Provided by:
sfs-common_0.8-0+pre20060720.1-1.1_i386
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 inter‐
preted as a file descriptor number. The default is to use the environ‐
ment 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 com‐
mands--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 host‐
name 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 avail‐
able 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 # char‐
acters 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 key‐
label is stored internally in the private key, and is shown in the out‐
put 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 time‐
out 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 net‐
work 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 connec‐
tion 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 certi
fication 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 directo‐
ries $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 mak‐
ing 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 pro‐
gram returns a zero exit status, the agent will sign with the cur‐
rent 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 invoca‐
tions. If the user has chosen to accept a particular request auto‐
matically, 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 man‐
ually 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/pre‐
fix#suffix.
-c cost
Override the default computational cost of processing a pass‐
word, 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 # charac‐
ter) 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 can‐
not 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 key‐
name. 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 pre‐
fix#, 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 sup‐
presses 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 pass‐
word, 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 okey‐
name] [-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 pri‐
vate key share on all of the servers given. Specify -BES to sup‐
press 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 syn‐
tax. 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 host‐
name (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 $HOME/.sfs/authkeys are
loaded and hashed. Remote keys and local keys in non-standard
locations can be loaded into the hash with this option. The
keys will in turn be used to authenticate you to the servers
that you intend to update.
-w wkeyfile
Save the complete Schnorr key (both halves) to the file given.
Note that it is possible to non-interactively sign with this
key, so it is advised that it not be stored on network-accessi‐
ble media. The intended use for this option is to allow saving
of both halves to a floppy disk or to a CD-R, so that in a
worst case scenario, the original key is still recoverable.
sfskey gethash [-6p] keyname
Retrieves a public key specified by keyname, which can be local
(from a local file) or remote (from an authentication server).
Remote keynames can contain fully-specified self-certifying host‐
names, or simple DNS names. In the latter case, sfskey uses SRP to
establish a secure connection to the authentication server.
-6 Display the hash in base-64 encoding.
sfskey group [-a key] [-E] [-C] [-L version] [-m {+|-}membername] [-o
{+|-}ownername] groupname
Retrieves, creates, and modifies group lists on an authentication
server. groupname is the name of the group, which can take an
optional DNS hostname or self-certifying hostname. Given a simple
DNS hostname, the server will attempt SRP to retrieve the server’s
public key. Using the -a is another way to retrieve the key.
With no options, sfskey will query the authentication server for
the group and print out the result. The group owners and members
listed will be exactly as they appear in the authentication
server’s database. The various options are described below.
-a key
This option can be supplied arbitrarily many times, once for
each key that should be loaded into sfskey for this session.
Keynames are specified as described above, and can be remote
(via SRP) or the path to a local file. Usually it will not be
necessary to specify keys in the keys directory
($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 group‐
name. If the group already exists, sfskey returns an error.
-L This option tells sfskey to retrieve a group’s changelog begin‐
ning 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 stan‐
dard output. If Location is simply -, returns the name of the cur‐
rent 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 stan‐
dard Rabin keys, and thus treats arg-i as [user][@]host arguments.
If host is a regular hostname, then SRP will be required to authen‐
ticate the host. If host is a full SFS pathname, then sfskey
passwd will look for keys in $HOME/.sfs/authkeys that can authenti‐
cate 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 authen‐
ticated 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
$HOME/.sfs/identity, unless -u is used, in which case the default
is to generate a new key in the current directory. For keys that
contain the special trailing character #, sfskey will implicitly
determine whether the user intends to generate or access a key. If
the command is invoked as root with the -u flag, then generation is
assumed. Similarly, if any of the options -bcgp are used, genera‐
tion is assumed. Otherwise, sfskey will first attempt to access
the most recent key matching keyname, and then will revert to gen‐
eration if the access fails.
If a user wishes to reuse a public key already registered with
another server, the user can specify user@server for keyname.
-f Force reregistration. Ordinarily, sfskey gen will fail if a
record for the given user already exists on the server.
-g Force key generation. When using keynames of the form prefix#,
sfskey register will always generate then next available key
with the prefix prefix in the standard keys directory
($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 mod‐
ulus 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 sav‐
ing 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 log‐
ging the user out of all file systems will likely not be visi‐
ble--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-certify‐
ing 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-certify‐
ing 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-certify‐
ing 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 manage‐
ment 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 fol‐
lowed 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 pro‐
gram 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 $HOME/.sfs/identity. Then you can run
sfskey update [user]@host for each server on which you need to
change your public key.
To authenticate you to the servers on which updates are requested,
sfskey update will first use the keys given via -a arguments; it
will then search keys in the standard key direc‐
tory--$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 $HOME/.sfs/identity
will be assumed.
The -r provides a shortcut for updating SRP information, if, for
instance, the authserver has changed its realm information. Invok‐
ing sfskey update -r [user]@host is equivalent to sfskey update -k
[user]@host host.
Several options control sfskey update’s behavior:
-E Do not send encrypted secret key information to the server.
-S Do not send SRP information to the server--this will prevent
the user from using SRP to connect to the server, but will also
prevent the server from gaining any information that could be
used by an attacker to mount an off-line guessing attack on the
user’s password. Implies -E
-a okeyname
This option can be supplied arbitrarily many times, once for
each key that should be loaded into sfskey for this session.
Keynames are specified as described above, and can be remote
(via SRP) or the path to a local file. Usually it will not be
necessary to specify keys in the keys directory
($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, $HOME/.sfs/identity is assumed. Note that
the -k flag can be specified only once.
-r [user][@]host
Update SRP information of a key on a remote host. Equivalent to
sfskey update -k [user]@host [user@]host. Cannot be used with
the -akS options.
-s srp_params is the path of a file generated by sfskey srpgen,
and specifies the parameters to use in generating SRP informa‐
tion for the server. The default is to get SRP parameters from
the server, or look in /usr/local/share/sfs/sfs_srp_params.
sfskey user [-a key] username
Retrieves a user record from an authentication server. username is
the name of the user, which can take an optional DNS hostname or
self-certifying hostname. Given a simple DNS hostname, the server
will attempt SRP to retrieve the server’s public key. Using the -a
is another way to retrieve the key.
sfskey will query the authentication server for the user and print
out the result.
-a key
This option can be supplied arbitrarily many times, once for
each key that should be loaded into sfskey for this session.
Keynames are specified as described above, and can be remote
(via SRP) or the path to a local file. Usually it will not be
necessary to specify keys in the keys directory
($HOME/.sfs/authkeys) as they are considered automatically.
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), sfs‐
rosd(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 com‐
mand 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