BSD_AUTH(3) BSD Programmer's Manual BSD_AUTH(3)NAME
auth_open, auth_call, auth_challenge, auth_check_change,
auth_check_expire, auth_clean, auth_close, auth_clrenv, auth_clroption,
auth_clroptions, auth_getitem auth_getstate, auth_getvalue,
auth_set_va_list, auth_setdata, auth_setenv, auth_setitem auth_setoption,
auth_setpwd, auth_setstate - interface to the BSD Authentication system
SYNOPSIS
#include <login_cap.h>
#include <bsd_auth.h>
auth_session_t *
auth_open();
int
auth_close(auth_session_t *as);
int
auth_call(auth_session_t *as, char *path, ...);
char *
auth_challenge(auth_session_t *as);
quad_t
auth_check_change(auth_session_t *as);
quad_t
auth_check_expire(auth_session_t *as);
void
auth_clean(auth_session_t *as);
void
auth_clrenv(auth_session_t *as);
void
auth_clroption(auth_session_t * as, char *name);
void
auth_clroptions(auth_session_t *as);
char *
auth_getitem(auth_session_t *as, auth_item_t item);
int
auth_getstate(auth_session_t *as);
char *
auth_getvalue(auth_session_t *as, char *what);
void
auth_set_va_list(auth_session_t *as, va_list ap);
int
auth_setdata(auth_session_t *as, void *ptr, size_t len);
void
auth_setenv(auth_session_t *as);
int
auth_setitem(auth_session_t *as, auth_item_t item, char *value);
int
auth_setoption(auth_session_t *as, char *name, char *value);
int
auth_setpwd(auth_session_t *as, struct passwd *pwd);
int
auth_setstate(auth_session_t *as, int state);
DESCRIPTION
These functions provide the lower level interface to the BSD Authentica-
tion system. They all operate on a BSD Authentication session pointer,
as, which is returned by auth_open(). The session pointer must be passed
to all other BSD Authentication functions called. The auth_open() func-
tion returns NULL if it was unable to allocate memory for the session.
The session is terminated by the auth_close() function, which also sets
any environment variables requested by the login script (assuming the us-
er was not rejected) or removes files created by the login script if the
authentication was not successful. It returns the final state of the au-
thentication request. A return value of 0 implies the user was not au-
thenticated. A non-zero return value is made up the 1 or more of the
following values ORed together:
AUTH_OKAY The user was authenticated.
AUTH_ROOTOKAY The user was authenticated with a root instance.
AUTH_SECURE The user was authenticated via a mechanism which is not
subject to eavesdropping attacks (such as provided by
token cards).
The full state of the session is returned by the auth_getstate() func-
tion. In addition to the values above, it also may contain the bits:
AUTH_SILENT Do not report an error, the user was not authenticated
for access and was not expected to be. This is returned
by login scripts that allow changing of the users pass-
word, for instance. This value is stripped off for nor-
mal returns.
AUTH_CHALLENGE The user was not authenticated for access and a chal-
lenge was issued. The challenge should be displayed to
the user, a response retrieved, and the result verified.
This value is stripped off for normal returns.
AUTH_EXPIRED The user's account has expired.
AUTH_PWEXPIRED The user's password has expired and needs to be changed.
A session may be cleaned by calling auth_clean(). This function causes
any files created by a login script in this session and clears all state
associated with this session.
The remaining functions are described in alphabetical order.
The fundamental function for doing BSD Authentication is auth_call(). In
addition to the pointer to the BSD Authentication session, it takes the
following parameters:
path The full path name of the login script to run. The call will
fail if path does not pass the requirements of the secure_path(3)
function.
... The remaining arguments, which should be of type char * and ter-
minated with a NULL are passed to the login script at the end of
the command line.
The auth_call() function, after verifying the path, creates a bi-direc-
tional pipe (socketpair) which is located on file descriptor 3 for the
child (the login script). This is known as the ``back channel''. The ac-
tual command line passed to the child is made up of 3 parts. The parame-
ters passed to auth_call() following path have appended to them any argu-
ments specified by the auth_set_va_list() function. These are typically
the variable arguments passed to the function that calls auth_call().
Any option values set by the auth_setoption() function are inserted be-
tween the first argument (the command name) and the second argument with
a preceeding -v flag. The name and value are separated by an `=':
-v name=value
Once the login script has been spawned, any data specified by the
auth_setdata() is written to the back channel. Multiple blocks of data
may have been specified and they will be sent in the same order they were
specified. As the data is sent, the storage for the data is zeroed out
and then freed (the data is zeroed out since it may contain sensitive in-
formation, such as a password). Once any data is written out,
auth_call() reads up to 8192 bytes of data from the back channel. The
state of the session is determined from this data (see login.conf(5) for
details). If the login script exits with a 0 and does not specify any
return state on the back channel, the state prior to the call to
auth_call() is retained.
The data read from the back channel is also used by the auth_getvalue()
and auth_close() functions. Subsequent calls to auth_call() will cause
this data to be lost and overwritten with the new data read from the new
call.
The environment passed to the login script by auth_call() only contains
two values: PATH and SHELL. The PATH is set to the default path ( /bin
and /usr/bin) while the SHELL is set to the default system shell (
/bin/sh).
The auth_challenge() function queries the login script defined by the
current style for a challenge for the user specified by name. (See below
for the setting of the style and name). It internally uses the
auth_call() function. The generated challenge is returned. NULL is re-
turned on error or if no challenge was generated. The challenge can also
be extracted by the auth_getchallenge() function, which simply returns
the last challenge generated for this session.
The auth_check_change() and auth_check_expire() functions check the pass-
word expiration (change) and account expiration times. They return 0 if
no change or expiration time is set for the account. They return a nega-
tive value of how many seconds have passed since the password or account
expired. In this case the state of the session is marked with either
AUTH_PWEXPIRED or AUTH_EXPIRED as well as clearing any bits which would
indicate the authentication was successful. If the password or account
has not expired they return the number of seconds left until the account
does expire. The return value of -1 can either indicate the password or
account just expired or that no password entry was set for the current
session.
The auth_clrenv() function clears any requests set by a login script for
environment variables to be set.
The auth_clroption() function clears the previously set option name.
The auth_clroptions() function clears all previously set options.
The auth_getitem() function returns the value of of item. The item may be
one of:
AUTH_CHALLENGE The latest challenge, if any, set for the session.
AUTH_CLASS The class of the user, as defined by the /etc/login.conf
file. This value is not directly used by BSD Authenti-
cation, rather, it is passed to the login scripts for
their possible use.
AUTH_INTERACTIVE
If set to any value then the session is tagged as inter-
active. If not set the session is not interactive.
When the value is requested it is always either NULL or
``True''. The auth subroutines may choose to provide ad-
ditional information to standard output or standard er-
ror when the session is interactive. There is no func-
tional change in the operation of the subroutines.
AUTH_NAME The name of the user being authenticated. The name
should include the instance, if any, that is being re-
quested.
AUTH_SERVICE The service requesting the authentication. Initially it
is set to the default service which provides the tradi-
tional interactive service.
AUTH_STYLE The style of authentication being performed, as defined
by the /etc/login.conf file. The style determines which
login script should actually be used.
The auth_getvalue() function returns the value, if any, associated with
the specified internal variable what. These variables are set by login
scripts. When a new login script is run (by the auth_call(function)) the
values from the previous login script are lost. (See login.conf(5) for
details on internal variables.)
The auth_set_va_list() function establishes a variable argument list to
be used by the auth_call() function. It is intended to be used by func-
tions which need to call auth_call() but take a variable number of argu-
ments themselves. Since the arguments are not copied, the call to
auth_call() must be placed within the scope of ap. The auth_call() func-
tion will call va_end(3) on ap.
The auth_setdata() function makes a copy of len bytes of data pointed to
by ptr for use by auth_call(). The data will be passed on the back chan-
nel to the next login script called.
The auth_setenv() function adds/deletes any environment variables re-
quested by the login script to the current environment.
The auth_setitem() function assigns value to the specified item. The
items are described above with the auth_getitem() function. In addition,
if item is AUTH_ALL and value is NULL then all items are cleared.
The auth_setoption() function requests that the option name be set with
the value of value when a script is executed by auth_call(). The actual
arguments to the script will be placed at the beginning of the argument
vector. For each option two arguments will be issued: -v name=value.
The function auth_setpwd() establishes the password file entry for the
authentication session. If the name has already been set by
auth_setitem() then the pwd argument may be NULL, else it must be the
password entry to use.
The function auth_setstate() sets the sessions state to state. Typically
this is either AUTH_OKAY or 0.
SEE ALSOauthenticate(3), auth_compat(3), login_cap(3), login.conf(5)BSDI BSD/OS March 20, 1997 5
