Provided by: sfs-server_0.8-0+pre20060720.1-1.1_i386
sfs_users - user-authentication database
The sfs_users file, maintained and used by the sfsauthd program, maps
public keys to local users and groups. It is roughly analogous to the
Unix /etc/passwd and /etc/group files. Each line of sfs_users can
specify a user or a group. Users are specified as follows (split into
two lines here only for clarity of presentation):
Note that the first USER is just the literal string USER. The rest of
the fields have the following meanings:
user is the unique name of a public key in the database.
Ordinarily it is the same as a username in the local password file.
However, it is also possible to add SFS users who do not have local
Unix accounts. It is also possible map multiple public keys to the
same local Unix account, as when several people have an account
with root privileges. In such cases, each key should be given a
unique name (e.g., dm/root, kaminsky/root, etc.).
uid uid is the user’s user ID on the given server.
version is the version number of this record in the users database.
Upon registration, this value is set to 1. Upon every subsequent
update, this value is incremented by 1.
gid gid is the users’s group ID on the given server.
This field is currently ignored, but in a future version may be
used to allow users to create ‘‘guest’’ accounts.
pubkey is an ASCII, human-readable representation of the user’s
public key. Can be either a Rabin or 2-Schnorr public key.
The privs field contains a comma-separated list of properties of
the account. Possible properties are as follows:
This property states that an SFS user corresponds to the local
Unix account account. In many settings, it is common to use
the unix= property to map every SFS user to a local Unix user
of the same name. The unix= property has several consequences.
First, if there is no local Unix user named account, this SFS
user will not be allowed to log in. Second, when the SFS user
logs in, SFS will search /etc/group for additional groups the
user might belong to. Third, the rexd remote login daemon will
allow remote login access to this account, using the shell and
home directory specified in /etc/passwd. Finally, on some
operating systems, SFS enforces account expiration dates
specified by /etc/shadow or /etc/spwd.db.
Indicates that this particular users has administrative
privileges in SFS. The option has no effect unless the
Userfile directive in sfsauthd_config specifies the -admin
option. For sfs_users files with the -admin option, the admin
privilege allows users to create and modify other user records
remotely, though currently client-side support for doing this
These properties are mostly of use with sfsaclsd, an
experimental server that is not part of the mainline SFS
srp srp is the server-side information for the SRP protocol. Unlike
the previous fields, this information must be kept secret. If the
information is disclosed, an attacker may be able to impersonate
the server by causing the sfskey add command to fetch the wrong
HostID. Note also that srp is specific to a particular hostname.
If you change the Location of a file server, users will need to
register new SRP.
privkey is actually opaque to sfsauthd. It is private, per-user
data that sfsauthd will return to users who successfully complete
the SRP protocol. Currently, sfskey users this field to store an
encrypted copy of a user’s private key, allowing the user to
retrieve the private key over the network.
If a user has chosen 2-Schnorr proactive signatures, the server’s
half of the private key is kept in this field.
audit contains the time, source IP address, and description of the
last update to this field. Useful in recovering from a compromised
Each group in sfs_users is specified by a line with the following
Here again the first GROUP is just the literal string GROUP, while the
remaining fields have the following meanings:
The name of the group.
gid The numeric group ID.
version is the version number of this record in the database. The
number increments when people edit groups through the sfskey
List of users who are allowed to edit the group membership list.
List of users who are in the group.
Properties of the group, mostly of use with sfsaclsd, an
experimental server that is not part of the mainline SFS
Information about the last time this record was modified through
the sfskey interface.
sfs_users files can be stored in one of three formats: plain ASCII,
database directories, and database files. (The latter two require SFS
to have been compiled with Sleepycat BerkeleyDB support.) The format
is determined by the extension of the file name. File names ending
.db/ are considered database directories; file names ending .db are
considered database files; everything else is considered ASCII. Only
read-only and exported public databases can be database files; read-
write databases must be directories, ending .db/. (The reason is that
read-write database files require write-ahead logging, which relies on
You should always edit sfs_users files using the vidb(8) command, for
two reasons. First, whenever editing files by hand, you run the risk
of overwriting concurrent updates by sfsauthd. vidb acquires the
necessary locks to prevent this from happening. Second, when editing a
database directory or file, vidb translates from the binary database
format into the ASCII format described above; when committing updates,
it also atomically modifies various secondary indexes that SFS relies
(Files in /etc/sfs supersede default versions in /usr/local/share/sfs.)
dirsearch(1), newaid(1), rex(1), sfsagent(1), sfskey(1), ssu(1),
sfs_config(5), sfs_hosts(5), sfs_srp_params(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/.