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Sourcecode: fetchmail version File versions

imap.c

/*
 * imap.c -- IMAP2bis/IMAP4 protocol methods
 *
 * Copyright 1997 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>
#if defined(STDC_HEADERS)
#include  <stdlib.h>
#include  <limits.h>
#include  <errno.h>
#endif
#include  "fetchmail.h"
#include  "socket.h"

#include  "i18n.h"

#if OPIE_ENABLE
#endif /* OPIE_ENABLE */

#ifndef strstr          /* glibc-2.1 declares this as a macro */
extern char *strstr();  /* needed on sysV68 R3V7.1. */
#endif /* strstr */

/* imap_version values */
#define IMAP2           -1    /* IMAP2 or IMAP2BIS, RFC1176 */
#define IMAP4           0     /* IMAP4 rev 0, RFC1730 */
#define IMAP4rev1 1     /* IMAP4 rev 1, RFC2060 */

static int count = 0, recentcount = 0, unseen = 0, deletions = 0;
static unsigned int startcount = 1;
static int expunged, expunge_period, saved_timeout = 0;
static int imap_version, preauth;
static flag do_idle, has_idle;
static char capabilities[MSGBUFSIZE+1];
static unsigned int *unseen_messages;

static int imap_ok(int sock, char *argbuf)
/* parse command response */
{
    char buf[MSGBUFSIZE+1];

    do {
      int   ok;
      char  *cp;

      if ((ok = gen_recv(sock, buf, sizeof(buf))))
          return(ok);

      /* all tokens in responses are caseblind */
      for (cp = buf; *cp; cp++)
          if (islower(*cp))
            *cp = toupper(*cp);

      /* interpret untagged status responses */
      if (strstr(buf, "* CAPABILITY"))
      {
          strncpy(capabilities, buf + 12, sizeof(capabilities));
          capabilities[sizeof(capabilities)-1] = '\0';
      }
      else if (strstr(buf, "EXISTS"))
      {
          count = atoi(buf+2);
          /*
           * Don't trust the message count passed by the server.
           * Without this check, it might be possible to do a
           * DNS-spoofing attack that would pass back a ridiculous 
           * count, and allocate a malloc area that would overlap
           * a portion of the stack.
           */
          if (count > INT_MAX/sizeof(int))
          {
            report(stderr, "bogus message count!");
            return(PS_PROTOCOL);
          }

          /*
           * Nasty kluge to handle RFC2177 IDLE.  If we know we're idling
           * we can't wait for the tag matching the IDLE; we have to tell the
           * server the IDLE is finished by shipping back a DONE when we
           * see an EXISTS.  Only after that will a tagged response be
           * shipped.  The idling flag also gets cleared on a timeout.
           */
          if (stage == STAGE_IDLE)
          {
            /* If IDLE isn't supported, we were only sending NOOPs anyway. */
            if (has_idle)
            {
                /* we do our own write and report here to disable tagging */
                SockWrite(sock, "DONE\r\n", 6);
                if (outlevel >= O_MONITOR)
                    report(stdout, "IMAP> DONE\n");
            }

            mytimeout = saved_timeout;
            stage = STAGE_FETCH;
          }
      }
      /* a space is required to avoid confusion with the \Recent flag */
      else if (strstr(buf, " RECENT"))
      {
          recentcount = atoi(buf+2);
      }
      else if (strstr(buf, "PREAUTH"))
          preauth = TRUE;
      /*
       * The server may decide to make the mailbox read-only, 
       * which causes fetchmail to go into a endless loop
       * fetching the same message over and over again. 
       * 
       * However, for check_only, we use EXAMINE which will
       * mark the mailbox read-only as per the RFC.
       * 
       * This checks for the condition and aborts if 
       * the mailbox is read-only. 
       *
       * See RFC 2060 section 6.3.1 (SELECT).
       * See RFC 2060 section 6.3.2 (EXAMINE).
       */ 
      else if (!check_only && strstr(buf, "[READ-ONLY]"))
          return(PS_LOCKBUSY);
    } while
      (tag[0] != '\0' && strncmp(buf, tag, strlen(tag)));

    if (tag[0] == '\0')
    {
      if (argbuf)
          strcpy(argbuf, buf);
      return(PS_SUCCESS); 
    }
    else
    {
      char  *cp;

      /* skip the tag */
      for (cp = buf; !isspace(*cp); cp++)
          continue;
      while (isspace(*cp))
          cp++;

        if (strncasecmp(cp, "OK", 2) == 0)
      {
          if (argbuf)
            strcpy(argbuf, cp);
          return(PS_SUCCESS);
      }
      else if (strncasecmp(cp, "BAD", 3) == 0)
          return(PS_ERROR);
      else if (strncasecmp(cp, "NO", 2) == 0)
      {
          if (stage == STAGE_GETAUTH) 
            return(PS_AUTHFAIL);    /* RFC2060, 6.2.2 */
          else
            return(PS_ERROR);
      }
      else
          return(PS_PROTOCOL);
    }
}

#if NTLM_ENABLE
#include "ntlm.h"

static tSmbNtlmAuthRequest   request;              
static tSmbNtlmAuthChallenge challenge;
static tSmbNtlmAuthResponse  response;

/*
 * NTLM support by Grant Edwards.
 *
 * Handle MS-Exchange NTLM authentication method.  This is the same
 * as the NTLM auth used by Samba for SMB related services. We just
 * encode the packets in base64 instead of sending them out via a
 * network interface.
 * 
 * Much source (ntlm.h, smb*.c smb*.h) was borrowed from Samba.
 */

static int do_imap_ntlm(int sock, struct query *ctl)
{
    char msgbuf[2048];
    int result,len;
  
    gen_send(sock, "AUTHENTICATE NTLM");

    if ((result = gen_recv(sock, msgbuf, sizeof msgbuf)))
      return result;
  
    if (msgbuf[0] != '+')
      return PS_AUTHFAIL;
  
    buildSmbNtlmAuthRequest(&request,ctl->remotename,NULL);

    if (outlevel >= O_DEBUG)
      dumpSmbNtlmAuthRequest(stdout, &request);

    memset(msgbuf,0,sizeof msgbuf);
    to64frombits (msgbuf, (unsigned char*)&request, SmbLength(&request));
  
    if (outlevel >= O_MONITOR)
      report(stdout, "IMAP> %s\n", msgbuf);
  
    strcat(msgbuf,"\r\n");
    SockWrite (sock, msgbuf, strlen (msgbuf));

    if ((gen_recv(sock, msgbuf, sizeof msgbuf)))
      return result;
  
    len = from64tobits ((char*)&challenge, msgbuf, sizeof(challenge));
    
    if (outlevel >= O_DEBUG)
      dumpSmbNtlmAuthChallenge(stdout, &challenge);
    
    buildSmbNtlmAuthResponse(&challenge, &response,ctl->remotename,ctl->password);
  
    if (outlevel >= O_DEBUG)
      dumpSmbNtlmAuthResponse(stdout, &response);
  
    memset(msgbuf,0,sizeof msgbuf);
    to64frombits (msgbuf, (unsigned char*)&response, SmbLength(&response));

    if (outlevel >= O_MONITOR)
      report(stdout, "IMAP> %s\n", msgbuf);
      
    strcat(msgbuf,"\r\n");
    SockWrite (sock, msgbuf, strlen (msgbuf));
  
    if ((result = gen_recv (sock, msgbuf, sizeof msgbuf)))
      return result;
  
    if (strstr (msgbuf, "OK"))
      return PS_SUCCESS;
    else
      return PS_AUTHFAIL;
}
#endif /* NTLM */

static int imap_canonicalize(char *result, char *raw, int maxlen)
/* encode an IMAP password as per RFC1730's quoting conventions */
{
    int i, j;

    j = 0;
    for (i = 0; i < strlen(raw) && i < maxlen; i++)
    {
      if ((raw[i] == '\\') || (raw[i] == '"'))
          result[j++] = '\\';
      result[j++] = raw[i];
    }
    result[j] = '\0';

    return(i);
}

static void capa_probe(int sock, struct query *ctl)
/* set capability variables from a CAPA probe */
{
    int     ok;

    /* probe to see if we're running IMAP4 and can use RFC822.PEEK */
    capabilities[0] = '\0';
    if ((ok = gen_transact(sock, "CAPABILITY")) == PS_SUCCESS)
    {
      char  *cp;

      /* capability checks are supposed to be caseblind */
      for (cp = capabilities; *cp; cp++)
          *cp = toupper(*cp);

      /* UW-IMAP server 10.173 notifies in all caps, but RFC2060 says we
         should expect a response in mixed-case */
      if (strstr(capabilities, "IMAP4REV1"))
      {
          imap_version = IMAP4rev1;
          if (outlevel >= O_DEBUG)
            report(stdout, GT_("Protocol identified as IMAP4 rev 1\n"));
      }
      else
      {
          imap_version = IMAP4;
          if (outlevel >= O_DEBUG)
            report(stdout, GT_("Protocol identified as IMAP4 rev 0\n"));
      }
    }
    else if (ok == PS_ERROR)
    {
      imap_version = IMAP2;
      if (outlevel >= O_DEBUG)
          report(stdout, GT_("Protocol identified as IMAP2 or IMAP2BIS\n"));
    }

    /* 
     * Handle idling.  We depend on coming through here on startup
     * and after each timeout (including timeouts during idles).
     */
    if (ctl->idle)
    {
      do_idle = TRUE;
      if (strstr(capabilities, "IDLE"))
      {
          has_idle = TRUE;
      }
      if (outlevel >= O_VERBOSE)
          report(stdout, GT_("will idle after poll\n"));
    }

    peek_capable = (imap_version >= IMAP4);
}

static int imap_getauth(int sock, struct query *ctl, char *greeting)
/* apply for connection authorization */
{
    int ok = 0;
#ifdef SSL_ENABLE
    flag did_stls = FALSE;
#endif /* SSL_ENABLE */

    /*
     * Assumption: expunges are cheap, so we want to do them
     * after every message unless user said otherwise.
     */
    if (NUM_SPECIFIED(ctl->expunge))
      expunge_period = NUM_VALUE_OUT(ctl->expunge);
    else
      expunge_period = 1;

    capa_probe(sock, ctl);

    /* 
     * If either (a) we saw a PREAUTH token in the greeting, or
     * (b) the user specified ssh preauthentication, then we're done.
     */
    if (preauth || ctl->server.authenticate == A_SSH)
    {
        preauth = FALSE;  /* reset for the next session */
        return(PS_SUCCESS);
    }

#ifdef SSL_ENABLE
    if ((!ctl->sslproto || !strcmp(ctl->sslproto,"tls1"))
        && !ctl->use_ssl
        && strstr(capabilities, "STARTTLS"))
    {
           char *realhost;

           realhost = ctl->server.via ? ctl->server.via : ctl->server.pollname;
           ok = gen_transact(sock, "STARTTLS");

           /* We use "tls1" instead of ctl->sslproto, as we want STARTTLS,
            * not other SSL protocols
            */
           if (ok == PS_SUCCESS &&
             SSLOpen(sock,ctl->sslcert,ctl->sslkey,"tls1",ctl->sslcertck, ctl->sslcertpath,ctl->sslfingerprint,realhost,ctl->server.pollname) == -1)
           {
             if (!ctl->sslproto && !ctl->wehaveauthed)
             {
               ctl->sslproto = xstrdup("");
               /* repoll immediately */
               return(PS_REPOLL);
             }
               report(stderr,
                      GT_("SSL connection failed.\n"));
               return(PS_AUTHFAIL);
           }
         did_stls = TRUE;

         /*
          * RFC 2595 says this:
          *
          * "Once TLS has been started, the client MUST discard cached
          * information about server capabilities and SHOULD re-issue the
          * CAPABILITY command.  This is necessary to protect against
          * man-in-the-middle attacks which alter the capabilities list prior
          * to STARTTLS.  The server MAY advertise different capabilities
          * after STARTTLS."
          */
         capa_probe(sock, ctl);
    }
#endif /* SSL_ENABLE */

    /*
     * Time to authenticate the user.
     * Try the protocol variants that don't require passwords first.
     */
    ok = PS_AUTHFAIL;

#ifdef GSSAPI
    if ((ctl->server.authenticate == A_ANY 
       || ctl->server.authenticate == A_GSSAPI)
      && strstr(capabilities, "AUTH=GSSAPI"))
      if(ok = do_gssauth(sock, "AUTHENTICATE", ctl->server.truename, ctl->remotename))
      {
          /* SASL cancellation of authentication */
          gen_send(sock, "*");
          if(ctl->server.authenticate != A_ANY)
                return ok;
      }
      else
          return ok;
#endif /* GSSAPI */

#ifdef KERBEROS_V4
    if ((ctl->server.authenticate == A_ANY 
       || ctl->server.authenticate == A_KERBEROS_V4
       || ctl->server.authenticate == A_KERBEROS_V5) 
      && strstr(capabilities, "AUTH=KERBEROS_V4"))
    {
      if ((ok = do_rfc1731(sock, "AUTHENTICATE", ctl->server.truename)))
      {
          /* SASL cancellation of authentication */
          gen_send(sock, "*");
          if(ctl->server.authenticate != A_ANY)
                return ok;
      }
      else
          return ok;
    }
#endif /* KERBEROS_V4 */

    /*
     * No such luck.  OK, now try the variants that mask your password
     * in a challenge-response.
     */

    if ((ctl->server.authenticate == A_ANY && strstr(capabilities, "AUTH=CRAM-MD5"))
      || ctl->server.authenticate == A_CRAM_MD5)
    {
      if ((ok = do_cram_md5 (sock, "AUTHENTICATE", ctl, NULL)))
      {
          /* SASL cancellation of authentication */
          gen_send(sock, "*");
          if(ctl->server.authenticate != A_ANY)
                return ok;
      }
      else
          return ok;
    }

#if OPIE_ENABLE
    if ((ctl->server.authenticate == A_ANY 
       || ctl->server.authenticate == A_OTP)
      && strstr(capabilities, "AUTH=X-OTP"))
      if ((ok = do_otp(sock, "AUTHENTICATE", ctl)))
      {
          /* SASL cancellation of authentication */
          gen_send(sock, "*");
          if(ctl->server.authenticate != A_ANY)
                return ok;
      }
      else
          return ok;
#else
    if (ctl->server.authenticate == A_OTP)
    {
      report(stderr, 
         GT_("Required OTP capability not compiled into fetchmail\n"));
    }
#endif /* OPIE_ENABLE */

#ifdef NTLM_ENABLE
    if ((ctl->server.authenticate == A_ANY 
       || ctl->server.authenticate == A_NTLM) 
      && strstr (capabilities, "AUTH=NTLM")) {
      if ((ok = do_imap_ntlm(sock, ctl)))
      {
          /* SASL cancellation of authentication */
          gen_send(sock, "*");
          if(ctl->server.authenticate != A_ANY)
                return ok;
      }
      else
          return(ok);
    }
#else
    if (ctl->server.authenticate == A_NTLM)
    {
      report(stderr, 
         GT_("Required NTLM capability not compiled into fetchmail\n"));
    }
#endif /* NTLM_ENABLE */

#ifdef __UNUSED__ /* The Cyrus IMAP4rev1 server chokes on this */
    /* this handles either AUTH=LOGIN or AUTH-LOGIN */
    if ((imap_version >= IMAP4rev1) && (!strstr(capabilities, "LOGIN")))
    {
      report(stderr, 
             GT_("Required LOGIN capability not supported by server\n"));
    }
#endif /* __UNUSED__ */

    /* 
     * We're stuck with sending the password en clair.
     * The reason for this odd-looking logic is that some
     * servers return LOGINDISABLED even though login 
     * actually works.  So arrange things in such a way that
     * setting auth passwd makes it ignore this capability.
     */
    if((ctl->server.authenticate==A_ANY&&!strstr(capabilities,"LOGINDISABLED"))
      || ctl->server.authenticate == A_PASSWORD)
    {
      /* these sizes guarantee no buffer overflow */
      char  remotename[NAMELEN*2+1], password[PASSWORDLEN*2+1];

      imap_canonicalize(remotename, ctl->remotename, NAMELEN);
      imap_canonicalize(password, ctl->password, PASSWORDLEN);

#ifdef HAVE_SNPRINTF
      snprintf(shroud, sizeof (shroud), "\"%s\"", password);
#else
      strcpy(shroud, "\"");
      strcat(shroud, password);
      strcat(shroud, "\"");
#endif
      ok = gen_transact(sock, "LOGIN \"%s\" \"%s\"", remotename, password);
      shroud[0] = '\0';
#ifdef SSL_ENABLE
      /* this is for servers which claim to support TLS, but actually
       * don't! */
      if (did_stls && ok == PS_SOCKET && !ctl->sslproto && !ctl->wehaveauthed)
      {
          ctl->sslproto = xstrdup("");
          /* repoll immediately */
          ok = PS_REPOLL;
      }
#endif
      if (ok)
      {
          /* SASL cancellation of authentication */
          gen_send(sock, "*");
          if(ctl->server.authenticate != A_ANY)
                return ok;
      }
      else
          return(ok);
    }

    return(ok);
}

static int internal_expunge(int sock)
/* ship an expunge, resetting associated counters */
{
    int     ok;

    if ((ok = gen_transact(sock, "EXPUNGE")))
      return(ok);

    expunged += deletions;
    deletions = 0;

#ifdef IMAP_UID   /* not used */
    expunge_uids(ctl);
#endif /* IMAP_UID */

    return(PS_SUCCESS);
}

static int imap_idle(int sock)
/* start an RFC2177 IDLE, or fake one if unsupported */
{
    int ok;

    stage = STAGE_IDLE;
    saved_timeout = mytimeout;

    if (has_idle) {
      /* special timeout to terminate the IDLE and re-issue it
       * at least every 28 minutes:
       * (the server may have an inactivity timeout) */
      mytimeout = 1680; /* 28 min */
      /* enter IDLE mode */
      ok = gen_transact(sock, "IDLE");

      if (ok == PS_IDLETIMEOUT) {
          /* send "DONE" continuation */
          SockWrite(sock, "DONE\r\n", 6);
          if (outlevel >= O_MONITOR)
            report(stdout, "IMAP> DONE\n");
      } else
          /* not idle timeout */
          return ok;
    } else {  /* no idle support, fake it */
      /* when faking an idle, we can't assume the server will
       * send us the new messages out of the blue (RFC2060);
       * this timeout is potentially the delay before we notice
       * new mail (can be small since NOOP checking is cheap) */
      mytimeout = 28;
      ok = gen_transact(sock, "NOOP");
      /* if there's an error (not likely) or we just found mail (stage 
       * has changed, timeout has also been restored), we're done */
      if (ok != 0 || stage != STAGE_IDLE)
          return(ok);

      /* wait (briefly) for an unsolicited status update */
      ok = imap_ok(sock, NULL);
      /* again, this is new mail or an error */
      if (ok != PS_IDLETIMEOUT)
          return(ok);
    }

    /* restore normal timeout value */
    mytimeout = saved_timeout;
    stage = STAGE_FETCH;

    /* get OK IDLE message */
    if (has_idle)
        return imap_ok(sock, NULL);

    return PS_SUCCESS;
}

static int imap_getrange(int sock, 
                   struct query *ctl, 
                   const char *folder, 
                   int *countp, int *newp, int *bytes)
/* get range of messages to be fetched */
{
    int ok;
    char buf[MSGBUFSIZE+1], *cp;

    /* find out how many messages are waiting */
    *bytes = -1;

    if (pass > 1)
    {
      /* 
       * We have to have an expunge here, otherwise the re-poll will
       * infinite-loop picking up un-expunged messages -- unless the
       * expunge period is one and we've been nuking each message 
       * just after deletion.
       */
      ok = 0;
      if (deletions) {
          ok = internal_expunge(sock);
          if (ok)
          {
            report(stderr, GT_("expunge failed\n"));
            return(ok);
          }
      }

      /*
       * recentcount is already set here by the last imap command which
       * returned RECENT on detecting new mail. if recentcount is 0, wait
       * for new mail.
       */

      /* some servers do not report RECENT after an EXPUNGE. this check
       * forces an incorrect recentcount to be ignored. */
      if (recentcount > count)
          recentcount = 0;
      /* this is a while loop because imap_idle() might return on other
       * mailbox changes also */
      while (recentcount == 0 && do_idle) {
          smtp_close(ctl, 1);
          ok = imap_idle(sock);
          if (ok)
          {
            report(stderr, GT_("re-poll failed\n"));
            return(ok);
          }
      }
      /* if recentcount is 0, return no mail */
      if (recentcount == 0)
            count = 0;
      if (outlevel >= O_DEBUG)
          report(stdout, GT_("%d messages waiting after re-poll\n"), count);
    }
    else
    {
      count = 0;
      ok = gen_transact(sock, 
                    check_only ? "EXAMINE \"%s\"" : "SELECT \"%s\"",
                    folder ? folder : "INBOX");
      if (ok != 0)
      {
          report(stderr, GT_("mailbox selection failed\n"));
          return(ok);
      }
      else if (outlevel >= O_DEBUG)
          report(stdout, GT_("%d messages waiting after first poll\n"), count);

      /* no messages?  then we may need to idle until we get some */
      while (count == 0 && do_idle) {
          ok = imap_idle(sock);
          if (ok)
          {
            report(stderr, GT_("re-poll failed\n"));
            return(ok);
          }
      }

      /*
       * We should have an expunge here to
       * a) avoid fetching deleted mails during 'fetchall'
       * b) getting a wrong count of mails during 'no fetchall'
       */
      if (!check_only && !ctl->keep && count > 0)
      {
          ok = internal_expunge(sock);
          if (ok)
          {
            report(stderr, GT_("expunge failed\n"));
            return(ok);
          }
          if (outlevel >= O_DEBUG)
            report(stdout, GT_("%d messages waiting after expunge\n"), count);
      }
    }

    *countp = count;
    recentcount = 0;
    startcount = 1;

    /* OK, now get a count of unseen messages and their indices */
    if (!ctl->fetchall && count > 0)
    {
      if (unseen_messages)
          free(unseen_messages);
      unseen_messages = xmalloc(count * sizeof(unsigned int));
      memset(unseen_messages, 0, count * sizeof(unsigned int));
      unseen = 0;

      /* don't count deleted messages, in case user enabled keep last time */
      gen_send(sock, "SEARCH UNSEEN NOT DELETED");
      do {
          ok = gen_recv(sock, buf, sizeof(buf));
          if (ok != 0)
          {
            report(stderr, GT_("search for unseen messages failed\n"));
            return(PS_PROTOCOL);
          }
          else if ((cp = strstr(buf, "* SEARCH")))
          {
            char  *ep;

            cp += 8;    /* skip "* SEARCH" */
            /* startcount is higher than count so that if there are no
             * unseen messages, imap_getsizes() will not need to do
             * anything! */
            startcount = count + 1;

            while (*cp && unseen < count)
            {
                /* skip whitespace */
                while (*cp && isspace(*cp))
                  cp++;
                if (*cp) 
                {
                  unsigned int um;
                  /*
                   * Message numbers are between 1 and 2^32 inclusive,
                   * so unsigned int is large enough.
                   */
                  um=(unsigned int)strtol(cp,&ep,10);
                  if (um <= count)
                  {
                      unseen_messages[unseen++] = um;
                      if (outlevel >= O_DEBUG)
                        report(stdout, GT_("%u is unseen\n"), um);
                      if (startcount > um)
                        startcount = um;
                  }
                  cp = ep;
                }
            }
          }
      } while
          (tag[0] != '\0' && strncmp(buf, tag, strlen(tag)));

      if (outlevel >= O_DEBUG && unseen > 0)
          report(stdout, GT_("%u is first unseen\n"), startcount);
    } else
      unseen = -1;

    *newp = unseen;
    count = 0;
    expunged = 0;
    deletions = 0;

    return(PS_SUCCESS);
}

static int imap_getpartialsizes(int sock, int first, int last, int *sizes)
/* capture the sizes of messages #first-#last */
{
    char buf [MSGBUFSIZE+1];

    /*
     * Some servers (as in, PMDF5.1-9.1 under OpenVMS 6.1)
     * won't accept 1:1 as valid set syntax.  Some implementors
     * should be taken out and shot for excessive anality.
     *
     * Microsoft Exchange (brain-dead piece of crap that it is) 
     * sometimes gets its knickers in a knot about bodiless messages.
     * You may see responses like this:
     *
     *      fetchmail: IMAP> A0004 FETCH 1:9 RFC822.SIZE
     *      fetchmail: IMAP< * 2 FETCH (RFC822.SIZE 1187)
     *      fetchmail: IMAP< * 3 FETCH (RFC822.SIZE 3954)
     *      fetchmail: IMAP< * 4 FETCH (RFC822.SIZE 1944)
     *      fetchmail: IMAP< * 5 FETCH (RFC822.SIZE 2933)
     *      fetchmail: IMAP< * 6 FETCH (RFC822.SIZE 1854)
     *      fetchmail: IMAP< * 7 FETCH (RFC822.SIZE 34054)
     *      fetchmail: IMAP< * 8 FETCH (RFC822.SIZE 5561)
     *      fetchmail: IMAP< * 9 FETCH (RFC822.SIZE 1101)
     *      fetchmail: IMAP< A0004 NO The requested item could not be found.
     *
     * This means message 1 has only headers.  For kicks and grins
     * you can telnet in and look:
     *      A003 FETCH 1 FULL
     *      A003 NO The requested item could not be found.
     *      A004 fetch 1 rfc822.header
     *      A004 NO The requested item could not be found.
     *      A006 FETCH 1 BODY
     *      * 1 FETCH (BODY ("TEXT" "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 35 3))
     *      A006 OK FETCH completed.
     *
     * To get around this, we terminate the read loop on a NO and count
     * on the fact that the sizes array has been preinitialized with a
     * known-bad size value.
     */

    /* expunges change the fetch numbers */
    first -= expunged;
    last -= expunged;

    if (last == first)
      gen_send(sock, "FETCH %d RFC822.SIZE", last);
    else if (last > first)
      gen_send(sock, "FETCH %d:%d RFC822.SIZE", first, last);
    else /* no unseen messages! */
      return(PS_SUCCESS);
    for (;;)
    {
      unsigned int num, size;
      int ok;
      char *cp;

      if ((ok = gen_recv(sock, buf, sizeof(buf))))
          return(ok);
      /* we want response matching to be case-insensitive */
      for (cp = buf; *cp; cp++)
          *cp = toupper(*cp);
      /* an untagged NO means that a message was not readable */
      if (strstr(buf, "* NO"))
          ;
      else if (strstr(buf, "OK") || strstr(buf, "NO"))
          break;
      else if (sscanf(buf, "* %u FETCH (RFC822.SIZE %u)", &num, &size) == 2) 
      {
          if (num >= first && num <= last)
              sizes[num - first] = size;
          else
            report(stderr, "Warning: ignoring bogus data for message sizes returned by the server.\n");
      }
    }

    return(PS_SUCCESS);
}

static int imap_getsizes(int sock, int count, int *sizes)
/* capture the sizes of all messages */
{
    return imap_getpartialsizes(sock, 1, count, sizes);
}

static int imap_is_old(int sock, struct query *ctl, int number)
/* is the given message old? */
{
    flag seen = TRUE;
    int i;

    /* 
     * Expunges change the fetch numbers, but unseen_messages contains
     * indices from before any expungees were done.  So neither the
     * argument nor the values in message_sequence need to be decremented.
     */

    seen = TRUE;
    for (i = 0; i < unseen; i++)
      if (unseen_messages[i] == number)
      {
          seen = FALSE;
          break;
      }

    return(seen);
}

static char *skip_token(char *ptr)
{
    while(isspace(*ptr)) ptr++;
    while(!isspace(*ptr) && !iscntrl(*ptr)) ptr++;
    while(isspace(*ptr)) ptr++;
    return(ptr);
}

static int imap_fetch_headers(int sock, struct query *ctl,int number,int *lenp)
/* request headers of nth message */
{
    char buf [MSGBUFSIZE+1];
    int     num;

    /* expunges change the fetch numbers */
    number -= expunged;

    /*
     * This is blessed by RFC1176, RFC1730, RFC2060.
     * According to the RFCs, it should *not* set the \Seen flag.
     */
    gen_send(sock, "FETCH %d RFC822.HEADER", number);

    /* looking for FETCH response */
    for (;;) 
    {
      int   ok;
      char  *ptr;

      if ((ok = gen_recv(sock, buf, sizeof(buf))))
          return(ok);
      ptr = skip_token(buf);  /* either "* " or "AXXXX " */
      if (sscanf(ptr, "%d FETCH (%*s {%d}", &num, lenp) == 2)
          break;
      /* try to recover from chronically fucked-up M$ Exchange servers */
      else if (!strncmp(ptr, "NO", 2))
      {
          /* wait for a tagged response */
          if (strstr (buf, "* NO"))
            imap_ok (sock, 0);
          return(PS_TRANSIENT);
      }
      else if (!strncmp(ptr, "BAD", 3))
      {
          /* wait for a tagged response */
          if (strstr (buf, "* BAD"))
            imap_ok (sock, 0);
          return(PS_TRANSIENT);
      }
    }

    if (num != number)
      return(PS_ERROR);
    else
      return(PS_SUCCESS);
}

static int imap_fetch_body(int sock, struct query *ctl, int number, int *lenp)
/* request body of nth message */
{
    char buf [MSGBUFSIZE+1], *cp;
    int     num;

    /* expunges change the fetch numbers */
    number -= expunged;

    /*
     * If we're using IMAP4, we can fetch the message without setting its
     * seen flag.  This is good!  It means that if the protocol exchange
     * craps out during the message, it will still be marked `unseen' on
     * the server.
     *
     * According to RFC2060, and Mark Crispin the IMAP maintainer,
     * FETCH %d BODY[TEXT] and RFC822.TEXT are "functionally 
     * equivalent".  However, we know of at least one server that
     * treats them differently in the presence of MIME attachments;
     * the latter form downloads the attachment, the former does not.
     * The server is InterChange, and the fool who implemented this
     * misfeature ought to be strung up by his thumbs.  
     *
     * When I tried working around this by disabling use of the 4rev1 form,
     * I found that doing this breaks operation with M$ Exchange.
     * Annoyingly enough, Exchange's refusal to cope is technically legal
     * under RFC2062.  Trust Microsoft, the Great Enemy of interoperability
     * standards, to find a way to make standards compliance irritating....
     */
    switch (imap_version)
    {
    case IMAP4rev1:     /* RFC 2060 */
      gen_send(sock, "FETCH %d BODY.PEEK[TEXT]", number);
      break;

    case IMAP4:         /* RFC 1730 */
      gen_send(sock, "FETCH %d RFC822.TEXT.PEEK", number);
      break;

    default:            /* RFC 1176 */
      gen_send(sock, "FETCH %d RFC822.TEXT", number);
      break;
    }

    /* looking for FETCH response */
    do {
      int   ok;

      if ((ok = gen_recv(sock, buf, sizeof(buf))))
          return(ok);
    } while
      (!strstr(buf+4, "FETCH") || sscanf(buf+2, "%d", &num) != 1);

    if (num != number)
      return(PS_ERROR);

    /*
     * Try to extract a length from the FETCH response.  RFC2060 requires
     * it to be present, but at least one IMAP server (Novell GroupWise)
     * botches this.  The overflow check is needed because of a broken
     * server called dbmail that returns huge garbage lengths.
     */
    if ((cp = strchr(buf, '{'))) {
        errno = 0;
      *lenp = (int)strtol(cp + 1, (char **)NULL, 10);
        if (errno == ERANGE && (*lenp == LONG_MAX || *lenp == LONG_MIN))
            *lenp = -1;    /* length is too big/small for us to handle */
    }
    else
      *lenp = -1; /* missing length part in FETCH reponse */

    return(PS_SUCCESS);
}

static int imap_trail(int sock, struct query *ctl, int number)
/* discard tail of FETCH response after reading message text */
{
    /* expunges change the fetch numbers */
    /* number -= expunged; */

    for (;;)
    {
      char buf[MSGBUFSIZE+1];
      int ok;

      if ((ok = gen_recv(sock, buf, sizeof(buf))))
          return(ok);

      /* UW IMAP returns "OK FETCH", Cyrus returns "OK Completed" */
      if (strstr(buf, "OK"))
          break;
    }

    return(PS_SUCCESS);
}

static int imap_delete(int sock, struct query *ctl, int number)
/* set delete flag for given message */
{
    int     ok;

    /* expunges change the fetch numbers */
    number -= expunged;

    /*
     * Use SILENT if possible as a minor throughput optimization.
     * Note: this has been dropped from IMAP4rev1.
     *
     * We set Seen because there are some IMAP servers (notably HP
     * OpenMail) that do message-receipt DSNs, but only when the seen
     * bit is set.  This is the appropriate time -- we get here right
     * after the local SMTP response that says delivery was
     * successful.
     */
    if ((ok = gen_transact(sock,
                  imap_version == IMAP4 
                        ? "STORE %d +FLAGS.SILENT (\\Seen \\Deleted)"
                        : "STORE %d +FLAGS (\\Seen \\Deleted)", 
                  number)))
      return(ok);
    else
      deletions++;

    /*
     * We do an expunge after expunge_period messages, rather than
     * just before quit, so that a line hit during a long session
     * won't result in lots of messages being fetched again during
     * the next session.
     */
    if (NUM_NONZERO(expunge_period) && (deletions % expunge_period) == 0)
      internal_expunge(sock);

    return(PS_SUCCESS);
}

static int imap_mark_seen(int sock, struct query *ctl, int number)
/* mark the given message as seen */
{
    return(gen_transact(sock,
      imap_version == IMAP4
      ? "STORE %d +FLAGS.SILENT (\\Seen)"
      : "STORE %d +FLAGS (\\Seen)",
      number));
}

static int imap_logout(int sock, struct query *ctl)
/* send logout command */
{
    /* if any un-expunged deletions remain, ship an expunge now */
    if (deletions)
      internal_expunge(sock);

#ifdef USE_SEARCH
    /* Memory clean-up */
    if (unseen_messages)
      free(unseen_messages);
#endif /* USE_SEARCH */

    return(gen_transact(sock, "LOGOUT"));
}

const static struct method imap =
{
    "IMAP",       /* Internet Message Access Protocol */
#if INET6_ENABLE
    "imap",
    "imaps",
#else /* INET6_ENABLE */
    143,                /* standard IMAP2bis/IMAP4 port */
    993,                /* ssl IMAP2bis/IMAP4 port */
#endif /* INET6_ENABLE */
    TRUE,         /* this is a tagged protocol */
    FALSE,        /* no message delimiter */
    imap_ok,            /* parse command response */
    imap_getauth, /* get authorization */
    imap_getrange,      /* query range of messages */
    imap_getsizes,      /* get sizes of messages (used for ESMTP SIZE option) */
    imap_getpartialsizes,     /* get sizes of subset of messages (used for ESMTP SIZE option) */
    imap_is_old,  /* no UID check */
    imap_fetch_headers, /* request given message headers */
    imap_fetch_body,    /* request given message body */
    imap_trail,         /* eat message trailer */
    imap_delete,  /* delete the message */
    imap_mark_seen,     /* how to mark a message as seen */
    imap_logout,  /* expunge and exit */
    TRUE,         /* yes, we can re-poll */
};

int doIMAP(struct query *ctl)
/* retrieve messages using IMAP Version 2bis or Version 4 */
{
    return(do_protocol(ctl, &imap));
}

/* imap.c ends here */

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