path: root/src/lib/kadm5/srv/adb_openclose.c

/*
 * Copyright 1993 OpenVision Technologies, Inc., All Rights Reserved
 *
 * $Header$ 
 */

#if !defined(lint) && !defined(__CODECENTER__)
static char *rcsid = "$Header$";
#endif

#include	<sys/file.h>
#include	<fcntl.h>
#include	<unistd.h>
#include	"adb.h"
#include	<stdlib.h>

#define MAX_LOCK_TRIES 5

struct _locklist {
     osa_adb_lock_ent lockinfo;
     struct _locklist *next;
};

osa_adb_ret_t osa_adb_create_db(char *filename, char *lockfilename,
				int magic)
{
     int lf;
     DB *db;
     HASHINFO info;
     
     memset(&info, 0, sizeof(info));
     info.hash = NULL;
     info.bsize = 256;
     info.ffactor = 8;
     info.nelem = 25000;
     info.lorder = 0;
     db = dbopen(filename, O_RDWR | O_CREAT | O_EXCL, 0600, DB_HASH, &info);
     if (db == NULL)
	  return errno;
     if (db->close(db) < 0)
	  return errno;

     /* only create the lock file if we successfully created the db */
     lf = THREEPARAMOPEN(lockfilename, O_RDWR | O_CREAT | O_EXCL, 0600);
     if (lf == -1)
	  return errno;
     (void) close(lf);
     
     return OSA_ADB_OK;
}

osa_adb_ret_t osa_adb_destroy_db(char *filename, char *lockfilename,
				 int magic)
{
     /* the admin databases do not contain security-critical data */
     if (unlink(filename) < 0 ||
	 unlink(lockfilename) < 0)
	  return errno;
     return OSA_ADB_OK;
}

osa_adb_ret_t osa_adb_rename_db(char *filefrom, char *lockfrom,
				char *fileto, char *lockto, int magic)
{
     osa_adb_db_t fromdb, todb;
     osa_adb_ret_t ret;

     /* make sure todb exists */
     if ((ret = osa_adb_create_db(fileto, lockto, magic)) &&
	 ret != EEXIST)
	  return ret;

     if (ret = osa_adb_init_db(&fromdb, filefrom, lockfrom, magic))
	  return ret;
     if (ret = osa_adb_init_db(&todb, fileto, lockto, magic)) {
	  (void) osa_adb_fini_db(fromdb, magic);
	  return ret;
     }
     if (ret = osa_adb_get_lock(fromdb, OSA_ADB_PERMANENT)) {
	  (void) osa_adb_fini_db(fromdb, magic);
	  (void) osa_adb_fini_db(todb, magic);
	  return ret;
     }
     if (ret = osa_adb_get_lock(todb, OSA_ADB_PERMANENT)) {
	  (void) osa_adb_fini_db(fromdb, magic);
	  (void) osa_adb_fini_db(todb, magic);
	  return ret;
     }
     if (rename(filefrom, fileto) < 0) {
	  (void) osa_adb_fini_db(fromdb, magic);
	  (void) osa_adb_fini_db(todb, magic);
	  return errno;
     }
     /*
      * Do not release the lock on fromdb because it is being renamed
      * out of existence; no one can ever use it again.
      */
     if (ret = osa_adb_release_lock(todb)) {
	  (void) osa_adb_fini_db(fromdb, magic);
	  (void) osa_adb_fini_db(todb, magic);
	  return ret;
     }
	  
     (void) osa_adb_fini_db(fromdb, magic);
     (void) osa_adb_fini_db(todb, magic);
     return 0;
}

osa_adb_ret_t osa_adb_init_db(osa_adb_db_t *dbp, char *filename,
			      char *lockfilename, int magic)
{
     osa_adb_db_t db;
     static struct _locklist *locklist = NULL;
     struct _locklist *lockp;
     krb5_error_code code;
     
     if (dbp == NULL || filename == NULL)
	  return EINVAL;

     db = (osa_adb_princ_t) malloc(sizeof(osa_adb_db_ent));
     if (db == NULL)
	  return ENOMEM;

     memset(db, 0, sizeof(*db));
     db->info.hash = NULL;
     db->info.bsize = 256;
     db->info.ffactor = 8;
     db->info.nelem = 25000;
     db->info.lorder = 0;

     /*
      * A process is allowed to open the same database multiple times
      * and access it via different handles.  If the handles use
      * distinct lockinfo structures, things get confused: lock(A),
      * lock(B), release(B) will result in the kernel unlocking the
      * lock file but handle A will still think the file is locked.
      * Therefore, all handles using the same lock file must share a
      * single lockinfo structure.
      *
      * It is not sufficient to have a single lockinfo structure,
      * however, because a single process may also wish to open
      * multiple different databases simultaneously, with different
      * lock files.  This code used to use a single static lockinfo
      * structure, which means that the second database opened used
      * the first database's lock file.  This was Bad.
      *
      * We now maintain a linked list of lockinfo structures, keyed by
      * lockfilename.  An entry is added when this function is called
      * with a new lockfilename, and all subsequent calls with that
      * lockfilename use the existing entry, updating the refcnt.
      * When the database is closed with fini_db(), the refcnt is
      * decremented, and when it is zero the lockinfo structure is
      * freed and reset.  The entry in the linked list, however, is
      * never removed; it will just be reinitialized the next time
      * init_db is called with the right lockfilename.
      */

     /* find or create the lockinfo structure for lockfilename */
     lockp = locklist;
     while (lockp) {
	  if (strcmp(lockp->lockinfo.filename, lockfilename) == 0)
	       break;
	  else
	       lockp = lockp->next;
     }
     if (lockp == NULL) {
	  /* doesn't exist, create it, add to list */
	  lockp = (struct _locklist *) malloc(sizeof(*lockp));
	  if (lockp == NULL) {
	       free(db);
	       return ENOMEM;
	  }
	  memset(lockp, 0, sizeof(*lockp));
	  lockp->next = locklist;
	  locklist = lockp;
     }

     /* now initialize lockp->lockinfo if necessary */
     if (lockp->lockinfo.lockfile == NULL) {
	  if (code = krb5_init_context(&lockp->lockinfo.context)) {
	       free(db);
	       return((osa_adb_ret_t) code);
	  }

	  /*
	   * needs be open read/write so that write locking can work with
	   * POSIX systems
	   */
	  lockp->lockinfo.filename = strdup(lockfilename);
	  if ((lockp->lockinfo.lockfile = fopen(lockfilename, "r+")) == NULL) {
	       /*
		* maybe someone took away write permission so we could only
		* get shared locks?
		*/
	       if ((lockp->lockinfo.lockfile = fopen(lockfilename, "r"))
		   == NULL) {
		    free(db);
		    return OSA_ADB_NOLOCKFILE;
	       }
	  }
	  lockp->lockinfo.lockmode = lockp->lockinfo.lockcnt = 0;
     }

     /* lockp is set, lockinfo is initialized, update the reference count */
     db->lock = &lockp->lockinfo;
     db->lock->refcnt++;

     db->filename = strdup(filename);
     db->magic = magic;

     *dbp = db;
     
     return OSA_ADB_OK;
}

osa_adb_ret_t osa_adb_fini_db(osa_adb_db_t db, int magic)
{
     if (db->magic != magic)
	  return EINVAL;
     if (db->lock->refcnt == 0) {
	  /* barry says this can't happen */
	  return OSA_ADB_FAILURE;
     } else {
	  db->lock->refcnt--;
     }

     if (db->lock->refcnt == 0) {
	  /*
	   * Don't free db->lock->filename, it is used as a key to
	   * find the lockinfo entry in the linked list.  If the
	   * lockfile doesn't exist, we must be closing the database
	   * after trashing it.  This has to be allowed, so don't
	   * generate an error.
	   */
	  if (db->lock->lockmode != OSA_ADB_PERMANENT)
	       (void) fclose(db->lock->lockfile);
	  db->lock->lockfile = NULL;
	  krb5_free_context(db->lock->context);
     }

     db->magic = 0;
     free(db->filename);
     free(db);
     return OSA_ADB_OK;
}     
     
osa_adb_ret_t osa_adb_get_lock(osa_adb_db_t db, int mode)
{
     int tries, gotlock, perm, krb5_mode, ret;

     if (db->lock->lockmode >= mode) {
	  /* No need to upgrade lock, just incr refcnt and return */
	  db->lock->lockcnt++;
	  return(OSA_ADB_OK);
     }

     perm = 0;
     switch (mode) {
	case OSA_ADB_PERMANENT:
	  perm = 1;
	case OSA_ADB_EXCLUSIVE:
	  krb5_mode = KRB5_LOCKMODE_EXCLUSIVE;
	  break;
	case OSA_ADB_SHARED:
	  krb5_mode = KRB5_LOCKMODE_SHARED;
	  break;
	default:
	  return(EINVAL);
     }

     for (gotlock = tries = 0; tries < MAX_LOCK_TRIES; tries++) {
	  if ((ret = krb5_lock_file(db->lock->context,
				    fileno(db->lock->lockfile),
				    krb5_mode|KRB5_LOCKMODE_DONTBLOCK)) == 0) {
	       gotlock++;
	       break;
	  } else if (ret == EBADF && mode == OSA_ADB_EXCLUSIVE)
	       /* tried to exclusive-lock something we don't have */
	       /* write access to */
	       return OSA_ADB_NOEXCL_PERM;

	  sleep(1);
     }

     /* test for all the likely "can't get lock" error codes */
     if (ret == EACCES || ret == EAGAIN || ret == EWOULDBLOCK)
	  return OSA_ADB_CANTLOCK_DB;
     else if (ret != 0)
	  return ret;

     /*
      * If the file no longer exists, someone acquired a permanent
      * lock.  If that process terminates its exclusive lock is lost,
      * but if we already had the file open we can (probably) lock it
      * even though it has been unlinked.  So we need to insist that
      * it exist.
      */
     if (access(db->lock->filename, F_OK) < 0) {
	  (void) krb5_lock_file(db->lock->context,
				fileno(db->lock->lockfile),
				KRB5_LOCKMODE_UNLOCK);
	  return OSA_ADB_NOLOCKFILE;
     }
     
     /* we have the shared/exclusive lock */
     
     if (perm) {
	  if (unlink(db->lock->filename) < 0) {
	       int ret;

	       /* somehow we can't delete the file, but we already */
	       /* have the lock, so release it and return */

	       ret = errno;
	       (void) krb5_lock_file(db->lock->context,
				     fileno(db->lock->lockfile),
				     KRB5_LOCKMODE_UNLOCK);
	       
	       /* maybe we should return CANTLOCK_DB.. but that would */
	       /* look just like the db was already locked */
	       return ret;
	  }

	  /* this releases our exclusive lock.. which is okay because */
	  /* now no one else can get one either */
	  (void) fclose(db->lock->lockfile);
     }
     
     db->lock->lockmode = mode;
     db->lock->lockcnt++;
     return OSA_ADB_OK;
}

osa_adb_ret_t osa_adb_release_lock(osa_adb_db_t db)
{
     int ret, fd;
     
     if (!db->lock->lockcnt)		/* lock already unlocked */
	  return OSA_ADB_NOTLOCKED;

     if (--db->lock->lockcnt == 0) {
	  if (db->lock->lockmode == OSA_ADB_PERMANENT) {
	       /* now we need to create the file since it does not exist */
               fd = THREEPARAMOPEN(db->lock->filename,O_RDWR | O_CREAT | O_EXCL,
                                   0600);
	       if ((db->lock->lockfile = fdopen(fd, "w+")) == NULL)
		    return OSA_ADB_NOLOCKFILE;
	  } else if (ret = krb5_lock_file(db->lock->context,
					  fileno(db->lock->lockfile),
					  KRB5_LOCKMODE_UNLOCK))
	       return ret;
	  
	  db->lock->lockmode = 0;
     }
     return OSA_ADB_OK;
}

osa_adb_ret_t osa_adb_open_and_lock(osa_adb_princ_t db, int locktype)
{
     int ret;

     ret = osa_adb_get_lock(db, locktype);
     if (ret != OSA_ADB_OK)
	  return ret;
     
     db->db = dbopen(db->filename, O_RDWR, 0600, DB_HASH, &db->info);
     if (db->db == NULL) {
	  (void) osa_adb_release_lock(db);
	  if(errno == EINVAL)
	       return OSA_ADB_BAD_DB;
	  return errno;
     }
     return OSA_ADB_OK;
}

osa_adb_ret_t osa_adb_close_and_unlock(osa_adb_princ_t db)
{
     int ret;

     if(db->db->close(db->db) == -1) {
	  (void) osa_adb_release_lock(db);
	  return OSA_ADB_FAILURE;
     }

     db->db = NULL;

     return(osa_adb_release_lock(db));
}