437 lines
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15 KiB
XML
437 lines
No EOL
15 KiB
XML
<refentry xmlns="http://docbook.org/ns/docbook" version="5.0" xml:id="pam3">
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<refmeta>
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<refentrytitle>pam</refentrytitle>
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<manvolnum>3</manvolnum>
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<refmiscinfo class="source">Linux-PAM</refmiscinfo>
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<refmiscinfo class="manual">Linux-PAM Manual</refmiscinfo>
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</refmeta>
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<refnamediv xml:id="pam3-name">
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<refname>pam</refname>
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<refpurpose>Pluggable Authentication Modules Library</refpurpose>
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</refnamediv>
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<refsynopsisdiv xml:id="pam3-synopsis">
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<funcsynopsis>
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<funcsynopsisinfo>#include <security/pam_appl.h></funcsynopsisinfo>
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<funcsynopsisinfo>#include <security/pam_modules.h></funcsynopsisinfo>
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<funcsynopsisinfo>#include <security/pam_ext.h></funcsynopsisinfo>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1 xml:id="pam3-description">
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<title>DESCRIPTION</title>
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<para>
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<emphasis remap="B">PAM</emphasis> is a system of libraries
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that handle the authentication tasks of applications (services)
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on the system. The library provides a stable general interface
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(Application Programming Interface - API) that privilege granting
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programs (such as
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<citerefentry>
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<refentrytitle>login</refentrytitle><manvolnum>1</manvolnum>
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</citerefentry> and <citerefentry>
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<refentrytitle>su</refentrytitle><manvolnum>1</manvolnum>
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</citerefentry>)
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defer to to perform standard authentication tasks.
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</para>
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<refsect2 xml:id="pam3-initialization_and_cleanup">
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<title>Initialization and Cleanup</title>
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<para>
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The
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<citerefentry>
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<refentrytitle>pam_start</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry> function creates the PAM context and initiates the
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PAM transaction. It is the first of the PAM functions that needs to
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be called by an application. The transaction state is contained
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entirely within the structure identified by this handle, so it is
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possible to have multiple transactions in parallel. But it is not
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possible to use the same handle for different transactions, a new
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one is needed for every new context.
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</para>
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<para>
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The
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<citerefentry>
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<refentrytitle>pam_end</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry> function terminates the PAM transaction and is the last
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function an application should call in the PAM context. Upon return
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the handle pamh is no longer valid and all memory associated with it
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will be invalid. It can be called at any time to terminate a PAM
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transaction.
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</para>
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</refsect2>
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<refsect2 xml:id="pam3-authentication">
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<title>Authentication</title>
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<para>
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The
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<citerefentry>
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<refentrytitle>pam_authenticate</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>
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function is used to
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authenticate the user. The user is required to provide an
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authentication token depending upon the authentication service,
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usually this is a password, but could also be a finger print.
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</para>
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<para>
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The
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<citerefentry>
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<refentrytitle>pam_setcred</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>
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function manages the user's credentials.
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</para>
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</refsect2>
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<refsect2 xml:id="pam3-account_management">
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<title>Account Management</title>
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<para>
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The
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<citerefentry>
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<refentrytitle>pam_acct_mgmt</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry> function is used to determine if the user's account is
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valid. It checks for authentication token and account expiration and
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verifies access restrictions. It is typically called after the user
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has been authenticated.
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</para>
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</refsect2>
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<refsect2 xml:id="pam3-password_management">
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<title>Password Management</title>
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<para>
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The
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<citerefentry>
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<refentrytitle>pam_chauthtok</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry> function is used to change the authentication token
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for a given user on request or because the token has expired.
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</para>
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</refsect2>
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<refsect2 xml:id="pam3-session_management">
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<title>Session Management</title>
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<para>
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The
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<citerefentry>
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<refentrytitle>pam_open_session</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry> function sets up a user session for a previously
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successful authenticated user. The session should later be terminated
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with a call to
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<citerefentry>
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<refentrytitle>pam_close_session</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>.
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</para>
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</refsect2>
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<refsect2 xml:id="pam3-conversation">
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<title>Conversation</title>
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<para>
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The PAM library uses an application-defined callback to allow
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a direct communication between a loaded module and the application.
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This callback is specified by the
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<emphasis>struct pam_conv</emphasis> passed to
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<citerefentry>
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<refentrytitle>pam_start</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry> at the start of the transaction. See
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<citerefentry>
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<refentrytitle>pam_conv</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>
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for details.
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</para>
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</refsect2>
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<refsect2 xml:id="pam3-data">
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<title>Data Objects</title>
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<para>
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The
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<citerefentry>
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<refentrytitle>pam_set_item</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>
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and
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<citerefentry>
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<refentrytitle>pam_get_item</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>
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functions allow applications and PAM service modules to set and
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retrieve PAM information.
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</para>
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<para>
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The
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<citerefentry>
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<refentrytitle>pam_get_user</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>
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function is the preferred method to obtain the username.
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</para>
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<para>
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The
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<citerefentry>
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<refentrytitle>pam_set_data</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>
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and
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<citerefentry>
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<refentrytitle>pam_get_data</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>
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function allows PAM service modules to set and retrieve free-form
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data from one invocation to another.
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</para>
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</refsect2>
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<refsect2 xml:id="pam3-miscellaneous">
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<title>Environment and Error Management</title>
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<para>
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The
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<citerefentry>
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<refentrytitle>pam_putenv</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>,
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<citerefentry>
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<refentrytitle>pam_getenv</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry> and
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<citerefentry>
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<refentrytitle>pam_getenvlist</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>
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functions are for maintaining a set of private environment variables.
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</para>
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<para>
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The
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<citerefentry>
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<refentrytitle>pam_strerror</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry> function returns a pointer to a string describing the
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given PAM error code.
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</para>
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</refsect2>
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</refsect1>
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<refsect1 xml:id="pam3-return_values">
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<title>RETURN VALUES</title>
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<para>
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The following return codes are known by PAM:
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</para>
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<variablelist>
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<varlistentry>
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<term>PAM_ABORT</term>
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<listitem>
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<para>Critical error, immediate abort.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>PAM_ACCT_EXPIRED</term>
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<listitem>
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<para>User account has expired.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>PAM_AUTHINFO_UNAVAIL</term>
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<listitem>
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<para>
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Authentication service cannot retrieve authentication info.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>PAM_AUTHTOK_DISABLE_AGING</term>
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<listitem>
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<para>Authentication token aging disabled.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>PAM_AUTHTOK_ERR</term>
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<listitem>
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<para>Authentication token manipulation error.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>PAM_AUTHTOK_EXPIRED</term>
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<listitem>
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<para>Authentication token expired.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>PAM_AUTHTOK_LOCK_BUSY</term>
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<listitem>
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<para>Authentication token lock busy.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>PAM_AUTHTOK_RECOVERY_ERR</term>
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<listitem>
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<para>Authentication information cannot be recovered.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>PAM_AUTH_ERR</term>
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<listitem>
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<para>Authentication failure.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>PAM_BUF_ERR</term>
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<listitem>
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<para>Memory buffer error.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>PAM_CONV_ERR</term>
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<listitem>
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<para>Conversation failure.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>PAM_CRED_ERR</term>
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<listitem>
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<para>Failure setting user credentials.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>PAM_CRED_EXPIRED</term>
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<listitem>
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<para>User credentials expired.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>PAM_CRED_INSUFFICIENT</term>
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<listitem>
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<para>Insufficient credentials to access authentication data.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>PAM_CRED_UNAVAIL</term>
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<listitem>
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<para>Authentication service cannot retrieve user credentials.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>PAM_IGNORE</term>
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<listitem>
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<para>The return value should be ignored by PAM dispatch.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>PAM_MAXTRIES</term>
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<listitem>
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<para>Have exhausted maximum number of retries for service.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>PAM_MODULE_UNKNOWN</term>
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<listitem>
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<para>Module is unknown.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>PAM_NEW_AUTHTOK_REQD</term>
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<listitem>
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<para>
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Authentication token is no longer valid; new one required.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>PAM_NO_MODULE_DATA</term>
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<listitem>
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<para>No module specific data is present.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>PAM_OPEN_ERR</term>
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<listitem>
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<para>Failed to load module.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>PAM_PERM_DENIED</term>
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<listitem>
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<para>Permission denied.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>PAM_SERVICE_ERR</term>
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<listitem>
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<para>Error in service module.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>PAM_SESSION_ERR</term>
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<listitem>
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<para>Cannot make/remove an entry for the specified session.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>PAM_SUCCESS</term>
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<listitem>
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<para>Success.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>PAM_SYMBOL_ERR</term>
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<listitem>
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<para>Symbol not found.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>PAM_SYSTEM_ERR</term>
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<listitem>
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<para>System error.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>PAM_TRY_AGAIN</term>
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<listitem>
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<para>Failed preliminary check by password service.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>PAM_USER_UNKNOWN</term>
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<listitem>
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<para>User not known to the underlying authentication module.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1 xml:id="see_also"><title>SEE ALSO</title>
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<para>
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<citerefentry>
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<refentrytitle>pam_acct_mgmt</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>, <citerefentry>
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<refentrytitle>pam_authenticate</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>, <citerefentry>
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<refentrytitle>pam_chauthtok</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>, <citerefentry>
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<refentrytitle>pam_close_session</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>, <citerefentry>
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<refentrytitle>pam_conv</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>, <citerefentry>
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<refentrytitle>pam_end</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>, <citerefentry>
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<refentrytitle>pam_get_data</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>, <citerefentry>
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<refentrytitle>pam_getenv</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>, <citerefentry>
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<refentrytitle>pam_getenvlist</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>, <citerefentry>
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<refentrytitle>pam_get_item</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>, <citerefentry>
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<refentrytitle>pam_get_user</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>, <citerefentry>
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<refentrytitle>pam_open_session</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>, <citerefentry>
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<refentrytitle>pam_putenv</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>, <citerefentry>
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<refentrytitle>pam_set_data</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>, <citerefentry>
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<refentrytitle>pam_set_item</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>, <citerefentry>
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<refentrytitle>pam_setcred</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>, <citerefentry>
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<refentrytitle>pam_start</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>, <citerefentry>
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<refentrytitle>pam_strerror</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>
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</para>
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</refsect1>
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<refsect1 xml:id="pam3-notes"><title>NOTES</title>
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<para>
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The <emphasis>libpam</emphasis> interfaces are only thread-safe if each
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thread within the multithreaded application uses its own PAM handle.
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</para>
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</refsect1>
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</refentry> |