sia_become_user(3) Library Functions Manual sia_become_user(3)
NAME
sia_become_user - su routine for SIA (Security Integration Architecture)
LIBRARY
Standard C library (libc.so and libc.a)
SYNOPSIS
#include <sia.h>
#include <siad.h>
int sia_become_user( sia_collect_func_t *collect, int argc, char **argv, char *hostname, char *username, char *tty, int colinput, char
*gssapi, char **envp, int style_flags)
PARAMETERS
The collect parameter is a pointer to an SIA collection routine. If this pointer is NULL, no collection is possible. If the pointer is
not NULL and the can_collect_input parameter entered during the sia_ses_init() call was zero, then this collection routine cannot be used
to prompt for input but can be used to display warnings or error messages. This parameter is read only. The argc and argv parameters are
used by the underlying security mechanisms for things like generating audit records and initializing database accesses. There should
always be at least one argument argv[0] which contains the name of the command or utility issuing a session initialization. These parame-
ters are read only. The hostname parameter is used to determine if the session is being requested by a remote system. If the request is
from a remote system, the hostname parameter points to a string containing the remote host information. If information about the request-
ing remote user is available, the information is in the form "node::user" for DECnet or "user@host" for IP. If the remote user information
is not available, the information is the remote "host". For local requests, this parameter is passed as a NULL pointer. The username
parameter is be set to point to the name or string representing the requesting user if this information is available. Otherwise this
parameter is set to NULL. This parameter is read only. The tty parameter is set to point to the name or string representing the request-
ing or active tty or X display if this information is available. Otherwise this parameter is set to NULL. This parameter is read only.
The colinput parameter specifies whether the collection of input is allowed during this session. A "1" means yes and "0" means no. This
parameter is read only. The gssapi pointer is for future expansion to utilize gss_api datatypes. It is not currently used and should be
set to NULL. This parameter is currently read only. The envp parameter specifies the environment array to add to the environment estab-
lished for the environment. Refer to exec(2) for a description of environment arrays. style_flags are specified as one or more of the fol-
lowing, or'ed together. Establish only a minimal environment for the user context. chdir() to user's home dir. chdir() to "/" is the
user's home directory is not available. This flag is ignored unless SIA_BEU_DOCHDIR or SIA_BEU_REALLOGIN is also set. This is a full
login, in the style of rlogind or rshd, rather than a 'su -user' equivalent.This flag implies SIA_BEU_DOCHDIR and SIA_BEU_SETLUID. Set or
change the audit ID of the process and call setlogin().
DESCRIPTION
This routine allows a privileged process to establish the full set of credentials for a specified user, for whichever system security mech-
anisms are in use. This is specifically intended for daemons like sendmail and cron which frequently have to perform unknown operations on
behalf of a given user.
The order of operations for this routine are as follows: (Note that in all cases, operations that fail cause succeeding steps to be skipped
and the function returns SIAFAIL.)
sia_ses_init() is called to initialize the SIA session. The argc through gssapi arguments are used.
getpwnam_r() is called for the specified username.
sia_make_entity_pwd() is called to complete filling out the SIA entity structure.
If _REALLOGIN is set, the entity's authtype field is set to SIA_A_NONE and sia_ses_estab() is called. If _REALLOGIN is not set, the
entity's authtype field is set to SIA_A_SUATH.
If _CLEARENV is set, the pointer to the old_environ is saved and a new (empty) one is created. (From this point on, failures will
attempt to restore the previous environment.)
If _CLEARENV is set, the old TERM environment variable will be propagated to the new environment (as is also done by login(1)) and a
PATH environment variable is set to the value "/usr/bin:".
The LOGNAME, USER, SHELL, and HOME environment variables are set from the user's profile. (Caution: If _CLEARENV was not specified,
these changes will still be in effect after a failure return)
If the 'envp' variable is non-NULL, each entry in that list is added to the environment with putenv(). (Caution: If _CLEARENV was
not specified, these changes will still be in effect after a failure return.)
The process priority is reset to the system default with setpriority(PRIO_PROCESS, 0, 0).
If _SETLUID was set and _REALLOGIN was not, the process audit ID is changed and setlogin() is called. If _REALLOGIN was set, these
steps are performed by sia_ses_estab() and sia_ses_launch().
sia_ses_launch() is called to perform the final processing of the session. This step will also call initgroups() if it is success-
ful, or in some cases if it is not successful. This change in the supplementary groups of the process is not restored on subsequent
failure.
If _DOCHDIR was set and _REALLOGIN was not, an attempt is made to chdir to the user's home directory. If that fails and _OKROOTDIR
was not set, or if the chdir("/") fails, SIAFAIL is returned.
If _REALLOGIN was set and _OKROOTDIR was not, and if the user's home directory was not "/", a check is made to see whether
sia_ses_launch() did a chdir("/") because the user's home directory was not available. If that is the case, SIAFAIL is returned.
sia_session_release() is called.
RETURN VALUES
The sia_become_user() routine returns either SIASUCCESS or SIAFAIL.
ERRORS
The errno value is not (normally) set explicitly by sia_* routines. The errno values are those returned from the dynamic loader interface,
from dependent (siad_*) routines, or from malloc. Possible errors include resource constraints (no memory) and various authentication
failures.
FILES
/etc/sia/matrix.conf
RELATED INFORMATION
sia_ses_init(3), siad_ses_init(3), siad_init(3), matrix.conf(4)
Security delim off
sia_become_user(3)