crontab: almost complete rewrite
crontab: make options consistent with other implementations text data bss dec hex filename 2042 4 0 2046 7fe busybox.t1/miscutils/crontab.o 1331 0 0 1331 533 busybox.t2/miscutils/crontab.o function old new delta edit_file 733 956 +223 open_as_user - 171 +171 packed_usage 23652 23650 -2 CDir 8 4 -4 ChangeUser 139 - -139 crontab_main 1522 616 -906 ------------------------------------------------------------------------------ (add/remove: 1/1 grow/shrink: 1/3 up/down: 394/-1051) Total: -657 bytes
This commit is contained in:
Denis Vlasenko
@@ -510,15 +510,14 @@ USE_FEATURE_BRCTL_FANCY("\n" \
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" -c dir Working dir"
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#define crontab_trivial_usage \
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"[-c dir] {file|-}|[-u|-l|-e|-d user]"
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"[-c DIR] [-u USER] [-ler]|[FILE]"
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#define crontab_full_usage \
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" file [opts] Replace crontab from file\n" \
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" - [opts] Replace crontab from stdin\n" \
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" -u user User\n" \
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" -l [user] List crontab for user\n" \
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" -e [user] Edit crontab for user\n" \
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" -d [user] Delete crontab for user\n" \
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" -c dir Crontab directory"
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" -c Crontab directory" \
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"\n -u User" \
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"\n -l List crontab" \
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"\n -e Edit crontab" \
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"\n -r Delete crontab" \
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"\n FILE Replace crontab by FILE ('-': stdin)" \
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#define cryptpw_trivial_usage \
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"[-a des|md5] [string]"
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@@ -25,321 +25,225 @@
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#define PATH_VI "/bin/vi" /* location of vi */
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#endif
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static const char *CDir = CRONTABS;
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static void EditFile(const char *user, const char *file);
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static int GetReplaceStream(const char *user, const char *file);
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static int ChangeUser(const char *user, short dochdir);
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int crontab_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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int crontab_main(int ac, char **av)
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static void change_user(const struct passwd *pas)
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{
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enum { NONE, EDIT, LIST, REPLACE, DELETE } option = NONE;
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const struct passwd *pas;
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const char *repFile = NULL;
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int repFd = 0;
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int i;
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char caller[256]; /* user that ran program */
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char buf[1024];
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int UserId;
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UserId = getuid();
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pas = getpwuid(UserId);
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if (pas == NULL)
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bb_perror_msg_and_die("getpwuid");
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safe_strncpy(caller, pas->pw_name, sizeof(caller));
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i = 1;
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if (ac > 1) {
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if (LONE_DASH(av[1])) {
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option = REPLACE;
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++i;
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} else if (av[1][0] != '-') {
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option = REPLACE;
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++i;
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repFile = av[1];
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}
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}
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for (; i < ac; ++i) {
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char *ptr = av[i];
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if (*ptr != '-')
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break;
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ptr += 2;
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switch (ptr[-1]) {
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case 'l':
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if (ptr[-1] == 'l')
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option = LIST;
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/* fall through */
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case 'e':
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if (ptr[-1] == 'e')
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option = EDIT;
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/* fall through */
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case 'd':
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if (ptr[-1] == 'd')
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option = DELETE;
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/* fall through */
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case 'u':
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if (i + 1 < ac && av[i+1][0] != '-') {
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++i;
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if (getuid() == geteuid()) {
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pas = getpwnam(av[i]);
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if (pas) {
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UserId = pas->pw_uid;
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} else {
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bb_error_msg_and_die("user %s unknown", av[i]);
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}
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} else {
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bb_error_msg_and_die("only the superuser may specify a user");
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}
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}
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break;
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case 'c':
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if (getuid() == geteuid()) {
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CDir = (*ptr) ? ptr : av[++i];
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} else {
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bb_error_msg_and_die("-c option: superuser only");
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}
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break;
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default:
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i = ac;
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break;
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}
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}
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if (i != ac || option == NONE)
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bb_show_usage();
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/*
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* Get password entry
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*/
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pas = getpwuid(UserId);
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if (pas == NULL)
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bb_perror_msg_and_die("getpwuid");
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/*
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* If there is a replacement file, obtain a secure descriptor to it.
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*/
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if (repFile) {
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repFd = GetReplaceStream(caller, repFile);
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if (repFd < 0)
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bb_error_msg_and_die("cannot read replacement file");
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}
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/*
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* Change directory to our crontab directory
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*/
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xchdir(CDir);
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/*
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* Handle options as appropriate
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*/
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switch (option) {
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case LIST:
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{
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FILE *fi;
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fi = fopen(pas->pw_name, "r");
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if (fi) {
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while (fgets(buf, sizeof(buf), fi) != NULL)
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fputs(buf, stdout);
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fclose(fi);
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} else {
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bb_error_msg("no crontab for %s", pas->pw_name);
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}
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}
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break;
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case EDIT:
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{
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/* FIXME: messy code here! we have file copying helpers for this! */
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FILE *fi;
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int fd;
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int n;
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char tmp[128];
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snprintf(tmp, sizeof(tmp), TMPDIR "/crontab.%d", getpid());
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fd = xopen3(tmp, O_RDWR|O_CREAT|O_TRUNC|O_EXCL, 0600);
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/* race, use fchown */
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chown(tmp, getuid(), getgid());
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fi = fopen(pas->pw_name, "r");
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if (fi) {
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while ((n = fread(buf, 1, sizeof(buf), fi)) > 0)
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full_write(fd, buf, n);
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}
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EditFile(caller, tmp);
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remove(tmp);
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lseek(fd, 0L, SEEK_SET);
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repFd = fd;
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}
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option = REPLACE;
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/* fall through */
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case REPLACE:
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{
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/* same here */
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char path[1024];
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int fd;
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int n;
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snprintf(path, sizeof(path), "%s.new", pas->pw_name);
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fd = open(path, O_CREAT|O_TRUNC|O_APPEND|O_WRONLY, 0600);
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if (fd >= 0) {
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while ((n = read(repFd, buf, sizeof(buf))) > 0) {
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full_write(fd, buf, n);
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}
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close(fd);
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rename(path, pas->pw_name);
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} else {
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bb_error_msg("cannot create %s/%s", CDir, path);
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}
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close(repFd);
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}
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break;
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case DELETE:
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remove(pas->pw_name);
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break;
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case NONE:
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default:
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break;
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}
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/*
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* Bump notification file. Handle window where crond picks file up
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* before we can write our entry out.
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*/
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if (option == REPLACE || option == DELETE) {
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FILE *fo;
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struct stat st;
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while ((fo = fopen(CRONUPDATE, "a"))) {
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fprintf(fo, "%s\n", pas->pw_name);
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fflush(fo);
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if (fstat(fileno(fo), &st) != 0 || st.st_nlink != 0) {
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fclose(fo);
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break;
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}
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fclose(fo);
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/* loop */
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}
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if (fo == NULL) {
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bb_error_msg("cannot append to %s/%s", CDir, CRONUPDATE);
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}
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}
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return 0;
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}
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static int GetReplaceStream(const char *user, const char *file)
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{
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int filedes[2];
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int pid;
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int fd;
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int n;
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char buf[1024];
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if (pipe(filedes) < 0) {
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perror("pipe");
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return -1;
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}
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pid = fork();
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if (pid < 0) {
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perror("fork");
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return -1;
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}
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if (pid > 0) {
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/*
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* PARENT
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*/
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close(filedes[1]);
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if (read(filedes[0], buf, 1) != 1) {
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close(filedes[0]);
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filedes[0] = -1;
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}
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return filedes[0];
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}
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/*
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* CHILD
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*/
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close(filedes[0]);
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if (ChangeUser(user, 0) < 0)
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exit(0);
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xfunc_error_retval = 0;
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fd = xopen(file, O_RDONLY);
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buf[0] = 0;
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write(filedes[1], buf, 1);
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while ((n = read(fd, buf, sizeof(buf))) > 0) {
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write(filedes[1], buf, n);
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}
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exit(0);
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}
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static void EditFile(const char *user, const char *file)
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{
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int pid = fork();
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if (pid == 0) {
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/*
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* CHILD - change user and run editor
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*/
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const char *ptr;
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if (ChangeUser(user, 1) < 0)
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exit(0);
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ptr = getenv("VISUAL");
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if (ptr == NULL)
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ptr = getenv("EDITOR");
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if (ptr == NULL)
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ptr = PATH_VI;
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ptr = xasprintf("%s %s", ptr, file);
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execl(DEFAULT_SHELL, DEFAULT_SHELL, "-c", ptr, NULL);
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bb_perror_msg_and_die("exec");
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}
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if (pid < 0) {
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/*
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* PARENT - failure
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*/
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bb_perror_msg_and_die("fork");
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}
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wait4(pid, NULL, 0, NULL);
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}
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static int ChangeUser(const char *user, short dochdir)
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{
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struct passwd *pas;
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/*
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* Obtain password entry and change privileges
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*/
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pas = getpwnam(user);
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if (pas == NULL) {
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bb_perror_msg_and_die("cannot get uid for %s", user);
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}
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setenv("USER", pas->pw_name, 1);
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setenv("HOME", pas->pw_dir, 1);
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setenv("SHELL", DEFAULT_SHELL, 1);
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/*
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* Change running state to the user in question
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*/
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/* initgroups, setgid, setuid */
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change_identity(pas);
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if (dochdir) {
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if (chdir(pas->pw_dir) < 0) {
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bb_perror_msg("chdir(%s) by %s failed", pas->pw_dir, user);
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xchdir(TMPDIR);
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if (chdir(pas->pw_dir) < 0) {
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bb_perror_msg("chdir(%s) by %s failed",
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pas->pw_dir, pas->pw_name);
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xchdir(TMPDIR);
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}
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}
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static void edit_file(const struct passwd *pas, const char *file)
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{
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const char *ptr;
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int pid = vfork();
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if (pid < 0) /* failure */
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bb_perror_msg_and_die("vfork");
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if (pid) { /* parent */
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wait4pid(pid);
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return;
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}
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/* CHILD - change user and run editor */
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change_user(pas);
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ptr = getenv("VISUAL");
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if (!ptr) {
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ptr = getenv("EDITOR");
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if (!ptr)
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ptr = PATH_VI;
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}
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/* TODO: clean up the environment!!! */
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/* not execlp - we won't use PATH */
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execl(ptr, ptr, file, NULL);
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bb_perror_msg_and_die("exec %s", ptr);
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}
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static int open_as_user(const struct passwd *pas, const char *file)
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{
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int filedes[2];
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pid_t pid;
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char c;
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xpipe(filedes);
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pid = vfork();
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if (pid < 0) /* ERROR */
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bb_perror_msg_and_die("vfork");
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if (pid) { /* PARENT */
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int n = safe_read(filedes[0], &c, 1);
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close(filedes[0]);
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close(filedes[1]);
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if (n > 0) /* child says it can read */
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return open(file, O_RDONLY);
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return -1;
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}
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/* CHILD */
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/* initgroups, setgid, setuid */
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change_identity(pas);
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/* We just try to read one byte. If that works, file is readable
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* under this user. We signal that by sending one byte to parent. */
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if (safe_read(xopen(file, O_RDONLY), &c, 1) == 1)
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safe_write(filedes[1], &c, 1); /* "papa, I can read!" */
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_exit(0);
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}
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int crontab_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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int crontab_main(int argc, char **argv)
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{
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const struct passwd *pas;
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const char *crontab_dir = CRONTABS;
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char *tmp_fname;
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char *new_fname;
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char *user_name; /* -u USER */
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int fd;
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int opt_ler;
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uid_t my_uid;
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/* file [opts] Replace crontab from file
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* - [opts] Replace crontab from stdin
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* -u user User
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* -c dir Crontab directory
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* -l List crontab for user
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* -e Edit crontab for user
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* -r Delete crontab for user
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* bbox also supports -d == -r, but most other crontab
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* implementations do not. Deprecated.
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*/
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enum {
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OPT_u = (1 << 0),
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OPT_c = (1 << 1),
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OPT_l = (1 << 2),
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OPT_e = (1 << 3),
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OPT_r = (1 << 4),
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OPT_ler = OPT_l + OPT_e + OPT_r,
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};
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my_uid = getuid();
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opt_complementary = "?1:dr"; /* max one argument; -d implies -r */
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opt_ler = getopt32(argv, "u:c:lerd", &user_name, &crontab_dir);
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argv += optind;
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if (opt_ler & (OPT_u|OPT_c))
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if (my_uid != geteuid())
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bb_error_msg_and_die("only root can use -c or -u");
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if (opt_ler & OPT_u) {
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pas = getpwnam(user_name);
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if (!pas)
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bb_error_msg_and_die("user %s is not known", user_name);
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my_uid = pas->pw_uid;
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} else {
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pas = getpwuid(my_uid);
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if (!pas)
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bb_perror_msg_and_die("no user record for UID %u",
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(unsigned)my_uid);
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}
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#define user_name DONT_USE_ME_BEYOND_THIS_POINT
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#define my_uid DONT_USE_ME_BEYOND_THIS_POINT
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/* From now on, keep only -l, -e, -r bits */
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opt_ler &= OPT_ler;
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if ((opt_ler - 1) & opt_ler) /* more than one bit set? */
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bb_show_usage();
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/* Read replacement file under user's UID/GID/group vector */
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if (!opt_ler) { /* Replace? */
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if (!argv[0])
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bb_show_usage();
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if (NOT_LONE_DASH(argv[0])) {
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fd = open_as_user(pas, argv[0]);
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if (fd < 0)
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bb_error_msg_and_die("user %s cannot read %s",
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pas->pw_name, argv[0]);
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xmove_fd(fd, STDIN_FILENO);
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}
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}
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return pas->pw_uid;
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/* cd to our crontab directory */
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xchdir(crontab_dir);
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tmp_fname = NULL;
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/* Handle requested operation */
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switch (opt_ler) {
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default: /* case OPT_r: Delete */
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remove(pas->pw_name);
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break;
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case OPT_l: /* List */
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{
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char *args[2] = { pas->pw_name, NULL };
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return bb_cat(args);
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/* list exits,
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* the rest go play with cron update file */
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}
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case OPT_e: /* Edit */
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tmp_fname = xasprintf(TMPDIR "/crontab.%u", (unsigned)getpid());
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fd = xopen3(tmp_fname, O_RDWR|O_CREAT|O_TRUNC|O_EXCL, 0600);
|
||||
xmove_fd(fd, STDIN_FILENO);
|
||||
fd = open(pas->pw_name, O_RDONLY);
|
||||
if (fd >= 0) {
|
||||
bb_copyfd_eof(fd, STDIN_FILENO);
|
||||
close(fd);
|
||||
}
|
||||
fchown(STDIN_FILENO, pas->pw_uid, pas->pw_gid);
|
||||
edit_file(pas, tmp_fname);
|
||||
xlseek(STDIN_FILENO, 0, SEEK_SET);
|
||||
/* fall through */
|
||||
|
||||
case 0: /* Replace (no -l, -e, or -r were given) */
|
||||
new_fname = xasprintf("%s.new", pas->pw_name);
|
||||
fd = open(new_fname, O_WRONLY|O_CREAT|O_TRUNC|O_APPEND, 0600);
|
||||
if (fd >= 0) {
|
||||
bb_copyfd_eof(STDIN_FILENO, fd);
|
||||
close(fd);
|
||||
rename(new_fname, pas->pw_name);
|
||||
} else {
|
||||
bb_error_msg("cannot create %s/%s",
|
||||
crontab_dir, new_fname);
|
||||
}
|
||||
if (tmp_fname)
|
||||
remove(tmp_fname);
|
||||
/*free(tmp_fname);*/
|
||||
/*free(new_fname);*/
|
||||
|
||||
} /* switch */
|
||||
|
||||
/* Bump notification file. Handle window where crond picks file up
|
||||
* before we can write our entry out.
|
||||
*/
|
||||
while ((fd = open(CRONUPDATE, O_WRONLY|O_CREAT|O_APPEND)) >= 0) {
|
||||
struct stat st;
|
||||
|
||||
fdprintf(fd, "%s\n", pas->pw_name);
|
||||
if (fstat(fd, &st) != 0 || st.st_nlink != 0) {
|
||||
/*close(fd);*/
|
||||
break;
|
||||
}
|
||||
/* st.st_nlink == 0:
|
||||
* file was deleted, maybe crond missed our notification */
|
||||
close(fd);
|
||||
/* loop */
|
||||
}
|
||||
if (fd < 0) {
|
||||
bb_error_msg("cannot append to %s/%s",
|
||||
crontab_dir, CRONUPDATE);
|
||||
}
|
||||
return 0;
|
||||
}
|
||||
|
||||
Reference in New Issue
Block a user