/src/ntp-dev/ntpd/ntp_leapsec.c

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/*
 * ntp_leapsec.c - leap second processing for NTPD
 *
 * Written by Juergen Perlinger (perlinger@ntp.org) for the NTP project.
 * The contents of 'html/copyright.html' apply.
 * ----------------------------------------------------------------------
 * This is an attempt to get the leap second handling into a dedicated
 * module to make the somewhat convoluted logic testable.
 */

#include <config.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <ctype.h>

#include "ntp_types.h"
#include "ntp_fp.h"
#include "ntp_stdlib.h"
#include "ntp_calendar.h"
#include "ntp_leapsec.h"
#include "ntp.h"
#include "vint64ops.h"
#include "lib_strbuf.h"

#include "isc/sha1.h"

static const char * const logPrefix = "leapsecond file";

/* ---------------------------------------------------------------------
 * GCC is rather sticky with its 'const' attribute. We have to do it more
 * explicit than with a cast if we want to get rid of a CONST qualifier.
 * Greetings from the PASCAL world, where casting was only possible via
 * untagged unions...
 */
static inline void*
noconst(
  const void* ptr
  )
{
  union {
    const void * cp;
    void *       vp;
  } tmp;
  tmp.cp = ptr;
  return tmp.vp;
}

/* ---------------------------------------------------------------------
 * Our internal data structure
 */
#define MAX_HIST 10  /* history of leap seconds */

struct leap_info {
  vint64   ttime; /* transition time (after the step, ntp scale) */
  uint32_t stime; /* schedule limit (a month before transition)  */
  int16_t  taiof; /* TAI offset on and after the transition      */
  uint8_t  dynls; /* dynamic: inserted on peer/clock request     */
};
typedef struct leap_info leap_info_t;

struct leap_head {
  vint64   update; /* time of information update                 */
  vint64   expire; /* table expiration time                      */
  uint16_t size;   /* number of infos in table                 */
  int16_t  base_tai;  /* total leaps before first entry      */
  int16_t  this_tai;  /* current TAI offset                */
  int16_t  next_tai;  /* TAI offset after 'when'             */
  vint64   dtime;  /* due time (current era end)                 */
  vint64   ttime;  /* nominal transition time (next era start)   */
  vint64   stime;  /* schedule time (when we take notice)        */
  vint64   ebase;  /* base time of this leap era                 */
  uint8_t  dynls;  /* next leap is dynamic (by peer request)     */
};
typedef struct leap_head leap_head_t;

struct leap_table {
  leap_signature_t lsig;
  leap_head_t  head;
  leap_info_t    info[MAX_HIST];
};

/* Where we store our tables */
static leap_table_t _ltab[2], *_lptr;
static int/*BOOL*/  _electric;

/* Forward decls of local helpers */
static int    add_range(leap_table_t*, const leap_info_t*);
static char * get_line(leapsec_reader, void*, char*, size_t);
static char * skipws(const char*);
static int    parsefail(const char * cp, const char * ep);
static void   reload_limits(leap_table_t*, const vint64*);
static void   fetch_leap_era(leap_era_t*, const leap_table_t*,
           const vint64*);
static int    betweenu32(uint32_t, uint32_t, uint32_t);
static void   reset_times(leap_table_t*);
static int    leapsec_add(leap_table_t*, const vint64*, int);
static int    leapsec_raw(leap_table_t*, const vint64 *, int, int);
static const char * lstostr(const vint64 * ts);

/* =====================================================================
 * Get & Set the current leap table
 */

/* ------------------------------------------------------------------ */
leap_table_t *
leapsec_get_table(
  int alternate)
{
  leap_table_t *p1, *p2;

  p1 = _lptr;
  if (p1 == &_ltab[0]) {
    p2 = &_ltab[1];
  } else if (p1 == &_ltab[1]) {
    p2 = &_ltab[0];
  } else {
    p1 = &_ltab[0];
    p2 = &_ltab[1];
    reset_times(p1);
    reset_times(p2);
    _lptr = p1;
  }
  if (alternate) {
    memcpy(p2, p1, sizeof(leap_table_t));
    p1 = p2;
  }

  return p1;
}

/* ------------------------------------------------------------------ */
int/*BOOL*/
leapsec_set_table(
  leap_table_t * pt)
{
  if (pt == &_ltab[0] || pt == &_ltab[1])
    _lptr = pt;
  return _lptr == pt;
}

/* ------------------------------------------------------------------ */
int/*BOOL*/
leapsec_electric(
  int/*BOOL*/ on)
{
  int res = _electric;
  if (on < 0)
    return res;

  _electric = (on != 0);
  if (_electric == res)
    return res;

  if (_lptr == &_ltab[0] || _lptr == &_ltab[1])
    reset_times(_lptr);

  return res;
}

/* =====================================================================
 * API functions that operate on tables
 */

/* ---------------------------------------------------------------------
 * Clear all leap second data. Use it for init & cleanup
 */
void
leapsec_clear(
  leap_table_t * pt)
{
  memset(&pt->lsig, 0, sizeof(pt->lsig));
  memset(&pt->head, 0, sizeof(pt->head));
  reset_times(pt);
}

/* ---------------------------------------------------------------------
 * Load a leap second file and check expiration on the go
 */
int/*BOOL*/
leapsec_load(
  leap_table_t * pt  ,
  leapsec_reader func,
  void *         farg,
  int            use_build_limit)
{
  char   *cp, *ep, linebuf[50];
  vint64 ttime, limit;
  long   taiof;
  struct calendar build;

  leapsec_clear(pt);
  if (use_build_limit && ntpcal_get_build_date(&build)) {
    /* don't prune everything -- permit the last 10yrs
     * before build.
     */
    build.year -= 10;
    limit = ntpcal_date_to_ntp64(&build);
  } else {
    memset(&limit, 0, sizeof(limit));
  }

  while (get_line(func, farg, linebuf, sizeof(linebuf))) {
    cp = linebuf;
    if (*cp == '#') {
      cp++;
      if (*cp == '@') {
        cp = skipws(cp+1);
        pt->head.expire = strtouv64(cp, &ep, 10);
        if (parsefail(cp, ep))
          goto fail_read;
        pt->lsig.etime = pt->head.expire.D_s.lo;
      } else if (*cp == '$') {
        cp = skipws(cp+1);
        pt->head.update = strtouv64(cp, &ep, 10);
        if (parsefail(cp, ep))
          goto fail_read;
      }
    } else if (isdigit((u_char)*cp)) {
      ttime = strtouv64(cp, &ep, 10);
      if (parsefail(cp, ep))
        goto fail_read;
      cp = skipws(ep);
      taiof = strtol(cp, &ep, 10);
      if (   parsefail(cp, ep)
          || taiof > SHRT_MAX || taiof < SHRT_MIN)
        goto fail_read;
      if (ucmpv64(&ttime, &limit) >= 0) {
        if (!leapsec_raw(pt, &ttime,
             taiof, FALSE))
          goto fail_insn;
      } else {
        pt->head.base_tai = (int16_t)taiof;
      }
      pt->lsig.ttime = ttime.D_s.lo;
      pt->lsig.taiof = (int16_t)taiof;
    }
  }
  return TRUE;

fail_read:
  errno = EILSEQ;
fail_insn:
  leapsec_clear(pt);
  return FALSE;
}

/* ---------------------------------------------------------------------
 * Dump a table in human-readable format. Use 'fprintf' and a FILE
 * pointer if you want to get it printed into a stream.
 */
void
leapsec_dump(
  const leap_table_t * pt  ,
  leapsec_dumper       func,
  void *               farg)
{
  int             idx;
  vint64          ts;
  struct calendar atb, ttb;

  ntpcal_ntp64_to_date(&ttb, &pt->head.expire);
  (*func)(farg, "leap table (%u entries) expires at %04u-%02u-%02u:\n",
    pt->head.size,
    ttb.year, ttb.month, ttb.monthday);
  idx = pt->head.size;
  while (idx-- != 0) {
    ts = pt->info[idx].ttime;
    ntpcal_ntp64_to_date(&ttb, &ts);
    ts = subv64u32(&ts, pt->info[idx].stime);
    ntpcal_ntp64_to_date(&atb, &ts);

    (*func)(farg, "%04u-%02u-%02u [%c] (%04u-%02u-%02u) - %d\n",
      ttb.year, ttb.month, ttb.monthday,
      "-*"[pt->info[idx].dynls != 0],
      atb.year, atb.month, atb.monthday,
      pt->info[idx].taiof);
  }
}

/* =====================================================================
 * usecase driven API functions
 */

int/*BOOL*/
leapsec_query(
  leap_result_t * qr   ,
  uint32_t        ts32 ,
  const time_t *  pivot)
{
  leap_table_t *   pt;
  vint64           ts64, last, next;
  uint32_t         due32;
  int              fired;

  /* preset things we use later on... */
  fired = FALSE;
  ts64  = ntpcal_ntp_to_ntp(ts32, pivot);
  pt    = leapsec_get_table(FALSE);
  memset(qr, 0, sizeof(leap_result_t));

  if (ucmpv64(&ts64, &pt->head.ebase) < 0) {
    /* Most likely after leap frame reset. Could also be a
     * backstep of the system clock. Anyway, get the new
     * leap era frame.
     */
    reload_limits(pt, &ts64);
  } else if (ucmpv64(&ts64, &pt->head.dtime) >= 0) {
    /* Boundary crossed in forward direction. This might
     * indicate a leap transition, so we prepare for that
     * case.
     *
     * Some operations below are actually NOPs in electric
     * mode, but having only one code path that works for
     * both modes is easier to maintain.
     *
     * There's another quirk we must keep looking out for:
     * If we just stepped the clock, the step might have
     * crossed a leap boundary. As with backward steps, we
     * do not want to raise the 'fired' event in that case.
     * So we raise the 'fired' event only if we're close to
     * the transition and just reload the limits otherwise.
     */
    last = addv64i32(&pt->head.dtime, 3); /* get boundary */
    if (ucmpv64(&ts64, &last) >= 0) {
      /* that was likely a query after a step */
      reload_limits(pt, &ts64);
    } else {
      /* close enough for deeper examination */
      last = pt->head.ttime;
      qr->warped = (int16_t)(last.D_s.lo -
                 pt->head.dtime.D_s.lo);
      next = addv64i32(&ts64, qr->warped);
      reload_limits(pt, &next);
      fired = ucmpv64(&pt->head.ebase, &last) == 0;
      if (fired) {
        ts64 = next;
        ts32 = next.D_s.lo;
      } else {
        qr->warped = 0;
      }
    }
  }

  qr->tai_offs = pt->head.this_tai;
  qr->ebase    = pt->head.ebase;
  qr->ttime    = pt->head.ttime;

  /* If before the next scheduling alert, we're done. */
  if (ucmpv64(&ts64, &pt->head.stime) < 0)
    return fired;

  /* now start to collect the remaining data */
  due32 = pt->head.dtime.D_s.lo;

  qr->tai_diff  = pt->head.next_tai - pt->head.this_tai;
  qr->ddist     = due32 - ts32;
  qr->dynamic   = pt->head.dynls;
  qr->proximity = LSPROX_SCHEDULE;

  /* if not in the last day before transition, we're done. */
  if (!betweenu32(due32 - SECSPERDAY, ts32, due32))
    return fired;

  qr->proximity = LSPROX_ANNOUNCE;
  if (!betweenu32(due32 - 10, ts32, due32))
    return fired;

  /* The last 10s before the transition. Prepare for action! */
  qr->proximity = LSPROX_ALERT;
  return fired;
}

/* ------------------------------------------------------------------ */
int/*BOOL*/
leapsec_query_era(
  leap_era_t *   qr   ,
  uint32_t       ntpts,
  const time_t * pivot)
{
  const leap_table_t * pt;
  vint64               ts64;

  pt   = leapsec_get_table(FALSE);
  ts64 = ntpcal_ntp_to_ntp(ntpts, pivot);
  fetch_leap_era(qr, pt, &ts64);
  return TRUE;
}

/* ------------------------------------------------------------------ */
int/*BOOL*/
leapsec_frame(
        leap_result_t *qr)
{
  const leap_table_t * pt;

        memset(qr, 0, sizeof(leap_result_t));
  pt = leapsec_get_table(FALSE);

  qr->tai_offs = pt->head.this_tai;
  qr->tai_diff = pt->head.next_tai - pt->head.this_tai;
  qr->ebase    = pt->head.ebase;
  qr->ttime    = pt->head.ttime;
  qr->dynamic  = pt->head.dynls;

  return ucmpv64(&pt->head.ttime, &pt->head.stime) >= 0;
}

/* ------------------------------------------------------------------ */
/* Reset the current leap frame */
void
leapsec_reset_frame(void)
{
  reset_times(leapsec_get_table(FALSE));
}

/* ------------------------------------------------------------------ */
/* load a file from a FILE pointer. Note: If hcheck is true, load
 * only after successful signature check. The stream must be seekable
 * or this will fail.
 */
int/*BOOL*/
leapsec_load_stream(
  FILE       * ifp  ,
  const char * fname,
  int/*BOOL*/  logall)
{
  leap_table_t *pt;
  int           rcheck;

  if (NULL == fname)
    fname = "<unknown>";

  rcheck = leapsec_validate((leapsec_reader)getc, ifp);
  if (logall)
    switch (rcheck)
    {
    case LSVALID_GOODHASH:
      msyslog(LOG_NOTICE, "%s ('%s'): good hash signature",
        logPrefix, fname);
      break;

    case LSVALID_NOHASH:
      msyslog(LOG_ERR, "%s ('%s'): no hash signature",
        logPrefix, fname);
      break;
    case LSVALID_BADHASH:
      msyslog(LOG_ERR, "%s ('%s'): signature mismatch",
        logPrefix, fname);
      break;
    case LSVALID_BADFORMAT:
      msyslog(LOG_ERR, "%s ('%s'): malformed hash signature",
        logPrefix, fname);
      break;
    default:
      msyslog(LOG_ERR, "%s ('%s'): unknown error code %d",
        logPrefix, fname, rcheck);
      break;
    }
  if (rcheck < 0)
    return FALSE;

  rewind(ifp);
  pt = leapsec_get_table(TRUE);
  if (!leapsec_load(pt, (leapsec_reader)getc, ifp, TRUE)) {
    switch (errno) {
    case EINVAL:
      msyslog(LOG_ERR, "%s ('%s'): bad transition time",
        logPrefix, fname);
      break;
    case ERANGE:
      msyslog(LOG_ERR, "%s ('%s'): times not ascending",
        logPrefix, fname);
      break;
    default:
      msyslog(LOG_ERR, "%s ('%s'): parsing error",
        logPrefix, fname);
      break;
    }
    return FALSE;
  }

  if (pt->head.size)
    msyslog(LOG_NOTICE, "%s ('%s'): loaded, expire=%s last=%s ofs=%d",
      logPrefix, fname, lstostr(&pt->head.expire),
      lstostr(&pt->info[0].ttime), pt->info[0].taiof);
  else
    msyslog(LOG_NOTICE,
      "%s ('%s'): loaded, expire=%s ofs=%d (no entries after build date)",
      logPrefix, fname, lstostr(&pt->head.expire),
      pt->head.base_tai);

  return leapsec_set_table(pt);
}

/* ------------------------------------------------------------------ */
int/*BOOL*/
leapsec_load_file(
  const char  * fname,
  struct stat * sb_old,
  int/*BOOL*/   force,
  int/*BOOL*/   logall)
{
  FILE       * fp;
  struct stat  sb_new;
  int          rc;

  /* just do nothing if there is no leap file */
  if ( !(fname && *fname) )
    return FALSE;

  /* try to stat the leapfile */
  if (0 != stat(fname, &sb_new)) {
    if (logall)
      msyslog(LOG_ERR, "%s ('%s'): stat failed: %m",
        logPrefix, fname);
    return FALSE;
  }

  /* silently skip to postcheck if no new file found */
  if (NULL != sb_old) {
    if (!force
     && sb_old->st_mtime == sb_new.st_mtime
     && sb_old->st_ctime == sb_new.st_ctime
       )
      return FALSE;
    *sb_old = sb_new;
  }

  /* try to open the leap file, complain if that fails
   *
   * [perlinger@ntp.org]
   * coverity raises a TOCTOU (time-of-check/time-of-use) issue
   * here, which is not entirely helpful: While there is indeed a
   * possible race condition between the 'stat()' call above and
   * the 'fopen)' call below, I intentionally want to omit the
   * overhead of opening the file and calling 'fstat()', because
   * in most cases the file would have be to closed anyway without
   * reading the contents.  I chose to disable the coverity
   * warning instead.
   *
   * So unless someone comes up with a reasonable argument why
   * this could be a real issue, I'll just try to silence coverity
   * on that topic.
   */
  /* coverity[toctou] */
  if ((fp = fopen(fname, "r")) == NULL) {
    if (logall)
      msyslog(LOG_ERR,
        "%s ('%s'): open failed: %m",
        logPrefix, fname);
    return FALSE;
  }

  rc = leapsec_load_stream(fp, fname, logall);
  fclose(fp);
  return rc;
}

/* ------------------------------------------------------------------ */
void
leapsec_getsig(
  leap_signature_t * psig)
{
  const leap_table_t * pt;

  pt = leapsec_get_table(FALSE);
  memcpy(psig, &pt->lsig, sizeof(leap_signature_t));
}

/* ------------------------------------------------------------------ */
int/*BOOL*/
leapsec_expired(
  uint32_t       when,
  const time_t * tpiv)
{
  const leap_table_t * pt;
  vint64 limit;

  pt = leapsec_get_table(FALSE);
  limit = ntpcal_ntp_to_ntp(when, tpiv);
  return ucmpv64(&limit, &pt->head.expire) >= 0;
}

/* ------------------------------------------------------------------ */
int32_t
leapsec_daystolive(
  uint32_t       when,
  const time_t * tpiv)
{
  const leap_table_t * pt;
  vint64 limit;

  pt = leapsec_get_table(FALSE);
  limit = ntpcal_ntp_to_ntp(when, tpiv);
  limit = subv64(&pt->head.expire, &limit);
  return ntpcal_daysplit(&limit).hi;
}

/* ------------------------------------------------------------------ */
#if 0 /* currently unused -- possibly revived later */
int/*BOOL*/
leapsec_add_fix(
  int            total,
  uint32_t       ttime,
  uint32_t       etime,
  const time_t * pivot)
{
  time_t         tpiv;
  leap_table_t * pt;
  vint64         tt64, et64;

  if (pivot == NULL) {
    time(&tpiv);
    pivot = &tpiv;
  }

  et64 = ntpcal_ntp_to_ntp(etime, pivot);
  tt64 = ntpcal_ntp_to_ntp(ttime, pivot);
  pt   = leapsec_get_table(TRUE);

  if (   ucmpv64(&et64, &pt->head.expire) <= 0
     || !leapsec_raw(pt, &tt64, total, FALSE) )
    return FALSE;

  pt->lsig.etime = etime;
  pt->lsig.ttime = ttime;
  pt->lsig.taiof = (int16_t)total;

  pt->head.expire = et64;

  return leapsec_set_table(pt);
}
#endif

/* ------------------------------------------------------------------ */
int/*BOOL*/
leapsec_add_dyn(
  int            insert,
  uint32_t       ntpnow,
  const time_t * pivot )
{
  leap_table_t * pt;
  vint64         now64;

  pt = leapsec_get_table(TRUE);
  now64 = ntpcal_ntp_to_ntp(ntpnow, pivot);
  return (   leapsec_add(pt, &now64, (insert != 0))
    && leapsec_set_table(pt));
}

/* ------------------------------------------------------------------ */
int/*BOOL*/
leapsec_autokey_tai(
  int            tai_offset,
  uint32_t       ntpnow    ,
  const time_t * pivot     )
{
  leap_table_t * pt;
  leap_era_t     era;
  vint64         now64;
  int            idx;

  (void)tai_offset;
  pt = leapsec_get_table(FALSE);

  /* Bail out if the basic offset is not zero and the putative
   * offset is bigger than 10s. That was in 1972 -- we don't want
   * to go back that far!
   */
  if (pt->head.base_tai != 0 || tai_offset < 10)
    return FALSE;

  /* If there's already data in the table, check if an update is
   * possible. Update is impossible if there are static entries
   * (since this indicates a valid leapsecond file) or if we're
   * too close to a leapsecond transition: We do not know on what
   * side the transition the sender might have been, so we use a
   * dead zone around the transition.
   */

  /* Check for static entries */
  for (idx = 0; idx != pt->head.size; idx++)
    if ( ! pt->info[idx].dynls)
      return FALSE;

  /* get the fulll time stamp and leap era for it */
  now64 = ntpcal_ntp_to_ntp(ntpnow, pivot);
  fetch_leap_era(&era, pt, &now64);

  /* check the limits with 20s dead band */
  era.ebase = addv64i32(&era.ebase,  20);
  if (ucmpv64(&now64, &era.ebase) < 0)
    return FALSE;

  era.ttime = addv64i32(&era.ttime, -20);
  if (ucmpv64(&now64, &era.ttime) > 0)
    return FALSE;

  /* Here we can proceed. Calculate the delta update. */
  tai_offset -= era.taiof;

  /* Shift the header info offsets. */
  pt->head.base_tai += tai_offset;
  pt->head.this_tai += tai_offset;
  pt->head.next_tai += tai_offset;

  /* Shift table entry offsets (if any) */
  for (idx = 0; idx != pt->head.size; idx++)
    pt->info[idx].taiof += tai_offset;

  /* claim success... */
  return TRUE;
}


/* =====================================================================
 * internal helpers
 */

/* [internal] Reset / init the time window in the leap processor to
 * force reload on next query. Since a leap transition cannot take place
 * at an odd second, the value chosen avoids spurious leap transition
 * triggers. Making all three times equal forces a reload. Using the
 * maximum value for unsigned 64 bits makes finding the next leap frame
 * a bit easier.
 */
static void
reset_times(
  leap_table_t * pt)
{
  memset(&pt->head.ebase, 0xFF, sizeof(vint64));
  pt->head.stime = pt->head.ebase;
  pt->head.ttime = pt->head.ebase;
  pt->head.dtime = pt->head.ebase;
}

/* [internal] Add raw data to the table, removing old entries on the
 * fly. This cannot fail currently.
 */
static int/*BOOL*/
add_range(
  leap_table_t *      pt,
  const leap_info_t * pi)
{
  /* If the table is full, make room by throwing out the oldest
   * entry. But remember the accumulated leap seconds!
   *
   * Setting the first entry is a bit tricky, too: Simply assuming
   * it is an insertion is wrong if the first entry is a dynamic
   * leap second removal. So we decide on the sign -- if the first
   * entry has a negative offset, we assume that it is a leap
   * second removal. In both cases the table base offset is set
   * accordingly to reflect the decision.
   *
   * In practice starting with a removal can only happen if the
   * first entry is a dynamic request without having a leap file
   * for the history proper.
   */
  if (pt->head.size == 0) {
    if (pi->taiof >= 0)
      pt->head.base_tai = pi->taiof - 1;
    else
      pt->head.base_tai = pi->taiof + 1;
  } else if (pt->head.size >= MAX_HIST) {
    pt->head.size     = MAX_HIST - 1;
    pt->head.base_tai = pt->info[pt->head.size].taiof;
  }

  /* make room in lower end and insert item */
  memmove(pt->info+1, pt->info, pt->head.size*sizeof(*pt->info));
  pt->info[0] = *pi;
  pt->head.size++;

  /* invalidate the cached limit data -- we might have news ;-)
   *
   * This blocks a spurious transition detection. OTOH, if you add
   * a value after the last query before a leap transition was
   * expected to occur, this transition trigger is lost. But we
   * can probably live with that.
   */
  reset_times(pt);
  return TRUE;
}

/* [internal] given a reader function, read characters into a buffer
 * until either EOL or EOF is reached. Makes sure that the buffer is
 * always NUL terminated, but silently truncates excessive data. The
 * EOL-marker ('\n') is *not* stored in the buffer.
 *
 * Returns the pointer to the buffer, unless EOF was reached when trying
 * to read the first character of a line.
 */
static char *
get_line(
  leapsec_reader func,
  void *         farg,
  char *         buff,
  size_t         size)
{
  int   ch;
  char *ptr;

  /* if we cannot even store the delimiter, declare failure */
  if (buff == NULL || size == 0)
    return NULL;

  ptr = buff;
  while (EOF != (ch = (*func)(farg)) && '\n' != ch)
    if (size > 1) {
      size--;
      *ptr++ = (char)ch;
    }
  /* discard trailing whitespace */
  while (ptr != buff && isspace((u_char)ptr[-1]))
    ptr--;
  *ptr = '\0';
  return (ptr == buff && ch == EOF) ? NULL : buff;
}

/* [internal] skips whitespace characters from a character buffer. */
static char *
skipws(
  const char *ptr)
{
  while (isspace((u_char)*ptr))
    ptr++;
  return (char*)noconst(ptr);
}

/* [internal] check if a strtoXYZ ended at EOL or whitespace and
 * converted something at all. Return TRUE if something went wrong.
 */
static int/*BOOL*/
parsefail(
  const char * cp,
  const char * ep)
{
  return (cp == ep)
      || (*ep && *ep != '#' && !isspace((u_char)*ep));
}

/* [internal] reload the table limits around the given time stamp. This
 * is where the real work is done when it comes to table lookup and
 * evaluation. Some care has been taken to have correct code for dealing
 * with boundary conditions and empty tables.
 *
 * In electric mode, transition and trip time are the same. In dumb
 * mode, the difference of the TAI offsets must be taken into account
 * and trip time and transition time become different. The difference
 * becomes the warping distance when the trip time is reached.
 */
static void
reload_limits(
  leap_table_t * pt,
  const vint64 * ts)
{
  int idx;

  /* Get full time and search the true lower bound. Use a
   * simple loop here, since the number of entries does
   * not warrant a binary search. This also works for an empty
   * table, so there is no shortcut for that case.
   */
  for (idx = 0; idx != pt->head.size; idx++)
    if (ucmpv64(ts, &pt->info[idx].ttime) >= 0)
      break;

  /* get time limits with proper bound conditions. Note that the
   * bounds of the table will be observed even if the table is
   * empty -- no undefined condition must arise from this code.
   */
  if (idx >= pt->head.size) {
    memset(&pt->head.ebase, 0x00, sizeof(vint64));
    pt->head.this_tai = pt->head.base_tai;
  } else {
    pt->head.ebase    = pt->info[idx].ttime;
    pt->head.this_tai = pt->info[idx].taiof;
  }
  if (--idx >= 0) {
    pt->head.next_tai = pt->info[idx].taiof;
    pt->head.dynls    = pt->info[idx].dynls;
    pt->head.ttime    = pt->info[idx].ttime;

    if (_electric)
      pt->head.dtime = pt->head.ttime;
                else
      pt->head.dtime = addv64i32(
        &pt->head.ttime,
        pt->head.next_tai - pt->head.this_tai);

    pt->head.stime = subv64u32(
      &pt->head.ttime, pt->info[idx].stime);

  } else {
    memset(&pt->head.ttime, 0xFF, sizeof(vint64));
    pt->head.stime    = pt->head.ttime;
    pt->head.dtime    = pt->head.ttime;
    pt->head.next_tai = pt->head.this_tai;
    pt->head.dynls    = 0;
  }
}

/* [internal] fetch the leap era for a given time stamp.
 * This is a cut-down version the algorithm used to reload the table
 * limits, but it does not update any global state and provides just the
 * era information for a given time stamp.
 */
static void
fetch_leap_era(
  leap_era_t         * into,
  const leap_table_t * pt  ,
  const vint64       * ts  )
{
  int idx;

  /* Simple search loop, also works with empty table. */
  for (idx = 0; idx != pt->head.size; idx++)
    if (ucmpv64(ts, &pt->info[idx].ttime) >= 0)
      break;
  /* fetch era data, keeping an eye on boundary conditions */
  if (idx >= pt->head.size) {
    memset(&into->ebase, 0x00, sizeof(vint64));
    into->taiof = pt->head.base_tai;
  } else {
    into->ebase = pt->info[idx].ttime;
    into->taiof = pt->info[idx].taiof;
  }
  if (--idx >= 0)
    into->ttime = pt->info[idx].ttime;
  else
    memset(&into->ttime, 0xFF, sizeof(vint64));
}

/* [internal] Take a time stamp and create a leap second frame for
 * it. This will schedule a leap second for the beginning of the next
 * month, midnight UTC. The 'insert' argument tells if a leap second is
 * added (!=0) or removed (==0). We do not handle multiple inserts
 * (yet?)
 *
 * Returns 1 if the insert worked, 0 otherwise. (It's not possible to
 * insert a leap second into the current history -- only appending
 * towards the future is allowed!)
 */
static int/*BOOL*/
leapsec_add(
  leap_table_t*  pt    ,
  const vint64 * now64 ,
  int            insert)
{
  vint64    ttime, starttime;
  struct calendar fts;
  leap_info_t li;

  /* Check against the table expiration and the latest available
   * leap entry. Do not permit inserts, only appends, and only if
   * the extend the table beyond the expiration!
   */
  if (   ucmpv64(now64, &pt->head.expire) < 0
      || (pt->head.size && ucmpv64(now64, &pt->info[0].ttime) <= 0)) {
    errno = ERANGE;
    return FALSE;
  }

  ntpcal_ntp64_to_date(&fts, now64);
  /* To guard against dangling leap flags: do not accept leap
   * second request on the 1st hour of the 1st day of the month.
   */
  if (fts.monthday == 1 && fts.hour == 0) {
    errno = EINVAL;
    return FALSE;
  }

  /* Ok, do the remaining calculations */
  fts.monthday = 1;
  fts.hour     = 0;
  fts.minute   = 0;
  fts.second   = 0;
  starttime = ntpcal_date_to_ntp64(&fts);
  fts.month++;
  ttime = ntpcal_date_to_ntp64(&fts);

  li.ttime = ttime;
  li.stime = ttime.D_s.lo - starttime.D_s.lo;
  li.taiof = (pt->head.size ? pt->info[0].taiof : pt->head.base_tai)
           + (insert ? 1 : -1);
  li.dynls = 1;
  return add_range(pt, &li);
}

/* [internal] Given a time stamp for a leap insertion (the exact begin
 * of the new leap era), create new leap frame and put it into the
 * table. This is the work horse for reading a leap file and getting a
 * leap second update via authenticated network packet.
 */
int/*BOOL*/
leapsec_raw(
  leap_table_t * pt,
  const vint64 * ttime,
  int            taiof,
  int            dynls)
{
  vint64    starttime;
  struct calendar fts;
  leap_info_t li;

  /* Check that we either extend the table or get a duplicate of
   * the latest entry. The latter is a benevolent overwrite with
   * identical data and could happen if we get an autokey message
   * that extends the lifetime of the current leapsecond table.
   * Otherwise paranoia rulez!
   */
  if (pt->head.size) {
    int cmp = ucmpv64(ttime, &pt->info[0].ttime);
    if (cmp == 0)
      cmp -= (taiof != pt->info[0].taiof);
    if (cmp < 0) {
      errno = ERANGE;
      return FALSE;
    }
    if (cmp == 0)
      return TRUE;
  }

  ntpcal_ntp64_to_date(&fts, ttime);
  /* If this does not match the exact month start, bail out. */
  if (fts.monthday != 1 || fts.hour || fts.minute || fts.second) {
    errno = EINVAL;
    return FALSE;
  }
  fts.month--; /* was in range 1..12, no overflow here! */
  starttime = ntpcal_date_to_ntp64(&fts);
  li.ttime = *ttime;
  li.stime = ttime->D_s.lo - starttime.D_s.lo;
  li.taiof = (int16_t)taiof;
  li.dynls = (dynls != 0);
  return add_range(pt, &li);
}

/* [internal] Do a wrap-around save range inclusion check.
 * Returns TRUE if x in [lo,hi[ (intervall open on right side) with full
 * handling of an overflow / wrap-around.
 */
static int/*BOOL*/
betweenu32(
  uint32_t lo,
  uint32_t x,
  uint32_t hi)
{
  int rc;

  if (lo <= hi)
    rc = (lo <= x) && (x < hi);
  else
    rc = (lo <= x) || (x < hi);
  return rc;
}

/* =====================================================================
 * validation stuff
 */

typedef struct {
  unsigned char hv[ISC_SHA1_DIGESTLENGTH];
} sha1_digest;

/* [internal] parse a digest line to get the hash signature
 * The NIST code creating the hash writes them out as 5 hex integers
 * without leading zeros. This makes reading them back as hex-encoded
 * BLOB impossible, because there might be less than 40 hex digits.
 *
 * The solution is to read the values back as integers, and then do the
 * byte twiddle necessary to get it into an array of 20 chars. The
 * drawback is that it permits any acceptable number syntax provided by
 * 'scanf()' and 'strtoul()', including optional signs and '0x'
 * prefixes.
 */
static int/*BOOL*/
do_leap_hash(
  sha1_digest * mac,
  char const  * cp )
{
  int wi, di, num, len;
  unsigned long tmp[5];

  memset(mac, 0, sizeof(*mac));
  num = sscanf(cp, " %lx %lx %lx %lx %lx%n",
         &tmp[0], &tmp[1], &tmp[2], &tmp[3], &tmp[4],
         &len);
  if (num != 5 || cp[len] > ' ')
    return FALSE;

  /* now do the byte twiddle */
  for (wi=0; wi < 5; ++wi)
    for (di=3; di >= 0; --di) {
      mac->hv[wi*4 + di] =
        (unsigned char)(tmp[wi] & 0x0FF);
      tmp[wi] >>= 8;
    }
  return TRUE;
}

/* [internal] add the digits of a data line to the hash, stopping at the
 * next hash ('#') character.
 */
static void
do_hash_data(
  isc_sha1_t * mdctx,
  char const * cp   )
{
  unsigned char  text[32]; // must be power of two!
  unsigned int   tlen =  0;
  unsigned char  ch;

  while ('\0' != (ch = *cp++) && '#' != ch)
    if (isdigit(ch)) {
      text[tlen++] = ch;
      tlen &= (sizeof(text)-1);
      if (0 == tlen)
        isc_sha1_update(
          mdctx, text, sizeof(text));
    }

  if (0 < tlen)
    isc_sha1_update(mdctx, text, tlen);
}

/* given a reader and a reader arg, calculate and validate the the hash
 * signature of a NIST leap second file.
 */
int
leapsec_validate(
  leapsec_reader func,
  void *         farg)
{
  isc_sha1_t     mdctx;
  sha1_digest    rdig, ldig; /* remote / local digests */
  char           line[50];
  int            hlseen = -1;

  isc_sha1_init(&mdctx);
  while (get_line(func, farg, line, sizeof(line))) {
    if (!strncmp(line, "#h", 2))
      hlseen = do_leap_hash(&rdig, line+2);
    else if (!strncmp(line, "#@", 2))
      do_hash_data(&mdctx, line+2);
    else if (!strncmp(line, "#$", 2))
      do_hash_data(&mdctx, line+2);
    else if (isdigit((unsigned char)line[0]))
      do_hash_data(&mdctx, line);
  }
  isc_sha1_final(&mdctx, ldig.hv);
  isc_sha1_invalidate(&mdctx);

  if (0 > hlseen)
    return LSVALID_NOHASH;
  if (0 == hlseen)
    return LSVALID_BADFORMAT;
  if (0 != memcmp(&rdig, &ldig, sizeof(sha1_digest)))
    return LSVALID_BADHASH;
  return LSVALID_GOODHASH;
}

/*
 * lstostr - prettyprint NTP seconds
 */
static const char *
lstostr(
  const vint64 * ts)
{
  char *    buf;
  struct calendar tm;

  LIB_GETBUF(buf);

  if ( ! (ts->d_s.hi >= 0 && ntpcal_ntp64_to_date(&tm, ts) >= 0))
    snprintf(buf, LIB_BUFLENGTH, "%s", "9999-12-31T23:59:59Z");
  else
    snprintf(buf, LIB_BUFLENGTH, "%04d-%02d-%02dT%02d:%02d:%02dZ",
      tm.year, tm.month, tm.monthday,
      tm.hour, tm.minute, tm.second);

  return buf;
}

/* reset the global state for unit tests */
void
leapsec_ut_pristine(void)
{
  memset(_ltab, 0, sizeof(_ltab));
  _lptr     = NULL;
  _electric = 0;
}



/* -*- that's all folks! -*- */

Coverage Report

Created: 2023-05-19 06:16