Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC: r252138
Add a new "-o" option to the gssd which forces gss_init_sec_context()
to use DES and the associated old style GSS initialization token.
This appears to be required for some non-FreeBSD servers to
get a kerberized NFS mount to work. Also, ignore some signals when daemonized,
which might fix the gssd from "disappearing" without leaving a core dump.
Given the tight timeframe for the FreeBSD9.2 release, I have
committed this while waiting for code review. I will commit
changes recommended by the review in a separate commit.

MFC: r251444, r251476
Add a "-v" (verbose) option to the gssd daemon, to help
with diagnosis of kerberized NFS mount problems. When set,
messages are sent to syslog() (or fprintf(stderr,...) if
"-d" is also specified) to indicate activity/results of
kgssapi upcalls.

MFC: r250176
Fix the getpwuid_r() call in the gssd daemon so that it handles
the ERANGE error return case. Without this fix, authentication
of users for certain system setups could fail unexpectedly.

MFC: r244604, r244638, r245014
It was reported via email that some sshds create kerberos
credential cache files with names other than /tmp/krb5cc_<uid>.
The gssd daemon does not know how to find these credential caches.
This patch implements a new option "-s" that does a search for
credential cache files, using roughly the same algorithm as the
gssd daemon for Linux uses. The gssd behaviour is only changed
if the new "-s" option is specified.

MFC: r244331
Fix the gssd daemon so that it uses syslog() to report
an error instead of calling err() when it is daemonized,
so that the error gets logged.

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Implement support for RPCSEC_GSS authentication to both the NFS client
and server. This replaces the RPC implementation of the NFS client and
server with the newer RPC implementation originally developed
(actually ported from the userland sunrpc code) to support the NFS
Lock Manager. I have tested this code extensively and I believe it is
stable and that performance is at least equal to the legacy RPC
implementation.

The NFS code currently contains support for both the new RPC
implementation and the older legacy implementation inherited from the
original NFS codebase. The default is to use the new implementation -
add the NFS_LEGACYRPC option to fall back to the old code. When I
merge this support back to RELENG_7, I will probably change this so
that users have to 'opt in' to get the new code.

To use RPCSEC_GSS on either client or server, you must build a kernel
which includes the KGSSAPI option and the crypto device. On the
userland side, you must build at least a new libc, mountd, mount_nfs
and gssd. You must install new versions of /etc/rc.d/gssd and
/etc/rc.d/nfsd and add 'gssd_enable=YES' to /etc/rc.conf.

As long as gssd is running, you should be able to mount an NFS
filesystem from a server that requires RPCSEC_GSS authentication. The
mount itself can happen without any kerberos credentials but all
access to the filesystem will be denied unless the accessing user has
a valid ticket file in the standard place (/tmp/krb5cc_<uid>). There
is currently no support for situations where the ticket file is in a
different place, such as when the user logged in via SSH and has
delegated credentials from that login. This restriction is also
present in Solaris and Linux. In theory, we could improve this in
future, possibly using Brooks Davis' implementation of variant
symlinks.

Supporting RPCSEC_GSS on a server is nearly as simple. You must create
service creds for the server in the form 'nfs/<fqdn>@<REALM>' and
install them in /etc/krb5.keytab. The standard heimdal utility ktutil
makes this fairly easy. After the service creds have been created, you
can add a '-sec=krb5' option to /etc/exports and restart both mountd
and nfsd.

The only other difference an administrator should notice is that nfsd
doesn't fork to create service threads any more. In normal operation,
there will be two nfsd processes, one in userland waiting for TCP
connections and one in the kernel handling requests. The latter
process will create as many kthreads as required - these should be
visible via 'top -H'. The code has some support for varying the number
of service threads according to load but initially at least, nfsd uses
a fixed number of threads according to the value supplied to its '-n'
option.

Sponsored by: Isilon Systems
MFC after: 1 month