Adding upstream version 1:4.13+dfsg1.upstream/1%4.13+dfsg1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1276 insertions, 0 deletions

diff --git a/lib/commonio.c b/lib/commonio.c
new file mode 100644
index 0000000..9a02ce1
--- /dev/null
+++ b/lib/commonio.c
@@ -0,0 +1,1276 @@
+/*
+ * SPDX-FileCopyrightText: 1990 - 1994, Julianne Frances Haugh
+ * SPDX-FileCopyrightText: 1996 - 2001, Marek Michałkiewicz
+ * SPDX-FileCopyrightText: 2001 - 2006, Tomasz Kłoczko
+ * SPDX-FileCopyrightText: 2007 - 2011, Nicolas François
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <config.h>
+
+#ident "$Id$"
+
+#include "defines.h"
+#include <assert.h>
+#include <sys/stat.h>
+#include <stdlib.h>
+#include <limits.h>
+#include <utime.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <stdio.h>
+#include <signal.h>
+#include "nscd.h"
+#include "sssd.h"
+#ifdef WITH_TCB
+#include <tcb.h>
+#endif				/* WITH_TCB */
+#include "prototypes.h"
+#include "commonio.h"
+#include "shadowlog_internal.h"
+
+/* local function prototypes */
+static int lrename (const char *, const char *);
+static int check_link_count (const char *file, bool log);
+static int do_lock_file (const char *file, const char *lock, bool log);
+static /*@null@*/ /*@dependent@*/FILE *fopen_set_perms (
+	const char *name,
+	const char *mode,
+	const struct stat *sb);
+static int create_backup (const char *, FILE *);
+static void free_linked_list (struct commonio_db *);
+static void add_one_entry (
+	struct commonio_db *db,
+	/*@owned@*/struct commonio_entry *p);
+static bool name_is_nis (const char *name);
+static int write_all (const struct commonio_db *);
+static /*@dependent@*/ /*@null@*/struct commonio_entry *find_entry_by_name (
+	struct commonio_db *,
+	const char *);
+static /*@dependent@*/ /*@null@*/struct commonio_entry *next_entry_by_name (
+	struct commonio_db *,
+	/*@null@*/struct commonio_entry *pos,
+	const char *);
+
+static int lock_count = 0;
+static bool nscd_need_reload = false;
+
+/*
+ * Simple rename(P) alternative that attempts to rename to symlink
+ * target.
+ */
+int lrename (const char *old, const char *new)
+{
+	int res;
+	char *r = NULL;
+
+#ifndef __GLIBC__
+	char resolved_path[PATH_MAX];
+#endif				/* !__GLIBC__ */
+	struct stat sb;
+	if (lstat (new, &sb) == 0 && S_ISLNK (sb.st_mode)) {
+#ifdef __GLIBC__ /* now a POSIX.1-2008 feature */
+		r = realpath (new, NULL);
+#else				/* !__GLIBC__ */
+		r = realpath (new, resolved_path);
+#endif				/* !__GLIBC__ */
+		if (NULL == r) {
+			perror ("realpath in lrename()");
+		} else {
+			new = r;
+		}
+	}
+
+	res = rename (old, new);
+
+#ifdef __GLIBC__
+	free (r);
+#endif				/* __GLIBC__ */
+
+	return res;
+}
+
+static int check_link_count (const char *file, bool log)
+{
+	struct stat sb;
+
+	if (stat (file, &sb) != 0) {
+		if (log) {
+			(void) fprintf (shadow_logfd,
+			                "%s: %s file stat error: %s\n",
+			                shadow_progname, file, strerror (errno));
+		}
+		return 0;
+	}
+
+	if (sb.st_nlink != 2) {
+		if (log) {
+			(void) fprintf (shadow_logfd,
+			                "%s: %s: lock file already used (nlink: %u)\n",
+			                shadow_progname, file, sb.st_nlink);
+		}
+		return 0;
+	}
+
+	return 1;
+}
+
+
+static int do_lock_file (const char *file, const char *lock, bool log)
+{
+	int fd;
+	pid_t pid;
+	ssize_t len;
+	int retval;
+	char buf[32];
+
+	fd = open (file, O_CREAT | O_TRUNC | O_WRONLY, 0600);
+	if (-1 == fd) {
+		if (log) {
+			(void) fprintf (shadow_logfd,
+			                "%s: %s: %s\n",
+			                shadow_progname, file, strerror (errno));
+		}
+		return 0;
+	}
+
+	pid = getpid ();
+	snprintf (buf, sizeof buf, "%lu", (unsigned long) pid);
+	len = (ssize_t) strlen (buf) + 1;
+	if (write (fd, buf, (size_t) len) != len) {
+		if (log) {
+			(void) fprintf (shadow_logfd,
+			                "%s: %s file write error: %s\n",
+			                shadow_progname, file, strerror (errno));
+		}
+		(void) close (fd);
+		unlink (file);
+		return 0;
+	}
+	if (fdatasync (fd) == -1) {
+		if (log) {
+			(void) fprintf (shadow_logfd,
+			                "%s: %s file sync error: %s\n",
+			                shadow_progname, file, strerror (errno));
+		}
+		(void) close (fd);
+		unlink (file);
+		return 0;
+	}
+	close (fd);
+
+	if (link (file, lock) == 0) {
+		retval = check_link_count (file, log);
+		unlink (file);
+		return retval;
+	}
+
+	fd = open (lock, O_RDWR);
+	if (-1 == fd) {
+		if (log) {
+			(void) fprintf (shadow_logfd,
+			                "%s: %s: %s\n",
+			                shadow_progname, lock, strerror (errno));
+		}
+		unlink (file);
+		errno = EINVAL;
+		return 0;
+	}
+	len = read (fd, buf, sizeof (buf) - 1);
+	close (fd);
+	if (len <= 0) {
+		if (log) {
+			(void) fprintf (shadow_logfd,
+			                "%s: existing lock file %s without a PID\n",
+			                shadow_progname, lock);
+		}
+		unlink (file);
+		errno = EINVAL;
+		return 0;
+	}
+	buf[len] = '\0';
+	if (get_pid (buf, &pid) == 0) {
+		if (log) {
+			(void) fprintf (shadow_logfd,
+			                "%s: existing lock file %s with an invalid PID '%s'\n",
+			                shadow_progname, lock, buf);
+		}
+		unlink (file);
+		errno = EINVAL;
+		return 0;
+	}
+	if (kill (pid, 0) == 0) {
+		if (log) {
+			(void) fprintf (shadow_logfd,
+			                "%s: lock %s already used by PID %lu\n",
+			                shadow_progname, lock, (unsigned long) pid);
+		}
+		unlink (file);
+		errno = EEXIST;
+		return 0;
+	}
+	if (unlink (lock) != 0) {
+		if (log) {
+			(void) fprintf (shadow_logfd,
+			                "%s: cannot get lock %s: %s\n",
+			                shadow_progname, lock, strerror (errno));
+		}
+		unlink (file);
+		return 0;
+	}
+
+	retval = 0;
+	if (link (file, lock) == 0) {
+		retval = check_link_count (file, log);
+	} else {
+		if (log) {
+			(void) fprintf (shadow_logfd,
+			                "%s: cannot get lock %s: %s\n",
+			                shadow_progname, lock, strerror (errno));
+		}
+	}
+
+	unlink (file);
+	return retval;
+}
+
+
+static /*@null@*/ /*@dependent@*/FILE *fopen_set_perms (
+	const char *name,
+	const char *mode,
+	const struct stat *sb)
+{
+	FILE *fp;
+	mode_t mask;
+
+	mask = umask (0777);
+	fp = fopen (name, mode);
+	(void) umask (mask);
+	if (NULL == fp) {
+		return NULL;
+	}
+
+#ifdef HAVE_FCHOWN
+	if (fchown (fileno (fp), sb->st_uid, sb->st_gid) != 0) {
+		goto fail;
+	}
+#else				/* !HAVE_FCHOWN */
+	if (chown (name, sb->st_mode) != 0) {
+		goto fail;
+	}
+#endif				/* !HAVE_FCHOWN */
+
+#ifdef HAVE_FCHMOD
+	if (fchmod (fileno (fp), sb->st_mode & 0664) != 0) {
+		goto fail;
+	}
+#else				/* !HAVE_FCHMOD */
+	if (chmod (name, sb->st_mode & 0664) != 0) {
+		goto fail;
+	}
+#endif				/* !HAVE_FCHMOD */
+	return fp;
+
+      fail:
+	(void) fclose (fp);
+	/* fopen_set_perms is used for intermediate files */
+	(void) unlink (name);
+	return NULL;
+}
+
+
+static int create_backup (const char *backup, FILE * fp)
+{
+	struct stat sb;
+	struct utimbuf ub;
+	FILE *bkfp;
+	int c;
+
+	if (fstat (fileno (fp), &sb) != 0) {
+		return -1;
+	}
+
+	bkfp = fopen_set_perms (backup, "w", &sb);
+	if (NULL == bkfp) {
+		return -1;
+	}
+
+	/* TODO: faster copy, not one-char-at-a-time.  --marekm */
+	c = 0;
+	if (fseek (fp, 0, SEEK_SET) == 0) {
+		while ((c = getc (fp)) != EOF) {
+			if (putc (c, bkfp) == EOF) {
+				break;
+			}
+		}
+	}
+	if ((c != EOF) || (ferror (fp) != 0) || (fflush (bkfp) != 0)) {
+		(void) fclose (bkfp);
+		/* FIXME: unlink the backup file? */
+		return -1;
+	}
+	if (fsync (fileno (bkfp)) != 0) {
+		(void) fclose (bkfp);
+		/* FIXME: unlink the backup file? */
+		return -1;
+	}
+	if (fclose (bkfp) != 0) {
+		/* FIXME: unlink the backup file? */
+		return -1;
+	}
+
+	ub.actime = sb.st_atime;
+	ub.modtime = sb.st_mtime;
+	(void) utime (backup, &ub);
+	return 0;
+}
+
+
+static void free_linked_list (struct commonio_db *db)
+{
+	struct commonio_entry *p;
+
+	while (NULL != db->head) {
+		p = db->head;
+		db->head = p->next;
+
+		free (p->line);
+
+		if (NULL != p->eptr) {
+			db->ops->free (p->eptr);
+		}
+
+		free (p);
+	}
+	db->tail = NULL;
+}
+
+
+int commonio_setname (struct commonio_db *db, const char *name)
+{
+	snprintf (db->filename, sizeof (db->filename), "%s", name);
+	db->setname = true;
+	return 1;
+}
+
+
+bool commonio_present (const struct commonio_db *db)
+{
+	return (access (db->filename, F_OK) == 0);
+}
+
+
+int commonio_lock_nowait (struct commonio_db *db, bool log)
+{
+	char* file = NULL;
+	char* lock = NULL;
+	size_t lock_file_len;
+	size_t file_len;
+	int err = 0;
+
+	if (db->locked) {
+		return 1;
+	}
+	file_len = strlen(db->filename) + 11;/* %lu max size */
+	lock_file_len = strlen(db->filename) + 6; /* sizeof ".lock" */
+	file = (char*)malloc(file_len);
+	if (file == NULL) {
+		goto cleanup_ENOMEM;
+	}
+	lock = (char*)malloc(lock_file_len);
+	if (lock == NULL) {
+		goto cleanup_ENOMEM;
+	}
+	snprintf (file, file_len, "%s.%lu",
+	          db->filename, (unsigned long) getpid ());
+	snprintf (lock, lock_file_len, "%s.lock", db->filename);
+	if (do_lock_file (file, lock, log) != 0) {
+		db->locked = true;
+		lock_count++;
+		err = 1;
+	}
+cleanup_ENOMEM:
+	free(file);
+	free(lock);
+	return err;
+}
+
+
+int commonio_lock (struct commonio_db *db)
+{
+	int i;
+
+#ifdef HAVE_LCKPWDF
+	/*
+	 * Only if the system libc has a real lckpwdf() - the one from
+	 * lockpw.c calls us and would cause infinite recursion!
+	 * It is also not used with the prefix option.
+	 */
+	if (!db->setname) {
+		/*
+		 * Call lckpwdf() on the first lock.
+		 * If it succeeds, call *_lock() only once
+		 * (no retries, it should always succeed).
+		 */
+		if (0 == lock_count) {
+			if (lckpwdf () == -1) {
+				if (geteuid () != 0) {
+					(void) fprintf (shadow_logfd,
+					                "%s: Permission denied.\n",
+					                shadow_progname);
+				}
+				return 0;	/* failure */
+			}
+		}
+
+		if (commonio_lock_nowait (db, true) != 0) {
+			return 1;	/* success */
+		}
+
+		ulckpwdf ();
+		return 0;		/* failure */
+	}
+#endif				/* !HAVE_LCKPWDF */
+
+	/*
+	 * lckpwdf() not used - do it the old way.
+	 */
+#ifndef LOCK_TRIES
+#define LOCK_TRIES 15
+#endif
+
+#ifndef LOCK_SLEEP
+#define LOCK_SLEEP 1
+#endif
+	for (i = 0; i < LOCK_TRIES; i++) {
+		if (i > 0) {
+			sleep (LOCK_SLEEP);	/* delay between retries */
+		}
+		if (commonio_lock_nowait (db, i==LOCK_TRIES-1) != 0) {
+			return 1;	/* success */
+		}
+		/* no unnecessary retries on "permission denied" errors */
+		if (geteuid () != 0) {
+			(void) fprintf (shadow_logfd, "%s: Permission denied.\n",
+			                shadow_progname);
+			return 0;
+		}
+	}
+	return 0;		/* failure */
+}
+
+static void dec_lock_count (void)
+{
+	if (lock_count > 0) {
+		lock_count--;
+		if (lock_count == 0) {
+			/* Tell nscd when lock count goes to zero,
+			   if any of the files were changed.  */
+			if (nscd_need_reload) {
+				nscd_flush_cache ("passwd");
+				nscd_flush_cache ("group");
+				sssd_flush_cache (SSSD_DB_PASSWD | SSSD_DB_GROUP);
+				nscd_need_reload = false;
+			}
+#ifdef HAVE_LCKPWDF
+			ulckpwdf ();
+#endif				/* HAVE_LCKPWDF */
+		}
+	}
+}
+
+
+int commonio_unlock (struct commonio_db *db)
+{
+	char lock[1024];
+
+	if (db->isopen) {
+		db->readonly = true;
+		if (commonio_close (db) == 0) {
+			if (db->locked) {
+				dec_lock_count ();
+			}
+			return 0;
+		}
+	}
+	if (db->locked) {
+		/*
+		 * Unlock in reverse order: remove the lock file,
+		 * then call ulckpwdf() (if used) on last unlock.
+		 */
+		db->locked = false;
+		snprintf (lock, sizeof lock, "%s.lock", db->filename);
+		unlink (lock);
+		dec_lock_count ();
+		return 1;
+	}
+	return 0;
+}
+
+
+/*
+ * Add an entry at the end.
+ *
+ * defines p->next, p->prev
+ * (unfortunately, owned special are not supported)
+ */
+static void add_one_entry (struct commonio_db *db,
+                           /*@owned@*/struct commonio_entry *p)
+{
+	/*@-mustfreeonly@*/
+	p->next = NULL;
+	p->prev = db->tail;
+	/*@=mustfreeonly@*/
+	if (NULL == db->head) {
+		db->head = p;
+	}
+	if (NULL != db->tail) {
+		db->tail->next = p;
+	}
+	db->tail = p;
+}
+
+
+static bool name_is_nis (const char *name)
+{
+	return (('+' == name[0]) || ('-' == name[0]));
+}
+
+
+/*
+ * New entries are inserted before the first NIS entry.  Order is preserved
+ * when db is written out.
+ */
+#ifndef KEEP_NIS_AT_END
+#define KEEP_NIS_AT_END 1
+#endif
+
+#if KEEP_NIS_AT_END
+static void add_one_entry_nis (struct commonio_db *db,
+                               /*@owned@*/struct commonio_entry *newp);
+
+/*
+ * Insert an entry between the regular entries, and the NIS entries.
+ *
+ * defines newp->next, newp->prev
+ * (unfortunately, owned special are not supported)
+ */
+static void add_one_entry_nis (struct commonio_db *db,
+                               /*@owned@*/struct commonio_entry *newp)
+{
+	struct commonio_entry *p;
+
+	for (p = db->head; NULL != p; p = p->next) {
+		if (name_is_nis (p->eptr ? db->ops->getname (p->eptr)
+		                         : p->line)) {
+			/*@-mustfreeonly@*/
+			newp->next = p;
+			newp->prev = p->prev;
+			/*@=mustfreeonly@*/
+			if (NULL != p->prev) {
+				p->prev->next = newp;
+			} else {
+				db->head = newp;
+			}
+			p->prev = newp;
+			return;
+		}
+	}
+	add_one_entry (db, newp);
+}
+#endif				/* KEEP_NIS_AT_END */
+
+/* Initial buffer size, as well as increment if not sufficient
+   (for reading very long lines in group files).  */
+#define BUFLEN 4096
+
+int commonio_open (struct commonio_db *db, int mode)
+{
+	char *buf;
+	char *cp;
+	char *line;
+	struct commonio_entry *p;
+	void *eptr = NULL;
+	int flags = mode;
+	size_t buflen;
+	int fd;
+	int saved_errno;
+
+	mode &= ~O_CREAT;
+
+	if (   db->isopen
+	    || (   (O_RDONLY != mode)
+	        && (O_RDWR != mode))) {
+		errno = EINVAL;
+		return 0;
+	}
+	db->readonly = (mode == O_RDONLY);
+	if (!db->readonly && !db->locked) {
+		errno = EACCES;
+		return 0;
+	}
+
+	db->head = NULL;
+	db->tail = NULL;
+	db->cursor = NULL;
+	db->changed = false;
+
+	fd = open (db->filename,
+	             (db->readonly ? O_RDONLY : O_RDWR)
+	           | O_NOCTTY | O_NONBLOCK | O_NOFOLLOW);
+	saved_errno = errno;
+	db->fp = NULL;
+	if (fd >= 0) {
+#ifdef WITH_TCB
+		if (tcb_is_suspect (fd) != 0) {
+			(void) close (fd);
+			errno = EINVAL;
+			return 0;
+		}
+#endif				/* WITH_TCB */
+		db->fp = fdopen (fd, db->readonly ? "r" : "r+");
+		saved_errno = errno;
+		if (NULL == db->fp) {
+			(void) close (fd);
+		}
+	}
+	errno = saved_errno;
+
+	/*
+	 * If O_CREAT was specified and the file didn't exist, it will be
+	 * created by commonio_close().  We have no entries to read yet.  --marekm
+	 */
+	if (NULL == db->fp) {
+		if (((flags & O_CREAT) != 0) && (ENOENT == errno)) {
+			db->isopen = true;
+			return 1;
+		}
+		return 0;
+	}
+
+	/* Do not inherit fd in spawned processes (e.g. nscd) */
+	fcntl (fileno (db->fp), F_SETFD, FD_CLOEXEC);
+
+	buflen = BUFLEN;
+	buf = (char *) malloc (buflen);
+	if (NULL == buf) {
+		goto cleanup_ENOMEM;
+	}
+
+	while (db->ops->fgets (buf, (int) buflen, db->fp) == buf) {
+		while (   ((cp = strrchr (buf, '\n')) == NULL)
+		       && (feof (db->fp) == 0)) {
+			size_t len;
+
+			buflen += BUFLEN;
+			cp = (char *) realloc (buf, buflen);
+			if (NULL == cp) {
+				goto cleanup_buf;
+			}
+			buf = cp;
+			len = strlen (buf);
+			if (db->ops->fgets (buf + len,
+			                    (int) (buflen - len),
+			                    db->fp) == NULL) {
+				goto cleanup_buf;
+			}
+		}
+		cp = strrchr (buf, '\n');
+		if (NULL != cp) {
+			*cp = '\0';
+		}
+
+		line = strdup (buf);
+		if (NULL == line) {
+			goto cleanup_buf;
+		}
+
+		if (name_is_nis (line)) {
+			eptr = NULL;
+		} else {
+			eptr = db->ops->parse (line);
+			if (NULL != eptr) {
+				eptr = db->ops->dup (eptr);
+				if (NULL == eptr) {
+					goto cleanup_line;
+				}
+			}
+		}
+
+		p = (struct commonio_entry *) malloc (sizeof *p);
+		if (NULL == p) {
+			goto cleanup_entry;
+		}
+
+		p->eptr = eptr;
+		p->line = line;
+		p->changed = false;
+
+		add_one_entry (db, p);
+	}
+
+	free (buf);
+
+	if (ferror (db->fp) != 0) {
+		goto cleanup_errno;
+	}
+
+	if ((NULL != db->ops->open_hook) && (db->ops->open_hook () == 0)) {
+		goto cleanup_errno;
+	}
+
+	db->isopen = true;
+	return 1;
+
+      cleanup_entry:
+	if (NULL != eptr) {
+		db->ops->free (eptr);
+	}
+      cleanup_line:
+	free (line);
+      cleanup_buf:
+	free (buf);
+      cleanup_ENOMEM:
+	errno = ENOMEM;
+      cleanup_errno:
+	saved_errno = errno;
+	free_linked_list (db);
+	fclose (db->fp);
+	db->fp = NULL;
+	errno = saved_errno;
+	return 0;
+}
+
+/*
+ * Sort given db according to cmp function (usually compares uids)
+ */
+int
+commonio_sort (struct commonio_db *db, int (*cmp) (const void *, const void *))
+{
+	struct commonio_entry **entries, *ptr;
+	size_t n = 0, i;
+#if KEEP_NIS_AT_END
+	struct commonio_entry *nis = NULL;
+#endif
+
+	for (ptr = db->head;
+	        (NULL != ptr)
+#if KEEP_NIS_AT_END
+	     && ((NULL == ptr->line)
+	         || (('+' != ptr->line[0])
+	             && ('-' != ptr->line[0])))
+#endif
+	     ;
+	     ptr = ptr->next) {
+		n++;
+	}
+#if KEEP_NIS_AT_END
+	if (NULL != ptr) {
+		nis = ptr;
+	}
+#endif
+
+	if (n <= 1) {
+		return 0;
+	}
+
+	entries = malloc (n * sizeof (struct commonio_entry *));
+	if (entries == NULL) {
+		return -1;
+	}
+
+	n = 0;
+	for (ptr = db->head;
+#if KEEP_NIS_AT_END
+	     nis != ptr;
+#else
+	     NULL != ptr;
+#endif
+/*@ -nullderef @*/
+	     ptr = ptr->next
+/*@ +nullderef @*/
+	    ) {
+		entries[n] = ptr;
+		n++;
+	}
+	qsort (entries, n, sizeof (struct commonio_entry *), cmp);
+
+	/* Take care of the head and tail separately */
+	db->head = entries[0];
+	n--;
+#if KEEP_NIS_AT_END
+	if (NULL == nis)
+#endif
+	{
+		db->tail = entries[n];
+	}
+	db->head->prev = NULL;
+	db->head->next = entries[1];
+	entries[n]->prev = entries[n - 1];
+#if KEEP_NIS_AT_END
+	entries[n]->next = nis;
+#else
+	entries[n]->next = NULL;
+#endif
+
+	/* Now other elements have prev and next entries */
+	for (i = 1; i < n; i++) {
+		entries[i]->prev = entries[i - 1];
+		entries[i]->next = entries[i + 1];
+	}
+
+	free (entries);
+	db->changed = true;
+
+	return 0;
+}
+
+/*
+ * Sort entries in db according to order in another.
+ */
+int commonio_sort_wrt (struct commonio_db *shadow,
+                       const struct commonio_db *passwd)
+{
+	struct commonio_entry *head = NULL, *pw_ptr, *spw_ptr;
+	const char *name;
+
+	if ((NULL == shadow) || (NULL == shadow->head)) {
+		return 0;
+	}
+
+	for (pw_ptr = passwd->head; NULL != pw_ptr; pw_ptr = pw_ptr->next) {
+		if (NULL == pw_ptr->eptr) {
+			continue;
+		}
+		name = passwd->ops->getname (pw_ptr->eptr);
+		for (spw_ptr = shadow->head;
+		     NULL != spw_ptr;
+		     spw_ptr = spw_ptr->next) {
+			if (NULL == spw_ptr->eptr) {
+				continue;
+			}
+			if (strcmp (name, shadow->ops->getname (spw_ptr->eptr))
+			    == 0) {
+				break;
+			}
+		}
+		if (NULL == spw_ptr) {
+			continue;
+		}
+		commonio_del_entry (shadow, spw_ptr);
+		spw_ptr->next = head;
+		head = spw_ptr;
+	}
+
+	for (spw_ptr = head; NULL != spw_ptr; spw_ptr = head) {
+		head = head->next;
+
+		if (NULL != shadow->head) {
+			shadow->head->prev = spw_ptr;
+		}
+		spw_ptr->next = shadow->head;
+		shadow->head = spw_ptr;
+	}
+
+	shadow->head->prev = NULL;
+	shadow->changed = true;
+
+	return 0;
+}
+
+/*
+ * write_all - Write the database to its file.
+ *
+ * It returns 0 if all the entries could be written correctly.
+ */
+static int write_all (const struct commonio_db *db)
+	/*@requires notnull db->fp@*/
+{
+	const struct commonio_entry *p;
+	void *eptr;
+
+	for (p = db->head; NULL != p; p = p->next) {
+		if (p->changed) {
+			eptr = p->eptr;
+			assert (NULL != eptr);
+			if (db->ops->put (eptr, db->fp) != 0) {
+				return -1;
+			}
+		} else if (NULL != p->line) {
+			if (db->ops->fputs (p->line, db->fp) == EOF) {
+				return -1;
+			}
+			if (putc ('\n', db->fp) == EOF) {
+				return -1;
+			}
+		}
+	}
+	return 0;
+}
+
+
+int commonio_close (struct commonio_db *db)
+{
+	char buf[1024];
+	int errors = 0;
+	struct stat sb;
+
+	if (!db->isopen) {
+		errno = EINVAL;
+		return 0;
+	}
+	db->isopen = false;
+
+	if (!db->changed || db->readonly) {
+		if (NULL != db->fp) {
+			(void) fclose (db->fp);
+			db->fp = NULL;
+		}
+		goto success;
+	}
+
+	if ((NULL != db->ops->close_hook) && (db->ops->close_hook () == 0)) {
+		goto fail;
+	}
+
+	memzero (&sb, sizeof sb);
+	if (NULL != db->fp) {
+		if (fstat (fileno (db->fp), &sb) != 0) {
+			(void) fclose (db->fp);
+			db->fp = NULL;
+			goto fail;
+		}
+
+		/*
+		 * Create backup file.
+		 */
+		snprintf (buf, sizeof buf, "%s-", db->filename);
+
+#ifdef WITH_SELINUX
+		if (set_selinux_file_context (db->filename, S_IFREG) != 0) {
+			errors++;
+		}
+#endif
+		if (create_backup (buf, db->fp) != 0) {
+			errors++;
+		}
+
+		if (fclose (db->fp) != 0) {
+			errors++;
+		}
+
+#ifdef WITH_SELINUX
+		if (reset_selinux_file_context () != 0) {
+			errors++;
+		}
+#endif
+		if (errors != 0) {
+			db->fp = NULL;
+			goto fail;
+		}
+	} else {
+		/*
+		 * Default permissions for new [g]shadow files.
+		 */
+		sb.st_mode = db->st_mode;
+		sb.st_uid = db->st_uid;
+		sb.st_gid = db->st_gid;
+	}
+
+	snprintf (buf, sizeof buf, "%s+", db->filename);
+
+#ifdef WITH_SELINUX
+	if (set_selinux_file_context (db->filename, S_IFREG) != 0) {
+		errors++;
+	}
+#endif
+
+	db->fp = fopen_set_perms (buf, "w", &sb);
+	if (NULL == db->fp) {
+		goto fail;
+	}
+
+	if (write_all (db) != 0) {
+		errors++;
+	}
+
+	if (fflush (db->fp) != 0) {
+		errors++;
+	}
+#ifdef HAVE_FSYNC
+	if (fsync (fileno (db->fp)) != 0) {
+		errors++;
+	}
+#else				/* !HAVE_FSYNC */
+	sync ();
+#endif				/* !HAVE_FSYNC */
+	if (fclose (db->fp) != 0) {
+		errors++;
+	}
+
+	db->fp = NULL;
+
+	if (errors != 0) {
+		unlink (buf);
+		goto fail;
+	}
+
+	if (lrename (buf, db->filename) != 0) {
+		goto fail;
+	}
+
+#ifdef WITH_SELINUX
+	if (reset_selinux_file_context () != 0) {
+		goto fail;
+	}
+#endif
+
+	nscd_need_reload = true;
+	goto success;
+      fail:
+	errors++;
+      success:
+
+	free_linked_list (db);
+	return errors == 0;
+}
+
+static /*@dependent@*/ /*@null@*/struct commonio_entry *next_entry_by_name (
+	struct commonio_db *db,
+	/*@null@*/struct commonio_entry *pos,
+	const char *name)
+{
+	struct commonio_entry *p;
+	void *ep;
+
+	if (NULL == pos) {
+		return NULL;
+	}
+
+	for (p = pos; NULL != p; p = p->next) {
+		ep = p->eptr;
+		if (   (NULL != ep)
+		    && (strcmp (db->ops->getname (ep), name) == 0)) {
+			break;
+		}
+	}
+	return p;
+}
+
+static /*@dependent@*/ /*@null@*/struct commonio_entry *find_entry_by_name (
+	struct commonio_db *db,
+	const char *name)
+{
+	return next_entry_by_name (db, db->head, name);
+}
+
+
+int commonio_update (struct commonio_db *db, const void *eptr)
+{
+	struct commonio_entry *p;
+	void *nentry;
+
+	if (!db->isopen || db->readonly) {
+		errno = EINVAL;
+		return 0;
+	}
+	nentry = db->ops->dup (eptr);
+	if (NULL == nentry) {
+		errno = ENOMEM;
+		return 0;
+	}
+	p = find_entry_by_name (db, db->ops->getname (eptr));
+	if (NULL != p) {
+		if (next_entry_by_name (db, p->next, db->ops->getname (eptr)) != NULL) {
+			fprintf (shadow_logfd, _("Multiple entries named '%s' in %s. Please fix this with pwck or grpck.\n"), db->ops->getname (eptr), db->filename);
+			db->ops->free (nentry);
+			return 0;
+		}
+		db->ops->free (p->eptr);
+		p->eptr = nentry;
+		p->changed = true;
+		db->cursor = p;
+
+		db->changed = true;
+		return 1;
+	}
+	/* not found, new entry */
+	p = (struct commonio_entry *) malloc (sizeof *p);
+	if (NULL == p) {
+		db->ops->free (nentry);
+		errno = ENOMEM;
+		return 0;
+	}
+
+	p->eptr = nentry;
+	p->line = NULL;
+	p->changed = true;
+
+#if KEEP_NIS_AT_END
+	add_one_entry_nis (db, p);
+#else				/* !KEEP_NIS_AT_END */
+	add_one_entry (db, p);
+#endif				/* !KEEP_NIS_AT_END */
+
+	db->changed = true;
+	return 1;
+}
+
+#ifdef ENABLE_SUBIDS
+int commonio_append (struct commonio_db *db, const void *eptr)
+{
+	struct commonio_entry *p;
+	void *nentry;
+
+	if (!db->isopen || db->readonly) {
+		errno = EINVAL;
+		return 0;
+	}
+	nentry = db->ops->dup (eptr);
+	if (NULL == nentry) {
+		errno = ENOMEM;
+		return 0;
+	}
+	/* new entry */
+	p = (struct commonio_entry *) malloc (sizeof *p);
+	if (NULL == p) {
+		db->ops->free (nentry);
+		errno = ENOMEM;
+		return 0;
+	}
+
+	p->eptr = nentry;
+	p->line = NULL;
+	p->changed = true;
+	add_one_entry (db, p);
+
+	db->changed = true;
+	return 1;
+}
+#endif				/* ENABLE_SUBIDS */
+
+void commonio_del_entry (struct commonio_db *db, const struct commonio_entry *p)
+{
+	if (p == db->cursor) {
+		db->cursor = p->next;
+	}
+
+	if (NULL != p->prev) {
+		p->prev->next = p->next;
+	} else {
+		db->head = p->next;
+	}
+
+	if (NULL != p->next) {
+		p->next->prev = p->prev;
+	} else {
+		db->tail = p->prev;
+	}
+
+	db->changed = true;
+}
+
+/*
+ * commonio_remove - Remove the entry of the given name from the database.
+ */
+int commonio_remove (struct commonio_db *db, const char *name)
+{
+	struct commonio_entry *p;
+
+	if (!db->isopen || db->readonly) {
+		errno = EINVAL;
+		return 0;
+	}
+	p = find_entry_by_name (db, name);
+	if (NULL == p) {
+		errno = ENOENT;
+		return 0;
+	}
+	if (next_entry_by_name (db, p->next, name) != NULL) {
+		fprintf (shadow_logfd, _("Multiple entries named '%s' in %s. Please fix this with pwck or grpck.\n"), name, db->filename);
+		return 0;
+	}
+
+	commonio_del_entry (db, p);
+
+	free (p->line);
+
+	if (NULL != p->eptr) {
+		db->ops->free (p->eptr);
+	}
+
+	return 1;
+}
+
+/*
+ * commonio_locate - Find the first entry with the specified name in
+ *                   the database.
+ *
+ *	If found, it returns the entry and set the cursor of the database to
+ *	that entry.
+ *
+ *	Otherwise, it returns NULL.
+ */
+/*@observer@*/ /*@null@*/const void *commonio_locate (struct commonio_db *db, const char *name)
+{
+	struct commonio_entry *p;
+
+	if (!db->isopen) {
+		errno = EINVAL;
+		return NULL;
+	}
+	p = find_entry_by_name (db, name);
+	if (NULL == p) {
+		errno = ENOENT;
+		return NULL;
+	}
+	db->cursor = p;
+	return p->eptr;
+}
+
+/*
+ * commonio_rewind - Restore the database cursor to the first entry.
+ *
+ * It returns 0 on error, 1 on success.
+ */
+int commonio_rewind (struct commonio_db *db)
+{
+	if (!db->isopen) {
+		errno = EINVAL;
+		return 0;
+	}
+	db->cursor = NULL;
+	return 1;
+}
+
+/*
+ * commonio_next - Return the next entry of the specified database
+ *
+ * It returns the next entry, or NULL if no other entries could be found.
+ */
+/*@observer@*/ /*@null@*/const void *commonio_next (struct commonio_db *db)
+{
+	void *eptr;
+
+	if (!db->isopen) {
+		errno = EINVAL;
+		return 0;
+	}
+	if (NULL == db->cursor) {
+		db->cursor = db->head;
+	} else {
+		db->cursor = db->cursor->next;
+	}
+
+	while (NULL != db->cursor) {
+		eptr = db->cursor->eptr;
+		if (NULL != eptr) {
+			return eptr;
+		}
+
+		db->cursor = db->cursor->next;
+	}
+	return NULL;
+}
+