1/* crond.c - daemon to execute scheduled commands.
2 *
3 * Copyright 2014 Ranjan Kumar <ranjankumar.bth@gmail.com>
4 *
5 * No Standard
6
7USE_CROND(NEWTOY(crond, "fbSl#<0=8d#<0L:c:[-bf][-LS][-ld]", TOYFLAG_USR|TOYFLAG_SBIN|TOYFLAG_NEEDROOT))
8
9config CROND
10  bool "crond"
11  default n
12  help
13    usage: crond [-fbS] [-l N] [-d N] [-L LOGFILE] [-c DIR]
14
15    A daemon to execute scheduled commands.
16
17    -b Background (default)
18    -c crontab dir
19    -d Set log level, log to stderr
20    -f Foreground
21    -l Set log level. 0 is the most verbose, default 8
22    -S Log to syslog (default)
23    -L Log to file
24*/
25
26#define FOR_crond
27#include "toys.h"
28
29GLOBALS(
30  char *crontabs_dir;
31  char *logfile;
32  int loglevel_d;
33  int loglevel;
34
35  time_t crontabs_dir_mtime;
36  uint8_t flagd;
37)
38
39typedef struct _var {
40  struct _var *next, *prev;
41  char *name, *val;
42} VAR;
43
44typedef struct _job {
45  struct _job *next, *prev;
46  char min[60], hour[24], dom[31], mon[12], dow[7], *cmd;
47  int isrunning, needstart, mailsize;
48  pid_t pid;
49} JOB;
50
51typedef struct _cronfile {
52  struct _cronfile *next, *prev;
53  struct double_list *job, *var;
54  char *username, *mailto;
55  int invalid;
56} CRONFILE;
57
58static char days[]={"sun""mon""tue""wed""thu""fri""sat"};
59static char months[]={"jan""feb""mar""apr""may""jun""jul"
60  "aug""sep""oct""nov""dec"};
61CRONFILE *gclist;
62
63#define LOG_EXIT 0
64#define LOG_LEVEL5 5
65#define LOG_LEVEL7 7
66#define LOG_LEVEL8 8
67#define LOG_LEVEL9 9 // warning
68#define LOG_ERROR 20
69
70static void loginfo(uint8_t loglevel, char *msg, ...)
71{
72  va_list s, d;
73
74  va_start(s, msg);
75  va_copy(d, s);
76  if (loglevel >= TT.loglevel) {
77    int used;
78    char *smsg;
79
80    if (!TT.flagd && TT.logfile) {
81      int fd = open(TT.logfile, O_WRONLY | O_CREAT | O_APPEND, 0666);
82      if (fd >=0 && fd != 2) {
83        dup2(fd, 2);
84        close(fd);
85      } else if (fd < 0) perror_msg("'%s", TT.logfile);
86    }
87    used = vsnprintf(NULL, 0, msg, d);
88    smsg = xzalloc(++used);
89    vsnprintf(smsg, used, msg, s);
90    if (TT.flagd || TT.logfile) {
91      fflush(NULL);
92      smsg[used-1] = '\n';
93      writeall((loglevel > 8) ? 2 : 1, smsg, used);
94    } else syslog((loglevel > 8) ? LOG_ERR : LOG_INFO, "%s", smsg);
95    free(smsg);
96  }
97  va_end(d);
98  va_end(s);
99  if (!loglevel) exit(20);
100}
101
102/*
103 * Names can also be used for the 'month' and 'day of week' fields
104 * (First three letters of the particular day or month).
105 */
106static int getindex(char *src, int size)
107{
108  int i;
109  char *field = (size == 12) ? months : days;
110
111  // strings are not allowed for min, hour and dom fields.
112  if (!(size == 7 || size == 12)) return -1;
113
114  for (i = 0; field[i]; i += 3) {
115    if (!strncasecmp(src, &field[i], 3))
116      return (i/3);
117  }
118  return -1;
119}
120
121// set elements of minute, hour, day of month, month and day of week arrays.
122static void fillarray(char *dst, int start, int end, int skip)
123{
124  int sk = 1;
125
126  if (end < 0) {
127    dst[start] = 1;
128    return;
129  }
130  if (!skip) skip = 1;
131  do {
132    if (!--sk) {
133      dst[start] = 1;
134      sk = skip;
135    }
136  } while (start++ != end);
137}
138
139static long getval(char *num, long low, long high)
140{
141  long val = strtol(num, &num, 10);
142
143  if (*num || (val < low) || (val > high)) return -1;
144  return val;
145}
146
147//static int parse_and_fillarray(char *dst, int size, char *src)
148static int parse_and_fillarray(char *dst, int min, int max, char *src)
149{
150  int start, end, skip = 0;
151  char *ptr = strchr(src, '/');
152
153  if (ptr) {
154    *ptr++ = 0;
155    if ((skip = getval(ptr, min, (min ? max: max-1))) < 0) goto ERROR;
156  }
157
158  if (*src == '-' || *src == ',') goto ERROR;
159  if (*src == '*') {
160    if (*(src+1)) goto ERROR;
161    fillarray(dst, 0, max-1, skip);
162  } else {
163    for (;;) {
164      char *ctoken = strsep(&src, ","), *dtoken;
165
166      if (!ctoken) break;
167      if (!*ctoken) goto ERROR;
168
169      // Get start position.
170      dtoken = strsep(&ctoken, "-");
171      if (isdigit(*dtoken)) {
172        if ((start = getval(dtoken, min, (min ? max : max-1))) < 0) goto ERROR;
173        start = min ? (start-1) : start;
174      } else if ((start = getindex(dtoken, max)) < 0) goto ERROR;
175
176      // Get end position.
177      if (!ctoken) end = -1; // e.g. N1,N2,N3
178      else if (*ctoken) {// e.g. N-M
179        if (isdigit(*ctoken)) {
180          if ((end = getval(ctoken, min, (min ? max : max-1))) < 0) goto ERROR;
181          end = min ? (end-1) : end;
182        } else if ((end = getindex(ctoken, max)) < 0) goto ERROR;
183        if (end == start) end = -1;
184      } else goto ERROR; // error condition 'N-'
185      fillarray(dst, start, end, skip);
186    }
187  }
188
189  if (TT.flagd && (TT.loglevel <= 5)) {
190    for (start = 0; start < max; start++)
191      fprintf(stderr, "%d", (unsigned char)dst[start]);
192    fputc('\n', stderr);
193  }
194  return 0;
195ERROR:
196  loginfo(LOG_LEVEL9, "parse error at %s", src);
197  return -1;
198}
199
200static char *omitspace(char *line)
201{
202  while (*line == ' ' || *line == '\t') line++;
203  return line;
204}
205
206static void parse_line(char *line, CRONFILE *cfile)
207{
208  int count = 0;
209  char *name, *val, *tokens[5] = {0,};
210  VAR *v;
211  JOB *j;
212
213  line = omitspace(line);
214  if (!*line || *line == '#') return;
215
216  /*
217   * TODO: Enhancement to support 8 special strings
218   * @reboot -> Run once at startup.
219   * @yearly -> Run once a year (0 0 1 1 *).
220   * @annually -> Same as above.
221   * @monthly -> Run once a month (0 0 1 * *).
222   * @weekly -> Run once a week (0 0 * * 0).
223   * @daily -> Run once a day (0 0 * * *).
224   * @midnight -> same as above.
225   * @hourly -> Run once an hour (0 * * * *).
226   */
227  if (*line == '@') return;
228  if (TT.flagd) loginfo(LOG_LEVEL5, "user:%s entry:%s", cfile->username, line);
229  while (count<5) {
230    int len = strcspn(line, " \t");
231
232    if (line[len]) line[len++] = '\0';
233    tokens[count++] = line;
234    line += len;
235    line = omitspace(line);
236    if (!*line) break;
237  }
238
239  switch (count) {
240    case 1: // form SHELL=/bin/sh
241      name = tokens[0];
242      if ((val = strchr(name, '='))) *val++ = 0;
243      if (!val || !*val) return;
244      break;
245    case 2: // form SHELL =/bin/sh or SHELL= /bin/sh
246      name = tokens[0];
247      if ((val = strchr(name, '='))) {
248        *val = 0;
249        val = tokens[1];
250      } else {
251        if (*(tokens[1]) != '=') return;
252        val = tokens[1] + 1;
253      }
254      if (!*val) return;
255      break;
256    case 3: // NAME = VAL
257      name = tokens[0];
258      val = tokens[2];
259      if (*(tokens[1]) != '=') return;
260      break;
261    case 5:
262      // don't have any cmd to execute.
263      if (!*line) return;
264      j = xzalloc(sizeof(JOB));
265
266      if (parse_and_fillarray(j->min, 0, sizeof(j->min), tokens[0]))
267        goto STOP_PARSING;
268      if (parse_and_fillarray(j->hour, 0, sizeof(j->hour), tokens[1]))
269        goto STOP_PARSING;
270      if (parse_and_fillarray(j->dom, 1, sizeof(j->dom), tokens[2]))
271        goto STOP_PARSING;
272      if (parse_and_fillarray(j->mon, 1, sizeof(j->mon), tokens[3]))
273        goto STOP_PARSING;
274      if (parse_and_fillarray(j->dow, 0, sizeof(j->dow), tokens[4]))
275        goto STOP_PARSING;
276      j->cmd = xstrdup(line);
277
278      if (TT.flagd) loginfo(LOG_LEVEL5, " command:%s", j->cmd);
279      dlist_add_nomalloc((struct double_list **)&cfile->job, (struct double_list *)j);
280      return;
281STOP_PARSING:
282      free(j);
283      return;
284    default: return;
285  }
286  if (!strcmp(name, "MAILTO")) cfile->mailto = xstrdup(val);
287  else {
288    v = xzalloc(sizeof(VAR));
289    v->name = xstrdup(name);
290    v->val = xstrdup(val);
291    dlist_add_nomalloc((struct double_list **)&cfile->var, (struct double_list *)v);
292  }
293}
294
295static void free_jobs(JOB **jlist)
296{
297  JOB *j = dlist_pop(jlist);
298  free(j->cmd);
299  free(j);
300}
301
302static void free_cronfile(CRONFILE **list)
303{
304  CRONFILE *l = dlist_pop(list);
305  VAR *v, *vnode = (VAR *)l->var;
306
307  if (l->username != l->mailto) free(l->mailto);
308  free(l->username);
309  while (vnode && (v = dlist_pop(&vnode))) {
310    free(v->name);
311    free(v->val);
312    free(v);
313  }
314  free(l);
315}
316
317/*
318 * Iterate all cronfiles to identify the completed jobs and freed them.
319 * If all jobs got completed for a cronfile, freed cronfile too.
320 */
321static void remove_completed_jobs()
322{
323  CRONFILE *lstart, *list = gclist;
324
325  lstart = list;
326  while (list) {
327    int delete = 1;
328    JOB *jstart, *jlist = (JOB *)list->job;
329
330    list->invalid = 1;
331    jstart = jlist;
332    while (jlist) {
333      jlist->isrunning = 0;
334      if (jlist->pid > 0) {
335        jlist->isrunning = 1;
336        delete = 0;
337        jlist = jlist->next;
338      } else {
339        if (jlist == jstart) { // if 1st node has to delete.
340          jstart = jstart->next;
341          free_jobs(&jlist);
342          continue;
343        } else free_jobs(&jlist);
344      }
345      if (jlist == jstart) break;
346    }
347    list->job = (struct double_list *)jlist;
348
349    if (delete) {
350      if (lstart == list) {
351        lstart = lstart->next;
352        free_cronfile(&list);
353        continue;
354      } else free_cronfile(&list);
355    }
356    list = list->next;
357    if (lstart == list) break;
358  }
359  gclist = list;
360}
361
362// Scan cronfiles and prepare the list of cronfiles with their jobs.
363static void scan_cronfiles()
364{
365  DIR *dp;
366  struct dirent *entry;
367
368  remove_completed_jobs();
369  if (chdir(TT.crontabs_dir)) loginfo(LOG_EXIT, "chdir(%s)", TT.crontabs_dir);
370  if (!(dp = opendir("."))) loginfo(LOG_EXIT, "chdir(%s)", ".");
371
372  while ((entry = readdir(dp))) {
373    int fd;
374    char *line;
375    CRONFILE *cfile;
376
377    if (entry->d_name[0] == '.' && (!entry->d_name[1] ||
378          (entry->d_name[1] == '.' && !entry->d_name[2])))
379      continue;
380
381    if (!getpwnam(entry->d_name)) {
382      loginfo(LOG_LEVEL7, "ignoring file '%s' (no such user)", entry->d_name);
383      continue;
384    }
385    if ((fd = open(entry->d_name, O_RDONLY)) < 0) continue;
386
387    // one node for each user
388    cfile = xzalloc(sizeof(CRONFILE));
389    cfile->username = xstrdup(entry->d_name);
390
391    for (; (line = get_line(fd)); free(line))
392      parse_line(line, cfile);
393
394    // If there is no job for a cron, remove the VAR list.
395    if (!cfile->job) {
396      VAR *v, *vnode = (VAR *)cfile->var;
397
398      free(cfile->username);
399      if (cfile->mailto) free(cfile->mailto);
400
401      while (vnode && (v = dlist_pop(&vnode))) {
402        free(v->name);
403        free(v->val);
404        free(v);
405      }
406      free(cfile);
407    } else {
408      if (!cfile->mailto) cfile->mailto = cfile->username;
409      dlist_add_nomalloc((struct double_list **)&gclist,
410          (struct double_list *)cfile);
411    }
412    close(fd);
413  }
414  closedir(dp);
415}
416
417/*
418 * Set env variables, if any in the cronfile. Execute given job with the given
419 * SHELL or Default SHELL and send an e-mail with respect to every successfully
420 * completed job (as per the given param 'prog').
421 */
422static void do_fork(CRONFILE *cfile, JOB *job, int fd, char *prog)
423{
424  pid_t pid = vfork();
425
426  if (pid == 0) {
427    VAR *v, *vstart = (VAR *)cfile->var;
428    struct passwd *pwd = getpwnam(cfile->username);
429
430    if (!pwd) loginfo(LOG_LEVEL9, "can't get uid for %s", cfile->username);
431    else {
432      char *file = "/bin/sh";
433
434      if (setenv("USER", pwd->pw_name, 1)) _exit(1);
435      for (v = vstart; v;) {
436        if (!strcmp("SHELL", v->name)) file = v->val;
437        if (setenv(v->name, v->val, 1)) _exit(1);
438        if ((v=v->next) == vstart) break;
439      }
440      if (!getenv("HOME")) {
441        if (setenv("HOME", pwd->pw_dir, 1))
442          _exit(1);
443      }
444      xsetuser(pwd);
445      if (chdir(pwd->pw_dir)) loginfo(LOG_LEVEL9, "chdir(%s)", pwd->pw_dir);
446      if (prog) file = prog;
447      if (TT.flagd) loginfo(LOG_LEVEL5, "child running %s", file);
448
449      if (fd >= 0) {
450        int newfd = prog ? 0 : 1;
451        if (fd != newfd) {
452          dup2(fd, newfd);
453          close(fd);
454        }
455        dup2(1, 2);
456      }
457      setpgrp();
458      execlp(file, file, (prog ? "-ti" : "-c"), (prog ? NULL : job->cmd), (char *) NULL);
459      loginfo(LOG_ERROR, "can't execute '%s' for user %s", file, cfile->username);
460
461      if (!prog) dprintf(1, "Exec failed: %s -c %s\n", file, job->cmd);
462      _exit(EXIT_SUCCESS);
463    }
464  }
465  if (pid < 0) {
466    loginfo(LOG_ERROR, "can't vfork");
467    pid = 0;
468  }
469  if (fd >=0) close(fd);
470  job->pid = pid;
471}
472
473// Send an e-mail for each successfully completed jobs.
474static void sendmail(CRONFILE *cfile, JOB *job)
475{
476  pid_t pid = job->pid;
477  int mailfd;
478  struct stat sb;
479
480  job->pid = 0;
481  if (pid <=0 || job->mailsize <=0) {
482    job->isrunning = 0;
483    job->needstart = 1;
484    return;
485  }
486  snprintf(toybuf, sizeof(toybuf), "/var/spool/cron/cron.%s.%d",
487      cfile->username, (int)pid);
488
489  mailfd = open(toybuf, O_RDONLY);
490  unlink(toybuf);
491  if (mailfd < 0) return;
492
493  if (fstat(mailfd, &sb) == -1 || sb.st_uid != 0 || sb.st_nlink != 0
494      || sb.st_size == job->mailsize || !S_ISREG(sb.st_mode)) {
495    xclose(mailfd);
496    return;
497  }
498  job->mailsize = 0;
499  do_fork(cfile, job, mailfd, "sendmail");
500}
501
502// Count the number of jobs, which are not completed.
503static int count_running_jobs()
504{
505  CRONFILE *cfile = gclist;
506  JOB *job, *jstart;
507  int count = 0;
508
509  while (cfile) {
510    job = jstart = (JOB *)cfile->job;
511    while (job) {
512      int ret;
513
514      if (!job->isrunning || job->pid<=0) goto NEXT_JOB;
515      job->isrunning = 0;
516      ret = waitpid(job->pid, NULL, WNOHANG);
517      if (ret < 0 || ret == job->pid) {
518        sendmail(cfile, job);
519        if (job->pid) count += (job->isrunning=1);
520        else {
521          job->isrunning = 0;
522          job->needstart = 1;
523        }
524      }
525      else count += (job->isrunning=1);
526
527NEXT_JOB:
528      if ((job = job->next) == jstart) break;
529    }
530    if ((cfile = cfile->next) == gclist) break;
531  }
532  return count;
533}
534
535// Execute jobs one by one and prepare for the e-mail sending.
536static void execute_jobs(void)
537{
538  CRONFILE *cfile = gclist;
539  JOB *job, *jstart;
540
541  while (cfile) {
542    job = jstart = (JOB *)cfile->job;
543    while (job) {
544      if (job->needstart) {
545        job->needstart = 0;
546        if (job->pid < 0) {
547          int mailfd = -1;
548
549          job->mailsize = job->pid = 0;
550          snprintf(toybuf, sizeof(toybuf), "/var/spool/cron/cron.%s.%d",
551              cfile->username, getpid());
552          if ((mailfd = open(toybuf, O_CREAT|O_TRUNC|O_WRONLY|O_EXCL|O_APPEND,
553                  0600)) < 0) {
554            loginfo(LOG_ERROR, "can't create mail file %s for user %s, "
555                "discarding output", toybuf, cfile->username);
556          } else {
557            dprintf(mailfd, "To: %s\nSubject: cron: %s\n\n", cfile->mailto, job->cmd);
558            job->mailsize = lseek(mailfd, 0, SEEK_CUR);
559          }
560          do_fork(cfile, job, mailfd, NULL);
561          if (mailfd >= 0) {
562            if (job->pid <= 0) unlink(toybuf);
563            else {
564              char *mailfile = xmprintf("/var/spool/cron/cron.%s.%d",
565                  cfile->username, (int)job->pid);
566              rename(toybuf, mailfile);
567              free(mailfile);
568            }
569          }
570          loginfo(LOG_LEVEL8, "USER %s pid %3d cmd %s",
571              cfile->username, job->pid, job->cmd);
572          if (job->pid < 0) job->needstart = 1;
573          else job->isrunning = 1;
574        }
575      }
576      if ((job = job->next) == jstart) break;
577    }
578    if ((cfile = cfile->next) == gclist) break;
579  }
580}
581
582// Identify jobs, which needs to be started at the given time interval.
583static void schedule_jobs(time_t ctime, time_t ptime)
584{
585  time_t tm = ptime-ptime%60;
586
587  for (; tm <= ctime; tm += 60) {
588    struct tm *lt;
589    CRONFILE *cfile = gclist;
590    JOB *job, *jstart;
591
592    if (tm <= ptime) continue;
593    lt = localtime(&tm);
594
595    while (cfile) {
596      if (TT.flagd) loginfo(LOG_LEVEL5, "file %s:", cfile->username);
597      if (cfile->invalid) goto NEXT_CRONFILE;
598      job = jstart = (JOB *)cfile->job;
599
600      while (job) {
601        if (TT.flagd) loginfo(LOG_LEVEL5, " line %s", job->cmd);
602
603        if (job->min[lt->tm_min] && job->hour[lt->tm_hour]
604            && (job->dom[lt->tm_mday] || job->dow[lt->tm_wday])
605            && job->mon[lt->tm_mon-1]) {
606          if (TT.flagd)
607            loginfo(LOG_LEVEL5, " job: %d %s\n", (int)job->pid, job->cmd);
608          if (job->pid > 0) {
609            loginfo(LOG_LEVEL8, "user %s: process already running: %s",
610                cfile->username, job->cmd);
611          } else if (!job->pid) {
612            job->pid = -1;
613            job->needstart = 1;
614            job->isrunning = 0;
615          }
616        }
617        if ((job = job->next) == jstart) break;
618      }
619NEXT_CRONFILE:
620      if ((cfile = cfile->next) == gclist) break;
621    }
622  }
623}
624
625void crond_main(void)
626{
627  time_t ctime, ptime;
628  int sleepfor = 60;
629  struct stat sb;
630
631  TT.flagd = (toys.optflags & FLAG_d);
632
633  // Setting default params.
634  if (TT.flagd) TT.loglevel = TT.loglevel_d;
635  if (!(toys.optflags & (FLAG_f | FLAG_b))) toys.optflags |= FLAG_b;
636  if (!(toys.optflags & (FLAG_S | FLAG_L))) toys.optflags |= FLAG_S;
637
638  if ((toys.optflags & FLAG_c)
639      && (TT.crontabs_dir[strlen(TT.crontabs_dir)-1] != '/'))
640    TT.crontabs_dir = xmprintf("%s/", TT.crontabs_dir);
641
642  if (!TT.crontabs_dir) TT.crontabs_dir = xstrdup("/var/spool/cron/crontabs/");
643  if (toys.optflags & FLAG_b) daemon(0,0);
644
645  if (!TT.flagd && !TT.logfile)
646    openlog(toys.which->name, LOG_CONS | LOG_PID, LOG_CRON);
647
648  // Set default shell once.
649  if (setenv("SHELL", "/bin/sh", 1)) error_exit("Can't set default shell");
650  xchdir(TT.crontabs_dir);
651  loginfo(LOG_LEVEL8, "crond started, log level %d", TT.loglevel);
652
653  if (stat(TT.crontabs_dir, &sb)) sb.st_mtime = 0;
654  TT.crontabs_dir_mtime = sb.st_mtime;
655  scan_cronfiles();
656  ctime = time(NULL);
657
658  while (1) {
659    long tdiff;
660
661    ptime = ctime;
662    sleep(sleepfor - (ptime%sleepfor) +1);
663    tdiff =(long) ((ctime = time(NULL)) - ptime);
664
665    if (stat(TT.crontabs_dir, &sb)) sb.st_mtime = 0;
666    if (TT.crontabs_dir_mtime != sb.st_mtime) {
667      TT.crontabs_dir_mtime = sb.st_mtime;
668      scan_cronfiles();
669    }
670
671    if (TT.flagd) loginfo(LOG_LEVEL5, "wakeup diff=%ld\n", tdiff);
672    if (tdiff < -60 * 60 || tdiff > 60 * 60)
673      loginfo(LOG_LEVEL9, "time disparity of %ld minutes detected", tdiff / 60);
674    else if (tdiff > 0) {
675      schedule_jobs(ctime, ptime);
676      execute_jobs();
677      if (count_running_jobs()) sleepfor = 10;
678      else sleepfor = 60;
679    }
680  }
681}
682