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BSD_AUTH(3)               OpenBSD Programmer's Manual              BSD_AUTH(3)

     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_getpwd, auth_getstate, auth_getvalue,
     auth_set_va_list, auth_setdata, auth_setenv, auth_setitem,
     auth_setoption, auth_setpwd, auth_setstate - interface to the BSD Authen-
     tication system

     #include <login_cap.h>
     #include <bsd_auth.h>

     auth_session_t *

     auth_close(auth_session_t *as);

     auth_call(auth_session_t *as, char *path, ...);

     char *
     auth_challenge(auth_session_t *as);

     auth_check_change(auth_session_t *as);

     auth_check_expire(auth_session_t *as);

     auth_clean(auth_session_t *as);

     auth_clrenv(auth_session_t *as);

     auth_clroption(auth_session_t * as, char *name);

     auth_clroptions(auth_session_t *as);

     char *
     auth_getitem(auth_session_t *as, auth_item_t item);

     struct passwd *
     auth_getpwd(auth_session_t *as);

     auth_getstate(auth_session_t *as);

     char *
     auth_getvalue(auth_session_t *as, char *what);

     auth_set_va_list(auth_session_t *as, va_list ap);

     auth_setdata(auth_session_t *as, void *ptr, size_t len);

     auth_setenv(auth_session_t *as);

     auth_setitem(auth_session_t *as, auth_item_t item, char *value);

     auth_setoption(auth_session_t *as, char *name, char *value);

     auth_setpwd(auth_session_t *as, struct passwd *pwd);

     auth_setstate(auth_session_t *as, int state);

     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.  It is not necessary to call auth_clean()
     if auth_close() is called.

     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)


     ...     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 preceding -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

     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 (

     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

     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.

                      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-

     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_getpwd() retrieves the saved password file entry for
     the authentication session.  If no entry has been saved (either explicit-
     ly via auth_setpwd() or implicitly via auth_check_expire() or
     auth_check_change()) it returns NULL. Note that the memory containing the
     password file entry is freed by a call to auth_close() or auth_clean().

     The function auth_setstate() sets the sessions state to state. Typically
     this is either AUTH_OKAY or 0.

     The auth_check_change() and auth_check_expire() functions call getpwnam()
     or getpwuid(), overwriting the static storage used by the getpwent(3)
     family of routines.  The calling program must either make a local copy of
     the passwd struct pointer via the pw_dup(3) function or use the auth_set-
     pwd(3) function to copy the passwd struct into as.

     authenticate(3), login_cap(3), pw_dup(3), login.conf(5)

OpenBSD 3.1                     March 20, 1997                               5


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