crontab.c

   1
   2 /*
   3  * CRONTAB.C
   4  *
   5  * CRONTAB
   6  *
   7  * usually setuid root, -c option only works if getuid() == geteuid()
   8  *
   9  * Copyright 1994 Matthew Dillon (dillon@apollo.backplane.com)
  10  * Copyright 2009 James Pryor <profjim@jimpryor.net>
  11  * May be distributed under the GNU General Public License
  12  */
  13
  14 #include "defs.h"
  15
  16 const char *CDir = CRONTABS;
  17 int   UserId;
  18 /* not used in this program, but subs.c needs */
  19 short LogLevel = LOG_NOTICE;
  20 short ForegroundOpt = 0;
  21 short LoggerOpt = 0;
  22 const char *LogFile = LOG_FILE;
  23 char *TempDir = TMPDIR;
  24
  25 void EditFile(const char *user, const char *file);
  26 int GetReplaceStream(const char *user, const char *file);
  27
  28 int
  29 main(int ac, char **av)
  30 {
  31         enum { NONE, EDIT, LIST, REPLACE, DELETE } option = NONE;
  32         struct passwd *pas;
  33         char *repFile = NULL;
  34         int repFd = 0;
  35         int i;
  36         char caller[256];               /* user that ran program */
  37
  38         UserId = getuid();
  39         if ((pas = getpwuid(UserId)) == NULL) {
  40                 perror("getpwuid");
  41                 exit(1);
  42         }
  43         snprintf(caller, sizeof(caller), "%s", pas->pw_name);
  44
  45         i = 1;
  46         if (ac > 1) {
  47                 if (av[1][0] == '-' && av[1][1] == 0) {
  48                         option = REPLACE;
  49                         ++i;
  50                 } else if (av[1][0] != '-') {
  51                         option = REPLACE;
  52                         ++i;
  53                         repFile = av[1];
  54                 }
  55         }
  56
  57         opterr = 0;
  58
  59         while ((i=getopt(ac,av,"ledu:c:")) != EOF) {
  60                 switch(i) {
  61                         case 'l':
  62                                         option = LIST;
  63                                 break;
  64                         case 'e':
  65                                         option = EDIT;
  66                                 break;
  67                         case 'd':
  68                                         option = DELETE;
  69                                 break;
  70                         case 'u':
  71                                 if (*optarg != 0 && getuid() == geteuid()) {
  72                                         pas = getpwnam(optarg);
  73                                         if (pas) {
  74                                                 UserId = pas->pw_uid;
  75                                         } else {
  76                                                 errx(1, "user %s unknown", optarg);
  77                                         }
  78                                 } else {
  79                                         errx(1, "only the superuser may specify a user");
  80                                 }
  81                                 break;
  82                         case 'c':
  83                                 if (*optarg != 0 && getuid() == geteuid()) {
  84                                         CDir = optarg;
  85                                 } else {
  86                                         errx(1, "-c option: superuser only");
  87                                 }
  88                                 break;
  89                         default:
  90                                 option = NONE;
  91                 }
  92         }
  93
  94         if (option == NONE) {
  95                 /*
  96                  * parse error
  97                  */
  98                 printf("crontab " VERSION "\n");
  99                 printf("crontab file <opts>  replace crontab from file\n");
 100                 printf("crontab -    <opts>  replace crontab from stdin\n");
 101                 printf("crontab -u user      specify user\n");
 102                 printf("crontab -l [user]    list crontab for user\n");
 103                 printf("crontab -e [user]    edit crontab for user\n");
 104                 printf("crontab -d [user]    delete crontab for user\n");
 105                 printf("crontab -c dir       specify crontab directory\n");
 106                 exit(2);
 107         }
 108
 109         /*
 110          * Get password entry
 111          */
 112
 113         if ((pas = getpwuid(UserId)) == NULL) {
 114                 perror("getpwuid");
 115                 exit(1);
 116         }
 117
 118         /*
 119          * If there is a replacement file, obtain a secure descriptor to it.
 120          */
 121
 122         if (repFile) {
 123                 repFd = GetReplaceStream(caller, repFile);
 124                 if (repFd < 0) {
 125                         errx(1, "unable to read replacement file");
 126                 }
 127         }
 128
 129         /*
 130          * Change directory to our crontab directory
 131          */
 132
 133         if (chdir(CDir) < 0) {
 134                 errx(1, "cannot change dir to %s: %s", CDir, strerror(errno));
 135         }
 136
 137         /*
 138          * Handle options as appropriate
 139          */
 140
 141         switch(option) {
 142                 case LIST:
 143                         {
 144                                 FILE *fi;
 145                                 char buf[1024];
 146
 147                                 if ((fi = fopen(pas->pw_name, "r"))) {
 148                                         while (fgets(buf, sizeof(buf), fi) != NULL)
 149                                                 fputs(buf, stdout);
 150                                         fclose(fi);
 151                                 } else {
 152                                         fprintf(stderr, "no crontab for %s\n", pas->pw_name);
 153                                 }
 154                         }
 155                         break;
 156                 case EDIT:
 157                         {
 158                                 FILE *fi;
 159                                 int fd;
 160                                 int n;
 161                                 char tmp[] = TMPDIR "/crontab.XXXXXX";
 162                                 char buf[1024];
 163
 164                                 if ((fd = mkstemp(tmp)) >= 0) {
 165                                         chown(tmp, getuid(), getgid());
 166                                         if ((fi = fopen(pas->pw_name, "r"))) {
 167                                                 while ((n = fread(buf, 1, sizeof(buf), fi)) > 0)
 168                                                         write(fd, buf, n);
 169                                         }
 170                                         EditFile(caller, tmp);
 171                                         remove(tmp);
 172                                         lseek(fd, 0L, 0);
 173                                         repFd = fd;
 174                                 } else {
 175                                         errx(1, "unable to create %s", tmp);
 176                                 }
 177
 178                         }
 179                         option = REPLACE;
 180                         /* fall through */
 181                 case REPLACE:
 182                         {
 183                                 char buf[1024];
 184                                 char path[1024];
 185                                 int fd;
 186                                 int n;
 187
 188                                 snprintf(path, sizeof(path), "%s.new", pas->pw_name);
 189                                 if ((fd = open(path, O_CREAT|O_TRUNC|O_EXCL|O_APPEND|O_WRONLY, 0600)) >= 0) {
 190                                         while ((n = read(repFd, buf, sizeof(buf))) > 0) {
 191                                                 write(fd, buf, n);
 192                                         }
 193                                         close(fd);
 194                                         rename(path, pas->pw_name);
 195                                 } else {
 196                                         fprintf(stderr, "unable to create %s/%s: %s\n",
 197                                                         CDir,
 198                                                         path,
 199                                                         strerror(errno)
 200                                                    );
 201                                 }
 202                                 close(repFd);
 203                         }
 204                         break;
 205                 case DELETE:
 206                         remove(pas->pw_name);
 207                         break;
 208                 case NONE:
 209                 default:
 210                         break;
 211         }
 212
 213         /*
 214          *  Bump notification file.  Handle window where crond picks file up
 215          *  before we can write our entry out.
 216          */
 217
 218         if (option == REPLACE || option == DELETE) {
 219                 FILE *fo;
 220                 struct stat st;
 221
 222                 while ((fo = fopen(CRONUPDATE, "a"))) {
 223                         fprintf(fo, "%s\n", pas->pw_name);
 224                         fflush(fo);
 225                         if (fstat(fileno(fo), &st) != 0 || st.st_nlink != 0) {
 226                                 fclose(fo);
 227                                 break;
 228                         }
 229                         fclose(fo);
 230                         /* loop */
 231                 }
 232                 if (fo == NULL) {
 233                         fprintf(stderr, "unable to append to %s/%s\n", CDir, CRONUPDATE);
 234                 }
 235         }
 236         (volatile void)exit(0);
 237         /* not reached */
 238 }
 239
 240 int
 241 GetReplaceStream(const char *user, const char *file)
 242 {
 243         int filedes[2];
 244         int pid;
 245         int fd;
 246         int n;
 247         char buf[1024];
 248
 249         if (pipe(filedes) < 0) {
 250                 perror("pipe");
 251                 return(-1);
 252         }
 253         if ((pid = fork()) < 0) {
 254                 perror("fork");
 255                 return(-1);
 256         }
 257         if (pid > 0) {
 258                 /*
 259                  * PARENT
 260                  */
 261
 262                 close(filedes[1]);
 263                 if (read(filedes[0], buf, 1) != 1) {
 264                         close(filedes[0]);
 265                         filedes[0] = -1;
 266                 }
 267                 return(filedes[0]);
 268         }
 269
 270         /*
 271          * CHILD
 272          */
 273
 274         close(filedes[0]);
 275
 276         if (ChangeUser(user, 0) < 0)
 277                 exit(0);
 278
 279         fd = open(file, O_RDONLY);
 280         if (fd < 0)
 281                 errx(0, "unable to open %s", file);
 282         buf[0] = 0;
 283         write(filedes[1], buf, 1);
 284         while ((n = read(fd, buf, sizeof(buf))) > 0) {
 285                 write(filedes[1], buf, n);
 286         }
 287         exit(0);
 288 }
 289
 290 void
 291 EditFile(const char *user, const char *file)
 292 {
 293         int pid;
 294
 295         if ((pid = fork()) == 0) {
 296                 /*
 297                  * CHILD - change user and run editor
 298                  */
 299                 const char *ptr;
 300                 char visual[1024];
 301
 302                 if (ChangeUser(user, 1) < 0)
 303                         exit(0);
 304                 if ((ptr = getenv("EDITOR")) == NULL || strlen(ptr) > 256)
 305                         if ((ptr = getenv("VISUAL")) == NULL || strlen(ptr) > 256)
 306                                 ptr = PATH_VI;
 307
 308                 snprintf(visual, sizeof(visual), "%s %s", ptr, file);
 309                 execl("/bin/sh", "/bin/sh", "-c", visual, NULL);
 310                 perror("exec");
 311                 exit(0);
 312         }
 313         if (pid < 0) {
 314                 /*
 315                  * PARENT - failure
 316                  */
 317                 perror("fork");
 318                 exit(1);
 319         }
 320         wait4(pid, NULL, 0, NULL);
 321 }
 322