346 lines
6.5 KiB
C
346 lines
6.5 KiB
C
/* vi: set sw=4 ts=4: */
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/*
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* CRONTAB
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*
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* usually setuid root, -c option only works if getuid() == geteuid()
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*
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* Copyright 1994 Matthew Dillon (dillon@apollo.west.oic.com)
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* Vladimir Oleynik <dzo@simtreas.ru> (C) 2002
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*
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* Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
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*/
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#include "libbb.h"
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#ifndef CRONTABS
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#define CRONTABS "/var/spool/cron/crontabs"
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#endif
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#ifndef TMPDIR
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#define TMPDIR "/var/spool/cron"
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#endif
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#ifndef CRONUPDATE
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#define CRONUPDATE "cron.update"
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#endif
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#ifndef PATH_VI
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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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{
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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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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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}
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}
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return pas->pw_uid;
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}
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