OpenBSD-4.6/lib/libc/gen/authenticate.3

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.\"	BSDI $From: authenticate.3,v 2.7 1998/09/03 20:27:20 prb Exp $
.Dd $Mdocdate: April 4 2008 $
.Dt AUTHENTICATE 3
.Os
.Sh NAME
.Nm auth_approval ,
.Nm auth_cat ,
.Nm auth_checknologin ,
.Nm auth_mkvalue ,
.Nm auth_userchallenge ,
.Nm auth_usercheck ,
.Nm auth_userokay ,
.Nm auth_userresponse ,
.Nm auth_verify
.Nd simplified interface to the BSD Authentication system
.Sh SYNOPSIS
.Fd #include <login_cap.h>
.Fd #include <bsd_auth.h>
.Ft int
.Fn auth_userokay "char *name" "char *style" "char *type" "char *password"
.Ft auth_session_t *
.Fn auth_userchallenge "char *name" "char *style" "char *type" "char **challengep"
.Ft auth_session_t *
.Fn auth_usercheck "char *name" "char *style" "char *type" "char *password"
.Ft int
.Fn auth_userresponse "auth_session_t *as" "char *response" "int more"
.Ft int
.Fn auth_approval "auth_session_t *as" "struct login_cap *lc" "char *name" "char *type"
.Ft int
.Fn auth_cat "char *file"
.Ft void
.Fn auth_checknologin "struct login_cap *lc"
.Ft char *
.Fn auth_mkvalue "char *value"
.Ft auth_session_t *
.Fn auth_verify "auth_session_t *as" "char *style" "char *name" "..."
.Sh DESCRIPTION
These functions provide a simplified interface to the BSD Authentication
system
.Pq see Xr bsd_auth 3 .
The
.Fn auth_userokay
function provides a single function call interface.
Provided with a user's name in
.Ar name ,
and an optional
.Ar style ,
.Ar type ,
and
.Ar password ,
the
.Fn auth_userokay
function returns a simple yes/no response.
A return value of 0 implies failure; a non-zero return value implies success.
If
.Ar style
is not
.Dv NULL ,
it specifies the desired style of authentication to be used.
If it is
.Dv NULL
then the default style for the user is used.
In this case,
.Ar name
may include the desired style by appending it to the user's name with a
single colon
.Pq Sq \:
as a separator.
If
.Ar type
is not
.Dv NULL
then it is used as the authentication type (such as
.Dq auth-myservice ) .
If
.Ar password
is
.Dv NULL
then
.Fn auth_userokay
operates in an interactive mode with the user on standard input, output,
and error.
If
.Ar password
is specified,
.Fn auth_userokay
operates in a non-interactive mode and only tests the specified passwords.
This non-interactive method does not work with challenge-response
authentication styles.
For security reasons, when a
.Ar password
is specified,
.Fn auth_userokay
will zero out its value before it returns.
.Pp
The
.Fn auth_usercheck
function operates the same as the
.Fn auth_userokay
function except that it does not close the BSD Authentication session created.
Rather than returning the status of the session, it returns
a pointer to the newly created BSD Authentication session.
.Pp
The
.Fn auth_userchallenge
function takes the same
.Ar name , style ,
and
.Ar type
arguments as does
.Fn auth_userokay .
However, rather than authenticating the user, it returns a possible
challenge in the pointer pointed to by
.Ar challengep .
The return value of the function is a pointer to a newly created
BSD Authentication session.
This challenge, if not
.Dv NULL ,
should be displayed to the user.
In any case, the user should provide a password which is
the
.Ar response
in a call to
.Fn auth_userresponse .
In addition to the password, the pointer returned by
.Fn auth_userchallenge
should be passed in as
.Ar as
and the value of
.Va more
should be non-zero if the program wishes to allow more attempts.
If
.Va more
is zero then the session will be closed.
The
.Fn auth_userresponse
function closes the BSD Authentication session and has the same
return value as
.Fn auth_userokay .
For security reasons, when a
.Ar response
is specified,
.Fn auth_userresponse
will zero out its value before it returns.
.Pp
The
.Fn auth_approval
function calls the approval script for the user of the specified
.Ar type .
The string
.Dq approve-
will be prepended to
.Ar type
if missing.
The resulting type is used to look up an entry in
.Pa /etc/login.conf
for the user's class.
If the entry is missing, the generic entry for
.Dq approve
will be used.
The
.Ar name
argument will be passed to the approval program as the name of the user.
The
.Ar lc
argument points to a login class structure.
If it is
.Dv NULL
then a login class structure will be looked up for the class of
user
.Ar name .
The
.Fn auth_approval
function returns a value of 0 on failure to approve the user.
.Pp
Prior to actually calling the approval script, the account's
expiration time, the associated nologin file, and existence
of the account's home directory
.Po
if
.Li requirehome
is set for this class
.Pc
are checked.
Failure on any of these points causes the
.Fn auth_approval
function to return a value of 0 and not actually call the approval script.
.Pp
The
.Fn auth_cat
function opens
.Ar file
for reading and copies its contents to standard output.
It returns 0 if it was unable to open
.Ar file
and 1 otherwise.
.Pp
The
.Fn auth_checknologin
function must be provided with a pointer to a login class.
If the class has a
.Dq nologin
entry defined and it points to a file that can be opened,
the contents of the file will be copied to standard output and
.Xr exit 3
will be called with a value of 1.
If the class does not have the field
.Dq ignorenologin
and the file
.Pa /etc/nologin
exists its contents will be copied to standard output and
.Xr exit 3
will be called with a value of 1.
.Pp
The
.Fn auth_verify
function is a front end to the
.Xr auth_call 3
function.
It will open a BSD Authentication session, if needed, and will set
the style and user name based on the
.Ar style
and
.Ar name
arguments, if not
.Dv NULL .
Values for the style and user name in an existing BSD Authentication
session will be replaced and the old values freed (if the calling program
has obtained pointers to the style or user name via
.Xr auth_getitem 3 ,
those pointers will become invalid).
The variable arguments are passed to
.Fn auth_call
via the
.Xr auth_set_va_list 3
function.
The, possibly created, BSD Authentication session is returned.
The
.Xr auth_getstate 3
or
.Xr auth_close 3
function
should be used to determine the outcome of the authentication request.
.Pp
The
.Fn auth_mkvalue
function takes a NUL-terminated string pointed to by
.Ar value
and returns a NUL-terminated string suitable for passing
back to a calling program on the back channel.
This function is for use by the login scripts themselves.
The string returned should be freed by
.Xr free 3
when it is no longer needed.
A value of
.Dv NULL
is returned if no memory was available for the new copy of the string.
.Sh SEE ALSO
.Xr auth_subr 3 ,
.Xr getpwent 3 ,
.Xr pw_dup 3
.Sh CAVEATS
The
.Fn auth_approval ,
.Fn auth_usercheck ,
.Fn auth_userokay ,
and
.Fn auth_userchallenge
functions call
.Xr getpwnam 3
or
.Xr getpwuid 3 ,
overwriting the static storage used by the
.Xr getpwent 3
family of routines.
The calling program must either make a local copy of the passwd struct
pointer via the
.Xr pw_dup 3
function or, for
.Fn auth_approval
and
.Fn auth_usercheck
only, use the
.Xr auth_setpwd 3
function to copy the passwd struct into a BSD Authentication session structure
which can then be passed to
.Fn auth_approval
or
.Fn auth_usercheck .