addresses: "));
            errlen = strlen(errhd);
            for (idp = msgblk.recipients; idp; idp = idp->next)
                if (idp->val.status.mark == XMIT_RCPTBAD)
                    errlen += strlen(idp->id) + 2;

            errmsg = xmalloc(errlen + 3);
            strcpy(errmsg, errhd);
            for (idp = msgblk.recipients; idp; idp = idp->next)
                if (idp->val.status.mark == XMIT_RCPTBAD)
                {
                    strcat(errmsg, idp->id);
                    if (idp->next)
                        strcat(errmsg, ", ");
                }

        }

        strcat(errmsg, "\r\n");

        /* ship out the error line */
        stuffline(ctl, errmsg);

        if (errmsg != errhd)
            free(errmsg);
    }

    /* issue the delimiter line */
    cp = buf;
    *cp++ = '\r';
    *cp++ = '\n';
    *cp++ = '\0';
    stuffline(ctl, buf);

    return(PS_SUCCESS);
}

int readbody(int sock, struct query *ctl, flag forward, int len)
/* read and dispose of a message body presented on sock */
/*   ctl:               query control record */
/*   sock:              to which the server is connected */
/*   len:               length of message */
/*   forward:           TRUE to forward */
{
    int linelen;
    unsigned char buf[MSGBUFSIZE+4];
    unsigned char *inbufp = buf;
    flag issoftline = FALSE;

    /*
     * Pass through the text lines in the body.
     *
     * Yes, this wants to be ||, not &&.  The problem is that in the most
     * important delimited protocol, POP3, the length is not reliable.
     * As usual, the problem is Microsoft brain damage; see FAQ item S2.
     * So, for delimited protocols we need to ignore the length here and
     * instead drop out of the loop with a break statement when we see
     * the message delimiter.
     */
    while (protocol->delimited || len > 0)
    {
        set_timeout(mytimeout);
        if ((linelen = SockRead(sock, inbufp, sizeof(buf)-4-(inbufp-buf)))==-1)
        {
            set_timeout(0);
            release_sink(ctl);
            return(PS_SOCKET);
        }
        set_timeout(0);

        /* write the message size dots */
        if (linelen > 0)
        {
            sizeticker += linelen;
            while (sizeticker >= SIZETICKER)
            {
                if (outlevel > O_SILENT && run.showdots && !run.use_syslog)
                {
                    fputc('.', stdout);
                    fflush(stdout);
                }
                sizeticker -= SIZETICKER;
            }
        }
        len -= linelen;

        /* check for end of message */
        if (protocol->delimited && *inbufp == '.')
        {
            if (EMPTYLINE(inbufp+1))
                break;
            else
                msgblk.msglen--;        /* subtract the size of the dot escape */
        }

        msgblk.msglen += linelen;

        if (ctl->mimedecode && (ctl->mimemsg & MSG_NEEDS_DECODE)) {
            issoftline = UnMimeBodyline(&inbufp, protocol->delimited, issoftline);
            if (issoftline && (sizeof(buf)-1-(inbufp-buf) < 200))
            {
                /*
                 * Soft linebreak, but less than 200 bytes left in
                 * input buffer. Rather than doing a buffer overrun,
                 * ignore the soft linebreak, NL-terminate data and
                 * deliver what we have now.
                 * (Who writes lines longer than 2K anyway?)
                 */
                *inbufp = '\n'; *(inbufp+1) = '\0';
                issoftline = 0;
            }
        }

        /* ship out the text line */
        if (forward && (!issoftline))
        {
            int n;
            inbufp = buf;

            /* guard against very long lines */
            buf[MSGBUFSIZE+1] = '\r';
            buf[MSGBUFSIZE+2] = '\n';
            buf[MSGBUFSIZE+3] = '\0';

            n = stuffline(ctl, buf);

            if (n < 0)
            {
                report(stdout, GT_("writing message text\n"));
                release_sink(ctl);
                return(PS_IOERR);
            }
            else if (outlevel >= O_VERBOSE && !is_a_file(1) && !run.use_syslog)
            {
                fputc('*', stdout);
                fflush(stdout);
            }
        }
    }

    return(PS_SUCCESS);
}

void init_transact(const struct method *proto)
/* initialize state for the send and receive functions */
{
    suppress_tags = FALSE;
    tagnum = 0;
    tag[0] = '\0';      /* nuke any tag hanging out from previous query */
    protocol = (struct method *)proto;
    shroud[0] = '\0';
}

static void enshroud(char *buf)
/* shroud a password in the given buffer */
{
    char *cp;

    if (shroud[0] && (cp = strstr(buf, shroud)))
    {
       char    *sp;

       sp = cp + strlen(shroud);
       *cp++ = '*';
       while (*sp)
           *cp++ = *sp++;
       *cp = '\0';
    }
}

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

    if (protocol->tagged && !suppress_tags)
        snprintf(buf, sizeof(buf) - 2, "%s ", GENSYM);
    else
        buf[0] = '\0';

#if defined(HAVE_STDARG_H)
    va_start(ap, fmt);
#else
    va_start(ap);
#endif
    vsnprintf(buf + strlen(buf), sizeof(buf)-2-strlen(buf), fmt, ap);
    va_end(ap);

    snprintf(buf+strlen(buf), sizeof(buf)-strlen(buf), "\r\n");
    SockWrite(sock, buf, strlen(buf));

    if (outlevel >= O_MONITOR)
    {
        enshroud(buf);
        buf[strlen(buf)-2] = '\0';
        report(stdout, "%s> %s\n", protocol->name, buf);
    }
}

int gen_recv(sock, buf, size)
/* get one line of input from the server */
int sock;       /* socket to which server is connected */
char *buf;      /* buffer to receive input */
int size;       /* length of buffer */
{
    int oldphase = phase;       /* we don't have to be re-entrant */

    phase = SERVER_WAIT;
    set_timeout(mytimeout);
    if (SockRead(sock, buf, size) == -1)
    {
        set_timeout(0);
        phase = oldphase;
        if(is_idletimeout())
        {
          resetidletimeout();
          return(PS_IDLETIMEOUT);
        }
        else
          return(PS_SOCKET);
    }
    else
    {
        set_timeout(0);
        if (buf[strlen(buf)-1] == '\n')
            buf[strlen(buf)-1] = '\0';
        if (buf[strlen(buf)-1] == '\r')
            buf[strlen(buf)-1] = '\0';
        if (outlevel >= O_MONITOR)
            report(stdout, "%s< %s\n", protocol->name, buf);
        phase = oldphase;
        return(PS_SUCCESS);
    }
}

#if defined(HAVE_STDARG_H)
int gen_transact(int sock, const char *fmt, ... )
#else
int gen_transact(int sock, fmt, va_alist)
int sock;               /* socket to which server is connected */
const char *fmt;        /* printf-style format */
va_dcl
#endif
/* assemble command in printf(3) style, send to server, accept a response */
{
    int ok;
    char buf [MSGBUFSIZE+1];
    va_list ap;
    int oldphase = phase;       /* we don't have to be re-entrant */

    phase = SERVER_WAIT;

    if (protocol->tagged && !suppress_tags)
        snprintf(buf, sizeof(buf) - 2, "%s ", GENSYM);
    else
        buf[0] = '\0';

#if defined(HAVE_STDARG_H)
    va_start(ap, fmt) ;
#else
    va_start(ap);
#endif
    vsnprintf(buf + strlen(buf), sizeof(buf)-2-strlen(buf), fmt, ap);
    va_end(ap);

    snprintf(buf+strlen(buf), sizeof(buf)-strlen(buf), "\r\n");
    if (SockWrite(sock, buf, strlen(buf)) < strlen(buf)) {
        /* short write, bail out */
        return PS_SOCKET;
    }

    if (outlevel >= O_MONITOR)
    {
        enshroud(buf);
        buf[strlen(buf)-2] = '\0';
        report(stdout, "%s> %s\n", protocol->name, buf);
    }

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

    phase = oldphase;
    return(ok);
}

/* transact.c ends here */