libexec/crond/database.c

#if !defined(lint) && !defined(LINT)
static char rcsid[] = "$Header: database.c,v 2.1 90/07/18 00:23:51 vixie Exp $";
#endif

/* vix 26jan87 [RCS has the log]
 */

/* Copyright 1988,1990 by Paul Vixie
 * All rights reserved
 *
 * Distribute freely, except: don't remove my name from the source or
 * documentation (don't take credit for my work), mark your changes (don't
 * get me blamed for your possible bugs), don't alter or remove this
 * notice.  May be sold if buildable source is provided to buyer.  No
 * warrantee of any kind, express or implied, is included with this
 * software; use at your own risk, responsibility for damages (if any) to
 * anyone resulting from the use of this software rests entirely with the
 * user.
 *
 * Send bug reports, bug fixes, enhancements, requests, flames, etc., and
 * I'll try to keep a version up to date.  I can be reached as follows:
 * Paul Vixie, 329 Noe Street, San Francisco, CA, 94114, (415) 864-7013,
 * paul@vixie.sf.ca.us || {hoptoad,pacbell,decwrl,crash}!vixie!paul
 */


#include "cron.h"
#include <pwd.h>
#if defined(BSD)
# include <sys/file.h>
# include <sys/dir.h>
#endif
#if defined(ATT)
# include <sys/file.h>
# include <ndir.h>
# include <fcntl.h>
#endif


extern void     perror(), exit();


void
load_database(old_db)
        cron_db         *old_db;
{
        extern void     link_user(), unlink_user(), free_user();
        extern user     *load_user(), *find_user();
        extern char     *env_get();

        static DIR      *dir = NULL;

        struct stat     statbuf;
        struct direct   *dp;
        cron_db         new_db;
        user            *u;

        Debug(DLOAD, ("[%d] load_database()\n", getpid()))

        /* before we start loading any data, do a stat on SPOOL_DIR
         * so that if anything changes as of this moment (i.e., before we've
         * cached any of the database), we'll see the changes next time.
         */
        if (stat(SPOOL_DIR, &statbuf) < OK)
        {
                log_it("CROND", getpid(), "STAT FAILED", SPOOL_DIR);
                (void) exit(ERROR_EXIT);
        }

        /* if spooldir's mtime has not changed, we don't need to fiddle with
         * the database.  Note that if /etc/passwd changes (like, someone's
         * UID/GID/HOME/SHELL, we won't see it.  Maybe we should
         * keep an mtime for the passwd file?  HINT
         *
         * Note that old_db->mtime is initialized to 0 in main(), and
         * so is guaranteed to be different than the stat() mtime the first
         * time this function is called.
         */
        if (old_db->mtime == statbuf.st_mtime)
        {
                Debug(DLOAD, ("[%d] spool dir mtime unch, no load needed.\n",
                        getpid()))
                return;
        }

        /* make sure the dir is open.  only happens the first time, since
         * the DIR is static and we don't close it.  Rewind the dir.
         */
        if (dir == NULL)
        {
                if (!(dir = opendir(SPOOL_DIR)))
                {
                        log_it("CROND", getpid(), "OPENDIR FAILED", SPOOL_DIR);
                        (void) exit(ERROR_EXIT);
                }
        }
        (void) rewinddir(dir);

        /* something's different.  make a new database, moving unchanged
         * elements from the old database, reloading elements that have
         * actually changed.  Whatever is left in the old database when
         * we're done is chaff -- crontabs that disappeared.
         */
        new_db.mtime = statbuf.st_mtime;
        new_db.head = new_db.tail = NULL;

        while (NULL != (dp = readdir(dir)))
        {
                extern struct passwd    *getpwnam();
                struct passwd           *pw;
                int                     crontab_fd;
                char                    fname[MAXNAMLEN+1],
                                        tabname[MAXNAMLEN+1];

                (void) strncpy(fname, dp->d_name, (int) dp->d_namlen);
                fname[dp->d_namlen] = '\0';

                /* avoid file names beginning with ".".  this is good
                 * because we would otherwise waste two guaranteed calls
                 * to getpwnam() for . and .., and also because user names
                 * starting with a period are just too nasty to consider.
                 */
                if (fname[0] == '.')
                        goto next_crontab;

                if (NULL == (pw = getpwnam(fname)))
                {
                        /* file doesn't have a user in passwd file.
                         */
                        log_it(fname, getpid(), "ORPHAN", "no passwd entry");
                        goto next_crontab;
                }

                sprintf(tabname, CRON_TAB(fname));
                if ((crontab_fd = open(tabname, O_RDONLY, 0)) < OK)
                {
                        /* crontab not accessible?
                         */
                        log_it(fname, getpid(), "CAN'T OPEN", tabname);
                        goto next_crontab;
                }

                if (fstat(crontab_fd, &statbuf) < OK)
                {
                        log_it(fname, getpid(), "FSTAT FAILED", tabname);
                        goto next_crontab;
                }

                Debug(DLOAD, ("\t%s:", fname))
                u = find_user(old_db, fname);
                if (u != NULL)
                {
                        /* if crontab has not changed since we last read it
                         * in, then we can just use our existing entry.
                         * note that we do not check for changes in the
                         * passwd entry (uid, home dir, etc).  HINT
                         */
                        if (u->mtime == statbuf.st_mtime)
                        {
                                Debug(DLOAD, (" [no change, using old data]"))
                                unlink_user(old_db, u);
                                link_user(&new_db, u);
                                goto next_crontab;
                        }

                        /* before we fall through to the code that will reload
                         * the user, let's deallocate and unlink the user in
                         * the old database.  This is more a point of memory
                         * efficiency than anything else, since all leftover
                         * users will be deleted from the old database when
                         * we finish with the crontab...
                         */
                        Debug(DLOAD, (" [delete old data]"))
                        unlink_user(old_db, u);
                        free_user(u);
                }
                u = load_user(
                        crontab_fd,
                        pw->pw_name,
                        pw->pw_uid,
                        pw->pw_gid,
                        pw->pw_dir,
                        pw->pw_shell
                );
                if (u != NULL)
                {
                        u->mtime = statbuf.st_mtime;
                        link_user(&new_db, u);
                }
next_crontab:
                if (crontab_fd >= OK) {
                        Debug(DLOAD, (" [done]\n"))
                        close(crontab_fd);
                }
        }
        /* if we don't do this, then when our children eventually call
         * getpwnam() in do_command.c's child_process to verify MAILTO=,
         * they will screw us up (and v-v).
         *
         * (this was lots of fun to find...)
         */
        endpwent();

        /* whatever's left in the old database is now junk.
         */
        Debug(DLOAD, ("unlinking old database:\n"))
        for (u = old_db->head;  u != NULL;  u = u->next)
        {
                Debug(DLOAD, ("\t%s\n", env_get(USERENV, u->envp)))
                unlink_user(old_db, u);
                free_user(u);
        }

        /* overwrite the database control block with the new one.
         */
        Debug(DLOAD, ("installing new database\n"))
#if defined(BSD)
        /* BSD has structure assignments */
        *old_db = new_db;
#endif
#if defined(ATT)
        /* ATT, well, I don't know.  Use memcpy(). */
        memcpy(old_db, &new_db, sizeof(cron_db));
#endif
        Debug(DLOAD, ("load_database is done\n"))
}


void
link_user(db, u)
        cron_db *db;
        user    *u;
{
        if (db->head == NULL)
                db->head = u;
        if (db->tail)
                db->tail->next = u;
        u->prev = db->tail;
        u->next = NULL;
        db->tail = u;
}


void
unlink_user(db, u)
        cron_db *db;
        user    *u;
{
        if (u->prev == NULL)
                db->head = u->next;
        else
                u->prev->next = u->next;

        if (u->next == NULL)
                db->tail = u->prev;
        else
                u->next->prev = u->prev;
}


user *
find_user(db, name)
        cron_db *db;
        char    *name;
{
        char    *env_get();
        user    *u;

        for (u = db->head;  u != NULL;  u = u->next)
                if (!strcmp(env_get(USERENV, u->envp), name))
                        break;
        return u;
}