Date: Fri, 10 Nov 1995 02:22:21 -0800 From: Faried Nawaz <fn@pain.csrv.uidaho.edu> To: hackers@freebsd.org Subject: vnconfig question. Message-ID: <199511101022.CAA10981@pain.csrv.uidaho.edu>
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hi,
1)
yesterday, the news machine ran out of swap (80mb doesn't cut it...), and
i decided to create a swapfile. i did (as root)
dd if=/dev/zero of=/x/b/swapfile bs=1k count=16384
vnconfig -v -e /dev/vn0c /x/b/swapfile swap
later, today, i was looking around on the box, and saw
-rw-rw-r-- 1 root wheel 16777216 Nov 8 23:06 swapfile
ie, read perms for everyone on the swapfile.
this is (obviously) bad for security. i guess if i'd thought a
bit more about what i was doing, and had remembered to umask 077
or chmod og-r swapfile, this would not be a problem. i'm not
sure everyone will always do that, though.
does it make sense to change vnconfig to automatically adjust the
permissions of a vnode file upon configuring, or to warn the user?
if so, should it do that upon configuring for any file, or for just
swapfiles (i'm guessing swapfiles only)?
i hacked together a patch which would change the permissions on the
swapfile if vnconfig -e ... ... swap is used. it's a bad patch because
(i think!) people can do
vnconfig -c /dev/vn0b /blah/swapfile
swapon /dev/vn0b
and it does nothing to the swapfile in that case.
here's the patch (against -current):
*** vnconfig.c-ORIG Thu Nov 9 22:27:45 1995
--- vnconfig.c Fri Nov 10 02:01:22 1995
***************
*** 301,311 ****
*/
if (flags & VN_ENABLE) {
if (flags & VN_SWAP) {
! rv = swapon(dev);
if (rv)
! perror("swapon");
! else if (verbose)
! printf("%s: swapping enabled\n", dev);
}
if (flags & (VN_MOUNTRO|VN_MOUNTRW)) {
struct ufs_args args;
--- 301,326 ----
*/
if (flags & VN_ENABLE) {
if (flags & VN_SWAP) {
! struct stat st;
!
! rv = stat(file, &st);
if (rv)
! perror("stat");
! else {
! if (st.st_mode & S_IRGRP ||
! st.st_mode & S_IROTH) {
! rv = chmod(vndisks[0].file, S_IRUSR);
! if (rv)
! perror("chmod");
! else {
! rv = swapon(dev);
! if (rv)
! perror("swapon");
! else if (verbose)
! printf("%s: swapping enabled\n", dev);
! }
! }
! }
}
if (flags & (VN_MOUNTRO|VN_MOUNTRW)) {
struct ufs_args args;
faried.
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