Provided by: sfs-common_0.8-0+pre20060720.1-1.1_i386 bug

NAME

       sfskey - SFS key manager

SYNOPSIS

       sfskey [-S sock] [-p pwfd] command [arg ...]

DESCRIPTION

       The sfskey command performs a variety of key management tasks, from
       generating and updating keys to controlling users’ SFS agents.  The
       general usage for sfskey is:

       sfskey [-S sock] [-p pwfd] command [arg ...]

       -S specifies a UNIX domain socket sfskey can use to communicate with
       your sfsagent socket.  If sock begins with -, the remainder is
       interpreted as a file descriptor number.  The default is to use the
       environment variable SFS_AGENTSOCK if that exists.  If not, sfskey asks
       the file system for a connection to the agent.

       The -p option specifies a file descriptor from which sfskey should read
       a passphrase, if it needs one, instead of attempting to read it from
       the user’s terminal.  This option may be convenient for scripts that
       invoke sfskey.  For operations that need multiple passphrases, you must
       specify the -p option multiple times, once for each passphrase.

       In SFS 0.7, two-party proactive Schnorr signatures (2-Schnorr for
       short) are supported in addition to Rabin signatures.  One half of the
       2-Schnorr key is stored on the designated signature sever, while the
       other is stored locally to file, or remotely via SRP.  Unlike Rabin
       keys, 2-Schnorr keys can fail to load when a signature server becomes
       unavailable.  For this reason, sfskey supports multiple private-key
       shares that correspond to the same public key; this way, a user can
       maintain a series of backup signature servers in case his primary
       server becomes unavailable.  By default, sfskey never stores both
       halves of a 2-Schnorr key to the same machine, so as to enforce key
       sharing.  To this effect, 2-Schnorr employs special sfskey
       commands--sfskey 2gen and sfskey 2edit.

       As of SFS 0.7, there is a new convention for saving and naming private
       keys.  By default, keys will be stored locally in $HOME/.sfs/authkeys,
       and will be in the following forms:

           user@host1#n
           user@host1#n,p.host2,m

       The first form is for standard Rabin keys.  The second is for 2-Schnorr
       proactive signature keys.  In the above examples, host1 is the the full
       hostname of the generating host, n is the public key version, p is the
       priority of the signing host (1 is the highest) host2 is the full
       hostname of the signing host, and m is the private key version.

       In general, these details can remain hidden, in that the symbolic link
       $HOME/.sfs/identity points to the most recent key generated in
       $HOME/.sfs/authkeys, and most sfskey commands have reasonable defaults.
       However, there is a command-line system for accessing and generating
       specific keys.  A blank keyname and the special keyname # refer to the
       default key $HOME/.sfs/identity during key access and the next
       available key during key generation.  Keynames containing a # character
       but not containing a / character are assumed to refer to keys in the
       $HOME/.sfs/authkeys directory.  When given files of the form prefix#,
       sfskey looks in the default directory for the most recent key with the
       given prefix during key access, and the next available key with the
       given prefix during key generation.  For keys of the form name#suffix,
       sfskey will look in the $HOME/.sfs/authkeys directory for keys that
       match the given name exactly. sfskey treats keys with / characters as
       regular files; it treats keys that contain @ characters but no #
       characters as keys stored on remote machines.

       Finally, one should note that SFS keys have both a keyname and also a
       keylabel.  sfskey uses the former to retrieve keys from the local file
       system or from remote servers.  The latter is less important; the
       keylabel is stored internally in the private key, and is shown in the
       output of the sfskey list command.

OPTIONS

       sfskey add [-t [hrs:]min] [keyname]
       sfskey add [-t [hrs:]min] [user]@hostname
           The add command loads and decrypts a private key, and gives the key
           to your agent.  Your agent will use it to try to authenticate you
           to any file systems you reference.  The -t option specifies a
           timeout after which the agent should forget the private key.

           In the first form of the command, the key indicated by keyname is
           loaded.  If keyname is omitted, or # is supplied, then the default
           key is $HOME/.sfs/identity. If the key supplied is a 2-Schnorr key,
           then sfskey add will attempt to load backup keys should the primary
           key fail due to an unavailable signature server.

           The second form of the command fetches a private key over the
           network using the SRP (http://srp.stanford.edu/) protocol.  SRP
           lets users establish a secure connection to a server without
           remembering its public key.  Instead, to prove their identities to
           each other, the user remembers a secret password and the server
           stores a one-way function of the password (also a secret).  SRP
           addresses the fact that passwords are often poorly chosen; it
           ensures that an attacker impersonating one of the two parties
           cannot learn enough information to mount an off-line password
           guessing attack--in other words, the attacker must interact with
           the server or user on every attempt to guess the password.

           The sfskey update, sfskey register, sfskey 2gen and sfskey 2edit
           commands let users store their private keys on servers, and
           retrieve them using the add command.  The private key is stored in
           encrypted form, using the same password as the SRP protocol (a safe
           design as the server never sees any password-equivalent data).

           Because the second form of sfskey add establishes a secure
           connection to a server, it also downloads the servers HostID
           securely and creates a symbolic link from /sfs/hostname to the
           server’s self-certifying pathname.

           When invoking sfskey add with the SRP syntax, sfskey will ask for
           the user’s password with a prompt of the following form:

           Passphrase for user@servername/nbits:

           user is simply the username of the key being fetched from the
           server.  servername is the name of the server on which the user
           registered his SRP information.  It may not be the same as the
           hostname argument to sfskey if the user has supplied a hostname
           alias (or CNAME) to sfskey add.  Finally, nbits is the size of the
           prime number used in the SRP protocol.  Higher values are more
           secure; 1,024 bits should be adequate.  However, users should
           expect always to see the same value for nbits (otherwise, someone
           may be trying to impersonate the server).

       sfskey certclear
           Clears the list of certification programs the agent runs.  See
           certprog, for more details on certification programs.

       sfskey certlist [-q]
           Prints the list of certification programs the agent runs.  See
           certprog, for more details on certification programs.

       sfskey certprog [-p prefix] [-f filter] [-e exclude] prog [arg ...]
           The certprog command registers a command to be run to lookup
           HostIDs on the fly in the /sfs directory.  This mechanism can be
           used for dynamic server authentication--running code to lookup
           HostIDs on-demand.  When you reference the file /sfs/prefix/name,
           your agent will run the command:

           prog arg ... name

           If the program succeeds and prints dest to its standard output, the
           agent will then create a symbolic link:

           /sfs/prefix/name -> dest

           The -p flag can be omitted, and the link is /sfs/name - >dest.
           prefix can be more than one directory deep (i.e., a series of path
           components separated by /).  If so, the first certification program
           whose prefix matches at the beginning of prefix is run.  The
           remaining path components are passed to prog.  For example:

             NEED EXAMPLE

           filter is a perl-style regular expression.  If it is specified,
           then name must contain it for the agent to run prog.  exclude is
           another regular expression, which, if specified, prevents the agent
           from running prog on names that contain it (regardless of filter).

           The program dirsearch can be used with certprog to configure
           certification paths--lists of directories in which to look for
           symbolic links to HostIDs.  The usage is:

           dirsearch [-clpq] dir1 [dir2 ...] name

           dirsearch searches through a list of directories dir1, dir2, ...
           until it finds one containing a file called name, then prints the
           pathname dir/name.  If it does not find a file, dirsearch exits
           with a non-zero exit code.  The following options affect
           dirsearch’s behavior:

           -c  Print the contents of the file to standard output, instead of
               its pathname.

           -l  Require that dir/name be a symbolic link, and print the path of
               the link’s destination, rather than the path of the link
               itself.

           -p  Print the path dir/name.  This is the default behavior anyway,
               so the option -p has no effect.

           -q  Do not print anything.  Exit abnormally if name is not found in
               any of the directories.

           As an example, to lookup self-certifying pathnames in the
           directories $HOME/.sfs/known_hosts and /mit, but only accepting
           links in /mit with names ending .mit.edu, you might execute the
           following commands:

             % sfskey certprog dirsearch $HOME/.sfs/known_hosts
             % sfskey certprog -f ’\.mit\.edu$’ /mnt/links

       sfskey confclear
           Clears the confirmation program that the agent runs.  See confprog,
           for more details on confirmation programs.

       sfskey conflist [-q]
           Prints the confirmation program that the agent runs.  See confprog,
           for more details on confirmation programs.

       sfskey confprog prog [arg ...]
           The confprog command registers a command to be run by the agent
           when it receives an authentication request.  The agent provides the
           program with the following command line arguments: the machine
           making the request, the machine that the requestor wants to access,
           the service (e.g., file system, remote execution facility), the
           current key that the agent will try signing with, and a list of all
           of the keys that the agent has available.  If the confirmation
           program returns a zero exit status, the agent will sign with the
           current key; otherwise, it will refuse to sign with that key and
           will try the next available one.

           The confirmation program can be very simple (always answer yes, for
           example), or quite complex.  SFS comes with an example confirmation
           program written in Python/GTK2 (confirm.py).  When called, the
           script can pop up a dialog box which asks the user what he wants to
           do with the request.  The user has several options: reject, accept,
           accept and allow all futures request from the requesting machine to
           access the named machine, accept and allow access from requestor to
           any machine in the named machine’s domain, or accept and allow
           access from requestor to any machine.  The script saves the user’s
           preferences in a data file which it consults on subsequent
           invocations.  If the user has chosen to accept a particular request
           automatically, the script returns zero (success) without popping up
           a dialog box.

           Confirmation programs allow the user to manage trust policies when
           working with machines that are trusted to different degrees.  For
           example, a user might trust the machine on his lan but want to
           manually confirm requests from machines in a shared compute
           cluster.

       sfskey delete keyname
           Deletes private key keyname from the agent (reversing the effect of
           an add command).

       sfskey deleteall
           Deletes all private keys from the agent.

       sfskey edit [-LP] [-o keyname] [-c cost] [-l label] [keyname]
           Changes the passphrase, passphrase ‘‘cost’’, or name of a public
           key.  Can also download a key from a remote server via SRP and
           store it in a file.

           keyname can be a file name, or it can be of the form [user]@server,
           in which case sfskey will fetch the key remotely and outfile must
           be specified.  If keyname is unspecified the default is
           $HOME/.sfs/identity.  If keyname is #, then sfskey edit will search
           for the next appropriate keyname in $HOME/.sfs/authkeys.  In this
           case, sfskey edit will update $HOME/.sfs/identity to point to this
           new key by default.

           The options are:

           -L  Does not set symlink in the case that keyname is #.

           -P  Removes any password from the key, so that the password is
               stored on disk in unencrypted form.

           -o keyname
               Specifies the file to which the edited key should be written.
               A keyname of # implies that sfskey edit should generate the
               next available default key in $HOME/.sfs/authkeys.  A keyname
               of the form prefix# implies that sfskey edit should generate
               the next available key in $HOME/.sfs/authkeys with the prefix
               prefix.  A keyname of the form prefix#suffix implies that
               sfskey edit should make a key named
               $HOME/.sfs/authkeys/prefix#suffix.

           -c cost
               Override the default computational cost of processing a
               password, or PwdCost.

           -l label
               Specifies the label of the key that shows up in sfskey list.

       sfskey 2edit -[Smp] [-l label] [-S | -s srpfile] [keyname1 keyname2
       ...]
           Refreshes a 2-Schnorr key by re-sharing a secret between a server
           and a client. In the case of a compromised client or server, it is
           recommended to refresh a 2-Schnorr key with this command.  If both
           the client and the server have been compromised, a refresh will be
           of little use.

           Use sfskey 2edit by supplying the keys that you wish to have
           updated.  Keynames are given in standard sfskey style.  Keynames
           must be either remote keynames (i.e., contain a @ but no #
           character) or stored in the standard keys directory (i.e., contain
           a # but no / character).  For remote keys, SRP will be used to
           download the key from the server, and the updated, encrypted client
           private keyhalf will be written back to the server along with the
           new server keyhalf.  No file will be saved locally.  For keys
           stored in $HOME/.sfs/authkeys, sfskey 2edit will update the server
           private keyhalf, and write the corresponding client private keyhalf
           out to $HOME/.sfs/authkeys under a new filename.  By default,
           sfskey 2edit will also write the new encrypted client private
           keyhalf back to the server for later SRP retrieval.

           If no key is specified, the default key, $HOME/.sfs/identity is
           assumed.

           -E  Do not update the encrypted private client key stored on the
               server.

           -S  Do not update SRP information on the server.  This option
               cannot be used if some of the keynames specified are for remote
               keys.

           -m  Refresh multiple keys.  If you have multiple private splits of
               the same private key, this flag will automatically update them
               all, given that you’ve specified one of them.  If you run
               sfskey 2edit -m, with no additional arguments or keynames,
               sfskey will refresh all current default keys.

           -p  Change password before writing keys out to disk or server.

           -l label
               Specifies the label of the key that shows up in sfskey list.

           -s srpfile
               Get SRP parameters from the file srpfile.

       sfskey gen [-KP] [-b nbits] [-c cost] [-l label] [keyname]
           Generates a new Rabin public/private key pair and stores it in
           keyname.  It omitted keyname defaults to the next available Rabin
           key in $HOME/.sfs/authkeys.  If keyname contains a / character, it
           will be treated as a regular Unix file.  If keyname is of the form
           prefix#, sfskey gen will look for the next available Rabin key in
           $HOME/.sfs/authkeys with the prefix prefix.  If keyname contains a
           non-terminal # character, it will be treated as a fully-specified
           keyname to be saved in $HOME/.sfs/authkeys.

           Note that sfskey gen is only useful for generating Rabin keys.  Use
           either sfskey register or sfskey 2gen to generate 2-Schnorr keys.

           -K  By default, sfskey gen asks the user to type random text with
               which to seed the random number generator.  The -K option
               suppresses that behavior.

           -P  Specifies that sfskey gen should not ask for a passphrase and
               the new key should be written to disk in unencrypted form.

           -b nbits
               Specifies that the public key should be nbits long.

           -c cost
               Override the default computational cost of processing a
               password, or PwdCost.

           -l label
               Specifies the label of the key that shows up in sfskey list.
               Otherwise, the user will be prompted for a name.

       sfskey 2gen [-BEKP] [-a {hostid | -}] [-b nbits] [-c cost] [-k
       okeyname] [-l label] [-S | -s srpfile] [-w wkeyfile] [nkeyname]
           Generates a new 2-Schnorr keypair for each of the servers specified
           by the -a flag.  All keypairs will correspond to the same public
           key.  The new keys will be saved locally to the files given by
           nkeyname in the usual fashion: if nkeyname is of the form prefix#,
           then sfskey 2gen will look for the next available 2-Schnorr key in
           $HOME/.sfs/authkeys with the prefix prefix.  If no nkeyname is
           given, it will find the next available keyname in
           $HOME/.sfs.authkeys with the default prefix (user@host).

           Note that by default, this operation will update the public key,
           the encrypted private key, the SRP information, and the server
           private key share on all of the servers given.  Specify -BES to
           suppress updates of these fields.

           -a -
           -a hostid
               Can be specified arbitrarily many times, once for each server
               that will accept the server private half of the 2-Schnorr key
               being generated.  Note that the same public key will be used
               for all servers.  To specify the local host, use the first
               syntax.  If SRP is used to download a key from host host (e.g.,
               -k user@host), then you can specify that host by its simple
               hostname (e.g., -a host).  If SRP was not used to connect to a
               host host, then -a requires a complete SFS host identifier
               (i.e., @Location,HostID).

           -B  Do not update the public key on the given servers.

           -E  Do not update the encrypted private key field on the given
               servers.

           -K
           -P
           -c cost
           -l label
           -s srpfile
               See sfskey gen.  These options behave similarly.

           -S  Do not update the SRP information on the server.

           -b nbits
               Specifies the number of bits for the 2-Schnorr modulus p.  The
               security of 2-Schnorr is related to the discrete log problem
               over Z_p*; values over 1024 are suggested for this parameter,
               and reasonable defaults are chosen if this parameter is not
               specified.

           -k keyname
               Specify this option arbitrarily many times to keys into memory
               for sfskey.  By default, all keys from $HOME/.sfs/authkeys are
               loaded and hashed.  Remote keys and local keys in non-standard
               locations can be loaded into the hash with this option.  The
               keys will in turn be used to authenticate you to the servers
               that you intend to update.

           -w wkeyfile
               Save the complete Schnorr key (both halves) to the file given.
               Note that it is possible to non-interactively sign with this
               key, so it is advised that it not be stored on network-
               accessible media.  The intended use for this option is to allow
               saving of both halves to a floppy disk or to a CD-R, so that in
               a worst case scenario, the original key is still recoverable.

       sfskey gethash [-6p] keyname
           Retrieves a public key specified by keyname, which can be local
           (from a local file) or remote (from an authentication server).
           Remote keynames can contain fully-specified self-certifying
           hostnames, or simple DNS names.  In the latter case, sfskey uses
           SRP to establish a secure connection to the authentication server.

           -6  Display the hash in base-64 encoding.

       sfskey group [-a key] [-E] [-C] [-L version] [-m {+|-}membername] [-o
       {+|-}ownername] groupname
           Retrieves, creates, and modifies group lists on an authentication
           server.  groupname is the name of the group, which can take an
           optional DNS hostname or self-certifying hostname.  Given a simple
           DNS hostname, the server will attempt SRP to retrieve the server’s
           public key.  Using the -a is another way to retrieve the key.

           With no options, sfskey will query the authentication server for
           the group and print out the result.  The group owners and members
           listed will be exactly as they appear in the authentication
           server’s database.  The various options are described below.

           -a key
               This option can be supplied arbitrarily many times, once for
               each key that should be loaded into sfskey for this session.
               Keynames are specified as described above, and can be remote
               (via SRP) or the path to a local file.  Usually it will not be
               necessary to specify keys in the keys directory
               ($HOME/.sfs/authkeys) as they are considered automatically.

           -E  With this option, sfskey will ask the authentication server to
               ‘‘expand’’ the owners and members lists first by computing the
               transitive closure of all groups and remote users.  The
               expanded group will contain only public key hashes and user
               names (local to the remote authentication server).

           -C  This option tells sfskey to create a new group called
               groupname.  If the group already exists, sfskey returns an
               error.

           -L  This option tells sfskey to retrieve a group’s changelog
               beginning at version version up through the most recent
               version.  The changelog contains the updates made to the
               group’s members list, plus the group’s current refresh and
               timeout values.

           -m {+|-}membername
           -o {+|-}ownername
               This option tells sfskey to add (+) or subtract (-) the given
               member or owner name to or from the given group.  membernames
               and ownernames must be of the form "u=<user>", "g=<group>" or
               "p=<pkhash>".  The "<user>" and "<group>" names can be local or
               remote, but remote names must contain the fully-qualified self-
               certifying hostname.  Duplicate member names and owner names
               are removed from the group before it is updated.  Removals of
               names that don’t exists on the given list are ignored.  This
               option may be given more than once.

       sfskey help
           Lists all of the various sfskey commands and their usage.

       sfskey hostid Location
       sfskey hostid Location@t{%}port
       sfskey hostid -
           Retrieves a self-certifying pathname insecurely over the network
           and prints @Location,HostID or @Location@t{%}port,HostID to
           standard output.  If Location is simply -, returns the name of the
           current machine, which is not insecure.

           -s service
               The default service is file service, sfs (except when using -).
               This option selects a different SFS service.  Possible values
               for service are sfs, authserv, and rex.

       sfskey kill
           Kill the agent.

       sfskey list [-ql]
           List the public keys whose private halves the the agent holds.

           -q  Suppresses the banner line explaining the output.

           -l  Lists the actual value of public keys, in addition the the
               names of the keys.

       sfskey norevokeset HostID ...
       sfskey norevokelist
       sfskey passwd [-Kp] [-S | -s srpfile] [-b nbits] [-c cost] [-l label]
       [arg1] [arg2] ...
           The sfskey passwd command is a high-level command for ‘‘changing
           passwords’’ in SFS.  In the case of proactive keys, sfskey passwd
           will simply refresh keys via sfskey 2edit functionality.  In the
           case of Rabin keys, sfskey passwd generates a new Rabin key and
           updates the given servers. By default, sfskey passwd assumes
           standard Rabin keys, and thus treats arg-i as [user][@]host
           arguments.  If host is a regular hostname, then SRP will be
           required to authenticate the host.  If host is a full SFS pathname,
           then sfskey passwd will look for keys in $HOME/.sfs/authkeys that
           can authenticate the user to that particular server.  In the case
           of proactive 2-Schnorr keys, sfskey passwd will treat arg-i as
           local or remote keynames.

           If no options or arguments are given, sfskey passwd will look to
           the default key given by $HOME/.sfs/identity.  If the default key
           is a proactive 2-Schnorr key, then all current 2-Schnorr keys in
           .sfs/authkeys are refreshed.  If the default key is a Rabin key,
           then the users key on the local machine is updated.

           -p  Specifies proactive mode.  Will treat arguments arg1 through
               arg-n as keynames, whether local or remote.  By default, sfskey
               passwd operates under the assumption that the key to update is
               a Rabin key.

           -K
           -S
           -s srpfile
           -b nbits
           -c cost
           -l label
               These options are the same as for sfskey gen.  Briefly, -S
               turns of SRP, -K disables keyboard randomness query, -s is used
               to supply an SRP parameters file and is mutually exclusive with
               -S, -b specifies the size of the key in bits, -c specifies the
               secret key encryption cost, and -l specifies the label for the
               key, as seen in sfskey list.

       sfskey register [-fgpPK] [-S | -s srpfile] [-b nbits] [-c cost] [-u
       user] [-l label] [-w filename] [keyname]
           The sfskey register command lets users who are logged into an SFS
           file server register their public keys with the file server for the
           first time.  Subsequent changes to their public keys can be
           authenticated with the old key, and must be performed using sfskey
           update or sfskey 2gen.  The superuser can also use sfskey register
           when creating accounts.

           keyname is the private key to use.  If keyname does not exist and
           is a pathname, sfskey will create it.  The default keyname is
           $HOME/.sfs/identity, unless -u is used, in which case the default
           is to generate a new key in the current directory.  For keys that
           contain the special trailing character #, sfskey will implicitly
           determine whether the user intends to generate or access a key.  If
           the command is invoked as root with the -u flag, then generation is
           assumed.  Similarly, if any of the options -bcgp are used,
           generation is assumed.  Otherwise, sfskey will first attempt to
           access the most recent key matching keyname, and then will revert
           to generation if the access fails.

           If a user wishes to reuse a public key already registered with
           another server, the user can specify user@server for keyname.

           -f  Force reregistration.  Ordinarily, sfskey gen will fail if a
               record for the given user already exists on the server.

           -g  Force key generation.  When using keynames of the form prefix#,
               sfskey register will always generate then next available key
               with the prefix prefix in the standard keys directory
               ($HOME/.sfs/authkeys).  If sfskey register is being run as root
               with the -u option, then access to the standard keys directory
               $HOME/.sfs/authkeys will not be allowed.  Hence, the key will
               simply be generated in the current directory.

           -p  Generate a new proactive 2-Schnorr key.  Implies the -g flag.

           -K
           -P
           -l label
           -b nbits
           -c cost
           -s srpfile
               These options are the same as for sfskey gen.  -K and -b have
               no effect if the key already exists.  They all imply the -g
               flag. If -p is given, then -b will specify the size of the
               modulus p used in 2-Schnorr.  Without -p, -b will specify the
               size of pq in Rabin.

           -S  Do not register any SRP information with the server--this will
               prevent the user from using SRP to connect to the server, but
               will also prevent the server from gaining any information that
               could be used by an attacker to mount an off-line guessing
               attack on the user’s password.

           -u user
               When sfskey register is run as root, specifies a particular
               user to register.

           -w filename
               When generating a proactive key, saves the complete key out to
               the given file.  Will raise an error if supplied without the -p
               flag.  For security reasons, this should only be used when
               saving to removable media (e.g., /floppy/complete-key-2).  It
               is a substantial security risk to leave the complete key on a
               file system that might be compromised.

           sfsauthd_config must have a Userfile with the -update and -passwd
           options to enable use of the sfskey register.

       sfskey reset
           Clear the contents of the /sfs directory, including all symbolic
           links created by sfskey certprog and sfskey add, and log the user
           out of all file systems.

           Note that this is not the same as deleting private keys held by the
           agent (use deleteall for that).  In particular, the effect of
           logging the user out of all file systems will likely not be
           visible--the user will automatically be logged in again on-demand.

       sfskey revokegen [-r newkeyfile [-n newhost]] [-o oldhost] oldkeyfile
       sfskey revokelist
       sfskey revokeclear
       sfskey revokeprog [-b [-f filter] [-e exclude]] prog [arg ...]
       sfskey select [-f] keyname
           Select the given key as the default key; set $HOME/.sfs/identity to
           point to the key given by keyname.  It cannot be an SRP key.

           -f  Force overwrite.  If current $HOME/.sfs/identity is a regular
               file, sfskey select will overwrite it.

       sfskey sesskill remotehost
           Kill the rex session to the server specified by remotehost, where
           remotehost is any unique prefix of the remote host’s self-
           certifying hostname (found under the "TO" column in the output to
           sfskey sesslist).

       sfskey sesslist
           List the rex sessions that the agent is maintaining.

       sfskey srpgen [-b nbits] file
           Generate a new sfs_srp_params file.

       sfskey srpclear
           Clears the in-memory cache of server self-certifying hostnames
           built from SRP results.  See srplist, for more details on this
           cache.

       sfskey srplist
           Prints the in-memory cache of server self-certifying hostnames
           built from SRP results.  This cache maps SRP names to self-
           certifying hostnames.  SRP names are of the form user@host.  Sample
           output of the sfskey srplist command might be

             % sfskey srplist
             alice@pdos.lcs.mit.edu      @amsterdam.lcs.mit.edu,bkfce6jdbmdbzfbct36qgvmpfwzs8exu
             alice@redlab.lcs            @redlab.lcs.mit.edu,gnze6vwxtwssr8mc5ibae7mtufhphzsk
             alice@ludlow.scs.cs.nyu.edu @ludlow.scs.cs.nyu.edu,hcbafipmin3eqmsgak2m6heequppitiz

           Currently, the agent consults this cache and adds new mappings to
           it when a user invokes REX with a DNS (SRP) name.  If the name is
           in the agent’s cache, REX will use the corresponding self-
           certifying hostname to authenticate the server.  If not, REX will
           use SRP to fetch the server’s public key and then add a new mapping
           to the agent’s cache.

       sfskey srpcacheprogclear
           Clears the SRP cache management program that the agent runs.  See
           srpcacheprog, for more details on cache management programs.

       sfskey srpcacheproglist [-q]
           Prints the SRP cache management program that the agent runs.  See
           srpcacheprog, for more details on confirmation programs.

       sfskey srpcacheprog prog [arg ...] The
           srpcacheprog command registers a command to be run by the agent in
           order to manage an on-disk copy of the in-memory SRP name cache
           (described above; ).  The agent will invoke the SRP cache
           management program with zero arguments when it wants to load the
           on-disk cache into memory and exactly one argument when it wants to
           add a new entry to the on-disk cache.  If no SRP cache management
           program is set, the agent will simply maintain an in-memory version
           which will be lost when the agent is restarted.

           In the first case (load), the program output must consist of one
           mapping per line.  Each mapping must consist of the SRP name
           followed by a single space followed by the self-certifying
           hostname. See srplist, for an example of what each of these fields
           might look like.  In the second case (store), the agent’s argument
           to the program will consist of a single mapping, to be added to the
           on-disk cache.  The mapping will have the same format described
           above: the SRP name followed by a single space followed by the
           self-certifying hostname (no trailing newline).

       sfskey update [-fE] [-S | -s srp_params] [-r srpkey] [-a okeyname] [-k
       nkeyname] server1 server2 ...
           Change a user’s public key and SRP information on an SFS file
           server.  To change public keys, typically you should generate a new
           public key and store it in $HOME/.sfs/identity.  Then you can run
           sfskey update [user]@host for each server on which you need to
           change your public key.

           To authenticate you to the servers on which updates are requested,
           sfskey update will first use the keys given via -a arguments; it
           will then search keys in the standard key
           directory--$HOME/.sfs/authkeys.

           At least one server argument is required.  As usual, the string
           ‘‘-’’ denotes the localhost. The servers specified can be either
           full SFS hostnames of the form [user]@Location,HostId, or standard
           hostnames of the form [user@]Location.  In the latter case, SRP is
           assumed, and the corresponding private key is automatically loaded
           into sfskey.

           The new key that is being pushed to the server is given by the -k
           flag.  If this is not provided, the default key $HOME/.sfs/identity
           will be assumed.

           The -r provides a shortcut for updating SRP information, if, for
           instance, the authserver has changed its realm information.
           Invoking sfskey update -r [user]@host is equivalent to sfskey
           update -k [user]@host host.

           Several options control sfskey update’s behavior:

           -E  Do not send encrypted secret key information to the server.

           -S  Do not send SRP information to the server--this will prevent
               the user from using SRP to connect to the server, but will also
               prevent the server from gaining any information that could be
               used by an attacker to mount an off-line guessing attack on the
               user’s password.  Implies -E

           -a okeyname
               This option can be supplied arbitrarily many times, once for
               each key that should be loaded into sfskey for this session.
               Keynames are specified as described above, and can be remote
               (via SRP) or the path to a local file.  Usually it will not be
               necessary to specify keys in the keys directory
               ($HOME/.sfs/authkeys) as they are considered automatically.

           -f  If there is a change in SRP realm information, the -f flag will
               force an update.  Normally, the user is prompted to verify.

           -k nkeyname
               Specifies the new key to push to the server. Can be an SRP key,
               a local file, or a keyname with a ’#’ sign, signifying a key
               stored in the keys directory, $HOME/.sfs/authkeys. If this flag
               is not specified, $HOME/.sfs/identity is assumed.  Note that
               the -k flag can be specified only once.

           -r [user][@]host
               Update SRP information of a key on a remote host. Equivalent to
               sfskey update -k [user]@host [user@]host.  Cannot be used with
               the -akS options.

           -s  srp_params is the path of a file generated by sfskey srpgen,
               and specifies the parameters to use in generating SRP
               information for the server.  The default is to get SRP
               parameters from the server, or look in
               /usr/local/share/sfs/sfs_srp_params.

       sfskey user [-a key] username
           Retrieves a user record from an authentication server.  username is
           the name of the user, which can take an optional DNS hostname or
           self-certifying hostname.  Given a simple DNS hostname, the server
           will attempt SRP to retrieve the server’s public key.  Using the -a
           is another way to retrieve the key.

           sfskey will query the authentication server for the user and print
           out the result.

           -a key
               This option can be supplied arbitrarily many times, once for
               each key that should be loaded into sfskey for this session.
               Keynames are specified as described above, and can be remote
               (via SRP) or the path to a local file.  Usually it will not be
               necessary to specify keys in the keys directory
               ($HOME/.sfs/authkeys) as they are considered automatically.

SEE ALSO

       dirsearch(1), newaid(1), rex(1), sfsagent(1), ssu(1), sfs_config(5),
       sfs_hosts(5), sfs_srp_params(5), sfs_users(5), sfsauthd_config(5),
       sfscd_config(5), sfsrosd_config(5), sfsrwsd_config(5), sfssd_config(5),
       sfs_environ(7), funmount(8), nfsmounter(8), sfsauthd(8), sfscd(8),
       sfsrosd(8), sfsrwcd(8), sfsrwsd(8), sfssd(8), vidb(8)

       The full documentation for SFS is maintained as a Texinfo manual.  If
       the info and SFS programs are properly installed at your site, the
       command info SFS should give you access to the complete manual.

       For updates, documentation, and software distribution, please see the
       SFS website at http://www.fs.net/.

AUTHOR

       sfsdev@redlab.lcs.mit.edu