NAME
pam_authenticate — perform authentication within the PAM framework
SYNOPSIS
cc
[ flag ... ] file ...
-lpam
[ library ... ]
#include <security/pam_appl.h>
int pam_authenticate(pam_handle_t *pamh,
int flags);
DESCRIPTION
pam_authenticate()
is called to authenticate the current user.
The user is usually required to enter a password or similar authentication token depending upon
the authentication service configured within the system. In the case
of smart card authentication this token would be a
PIN
(Personal Identification
Number).
The user in question should have been specified by a prior call to
pam_start()
or
pam_set_item().
The following flags may be set in the
flags
field:
- PAM_SILENT
Authentication service should not generate any messages
- PAM_DISALLOW_NULL_AUTHTOK
The authentication service should return
PAM_AUTH_ERROR
if the user has a null authentication token
APPLICATION USAGE
Refer to
pam(3)
for information on thread-safety of PAM interfaces.
NOTES
In the case of authentication failures due to an incorrect username
or password, it is the responsibility of the application to retry
pam_authenticate()
and to maintain the retry count.
An authentication service module may implement an
internal retry count and return an error
PAM_MAXTRIES
if the module does not want the application to retry.
If the PAM framework can not load the authentication module, then
it will return
PAM_ABORT.
This indicates a serious failure and that
the application should not attempt to retry the authentication.
For security reasons,
the location of authentication failures is hidden from the user.
Thus, if several authentication services are stacked and a single
service fails,
pam_authenticate()
requires that the user re-authenticate to all the services.
A null authentication token in the authentication database will
result in successful authentication unless
PAM_DISALLOW_NULL_AUTHTOK
was specified.
In such cases, there will not be any prompting
for the user to enter an authentication token.
The authentication can be done through a smart card. In this case the
user plugs their smart card in the smart card reader and is required to
enter their smart card PIN.
RETURN VALUES
Upon successful completion,
PAM_SUCCESS
is returned.
In addition to the error return values described in
pam(3),
the following values may be returned:
- PAM_AUTH_ERR
Authentication failure.
- PAM_CRED_INSUFFICIENT
Can not access authentication data due to insufficient credentials.
- PAM_AUTHINFO_UNAVAIL
Underlying authentication service can not retrieve authentication information.
- PAM_USER_UNKNOWN
User not known to the underlying authentication module.
- PAM_MAXTRIES
An authentication service has maintained a retry count which
has been reached. No further retries should be attempted.
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