* Improve code that determines the type of encryption that is used according

[alpine.git] / imap / src / c-client / pop3.c

/* ========================================================================
 * Copyright 2008-2011 Mark Crispin   
 * ========================================================================
 */

/*
 * Program:     Post Office Protocol 3 (POP3) client routines
 *
 * Author:      Mark Crispin
 *
 * Date:        6 June 1994
 * Last Edited: 8 April 2011
 *
 * Previous versions of this file were:
 *
 * Copyright 1988-2007 University of Washington
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 */


#include <ctype.h>
#include <stdio.h>
#include <time.h>
#include "c-client.h"
#include "flstring.h"
#include "netmsg.h"
\f
/* Parameters */

#define POP3TCPPORT (long) 110  /* assigned TCP contact port */
#define POP3SSLPORT (long) 995  /* assigned SSL TCP contact port */
#define IDLETIMEOUT (long) 10   /* defined in RFC 1939 */


/* POP3 I/O stream local data */
        
typedef struct pop3_local {
  NETSTREAM *netstream;         /* TCP I/O stream */
  char *response;               /* last server reply */
  char *reply;                  /* text of last server reply */
  unsigned long cached;         /* current cached message uid */
  unsigned long hdrsize;        /* current cached header size */
  FILE *txt;                    /* current cached file descriptor */
  struct {
    unsigned int capa : 1;      /* server has CAPA, definitely new */
    unsigned int expire : 1;    /* server has EXPIRE */
    unsigned int logindelay : 1;/* server has LOGIN-DELAY */
    unsigned int stls : 1;      /* server has STLS */
    unsigned int pipelining : 1;/* server has PIPELINING */
    unsigned int respcodes : 1; /* server has RESP-CODES */
    unsigned int top : 1;       /* server has TOP */
    unsigned int uidl : 1;      /* server has UIDL */
    unsigned int user : 1;      /* server has USER */
    char *implementation;       /* server implementation string */
    long delaysecs;             /* minimum time between login (neg variable) */
    long expiredays;            /* server-guaranteed minimum retention days */
                                /* supported authenticators */
    unsigned int sasl : MAXAUTHENTICATORS;
  } cap;
  unsigned int sensitive : 1;   /* sensitive data in progress */
  unsigned int loser : 1;       /* server is a loser */
  unsigned int saslcancel : 1;  /* SASL cancelled by protocol */
} POP3LOCAL;


/* Convenient access to local data */

#define LOCAL ((POP3LOCAL *) stream->local)
\f
/* Function prototypes */

DRIVER *pop3_valid (char *name);
void *pop3_parameters (long function,void *value);
void pop3_scan (MAILSTREAM *stream,char *ref,char *pat,char *contents);
void pop3_list (MAILSTREAM *stream,char *ref,char *pat);
void pop3_lsub (MAILSTREAM *stream,char *ref,char *pat);
long pop3_subscribe (MAILSTREAM *stream,char *mailbox);
long pop3_unsubscribe (MAILSTREAM *stream,char *mailbox);
long pop3_create (MAILSTREAM *stream,char *mailbox);
long pop3_delete (MAILSTREAM *stream,char *mailbox);
long pop3_rename (MAILSTREAM *stream,char *old,char *newname);
long pop3_status (MAILSTREAM *stream,char *mbx,long flags);
MAILSTREAM *pop3_open (MAILSTREAM *stream);
long pop3_capa (MAILSTREAM *stream,long flags);
long pop3_auth (MAILSTREAM *stream,NETMBX *mb,char *pwd,char *usr);
void *pop3_challenge (void *stream,unsigned long *len);
long pop3_response (void *stream,char *s,unsigned long size);
void pop3_close (MAILSTREAM *stream,long options);
void pop3_fetchfast (MAILSTREAM *stream,char *sequence,long flags);
char *pop3_header (MAILSTREAM *stream,unsigned long msgno,unsigned long *size,
                   long flags);
long pop3_text (MAILSTREAM *stream,unsigned long msgno,STRING *bs,long flags);
unsigned long pop3_cache (MAILSTREAM *stream,MESSAGECACHE *elt);
long pop3_ping (MAILSTREAM *stream);
void pop3_check (MAILSTREAM *stream);
long pop3_expunge (MAILSTREAM *stream,char *sequence,long options);
long pop3_copy (MAILSTREAM *stream,char *sequence,char *mailbox,long options);
long pop3_append (MAILSTREAM *stream,char *mailbox,append_t af,void *data);

long pop3_send_num (MAILSTREAM *stream,char *command,unsigned long n);
long pop3_send (MAILSTREAM *stream,char *command,char *args);
long pop3_reply (MAILSTREAM *stream);
long pop3_fake (MAILSTREAM *stream,char *text);
\f
/* POP3 mail routines */


/* Driver dispatch used by MAIL */

DRIVER pop3driver = {
  "pop3",                       /* driver name */
                                /* driver flags */
#ifdef INADEQUATE_MEMORY
  DR_LOWMEM |
#endif
  DR_MAIL|DR_NOFAST|DR_CRLF|DR_NOSTICKY|DR_NOINTDATE|DR_NONEWMAIL,
  (DRIVER *) NIL,               /* next driver */
  pop3_valid,                   /* mailbox is valid for us */
  pop3_parameters,              /* manipulate parameters */
  pop3_scan,                    /* scan mailboxes */
  pop3_list,                    /* find mailboxes */
  pop3_lsub,                    /* find subscribed mailboxes */
  pop3_subscribe,               /* subscribe to mailbox */
  pop3_unsubscribe,             /* unsubscribe from mailbox */
  pop3_create,                  /* create mailbox */
  pop3_delete,                  /* delete mailbox */
  pop3_rename,                  /* rename mailbox */
  pop3_status,                  /* status of mailbox */
  pop3_open,                    /* open mailbox */
  pop3_close,                   /* close mailbox */
  pop3_fetchfast,               /* fetch message "fast" attributes */
  NIL,                          /* fetch message flags */
  NIL,                          /* fetch overview */
  NIL,                          /* fetch message structure */
  pop3_header,                  /* fetch message header */
  pop3_text,                    /* fetch message text */
  NIL,                          /* fetch message */
  NIL,                          /* unique identifier */
  NIL,                          /* message number from UID */
  NIL,                          /* modify flags */
  NIL,                          /* per-message modify flags */
  NIL,                          /* search for message based on criteria */
  NIL,                          /* sort messages */
  NIL,                          /* thread messages */
  pop3_ping,                    /* ping mailbox to see if still alive */
  pop3_check,                   /* check for new messages */
  pop3_expunge,                 /* expunge deleted messages */
  pop3_copy,                    /* copy messages to another mailbox */
  pop3_append,                  /* append string message to mailbox */
  NIL                           /* garbage collect stream */
};

                                /* prototype stream */
MAILSTREAM pop3proto = {&pop3driver};

                                /* driver parameters */
static unsigned long pop3_maxlogintrials = MAXLOGINTRIALS;
static long pop3_port = 0;
static long pop3_sslport = 0;
\f
/* POP3 mail validate mailbox
 * Accepts: mailbox name
 * Returns: our driver if name is valid, NIL otherwise
 */

DRIVER *pop3_valid (char *name)
{
  NETMBX mb;
  return (mail_valid_net_parse (name,&mb) &&
          !strcmp (mb.service,pop3driver.name) && !mb.authuser[0] &&
          !compare_cstring (mb.mailbox,"INBOX")) ? &pop3driver : NIL;
}


/* News manipulate driver parameters
 * Accepts: function code
 *          function-dependent value
 * Returns: function-dependent return value
 */

void *pop3_parameters (long function,void *value)
{
  switch ((int) function) {
  case SET_MAXLOGINTRIALS:
    pop3_maxlogintrials = (unsigned long) value;
    break;
  case GET_MAXLOGINTRIALS:
    value = (void *) pop3_maxlogintrials;
    break;
  case SET_POP3PORT:
    pop3_port = (long) value;
    break;
  case GET_POP3PORT:
    value = (void *) pop3_port;
    break;
  case SET_SSLPOPPORT:
    pop3_sslport = (long) value;
    break;
  case GET_SSLPOPPORT:
    value = (void *) pop3_sslport;
    break;
  case GET_IDLETIMEOUT:
    value = (void *) IDLETIMEOUT;
    break;
  default:
    value = NIL;                /* error case */
    break;
  }
  return value;
}
\f
/* POP3 mail scan mailboxes for string
 * Accepts: mail stream
 *          reference
 *          pattern to search
 *          string to scan
 */

void pop3_scan (MAILSTREAM *stream,char *ref,char *pat,char *contents)
{
  char tmp[MAILTMPLEN];
  if ((ref && *ref) ?           /* have a reference */
      (pop3_valid (ref) && pmatch ("INBOX",pat)) :
      (mail_valid_net (pat,&pop3driver,NIL,tmp) && pmatch ("INBOX",tmp)))
    mm_log ("Scan not valid for POP3 mailboxes",ERROR);
}


/* POP3 mail find list of all mailboxes
 * Accepts: mail stream
 *          reference
 *          pattern to search
 */

void pop3_list (MAILSTREAM *stream,char *ref,char *pat)
{
  char tmp[MAILTMPLEN];
  if (ref && *ref) {            /* have a reference */
    if (pop3_valid (ref) && pmatch ("INBOX",pat)) {
      strcpy (strchr (strcpy (tmp,ref),'}')+1,"INBOX");
      mm_list (stream,NIL,tmp,LATT_NOINFERIORS);
    }
  }
  else if (mail_valid_net (pat,&pop3driver,NIL,tmp) && pmatch ("INBOX",tmp)) {
    strcpy (strchr (strcpy (tmp,pat),'}')+1,"INBOX");
    mm_list (stream,NIL,tmp,LATT_NOINFERIORS);
  }
}
\f
/* POP3 mail find list of subscribed mailboxes
 * Accepts: mail stream
 *          reference
 *          pattern to search
 */

void pop3_lsub (MAILSTREAM *stream,char *ref,char *pat)
{
  void *sdb = NIL;
  char *s,mbx[MAILTMPLEN],tmp[MAILTMPLEN];
  if (*pat == '{') {            /* if remote pattern, must be POP3 */
    if (!pop3_valid (pat)) return;
    ref = NIL;                  /* good POP3 pattern, punt reference */
  }
                                /* if remote reference, must be valid POP3 */
  if (ref && (*ref == '{') && !pop3_valid (ref)) return;
                                /* kludgy application of reference */
  if (ref && *ref) sprintf (mbx,"%s%s",ref,pat);
  else strcpy (mbx,pat);

  if ((s = sm_read (tmp,&sdb)) != NULL) do if (pop3_valid (s) && pmatch (s,mbx))
    mm_lsub (stream,NIL,s,NIL);
                                /* until no more subscriptions */
  while ((s = sm_read (tmp,&sdb)) != NULL);
}


/* POP3 mail subscribe to mailbox
 * Accepts: mail stream
 *          mailbox to add to subscription list
 * Returns: T on success, NIL on failure
 */

long pop3_subscribe (MAILSTREAM *stream,char *mailbox)
{
  return sm_subscribe (mailbox);
}


/* POP3 mail unsubscribe to mailbox
 * Accepts: mail stream
 *          mailbox to delete from subscription list
 * Returns: T on success, NIL on failure
 */

long pop3_unsubscribe (MAILSTREAM *stream,char *mailbox)
{
  return sm_unsubscribe (mailbox);
}
\f
/* POP3 mail create mailbox
 * Accepts: mail stream
 *          mailbox name to create
 * Returns: T on success, NIL on failure
 */

long pop3_create (MAILSTREAM *stream,char *mailbox)
{
  return NIL;                   /* never valid for POP3 */
}


/* POP3 mail delete mailbox
 *          mailbox name to delete
 * Returns: T on success, NIL on failure
 */

long pop3_delete (MAILSTREAM *stream,char *mailbox)
{
  return NIL;                   /* never valid for POP3 */
}


/* POP3 mail rename mailbox
 * Accepts: mail stream
 *          old mailbox name
 *          new mailbox name
 * Returns: T on success, NIL on failure
 */

long pop3_rename (MAILSTREAM *stream,char *old,char *newname)
{
  return NIL;                   /* never valid for POP3 */
}
\f
/* POP3 status
 * Accepts: mail stream
 *          mailbox name
 *          status flags
 * Returns: T on success, NIL on failure
 */

long pop3_status (MAILSTREAM *stream,char *mbx,long flags)
{
  MAILSTATUS status;
  unsigned long i;
  long ret = NIL;
  MAILSTREAM *tstream =
    (stream && LOCAL->netstream && mail_usable_network_stream (stream,mbx)) ?
      stream : mail_open (NIL,mbx,OP_SILENT);
  if (tstream) {                /* have a usable stream? */
    status.flags = flags;       /* return status values */
    status.messages = tstream->nmsgs;
    status.recent = tstream->recent;
    if (flags & SA_UNSEEN)      /* must search to get unseen messages */
      for (i = 1,status.unseen = 0; i <= tstream->nmsgs; i++)
        if (!mail_elt (tstream,i)->seen) status.unseen++;
    status.uidnext = tstream->uid_last + 1;
    status.uidvalidity = tstream->uid_validity;
                                /* pass status to main program */
    mm_status (tstream,mbx,&status);
    if (stream != tstream) mail_close (tstream);
    ret = LONGT;
  }
  return ret;                   /* success */
}
\f
/* POP3 mail open
 * Accepts: stream to open
 * Returns: stream on success, NIL on failure
 */

MAILSTREAM *pop3_open (MAILSTREAM *stream)
{
  unsigned long i,j;
  char *s,*t,tmp[MAILTMPLEN],usr[MAILTMPLEN];
  NETMBX mb;
  MESSAGECACHE *elt;
                                /* return prototype for OP_PROTOTYPE call */
  if (!stream) return &pop3proto;
  mail_valid_net_parse (stream->mailbox,&mb);
  usr[0] = '\0';                /* initially no user name */
  if (stream->local) fatal ("pop3 recycle stream");
                                /* /anonymous not supported */
  if (mb.anoflag || stream->anonymous) {
    mm_log ("Anonymous POP3 login not available",ERROR);
    return NIL;
  }
                                /* /readonly not supported either */
  if (mb.readonlyflag || stream->rdonly) {
    mm_log ("Read-only POP3 access not available",ERROR);
    return NIL;
  }
                                /* copy other switches */
  if (mb.dbgflag) stream->debug = T;
  if (mb.secflag) stream->secure = T;
  mb.trysslflag = stream->tryssl = (mb.trysslflag || stream->tryssl) ? T : NIL;
  stream->local =               /* instantiate localdata */
    (void *) memset (fs_get (sizeof (POP3LOCAL)),0,sizeof (POP3LOCAL));
  stream->sequence++;           /* bump sequence number */
  stream->perm_deleted = T;     /* deleted is only valid flag */
\f
  if ((LOCAL->netstream =       /* try to open connection */
       net_open (&mb,NIL,pop3_port ? pop3_port : POP3TCPPORT,
                 (NETDRIVER *) mail_parameters (NIL,GET_SSLDRIVER,NIL),
                 "*pop3s",pop3_sslport ? pop3_sslport : POP3SSLPORT)) &&
      pop3_reply (stream)) {
    mm_log (LOCAL->reply,NIL);  /* give greeting */
    if (!pop3_auth (stream,&mb,tmp,usr)) pop3_close (stream,NIL);
    else if (pop3_send (stream,"STAT",NIL)) {
      int silent = stream->silent;
      stream->silent = T;
      sprintf (tmp,"{%.200s:%lu/pop3",
               (long) mail_parameters (NIL,GET_TRUSTDNS,NIL) ?
               net_host (LOCAL->netstream) : mb.host,
               net_port (LOCAL->netstream));
      if (mb.tlsflag) strcat (tmp,"/tls");
      if (mb.tlssslv23) strcat (tmp,"/tls-sslv23");
      if (mb.tls1) strcat (tmp,"/tls1");
      if (mb.tls1_1) strcat (tmp,"/tls1_1");
      if (mb.tls1_2) strcat (tmp,"/tls1_2");
      if (mb.tls1_3) strcat (tmp,"/tls1_3");
      if (mb.notlsflag) strcat (tmp,"/notls");
      if (mb.sslflag) strcat (tmp,"/ssl");
      if (mb.novalidate) strcat (tmp,"/novalidate-cert");
      if ((LOCAL->loser = mb.loser) != 0) strcat (tmp,"/loser");
      if (stream->secure) strcat (tmp,"/secure");
      sprintf (tmp + strlen (tmp),"/user=\"%s\"}%s",usr,mb.mailbox);
      stream->inbox = T;        /* always INBOX */
      fs_give ((void **) &stream->mailbox);
      stream->mailbox = cpystr (tmp);
                                /* notify upper level */
      mail_exists (stream,stream->uid_last = strtoul (LOCAL->reply,NIL,10));
      mail_recent (stream,stream->nmsgs);
                                /* instantiate elt */
      for (i = 0; i < stream->nmsgs;) {
        elt = mail_elt (stream,++i);
        elt->valid = elt->recent = T;
        elt->private.uid = i;
      }
\f
                                /* trust LIST output if new server */
      if (!LOCAL->loser && LOCAL->cap.capa && pop3_send (stream,"LIST",NIL)) {
        while ((s = net_getline (LOCAL->netstream)) && (*s != '.')) {
          if ((i = strtoul (s,&t,10)) && (i <= stream->nmsgs) &&
              (j = strtoul (t,NIL,10))) mail_elt (stream,i)->rfc822_size = j;
          fs_give ((void **) &s);
        }
                                /* flush final dot */
        if (s) fs_give ((void **) &s);
        else {                  /* lost connection */
          mm_log ("POP3 connection broken while itemizing messages",ERROR);
          pop3_close (stream,NIL);
          return NIL;
        }
      }
      stream->silent = silent;  /* notify main program */
      mail_exists (stream,stream->nmsgs);
                                /* notify if empty */
      if (!(stream->nmsgs || stream->silent)) mm_log ("Mailbox is empty",WARN);
    }
    else {                      /* error in STAT */
      mm_log (LOCAL->reply,ERROR);
      pop3_close (stream,NIL);  /* too bad */
    }
  }
  else {                        /* connection failed */
    if (LOCAL->reply) mm_log (LOCAL->reply,ERROR);
    pop3_close (stream,NIL);    /* failed, clean up */
  }
  return LOCAL ? stream : NIL;  /* if stream is alive, return to caller */
}
\f
/* POP3 capabilities
 * Accepts: stream
 *          authenticator flags
 * Returns: T on success, NIL on failure
 */

long pop3_capa (MAILSTREAM *stream,long flags)
{
  unsigned long i;
  char *s,*t,*r,*args;
  if (LOCAL->cap.implementation)/* zap all old capabilities */
    fs_give ((void **) &LOCAL->cap.implementation);
  memset (&LOCAL->cap,0,sizeof (LOCAL->cap));
                                /* get server capabilities */
  if (pop3_send (stream,"CAPA",NIL)) LOCAL->cap.capa = T;
  else {
    LOCAL->cap.user = T;        /* guess worst-case old server */
    return NIL;                 /* no CAPA on this server */
  }
  while ((t = net_getline (LOCAL->netstream)) && (t[1] || (*t != '.'))) {
    if (stream->debug) mm_dlog (t);
                                /* get optional capability arguments */
    if ((args = strchr (t,' ')) != NULL) *args++ = '\0';
    if (!compare_cstring (t,"STLS")) LOCAL->cap.stls = T;
    else if (!compare_cstring (t,"PIPELINING")) LOCAL->cap.pipelining = T;
    else if (!compare_cstring (t,"RESP-CODES")) LOCAL->cap.respcodes = T;
    else if (!compare_cstring (t,"TOP")) LOCAL->cap.top = T;
    else if (!compare_cstring (t,"UIDL")) LOCAL->cap.uidl = T;
    else if (!compare_cstring (t,"USER")) LOCAL->cap.user = T;
    else if (!compare_cstring (t,"IMPLEMENTATION") && args)
      LOCAL->cap.implementation = cpystr (args);
    else if (!compare_cstring (t,"EXPIRE") && args) {
      LOCAL->cap.expire = T;    /* note that it is present */
      if ((s = strchr(args,' ')) != NULL){/* separate time from possible USER */
        *s++ = '\0';
                                /* in case they add something after USER */
        if ((strlen (s) > 4) && (s[4] == ' ')) s[4] = '\0';
      }
      LOCAL->cap.expire =       /* get expiration time */
        (!compare_cstring (args,"NEVER")) ? 65535 :
          ((s && !compare_cstring (s,"USER")) ? -atoi (args) : atoi (args));
    }
    else if (!compare_cstring (t,"LOGIN-DELAY") && args) {
      LOCAL->cap.logindelay = T;/* note that it is present */
      if ((s = strchr(args,' ')) != NULL){/* separate time from possible USER */
        *s++ = '\0';
                                /* in case they add something after USER */
        if ((strlen (s) > 4) && (s[4] == ' ')) s[4] = '\0';
      }
                                /* get delay time */
      LOCAL->cap.delaysecs = (s && !compare_cstring (s,"USER")) ?
        -atoi (args) : atoi (args);
    }
    else if (!compare_cstring (t,"SASL") && args)
      for (args = strtok_r (args," ",&r); args; args = strtok_r (NIL," ",&r))
        if ((i = mail_lookup_auth_name (args,flags)) &&
            (--i < MAXAUTHENTICATORS))
          LOCAL->cap.sasl |= (1 << i);
    fs_give ((void **) &t);
  }
  if (t) {                      /* flush end of text indicator */
    if (stream->debug) mm_dlog (t);
    fs_give ((void **) &t);
  }
  return LONGT;
}
\f
/* POP3 authenticate
 * Accepts: stream to login
 *          parsed network mailbox structure
 *          scratch buffer of length MAILTMPLEN
 *          place to return user name
 * Returns: T on success, NIL on failure
 */

long pop3_auth (MAILSTREAM *stream,NETMBX *mb,char *pwd,char *usr)
{
  unsigned long i,trial,auths = 0, authsaved;
  char *t, *app_pwd = NIL;
  AUTHENTICATOR *at, *atsaved;
  long ret = NIL;
  long flags = (stream->secure ? AU_SECURE : NIL) |
    (mb->authuser[0] ? AU_AUTHUSER : NIL);
  long capaok = pop3_capa (stream,flags);
  NETDRIVER *ssld = (NETDRIVER *) mail_parameters (NIL,GET_SSLDRIVER,NIL);
  sslstart_t stls = (sslstart_t) mail_parameters (NIL,GET_SSLSTART,NIL);
                                /* server has TLS? */
  if (stls && LOCAL->cap.stls && !mb->sslflag && !mb->notlsflag &&
      pop3_send (stream,"STLS",NIL)) {
    mb->tlsflag = T;            /* TLS OK, get into TLS at this end */
    LOCAL->netstream->dtb = ssld;
    if (!(LOCAL->netstream->stream =
          (*stls) (LOCAL->netstream->stream,mb->host,
                   SSL_MTHD(*mb) | (mb->novalidate ? NET_NOVALIDATECERT : NIL)))) {
                                /* drat, drop this connection */
      if (LOCAL->netstream) net_close (LOCAL->netstream);
      LOCAL->netstream= NIL;
      return NIL;               /* TLS negotiation failed */
    }
    pop3_capa (stream,flags);   /* get capabilities now that TLS in effect */
  }
  else if (mb->tlsflag) {       /* user specified /tls but can't do it */
    mm_log ("Unable to negotiate TLS with this server",ERROR);
    return NIL;
  }
                                /* get authenticators from capabilities */
  if (capaok) auths = LOCAL->cap.sasl;
                                /* get list of authenticators */
  else if (pop3_send (stream,"AUTH",NIL)) {
    while ((t = net_getline (LOCAL->netstream)) && (t[1] || (*t != '.'))) {
      if (stream->debug) mm_dlog (t);
      if ((i = mail_lookup_auth_name (t,flags)) && (--i < MAXAUTHENTICATORS))
        auths |= (1 << i);
      fs_give ((void **) &t);
    }
    if (t) {                    /* flush end of text indicator */
      if (stream->debug) mm_dlog (t);
      fs_give ((void **) &t);
    }
  }
                                /* disable LOGIN if PLAIN also advertised */
  if ((i = mail_lookup_auth_name ("PLAIN",NIL)) && (--i < MAXAUTHENTICATORS) &&
      (auths & (1 << i)) &&
      (i = mail_lookup_auth_name ("LOGIN",NIL)) && (--i < MAXAUTHENTICATORS))
    auths &= ~(1 << i);
\f
  if (auths) {                  /* got any authenticators? */
    if ((long) mail_parameters (NIL,GET_TRUSTDNS,NIL)) {
                                /* remote name for authentication */
      strncpy (mb->host,(long) mail_parameters (NIL,GET_SASLUSESPTRNAME,NIL) ?
               net_remotehost (LOCAL->netstream) : net_host (LOCAL->netstream),
               NETMAXHOST-1);
      mb->host[NETMAXHOST-1] = '\0';
    }
    for (t = NIL, LOCAL->saslcancel = NIL; !ret && LOCAL->netstream && auths &&
         (at = mail_lookup_auth (find_rightmost_bit (&auths)+1)); ) {
        if(mb && *mb->auth){
           if(!compare_cstring(at->name, mb->auth))
              atsaved = at;
           else{
              authsaved = auths;
              continue;
           }
        }   

      if (t) {                  /* previous authenticator failed? */
        sprintf (pwd,"Retrying using %.80s authentication after %.80s",
                 at->name,t);
        mm_log (pwd,NIL);
        fs_give ((void **) &t);
      }
      trial = 0;                /* initial trial count */
      do {
        if (t) {
          sprintf (pwd,"Retrying %s authentication after %.80s",at->name,t);
          mm_log (pwd,WARN);
          fs_give ((void **) &t);
        }
        LOCAL->saslcancel = NIL;
        if (pop3_send (stream,"AUTH",at->name)) {
                                /* hide client authentication responses */
          if (!(at->flags & AU_SECURE)) LOCAL->sensitive = T;
          if ((*at->client) (pop3_challenge,pop3_response,"pop",mb,stream,
                             &trial,usr) && LOCAL->response) {
            if (*LOCAL->response == '+') ret = LONGT;
                                /* if main program requested cancellation */
            else if (!trial) mm_log ("POP3 Authentication cancelled",ERROR);
          }
          LOCAL->sensitive=NIL; /* unhide */
        }
                                /* remember response if error and no cancel */
        if (!ret && trial) t = cpystr (LOCAL->reply);
      } while (!ret && trial && (trial < pop3_maxlogintrials) &&
               LOCAL->netstream);
    }
    if (t) {                    /* previous authenticator failed? */
      if (!LOCAL->saslcancel) { /* don't do this if a cancel */
        sprintf (pwd,"Can not authenticate to POP3 server: %.80s",t);
        mm_log (pwd,ERROR);
      }
      fs_give ((void **) &t);
    }
    if(mb && *mb->auth){
      if(!authsaved) sprintf (pwd,"Client does not support AUTH=%.80s authenticator",mb->auth);
      else if (!atsaved) sprintf (pwd,"POP server does not support AUTH=%.80s authenticator",mb->auth);
      if (!authsaved || !atsaved) mm_log (pwd,ERROR);
  }

  }
\f
  else if (stream->secure)
    mm_log ("Can't do secure authentication with this server",ERROR);
  else if (mb->authuser[0])
    mm_log ("Can't do /authuser with this server",ERROR);
  else if (!LOCAL->cap.user) mm_log ("Can't login to this server",ERROR);
  else {                        /* traditional login */
    trial = 0;                  /* initial trial count */
    do {
      pwd[0] = 0;               /* prompt user for password */
      if(app_pwd) fs_give((void **) &app_pwd);
      mm_login (mb,usr, &app_pwd,trial++);
      if(app_pwd){ 
        strncpy(pwd, app_pwd, MAILTMPLEN);
        pwd[MAILTMPLEN-1] = '\0';
      }
      if (pwd[0]) {             /* send login sequence if have password */
        if (pop3_send (stream,"USER",usr)) {
          LOCAL->sensitive = T; /* hide this command */
          if (pop3_send (stream,"PASS",pwd)) ret = LONGT;
          LOCAL->sensitive=NIL; /* unhide */
        }
        if (!ret) {             /* failure */
          mm_log (LOCAL->reply,WARN);
          if (trial == pop3_maxlogintrials)
            mm_log ("Too many login failures",ERROR);
        }
      }
                                /* user refused to give password */
      else mm_log ("Login aborted",ERROR);
    } while (!ret && pwd[0] && (trial < pop3_maxlogintrials) &&
             LOCAL->netstream);
  }
  if(app_pwd) fs_give((void **) &app_pwd);
  memset (pwd,0,MAILTMPLEN);    /* erase password */
                                /* get capabilities if logged in */
  if (ret && capaok) pop3_capa (stream,flags);
  return ret;
}
\f
/* Get challenge to authenticator in binary
 * Accepts: stream
 *          pointer to returned size
 * Returns: challenge or NIL if not challenge
 */

void *pop3_challenge (void *s,unsigned long *len)
{
  char tmp[MAILTMPLEN];
  void *ret = NIL;
  MAILSTREAM *stream = (MAILSTREAM *) s;
  if (stream && LOCAL->response &&
      (*LOCAL->response == '+') && (LOCAL->response[1] == ' ') &&
      !(ret = rfc822_base64 ((unsigned char *) LOCAL->reply,
                             strlen (LOCAL->reply),len))) {
    sprintf (tmp,"POP3 SERVER BUG (invalid challenge): %.80s",LOCAL->reply);
    mm_log (tmp,ERROR);
  }
  return ret;
}


/* Send authenticator response in BASE64
 * Accepts: MAIL stream
 *          string to send
 *          length of string
 * Returns: T if successful, else NIL
 */

long pop3_response (void *s,char *response,unsigned long size)
{
  MAILSTREAM *stream = (MAILSTREAM *) s;
  unsigned long i,j,ret;
  char *t,*u;
  if (response) {               /* make CRLFless BASE64 string */
    if (size) {
      for (t = (char *) rfc822_binary ((void *) response,size,&i),u = t,j = 0;
           j < i; j++) if (t[j] > ' ') *u++ = t[j];
      *u = '\0';                /* tie off string for mm_dlog() */
      if (stream->debug) mail_dlog (t,LOCAL->sensitive);
                                /* append CRLF */
      *u++ = '\015'; *u++ = '\012'; *u = '\0';
      ret = net_sout (LOCAL->netstream,t,u - t);
      fs_give ((void **) &t);
    }
    else ret = net_sout (LOCAL->netstream,"\015\012",2);
  }
  else {                        /* abort requested */
    ret = net_sout (LOCAL->netstream,"*\015\012",3);
    LOCAL->saslcancel = T;      /* mark protocol-requested SASL cancel */
  }
  pop3_reply (stream);          /* get response */
  return ret;
}
\f
/* POP3 mail close
 * Accepts: MAIL stream
 *          option flags
 */

void pop3_close (MAILSTREAM *stream,long options)
{
  int silent = stream->silent;
  if (LOCAL) {                  /* only if a file is open */
    if (LOCAL->netstream) {     /* close POP3 connection */
      stream->silent = T;
      if (options & CL_EXPUNGE) pop3_expunge (stream,NIL,NIL);
      stream->silent = silent;
      pop3_send (stream,"QUIT",NIL);
      mm_notify (stream,LOCAL->reply,BYE);
    }
                                /* close POP3 connection */
    if (LOCAL->netstream) net_close (LOCAL->netstream);
                                /* clean up */
    if (LOCAL->cap.implementation)
      fs_give ((void **) &LOCAL->cap.implementation);
    if (LOCAL->txt) fclose (LOCAL->txt);
    LOCAL->txt = NIL;
    if (LOCAL->response) fs_give ((void **) &LOCAL->response);
                                /* nuke the local data */
    fs_give ((void **) &stream->local);
    stream->dtb = NIL;          /* log out the DTB */
  }
}
\f
/* POP3 mail fetch fast information
 * Accepts: MAIL stream
 *          sequence
 *          option flags
 * This is ugly and slow
 */

void pop3_fetchfast (MAILSTREAM *stream,char *sequence,long flags)
{
  unsigned long i;
  MESSAGECACHE *elt;
                                /* get sequence */
  if (stream && LOCAL && ((flags & FT_UID) ?
                          mail_uid_sequence (stream,sequence) :
                          mail_sequence (stream,sequence)))
    for (i = 1; i <= stream->nmsgs; i++)
      if ((elt = mail_elt (stream,i))->sequence &&
          !(elt->day && elt->rfc822_size)) {
        ENVELOPE **env = NIL;
        ENVELOPE *e = NIL;
        if (!stream->scache) env = &elt->private.msg.env;
        else if (stream->msgno == i) env = &stream->env;
        else env = &e;
        if (!*env || !elt->rfc822_size) {
          STRING bs;
          unsigned long hs;
          char *ht = (*stream->dtb->header) (stream,i,&hs,NIL);
                                /* need to make an envelope? */
          if (!*env) rfc822_parse_msg (env,NIL,ht,hs,NIL,BADHOST,
                                       stream->dtb->flags);
                                /* need message size too, ugh */
          if (!elt->rfc822_size) {
            (*stream->dtb->text) (stream,i,&bs,FT_PEEK);
            elt->rfc822_size = hs + SIZE (&bs) - GETPOS (&bs);
          }
        }
                                /* if need date, have date in envelope? */
        if (!elt->day && *env && (*env)->date)
          mail_parse_date (elt,(*env)->date);
                                /* sigh, fill in bogus default */
        if (!elt->day) elt->day = elt->month = 1;
        mail_free_envelope (&e);
      }
}
\f
/* POP3 fetch header as text
 * Accepts: mail stream
 *          message number
 *          pointer to return size
 *          flags
 * Returns: header text
 */

char *pop3_header (MAILSTREAM *stream,unsigned long msgno,unsigned long *size,
                   long flags)
{
  unsigned long i;
  char tmp[MAILTMPLEN];
  MESSAGECACHE *elt;
  FILE *f = NIL;
  *size = 0;                    /* initially no header size */
  if ((flags & FT_UID) && !(msgno = mail_msgno (stream,msgno))) return "";
                                /* have header text already? */
  if (!(elt = mail_elt (stream,msgno))->private.msg.header.text.data) {
                                /* if have CAPA and TOP, assume good TOP */
    if (!LOCAL->loser && LOCAL->cap.top) {
      sprintf (tmp,"TOP %lu 0",mail_uid (stream,msgno));
      if (pop3_send (stream,tmp,NIL))
        f = netmsg_slurp (LOCAL->netstream,&i,
                          &elt->private.msg.header.text.size);
    }
                                /* otherwise load the cache with the message */
    else if ((elt->private.msg.header.text.size = pop3_cache (stream,elt)) != 0L)
      f = LOCAL->txt;
    if (f) {                    /* got it, make sure at start of file */
      fseek (f,(unsigned long) 0,SEEK_SET);
                                /* read header from the cache */
      fread (elt->private.msg.header.text.data = (unsigned char *)
             fs_get ((size_t) elt->private.msg.header.text.size + 1),
             (size_t) 1,(size_t) elt->private.msg.header.text.size,f);
                                /* tie off header text */
      elt->private.msg.header.text.data[elt->private.msg.header.text.size] =
        '\0';
                                /* close if not the cache */
      if (f != LOCAL->txt) fclose (f);
    }
  }
                                /* return size of text */
  if (size) *size = elt->private.msg.header.text.size;
  return elt->private.msg.header.text.data ?
    (char *) elt->private.msg.header.text.data : "";
}
\f
/* POP3 fetch body
 * Accepts: mail stream
 *          message number
 *          pointer to stringstruct to initialize
 *          flags
 * Returns: T if successful, else NIL
 */

long pop3_text (MAILSTREAM *stream,unsigned long msgno,STRING *bs,long flags)
{
  MESSAGECACHE *elt;
  INIT (bs,mail_string,(void *) "",0);
  if ((flags & FT_UID) && !(msgno = mail_msgno (stream,msgno))) return NIL;
  elt = mail_elt (stream,msgno);
  pop3_cache (stream,elt);      /* make sure cache loaded */
  if (!LOCAL->txt) return NIL;  /* error if don't have a file */
  if (!(flags & FT_PEEK)) {     /* mark seen if needed */
    elt->seen = T;
    mm_flags (stream,elt->msgno);
  }
  INIT (bs,file_string,(void *) LOCAL->txt,elt->rfc822_size);
  SETPOS (bs,LOCAL->hdrsize);   /* skip past header */
  return T;
}
\f
/* POP3 cache message
 * Accepts: mail stream
 *          message number
 * Returns: header size
 */

unsigned long pop3_cache (MAILSTREAM *stream,MESSAGECACHE *elt)
{
                                /* already cached? */
  if (LOCAL->cached != mail_uid (stream,elt->msgno)) {
                                /* no, close current file */
    if (LOCAL->txt) fclose (LOCAL->txt);
    LOCAL->txt = NIL;
    LOCAL->cached = LOCAL->hdrsize = 0;
    if (pop3_send_num (stream,"RETR",elt->msgno) &&
        (LOCAL->txt = netmsg_slurp (LOCAL->netstream,&elt->rfc822_size,
                                    &LOCAL->hdrsize)))
                                /* set as current message number */
      LOCAL->cached = mail_uid (stream,elt->msgno);
    else elt->deleted = T;
  }
  return LOCAL->hdrsize;
}
\f
/* POP3 mail ping mailbox
 * Accepts: MAIL stream
 * Returns: T if stream alive, else NIL
 */

long pop3_ping (MAILSTREAM *stream)
{
  return pop3_send (stream,"NOOP",NIL);
}


/* POP3 mail check mailbox
 * Accepts: MAIL stream
 */

void pop3_check (MAILSTREAM *stream)
{
  if (pop3_ping (stream)) mm_log ("Check completed",NIL);
}


/* POP3 mail expunge mailbox
 * Accepts: MAIL stream
 *          sequence to expunge if non-NIL
 *          expunge options
 * Returns: T if success, NIL if failure
 */

long pop3_expunge (MAILSTREAM *stream,char *sequence,long options)
{
  char tmp[MAILTMPLEN];
  MESSAGECACHE *elt;
  unsigned long i = 1,n = 0;
  long ret;
  if ((ret = sequence ? ((options & EX_UID) ?
                        mail_uid_sequence (stream,sequence) :
                        mail_sequence (stream,sequence)) :
      LONGT) != 0L) {                   /* build selected sequence if needed */
    while (i <= stream->nmsgs) {
      elt = mail_elt (stream,i);
      if (elt->deleted && (sequence ? elt->sequence : T) &&
          pop3_send_num (stream,"DELE",i)) {
                                /* expunging currently cached message? */
        if (LOCAL->cached == mail_uid (stream,i)) {
                                /* yes, close current file */
          if (LOCAL->txt) fclose (LOCAL->txt);
          LOCAL->txt = NIL;
          LOCAL->cached = LOCAL->hdrsize = 0;
        }
        mail_expunged (stream,i);
        n++;
      }
      else i++;                 /* try next message */
    }
    if (!stream->silent) {      /* only if not silent */
      if (n) {                  /* did we expunge anything? */
        sprintf (tmp,"Expunged %lu messages",n);
        mm_log (tmp,(long) NIL);
      }
      else mm_log ("No messages deleted, so no update needed",(long) NIL);
    }
  }
  return ret;
}
\f
/* POP3 mail copy message(s)
 * Accepts: MAIL stream
 *          sequence
 *          destination mailbox
 *          option flags
 * Returns: T if copy successful, else NIL
 */

long pop3_copy (MAILSTREAM *stream,char *sequence,char *mailbox,long options)
{
  mailproxycopy_t pc =
    (mailproxycopy_t) mail_parameters (stream,GET_MAILPROXYCOPY,NIL);
  if (pc) return (*pc) (stream,sequence,mailbox,options);
  mm_log ("Copy not valid for POP3",ERROR);
  return NIL;
}


/* POP3 mail append message from stringstruct
 * Accepts: MAIL stream
 *          destination mailbox
 *          append callback
 *          data for callback
 * Returns: T if append successful, else NIL
 */

long pop3_append (MAILSTREAM *stream,char *mailbox,append_t af,void *data)
{
  mm_log ("Append not valid for POP3",ERROR);
  return NIL;
}
\f
/* Internal routines */


/* Post Office Protocol 3 send command with number argument
 * Accepts: MAIL stream
 *          command
 *          number
 * Returns: T if successful, NIL if failure
 */

long pop3_send_num (MAILSTREAM *stream,char *command,unsigned long n)
{
  char tmp[MAILTMPLEN];
  sprintf (tmp,"%lu",mail_uid (stream,n));
  return pop3_send (stream,command,tmp);
}


/* Post Office Protocol 3 send command
 * Accepts: MAIL stream
 *          command
 *          command argument
 * Returns: T if successful, NIL if failure
 */

long pop3_send (MAILSTREAM *stream,char *command,char *args)
{
  long ret;
  char *s = (char *) fs_get (strlen (command) + (args ? strlen (args) + 1: 0)
                             + 3);
  mail_lock (stream);           /* lock up the stream */
  if (!LOCAL->netstream) ret = pop3_fake (stream,"POP3 connection lost");
  else {                        /* build the complete command */
    if (args) sprintf (s,"%s %s",command,args);
    else strcpy (s,command);
    if (stream->debug) mail_dlog (s,LOCAL->sensitive);
    strcat (s,"\015\012");
                                /* send the command */
    ret = net_soutr (LOCAL->netstream,s) ? pop3_reply (stream) :
      pop3_fake (stream,"POP3 connection broken in command");
  }
  fs_give ((void **) &s);
  mail_unlock (stream);         /* unlock stream */
  return ret;
}
\f
/* Post Office Protocol 3 get reply
 * Accepts: MAIL stream
 * Returns: T if success reply, NIL if error reply
 */

long pop3_reply (MAILSTREAM *stream)
{
  char *s;
                                /* flush old reply */
  if (LOCAL->response) fs_give ((void **) &LOCAL->response);
                                /* get reply */
  if (!(LOCAL->response = net_getline (LOCAL->netstream)))
    return pop3_fake (stream,"POP3 connection broken in response");
  if (stream->debug) mm_dlog (LOCAL->response);
  LOCAL->reply = (s = strchr (LOCAL->response,' ')) ? s + 1 : LOCAL->response;
                                /* return success or failure */
  return (*LOCAL->response =='+') ? T : NIL;
}


/* Post Office Protocol 3 set fake error
 * Accepts: MAIL stream
 *          error text
 * Returns: NIL, always
 */

long pop3_fake (MAILSTREAM *stream,char *text)
{
  mm_notify (stream,text,BYE);  /* send bye alert */
  if (LOCAL->netstream) net_close (LOCAL->netstream);
  LOCAL->netstream = NIL;       /* farewell, dear TCP stream */
                                /* flush any old reply */
  if (LOCAL->response) fs_give ((void **) &LOCAL->response);
  LOCAL->reply = text;          /* set up pseudo-reply string */
  return NIL;                   /* return error code */
}