chown(1) / chgrp(1) fail on symbolic links

[Larry Philps]

Subject: chown(1) / chgrp(1) do not work on symbolic links
Index:	/usr/src/bin/chgrp.c /usr/src/etc/chown.c 4.2BSD

Description:
	The chown system call does not follow symbolic links in
	namei so that it is possible to change the owner and group
	of the link itself and not just what it points to.  Also
	chown(2) changes both the owner and group.  Thus chown (1)
	stat's the destination file in order to find its current group.
	This value is then used in the call to chown (2).  A similar
	situtation exists for chgrp in which it needs to know the current
	owner of the file before calling chown (2).  However, both
	chgrp and chown use the stat (2) system call, so that if you
	try to chown/chgrp a symbolic link, the group/owner will end up
	being set to the group/owner of the file the link points to.
Repeat-By:
	Script started on Tue Jul  2 13:35:55 1985
	# echo > junk
	# chown 9998 junk
	# chgrp 9999 junk
	# ln -s junk symlink
	# ls -lg symlink junk
	-rw-r--r--  1 9998     9999            0 Jul  2 13:36 junk
	lrwxr-xr-x  1 0        0               4 Jul  2 13:36 symlink@ -> junk
	# chown root symlink
	# ls -lg junk symlink
	-rw-r--r--  1 9998     9999            0 Jul  2 13:36 junk
	lrwxr-xr-x  1 0        9999            4 Jul  2 13:36 symlink@ -> junk
			       ----
	# rm symlink
	# ln -s junk symlink
	# ls -lg symlink junk
	-rw-r--r--  1 9998     9999            0 Jul  2 13:36 junk
	lrwxr-xr-x  1 0        0               4 Jul  2 13:36 symlink@ -> junk
	# chgrp daemon symlink
	# lg -lg junk symlink
	-rw-r--r--  1 9998     9999            0 Jul  2 13:36 junk
	lrwxr-xr-x  1 9998     1               4 Jul  2 13:37 symlink@ -> junk
		      ----
Fix:
	Change the call to stat (2) in both chgrp.c and chown.c to be
	a call to lstat (2).

	*** /tmp/,RCSt1001285	Tue Jul  2 13:43:07 1985
	--- chown.c	Tue Jul  2 11:29:46 1985
	***************
	*** 41,45
	  cho:
		for(c=2; c<argc; c++) {
	! 		stat(argv[c], &stbuf);
			if(chown(argv[c], uid, stbuf.st_gid) < 0 && !fflag) {
				perror(argv[c]);

	--- 45,49 -----
	  cho:
		for(c=2; c<argc; c++) {
	! 		lstat(argv[c], &stbuf);
			if(chown(argv[c], uid, stbuf.st_gid) < 0 && !fflag) {
				perror(argv[c]);

	*** /tmp/,RCSt1001291	Tue Jul  2 13:43:23 1985
	--- chgrp.c	Tue Jul  2 11:32:33 1985
	***************
	*** 71,75
	  ok:
		for (c = 1; c < argc; c++) {
	! 		if (stat(argv[c], &stbuf)) {
				perror(argv[c]);
				continue;

	--- 72,76 -----
	  ok:
		for (c = 1; c < argc; c++) {
	! 		if (lstat(argv[c], &stbuf)) {
				perror(argv[c]);
				continue;

-- 
						Larry Philps
						Engineering Computing Facility
						University of Toronto
		{linus,ihnp4,uw-beaver,floyd,decvax,utzoo}!utcsri!utecfa!larry