Modify pw_copy:

- if pw is NULL and oldpw is not NULL then the oldpw is deleted
- if pw->pw_name != oldpw->pw_name but pw->pw_uid == oldpw->pw_uid
then it renames the user

add new gr_* functions so now gr_util API is similar to pw_util API,
this allow to manipulate groups in a safe way.

Reviewed by:	des
Approved by:	des
MFC after:	1 month

3 files changed, 332 insertions, 13 deletions

diff --git a/lib/libutil/gr_util.c b/lib/libutil/gr_util.c
index 633f435..0173595 100644
--- a/lib/libutil/gr_util.c
+++ b/lib/libutil/gr_util.c
@@ -28,23 +28,319 @@
 __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
+#include <sys/errno.h>
+#include <sys/stat.h>
 
+#include <ctype.h>
+#include <err.h>
+#include <fcntl.h>
 #include <grp.h>
 #include <inttypes.h>
 #include <libutil.h>
+#include <paths.h>
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 
 struct group_storage {
 	struct group	 gr;
 	char		*members[];
 };
 
+static int lockfd = -1;
+static char group_dir[PATH_MAX];
+static char group_file[PATH_MAX];
+static char tempname[PATH_MAX];
+static int initialized;
+
 static const char group_line_format[] = "%s:%s:%ju:";
 
 /*
+ * Initialize statics
+ */
+int
+gr_init(const char *dir, const char *group)
+{
+	if (dir == NULL) {
+		strcpy(group_dir, _PATH_ETC);
+	} else {
+		if (strlen(dir) >= sizeof(group_dir)) {
+			errno = ENAMETOOLONG;
+			return (-1);
+		}
+		strcpy(group_dir, dir);
+	}
+
+	if (group == NULL) {
+		if (dir == NULL) {
+			strcpy(group_file, _PATH_GROUP);
+		} else if (snprintf(group_file, sizeof(group_file), "%s/group",
+			group_dir) > (int)sizeof(group_file)) {
+			errno = ENAMETOOLONG;
+			return (-1);
+		}
+	} else {
+		if (strlen(group) >= sizeof(group_file)) {
+			errno = ENAMETOOLONG;
+			return (-1);
+		}
+		strcpy(group_file, group);
+	}
+	initialized = 1;
+	return (0);
+}
+
+/*
+ * Lock the group file
+ */
+int
+gr_lock(void)
+{
+	if (*group_file == '\0')
+		return (-1);
+
+	for (;;) {
+		struct stat st;
+
+		lockfd = open(group_file, O_RDONLY, 0);
+		if (lockfd < 0 || fcntl(lockfd, F_SETFD, 1) == -1)
+			err(1, "%s", group_file);
+		if (flock(lockfd, LOCK_EX|LOCK_NB) == -1) {
+			if (errno == EWOULDBLOCK) {
+				errx(1, "the group file is busy");
+			} else {
+				err(1, "could not lock the group file: ");
+			}
+		}
+		if (fstat(lockfd, &st) == -1)
+			err(1, "fstat() failed: ");
+		if (st.st_nlink != 0)
+			break;
+		close(lockfd);
+		lockfd = -1;
+	}
+	return (lockfd);
+}
+
+/*
+ * Create and open a presmuably safe temp file for editing group data
+ */
+int
+gr_tmp(int mfd)
+{
+	char buf[8192];
+	ssize_t nr;
+	const char *p;
+	int tfd;
+
+	if (*group_file == '\0')
+		return (-1);
+	if ((p = strrchr(group_file, '/')))
+		++p;
+	else
+		p = group_file;
+	if (snprintf(tempname, sizeof(tempname), "%.*sgroup.XXXXXX",
+		(int)(p - group_file), group_file) >= (int)sizeof(tempname)) {
+		errno = ENAMETOOLONG;
+		return (-1);
+	}
+	if ((tfd = mkstemp(tempname)) == -1)
+		return (-1);
+	if (mfd != -1) {
+		while ((nr = read(mfd, buf, sizeof(buf))) > 0)
+			if (write(tfd, buf, (size_t)nr) != nr)
+				break;
+		if (nr != 0) {
+			unlink(tempname);
+			*tempname = '\0';
+			close(tfd);
+			return (-1);
+		}
+	}
+	return (tfd);
+}
+
+/*
+ * Copy the group file from one descriptor to another, replacing, deleting
+ * or adding a single record on the way.
+ */
+int
+gr_copy(int ffd, int tfd, const struct group *gr, struct group *old_gr)
+{
+	char buf[8192], *end, *line, *p, *q, *r, t;
+	struct group *fgr;
+	const struct group *sgr;
+	size_t len;
+	int eof, readlen;
+
+	sgr = gr;
+	if (gr == NULL) {
+		line = NULL;
+		if (old_gr == NULL)
+			return (-1);
+		sgr = old_gr;
+	} else if ((line = gr_make(gr)) == NULL)
+		return (-1);
+
+	eof = 0;
+	len = 0;
+	p = q = end = buf;
+	for (;;) {
+		/* find the end of the current line */
+		for (p = q; q < end && *q != '\0'; ++q)
+			if (*q == '\n')
+				break;
+
+		/* if we don't have a complete line, fill up the buffer */
+		if (q >= end) {
+			if (eof)
+				break;
+			if ((size_t)(q - p) >= sizeof(buf)) {
+				warnx("group line too long");
+				errno = EINVAL; /* hack */
+				goto err;
+			}
+			if (p < end) {
+				q = memmove(buf, p, end -p);
+				end -= p - buf;
+			} else {
+				p = q = end = buf;
+			}
+			readlen = read(ffd, end, sizeof(buf) - (end -buf));
+			if (readlen == -1)
+				goto err;
+			else
+				len = (size_t)readlen;
+			if (len == 0 && p == buf)
+				break;
+			end += len;
+			len = end - buf;
+			if (len < (ssize_t)sizeof(buf)) {
+				eof = 1;
+				if (len > 0 && buf[len -1] != '\n')
+					++len, *end++ = '\n';
+			}
+			continue;
+		}
+
+		/* is it a blank line or a comment? */
+		for (r = p; r < q && isspace(*r); ++r)
+			/* nothing */;
+		if (r == q || *r == '#') {
+			/* yep */
+			if (write(tfd, p, q -p + 1) != q - p + 1)
+				goto err;
+			++q;
+			continue;
+		}
+
+		/* is it the one we're looking for? */
+
+		t = *q;
+		*q = '\0';
+
+		fgr = gr_scan(r);
+
+		/* fgr is either a struct group for the current line,
+		 * or NULL if the line is malformed.
+		 */
+
+		*q = t;
+		if (fgr == NULL || fgr->gr_gid != sgr->gr_gid) {
+			/* nope */
+			if (fgr != NULL)
+				free(fgr);
+			if (write(tfd, p, q - p + 1) != q - p + 1)
+				goto err;
+			++q;
+			continue;
+		}
+		if (old_gr && !gr_equal(fgr, old_gr)) {
+			warnx("entry inconsistent");
+			free(fgr);
+			errno = EINVAL; /* hack */
+			goto err;
+		}
+		free(fgr);
+
+		/* it is, replace or remove it */
+		if (line != NULL) {
+			len = strlen(line);
+			if (write(tfd, line, len) != (int) len)
+				goto err;
+		} else {
+			/* when removed, avoid the \n */
+			q++;
+		}
+		/* we're done, just copy the rest over */
+		for (;;) {
+			if (write(tfd, q, end - q) != end - q)
+				goto err;
+			q = buf;
+			readlen = read(ffd, buf, sizeof(buf));
+			if (readlen == 0)
+				break;
+			else
+				len = (size_t)readlen;
+			if (readlen == -1)
+				goto err;
+			end = buf + len;
+		}
+		goto done;
+	}
+
+	/* if we got here, we didn't find the old entry */
+	if (line == NULL) {
+		errno = ENOENT;
+		goto err;
+	}
+	len = strlen(line);
+	if ((size_t)write(tfd, line, len) != len ||
+	   write(tfd, "\n", 1) != 1)
+		goto err;
+ done:
+	if (line != NULL)
+		free(line);
+	return (0);
+ err:
+	if (line != NULL)
+		free(line);
+	return (-1);
+}
+
+/*
+ * Regenerate the group file
+ */
+int
+gr_mkdb(void)
+{
+	return (rename(tempname, group_file));
+}
+
+/*
+ * Clean up. Preserver errno for the caller's convenience.
+ */
+void
+gr_fini(void)
+{
+	int serrno;
+
+	if (!initialized)
+		return;
+	initialized = 0;
+	serrno = errno;
+	if (*tempname != '\0') {
+		unlink(tempname);
+		*tempname = '\0';
+	}
+	if (lockfd != -1)
+		close(lockfd);
+	errno = serrno;
+}
+
+/*
  * Compares two struct group's.
  */
 int
diff --git a/lib/libutil/libutil.h b/lib/libutil/libutil.h
index fc6d3bb..dea14cf 100644
--- a/lib/libutil/libutil.h
+++ b/lib/libutil/libutil.h
@@ -152,9 +152,15 @@ int	pw_tmp(int _mfd);
 #endif
 
 #ifdef _GRP_H_
+int 	gr_copy(int __ffd, int _tfd, const struct group *_gr, struct group *_old_gr);
+struct group *gr_dup(const struct group *gr);
 int	gr_equal(const struct group *gr1, const struct group *gr2);
+void	gr_fini(void);
+int	gr_init(const char *_dir, const char *_master);
+int	gr_lock(void);
 char	*gr_make(const struct group *gr);
-struct group *gr_dup(const struct group *gr);
+int	gr_mkdb(void);
+int	gr_tmp(int _mdf);
 struct group *gr_scan(const char *line);
 #endif
 
diff --git a/lib/libutil/pw_util.c b/lib/libutil/pw_util.c
index 5eae280..1068eff 100644
--- a/lib/libutil/pw_util.c
+++ b/lib/libutil/pw_util.c
@@ -410,18 +410,25 @@ pw_make(const struct passwd *pw)
 }
 
 /*
- * Copy password file from one descriptor to another, replacing or adding
- * a single record on the way.
+ * Copy password file from one descriptor to another, replacing, deleting
+ * or adding a single record on the way.
  */
 int
 pw_copy(int ffd, int tfd, const struct passwd *pw, struct passwd *old_pw)
 {
 	char buf[8192], *end, *line, *p, *q, *r, t;
 	struct passwd *fpw;
+	const struct passwd *spw;
 	size_t len;
 	int eof, readlen;
 
-	if ((line = pw_make(pw)) == NULL)
+	spw = pw;
+	if (pw == NULL) {
+		line = NULL;
+		if (old_pw == NULL)
+			return (-1);
+		spw = old_pw;
+	} else if ((line = pw_make(pw)) == NULL)
 		return (-1);
 
 	eof = 0;
@@ -489,7 +496,7 @@ pw_copy(int ffd, int tfd, const struct passwd *pw, struct passwd *old_pw)
 		 */
 
 		*q = t;
-		if (fpw == NULL || strcmp(fpw->pw_name, pw->pw_name) != 0) {
+		if (fpw == NULL || fpw->pw_uid != spw->pw_uid) {
 			/* nope */
 			if (fpw != NULL)
 				free(fpw);
@@ -506,11 +513,15 @@ pw_copy(int ffd, int tfd, const struct passwd *pw, struct passwd *old_pw)
 		}
 		free(fpw);
 
-		/* it is, replace it */
-		len = strlen(line);
-		if (write(tfd, line, len) != (int)len)
-			goto err;
-
+		/* it is, replace or remove it */
+		if (line != NULL) {
+			len = strlen(line);
+			if (write(tfd, line, len) != (int)len)
+				goto err;
+		} else {
+			/* when removed, avoid the \n */
+			q++;
+		}
 		/* we're done, just copy the rest over */
 		for (;;) {
 			if (write(tfd, q, end - q) != end - q)
@@ -528,16 +539,22 @@ pw_copy(int ffd, int tfd, const struct passwd *pw, struct passwd *old_pw)
 		goto done;
 	}
 
-	/* if we got here, we have a new entry */
+	/* if we got here, we didn't find the old entry */
+	if (line == NULL) {
+		errno = ENOENT;
+		goto err;
+	}
 	len = strlen(line);
 	if ((size_t)write(tfd, line, len) != len ||
 	    write(tfd, "\n", 1) != 1)
 		goto err;
  done:
-	free(line);
+	if (line != NULL)
+		free(line);
 	return (0);
  err:
-	free(line);
+	if (line != NULL)
+		free(line);
 	return (-1);
 }