.\" rpc.gssd(8)
.\"
.\" Copyright (C) 2003 J. Bruce Fields <bfields@umich.edu>
-.TH rpc.gssd 8 "14 Mar 2007"
+.\"
+.TH rpc.gssd 8 "20 Feb 2013"
.SH NAME
-rpc.gssd \- rpcsec_gss daemon
+rpc.gssd \- RPCSEC_GSS daemon
.SH SYNOPSIS
-.B "rpc.gssd [-f] [-n] [-k keytab] [-p pipefsdir] [-v] [-r] [-d ccachedir]"
-.SH DESCRIPTION
-The rpcsec_gss protocol gives a means of using the gss-api generic security
-api to provide security for protocols using rpc (in particular, nfs). Before
-exchanging any rpc requests using rpcsec_gss, the rpc client must first
-establish a security context. The linux kernel's implementation of rpcsec_gss
-depends on the userspace daemon
.B rpc.gssd
-to establish security contexts. The
+.RB [ \-fMnlvr ]
+.RB [ \-k
+.IR keytab ]
+.RB [ \-p
+.IR pipefsdir ]
+.RB [ \-d
+.IR ccachedir ]
+.RB [ \-t
+.IR timeout ]
+.RB [ \-R
+.IR realm ]
+.SH INTRODUCTION
+The RPCSEC_GSS protocol, defined in RFC 5403, is used to provide
+strong security for RPC-based protocols such as NFS.
+.P
+Before exchanging RPC requests using RPCSEC_GSS, an RPC client must
+establish a GSS
+.IR "security context" .
+A security context is shared state on each
+end of a network transport that enables GSS-API security services.
+.P
+Security contexts are established using
+.IR "security credentials" .
+A credential grants temporary access to a secure network service,
+much as a railway ticket grants temporary access to use a rail service.
+.P
+A user typically obtains a credential by providing a password to the
+.BR kinit (1)
+command, or via a PAM library at login time.
+A credential acquired with a
+.I user principal
+is known as a
+.I user credential
+(see
+.BR kerberos (1)
+for more on principals).
+.P
+For certain operations, a credential is required
+which represents no user,
+is otherwise unprivileged,
+and is always available.
+This is referred to as a
+.IR "machine credential" .
+.P
+Machine credentials are typically established using a
+.IR "service principal" ,
+whose encrypted password, called its
+.IR key ,
+is stored in a file, called a
+.IR keytab ,
+to avoid requiring a user prompt.
+A machine credential effectively does not expire because the system
+can renew it as needed without user intervention.
+.P
+Once obtained, credentials are typically stored in local temporary files
+with well-known pathnames.
+.SH DESCRIPTION
+To establish GSS security contexts using these credential files,
+the Linux kernel RPC client depends on a userspace daemon called
+.BR rpc.gssd .
+The
.B rpc.gssd
-daemon uses files in the rpc_pipefs filesystem to communicate with the kernel.
-
+daemon uses the rpc_pipefs filesystem to communicate with the kernel.
.SH OPTIONS
.TP
.B -f
attempting to mount an nfs filesystem requiring Kerberos
authentication.
.TP
-.B -k keytab
+.BI "-k " keytab
Tells
.B rpc.gssd
to use the keys found in
.I keytab
to obtain "machine credentials".
-The default value is "/etc/krb5.keytab".
+The default value is
+.I /etc/krb5.keytab.
.IP
Previous versions of
.B rpc.gssd
If this search order does not use the correct key then provide a
keytab file that contains only correct keys.
.TP
-.B -p path
+.B -l
Tells
.B rpc.gssd
-where to look for the rpc_pipefs filesystem. The default value is
-"/var/lib/nfs/rpc_pipefs".
+to limit session keys to Single DES even if the kernel supports stronger
+encryption types. Service ticket encryption is still governed by what
+the KDC believes the target server supports. This way the client can
+access a server that has strong keys in its keytab for ticket decryption
+but whose kernel only supports Single DES.
+.IP
+The alternative is to put only Single DES keys in the server's keytab
+and limit encryption types for its principal to Single DES on the KDC
+which will cause service tickets for this server to be encrypted using
+only Single DES and (as a side-effect) contain only Single DES session
+keys.
+.IP
+This legacy behaviour is only required for older servers
+(pre nfs-utils-1.2.4). If the server has a recent kernel, Kerberos
+implementation and nfs-utils it will work just fine with stronger
+encryption.
+.IP
+.B Note:
+This option is only available with Kerberos libraries that
+support setable encryption types.
.TP
-.B -d directory
+.BI "-p " path
Tells
.B rpc.gssd
-where to look for Kerberos credential files. The default value is "/tmp".
-This can also be a colon separated list of directories to be searched
-for Kerberos credential files. Note that if machine credentials are being
-stored in files, then the first directory on this list is where the
-machine credentials are stored.
+where to look for the rpc_pipefs filesystem. The default value is
+.IR /var/lib/nfs/rpc_pipefs .
+.TP
+.BI "-d " search-path
+This option specifies a colon separated list of directories that
+.B rpc.gssd
+searches for credential files. The default value is
+.IR /tmp:/run/user/%U .
+The literal sequence "%U" can be specified to substitue the UID
+of the user for whom credentials are being searched.
+.TP
+.B -M
+By default, machine credentials are stored in files in the first
+directory in the credential directory search path (see the
+.B -d
+option). When
+.B -M
+is set,
+.B rpc.gssd
+stores machine credentials in memory instead.
.TP
.B -v
Increases the verbosity of the output (can be specified multiple times).
.TP
.B -r
-If the rpcsec_gss library supports setting debug level,
+If the RPCSEC_GSS library supports setting debug level,
increases the verbosity of the output (can be specified multiple times).
.TP
-.B -R realm
+.BI "-R " realm
Kerberos tickets from this
.I realm
will be preferred when scanning available credentials cache files to be
used to create a context. By default, the default realm, as configured
in the Kerberos configuration file, is preferred.
.TP
-.B -t timeout
-Timeout, in seconds, for kernel gss contexts. This option allows you to force
+.BI "-t " timeout
+Timeout, in seconds, for kernel GSS contexts. This option allows you to force
new kernel contexts to be negotiated after
.I timeout
seconds, which allows changing Kerberos tickets and identities frequently.
The default is no explicit timeout, which means the kernel context will live
the lifetime of the Kerberos service ticket used in its creation.
.SH SEE ALSO
-.BR rpc.svcgssd(8)
+.BR rpc.svcgssd (8),
+.BR kerberos (1),
+.BR kinit (1),
+.BR krb5.conf (5)
.SH AUTHORS
.br
Dug Song <dugsong@umich.edu>
projects / nfs-utils.git / blobdiff