/*

 * pop3.c -- POP3 protocol methods

 *

 * Copyright 1998 by Eric S. Raymond.

 * For license terms, see the file COPYING in this directory.

 */

#include  "config.h"

#ifdef POP3_ENABLE

#include  <stdio.h>

#include  <string.h>

#include  <ctype.h>

#if defined(HAVE_UNISTD_H)

#include <unistd.h>

#endif

#if defined(STDC_HEADERS)

#include  <stdlib.h>

#endif

#include  <errno.h>

#include  "fetchmail.h"

#include  "socket.h"

#include  "i18n.h"

#ifdef OPIE_ENABLE

#ifdef __cplusplus

extern "C" {

#endif

#include <opie.h>

#ifdef __cplusplus

}

#endif

#endif /* OPIE_ENABLE */

/* global variables: please reinitialize them explicitly for proper

 * working in daemon mode */

/* TODO: session variables to be initialized before server greeting */

#ifdef OPIE_ENABLE

static char lastok[POPBUFSIZE+1];

#endif /* OPIE_ENABLE */

/* session variables initialized in capa_probe() or pop3_getauth() */

flag done_capa = FALSE;

#if defined(GSSAPI)

flag has_gssapi = FALSE;

#endif /* defined(GSSAPI) */

#if defined(KERBEROS_V4) || defined(KERBEROS_V5)

flag has_kerberos = FALSE;

#endif /* defined(KERBEROS_V4) || defined(KERBEROS_V5) */

static flag has_cram = FALSE;

#ifdef OPIE_ENABLE

flag has_otp = FALSE;

#endif /* OPIE_ENABLE */

#ifdef NTLM_ENABLE

flag has_ntlm = FALSE;

#endif /* NTLM_ENABLE */

#ifdef SSL_ENABLE

static flag has_stls = FALSE;

#endif /* SSL_ENABLE */

/* mailbox variables initialized in pop3_getrange() */

static int last;

/* mail variables initialized in pop3_fetch() */

#ifdef SDPS_ENABLE

char *sdps_envfrom;

char *sdps_envto;

#endif /* SDPS_ENABLE */

#ifdef NTLM_ENABLE

#include "ntlm.h"

/*

 * 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_pop3_ntlm(int sock, struct query *ctl,

	int msn_instead /** if true, send AUTH MSN, else send AUTH NTLM */)

{

    char msgbuf[POPBUFSIZE+1];

    int result;

    gen_send(sock, msn_instead ? "AUTH MSN" : "AUTH NTLM");

    if ((result = ntlm_helper(sock, ctl, "POP3")))

	return result;

    if ((result = gen_recv (sock, msgbuf, sizeof msgbuf)))

	return result;

    if (strstr (msgbuf, "OK"))

	return PS_SUCCESS;

    else

	return PS_AUTHFAIL;

}

#endif /* NTLM */

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

static int pop3_ok (int sock, char *argbuf)

/* parse command response */

{

    int ok;

    char buf [POPBUFSIZE+1];

    char *bufp;

    if ((ok = gen_recv(sock, buf, sizeof(buf))) == 0)

    {	bufp = buf;

	if (*bufp == '+' || *bufp == '-')

	    bufp++;

	else

	    return(PS_PROTOCOL);

	while (isalpha((unsigned char)*bufp))

	    bufp++;

	if (*bufp)

	  *(bufp++) = '\0';

	if (strcmp(buf,"+OK") == 0)

	{

#ifdef OPIE_ENABLE

	    strcpy(lastok, bufp);

#endif /* OPIE_ENABLE */

	    ok = 0;

	}

	else if (strncmp(buf,"-ERR", 4) == 0)

	{

	    if (stage == STAGE_FETCH)

		ok = PS_TRANSIENT;

	    else if (stage > STAGE_GETAUTH)

		ok = PS_PROTOCOL;

	    /*

	     * We're checking for "lock busy", "unable to lock", 

	     * "already locked", "wait a few minutes" etc. here. 

	     * This indicates that we have to wait for the server to

	     * unwedge itself before we can poll again.

	     *

	     * PS_LOCKBUSY check empirically verified with two recent

	     * versions of the Berkeley popper; QPOP (version 2.2)  and

	     * QUALCOMM Pop server derived from UCB (version 2.1.4-R3)

	     * These are caught by the case-indifferent "lock" check.

	     * The "wait" catches "mail storage services unavailable,

	     * wait a few minutes and try again" on the InterMail server.

	     *

	     * If these aren't picked up on correctly, fetchmail will 

	     * think there is an authentication failure and wedge the

	     * connection in order to prevent futile polls.

	     *

	     * Gad, what a kluge.

	     */

	    else if (strstr(bufp,"lock")

		     || strstr(bufp,"Lock")

		     || strstr(bufp,"LOCK")

		     || strstr(bufp,"wait")

		     /* these are blessed by RFC 2449 */

		     || strstr(bufp,"[IN-USE]")||strstr(bufp,"[LOGIN-DELAY]"))

		ok = PS_LOCKBUSY;

	    else if ((strstr(bufp,"Service")

		     || strstr(bufp,"service"))

			 && (strstr(bufp,"unavailable")))

		ok = PS_SERVBUSY;

	    else

		ok = PS_AUTHFAIL;

	    /*

	     * We always want to pass the user lock-busy messages, because

	     * they're red flags.  Other stuff (like AUTH failures on non-

	     * RFC1734 servers) only if we're debugging.

	     */

	    if (*bufp && (ok == PS_LOCKBUSY || outlevel >= O_MONITOR))

	      report(stderr, "%s\n", bufp);

	}

	else

	    ok = PS_PROTOCOL;

#if POPBUFSIZE > MSGBUFSIZE

#error "POPBUFSIZE must not be larger than MSGBUFSIZE"

#endif

	if (argbuf != NULL)

	    strcpy(argbuf,bufp);

    }

    return(ok);

}

static int capa_probe(int sock)

/* probe the capabilities of the remote server */

{

    int	ok;

    if (done_capa) {

	return PS_SUCCESS;

    }

#if defined(GSSAPI)

    has_gssapi = FALSE;

#endif /* defined(GSSAPI) */

#if defined(KERBEROS_V4) || defined(KERBEROS_V5)

    has_kerberos = FALSE;

#endif /* defined(KERBEROS_V4) || defined(KERBEROS_V5) */

    has_cram = FALSE;

#ifdef OPIE_ENABLE

    has_otp = FALSE;

#endif /* OPIE_ENABLE */

#ifdef NTLM_ENABLE

    has_ntlm = FALSE;

#endif /* NTLM_ENABLE */

    ok = gen_transact(sock, "CAPA");

    if (ok == PS_SUCCESS)

    {

	char buffer[64];

	/* determine what authentication methods we have available */

	while ((ok = gen_recv(sock, buffer, sizeof(buffer))) == 0)

	{

	    if (DOTLINE(buffer))

		break;

#ifdef SSL_ENABLE

	    if (strstr(buffer, "STLS"))

		has_stls = TRUE;

#endif /* SSL_ENABLE */

#if defined(GSSAPI)

	    if (strstr(buffer, "GSSAPI"))

		has_gssapi = TRUE;

#endif /* defined(GSSAPI) */

#if defined(KERBEROS_V4)

	    if (strstr(buffer, "KERBEROS_V4"))

		has_kerberos = TRUE;

#endif /* defined(KERBEROS_V4)  */

#ifdef OPIE_ENABLE

	    if (strstr(buffer, "X-OTP"))

		has_otp = TRUE;

#endif /* OPIE_ENABLE */

#ifdef NTLM_ENABLE

	    if (strstr(buffer, "NTLM"))

		has_ntlm = TRUE;

#endif /* NTLM_ENABLE */

	    if (strstr(buffer, "CRAM-MD5"))

		has_cram = TRUE;

	}

    }

    done_capa = TRUE;

    return(ok);

}

static void set_peek_capable(struct query *ctl)

{

    /* we're peek-capable means that the use of TOP is enabled,

     * see pop3_fetch for details - short story, we can use TOP if

     * we have a means of reliably tracking which mail we need to

     * refetch should the connection abort in the middle.

     * fetchall forces RETR, as does keep without UIDL */

    peek_capable = !ctl->fetchall && (!ctl->keep || ctl->server.uidl);

}

static int pop3_getauth(int sock, struct query *ctl, char *greeting)

/* apply for connection authorization */

{

    int ok;

    char *start,*end;

    char *msg;

#ifdef OPIE_ENABLE

    char *challenge;

#endif /* OPIE_ENABLE */

#ifdef SSL_ENABLE

    flag connection_may_have_tls_errors = FALSE;

#endif /* SSL_ENABLE */

    done_capa = FALSE;

#if defined(GSSAPI)

    has_gssapi = FALSE;

#endif /* defined(GSSAPI) */

#if defined(KERBEROS_V4) || defined(KERBEROS_V5)

    has_kerberos = FALSE;

#endif /* defined(KERBEROS_V4) || defined(KERBEROS_V5) */

    has_cram = FALSE;

#ifdef OPIE_ENABLE

    has_otp = FALSE;

#endif /* OPIE_ENABLE */

#ifdef SSL_ENABLE

    has_stls = FALSE;

#endif /* SSL_ENABLE */

    /* Set this up before authentication quits early. */

    set_peek_capable(ctl);

    /* Hack: allow user to force RETR. */

    if (peek_capable && getenv("FETCHMAIL_POP3_FORCE_RETR")) {

	peek_capable = 0;

    }

    /*

     * The "Maillennium POP3/PROXY server" deliberately truncates

     * TOP replies after c. 64 or 80 kByte (we have varying reports), so

     * disable TOP. Comcast once spewed marketing babble to the extent

     * of protecting Outlook -- pretty overzealous to break a protocol

     * for that that Microsoft could have read, too. Comcast aren't

     * alone in using this software though.

     * <http://lists.ccil.org/pipermail/fetchmail-friends/2004-April/008523.html>

     * (Thanks to Ed Wilts for reminding me of that.)

     *

     * The warning is printed once per server, until fetchmail exits.

     * It will be suppressed when --fetchall or other circumstances make

     * us use RETR anyhow.

     *

     * Matthias Andree

     */

    if (peek_capable && strstr(greeting, "Maillennium POP3/PROXY server")) {

	if ((ctl->server.workarounds & WKA_TOP) == 0) {

	    report(stdout, GT_("Warning: \"Maillennium POP3/PROXY server\" found, using RETR command instead of TOP.\n"));

	    ctl->server.workarounds |= WKA_TOP;

	}

	peek_capable = 0;

    }

    if (ctl->server.authenticate == A_SSH) {

        return PS_SUCCESS;

    }

#ifdef SDPS_ENABLE

    /*

     * This needs to catch both demon.co.uk and demon.net.

     * If we see either, and we're in multidrop mode, try to use

     * the SDPS *ENV extension.

     */

    if (!(ctl->server.sdps) && MULTIDROP(ctl) && strstr(greeting, "demon."))

        ctl->server.sdps = TRUE;

#endif /* SDPS_ENABLE */

   switch (ctl->server.protocol) {

    case P_POP3:

#ifdef RPA_ENABLE

	/* XXX FIXME: AUTH probing (RFC1734) should become global */

	/* CompuServe POP3 Servers as of 990730 want AUTH first for RPA */

	if (strstr(ctl->remotename, "@compuserve.com"))

	{

	    /* AUTH command should return a list of available mechanisms */

	    if (gen_transact(sock, "AUTH") == 0)

	    {

		char buffer[10];

		flag has_rpa = FALSE;

		while ((ok = gen_recv(sock, buffer, sizeof(buffer))) == 0)

		{

		    if (DOTLINE(buffer))

			break;

		    if (strncasecmp(buffer, "rpa", 3) == 0)

			has_rpa = TRUE;

		}

		if (has_rpa && !POP3_auth_rpa(ctl->remotename, 

					      ctl->password, sock))

		    return(PS_SUCCESS);

	    }

	    return(PS_AUTHFAIL);

	}

#endif /* RPA_ENABLE */

	/*

	 * CAPA command may return a list including available

	 * authentication mechanisms and STLS capability.

	 *

	 * If it doesn't, no harm done, we just fall back to a plain

	 * login -- if the user allows it.

	 *

	 * Note that this code latches the server's authentication type,

	 * so that in daemon mode the CAPA check only needs to be done

	 * once at start of run.

	 *

	 * If CAPA fails, then force the authentication method to

	 * PASSWORD, switch off opportunistic and repoll immediately.

	 * If TLS is mandatory, fail up front.

	 */

	if ((ctl->server.authenticate == A_ANY) ||

		(ctl->server.authenticate == A_GSSAPI) ||

		(ctl->server.authenticate == A_KERBEROS_V4) ||

		(ctl->server.authenticate == A_KERBEROS_V5) ||

		(ctl->server.authenticate == A_OTP) ||

		(ctl->server.authenticate == A_CRAM_MD5) ||

		maybe_tls(ctl))

	{

	    if ((ok = capa_probe(sock)) != PS_SUCCESS)

		/* we are in STAGE_GETAUTH => failure is PS_AUTHFAIL! */

		if (ok == PS_AUTHFAIL ||

		    /* Some servers directly close the socket. However, if we

		     * have already authenticated before, then a previous CAPA

		     * must have succeeded. In that case, treat this as a

		     * genuine socket error and do not change the auth method.

		     */

		    (ok == PS_SOCKET && !ctl->wehaveauthed))

		{

#ifdef SSL_ENABLE

		    if (must_tls(ctl)) {

			/* fail with mandatory STLS without repoll */

			report(stderr, GT_("TLS is mandatory for this session, but server refused CAPA command.\n"));

			report(stderr, GT_("The CAPA command is however necessary for TLS.\n"));

			return ok;

		    } else if (maybe_tls(ctl)) {

			/* defeat opportunistic STLS */

			xfree(ctl->sslproto);

			ctl->sslproto = xstrdup("");

		    }

#endif

		    /* If strong authentication was opportunistic, retry without, else fail. */

		    switch (ctl->server.authenticate) {

			case A_ANY:

			    ctl->server.authenticate = A_PASSWORD;

			    /* FALLTHROUGH */

			case A_PASSWORD: /* this should only happen with TLS enabled */

			    return PS_REPOLL;

			default:

			    return PS_AUTHFAIL;

		    }

		}

	}

#ifdef SSL_ENABLE

	if (maybe_tls(ctl)) {

	    char *commonname;

	    commonname = ctl->server.pollname;

	    if (ctl->server.via)

		commonname = ctl->server.via;

	    if (ctl->sslcommonname)

		commonname = ctl->sslcommonname;

	   if (has_stls

		   || must_tls(ctl)) /* if TLS is mandatory, ignore capabilities */

	   {

	       /* Use "tls1" rather than ctl->sslproto because tls1 is the only

		* protocol that will work with STARTTLS.  Don't need to worry

		* whether TLS is mandatory or opportunistic unless SSLOpen() fails

		* (see below). */

	       if (gen_transact(sock, "STLS") == PS_SUCCESS

		       && (set_timeout(mytimeout), SSLOpen(sock, ctl->sslcert, ctl->sslkey, "tls1", ctl->sslcertck,

			   ctl->sslcertfile, ctl->sslcertpath, ctl->sslfingerprint, commonname,

			   ctl->server.pollname, &ctl->remotename)) != -1)

	       {

		   /*

		    * 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."

		    *

		    * Now that we're confident in our TLS connection we can

		    * guarantee a secure capability re-probe.

		    */

		   set_timeout(0);

		   done_capa = FALSE;

		   ok = capa_probe(sock);

		   if (ok != PS_SUCCESS) {

		       return ok;

		   }

		   if (outlevel >= O_VERBOSE)

		   {

		       report(stdout, GT_("%s: upgrade to TLS succeeded.\n"), commonname);

		   }

	       } else if (must_tls(ctl)) {

		   /* Config required TLS but we couldn't guarantee it, so we must

		    * stop. */

		   set_timeout(0);

		   report(stderr, GT_("%s: upgrade to TLS failed.\n"), commonname);

		   return PS_SOCKET;

	       } else {

		   /* We don't know whether the connection is usable, and there's

		    * no command we can reasonably issue to test it (NOOP isn't

		    * allowed til post-authentication), so leave it in an unknown

		    * state, mark it as such, and check more carefully if things

		    * go wrong when we try to authenticate. */

		   set_timeout(0);

		   connection_may_have_tls_errors = TRUE;

		   if (outlevel >= O_VERBOSE)

		   {

		       report(stdout, GT_("%s: opportunistic upgrade to TLS failed, trying to continue.\n"), commonname);

		   }

	       }

	   }

	} /* maybe_tls() */

#endif /* SSL_ENABLE */

	/*

	 * OK, we have an authentication type now.

	 */

#if defined(KERBEROS_V4)

	/* 

	 * Servers doing KPOP have to go through a dummy login sequence

	 * rather than doing SASL.

	 */

	if (has_kerberos &&

	    ctl->server.service && (strcmp(ctl->server.service, KPOP_PORT)!=0)

	    && (ctl->server.authenticate == A_KERBEROS_V4

	     || ctl->server.authenticate == A_KERBEROS_V5

	     || ctl->server.authenticate == A_ANY))

	{

	    ok = do_rfc1731(sock, "AUTH", ctl->server.truename);

	    if (ok == PS_SUCCESS || ctl->server.authenticate != A_ANY)

		break;

	}

#endif /* defined(KERBEROS_V4) || defined(KERBEROS_V5) */

#if defined(GSSAPI)

	if (has_gssapi &&

	    (ctl->server.authenticate == A_GSSAPI ||

	    (ctl->server.authenticate == A_ANY

	     && check_gss_creds("pop", ctl->server.truename) == PS_SUCCESS)))

	{

	    ok = do_gssauth(sock,"AUTH","pop",ctl->server.truename,ctl->remotename);

	    if (ok == PS_SUCCESS || ctl->server.authenticate != A_ANY)

		break;

	}

#endif /* defined(GSSAPI) */

#ifdef OPIE_ENABLE

	if (has_otp &&

	    (ctl->server.authenticate == A_OTP ||

	     ctl->server.authenticate == A_ANY))

	{

	    ok = do_otp(sock, "AUTH", ctl);

	    if (ok == PS_SUCCESS || ctl->server.authenticate != A_ANY)

		break;

	}

#endif /* OPIE_ENABLE */

#ifdef NTLM_ENABLE

    /* MSN servers require the use of NTLM (MSN) authentication */

    if (!strcasecmp(ctl->server.pollname, "pop3.email.msn.com") ||

	    ctl->server.authenticate == A_MSN)

	return (do_pop3_ntlm(sock, ctl, 1) == 0) ? PS_SUCCESS : PS_AUTHFAIL;

    if (ctl->server.authenticate == A_NTLM || (has_ntlm && ctl->server.authenticate == A_ANY)) {

	ok = do_pop3_ntlm(sock, ctl, 0);

        if (ok == 0 || ctl->server.authenticate != A_ANY)

	    break;

    }

#else

    if (ctl->server.authenticate == A_NTLM || ctl->server.authenticate == A_MSN)

    {

	report(stderr,

	   GT_("Required NTLM capability not compiled into fetchmail\n"));

    }

#endif

 	if (ctl->server.authenticate == A_CRAM_MD5 || 

	    (has_cram && ctl->server.authenticate == A_ANY))

	{

	    ok = do_cram_md5(sock, "AUTH", ctl, NULL);

	    if (ok == PS_SUCCESS || ctl->server.authenticate != A_ANY)

		break;

	}

	/* ordinary validation, no one-time password or RPA */ 

	if ((ok = gen_transact(sock, "USER %s", ctl->remotename)))

	    break;

#ifdef OPIE_ENABLE

	/* see RFC1938: A One-Time Password System */

	if ((challenge = strstr(lastok, "otp-"))) {

	  char response[OPIE_RESPONSE_MAX+1];

	  int i;

	  char *n = xstrdup("");

	  i = opiegenerator(challenge, !strcmp(ctl->password, "opie") ? n : ctl->password, response);

	  free(n);

	  if ((i == -2) && !run.poll_interval) {

	    char secret[OPIE_SECRET_MAX+1];

	    fprintf(stderr, GT_("Secret pass phrase: "));

	    if (opiereadpass(secret, sizeof(secret), 0))

	      i = opiegenerator(challenge,  secret, response);

	    memset(secret, 0, sizeof(secret));

	  };

	  if (i) {

	    ok = PS_ERROR;

	    break;

	  };

	  ok = gen_transact(sock, "PASS %s", response);

	  break;

	}

#endif /* OPIE_ENABLE */

	/* KPOP uses out-of-band authentication and does not check what

	 * we send here, so send some random fixed string, to avoid

	 * users switching *to* KPOP accidentally revealing their

	 * password */

	if ((ctl->server.authenticate == A_ANY

		    || ctl->server.authenticate == A_KERBEROS_V4

		    || ctl->server.authenticate == A_KERBEROS_V5)

		&& (ctl->server.service != NULL

		    && strcmp(ctl->server.service, KPOP_PORT) == 0))

	{

	    ok = gen_transact(sock, "PASS krb_ticket");

	    break;

	}

	/* check if we are actually allowed to send the password */

	if (ctl->server.authenticate == A_ANY

		|| ctl->server.authenticate == A_PASSWORD) {

	    strlcpy(shroud, ctl->password, sizeof(shroud));

	    ok = gen_transact(sock, "PASS %s", ctl->password);

	} else {

	    report(stderr, GT_("We've run out of allowed authenticators and cannot continue.\n"));

	    ok = PS_AUTHFAIL;

	}

	memset(shroud, 0x55, sizeof(shroud));

	shroud[0] = '\0';

	break;

    case P_APOP:

	/* build MD5 digest from greeting timestamp + password */

	/* find start of timestamp */

	for (start = greeting;  *start != 0 && *start != '<';  start++)

	    continue;

	if (*start == 0) {

	    report(stderr,

		   GT_("Required APOP timestamp not found in greeting\n"));

	    return(PS_AUTHFAIL);

	}

	/* find end of timestamp */

	for (end = start;  *end != 0  && *end != '>';  end++)

	    continue;

	if (*end == 0 || end == start + 1) {

	    report(stderr, 

		   GT_("Timestamp syntax error in greeting\n"));

	    return(PS_AUTHFAIL);

	}

	else

	    *++end = '\0';

	/* SECURITY: 2007-03-17

	 * Strictly validating the presented challenge for RFC-822

	 * conformity (it must be a msg-id in terms of that standard) is

	 * supposed to make attacks against the MD5 implementation

	 * harder[1]

	 *

	 * [1] "Security vulnerability in APOP authentication",

	 *     Gaëtan Leurent, fetchmail-devel, 2007-03-17 */

	if (!rfc822_valid_msgid((unsigned char *)start)) {

	    report(stderr,

		    GT_("Invalid APOP timestamp.\n"));

	    return PS_AUTHFAIL;

	}

	/* copy timestamp and password into digestion buffer */

	msg = (char *)xmalloc((end-start+1) + strlen(ctl->password) + 1);

	strcpy(msg,start);

	strcat(msg,ctl->password);

	strcpy((char *)ctl->digest, MD5Digest((unsigned char *)msg));

	free(msg);

	ok = gen_transact(sock, "APOP %s %s", ctl->remotename, (char *)ctl->digest);

	break;

    case P_RPOP:

	if ((ok = gen_transact(sock,"USER %s", ctl->remotename)) == 0) {

	    strlcpy(shroud, ctl->password, sizeof(shroud));

	    ok = gen_transact(sock, "RPOP %s", ctl->password);

	    memset(shroud, 0x55, sizeof(shroud));

	    shroud[0] = '\0';

	}

	break;

    default:

	report(stderr, GT_("Undefined protocol request in POP3_auth\n"));

	ok = PS_ERROR;

    }

#ifdef SSL_ENABLE

    /* this is for servers which claim to support TLS, but actually

     * don't! */

    if (connection_may_have_tls_errors

		    && (ok == PS_SOCKET || ok == PS_PROTOCOL))

    {

	xfree(ctl->sslproto);

	ctl->sslproto = xstrdup("");

	/* repoll immediately without TLS */

	ok = PS_REPOLL;

    }

#endif

    if (ok != 0)

    {

	/* maybe we detected a lock-busy condition? */

        if (ok == PS_LOCKBUSY)

	    report(stderr, GT_("lock busy!  Is another session active?\n")); 

	return(ok);

    }

/* Disable the sleep. Based on patch by Brian Candler 2004-04-19/2004-11-08,

 * accepted by Matthias Andree.

 *

 * Rationale: the server must have locked the spool before returning +OK;

 * this sleep just wastes time and hence, for modem and GSM CSD users, money. */

#ifdef WANT_BOGUS

    /*

     * Empirical experience shows some server/OS combinations

     * may need a brief pause even after any lockfiles on the

     * server are released, to give the server time to finish

     * copying back very large mailfolders from the temp-file...

     * this is only ever an issue with extremely large mailboxes.

     */

    sleep(3); /* to be _really_ safe, probably need sleep(5)! */

#endif

    /* we're approved */

    return(PS_SUCCESS);

}

/* cut off C string at first POSIX space */

static void trim(char *s) {

    s += strcspn(s, POSIX_space);

    s[0] = '\0';

}

/* XXX FIXME: using the Message-ID is unsafe, some messages (spam,

 * broken messages) do not have Message-ID headers, and messages without

 * those appear to break this code and cause fetchmail (at least version

 * 6.2.3) to not delete such messages properly after retrieval.

 * See Sourceforge Bug #780933.

 *

 * The other problem is that the TOP command itself is optional, too... */

static int pop3_gettopid(int sock, int num , char *id, size_t idsize)

{

    int ok;

    int got_it;

    char buf [POPBUFSIZE+1];

    snprintf(buf, sizeof(buf), "TOP %d 1", num);

    if ((ok = gen_transact(sock, "%s", buf)) != 0)

       return ok;

    got_it = 0;

    while (gen_recv(sock, buf, sizeof(buf)) == 0)

    {

	if (DOTLINE(buf))

	    break;

	if (!got_it && 0 == strncasecmp("Message-Id:", buf, 11)) {

	    char *p = buf + 11;

	    got_it = 1;

	    p += strspn(p, POSIX_space);

	    strlcpy(id, p, idsize);

	    trim(id);

	}

    }

    /* XXX FIXME: do not return success here if no Message-ID header was

     * found. */

    return 0;

}

/** Parse the UID response (leading +OK must have been

 * stripped off) in buf, store the number in gotnum, and store the ID

 * into the caller-provided buffer "id" of size "idsize".

 * Returns PS_SUCCESS or PS_PROTOCOL for failure. */

static int parseuid(const char *buf, unsigned long *gotnum, char *id, size_t idsize)

{

    const char *i;

    char *j;

    /* skip leading blanks ourselves */

    i = buf;

    i += strspn(i, POSIX_space);

    errno = 0;

    *gotnum = strtoul(i, &j, 10);

    if (j == i || !*j || errno || NULL == strchr(POSIX_space, *j)) {

	report(stderr, GT_("Cannot handle UIDL response from upstream server.\n"));

	return PS_PROTOCOL;

    }

    j += strspn(j, POSIX_space);

    strlcpy(id, j, idsize);

    trim(id);

    return PS_SUCCESS;

}

/** request UIDL for single message \a num and stuff the result into the

 * buffer \a id which can hold \a idsize bytes */

static int pop3_getuidl(int sock, int num, char *id /** output */, size_t idsize)

{

    int ok;

    char buf [POPBUFSIZE+1];

    unsigned long gotnum;

    gen_send(sock, "UIDL %d", num);

    if ((ok = pop3_ok(sock, buf)) != 0)

	return(ok);

    if ((ok = parseuid(buf, &gotnum, id, idsize)))

	return ok;

    if (gotnum != (unsigned long)num) {

	report(stderr, GT_("Server responded with UID for wrong message.\n"));

	return PS_PROTOCOL;

    }

    return(PS_SUCCESS);

}

static int pop3_fastuidl( int sock,  struct query *ctl, unsigned int count, int *newp)

{

    int ok;

    unsigned int first_nr, last_nr, try_nr;

    char id [IDLEN+1];

    struct idlist *savep = NULL; /** pointer to cache save_str result, speeds up saves */

    first_nr = 0;

    last_nr = count + 1;

    while (first_nr < last_nr - 1)

    {

	struct idlist	*newl;

	try_nr = (first_nr + last_nr) / 2;

	if ((ok = pop3_getuidl(sock, try_nr, id, sizeof(id))) != 0)

	    return ok;

	if ((newl = str_in_list(&ctl->oldsaved, id, FALSE)))

	{

	    flag mark = newl->val.status.mark;

	    if (mark == UID_DELETED || mark == UID_EXPUNGED)

	    {

		if (outlevel >= O_VERBOSE)

		    report(stderr, GT_("id=%s (num=%u) was deleted, but is still present!\n"), id, try_nr);

		/* just mark it as seen now! */

		newl->val.status.mark = mark = UID_SEEN;

	    }

	    /* narrow the search region! */

	    if (mark == UID_UNSEEN)

	    {

		if (outlevel >= O_DEBUG)

		    report(stdout, GT_("%u is unseen\n"), try_nr);

		last_nr = try_nr;

	    }

	    else

		first_nr = try_nr;

	    /* save the number */

	    newl->val.status.num = try_nr;

	}

	else

	{

	    if (outlevel >= O_DEBUG)

		report(stdout, GT_("%u is unseen\n"), try_nr);

	    last_nr = try_nr;

	    /* save it */

	    savep = save_str(savep ? &savep : &ctl->oldsaved, id, UID_UNSEEN);

	    savep->val.status.num = try_nr;

	}

    }

    if (outlevel >= O_DEBUG && last_nr <= count)

	report(stdout, GT_("%u is first unseen\n"), last_nr);

    /* update last! */

    *newp = count - first_nr;

    last = first_nr;

    return 0;

}

static int pop3_slowuidl( int sock,  struct query *ctl, int *countp, int *newp)

{

    /* XXX FIXME: this code is severely broken. A Cc:d mailing list

     * message will arrive twice with the same Message-ID, so this

     * slowuidl code will break. Same goes for messages without

     * Message-ID headers at all. This code would best be removed. */

    /* This approach tries to get the message headers from the

     * remote hosts and compares the message-id to the already known

     * ones:

     *  + if the first message containes a new id, all messages on

     *    the server will be new

     *  + if the first is known, try to estimate the last known message

     *    on the server and check. If this works you know the total number

     *    of messages to get.

     *  + Otherwise run a binary search to determine the last known message

     */

    int ok, nolinear = 0;

    int first_nr, list_len, try_id, try_nr, add_id;

    int num;

    char id [IDLEN+1];

    if ((ok = pop3_gettopid(sock, 1, id, sizeof(id))) != 0)

	return ok;

    if( ( first_nr = str_nr_in_list(&ctl->oldsaved, id) ) == -1 ) {

	/* the first message is unknown -> all messages are new */

	*newp = *countp;	

	return 0;

    }

    /* check where we expect the latest known message */

    list_len = count_list( &ctl->oldsaved );

    try_id = list_len  - first_nr; /* -1 + 1 */

    if( try_id > 1 ) {

	if( try_id <= *countp ) {

	    if ((ok = pop3_gettopid(sock, try_id, id, sizeof(id))) != 0)

		return ok;

	    try_nr = str_nr_last_in_list(&ctl->oldsaved, id);

	} else {

	    try_id = *countp+1;

	    try_nr = -1;

	}

	if( try_nr != list_len -1 ) {

	    /* some messages inbetween have been deleted... */

	    if( try_nr == -1 ) {

		nolinear = 1;

		for( add_id = 1<<30; add_id > try_id-1; add_id >>= 1 )

		    ;

		for( ; add_id; add_id >>= 1 ) {

		    if( try_nr == -1 ) {

			if( try_id - add_id <= 1 ) {

			    continue;

			}

			try_id -= add_id;

		    } else 

			try_id += add_id;

		    if ((ok = pop3_gettopid(sock, try_id, id, sizeof(id))) != 0)

			return ok;

		    try_nr = str_nr_in_list(&ctl->oldsaved, id);

		}

		if( try_nr == -1 ) {

		    try_id--;

		}

	    } else {

		report(stderr, 

		       GT_("Messages inserted into list on server. Cannot handle this.\n"));

		return -1;

	    }

	} 

    }

    /* the first try_id messages are known -> copy them to the newsaved list */

    for( num = first_nr; num < list_len; num++ )

    {

	struct idlist	*newl = save_str(&ctl->newsaved, 

				str_from_nr_list(&ctl->oldsaved, num),

				UID_UNSEEN);

	newl->val.status.num = num - first_nr + 1;

    }

    if( nolinear ) {

	free_str_list(&ctl->oldsaved);

	ctl->oldsaved = 0;

	last = try_id;

    }

    *newp = *countp - try_id;

    return 0;

}

static int pop3_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 [POPBUFSIZE+1];

    (void)folder;

    /* Ensure that the new list is properly empty */

    ctl->newsaved = (struct idlist *)NULL;

#ifdef MBOX

    /* Alain Knaff suggests this, but it's not RFC standard */

    if (folder)

	if ((ok = gen_transact(sock, "MBOX %s", folder)))

	    return ok;

#endif /* MBOX */

    /* get the total message count */

    gen_send(sock, "STAT");

    ok = pop3_ok(sock, buf);

    if (ok == 0) {

	int asgn;

	asgn = sscanf(buf,"%d %d", countp, bytes);

	if (asgn != 2)

		return PS_PROTOCOL;

    } else

	return(ok);

    /*

     * Newer, RFC-1725/1939-conformant POP servers may not have the LAST

     * command.  We work as hard as possible to hide this, but it makes

     * counting new messages intrinsically quadratic in the worst case.

     */

    last = 0;

    *newp = -1;

    /* if there are messages, and UIDL is desired, use UIDL

     * also use UIDL if fetchall is unset */

    if (*countp > 0 && (!ctl->fetchall || ctl->server.uidl))

    {

	int fastuidl;

	char id [IDLEN+1];

	/* should we do fast uidl this time? */

	fastuidl = ctl->fastuidl;

	if (*countp > 7 &&		/* linear search is better if there are few mails! */

	    !ctl->fetchall &&		/* with fetchall, all uids are required */

	    !ctl->flush &&		/* with flush, it is safer to disable fastuidl */

	    NUM_NONZERO (fastuidl))

	{

	    if (fastuidl == 1)

		dofastuidl = 1;

	    else

		dofastuidl = ctl->fastuidlcount != 0;

	}

	else

	    dofastuidl = 0;

	if (!ctl->server.uidl) {

	    gen_send(sock, "LAST");

	    ok = pop3_ok(sock, buf);

	} else

	    ok = 1;

	if (ok == 0)

	{

	    /* scan LAST reply */

	    if (sscanf(buf, "%d", &last) == 0)

	    {

		report(stderr, GT_("protocol error\n"));

		return(PS_ERROR);

	    }

	    *newp = (*countp - last);

	}

	else

	{

	    /* do UIDL */

	    if (dofastuidl)

		return(pop3_fastuidl( sock, ctl, *countp, newp));

	    /* grab the mailbox's UID list */

	    if (gen_transact(sock, "UIDL") != 0)

	    {

		/* don't worry, yet! do it the slow way */

		if (pop3_slowuidl(sock, ctl, countp, newp))

		{

		    report(stderr, GT_("protocol error while fetching UIDLs\n"));

		    return(PS_ERROR);

		}

	    }

	    else

	    {

		/* UIDL worked - parse reply */

		unsigned long unum;

		struct idlist *newl = NULL;

		*newp = 0;

		while (gen_recv(sock, buf, sizeof(buf)) == PS_SUCCESS)

		{

		    if (DOTLINE(buf))

			break;

		    if (parseuid(buf, &unum, id, sizeof(id)) == PS_SUCCESS)

		    {

			struct idlist	*old;

			newl = save_str(newl ? &newl : &ctl->newsaved, id, UID_UNSEEN);

			newl->val.status.num = unum;

			if ((old = str_in_list(&ctl->oldsaved, id, FALSE)))

			{

			    flag mark = old->val.status.mark;

			    if (mark == UID_DELETED || mark == UID_EXPUNGED)

			    {

				/* XXX FIXME: switch 3 occurrences from

				 * (int)unum or (unsigned int)unum to

				 * remove the cast and use %lu - not now

				 * though, time for new release */

				if (outlevel >= O_VERBOSE)

				    report(stderr, GT_("id=%s (num=%d) was deleted, but is still present!\n"), id, (int)unum);

				/* just mark it as seen now! */

				old->val.status.mark = mark = UID_SEEN;

			    }

			    newl->val.status.mark = mark;

			    if (mark == UID_UNSEEN)

			    {

				(*newp)++;

				if (outlevel >= O_DEBUG)

				    report(stdout, GT_("%u is unseen\n"), (unsigned int)unum);

			    }

			}

			else

			{

			    (*newp)++;

			    if (outlevel >= O_DEBUG)

				report(stdout, GT_("%u is unseen\n"), (unsigned int)unum);

			    /* add it to oldsaved also! In case, we do not

			     * swap the lists (say, due to socket error),

			     * the same mail will not be downloaded again.

			     */

			    old = save_str(&ctl->oldsaved, id, UID_UNSEEN);

			}

			/* save the number */

			old->val.status.num = unum;

		    } else

			return PS_ERROR;

		} /* multi-line loop for UIDL reply */

	    } /* UIDL parser */

	} /* do UIDL */

    }

    return(PS_SUCCESS);

}

static int pop3_getpartialsizes(int sock, int first, int last, int *sizes)

/* capture the size of message #first */

{

    int	ok = 0, i, num;

    char buf [POPBUFSIZE+1];

    unsigned int size;

    for (i = first; i <= last; i++) {

	gen_send(sock, "LIST %d", i);

	if ((ok = pop3_ok(sock, buf)) != 0)

	    return(ok);

	if (sscanf(buf, "%d %u", &num, &size) == 2) {

	    if (num == i)

		sizes[i - first] = size;

	    else

		/* warn about possible attempt to induce buffer overrun

		 *

		 * we expect server reply message number and requested

		 * message number to match */

		report(stderr, "Warning: ignoring bogus data for message sizes returned by server.\n");

	}

    }

    return(ok);

}

static int pop3_getsizes(int sock, int count, int *sizes)

/* capture the sizes of all messages */

{

    int	ok;

    if ((ok = gen_transact(sock, "LIST")) != 0)

	return(ok);

    else

    {

	char buf [POPBUFSIZE+1];

	while ((ok = gen_recv(sock, buf, sizeof(buf))) == 0)

	{

	    unsigned int num, size;

	    if (DOTLINE(buf))

		break;

	    else if (sscanf(buf, "%u %u", &num, &size) == 2) {

		if (num > 0 && num <= (unsigned)count)

		    sizes[num - 1] = size;

		else

		    /* warn about possible attempt to induce buffer overrun */

		    report(stderr, "Warning: ignoring bogus data for message sizes returned by server.\n");

	    }

	}

	return(ok);

    }

}

static int pop3_is_old(int sock, struct query *ctl, int num)

/* is the given message old? */

{

    struct idlist *newl;

    if (!ctl->oldsaved)

	return (num <= last);

    else if (dofastuidl)

    {

	char id [IDLEN+1];

	if (num <= last)

	    return(TRUE);

	/* in fast uidl, we manipulate the old list only! */

	if ((newl = id_find(&ctl->oldsaved, num)))

	{

	    /* we already have the id! */

	    return(newl->val.status.mark != UID_UNSEEN);

	}

	/* get the uidl first! */

	if (pop3_getuidl(sock, num, id, sizeof(id)) != PS_SUCCESS)

	    return(TRUE);

	if ((newl = str_in_list(&ctl->oldsaved, id, FALSE))) {

	    /* we already have the id! */

	    newl->val.status.num = num;

	    return(newl->val.status.mark != UID_UNSEEN);

	}

	/* save it */

	newl = save_str(&ctl->oldsaved, id, UID_UNSEEN);

	newl->val.status.num = num;

	return(FALSE);

    }

    else

        return ((newl = id_find(&ctl->newsaved, num)) != NULL &&

	    newl->val.status.mark != UID_UNSEEN);

}

#ifdef UNUSED

/*

 * We could use this to fetch headers only as we do for IMAP.  The trouble 

 * is that there's no way to fetch the body only.  So the following RETR 

 * would have to re-fetch the header.  Enough messages have longer headers

 * than bodies to make this a net loss.

 */

static int pop_fetch_headers(int sock, struct query *ctl,int number,int *lenp)

/* request headers of nth message */

{

    int ok;

    char buf[POPBUFSIZE+1];

    gen_send(sock, "TOP %d 0", number);

    if ((ok = pop3_ok(sock, buf)) != 0)

	return(ok);

    *lenp = -1;		/* we got sizes from the LIST response */

    return(PS_SUCCESS);

}

#endif /* UNUSED */

static int pop3_fetch(int sock, struct query *ctl, int number, int *lenp)

/* request nth message */

{

    int ok;

    char buf[POPBUFSIZE+1];

#ifdef SDPS_ENABLE

    /*

     * See http://www.demon.net/helpdesk/producthelp/mail/sdps-tech.html/

     * for a description of what we're parsing here.

     * -- updated 2006-02-22

     */

    if (ctl->server.sdps)

    {

	int	linecount = 0;

	sdps_envfrom = (char *)NULL;

	sdps_envto = (char *)NULL;

	gen_send(sock, "*ENV %d", number);

	do {

	    if (gen_recv(sock, buf, sizeof(buf)))

            {

                break;

            }

            linecount++;

	    switch (linecount) {

	    case 4:

		/* No need to wrap envelope from address */

		/* FIXME: some parts of fetchmail don't handle null

		 * envelope senders, so use <> to mark null sender

		 * as a workaround. */

		if (strspn(buf, " \t") == strlen(buf))

		    strcpy(buf, "<>");

		sdps_envfrom = (char *)xmalloc(strlen(buf)+1);

		strcpy(sdps_envfrom,buf);

		break;

	    case 5:

                /* Wrap address with To: <> so nxtaddr() likes it */

                sdps_envto = (char *)xmalloc(strlen(buf)+7);

                sprintf(sdps_envto,"To: <%s>",buf);

		break;

            }

	} while

	    (!(buf[0] == '.' && (buf[1] == '\r' || buf[1] == '\n' || buf[1] == '\0')));

    }

#else

    (void)ctl;

#endif /* SDPS_ENABLE */

    /*

     * Though the POP RFCs don't document this fact, on almost every

     * POP3 server I know of messages are marked "seen" only at the

     * time the OK response to a RETR is issued.

     *

     * This means we can use TOP to 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.  (Exception: in early 1999 SpryNet's POP3 servers were

     * reported to mark messages seen on a TOP fetch.)

     *

     * However...*don't* do this if we're using keep to suppress deletion!

     * In that case, marking the seen flag is the only way to prevent the

     * message from being re-fetched on subsequent runs.

     *

     * Also use RETR (that means no TOP, no peek) if fetchall is on.

     * This gives us a workaround for servers like usa.net's that bungle

     * TOP.  It's pretty harmless because fetchall guarantees that any

     * message dropped by an interrupted RETR will be picked up on the

     * next poll of the site.

     *

     * We take advantage here of the fact that, according to all the

     * POP RFCs, "if the number of lines requested by the POP3 client

     * is greater than than the number of lines in the body, then the

     * POP3 server sends the entire message.").

     *

     * The line count passed (99999999) is the maximum value CompuServe will

     * accept; it's much lower than the natural value 2147483646 (the maximum

     * twos-complement signed 32-bit integer minus 1) */

    if (!peek_capable)

	gen_send(sock, "RETR %d", number);

    else

	gen_send(sock, "TOP %d 99999999", number);

    if ((ok = pop3_ok(sock, buf)) != 0)

	return(ok);

    *lenp = -1;		/* we got sizes from the LIST response */

    return(PS_SUCCESS);

}

static void mark_uid_seen(struct query *ctl, int number)

/* Tell the UID code we've seen this. */

{

    struct idlist	*sdp;

    if ((sdp = id_find(&ctl->newsaved, number)))

	sdp->val.status.mark = UID_SEEN;

    /* mark it as seen in oldsaved also! In case, we do not swap the lists

     * (say, due to socket error), the same mail will not be downloaded

     * again.

     */

    if ((sdp = id_find(&ctl->oldsaved, number)))

	sdp->val.status.mark = UID_SEEN;

}

static int pop3_delete(int sock, struct query *ctl, int number)

/* delete a given message */

{

    int ok;

    mark_uid_seen(ctl, number);

    /* actually, mark for deletion -- doesn't happen until QUIT time */

    ok = gen_transact(sock, "DELE %d", number);

    if (ok != PS_SUCCESS)

	return(ok);

    delete_str(dofastuidl ? &ctl->oldsaved : &ctl->newsaved, number);

    return(PS_SUCCESS);

}

static int pop3_mark_seen(int sock, struct query *ctl, int number)

/* mark a given message as seen */

{

    (void)sock;

    mark_uid_seen(ctl, number);

    return(PS_SUCCESS);

}

static int pop3_logout(int sock, struct query *ctl)

/* send logout command */

{

    int ok;

#ifdef __UNUSED__

    /*

     * We used to do this in case the server marks messages deleted when seen.

     * (Yes, this has been reported, in the MercuryP/NLM server.

     * It's even legal under RFC 1939 (section 8) as a site policy.)

     * It interacted badly with UIDL, though.  Thomas Zajic wrote:

     * "Running 'fetchmail -F -v' and checking the logs, I found out

     * that fetchmail did in fact flush my mailbox properly, but sent

     * a RSET just before sending QUIT to log off.  This caused the

     * POP3 server to undo/forget about the previous DELEs, resetting

     * my mailbox to its original (ie.  unflushed) state. The

     * ~/.fetchids file did get flushed though, so the next time

     * fetchmail was run it saw all the old messages as new ones ..."

     */

     if (ctl->keep)

	gen_transact(sock, "RSET");

#endif /* __UNUSED__ */

    ok = gen_transact(sock, "QUIT");

    if (!ok)

	expunge_uids(ctl);

    return(ok);

}

static const struct method pop3 =

{

    "POP3",		/* Post Office Protocol v3 */

    "pop3",		/* port for plain and TLS POP3 */

    "pop3s",		/* port for SSL POP3 */

    FALSE,		/* this is not a tagged protocol */

    TRUE,		/* this uses a message delimiter */

    pop3_ok,		/* parse command response */

    pop3_getauth,	/* get authorization */

    pop3_getrange,	/* query range of messages */

    pop3_getsizes,	/* we can get a list of sizes */

    pop3_getpartialsizes,	/* we can get the size of 1 mail */

    pop3_is_old,	/* how do we tell a message is old? */

    pop3_fetch,		/* request given message */

    NULL,		/* no way to fetch body alone */

    NULL,		/* no message trailer */

    pop3_delete,	/* how to delete a message */

    pop3_mark_seen,	/* how to mark a message as seen */

    NULL,		/* no action at end of mailbox */

    pop3_logout,	/* log out, we're done */

    FALSE,		/* no, we can't re-poll */

};

int doPOP3 (struct query *ctl)

/* retrieve messages using POP3 */

{

#ifndef MBOX

    if (ctl->mailboxes->id) {

	fprintf(stderr,GT_("Option --folder is not supported with POP3\n"));

	return(PS_SYNTAX);

    }

#endif /* MBOX */

    return(do_protocol(ctl, &pop3));

}

#endif /* POP3_ENABLE */

/* pop3.c ends here */