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  1. 15 Dec, 2009 3 commits
    • J. Bruce Fields's avatar
      nfsd4: don't continue "under" mounts in V4ROOT case · 3b6cee7b
      J. Bruce Fields authored 
      If /A/mount/point/ has filesystem "B" mounted on top of it, and if "A"
is exported, but not "B", then the nfs server has always returned to the
client a filehandle for the mountpoint, instead of for the root of "B",
allowing the client to see the subtree of "A" that would otherwise be
hidden by B.

Disable this behavior in the case of V4ROOT exports; we implement the
path restrictions of V4ROOT exports by treating *every* directory as if
it were a mountpoint, and allowing traversal *only* if the new directory
is exported.
Signed-off-by: default avatarJ. Bruce Fields <bfields@citi.umich.edu>
      3b6cee7b
    • Steve Dickson's avatar
      nfsd: introduce export flag for v4 pseudoroot · eb4c86c6
      Steve Dickson authored 
      NFSv4 differs from v2 and v3 in that it presents a single unified
filesystem tree, whereas v2 and v3 exported multiple filesystem (whose
roots could be found using a separate mount protocol).

Our original NFSv4 server implementation asked the administrator to
designate a single filesystem as the NFSv4 root, then to mount
filesystems they wished to export underneath.  (Often using bind mounts
of already-existing filesystems.)

This was conceptually simple, and allowed easy implementation, but
created a serious obstacle to upgrading between v2/v3: since the paths
to v4 filesystems were different, administrators would have to adjust
all the paths in client-side mount commands when switching to v4.

Various workarounds are possible.  For example, the administrator could
export "/" and designate it as the v4 root.  However, the security risks
of that approach are obvious, and in any case we shouldn't be requiring
the administrator to take extra steps to fix this problem; instead, the
server should present consistent paths across different versions by
default.

These patches take a modified version of that approach: we provide a new
export option which exports only a subset of a filesystem.  With this
flag, it becomes safe for mountd to export "/" by default, with no need
for additional configuration.

We begin just by defining the new flag.
Signed-off-by: default avatarSteve Dickson <steved@redhat.com>
Signed-off-by: default avatarJ. Bruce Fields <bfields@citi.umich.edu>
      eb4c86c6
    • J. Bruce Fields's avatar
      nfsd: let "insecure" flag vary by pseudoflavor · 12045a6e
      J. Bruce Fields authored 
      This was an oversight; it should be among the export flags that can be
allowed to vary by pseudoflavor.  This allows an administrator to (for
example) allow auth_sys mounts only from low ports, but allow auth_krb5
mounts to use any port.
Signed-off-by: default avatarJ. Bruce Fields <bfields@citi.umich.edu>
      12045a6e
  3. 14 Dec, 2009 14 commits
  5. 25 Nov, 2009 1 commit
    • J. Bruce Fields's avatar
      nfsd: simplify fh_verify access checks · 864f0f61
      J. Bruce Fields authored 
      All nfsd security depends on the security checks in fh_verify, and
especially on nfsd_setuser().

It therefore bothers me that the nfsd_setuser call may be made from
three different places, depending on whether the filehandle has already
been mapped to a dentry, and on whether subtreechecking is in force.

Instead, make an unconditional call in fh_verify(), so it's trivial to
verify that the call always occurs.

That leaves us with a redundant nfsd_setuser() call in the subtreecheck
case--it needs the correct user set earlier in order to check execute
permissions on the path to this filehandle--but I'm willing to accept
that minor inefficiency in the subtreecheck case in return for more
straightforward permission checking.
Signed-off-by: default avatarJ. Bruce Fields <bfields@citi.umich.edu>
      864f0f61
  7. 23 Nov, 2009 2 commits
  9. 19 Nov, 2009 9 commits
  11. 18 Nov, 2009 11 commits
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