Special kernel keys, such as those used to hold DNS results for AFS, CIFS and
NFS and those used to hold idmapper results for NFS, used to be
'invalidateable' with key_revoke().  However, since the default permissions for
keys were reduced:

	Commit: 96b5c8fe
	KEYS: Reduce initial permissions on keys

it has become impossible to do this.

Add a key flag (KEY_FLAG_ROOT_CAN_INVAL) that will permit a key to be
invalidated by root.  This should not be used for system keyrings as the
garbage collector will try and remove any invalidate key.  For system keyrings,
KEY_FLAG_ROOT_CAN_CLEAR can be used instead.

After this, from userspace, keyctl_invalidate() and "keyctl invalidate" can be
used by any possessor of CAP_SYS_ADMIN (typically root) to invalidate DNS and
idmapper keys.  Invalidated keys are immediately garbage collected and will be
immediately rerequested if needed again.
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Tested-by: NSteve Dickson <steved@redhat.com>

dns_query() credulously assumes that keys are null-terminated and
returns a copy of a memory block that is off by one.
Signed-off-by: NManuel Schölling <manuel.schoelling@gmx.de>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

According to RFC1035 "[...] the total length of a domain name (i.e.,
label octets and label length octets) is restricted to 255 octets or
less."
Signed-off-by: NManuel Schölling <manuel.schoelling@gmx.de>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Several files refer to an old address for the Free Software Foundation
in the file header comment.  Resolve by replacing the address with
the URL <http://www.gnu.org/licenses/> so that we do not have to keep
updating the header comments anytime the address changes.

CC: John Fastabend <john.r.fastabend@intel.com>
CC: Alex Duyck <alexander.h.duyck@intel.com>
CC: Marcel Holtmann <marcel@holtmann.org>
CC: Gustavo Padovan <gustavo@padovan.org>
CC: Johan Hedberg <johan.hedberg@gmail.com>
CC: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

If the DNS server returns an error, allow that to be cached in the DNS resolver
key in lieu of a value.  Userspace passes the desired error number as an option
in the payload:

	"#dnserror=<number>"

Userspace must map h_errno from the name resolution routines to an appropriate
Linux error before passing it up.  Something like the following mapping is
recommended:

	[HOST_NOT_FOUND]	= ENODATA,
	[TRY_AGAIN]		= EAGAIN,
	[NO_RECOVERY]		= ECONNREFUSED,
	[NO_DATA]		= ENODATA,

in lieu of Linux errors specifically for representing name service errors.  The
filesystem must map these errors appropropriately before passing them to
userspace.  AFS is made to map ENODATA and EAGAIN to EDESTADDRREQ for the
return to userspace; ECONNREFUSED is allowed to stand as is.

The error can be seen in /proc/keys as a negative number after the description
of the key.  Compare, for example, the following key entries:

2f97238c I--Q--     1  53s 3f010000     0     0 dns_resol afsdb:grand.centrall.org: -61
338bfbbe I--Q--     1  59m 3f010000     0     0 dns_resol afsdb:grand.central.org: 37

If the error option is supplied in the payload, the main part of the payload is
discarded.  The key should have an expiry time set by userspace.
Signed-off-by: NWang Lei <wang840925@gmail.com>
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Acked-by: NJeff Layton <jlayton@redhat.com>
Signed-off-by: NSteve French <sfrench@us.ibm.com>

Fixes for the DNS query module, including:

 (1) Use 'negative' instead of '-ve' in the documentation.

 (2) Mark the kdoc comment with '/**' on dns_query().
Reported-by: NRandy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Signed-off-by: NSteve French <sfrench@us.ibm.com>

Fixes build errors:

net/dns_resolver/dns_key.c: In function 'init_dns_resolver':
net/dns_resolver/dns_key.c:170: error: implicit declaration of function 'IS_ERR'
net/dns_resolver/dns_key.c:171: error: implicit declaration of function 'PTR_ERR'
net/dns_resolver/dns_query.c: In function 'dns_query':
net/dns_resolver/dns_query.c:126: error: implicit declaration of function 'IS_ERR'
net/dns_resolver/dns_query.c:127: error: implicit declaration of function 'PTR_ERR'
Signed-off-by: NStephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Signed-off-by: NSteve French <sfrench@us.ibm.com>

Separate out the DNS resolver key type from the CIFS filesystem into its own
module so that it can be made available for general use, including the AFS
filesystem module.

This facility makes it possible for the kernel to upcall to userspace to have
it issue DNS requests, package up the replies and present them to the kernel
in a useful form.  The kernel is then able to cache the DNS replies as keys
can be retained in keyrings.

Resolver keys are of type "dns_resolver" and have a case-insensitive
description that is of the form "[<type>:]<domain_name>".  The optional <type>
indicates the particular DNS lookup and packaging that's required.  The
<domain_name> is the query to be made.

If <type> isn't given, a basic hostname to IP address lookup is made, and the
result is stored in the key in the form of a printable string consisting of a
comma-separated list of IPv4 and IPv6 addresses.

This key type is supported by userspace helpers driven from /sbin/request-key
and configured through /etc/request-key.conf.  The cifs.upcall utility is
invoked for UNC path server name to IP address resolution.

The CIFS functionality is encapsulated by the dns_resolve_unc_to_ip() function,
which is used to resolve a UNC path to an IP address for CIFS filesystem.  This
part remains in the CIFS module for now.

See the added Documentation/networking/dns_resolver.txt for more information.
Signed-off-by: NWang Lei <wang840925@gmail.com>
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Acked-by: NJeff Layton <jlayton@redhat.com>
Signed-off-by: NSteve French <sfrench@us.ibm.com>