/*
 * ProFTPD: mod_delay -- a module for adding arbitrary delays to the FTP
 *                       session lifecycle
 * Copyright (c) 2004-2022 TJ Saunders
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA 02110-1335, USA.
 *
 * As a special exemption, TJ Saunders and other respective copyright holders
 * give permission to link this program with OpenSSL, and distribute the
 * resulting executable, without including the source code for OpenSSL in the
 * source distribution.
 *
 * This is mod_delay, contrib software for proftpd 1.3.x and above.
 * For more information contact TJ Saunders <tj@castaglia.org>.
 */

#include "conf.h"
#include "privs.h"

#define MOD_DELAY_VERSION		"mod_delay/0.7"

/* Make sure the version of proftpd is as necessary. */
#if PROFTPD_VERSION_NUMBER < 0x0001021001
# error "ProFTPD 1.2.10rc1 or later required"
#endif

#ifdef HAVE_SYS_MMAN_H
# include <sys/mman.h>
#endif

/* On some platforms, this may not be defined.  On AIX, for example, this
 * symbol is only defined when _NO_PROTO is defined, and _XOPEN_SOURCE is 500.
 * How annoying.
 */
#ifndef MAP_FAILED
# define MAP_FAILED	((void *) -1)
#endif

#if defined(PR_USE_CTRLS)
# include <mod_ctrls.h>
#endif /* PR_USE_CTRLS */

/* Number of values to keep in a row. */
#ifndef DELAY_NVALUES
# define DELAY_NVALUES			256
#endif

/* Fraction of total values that are accepted from a single session. */
#ifndef DELAY_SESS_NVALUES
# define DELAY_SESS_NVALUES		16
#endif

/* The mod_delay tables have separate entries for different protocols;
 * the implementation/handling of one protocol means that that protocol can
 * have different timings from others.  For example, due to the encryption
 * overhead, authentication via SSL can take longer than without SSL.  Thus
 * we need to keep the per-protocol timings separate.
 *
 * We currently allocate space for three protocols:
 *
 *  ftp
 *  ftps
 *  ssh2
 *
 * If more protocols are supported by proftpd, this this DELAY_NPROTO value
 * should be increased accordingly.  The delay_table_reset() function will
 * also need updating, to include the new protocol, as well.
 */
#define DELAY_NPROTO			3

/* Define an absolute upper limit on the delay values selected, in usecs.
 *
 * I originally wanted a ceiling of 1 hour, but when converted to usecs, the
 * value exceeded LONG_MAX.  So instead, we use 1800000000 usecs (30 min).
 */
#define DELAY_MAX_DELAY_USECS			1800000000L

/* Define an upper bound on the interval we will use, between time of connect
 * and time of USER command.  This is currently limited to 60 seconds.
 */
#define DELAY_MAX_CONNECT_INTERVAL_USECS	60000000L

#if defined(PR_USE_CTRLS)
static ctrls_acttab_t delay_acttab[];
#endif /* PR_USE_CTRLS */

extern xaset_t *server_list;

module delay_module;

struct delay_vals_rec {
  char dv_proto[16];
  unsigned int dv_nvals;
  long dv_vals[DELAY_NVALUES];
};

struct delay_rec {
  unsigned int d_sid;
  char d_addr[80];
  unsigned int d_port;
  struct delay_vals_rec d_vals[DELAY_NPROTO];
};

struct {
  int dt_enabled;
  const char *dt_path;
  int dt_fd;
  size_t dt_size;
  void *dt_data;

} delay_tab;

static unsigned int delay_engine = TRUE;
static unsigned int delay_nuser = 0;
static unsigned int delay_npass = 0;
static unsigned long delay_user_delayed = 0L;
static unsigned long delay_pass_delayed = 0L;
static pool *delay_pool = NULL;
static struct timeval delay_tv;

/* DelayOnEvent events */
#define DELAY_EVENT_USER_CMD		1
#define DELAY_EVENT_PASS_CMD		2
#define DELAY_EVENT_FAILED_LOGIN	3

static unsigned long delay_failed_login_min_delay = 0UL;
static unsigned long delay_pass_min_delay = 0UL;
static unsigned long delay_user_min_delay = 0UL;

static int delay_sess_init(void);
static void delay_table_reset(void);

#define delay_swap(a, b) \
  tmp = (a); \
  (a) = (b); \
  (b) = tmp;

static const char *trace_channel = "delay";

static long delay_select_k(unsigned long k, array_header *values) {
  unsigned long l, ir, tmp = 0;
  long *elts = (long *) values->elts;
  unsigned int nelts = values->nelts;

  /* This is from "Numeric Recipes in C", Ch. 8.5, as the select()
   * algorithm, an in-place sorting algorithm for finding the Kth
   * element in an array, where all elements to the left of K are
   * smaller than K, and all elements to the right are larger.
   */

  l = 1;
  ir = values->nelts - 1;

  while (TRUE) {
    unsigned int i, j;
    long p;
    unsigned long mid;

    pr_signals_handle();

    if (ir <= l+1) {
      if (ir == l+1 &&
          elts[ir] < elts[l]) {
        delay_swap(elts[l], elts[ir]);
      }

      return elts[k];
    }

    mid = (l + ir) >> 1;

    delay_swap(elts[mid], elts[l+1]);
    if (elts[l] > elts[ir]) {
      delay_swap(elts[l], elts[ir]);
    }

    if (elts[l+1] > elts[ir]) {
      delay_swap(elts[l+1], elts[ir]);
    }

    if (elts[l] > elts[l+1]) {
      delay_swap(elts[l], elts[l+1]);
    }

    i = l + 1;
    j = ir;
    p = elts[l+1];

    while (TRUE) {
      pr_signals_handle();

      do {
        i++;
      } while (i < nelts && elts[i] < p);

      do {
        j--;
      } while (elts[j] > p);

      if (j < i) {
        break;
      }

      delay_swap(elts[i], elts[j]);
    }

    elts[l+1] = elts[j];
    elts[j] = p;

    if ((unsigned long) p >= k) {
      ir = j - 1;
    }

    if ((unsigned long) p <= k) {
      l = i;
    }

    if (l >= (nelts - 1) ||
        ir >= nelts) {
      break;
    }
  }

  return -1;
}

static long delay_get_median(pool *p, unsigned int rownum, const char *protocol,
    long interval) {
  register unsigned int i;
  struct delay_rec *row;
  struct delay_vals_rec *dv = NULL;
  long *tab_vals = NULL, median;
  array_header *list = make_array(p, 1, sizeof(long));
  
  /* Calculate the median value of the current command's recorded values,
   * taking the protocol (e.g. "ftp", "ftps", "ssh2") into account.
   *
   * When calculating the median, we use the current interval as well
   * as the recorded intervals in the table, giving us an odd number of
   * values.
   *
   * If the number of values in this row is less than the watermark
   * value, we'll actually return the maximum value, rather than the
   * median.  Below the watermark, the server is "cold" and has not
   * yet accumulated enough data to make the median a useful value.
   */

  row = &((struct delay_rec *) delay_tab.dt_data)[rownum];

  /* Find the list of delay values that match the given protocol. */
  for (i = 0; i < DELAY_NPROTO; i++) {
    dv = &(row->d_vals[i]);
    if (strcmp(dv->dv_proto, protocol) == 0) {
      tab_vals = dv->dv_vals;
      break;
    }
  }

  /* Start at the end of the row and work backward, as values are
   * always added at the end of the row, shifting everything to the left.
   */
  if (tab_vals != NULL) {
    for (i = 1; i < dv->dv_nvals; i++) {
      /* Ignore any possible garbage (i.e. negative) values in the
       * DelayTable.
       */
      if (tab_vals[DELAY_NVALUES - 1 - i] >= 0) {
        *((long *) push_array(list)) = tab_vals[DELAY_NVALUES - 1 - i];
      }
    }
  }
  *((long *) push_array(list)) = interval;

  pr_trace_msg(trace_channel, 6, "selecting median interval from %d %s",
    list->nelts, list->nelts != 1 ? "values" : "value");

  median = delay_select_k(((list->nelts + 1) / 2), list);
  if (median >= 0) {

    /* Enforce an additional restriction: no delays over a hard limit. */
    if (median >= DELAY_MAX_DELAY_USECS) {
      pr_trace_msg(trace_channel, 1,
        "selected median (%ld usecs) exceeds max delay (%ld usecs), ignoring",
        median, (long) DELAY_MAX_DELAY_USECS);
      pr_log_debug(DEBUG5, MOD_DELAY_VERSION
        ": selected median (%ld usecs) exceeds max delay (%ld usecs), ignoring",
        median, (long) DELAY_MAX_DELAY_USECS);
      median = -1;

    } else {
      pr_trace_msg(trace_channel, 7, "selected median interval of %ld usecs",
        median);
    }
  }

  return median;
}

static int delay_mask_signals(unsigned char block) {
  static sigset_t mask_sigset;
  int res = -1;

  if (block) {
    sigemptyset(&mask_sigset);

    sigaddset(&mask_sigset, SIGCHLD);
    sigaddset(&mask_sigset, SIGUSR1);
    sigaddset(&mask_sigset, SIGINT);
    sigaddset(&mask_sigset, SIGQUIT);
#ifdef SIGIO
    sigaddset(&mask_sigset, SIGIO);
#endif
#ifdef SIGBUS
    sigaddset(&mask_sigset, SIGBUS);
#endif
    sigaddset(&mask_sigset, SIGHUP);

    res = sigprocmask(SIG_BLOCK, &mask_sigset, NULL);

  } else {
    res = sigprocmask(SIG_UNBLOCK, &mask_sigset, NULL);
  }

  return res;
}

static void delay_signals_block(void) {
  if (delay_mask_signals(TRUE) < 0) {
    pr_trace_msg(trace_channel, 1,
      "error blocking signals: %s", strerror(errno));
  }   
}

static void delay_signals_unblock(void) {
  if (delay_mask_signals(FALSE) < 0) {
    pr_trace_msg(trace_channel, 1,
      "error unblocking signals: %s", strerror(errno));
  }
}

static unsigned long delay_delay(unsigned long interval) {
  struct timeval tv;
  int res, xerrno;

  tv.tv_sec = interval / 1000000;
  tv.tv_usec = interval % 1000000;

  pr_trace_msg(trace_channel, 8, "delaying for %ld usecs",
    (long int) ((tv.tv_sec * 1000000) + tv.tv_usec));

  delay_signals_block();
  res = select(0, NULL, NULL, NULL, &tv);
  xerrno = errno;
  delay_signals_unblock();

  if (res < 0 &&
      xerrno == EINTR) {

    /* If we were interrupted, handle the interrupting signal. */
    pr_signals_handle();
  }

  return interval;
}

static unsigned long delay_delay_with_jitter(long interval) {
  long rand_usec;

  /* Add an additional delay of a random number of usecs, with a
   * maximum of half of the given interval.
   */
  rand_usec = ((interval / 2.0) * rand()) / RAND_MAX;
  pr_trace_msg(trace_channel, 8, "additional random delay of %ld usecs added",
    (long int) rand_usec);
  interval += rand_usec;

  if (interval > DELAY_MAX_DELAY_USECS) {
    interval = DELAY_MAX_DELAY_USECS;
  }

  return delay_delay(interval);
}

/* Similar to the pr_str_get_duration() function, but parses millisecond
 * values, not seconds.
 */
static int delay_str_get_duration_ms(const char *str, long *duration) {
  unsigned int mins, secs;
  long msecs;
  int flags = PR_STR_FL_IGNORE_CASE, has_suffix = FALSE;
  size_t len;
  char *ptr = NULL;

  if (str == NULL) {
    errno = EINVAL;
    return -1;
  }

  if (sscanf(str, "%2u:%2u.%4lu", &mins, &secs, &msecs) == 3) {
    if (mins > INT_MAX ||
        secs > INT_MAX ||
        msecs > INT_MAX) {
      errno = ERANGE;
      return -1;
    }

    if (duration != NULL) {
      *duration = (mins * 60 * 1000) + (secs * 1000) + msecs;
    }

    return 0;
  }

  len = strlen(str);
  if (len == 0) {
    errno = EINVAL;
    return -1;
  }

  has_suffix = pr_strnrstr(str, len, "ms", 2, flags);
  if (has_suffix == TRUE) {
    /* Parse millisecs */

    if (sscanf(str, "%ld", &msecs) == 1) {
      if (msecs > INT_MAX) {
        errno = ERANGE;
        return -1;
      }

      if (duration != NULL) {
        *duration = msecs;
      }

      return 0;
    }

    errno = EINVAL;
    return -1;
  }

  has_suffix = pr_strnrstr(str, len, "s", 1, flags);
  if (has_suffix == FALSE) {
    has_suffix = pr_strnrstr(str, len, "sec", 3, flags);
  }
  if (has_suffix == TRUE) {
    /* Parse seconds */

    if (sscanf(str, "%u", &secs) == 1) {
      if (secs > INT_MAX) {
        errno = ERANGE;
        return -1;
      }

      if (duration != NULL) {
        *duration = (secs * 1000);
      }

      return 0;
    }

    errno = EINVAL;
    return -1;
  }

  /* Use strtol(3) here, check for trailing garbage, etc. */
  msecs = strtol(str, &ptr, 10);
  if (ptr && *ptr) {
    /* Not a bare number, but a string with non-numeric characters. */
    errno = EINVAL;
    return -1;
  }

  if (msecs < 0 ||
      msecs > INT_MAX) {
    errno = ERANGE;
    return -1;
  }

  if (duration != NULL) {
    *duration = msecs;
  }

  return 0;
}

/* There are two rows (USER and PASS) for each server ID (SID).
 *
 * The main server has a SID of 1.  Thus to access the USER row for SID 1,
 * the row index is 0; the PASS row for SID 1 has a row index of 1.
 *
 * The general formula for the USER row of a given SID is:
 *
 *   r = (sid * 2) - 2;
 *
 * and thus for accessing the PASS row, the formula is:
 *
 *   r = (sid * 2) - 1;
 */
static unsigned int delay_get_user_rownum(unsigned int sid) {
  unsigned int r;

  r = (sid * 2) - 2;
  return r;
}

static unsigned int delay_get_pass_rownum(unsigned int sid) {
  unsigned int r;

  r = (sid * 2) - 1;
  return r;
}

static void delay_table_add_interval(unsigned int rownum, const char *protocol,
    long interval) {
  register unsigned int i;
  struct delay_rec *row;
  struct delay_vals_rec *dv = NULL;

  row = &((struct delay_rec *) delay_tab.dt_data)[rownum];

  for (i = 0; i < DELAY_NPROTO; i++) {
    dv = &(row->d_vals[i]);
    if (strcmp(dv->dv_proto, protocol) == 0) {
      break;
    }
  }

  /* Shift all existing values to the left one position. */
  memmove(&(dv->dv_vals[0]), &(dv->dv_vals[1]),
    sizeof(long) * (DELAY_NVALUES - 1));

  /* Add the given value to the end. */

  if (interval > DELAY_MAX_DELAY_USECS) {
    /* Truncate the interval to the maximum allowed value. */
    interval = DELAY_MAX_DELAY_USECS;
  }

  dv->dv_vals[DELAY_NVALUES-1] = interval;
  if (dv->dv_nvals < DELAY_NVALUES) {
    dv->dv_nvals++;
  }
}

static int delay_table_init(void) {
  pr_fh_t *fh;
  struct stat st;
  server_rec *s;
  unsigned int nservers = 0;
  off_t tab_size;
  int flags = O_RDWR|O_CREAT;
  int reset_table = FALSE, xerrno = 0;

  /* We only want to create the table if it does not already exist.
   *
   * If the ServerType is inetd, we want to leave the current contents
   * alone (don't we want to check to see that it's appropriate, sid-wise,
   * for the current server_list?), otherwise, we reset the table.
   *
   * The size of the table should be:
   *
   *  number of vhosts * 2 * row size
   */

  for (s = (server_rec *) server_list->xas_list; s; s = s->next) {
    nservers++;
  }

  tab_size = nservers * 2 * sizeof(struct delay_rec);

  PRIVS_ROOT
  fh = pr_fsio_open(delay_tab.dt_path, flags);
  xerrno = errno;
  PRIVS_RELINQUISH

  if (fh == NULL) {
    pr_log_debug(DEBUG0, MOD_DELAY_VERSION
      ": error opening DelayTable '%s': %s", delay_tab.dt_path,
      strerror(xerrno));
    pr_trace_msg(trace_channel, 1, "error opening DelayTable '%s': %s",
      delay_tab.dt_path, strerror(xerrno));
    errno = xerrno;
    return -1;
  }

  /* Find a usable fd for the just-opened DelayTable fd. */
  if (pr_fs_get_usable_fd2(&(fh->fh_fd)) < 0) {
    pr_log_debug(DEBUG0, MOD_DELAY_VERSION
      ": warning: unable to find good fd for DelayTable %d: %s",
      fh->fh_fd, strerror(errno));
  }

  /* Set the close-on-exec flag, for safety. */
  if (fcntl(fh->fh_fd, F_SETFD, FD_CLOEXEC) < 0) {
    pr_log_pri(PR_LOG_WARNING, MOD_DELAY_VERSION
      ": unable to set CLO_EXEC on DelayTable fd %d: %s", fh->fh_fd,
      strerror(errno));
  }

  if (pr_fsio_fstat(fh, &st) < 0) {
    xerrno = errno;

    pr_trace_msg(trace_channel, 1, "error stat'ing DelayTable '%s': %s",
      delay_tab.dt_path, strerror(xerrno));
    pr_fsio_close(fh);

    errno = xerrno;
    return -1;
  }

  if (S_ISDIR(st.st_mode)) {
    xerrno = EISDIR;

    pr_trace_msg(trace_channel, 1, "error using DelayTable '%s': %s",
      delay_tab.dt_path, strerror(xerrno));
    pr_fsio_close(fh);

    errno = xerrno;
    return -1;
  }

  if (st.st_size != tab_size) {
    /* This check is for cases when the ServerType is inetd, and the
     * current DelayTable has the wrong size, which can happen if the
     * configuration has changed by having vhosts added or removed.
     */

    pr_trace_msg(trace_channel, 3,
      "expected table size %" PR_LU ", found %" PR_LU ", resetting table",
      (pr_off_t) tab_size, (pr_off_t) st.st_size);
    reset_table = TRUE;
  }

  if (reset_table) {
    struct flock lock;

    lock.l_type = F_WRLCK;
    lock.l_whence = 0;
    lock.l_start = 0;
    lock.l_len = 0;

    pr_trace_msg(trace_channel, 8, "write-locking DelayTable '%s'",
      fh->fh_path);
    while (fcntl(fh->fh_fd, F_SETLKW, &lock) < 0) {
      xerrno = errno;

      if (errno == EINTR) {
        pr_signals_handle();
        continue;
      }

      pr_log_pri(PR_LOG_WARNING, MOD_DELAY_VERSION
        ": unable to obtain write lock on DelayTable '%s': %s",
        fh->fh_path, strerror(xerrno));
      pr_trace_msg(trace_channel, 1,
        "unable to obtain write lock on DelayTable '%s': %s", fh->fh_path,
        strerror(xerrno));
      pr_fsio_close(fh);

      errno = xerrno;
      return -1;
    } 

    /* Seek to the desired table size (actually, one byte less than the
     * desired size) and write a single byte, so that there's enough
     * allocated backing store on the filesystem to support the ensuing
     * mmap() call.
     */
    if (lseek(fh->fh_fd, tab_size-1, SEEK_SET) < 0) {
      xerrno = errno;

      pr_log_pri(PR_LOG_WARNING, MOD_DELAY_VERSION
        ": error seeking to %lu in DelayTable '%s': %s",
        (unsigned long) tab_size-1, fh->fh_path, strerror(xerrno));
      pr_trace_msg(trace_channel, 1,
        "error seeking to %lu in DelayTable '%s': %s",
        (unsigned long) tab_size-1, fh->fh_path, strerror(xerrno));

      pr_fsio_close(fh);

      errno = xerrno;
      return -1;
    }

    if (write(fh->fh_fd, "", 1) != 1) {
      xerrno = errno;

      pr_log_pri(PR_LOG_WARNING, MOD_DELAY_VERSION
        ": error writing single byte to DelayTable '%s': %s", fh->fh_path,
        strerror(xerrno));
      pr_trace_msg(trace_channel, 1,
        "error writing single byte to DelayTable '%s': %s", fh->fh_path,
        strerror(xerrno));

      pr_fsio_close(fh);

      errno = xerrno;
      return -1;
    }

    /* Truncate the table, in case we're shrinking an existing table. */
    pr_fsio_ftruncate(fh, tab_size);

    lock.l_type = F_UNLCK;

    pr_trace_msg(trace_channel, 8, "unlocking DelayTable '%s'", fh->fh_path);
    if (fcntl(fh->fh_fd, F_SETLK, &lock) < 0) {
      pr_trace_msg(trace_channel, 3,
        "error unlocking fd %d: %s", fh->fh_fd, strerror(errno));
    }
  }

  delay_tab.dt_fd = fh->fh_fd;
  delay_tab.dt_size = (size_t) tab_size;

  pr_trace_msg(trace_channel, 8, "mapping DelayTable '%s' (%lu bytes, fd %d) "
    "into memory", fh->fh_path, (unsigned long) delay_tab.dt_size,
    delay_tab.dt_fd);
  delay_tab.dt_data = mmap(NULL, delay_tab.dt_size, PROT_READ|PROT_WRITE,
    MAP_SHARED, delay_tab.dt_fd, 0);

  if (delay_tab.dt_data == MAP_FAILED) {
    xerrno = errno;

    delay_tab.dt_data = NULL;

    pr_log_pri(PR_LOG_WARNING, MOD_DELAY_VERSION
      ": error mapping DelayTable '%s' into memory: %s", delay_tab.dt_path,
      strerror(xerrno));
    pr_trace_msg(trace_channel, 1,
      "error mapping DelayTable '%s' into memory: %s", delay_tab.dt_path,
      strerror(xerrno));

    pr_fsio_close(fh);
    delay_tab.dt_fd = -1;

    errno = xerrno;
    return -1;
  }

  if (!reset_table) {
    struct delay_rec *row;

    for (s = (server_rec *) server_list->xas_list; s; s = s->next) {
      unsigned int r;
      const char *ip_str;

      /* Row for USER values */
      r = delay_get_user_rownum(s->sid);
      row = &((struct delay_rec *) delay_tab.dt_data)[r];
      ip_str = pr_netaddr_get_ipstr(s->addr);
      if (ip_str == NULL) {
        continue;
      }

      if (strcmp(ip_str, row->d_addr) != 0) {
        reset_table = TRUE;
        break;
      }

      if (s->ServerPort != row->d_port) {
        reset_table = TRUE;
        break;
      }

      /* Row for PASS values */
      r = delay_get_pass_rownum(s->sid);
      row = &((struct delay_rec *) delay_tab.dt_data)[r];
      if (strcmp(ip_str, row->d_addr) != 0) {
        reset_table = TRUE;
        break;
      }

      if (s->ServerPort != row->d_port) {
        reset_table = TRUE;
        break;
      }
    }
  }

  if (reset_table) {
    struct flock lock;

    lock.l_type = F_WRLCK;
    lock.l_whence = 0;
    lock.l_start = 0;
    lock.l_len = 0;

    pr_trace_msg(trace_channel, 8, "write-locking DelayTable '%s'",
      fh->fh_path);
    while (fcntl(fh->fh_fd, F_SETLKW, &lock) < 0) {
      xerrno = errno;

      if (errno == EINTR) {
        pr_signals_handle();
        continue;
      }

      pr_log_pri(PR_LOG_WARNING, MOD_DELAY_VERSION
        ": unable to obtain write lock on DelayTable '%s': %s",
        fh->fh_path, strerror(xerrno));
      pr_trace_msg(trace_channel, 1,
        "unable to obtain write lock on DelayTable '%s': %s", fh->fh_path,
        strerror(xerrno));
      pr_fsio_close(fh);

      errno = xerrno;
      return -1;
    }

    /* Seek to the desired table size (actually, one byte less than the
     * desired size) and write a single byte, so that there's enough
     * allocated backing store on the filesystem to support the ensuing
     * mmap() call.
     */
    if (lseek(fh->fh_fd, tab_size-1, SEEK_SET) < 0) {
      xerrno = errno;

      pr_log_pri(PR_LOG_WARNING, MOD_DELAY_VERSION
        ": error seeking to %lu in DelayTable '%s': %s",
        (unsigned long) tab_size-1, fh->fh_path, strerror(xerrno));
      pr_trace_msg(trace_channel, 1,
        "error seeking to %lu in DelayTable '%s': %s",
        (unsigned long) tab_size-1, fh->fh_path, strerror(xerrno));

      pr_fsio_close(fh);

      errno = xerrno;
      return -1;
    }

    if (write(fh->fh_fd, "", 1) != 1) {
      xerrno = errno;

      pr_log_pri(PR_LOG_WARNING, MOD_DELAY_VERSION
        ": error writing single byte to DelayTable '%s': %s", fh->fh_path,
        strerror(xerrno));
      pr_trace_msg(trace_channel, 1,
        "error writing single byte to DelayTable '%s': %s", fh->fh_path,
        strerror(xerrno));

      pr_fsio_close(fh);

      errno = xerrno;
      return -1;
    }

    /* Truncate the table, in case we're shrinking an existing table. */
    pr_fsio_ftruncate(fh, tab_size);

    pr_trace_msg(trace_channel, 6, "resetting DelayTable '%s'",
      delay_tab.dt_path);
    delay_table_reset();

    lock.l_type = F_UNLCK;

    pr_trace_msg(trace_channel, 8, "unlocking DelayTable '%s'", fh->fh_path);
    if (fcntl(fh->fh_fd, F_SETLK, &lock) < 0) {
      pr_trace_msg(trace_channel, 3,
        "error unlocking fd %d: %s", fh->fh_fd, strerror(errno));
    }
  }

  /* Done */
  pr_trace_msg(trace_channel, 8, "unmapping DelayTable '%s' from memory",
    delay_tab.dt_path);
  if (munmap(delay_tab.dt_data, delay_tab.dt_size) < 0) {
    xerrno = errno;
    pr_fsio_close(fh);

    pr_log_pri(PR_LOG_WARNING, MOD_DELAY_VERSION
      ": error unmapping DelayTable '%s': %s", delay_tab.dt_path,
      strerror(xerrno));
    pr_trace_msg(trace_channel, 1, "error unmapping DelayTable '%s': %s",
      delay_tab.dt_path, strerror(xerrno));

    errno = xerrno;
    return -1;
  }

  delay_tab.dt_data = NULL;
  delay_tab.dt_fd = -1;

  if (pr_fsio_close(fh) < 0) {
    xerrno = errno;

    pr_log_pri(PR_LOG_WARNING, MOD_DELAY_VERSION
      ": error closing DelayTable '%s': %s", delay_tab.dt_path,
      strerror(xerrno));
    pr_trace_msg(trace_channel, 1, "error closing DelayTable '%s': %s",
      delay_tab.dt_path, strerror(xerrno));

    errno = xerrno;
    return -1;
  }

  return 0;
}

static int delay_table_load(int lock_table) {
  struct flock lock;

  if (lock_table) {
    lock.l_type = F_WRLCK;
    lock.l_whence = 0;
    lock.l_start = 0;
    lock.l_len = 0;

    pr_trace_msg(trace_channel, 8, "write-locking DelayTable '%s'",
      delay_tab.dt_path);
    while (fcntl(delay_tab.dt_fd, F_SETLKW, &lock) < 0) {
      if (errno == EINTR) {
        pr_signals_handle();
        continue;
      }

      return -1;
    }
  }

  if (delay_tab.dt_data == NULL) {
    pr_trace_msg(trace_channel, 8, "mapping DelayTable '%s' (%lu bytes, fd %d) "
      "into memory", delay_tab.dt_path, (unsigned long) delay_tab.dt_size,
      delay_tab.dt_fd);
    delay_tab.dt_data = mmap(NULL, delay_tab.dt_size, PROT_READ|PROT_WRITE,
      MAP_SHARED, delay_tab.dt_fd, 0);

    if (delay_tab.dt_data == MAP_FAILED) {
      int xerrno = errno;

      delay_tab.dt_data = NULL;

      if (lock_table) {
        /* Make sure we release the lock before returning. */
        lock.l_type = F_UNLCK;
        lock.l_whence = 0;
        lock.l_start = 0;
        lock.l_len = 0;

        pr_trace_msg(trace_channel, 8, "unlocking DelayTable '%s'",
          delay_tab.dt_path);
        while (fcntl(delay_tab.dt_fd, F_SETLKW, &lock) < 0) {
          if (errno == EINTR) {
            pr_signals_handle();
            continue;
          }
        }
      }

      errno = xerrno; 
      return -1;
    }
  }

  return 0;
}

static void delay_table_reset(void) {
  server_rec *s;

  for (s = (server_rec *) server_list->xas_list; s; s = s->next) {
    unsigned int r;
    struct delay_rec *row;
    struct delay_vals_rec *dv;
    const char *ip_str;

    ip_str = pr_netaddr_get_ipstr(s->addr);
    if (ip_str == NULL) {
      continue;
    }

    /* Row for USER values */
    r = delay_get_user_rownum(s->sid);
    row = &((struct delay_rec *) delay_tab.dt_data)[r];
    row->d_sid = s->sid;
    sstrncpy(row->d_addr, ip_str, sizeof(row->d_addr));
    row->d_port = s->ServerPort;
    memset(row->d_vals, 0, sizeof(row->d_vals));

    /* Initialize value subsets for "ftp", "ftps", and "ssh2". */
    dv = &(row->d_vals[0]);
    memset(dv->dv_proto, 0, sizeof(dv->dv_proto));
    sstrcat(dv->dv_proto, "ftp", sizeof(dv->dv_proto));
    dv->dv_nvals = 0;
    memset(dv->dv_vals, -1, sizeof(dv->dv_vals));

    dv = &(row->d_vals[1]);
    memset(dv->dv_proto, 0, sizeof(dv->dv_proto));
    sstrcat(dv->dv_proto, "ftps", sizeof(dv->dv_proto));
    dv->dv_nvals = 0;
    memset(dv->dv_vals, -1, sizeof(dv->dv_vals));

    dv = &(row->d_vals[2]);
    memset(dv->dv_proto, 0, sizeof(dv->dv_proto));
    sstrcat(dv->dv_proto, "ssh2", sizeof(dv->dv_proto));
    dv->dv_nvals = 0;
    memset(dv->dv_vals, -1, sizeof(dv->dv_vals));

    /* Row for PASS values */
    r = delay_get_pass_rownum(s->sid);
    row = &((struct delay_rec *) delay_tab.dt_data)[r];
    row->d_sid = s->sid;
    sstrncpy(row->d_addr, ip_str, sizeof(row->d_addr));
    row->d_port = s->ServerPort;
    memset(row->d_vals, 0, sizeof(row->d_vals));

    dv = &(row->d_vals[0]);
    memset(dv->dv_proto, 0, sizeof(dv->dv_proto));
    sstrcat(dv->dv_proto, "ftp", sizeof(dv->dv_proto));
    dv->dv_nvals = 0;
    memset(dv->dv_vals, -1, sizeof(dv->dv_vals));

    dv = &(row->d_vals[1]);
    memset(dv->dv_proto, 0, sizeof(dv->dv_proto));
    sstrcat(dv->dv_proto, "ftps", sizeof(dv->dv_proto));
    dv->dv_nvals = 0;
    memset(dv->dv_vals, -1, sizeof(dv->dv_vals));

    dv = &(row->d_vals[2]);
    memset(dv->dv_proto, 0, sizeof(dv->dv_proto));
    sstrcat(dv->dv_proto, "ssh2", sizeof(dv->dv_proto));
    dv->dv_nvals = 0;
    memset(dv->dv_vals, -1, sizeof(dv->dv_vals));
  }
}

static int delay_table_wlock(unsigned int rownum) {
  struct flock lock;

  lock.l_type = F_WRLCK;
  lock.l_whence = 0;
  lock.l_start = sizeof(struct delay_rec) * rownum;
  lock.l_len = sizeof(struct delay_rec);

  pr_trace_msg(trace_channel, 8, "write-locking DelayTable '%s', row %u",
    delay_tab.dt_path, rownum + 1);
  while (fcntl(delay_tab.dt_fd, F_SETLKW, &lock) < 0) {
    int xerrno = errno;

    if (xerrno == EINTR) {
      pr_signals_handle();
      continue;
    }

    pr_trace_msg(trace_channel, 1, "error locking row: %s", strerror(xerrno));

    errno = xerrno;
    return -1;
  }

  return 0;
}

static int delay_table_unload(int unlock_table) {

  if (delay_tab.dt_data) {
    pr_trace_msg(trace_channel, 8, "unmapping DelayTable '%s' from memory",
      delay_tab.dt_path);
    if (munmap(delay_tab.dt_data, delay_tab.dt_size) < 0) {
      int xerrno = errno;

      pr_log_pri(PR_LOG_WARNING, MOD_DELAY_VERSION
        ": error unmapping DelayTable '%s': %s", delay_tab.dt_path,
        strerror(xerrno));
      pr_trace_msg(trace_channel, 1, "error unmapping DelayTable '%s': %s",
        delay_tab.dt_path, strerror(xerrno));

      errno = xerrno;
      return -1;
    }

    delay_tab.dt_data = NULL;
  }

  if (unlock_table) {
    struct flock lock;
    lock.l_type = F_UNLCK;
    lock.l_whence = SEEK_SET;
    lock.l_start = 0;
    lock.l_len = 0;

    pr_trace_msg(trace_channel, 8, "unlocking DelayTable '%s'",
      delay_tab.dt_path);
    while (fcntl(delay_tab.dt_fd, F_SETLK, &lock) < 0) {
      if (errno == EINTR) {
        pr_signals_handle();
        continue;
      }

      return -1;
    }
  }

  return 0;
}

static int delay_table_unlock(unsigned int rownum) {
  struct flock lock;

  lock.l_type = F_UNLCK;
  lock.l_whence = 0;
  lock.l_start = sizeof(struct delay_rec) * rownum;
  lock.l_len = sizeof(struct delay_rec);

  pr_trace_msg(trace_channel, 8, "unlocking DelayTable '%s', row %u",
    delay_tab.dt_path, rownum + 1);
  while (fcntl(delay_tab.dt_fd, F_SETLKW, &lock) < 0) {
    int xerrno = errno;

    if (xerrno == EINTR) {
      pr_signals_handle();
      continue;
    }

    pr_trace_msg(trace_channel, 1, "error unlocking row: %s", strerror(xerrno));

    errno = xerrno;
    return -1;
  }

  return 0;
}

#if defined(PR_USE_CTRLS)

/* Control handlers
 */

static int delay_handle_info(pr_ctrls_t *ctrl, int reqargc,
    char **reqargv) {
  register server_rec *s;
  pool *tmp_pool;
  pr_fh_t *fh;
  char *vals;
  int xerrno = 0;

  PRIVS_ROOT
  fh = pr_fsio_open(delay_tab.dt_path, O_RDWR);
  xerrno = errno;
  PRIVS_RELINQUISH

  if (fh == NULL) {
    pr_ctrls_add_response(ctrl,
      "warning: unable to open DelayTable '%s': %s", delay_tab.dt_path,
      strerror(xerrno));
    errno = xerrno;
    return -1;
  }

  delay_tab.dt_fd = fh->fh_fd;
  delay_tab.dt_data = NULL;

  if (delay_table_load(TRUE) < 0) {
    xerrno = errno;

    pr_ctrls_add_response(ctrl,
      "unable to load DelayTable '%s' (fd %d) into memory: %s",
      delay_tab.dt_path, delay_tab.dt_fd, strerror(xerrno));
    pr_trace_msg(trace_channel, 1,
      "unable to load DelayTable '%s' (fd %d) into memory: %s",
      delay_tab.dt_path, delay_tab.dt_fd, strerror(xerrno));

    pr_fsio_close(fh);
    delay_tab.dt_fd = -1;
    delay_tab.dt_data = NULL;

    errno = xerrno;
    return -1;
  }

  tmp_pool = make_sub_pool(delay_pool);

  for (s = (server_rec *) server_list->xas_list; s; s = s->next) {
    unsigned int r;
    register unsigned int i;
    struct delay_rec *row;

    /* Row for USER values */
    r = delay_get_user_rownum(s->sid);
    row = &((struct delay_rec *) delay_tab.dt_data)[r];
    pr_ctrls_add_response(ctrl, "Address %s#%u: USER values (usecs):",
      row->d_addr, row->d_port);

    for (i = 0; i < DELAY_NPROTO; i++) {
      struct delay_vals_rec *dv;
      register unsigned int j;

      dv = &(row->d_vals[i]);

      if ((dv->dv_proto)[0] == '\0') {
        continue;
      }

      pr_ctrls_add_response(ctrl, " + Protocol %s, %u values:", dv->dv_proto,
        dv->dv_nvals);

      /* Start at the end of the row and work backward, as values are
       * always added at the end of the row, shifting everything to the left.
       */
      vals = "";
      for (j = 0; j < dv->dv_nvals; j++) {
        char buf[80];

        memset(buf, '\0', sizeof(buf));
        pr_snprintf(buf, sizeof(buf)-1, "%10ld",
          dv->dv_vals[DELAY_NVALUES - 1 - j]);

        vals = pstrcat(tmp_pool, vals, " ", buf, NULL);

        if (j != 0 &&
            j % 4 == 0) {
          pr_ctrls_add_response(ctrl, "    %s", vals);
          vals = "";
        }
      }

      if (strlen(vals) > 0)
        pr_ctrls_add_response(ctrl, "    %s", vals);
    }

    pr_ctrls_add_response(ctrl, "%s", "");

    /* Row for PASS values */
    r = delay_get_pass_rownum(s->sid);
    row = &((struct delay_rec *) delay_tab.dt_data)[r];
    pr_ctrls_add_response(ctrl, "Address %s#%u: PASS values (usecs):",
      row->d_addr, row->d_port);

    for (i = 0; i < DELAY_NPROTO; i++) {
      struct delay_vals_rec *dv;
      register unsigned int j;

      dv = &(row->d_vals[i]);

      if ((dv->dv_proto)[0] == '\0') {
        continue;
      }

      pr_ctrls_add_response(ctrl, " + Protocol %s, %u values:", dv->dv_proto,
        dv->dv_nvals);

      vals = "";
      for (j = 0; j < dv->dv_nvals; j++) {
        char buf[80];

        memset(buf, '\0', sizeof(buf));
        pr_snprintf(buf, sizeof(buf)-1, "%10ld",
          dv->dv_vals[DELAY_NVALUES - 1 - j]);

        vals = pstrcat(tmp_pool, vals, " ", buf, NULL);

        if (j != 0 &&
            j % 4 == 0) {
          pr_ctrls_add_response(ctrl, "    %s", vals);
          vals = "";
        }
      }

      if (strlen(vals) > 0)
        pr_ctrls_add_response(ctrl, "    %s", vals);
    }

    pr_ctrls_add_response(ctrl, "%s", "");
  }

  if (delay_table_unload(TRUE) < 0) {
    pr_ctrls_add_response(ctrl,
      "unable to unload DelayTable '%s' from memory: %s",
      delay_tab.dt_path, strerror(errno));
  }

  pr_fsio_close(fh);

  delay_tab.dt_fd = -1;
  delay_tab.dt_data = NULL;

  destroy_pool(tmp_pool);
  return 0;
}

static int delay_handle_reset(pr_ctrls_t *ctrl, int reqargc,
    char **reqarg) {
  struct flock lock;
  pr_fh_t *fh;
  int xerrno = 0;

  PRIVS_ROOT
  fh = pr_fsio_open(delay_tab.dt_path, O_RDWR);
  xerrno = errno;
  PRIVS_RELINQUISH

  if (fh == NULL) {
    pr_ctrls_add_response(ctrl,
      "unable to open DelayTable '%s': %s", delay_tab.dt_path,
      strerror(xerrno));
    errno = xerrno;
    return -1;
  }

  lock.l_type = F_WRLCK;
  lock.l_whence = 0;
  lock.l_start = 0;
  lock.l_len = 0;

  while (fcntl(fh->fh_fd, F_SETLKW, &lock) < 0) {
    xerrno = errno;

    if (xerrno == EINTR) {
      pr_signals_handle();
      continue;
    }

    pr_ctrls_add_response(ctrl,
      "unable to obtain write lock on DelayTable '%s': %s",
       fh->fh_path, strerror(xerrno));
    pr_fsio_close(fh);

    errno = xerrno;
    return -1;
  }

  if (pr_fsio_ftruncate(fh, 0) < 0) {
    xerrno = errno;

    pr_ctrls_add_response(ctrl,
      "error truncating DelayTable '%s': %s", fh->fh_path, strerror(xerrno));
    pr_fsio_close(fh);

    errno = xerrno;
    return -1;
  }

  lock.l_type = F_UNLCK;
  if (fcntl(fh->fh_fd, F_SETLK, &lock) < 0) {
    pr_trace_msg(trace_channel, 3,
      "error unlocking fd %d: %s", fh->fh_fd, strerror(errno));
  }

  if (pr_fsio_close(fh) < 0) {
    xerrno = errno;

    pr_ctrls_add_response(ctrl,
      "error closing DelayTable '%s': %s", delay_tab.dt_path,
      strerror(xerrno));

    errno = xerrno;
    return -1;
  }

  pr_ctrls_add_response(ctrl, "DelayTable '%s' reset", delay_tab.dt_path);
  return 0;
}

static int delay_handle_delay(pr_ctrls_t *ctrl, int reqargc,
    char **reqargv) {

  if (delay_tab.dt_enabled == FALSE) {
    pr_ctrls_add_response(ctrl, "delay: DelayTable disabled");
    return -1;
  }

  if (reqargc == 0 ||
      reqargv == NULL) {
    pr_ctrls_add_response(ctrl, "delay: missing required parameters");
    return -1;
  }

  if (strcmp(reqargv[0], "info") == 0) {

    if (!pr_ctrls_check_acl(ctrl, delay_acttab, "info")) {
      pr_ctrls_add_response(ctrl, "access denied");
      return -1;
    }

    return delay_handle_info(ctrl, --reqargc, ++reqargv);

  } else if (strcmp(reqargv[0], "reset") == 0) {

    if (!pr_ctrls_check_acl(ctrl, delay_acttab, "reset")) {
      pr_ctrls_add_response(ctrl, "access denied");
      return -1;
    }

    return delay_handle_reset(ctrl, --reqargc, ++reqargv);
  }

  pr_ctrls_add_response(ctrl, "unknown delay action: '%s'", reqargv[0]);
  return -1;
}

#endif /* PR_USE_CTRLS */

/* Configuration handlers
 */

/* usage: DelayControlsACLs actions|all allow|deny user|group list */
MODRET set_delayctrlsacls(cmd_rec *cmd) {
#if defined(PR_USE_CTRLS)
  char *bad_action = NULL, **actions = NULL;

  CHECK_ARGS(cmd, 4);
  CHECK_CONF(cmd, CONF_ROOT);

  actions = ctrls_parse_acl(cmd->tmp_pool, cmd->argv[1]);

  /* Check the second parameter to make sure it is "allow" or "deny" */
  if (strcmp(cmd->argv[2], "allow") != 0 &&
      strcmp(cmd->argv[2], "deny") != 0)
    CONF_ERROR(cmd, "second parameter must be 'allow' or 'deny'");

  /* Check the third parameter to make sure it is "user" or "group" */
  if (strcmp(cmd->argv[3], "user") != 0 &&
      strcmp(cmd->argv[3], "group") != 0)
    CONF_ERROR(cmd, "third parameter must be 'user' or 'group'");

  bad_action = pr_ctrls_set_module_acls(delay_acttab, delay_pool, actions,
    cmd->argv[2], cmd->argv[3], cmd->argv[4]);
  if (bad_action != NULL)
    CONF_ERROR(cmd, pstrcat(cmd->tmp_pool, ": unknown delay action: '",
      bad_action, "'", NULL));

  return PR_HANDLED(cmd);
#else
  CONF_ERROR(cmd, "requires Controls support (--enable-ctrls)")
#endif /* PR_USE_CTRLS */
}

/* usage: DelayEngine on|off */
MODRET set_delayengine(cmd_rec *cmd) {
  config_rec *c;
  int bool;

  CHECK_ARGS(cmd, 1);
  CHECK_CONF(cmd, CONF_ROOT|CONF_VIRTUAL|CONF_GLOBAL);

  bool = get_boolean(cmd, 1);
  if (bool == -1)
    CONF_ERROR(cmd, "expected Boolean parameter");

  c = add_config_param(cmd->argv[0], 1, NULL);
  c->argv[0] = pcalloc(c->pool, sizeof(unsigned int));
  *((unsigned int *) c->argv[0]) = bool;

  return PR_HANDLED(cmd);
}

/* usage: DelayOnEvent event delay-millis */
MODRET set_delayonevent(cmd_rec *cmd) {
  config_rec *c;
  long delay_ms = -1;
  int event;

  CHECK_ARGS(cmd, 2);
  CHECK_CONF(cmd, CONF_ROOT|CONF_VIRTUAL|CONF_GLOBAL);

  if (strcmp(cmd->argv[1], "USER") == 0) {
    event = DELAY_EVENT_USER_CMD;

  } else if (strcmp(cmd->argv[1], "PASS") == 0) {
    event = DELAY_EVENT_PASS_CMD;

  } else if (strcmp(cmd->argv[1], "FailedLogin") == 0) {
    event = DELAY_EVENT_FAILED_LOGIN;

  } else {
    CONF_ERROR(cmd, pstrcat(cmd->tmp_pool, "unknown/unsupported event: ",
      cmd->argv[1], NULL));
  }

  if (delay_str_get_duration_ms(cmd->argv[2], &delay_ms) < 0) {
    CONF_ERROR(cmd, pstrcat(cmd->tmp_pool, "error parsing delay parameter '",
      cmd->argv[2], "': ", strerror(errno), NULL));
  }

  c = add_config_param(cmd->argv[0], 2, NULL, NULL);
  c->argv[0] = palloc(c->pool, sizeof(int));
  *((int *) c->argv[0]) = event;
  c->argv[1] = palloc(c->pool, sizeof(unsigned long));

  /* Note: Even though we parsed the delay parameter in millisec, we
   * need to use microsecs internally, as that is the implemented interface.
   */
  *((unsigned long *) c->argv[1]) = (delay_ms * 1000);

  return PR_HANDLED(cmd);
}

/* usage: DelayTable path|"none" */
MODRET set_delaytable(cmd_rec *cmd) {
  const char *table = NULL;

  CHECK_ARGS(cmd, 1);
  CHECK_CONF(cmd, CONF_ROOT);

  if (pr_fs_valid_path(cmd->argv[1]) < 0) {
    if (strcasecmp(cmd->argv[1], "none") != 0) {
      CONF_ERROR(cmd, "must be an absolute path");
    }

  } else {
    table = cmd->argv[1];
  }

  add_config_param_str(cmd->argv[0], 1, table);
  return PR_HANDLED(cmd);
}

/* Command handlers
 */

MODRET delay_log_pass(cmd_rec *cmd) {
  if (delay_engine == FALSE) {
    return PR_DECLINED(cmd);
  }

  if (delay_pass_min_delay > 0) {
    unsigned long interval = 0L;

    if (delay_pass_delayed < delay_pass_min_delay) {
      interval = delay_pass_min_delay - delay_pass_delayed;
    }

    if (interval > 0) {
      pr_trace_msg(trace_channel, 9,
        "enforcing minimum PASS delay (%lu usec), adding %ld usec delay",
        delay_pass_min_delay, interval);
      delay_delay(interval);
    }
  }

  return PR_DECLINED(cmd);
}

MODRET delay_log_pass_err(cmd_rec *cmd) {
  if (delay_engine == FALSE) { 
    return PR_DECLINED(cmd);
  }
  
  if (delay_failed_login_min_delay > 0 ||
      delay_pass_min_delay > 0) {
    unsigned long interval = 0L, min_delay;

    min_delay = delay_failed_login_min_delay;
    if (delay_pass_min_delay > min_delay) {
      min_delay = delay_pass_min_delay;
    }
      
    if (delay_pass_delayed < min_delay) {
      interval = min_delay - delay_pass_delayed;
    }

    if (interval > 0) {
      pr_trace_msg(trace_channel, 9,
        "enforcing minimum failed login delay (%lu usec), adding %ld usec "
        "delay", delay_failed_login_min_delay, interval);
      delay_delay(interval);
    }
  }

  return PR_DECLINED(cmd);
}

MODRET delay_log_user(cmd_rec *cmd) {
  if (delay_engine == FALSE) { 
    return PR_DECLINED(cmd);
  }

  if (delay_user_min_delay > 0) {
    long interval = 0L;

    if (delay_user_delayed < delay_user_min_delay) {
      interval = delay_user_min_delay - delay_user_delayed;
    }

    if (interval > 0) {
      pr_trace_msg(trace_channel, 9,
        "enforcing minimum USER delay (%lu usec), adding %ld usec delay",
        delay_user_min_delay, interval);
      delay_delay(interval);
    }
  }

  return PR_DECLINED(cmd);
}

MODRET delay_post_pass(cmd_rec *cmd) {
  struct timeval tv;
  unsigned int rownum;
  long interval, median;
  const char *proto;
  unsigned char *authenticated;

  if (delay_engine == FALSE ||
      delay_tab.dt_enabled == FALSE) {
    return PR_DECLINED(cmd);
  }

  /* Has the client already authenticated? */
  authenticated = get_param_ptr(cmd->server->conf, "authenticated", FALSE);
  if (authenticated != NULL &&
      *authenticated == TRUE) {
    return PR_DECLINED(cmd);
  }

  rownum = delay_get_pass_rownum(main_server->sid);

  /* Prepare for manipulating the table. */
  if (delay_table_load(FALSE) < 0) {
    int xerrno = errno;

    pr_log_pri(PR_LOG_WARNING, MOD_DELAY_VERSION
      ": unable to load DelayTable '%s' (fd %d) into memory: %s",
      delay_tab.dt_path, delay_tab.dt_fd, strerror(xerrno));
    pr_trace_msg(trace_channel, 1,
      "unable to load DelayTable '%s' (fd %d) into memory: %s",
      delay_tab.dt_path, delay_tab.dt_fd, strerror(xerrno));

    errno = xerrno;
    return PR_DECLINED(cmd);
  }

  memset(&tv, 0, sizeof(tv));
  gettimeofday(&tv, NULL);

  delay_table_wlock(rownum);

  interval = (tv.tv_sec - delay_tv.tv_sec) * 1000000 +
    (tv.tv_usec - delay_tv.tv_usec);
  pr_trace_msg(trace_channel, 9,
    "interval between USER and PASS commands: %ld usecs", interval);

  proto = pr_session_get_protocol(0);

  /* Get the median interval value. */
  median = delay_get_median(cmd->tmp_pool, rownum, proto, interval);

  /* Add the interval to the table. Only allow a single session to
   * add a portion of the cache size, to prevent a single client from
   * poisoning the cache.
   */
  if (delay_npass < (DELAY_NVALUES / DELAY_SESS_NVALUES)) {
    pr_trace_msg(trace_channel, 8, "adding %ld usecs to PASS row", interval);
    delay_table_add_interval(rownum, proto, interval);
    delay_npass++;

  } else {
    /* Generate an event, in case a module (i.e. mod_ban) might want
     * to do something appropriate to such an ill-behaved client.
     */
    pr_event_generate("mod_delay.max-pass", session.c);
  }

  /* Done with the table. */
  delay_table_unlock(rownum);
  if (delay_table_unload(FALSE) < 0) {
    pr_log_pri(PR_LOG_WARNING, MOD_DELAY_VERSION
      ": unable to unload DelayTable '%s' from memory: %s",
      delay_tab.dt_path, strerror(errno));
  }

  /* If this is a POST_CMD phase, then close the table.  If the phase is
   * POST_CMD_ERR, then leave the table open; the client may send another
   * set of USER/PASS commands.
   */
  if (session.curr_phase == POST_CMD) {
    (void) close(delay_tab.dt_fd);
    delay_tab.dt_fd = -1;
  }

  /* If the current interval is less than the median interval (and a valid
   * median interval was selected), we need to delay ourselves a little.
   */
  if (median >= 0) {
    if (interval < median) {
      pr_trace_msg(trace_channel, 9,
        "interval (%ld usecs) less than selected median (%ld usecs), delaying",
        interval, median);
      delay_pass_delayed = delay_delay_with_jitter(median - interval);
    }

  } else {
    pr_trace_msg(trace_channel, 9,
      "invalid median value (%ld usecs) selected, ignoring", median);
  }

  return PR_DECLINED(cmd);
}

MODRET delay_pre_pass(cmd_rec *cmd) {
  if (delay_engine == FALSE) {
    return PR_DECLINED(cmd);
  }

  /* Always reset the USER delayed value. */
  delay_pass_delayed = 0L;

  gettimeofday(&delay_tv, NULL);
  return PR_DECLINED(cmd);
}

MODRET delay_post_user(cmd_rec *cmd) {
  struct timeval tv;
  unsigned int rownum;
  long interval = 0L, median = 0L;
  const char *proto;
  unsigned char *authenticated;

  if (delay_engine == FALSE ||
      delay_tab.dt_enabled == FALSE) {
    return PR_DECLINED(cmd);
  }

  /* Has the client already authenticated? */
  authenticated = get_param_ptr(cmd->server->conf, "authenticated", FALSE);
  if (authenticated != NULL &&
      *authenticated == TRUE) {
    return PR_DECLINED(cmd);
  }
 
  rownum = delay_get_user_rownum(main_server->sid);

  /* Prepare for manipulating the table. */
  if (delay_table_load(FALSE) < 0) {
    int xerrno = errno;

    pr_log_pri(PR_LOG_WARNING, MOD_DELAY_VERSION
      ": unable to load DelayTable '%s' (fd %d) into memory: %s",
      delay_tab.dt_path, delay_tab.dt_fd, strerror(xerrno));
    pr_trace_msg(trace_channel, 1,
      "unable to load DelayTable '%s' (fd %d) into memory: %s",
      delay_tab.dt_path, delay_tab.dt_fd, strerror(xerrno));

    errno = xerrno;
    return PR_DECLINED(cmd);
  }

  memset(&tv, 0, sizeof(tv));
  gettimeofday(&tv, NULL);

  delay_table_wlock(rownum);

  interval = (tv.tv_sec - delay_tv.tv_sec) * 1000000 +
    (tv.tv_usec - delay_tv.tv_usec);

  /* There can conceivably be quite a bit of time between connect and USER,
   * e.g. for TLS handshakes, DNS lookups, user latency, etc.  Thus we put
   * a bound on this interval at 60 seconds.  For the most part, this will
   * not affect the selected median value -- expect when the DelayTable
   * is empty, and this is the only value present.
   */
  if (interval > DELAY_MAX_CONNECT_INTERVAL_USECS) {
    interval = DELAY_MAX_CONNECT_INTERVAL_USECS;
  }
 
  pr_trace_msg(trace_channel, 9,
    "interval between connect and USER command: %ld usecs", interval);

  proto = pr_session_get_protocol(0);

  /* Get the median interval value. */
  median = delay_get_median(cmd->tmp_pool, rownum, proto, interval);

  /* Add the interval to the table. Only allow a single session to
   * add a portion of the cache size, to prevent a single client from
   * poisoning the cache.
   */
  if (delay_nuser < (DELAY_NVALUES / DELAY_SESS_NVALUES)) {
    pr_trace_msg(trace_channel, 8, "adding %ld usecs to USER row", interval);
    delay_table_add_interval(rownum, proto, interval);
    delay_nuser++;

  } else {
    /* Generate an event, in case a module (i.e. mod_ban) might want
     * to do something appropriate to such an ill-behaved client.
     */
    pr_event_generate("mod_delay.max-user", session.c);
  }

  /* Done with the table. */
  delay_table_unlock(rownum);
  if (delay_table_unload(FALSE) < 0) {
    pr_log_pri(PR_LOG_WARNING, MOD_DELAY_VERSION
      ": unable to unload DelayTable '%s' from memory: %s",
      delay_tab.dt_path, strerror(errno));
  }

  /* If the current interval is less than the median interval (and a valid
   * median interval was selected), we need to delay ourselves a little.
   */
  if (median >= 0) {
    if (interval < median) {
      pr_trace_msg(trace_channel, 9,
        "interval (%ld usecs) less than selected median (%ld usecs), delaying",
        interval, median);
      delay_user_delayed = delay_delay_with_jitter(median - interval);
    }

  } else {
    pr_trace_msg(trace_channel, 9,
      "invalid median value (%ld usecs) selected, ignoring", median);
  }

  return PR_DECLINED(cmd);
}

MODRET delay_pre_user(cmd_rec *cmd) {
  if (delay_engine == FALSE) {
    return PR_DECLINED(cmd);
  }

  /* Always reset the USER delayed value. */
  delay_user_delayed = 0L;

  gettimeofday(&delay_tv, NULL);
  return PR_DECLINED(cmd);
}

/* Event handlers
 */

#if defined(PR_SHARED_MODULE)
static void delay_mod_unload_ev(const void *event_data, void *user_data) {
  if (strcmp("mod_delay.c", (const char *) event_data) == 0) {
    /* Unregister ourselves from all events. */
    pr_event_unregister(&delay_module, NULL, NULL);

# ifdef PR_USE_CTRLS
    pr_ctrls_unregister(&delay_module, "delay");
# endif

  }
}
#endif

static void delay_postparse_ev(const void *event_data, void *user_data) {
  config_rec *c;

  c = find_config(main_server->conf, CONF_PARAM, "DelayEngine", FALSE);
  if (c != NULL &&
      *((unsigned int *) c->argv[0]) == FALSE) {
    delay_engine = FALSE;
  }

  if (delay_engine == FALSE) {
    return;
  }

  delay_tab.dt_enabled = FALSE;

  c = find_config(main_server->conf, CONF_PARAM, "DelayTable", FALSE);
  if (c != NULL) {
    const char *table = NULL;

    table = c->argv[0];
    if (table != NULL) {
      delay_tab.dt_enabled = TRUE;
      delay_tab.dt_path = table;
    }
  }

  if (delay_tab.dt_enabled) {
    (void) delay_table_init();
  }
}

static void delay_restart_ev(const void *event_data, void *user_data) {
#if defined(PR_USE_CTRLS)
    register unsigned int i;
#endif /* PR_USE_CTRLS */

  delay_tab.dt_path = PR_RUN_DIR "/proftpd.delay";
  delay_tab.dt_data = NULL;
  delay_tab.dt_enabled = TRUE;

  if (delay_pool) {
    destroy_pool(delay_pool);
  }

  delay_pool = make_sub_pool(permanent_pool);
  pr_pool_tag(delay_pool, MOD_DELAY_VERSION);

#if defined(PR_USE_CTRLS)
  for (i = 0; delay_acttab[i].act_action; i++) {
    delay_acttab[i].act_acl = pcalloc(delay_pool, sizeof(ctrls_acl_t));
    pr_ctrls_init_acl(delay_acttab[i].act_acl);
  }
#endif /* PR_USE_CTRLS */
}

static void delay_sess_reinit_ev(const void *event_data, void *user_data) {
  int res;

  /* A HOST command changed the main_server pointer, reinitialize ourselves. */

  pr_event_unregister(&delay_module, "core.session-reinit",
    delay_sess_reinit_ev);

  delay_engine = TRUE;

  if (delay_tab.dt_fd > 0) {
    close(delay_tab.dt_fd);
    delay_tab.dt_fd = -1;
  }

  delay_nuser = 0;
  delay_npass = 0;

  res = delay_sess_init();
  if (res < 0) {
    pr_session_disconnect(&delay_module,
      PR_SESS_DISCONNECT_SESSION_INIT_FAILED, NULL);
  }
}

static void delay_shutdown_ev(const void *event_data, void *user_data) {
  pr_fh_t *fh = NULL;
  char *data = NULL;
  size_t datalen = 0;
  int xerrno = 0;

  if (delay_engine == FALSE ||
      delay_tab.dt_enabled == FALSE) {
    return;
  }

  /* Write out the DelayTable to the filesystem, thus updating the
   * file metadata.
   */

  PRIVS_ROOT
  fh = pr_fsio_open(delay_tab.dt_path, O_RDWR);
  xerrno = errno;
  PRIVS_RELINQUISH

  if (fh == NULL) {
    pr_log_pri(PR_LOG_WARNING, MOD_DELAY_VERSION
      ": unable to open DelayTable '%s': %s", delay_tab.dt_path,
      strerror(xerrno));
    errno = xerrno;
    return;
  }

  delay_tab.dt_fd = fh->fh_fd;
  delay_tab.dt_data = NULL;

  if (delay_table_load(TRUE) < 0) {
    xerrno = errno;
    pr_fsio_close(fh);

    pr_log_pri(PR_LOG_WARNING, MOD_DELAY_VERSION
      ": unable to load DelayTable '%s' (fd %d) into memory: %s",
      delay_tab.dt_path, delay_tab.dt_fd, strerror(xerrno));
    pr_trace_msg(trace_channel, 1,
      "unable to load DelayTable '%s' (fd %d) into memory: %s",
      delay_tab.dt_path, delay_tab.dt_fd, strerror(xerrno));
    
    errno = xerrno;
    return;
  }

  datalen = delay_tab.dt_size;
  data = palloc(delay_pool, datalen);
  if (data != NULL &&
      datalen > 0) {
    memcpy(data, delay_tab.dt_data, datalen);
  }

  if (delay_table_unload(TRUE) < 0) {
    pr_log_pri(PR_LOG_WARNING, MOD_DELAY_VERSION
      ": error unloading DelayTable '%s' from memory: %s",
      delay_tab.dt_path, strerror(errno));
  }

  if (data != NULL &&
      datalen > 0) {
    if (pr_fsio_write(fh, data, datalen) < 0) {
      pr_log_pri(PR_LOG_WARNING, MOD_DELAY_VERSION
        ": error updating DelayTable '%s': %s", delay_tab.dt_path,
        strerror(errno));
    }
  }

  delay_tab.dt_fd = -1;
  if (pr_fsio_close(fh) < 0) {
    pr_log_pri(PR_LOG_WARNING, MOD_DELAY_VERSION
      ": error writing DelayTable '%s': %s", delay_tab.dt_path,
      strerror(errno));
  }
}

/* Initialization functions
 */

static int delay_init(void) {
  delay_tab.dt_path = PR_RUN_DIR "/proftpd.delay";
  delay_tab.dt_data = NULL;

#if defined(PR_SHARED_MODULE)
  pr_event_register(&delay_module, "core.module-unload", delay_mod_unload_ev,
    NULL);
#endif
  pr_event_register(&delay_module, "core.postparse", delay_postparse_ev, NULL);
  pr_event_register(&delay_module, "core.restart", delay_restart_ev, NULL);
  pr_event_register(&delay_module, "core.shutdown", delay_shutdown_ev, NULL);

  delay_pool = make_sub_pool(permanent_pool);
  pr_pool_tag(delay_pool, MOD_DELAY_VERSION);

#if defined(PR_USE_CTRLS)
  if (pr_ctrls_register(&delay_module, "delay", "tune mod_delay settings",
      delay_handle_delay) < 0) {
    pr_log_pri(PR_LOG_NOTICE, MOD_DELAY_VERSION
      ": error registering 'delay' control: %s", strerror(errno));

  } else {
    register unsigned int i;

    for (i = 0; delay_acttab[i].act_action; i++) {
      delay_acttab[i].act_acl = pcalloc(delay_pool, sizeof(ctrls_acl_t));
      pr_ctrls_init_acl(delay_acttab[i].act_acl);
    }
  }
#endif /* PR_USE_CTRLS */

  return 0;
}

static int delay_sess_init(void) {
  pr_fh_t *fh;
  config_rec *c;
  int xerrno;

  pr_event_register(&delay_module, "core.session-reinit", delay_sess_reinit_ev,
    NULL);

  if (delay_engine == FALSE) {
    return 0;
  }

  /* Look up DelayEngine again, as it may have been disabled in an
   * <IfClass> section.
   */
  c = find_config(main_server->conf, CONF_PARAM, "DelayEngine", FALSE);
  if (c != NULL &&
      *((unsigned int *) c->argv[0]) == FALSE) {
    delay_engine = FALSE;
  }

  if (delay_engine == FALSE) {
    return 0;
  }

  c = find_config(main_server->conf, CONF_PARAM, "DelayOnEvent", FALSE);
  while (c != NULL) {
    int event;
    unsigned long delay_usec;

    pr_signals_handle();

    event = *((int *) c->argv[0]);
    delay_usec = *((unsigned long *) c->argv[1]);

    switch (event) {
      case DELAY_EVENT_USER_CMD:
        delay_user_min_delay = delay_usec;
        break;

      case DELAY_EVENT_PASS_CMD:
        delay_pass_min_delay = delay_usec;
        break;

      case DELAY_EVENT_FAILED_LOGIN:
        delay_failed_login_min_delay = delay_usec;
        break;
    }

    c = find_config_next(c, c->next, CONF_PARAM, "DelayOnEvent", FALSE);
  }

  if (delay_tab.dt_enabled == FALSE) {
    /* If the DelayTable has been disabled (but not DelayEngine), AND there
     * are not DelayOnEvent rules set, log a warning since mod_delay will not
     * be doing much; it's probably an unintentional misconfiguration.
     */

    pr_log_debug(DEBUG0, MOD_DELAY_VERSION
      ": no DelayOnEvent rules configured with \"DelayTable none\" in effect, "
      "disabling module");
    return 0;
  }

  delay_nuser = 0;
  delay_npass = 0;

  pr_trace_msg(trace_channel, 6, "opening DelayTable '%s'", delay_tab.dt_path);

  PRIVS_ROOT
  fh = pr_fsio_open(delay_tab.dt_path, O_RDWR);
  xerrno = errno;
  PRIVS_RELINQUISH

  if (fh == NULL) {
    pr_log_pri(PR_LOG_WARNING, MOD_DELAY_VERSION
      ": unable to open DelayTable '%s': %s", delay_tab.dt_path,
      strerror(xerrno));
    pr_trace_msg(trace_channel, 1, "unable to open DelayTable '%s': %s",
      delay_tab.dt_path, strerror(xerrno));
    delay_engine = FALSE;
    return 0;
  }

  /* Find a usable fd for the just-opened DelayTable fd. */
  if (pr_fs_get_usable_fd2(&(fh->fh_fd)) < 0) {
    pr_log_debug(DEBUG0, MOD_DELAY_VERSION
      ": warning: unable to find good fd for DelayTable %d: %s",
      fh->fh_fd, strerror(errno));
  }

  /* Set the close-on-exec flag, for safety. */
  if (fcntl(fh->fh_fd, F_SETFD, FD_CLOEXEC) < 0) {
    pr_log_pri(PR_LOG_WARNING, MOD_DELAY_VERSION
      ": unable to set CLO_EXEC on DelayTable fd %d: %s", fh->fh_fd,
      strerror(errno));
  }

  delay_tab.dt_fd = fh->fh_fd;
  delay_tab.dt_data = NULL;

  return 0;  
}

/* Module API tables
 */

#if defined(PR_USE_CTRLS)
static ctrls_acttab_t delay_acttab[] = {
  { "info",	NULL, NULL, NULL },
  { "reset",	NULL, NULL, NULL },
  { NULL,	NULL, NULL, NULL }
};
#endif /* PR_USE_CTRLS */

static conftable delay_conftab[] = {
  { "DelayControlsACLs",set_delayctrlsacls,	NULL },
  { "DelayEngine",	set_delayengine,	NULL },
  { "DelayOnEvent",	set_delayonevent,	NULL },
  { "DelayTable",	set_delaytable,		NULL },
  { NULL }
};

static cmdtable delay_cmdtab[] = {
  { PRE_CMD,		C_PASS,	G_NONE,	delay_pre_pass,		FALSE, FALSE },
  { POST_CMD,		C_PASS,	G_NONE,	delay_post_pass,	FALSE, FALSE },
  { POST_CMD_ERR,	C_PASS,	G_NONE,	delay_post_pass,	FALSE, FALSE },
  { PRE_CMD,		C_USER,	G_NONE,	delay_pre_user,		FALSE, FALSE },
  { POST_CMD,		C_USER,	G_NONE,	delay_post_user,	FALSE, FALSE },
  { POST_CMD_ERR,	C_USER,	G_NONE,	delay_post_user,	FALSE, FALSE },
  { LOG_CMD,		C_USER,	G_NONE,	delay_log_user,		FALSE, FALSE },
  { LOG_CMD_ERR,	C_USER,	G_NONE,	delay_log_user,		FALSE, FALSE },
  { LOG_CMD,		C_PASS,	G_NONE,	delay_log_pass,		FALSE, FALSE },
  { LOG_CMD_ERR,	C_PASS,	G_NONE,	delay_log_pass_err,	FALSE, FALSE },
  { 0, NULL }
};

module delay_module = {
  NULL, NULL,

  /* Module API version 2.0 */
  0x20,

  /* Module name */
  "delay",

  /* Module configuration handler table */
  delay_conftab,

  /* Module command handler table */
  delay_cmdtab,

  /* Module authentication handler table */
  NULL,

  /* Module initialization function */
  delay_init,

  /* Session initialization function */
  delay_sess_init,

  /* Module version */
  MOD_DELAY_VERSION
};
