source: trunk/third/cyrus-sasl/lib/server.c @ 18842

/* SASL server API implementation
 * Rob Siemborski
 * Tim Martin
 * $Id: server.c,v 1.1.1.2 2003-02-12 22:33:36 ghudson Exp $
 */
/* 
 * Copyright (c) 2001 Carnegie Mellon University.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer. 
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The name "Carnegie Mellon University" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For permission or any other legal
 *    details, please contact  
 *      Office of Technology Transfer
 *      Carnegie Mellon University
 *      5000 Forbes Avenue
 *      Pittsburgh, PA  15213-3890
 *      (412) 268-4387, fax: (412) 268-7395
 *      tech-transfer@andrew.cmu.edu
 *
 * 4. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by Computing Services
 *     at Carnegie Mellon University (http://www.cmu.edu/computing/)."
 *
 * CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
 * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
 * FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
 * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/* local functions/structs don't start with sasl
 */
#include <config.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
#ifndef macintosh
#include <sys/types.h>
#include <sys/stat.h>
#endif
#include <fcntl.h>
#include <string.h>
#include <ctype.h>

#include "sasl.h"
#include "saslint.h"
#include "saslplug.h"
#include "saslutil.h"

#ifdef sun
/* gotta define gethostname ourselves on suns */
extern int gethostname(char *, int);
#endif

#define DEFAULT_CHECKPASS_MECH "auxprop"

/* Contains functions:
 * 
 * sasl_server_init
 * sasl_server_new
 * sasl_listmech
 * sasl_server_start
 * sasl_server_step
 * sasl_checkpass
 * sasl_checkapop
 * sasl_user_exists
 * sasl_setpass
 */

/* if we've initialized the server sucessfully */
static int _sasl_server_active = 0;

/* For access by other modules */
int _is_sasl_server_active(void) { return _sasl_server_active; }

static int _sasl_checkpass(sasl_conn_t *conn, const char *service, 
                           const char *user, const char *pass);

static mech_list_t *mechlist = NULL; /* global var which holds the list */

static sasl_global_callbacks_t global_callbacks;

/* set the password for a user
 *  conn        -- SASL connection
 *  user        -- user name
 *  pass        -- plaintext password, may be NULL to remove user
 *  passlen     -- length of password, 0 = strlen(pass)
 *  oldpass     -- NULL will sometimes work
 *  oldpasslen  -- length of password, 0 = strlen(oldpass)
 *  flags       -- see flags below
 * 
 * returns:
 *  SASL_NOCHANGE  -- proper entry already exists
 *  SASL_NOMECH    -- no authdb supports password setting as configured
 *  SASL_NOVERIFY  -- user exists, but no settable password present
 *  SASL_DISABLED  -- account disabled
 *  SASL_PWLOCK    -- password locked
 *  SASL_WEAKPASS  -- password too weak for security policy
 *  SASL_NOUSERPASS -- user-supplied passwords not permitted
 *  SASL_FAIL      -- OS error
 *  SASL_BADPARAM  -- password too long
 *  SASL_OK        -- successful
 */

int sasl_setpass(sasl_conn_t *conn,
                 const char *user,
                 const char *pass, unsigned passlen,
                 const char *oldpass,
                 unsigned oldpasslen,
                 unsigned flags)
{
    int result=SASL_OK, tmpresult;
    sasl_server_conn_t *s_conn = (sasl_server_conn_t *) conn;
    sasl_server_userdb_setpass_t *setpass_cb = NULL;
    void *context = NULL;
    mechanism_t *m;
     
    if (!_sasl_server_active || !mechlist) return SASL_NOTINIT;

    /* check params */
    if (!conn) return SASL_BADPARAM;
    if (conn->type != SASL_CONN_SERVER) PARAMERROR(conn);
     
    if ((!(flags & SASL_SET_DISABLE) && passlen == 0)
        || ((flags & SASL_SET_CREATE) && (flags & SASL_SET_DISABLE)))
        PARAMERROR(conn);

    /* call userdb callback function */
    result = _sasl_getcallback(conn, SASL_CB_SERVER_USERDB_SETPASS,
                               &setpass_cb, &context);
    if(result == SASL_OK && setpass_cb) {
        tmpresult = setpass_cb(conn, context, user, pass, passlen,
                            s_conn->sparams->propctx, flags);
        if(tmpresult != SASL_OK) {
            _sasl_log(conn, SASL_LOG_ERR,
                      "setpass callback failed for %s: %z",
                      user, tmpresult);
        } else {
            _sasl_log(conn, SASL_LOG_NOTE,
                      "setpass callback succeeded for %s", user);
        }
    } else {
        result = SASL_OK;
    }

    /* now we let the mechanisms set their secrets */
    for (m = mechlist->mech_list; m; m = m->next) {
        if (!m->plug->setpass) {
            /* can't set pass for this mech */
            continue;
        }
        tmpresult = m->plug->setpass(m->plug->glob_context,
                                     ((sasl_server_conn_t *)conn)->sparams,
                                     user,
                                     pass,
                                     passlen,
                                     oldpass, oldpasslen,
                                     flags);
        if (tmpresult == SASL_OK) {
            _sasl_log(conn, SASL_LOG_NOTE,
                      "%s: set secret for %s", m->plug->mech_name, user);

            m->condition = SASL_OK; /* if we previously thought the
                                       mechanism didn't have any user secrets 
                                       we now think it does */

        } else if (tmpresult == SASL_NOCHANGE) {
            _sasl_log(conn, SASL_LOG_NOTE,
                      "%s: secret not changed for %s", m->plug->mech_name, user);
        } else {
            result = tmpresult;
            _sasl_log(conn, SASL_LOG_ERR,
                      "%s: failed to set secret for %s: %z (%m)",
                      m->plug->mech_name, user, tmpresult,
#ifndef WIN32
                      errno
#else
                      GetLastError()
#endif
                      );
        }
    }

    RETURN(conn, result);
}

/* local mechanism which disposes of server */
static void server_dispose(sasl_conn_t *pconn)
{
  sasl_server_conn_t *s_conn=  (sasl_server_conn_t *) pconn;
  context_list_t *cur, *cur_next;
  
  if (s_conn->mech
      && s_conn->mech->plug->mech_dispose) {
    s_conn->mech->plug->mech_dispose(pconn->context,
                                     s_conn->sparams->utils);
  }
  pconn->context = NULL;

  for(cur = s_conn->mech_contexts; cur; cur=cur_next) {
      cur_next = cur->next;
      if(cur->context)
          cur->mech->plug->mech_dispose(cur->context, s_conn->sparams->utils);
      sasl_FREE(cur);
  }  
  s_conn->mech_contexts = NULL;
  
  _sasl_free_utils(&s_conn->sparams->utils);

  if (s_conn->sparams->propctx)
      prop_dispose(&s_conn->sparams->propctx);

  if (s_conn->user_realm)
      sasl_FREE(s_conn->user_realm);

  if (s_conn->sparams)
      sasl_FREE(s_conn->sparams);

  _sasl_conn_dispose(pconn);
}

static int init_mechlist(void)
{
    sasl_utils_t *newutils = NULL;

    mechlist->mutex = sasl_MUTEX_ALLOC();
    if(!mechlist->mutex) return SASL_FAIL;

    /* set util functions - need to do rest */
    newutils = _sasl_alloc_utils(NULL, &global_callbacks);
    if (newutils == NULL)
        return SASL_NOMEM;

    newutils->checkpass = &sasl_checkpass;

    mechlist->utils = newutils;
    mechlist->mech_list=NULL;
    mechlist->mech_length=0;

    return SASL_OK;
}

/*
 * parameters:
 *  p - entry point
 */
int sasl_server_add_plugin(const char *plugname,
                           sasl_server_plug_init_t *p)
{
    int plugcount;
    sasl_server_plug_t *pluglist;
    mechanism_t *mech;
    sasl_server_plug_init_t *entry_point;
    int result;
    int version;
    int lupe;

    if(!plugname || !p) return SASL_BADPARAM;

    entry_point = (sasl_server_plug_init_t *)p;

    /* call into the shared library asking for information about it */
    /* version is filled in with the version of the plugin */
    result = entry_point(mechlist->utils, SASL_SERVER_PLUG_VERSION, &version,
                         &pluglist, &plugcount);

    if ((result != SASL_OK) && (result != SASL_NOUSER)) {
        _sasl_log(NULL, SASL_LOG_DEBUG,
                  "server add_plugin entry_point error %z\n", result);
        return result;
    }

    /* Make sure plugin is using the same SASL version as us */
    if (version != SASL_SERVER_PLUG_VERSION)
    {
        _sasl_log(NULL, SASL_LOG_ERR,
                  "version mismatch on plugin");
        return SASL_BADVERS;
    }

    for (lupe=0;lupe < plugcount ;lupe++)
    {
        mech = sasl_ALLOC(sizeof(mechanism_t));
        if (! mech) return SASL_NOMEM;

        mech->plug=pluglist++;
        if(_sasl_strdup(plugname, &mech->plugname, NULL) != SASL_OK) {
            sasl_FREE(mech);
            return SASL_NOMEM;
        }
        mech->version = version;

        /* wheather this mech actually has any users in it's db */
        mech->condition = result; /* SASL_OK or SASL_NOUSER */

        mech->next = mechlist->mech_list;
        mechlist->mech_list = mech;
        mechlist->mech_length++;
    }

    return SASL_OK;
}

static void server_done(void) {
  mechanism_t *m;
  mechanism_t *prevm;

  if (mechlist != NULL)
  {
      m=mechlist->mech_list; /* m point to beginning of the list */

      while (m!=NULL)
      {
          prevm=m;
          m=m->next;
    
          if (prevm->plug->mech_free) {
              prevm->plug->mech_free(prevm->plug->glob_context,
                                     mechlist->utils);
          }

          sasl_FREE(prevm->plugname);             
          sasl_FREE(prevm);    
      }
      _sasl_free_utils(&mechlist->utils);
      sasl_MUTEX_FREE(mechlist->mutex);
      sasl_FREE(mechlist);
      mechlist = NULL;
  }

  /* Free the auxprop plugins */
  _sasl_auxprop_free();

  global_callbacks.callbacks = NULL;
  global_callbacks.appname = NULL;

  /* no longer active. fail on listmech's etc. */
  _sasl_server_active = 0;
}

static int
server_idle(sasl_conn_t *conn)
{
  mechanism_t *m;
  if (! mechlist)
    return 0;

  for (m = mechlist->mech_list;
       m!=NULL;
       m = m->next)
    if (m->plug->idle
        &&  m->plug->idle(m->plug->glob_context,
                          conn,
                          conn ? ((sasl_server_conn_t *)conn)->sparams : NULL))
      return 1;
  return 0;
}

static int load_config(const sasl_callback_t *verifyfile_cb)
{
  int result;
  const char *path_to_config=NULL;
  char *c;
  char *config_filename=NULL;
  int len;
  const sasl_callback_t *getpath_cb=NULL;

  /* get the path to the plugins; for now the config file will reside there */
  getpath_cb=_sasl_find_getpath_callback( global_callbacks.callbacks );
  if (getpath_cb==NULL) return SASL_BADPARAM;

  /* getpath_cb->proc MUST be a sasl_getpath_t; if only c had a type
     system */
  result = ((sasl_getpath_t *)(getpath_cb->proc))(getpath_cb->context,
                                                  &path_to_config);
  if (result!=SASL_OK) goto done;
  if (path_to_config == NULL) path_to_config = "";

  if ((c = strchr(path_to_config, PATHS_DELIMITER))) {
      *c = '\0';
  }

  /* length = length of path + '/' + length of appname + ".conf" + 1
     for '\0' */
  len = strlen(path_to_config)+2+ strlen(global_callbacks.appname)+5+1;

  if (len > PATH_MAX ) {
      result = SASL_FAIL;
      goto done;
  }

  /* construct the filename for the config file */
  config_filename = sasl_ALLOC(len);
  if (! config_filename) {
      result = SASL_NOMEM;
      goto done;
  }

  snprintf(config_filename, len, "%s/%s.conf", path_to_config, 
           global_callbacks.appname);

  /* Ask the application if it's safe to use this file */
  result = ((sasl_verifyfile_t *)(verifyfile_cb->proc))(verifyfile_cb->context,
                                        config_filename, SASL_VRFY_CONF);

  /* returns continue if this file is to be skipped */
  
  /* returns SASL_CONTINUE if doesn't exist
   * if doesn't exist we can continue using default behavior
   */
  if (result==SASL_OK)
    result=sasl_config_init(config_filename);

 done:
  if (config_filename) sasl_FREE(config_filename);

  return result;
}

/*
 * Verify that all the callbacks are valid
 */
static int verify_server_callbacks(const sasl_callback_t *callbacks)
{
    if (callbacks == NULL) return SASL_OK;

    while (callbacks->id != SASL_CB_LIST_END) {
        if (callbacks->proc==NULL) return SASL_FAIL;

        callbacks++;
    }

    return SASL_OK;
}

static char *grab_field(char *line, char **eofield)
{
    int d = 0;
    char *field;

    while (isspace((int) *line)) line++;

    /* find end of field */
    while (line[d] && !isspace(((int) line[d]))) d++;
    field = sasl_ALLOC(d + 1);
    if (!field) { return NULL; }
    memcpy(field, line, d);
    field[d] = '\0';
    *eofield = line + d;
    
    return field;
}

struct secflag_map_s {
    char *name;
    int value;
};

struct secflag_map_s secflag_map[] = {
    { "noplaintext", SASL_SEC_NOPLAINTEXT },
    { "noactive", SASL_SEC_NOACTIVE },
    { "nodictionary", SASL_SEC_NODICTIONARY },
    { "forward_secrecy", SASL_SEC_FORWARD_SECRECY },
    { "noanonymous", SASL_SEC_NOANONYMOUS },
    { "pass_credentials", SASL_SEC_PASS_CREDENTIALS },
    { "mutual_auth", SASL_SEC_MUTUAL_AUTH },
    { NULL, 0x0 }
};

static int parse_mechlist_file(const char *mechlistfile)
{
    FILE *f;
    char buf[1024];
    char *t, *ptr;
    int r = 0;

    f = fopen(mechlistfile, "r");
    if (!f) return SASL_FAIL;

    r = SASL_OK;
    while (fgets(buf, sizeof(buf), f) != NULL) {
        mechanism_t *n = sasl_ALLOC(sizeof(mechanism_t));
        sasl_server_plug_t *nplug;

        if (n == NULL) { r = SASL_NOMEM; break; }
        n->version = SASL_SERVER_PLUG_VERSION;
        n->condition = SASL_CONTINUE;
        nplug = sasl_ALLOC(sizeof(sasl_server_plug_t));
        if (nplug == NULL) { r = SASL_NOMEM; break; }
        memset(nplug, 0, sizeof(sasl_server_plug_t));

        /* each line is:
           plugin-file WS mech_name WS max_ssf *(WS security_flag) RET
        */
        
        /* grab file */
        n->f = grab_field(buf, &ptr);

        /* grab mech_name */
        nplug->mech_name = grab_field(ptr, &ptr);

        /* grab max_ssf */
        nplug->max_ssf = strtol(ptr, &ptr, 10);

        /* grab security flags */
        while (*ptr != '\n') {
            struct secflag_map_s *map;

            /* read security flag */
            t = grab_field(ptr, &ptr);
            map = secflag_map;
            while (map->name) {
                if (!strcasecmp(t, map->name)) {
                    nplug->security_flags |= map->value;
                    break;
                }
                map++;
            }
            if (!map->name) {
                _sasl_log(NULL, SASL_LOG_ERR,
                          "%s: couldn't identify flag '%s'",
                          nplug->mech_name, t);
            }
            free(t);
        }

        /* insert mechanism into mechlist */
        n->plug = nplug;
        n->next = mechlist->mech_list;
        mechlist->mech_list = n;
        mechlist->mech_length++;
    }

    fclose(f);
    return r;
}

/* initialize server drivers, done once per process
 *  callbacks      -- callbacks for all server connections; must include
 *                    getopt callback
 *  appname        -- name of calling application (for lower level logging)
 * results:
 *  state          -- server state
 * returns:
 *  SASL_OK        -- success
 *  SASL_BADPARAM  -- error in config file
 *  SASL_NOMEM     -- memory failure
 *  SASL_BADVERS   -- Mechanism version mismatch
 */

int sasl_server_init(const sasl_callback_t *callbacks,
                     const char *appname)
{
    int ret;
    const sasl_callback_t *vf;
    const char *pluginfile = NULL;
#ifdef PIC
    sasl_getopt_t *getopt;
    void *context;
#endif

    const add_plugin_list_t ep_list[] = {
        { "sasl_server_plug_init", (add_plugin_t *)sasl_server_add_plugin },
        { "sasl_auxprop_plug_init", (add_plugin_t *)sasl_auxprop_add_plugin },
        { "sasl_canonuser_init", (add_plugin_t *)sasl_canonuser_add_plugin },
        { NULL, NULL }
    };

    /* we require the appname to be non-null */
    if (appname==NULL) return SASL_BADPARAM;

    ret = _sasl_common_init();
    if (ret != SASL_OK)
        return ret;
 
    _sasl_server_cleanup_hook = &server_done;

    /* verify that the callbacks look ok */
    ret = verify_server_callbacks(callbacks);
    if (ret != SASL_OK) return ret;

    global_callbacks.callbacks = callbacks;
    global_callbacks.appname = appname;

    /* allocate mechlist and set it to empty */
    mechlist = sasl_ALLOC(sizeof(mech_list_t));
    if (mechlist == NULL) return SASL_NOMEM;

    ret = init_mechlist();
    if (ret != SASL_OK) return ret;

    vf = _sasl_find_verifyfile_callback(callbacks);

    /* load config file if applicable */
    ret = load_config(vf);
    if ((ret != SASL_OK) && (ret != SASL_CONTINUE)) {
        return ret;
    }

    /* load internal plugins */
    sasl_server_add_plugin("EXTERNAL", &external_server_plug_init);

#ifdef PIC
    /* delayed loading of plugins? (DSO only, as it doesn't
     * make much [any] sense to delay in the static library case) */
    if (_sasl_getcallback(NULL, SASL_CB_GETOPT, &getopt, &context) 
           == SASL_OK) {
        /* No sasl_conn_t was given to getcallback, so we provide the
         * global callbacks structure */
        ret = getopt(&global_callbacks, NULL, "plugin_list", &pluginfile, NULL);
    }
#endif
    
    if (pluginfile != NULL) {
        /* this file should contain a list of plugins available.
           we'll load on demand. */

        /* Ask the application if it's safe to use this file */
        ret = ((sasl_verifyfile_t *)(vf->proc))(vf->context,
                                                pluginfile,
                                                SASL_VRFY_CONF);
        if (ret != SASL_OK) {
            _sasl_log(NULL, SASL_LOG_ERR,
                      "unable to load plugin list %s: %z", pluginfile, ret);
        }
        
        if (ret == SASL_OK) {
            ret = parse_mechlist_file(pluginfile);
        }
    } else {
        /* load all plugins now */
        ret = _sasl_load_plugins(ep_list,
                                 _sasl_find_getpath_callback(callbacks),
                                 _sasl_find_verifyfile_callback(callbacks));
    }

    if (ret == SASL_OK) {
        /* _sasl_server_active shows if we're active or not. 
           server_done() sets it back to 0 */
        _sasl_server_active = 1;
        _sasl_server_idle_hook = &server_idle;

        ret = _sasl_build_mechlist();
    }

    return ret;
}

/*
 * Once we have the users plaintext password we 
 * may want to transition them. That is put entries
 * for them in the passwd database for other
 * stronger mechanism
 *
 * for example PLAIN -> CRAM-MD5
 */
static int
_sasl_transition(sasl_conn_t * conn,
                 const char * pass,
                 unsigned passlen)
{
    const char *dotrans = "n";
    sasl_getopt_t *getopt;
    int result = SASL_OK;
    void *context;

    if (! conn)
        return SASL_BADPARAM;

    if (! conn->oparams.authid)
        PARAMERROR(conn);

    /* check if this is enabled: default to false */
    if (_sasl_getcallback(conn, SASL_CB_GETOPT, &getopt, &context) == SASL_OK)
    {
        getopt(context, NULL, "auto_transition", &dotrans, NULL);
        if (dotrans == NULL) dotrans = "n";
    }

    if (*dotrans == '1' || *dotrans == 'y' ||
        (*dotrans == 'o' && dotrans[1] == 'n') || *dotrans == 't') {
        /* ok, it's on! */
        result = sasl_setpass(conn,
                              conn->oparams.authid,
                              pass,
                              passlen,
                              NULL, 0, 0);
    }

    RETURN(conn,result);
}


/* create context for a single SASL connection
 *  service        -- registered name of the service using SASL (e.g. "imap")
 *  serverFQDN     -- Fully qualified domain name of server.  NULL means use
 *                    gethostname() or equivalent.
 *                    Useful for multi-homed servers.
 *  user_realm     -- permits multiple user realms on server, NULL = default
 *  iplocalport    -- server IPv4/IPv6 domain literal string with port
 *                    (if NULL, then mechanisms requiring IPaddr are disabled)
 *  ipremoteport   -- client IPv4/IPv6 domain literal string with port
 *                    (if NULL, then mechanisms requiring IPaddr are disabled)
 *  callbacks      -- callbacks (e.g., authorization, lang, new getopt context)
 *  flags          -- usage flags (see above)
 * returns:
 *  pconn          -- new connection context
 *
 * returns:
 *  SASL_OK        -- success
 *  SASL_NOMEM     -- not enough memory
 */

int sasl_server_new(const char *service,
                    const char *serverFQDN,
                    const char *user_realm,
                    const char *iplocalport,
                    const char *ipremoteport,
                    const sasl_callback_t *callbacks,
                    unsigned flags,
                    sasl_conn_t **pconn)
{
  int result;
  sasl_server_conn_t *serverconn;
  sasl_utils_t *utils;

  if (_sasl_server_active==0) return SASL_NOTINIT;
  if (! pconn) return SASL_FAIL;
  if (! service) return SASL_FAIL;

  *pconn=sasl_ALLOC(sizeof(sasl_server_conn_t));
  if (*pconn==NULL) return SASL_NOMEM;

  memset(*pconn, 0, sizeof(sasl_server_conn_t));

  serverconn = (sasl_server_conn_t *)*pconn;

  /* make sparams */
  serverconn->sparams=sasl_ALLOC(sizeof(sasl_server_params_t));
  if (serverconn->sparams==NULL)
      MEMERROR(*pconn);

  memset(serverconn->sparams, 0, sizeof(sasl_server_params_t));

  (*pconn)->destroy_conn = &server_dispose;
  result = _sasl_conn_init(*pconn, service, flags, SASL_CONN_SERVER,
                           &server_idle, serverFQDN,
                           iplocalport, ipremoteport,
                           callbacks, &global_callbacks);
  if (result != SASL_OK)
      goto done_error;


  /* set util functions - need to do rest */
  utils=_sasl_alloc_utils(*pconn, &global_callbacks);
  if (!utils) {
      result = SASL_NOMEM;
      goto done_error;
  }
  
  utils->checkpass = &sasl_checkpass;

  /* Setup the propctx -> We'll assume the default size */
  serverconn->sparams->propctx=prop_new(0);
  if(!serverconn->sparams->propctx) {
      result = SASL_NOMEM;
      goto done_error;
  }

  serverconn->sparams->service = (*pconn)->service;
  serverconn->sparams->servicelen = strlen((*pconn)->service);

  serverconn->sparams->appname = global_callbacks.appname;
  serverconn->sparams->applen = strlen(global_callbacks.appname);

  serverconn->sparams->serverFQDN = (*pconn)->serverFQDN;
  serverconn->sparams->slen = strlen((*pconn)->serverFQDN);

  if (user_realm) {
      result = _sasl_strdup(user_realm, &serverconn->user_realm, NULL);
      serverconn->sparams->urlen = strlen(user_realm);
      serverconn->sparams->user_realm = serverconn->user_realm;
  } else {
      serverconn->user_realm = NULL;
      /* the sparams is already zeroed */
  }

  serverconn->sparams->utils = utils;
  serverconn->sparams->transition = &_sasl_transition;
  serverconn->sparams->canon_user = &_sasl_canon_user;
  serverconn->sparams->props = serverconn->base.props;
  serverconn->sparams->flags = flags;

  if(result == SASL_OK) return SASL_OK;

 done_error:
  _sasl_conn_dispose(*pconn);
  sasl_FREE(*pconn);
  *pconn = NULL;
  return result;
}

/*
 * The rule is:
 * IF mech strength + external strength < min ssf THEN FAIL
 * We also have to look at the security properties and make sure
 * that this mechanism has everything we want
 */
static int mech_permitted(sasl_conn_t *conn,
                          mechanism_t *mech)
{
    sasl_server_conn_t *s_conn = (sasl_server_conn_t *)conn;
    const sasl_server_plug_t *plug;
    int myflags;
    context_list_t *cur;
    sasl_getopt_t *getopt;
    void *context;
    sasl_ssf_t minssf = 0;

    if(!conn) return 0;

    if(! mech || ! mech->plug) {
        PARAMERROR(conn);
        return 0;
    }
    
    plug = mech->plug;

    /* get the list of allowed mechanisms (default = all) */
    if (_sasl_getcallback(conn, SASL_CB_GETOPT, &getopt, &context)
            == SASL_OK) {
        const char *mlist;

        getopt(context, NULL, "mech_list", &mlist, NULL);

        /* if we have a list, check the plugin against it */
        if (mlist) {
            const char *cp;

            while (*mlist) {
                for (cp = mlist; *cp && !isspace((int) *cp); cp++);
                if (((size_t) (cp - mlist) == strlen(plug->mech_name)) &&
                    !strncasecmp(mlist, plug->mech_name,
                                 strlen(plug->mech_name))) {
                    break;
                }
                mlist = cp;
                while (*mlist && isspace((int) *mlist)) mlist++;
            }

            if (!*mlist) return 0;  /* reached EOS -> not in our list */
        }
    }

    /* setup parameters for the call to mech_avail */
    s_conn->sparams->serverFQDN=conn->serverFQDN;
    s_conn->sparams->service=conn->service;
    s_conn->sparams->user_realm=s_conn->user_realm;
    s_conn->sparams->props=conn->props;
    s_conn->sparams->external_ssf=conn->external.ssf;

    /* Check if we have banished this one already */
    for(cur = s_conn->mech_contexts; cur; cur=cur->next) {
        if(cur->mech == mech) {
            /* If it's not mech_avail'd, then stop now */
            if(!cur->context) return 0;
            break;
        }
    }
    
    if (!strcasecmp(plug->mech_name, "EXTERNAL")) {
        /* Special case for the external mechanism */
        if (conn->props.min_ssf > conn->external.ssf
            || ! conn->external.auth_id) {
            sasl_seterror(conn, SASL_NOLOG,
                          "External SSF not good enough");
            return 0;
        }
    } else {    
        if (conn->props.min_ssf < conn->external.ssf) {
            minssf = 0;
        } else {
            minssf = conn->props.min_ssf - conn->external.ssf;
        }

        /* Generic mechanism */
        if (plug->max_ssf < minssf) {
            sasl_seterror(conn, SASL_NOLOG,
                          "mech %s is too weak", plug->mech_name);
            return 0; /* too weak */
        }
        
    }

    context = NULL;
    if(plug->mech_avail
       && plug->mech_avail(plug->glob_context,
                           s_conn->sparams, (void **)&context) != SASL_OK ) {
        /* Mark this mech as no good for this connection */
        cur = sasl_ALLOC(sizeof(context_list_t));
        if(!cur) {
            MEMERROR(conn);
            return 0;
        }
        cur->context = NULL;
        cur->mech = mech;
        cur->next = s_conn->mech_contexts;
        s_conn->mech_contexts = cur;

        /* Error should be set by mech_avail call */
        return 0;
    } else if(context) {
        /* Save this context */
        cur = sasl_ALLOC(sizeof(context_list_t));
        if(!cur) {
            MEMERROR(conn);
            return 0;
        }
        cur->context = context;
        cur->mech = mech;
        cur->next = s_conn->mech_contexts;
        s_conn->mech_contexts = cur;
    }
    
    /* Generic mechanism */
    if (plug->max_ssf < minssf) {
        sasl_seterror(conn, SASL_NOLOG, "too weak");
        return 0; /* too weak */
    }

    /* if there are no users in the secrets database we can't use this 
       mechanism */
    if (mech->condition == SASL_NOUSER) {
        sasl_seterror(conn, 0, "no users in secrets db");
        return 0;
    }

    /* Can it meet our features? */
    if ((conn->flags & SASL_NEED_PROXY) &&
        !(plug->features & SASL_FEAT_ALLOWS_PROXY)) {
        return 0;
    }
    
    /* security properties---if there are any flags that differ and are
       in what the connection are requesting, then fail */
    
    /* special case plaintext */
    myflags = conn->props.security_flags;

    /* if there's an external layer this is no longer plaintext */
    if ((conn->props.min_ssf <= conn->external.ssf) && 
        (conn->external.ssf > 1)) {
        myflags &= ~SASL_SEC_NOPLAINTEXT;
    }

    /* do we want to special case SASL_SEC_PASS_CREDENTIALS? nah.. */
    if (((myflags ^ plug->security_flags) & myflags) != 0) {
        sasl_seterror(conn, SASL_NOLOG,
                      "security flags do not match required");
        return 0;
    }

    /* Check Features */
    if(plug->features & SASL_FEAT_GETSECRET) {
        /* We no longer support sasl_server_{get,put}secret */
        sasl_seterror(conn, 0,
                      "mech %s requires unprovided secret facility",
                      plug->mech_name);
        return 0;
    }

    return 1;
}

/*
 * make the authorization 
 *
 */

static int do_authorization(sasl_server_conn_t *s_conn)
{
    int ret;
    sasl_authorize_t *authproc;
    void *auth_context;
    
    /* now let's see if authname is allowed to proxy for username! */
    
    /* check the proxy callback */
    if (_sasl_getcallback(&s_conn->base, SASL_CB_PROXY_POLICY,
                          &authproc, &auth_context) != SASL_OK) {
        INTERROR(&s_conn->base, SASL_NOAUTHZ);
    }

    ret = authproc(&(s_conn->base), auth_context,
                   s_conn->base.oparams.user, s_conn->base.oparams.ulen,
                   s_conn->base.oparams.authid, s_conn->base.oparams.alen,
                   s_conn->user_realm,
                   (s_conn->user_realm ? strlen(s_conn->user_realm) : 0),
                   s_conn->sparams->propctx);

    RETURN(&s_conn->base, ret);
}


/* start a mechanism exchange within a connection context
 *  mech           -- the mechanism name client requested
 *  clientin       -- client initial response (NUL terminated), NULL if empty
 *  clientinlen    -- length of initial response
 *  serverout      -- initial server challenge, NULL if done 
 *                    (library handles freeing this string)
 *  serveroutlen   -- length of initial server challenge
 * output:
 *  pconn          -- the connection negotiation state on success
 *
 * Same returns as sasl_server_step() or
 * SASL_NOMECH if mechanism not available.
 */
int sasl_server_start(sasl_conn_t *conn,
                      const char *mech,
                      const char *clientin,
                      unsigned clientinlen,
                      const char **serverout,
                      unsigned *serveroutlen)
{
    sasl_server_conn_t *s_conn=(sasl_server_conn_t *) conn;
    int result;
    context_list_t *cur, **prev;
    mechanism_t *m;

    if (_sasl_server_active==0) return SASL_NOTINIT;

    /* make sure mech is valid mechanism
       if not return appropriate error */
    m=mechlist->mech_list;

    /* check parameters */
    if(!conn) return SASL_BADPARAM;
    
    if (!mech || ((clientin==NULL) && (clientinlen>0)))
        PARAMERROR(conn);

    if(serverout) *serverout = NULL;
    if(serveroutlen) *serveroutlen = 0;

    while (m!=NULL)
    {
        if ( strcasecmp(mech,m->plug->mech_name)==0)
        {
            break;
        }
        m=m->next;
    }
  
    if (m==NULL) {
        sasl_seterror(conn, 0, "Couldn't find mech %s", mech);
        result = SASL_NOMECH;
        goto done;
    }

    /* Make sure that we're willing to use this mech */
    if (! mech_permitted(conn, m)) {
        result = SASL_NOMECH;
        goto done;
    }

    if (m->condition == SASL_CONTINUE) {
        sasl_server_plug_init_t *entry_point;
        void *library = NULL;
        sasl_server_plug_t *pluglist;
        int version, plugcount;
        int l = 0;

        /* need to load this plugin */
        result = _sasl_get_plugin(m->f,
                    _sasl_find_verifyfile_callback(global_callbacks.callbacks),
                                  &library);

        if (result == SASL_OK) {
            result = _sasl_locate_entry(library, "sasl_server_plug_init",
                                        (void **)&entry_point);
        }

        if (result == SASL_OK) {
            result = entry_point(mechlist->utils, SASL_SERVER_PLUG_VERSION,
                                 &version, &pluglist, &plugcount);
        }

        if (result == SASL_OK) {
            /* find the correct mechanism in this plugin */
            for (l = 0; l < plugcount; l++) {
                if (!strcasecmp(pluglist[l].mech_name, 
                                m->plug->mech_name)) break;
            }
            if (l == plugcount) {
                result = SASL_NOMECH;
            }
        }
        if (result == SASL_OK) {
            /* check that the parameters are the same */
            if ((pluglist[l].max_ssf != m->plug->max_ssf) ||
                (pluglist[l].security_flags != m->plug->security_flags)) {
                _sasl_log(conn, SASL_LOG_ERR, 
                          "%s: security parameters don't match mechlist file",
                          pluglist[l].mech_name);
                result = SASL_NOMECH;
            }
        }
        if (result == SASL_OK) {
            /* copy mechlist over */
            sasl_FREE((sasl_server_plug_t *) m->plug);
            m->plug = &pluglist[l];
            m->condition = SASL_OK;
        }

        if (result != SASL_OK) {
            /* The library will eventually be freed, don't sweat it */
            RETURN(conn, result);
        }
    }

    /* We used to setup sparams HERE, but now it's done
       inside of mech_permitted (which is called above) */
    prev = &s_conn->mech_contexts;
    for(cur = *prev; cur; prev=&cur->next,cur=cur->next) {
        if(cur->mech == m) {
            if(!cur->context) {
                sasl_seterror(conn, 0,
                              "Got past mech_permitted with a disallowed mech!");
                return SASL_NOMECH;
            }
            /* If we find it, we need to pull cur out of the
               list so it won't be freed later! */
            (*prev)->next = cur->next;
            conn->context = cur->context;
            sasl_FREE(cur);
        }
    }

    s_conn->mech = m;
    
    if(!conn->context) {
        /* Note that we don't hand over a new challenge */
        result = s_conn->mech->plug->mech_new(s_conn->mech->plug->glob_context,
                                              s_conn->sparams,
                                              NULL,
                                              0,
                                              &(conn->context));
    } else {
        /* the work was already done by mech_avail! */
        result = SASL_OK;
    }
    
    if (result == SASL_OK) {
         if(clientin) {
            if(s_conn->mech->plug->features & SASL_FEAT_SERVER_FIRST) {
                /* Remote sent first, but mechanism does not support it.
                 * RFC 2222 says we fail at this point. */
                sasl_seterror(conn, 0,
                              "Remote sent first but mech does not allow it.");
                result = SASL_BADPROT;
            } else {
                /* Mech wants client-first, so let them have it */
                result = sasl_server_step(conn,
                                          clientin, clientinlen,
                                          serverout, serveroutlen);
            }
        } else {
            if(s_conn->mech->plug->features & SASL_FEAT_WANT_CLIENT_FIRST) {
                /* Mech wants client first anyway, so we should do that */
                *serverout = "";
                *serveroutlen = 0;
                result = SASL_CONTINUE;
            } else {
                /* Mech wants server-first, so let them have it */
                result = sasl_server_step(conn,
                                          clientin, clientinlen,
                                          serverout, serveroutlen);
            }
        }
    }

 done:
    if(   result != SASL_OK
       && result != SASL_CONTINUE
       && result != SASL_INTERACT) {
        if(conn->context) {
            s_conn->mech->plug->mech_dispose(conn->context,
                                             s_conn->sparams->utils);
            conn->context = NULL;
        }
    }
    
    RETURN(conn,result);
}


/* perform one step of the SASL exchange
 *  inputlen & input -- client data
 *                      NULL on first step if no optional client step
 *  outputlen & output -- set to the server data to transmit
 *                        to the client in the next step
 *                        (library handles freeing this)
 *
 * returns:
 *  SASL_OK        -- exchange is complete.
 *  SASL_CONTINUE  -- indicates another step is necessary.
 *  SASL_TRANS     -- entry for user exists, but not for mechanism
 *                    and transition is possible
 *  SASL_BADPARAM  -- service name needed
 *  SASL_BADPROT   -- invalid input from client
 *  ...
 */

int sasl_server_step(sasl_conn_t *conn,
                     const char *clientin,
                     unsigned clientinlen,
                     const char **serverout,
                     unsigned *serveroutlen)
{
    int ret;
    sasl_server_conn_t *s_conn = (sasl_server_conn_t *) conn;  /* cast */

    /* check parameters */
    if (_sasl_server_active==0) return SASL_NOTINIT;
    if (!conn) return SASL_BADPARAM;
    if ((clientin==NULL) && (clientinlen>0))
        PARAMERROR(conn);

    /* If we've already done the last send, return! */
    if(s_conn->sent_last == 1) {
        return SASL_OK;
    }

    /* Don't do another step if the plugin told us that we're done */
    if (conn->oparams.doneflag) {
        _sasl_log(conn, SASL_LOG_ERR, "attempting server step after doneflag");
        return SASL_FAIL;
    }

    if(serverout) *serverout = NULL;
    if(serveroutlen) *serveroutlen = 0;

    ret = s_conn->mech->plug->mech_step(conn->context,
                                        s_conn->sparams,
                                        clientin,
                                        clientinlen,
                                        serverout,
                                        serveroutlen,
                                        &conn->oparams);

    if (ret == SASL_OK) {
        ret = do_authorization(s_conn);
    }

    if (ret == SASL_OK) {
        /* if we're done, we need to watch out for the following:
         * 1. the mech does server-send-last
         * 2. the protocol does not
         *
         * in this case, return SASL_CONTINUE and remember we are done.
         */
        if(*serverout && !(conn->flags & SASL_SUCCESS_DATA)) {
            s_conn->sent_last = 1;
            ret = SASL_CONTINUE;
        }
        if(!conn->oparams.maxoutbuf) {
            conn->oparams.maxoutbuf = conn->props.maxbufsize;
        }

        if(conn->oparams.user == NULL || conn->oparams.authid == NULL) {
            sasl_seterror(conn, 0,
                          "mech did not call canon_user for both authzid " \
                          "and authid");
            ret = SASL_BADPROT;
        }       
    }
    
    if(   ret != SASL_OK
       && ret != SASL_CONTINUE
       && ret != SASL_INTERACT) {
        if(conn->context) {
            s_conn->mech->plug->mech_dispose(conn->context,
                                             s_conn->sparams->utils);
            conn->context = NULL;
        }
    }

    RETURN(conn, ret);
}

/* returns the length of all the mechanisms
 * added up 
 */

static unsigned mech_names_len()
{
  mechanism_t *listptr;
  unsigned result = 0;

  for (listptr = mechlist->mech_list;
       listptr;
       listptr = listptr->next)
    result += strlen(listptr->plug->mech_name);

  return result;
}

/* This returns a list of mechanisms in a NUL-terminated string
 *
 * The default behavior is to seperate with spaces if sep==NULL
 */
int _sasl_server_listmech(sasl_conn_t *conn,
                          const char *user __attribute__((unused)),
                          const char *prefix,
                          const char *sep,
                          const char *suffix,
                          const char **result,
                          unsigned *plen,
                          int *pcount)
{
  int lup;
  mechanism_t *listptr;
  int ret;
  int resultlen;
  int flag;
  const char *mysep;

  /* if there hasn't been a sasl_sever_init() fail */
  if (_sasl_server_active==0) return SASL_NOTINIT;
  if (!conn) return SASL_BADPARAM;
  if (conn->type != SASL_CONN_SERVER) PARAMERROR(conn);
  
  if (! result)
      PARAMERROR(conn);

  if (plen != NULL)
      *plen = 0;
  if (pcount != NULL)
      *pcount = 0;

  if (sep) {
      mysep = sep;
  } else {
      mysep = " ";
  }

  if (! mechlist || mechlist->mech_length <= 0)
      INTERROR(conn, SASL_NOMECH);

  resultlen = (prefix ? strlen(prefix) : 0)
            + (strlen(mysep) * (mechlist->mech_length - 1))
            + mech_names_len()
            + (suffix ? strlen(suffix) : 0)
            + 1;
  ret = _buf_alloc(&conn->mechlist_buf,
                   &conn->mechlist_buf_len, resultlen);
  if(ret != SASL_OK) MEMERROR(conn);

  if (prefix)
    strcpy (conn->mechlist_buf,prefix);
  else
    *(conn->mechlist_buf) = '\0';

  listptr = mechlist->mech_list;  
   
  flag = 0;
  /* make list */
  for (lup = 0; lup < mechlist->mech_length; lup++) {
      /* currently, we don't use the "user" parameter for anything */
      if (mech_permitted(conn, listptr)) {
          if (pcount != NULL)
              (*pcount)++;

          /* print seperator */
          if (flag) {
              strcat(conn->mechlist_buf, mysep);
          } else {
              flag = 1;
          }

          /* now print the mechanism name */
          strcat(conn->mechlist_buf, listptr->plug->mech_name);
      }

      listptr = listptr->next;
  }

  if (suffix)
      strcat(conn->mechlist_buf,suffix);

  if (plen!=NULL)
      *plen=strlen(conn->mechlist_buf);

  *result = conn->mechlist_buf;

  return SASL_OK;
  
}

sasl_string_list_t *_sasl_server_mechs(void) 
{
  mechanism_t *listptr;
  sasl_string_list_t *retval = NULL, *next=NULL;

  if(!_sasl_server_active) return NULL;

  /* make list */
  for (listptr = mechlist->mech_list; listptr; listptr = listptr->next) {
      next = sasl_ALLOC(sizeof(sasl_string_list_t));

      if(!next && !retval) return NULL;
      else if(!next) {
          next = retval->next;
          do {
              sasl_FREE(retval);
              retval = next;
              next = retval->next;
          } while(next);
          return NULL;
      }
      
      next->d = listptr->plug->mech_name;

      if(!retval) {
          next->next = NULL;
          retval = next;
      } else {
          next->next = retval;
          retval = next;
      }
  }

  return retval;
}

#define EOSTR(s,n) (((s)[n] == '\0') || ((s)[n] == ' ') || ((s)[n] == '\t'))
static int is_mech(const char *t, const char *m)
{
    int sl = strlen(m);
    return ((!strncasecmp(m, t, sl)) && EOSTR(t, sl));
}

/* returns OK if it's valid */
static int _sasl_checkpass(sasl_conn_t *conn, const char *service,
                           const char *user, const char *pass)
{
    sasl_server_conn_t *s_conn = (sasl_server_conn_t *) conn;
    int result;
    sasl_getopt_t *getopt;
    sasl_server_userdb_checkpass_t *checkpass_cb;
    void *context;
    const char *mlist, *mech;
    struct sasl_verify_password_s *v;

    /* call userdb callback function, if available */
    result = _sasl_getcallback(conn, SASL_CB_SERVER_USERDB_CHECKPASS,
                               &checkpass_cb, &context);
    if(result == SASL_OK && checkpass_cb) {
        result = checkpass_cb(conn, context, user, pass, strlen(pass),
                              s_conn->sparams->propctx);
        if(result == SASL_OK)
            return SASL_OK;
    }

    /* figure out how to check (i.e. auxprop or saslauthd or pwcheck) */
    if (_sasl_getcallback(conn, SASL_CB_GETOPT, &getopt, &context)
            == SASL_OK) {
        getopt(context, NULL, "pwcheck_method", &mlist, NULL);
    }

    if(!mlist) mlist = DEFAULT_CHECKPASS_MECH;

    result = SASL_NOMECH;

    mech = mlist;
    while (*mech && result != SASL_OK) {
        for (v = _sasl_verify_password; v->name; v++) {
            if(is_mech(mech, v->name)) {
                result = v->verify(conn, user, pass, service,
                                   s_conn->user_realm);
                break;
            }
        }
        if (result != SASL_OK) {
            /* skip to next mech in list */
            while (*mech && !isspace((int) *mech)) mech++;
            while (*mech && isspace((int) *mech)) mech++;
        }
    }

    if (result == SASL_NOMECH) {
        /* no mechanism available ?!? */
        _sasl_log(conn, SASL_LOG_ERR, "unknown password verifier %s", mech);
    }

    if (result != SASL_OK)
        sasl_seterror(conn, SASL_NOLOG, "checkpass failed");

    RETURN(conn, result);
}

/* check if a plaintext password is valid
 *   if user is NULL, check if plaintext passwords are enabled
 * inputs:
 *  user          -- user to query in current user_domain
 *  userlen       -- length of username, 0 = strlen(user)
 *  pass          -- plaintext password to check
 *  passlen       -- length of password, 0 = strlen(pass)
 * returns 
 *  SASL_OK       -- success
 *  SASL_NOMECH   -- mechanism not supported
 *  SASL_NOVERIFY -- user found, but no verifier
 *  SASL_NOUSER   -- user not found
 */
int sasl_checkpass(sasl_conn_t *conn,
                   const char *user,
                   unsigned userlen __attribute__((unused)),
                   const char *pass,
                   unsigned passlen)
{
    int result;
    
    if (_sasl_server_active==0) return SASL_NOTINIT;
    
    /* check if it's just a query if we are enabled */
    if (!user)
        return SASL_OK;

    if (!conn) return SASL_BADPARAM;
    
    /* check params */
    if (pass == NULL)
        PARAMERROR(conn);

    result = _sasl_checkpass(conn, conn->service, user, pass);

    if (result == SASL_OK) {
        strncpy(conn->authid_buf, user, CANON_BUF_SIZE);
        conn->oparams.authid = conn->authid_buf;
      
        result = _sasl_transition(conn, pass, passlen);
    }

    RETURN(conn,result);
}

/* check if a user exists on server
 *  conn          -- connection context (may be NULL, used to hold last error)
 *  service       -- registered name of the service using SASL (e.g. "imap")
 *  user_realm    -- permits multiple user realms on server, NULL = default
 *  user          -- NUL terminated user name
 *
 * returns:
 *  SASL_OK       -- success
 *  SASL_DISABLED -- account disabled [FIXME: currently not detected]
 *  SASL_NOUSER   -- user not found
 *  SASL_NOVERIFY -- user found, but no usable mechanism [FIXME: not supported]
 *  SASL_NOMECH   -- no mechanisms enabled
 */
int sasl_user_exists(sasl_conn_t *conn,
                     const char *service,
                     const char *user_realm,
                     const char *user) 
{
    int result=SASL_NOMECH;
    const char *mlist, *mech;
    void *context;
    sasl_getopt_t *getopt;
    struct sasl_verify_password_s *v;
    
    /* check params */
    if (_sasl_server_active==0) return SASL_NOTINIT;
    if (!conn) return SASL_BADPARAM;
    if (!user || conn->type != SASL_CONN_SERVER) 
        PARAMERROR(conn);

    if(!service) service = conn->service;
    
    /* figure out how to check (i.e. auxprop or saslauthd or pwcheck) */
    if (_sasl_getcallback(conn, SASL_CB_GETOPT, &getopt, &context)
            == SASL_OK) {
        getopt(context, NULL, "pwcheck_method", &mlist, NULL);
    }

    if(!mlist) mlist = DEFAULT_CHECKPASS_MECH;

    result = SASL_NOMECH;

    mech = mlist;
    while (*mech && result != SASL_OK) {
        for (v = _sasl_verify_password; v->name; v++) {
            if(is_mech(mech, v->name)) {
                result = v->verify(conn, user, NULL, service, user_realm);
                break;
            }
        }
        if (result != SASL_OK) {
            /* skip to next mech in list */
            while (*mech && !isspace((int) *mech)) mech++;
            while (*mech && isspace((int) *mech)) mech++;
        }
    }

    /* Screen out the SASL_BADPARAM response
     * we'll get from not giving a password */
    if(result == SASL_BADPARAM) {
        result = SASL_OK;
    }

    if (result == SASL_NOMECH) {
        /* no mechanism available ?!? */
        _sasl_log(conn, SASL_LOG_ERR, "no plaintext password verifier?");
        sasl_seterror(conn, SASL_NOLOG, "no plaintext password verifier?");
    }

    RETURN(conn, result);
}

/* check if an apop exchange is valid
 *  (note this is an optional part of the SASL API)
 *  if challenge is NULL, just check if APOP is enabled
 * inputs:
 *  challenge     -- challenge which was sent to client
 *  challen       -- length of challenge, 0 = strlen(challenge)
 *  response      -- client response, "<user> <digest>" (RFC 1939)
 *  resplen       -- length of response, 0 = strlen(response)
 * returns 
 *  SASL_OK       -- success
 *  SASL_BADAUTH  -- authentication failed
 *  SASL_BADPARAM -- missing challenge
 *  SASL_BADPROT  -- protocol error (e.g., response in wrong format)
 *  SASL_NOVERIFY -- user found, but no verifier
 *  SASL_NOMECH   -- mechanism not supported
 *  SASL_NOUSER   -- user not found
 */
int sasl_checkapop(sasl_conn_t *conn,
#ifdef DO_SASL_CHECKAPOP
                   const char *challenge,
                   unsigned challen __attribute__((unused)),
                   const char *response,
                   unsigned resplen __attribute__((unused)))
#else
                   const char *challenge __attribute__((unused)),
                   unsigned challen __attribute__((unused)),
                   const char *response __attribute__((unused)),
                   unsigned resplen __attribute__((unused)))
#endif
{
#ifdef DO_SASL_CHECKAPOP
    sasl_server_conn_t *s_conn = (sasl_server_conn_t *) conn;
    char *user, *user_end;
    const char *password_request[] = { SASL_AUX_PASSWORD, NULL };
    size_t user_len;
    int result;

    if (_sasl_server_active==0)
        return SASL_NOTINIT;

    /* check if it's just a query if we are enabled */
    if(!challenge)
        return SASL_OK;

    /* check params */
    if (!conn) return SASL_BADPARAM;
    if (!response)
        PARAMERROR(conn);

    /* Parse out username and digest.
     *
     * Per RFC 1939, response must be "<user> <digest>", where
     * <digest> is a 16-octet value which is sent in hexadecimal
     * format, using lower-case ASCII characters.
     */
    user_end = strrchr(response, ' ');
    if (!user_end || strspn(user_end + 1, "0123456789abcdef") != 32) 
    {
        sasl_seterror(conn, 0, "Bad Digest");
        RETURN(conn,SASL_BADPROT);
    }
 
    user_len = (size_t)(user_end - response);
    user = sasl_ALLOC(user_len + 1);
    memcpy(user, response, user_len);
    user[user_len] = '\0';

    result = prop_request(s_conn->sparams->propctx, password_request);
    if(result != SASL_OK) 
    {
        sasl_FREE(user);
        RETURN(conn, result);
    }

    /* Cannonify it */
    result = _sasl_canon_user(conn, user, user_len,
                              SASL_CU_AUTHID | SASL_CU_AUTHZID,
                              &(conn->oparams));
    sasl_FREE(user);

    if(result != SASL_OK) RETURN(conn, result);

    /* Do APOP verification */
    result = _sasl_auxprop_verify_apop(conn, conn->oparams.authid,
        challenge, user_end + 1, s_conn->user_realm);

    /* If verification failed, we don't want to encourage getprop to work */
    if(result != SASL_OK) {
        conn->oparams.user = NULL;
        conn->oparams.authid = NULL;
    }

    RETURN(conn, result);
#else /* sasl_checkapop was disabled at compile time */
    sasl_seterror(conn, SASL_NOLOG,
        "sasl_checkapop called, but was disabled at compile time");
    RETURN(conn, SASL_NOMECH);
#endif /* DO_SASL_CHECKAPOP */
}