freebsd-dev/lib/libskey/skey.3

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.\" David L. Nugent. All Rights reserved.
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.Dd December 22, 1996
.Dt SKEY 3
.Os
.Sh NAME
.Nm skeylookup ,
.Nm skeyverify ,
.Nm skeychallenge ,
.Nm skeyinfo ,
.Nm skeyaccess ,
.Nm skey_getpass ,
.Nm skey_crypt
.Nd library routines for S/Key password control table access
.Sh LIBRARY
.Lb libskey
.Sh SYNOPSIS
.Fd #include <stdio.h>
.Fd #include <skey.h>
.Ft int
.Fn skeylookup "struct skey *mp" "const char *name"
.Ft int
.Fn skeyverify "struct skey *mp" "char *response"
.Ft int
.Fn skeychallenge "struct skey *mp" "const char *name" "char *challenge"
.Ft int
.Fn skeyinfo "struct skey *mp" "const char *name" "char *ss"
.Ft int
.Fn skeyaccess "char *user" "const char *port" "const char *host" "const char *addr"
.Ft char *
.Fn skey_getpass "const char *prompt" "struct passwd *pwd" "int pwok"
.Ft const char *
.Fn skey_crypt "char *pp" "char *salt" "struct passwd *pwd" "int pwok"
.Sh DESCRIPTION
These routes support the S/Key one time password system used for
accessing computer systems.
See
.Xr skey 1 
for more information about the S/Key system itself.
.Pp
.Pp
.Fn skeylookup
finds an entry in the one-time password database.
On success (an entry is found corresponding to the given name),
they skey structure passed by the caller is filled and 0 is
returned, with the file read/write pointer positioned at the
beginning of the record found.
If no entry is found corresponding to the given name, the file
read/write pointer is positioned at end of file and the routine
returns 1.
If the database cannot be opened or an access error occurs,
.Fn skeylookup
returns -1.
.Pp
The
.Fn skeyinfo
function looks up skey info for user 'name'.
If successful, the caller's skey structure is filled and
.Fn skeyinfo
returns 0.
If an optional challenge string buffer is given, it is updated.
If unsuccessful (e.g. if the name is unknown, or the database
cannot be accessed) -1 is returned.
.Pp
.Fn skeychallenge
returns an skey challenge string for 'name'.
If successful, the caller's skey structure is filled, and
the function returns 0, with the file read/write pointer
left at the start of the record.
If unsuccessful (ie. the name was not found), the function
returns -1 and the database is closed.
.Pp
.Fn skeyverify
verifies a response to an s/key challenge.
If this function returns 0, the verify was successful and
the database was updated.
If 1 is returned, the verify failed and the database remains
unchanged.
If -1 is returned, some sort of error occurred with the database,
and the database is left unchanged.
The s/key database is always closed by this call.
.Pp
The
.Fn skey_getpass
function may be used to read regular or s/key passwords.
The prompt to use is passed to the function, along with the
full (secure) struct passwd for the user to be verified.
.Fn skey_getpass
uses the standard library getpass on the first attempt at
retrieving the user's password, and if that is blank, turns
echo back on and retrieves the S/Key password.
In either case, the entered string is returned back to the
caller.
.Pp
The
.Fn skey_crypt
is a wrapper function for the standard library
.Xr crypt 3 ,
which returns the encrypted UNIX password if either the given
s/key or regular passwords are ok.
.Fn skey_crypt
first attempts verification of the given password via the skey
method, and will return the encrypted password from the
passwd structure if it can be verified, as though the user had
actually entered the correct UNIX password.
If s/key password verification does not work, then the password
is encrypted in the usual way and the result passed back to the
caller.
If the passwd structure pointer is NULL,
.Fn skey_crypt
returns a non-NULL string which could not possibly be a valid
UNIX password (namely, a string containing ":").
.Pp
The
.Fn skeyaccess
function determines whether traditional UNIX (non-S/Key) passwords
are permitted for any combination of user name, group member,
terminal port, host name, and network.  If UNIX passwords are allowed,
.Fn skeyaccess
returns a non-zero value.  If UNIX passwords are not allowed, it
returns 0.  See
.Xr skey.access 5
for more information on the layout and structure of the
skey.access configuration file which this function uses.
.Sh RETURN VALUES
See above.
.Sh SEE ALSO
.Xr skey 1 ,
.Xr skey.access 5
.Sh BUGS
No advisory locking is done on the s/key database to guard against
simultaneous access from multiple processes.
This is not normally a problem when keys are added to or updated
in the file, but may be problematic when keys are removed.
.Sh AUTHORS
.An Phil Karn ,
.An Neil M. Haller ,
.An John S. Walden ,
.An Scott Chasin